WO2025199649A1 - Broadband microspectroscopic dynamic testing system - Google Patents

Abstract

Disclosed embodiments relate to optical characterization apparatuses, focusing primarily on the meticulous examination of nanostructured and unstructured thin films across varied wavelengths. Embodiments amalgamate advanced technologies to facilitate precise, versatile, and reliable analytical outcomes, crucial for the exploration of materials science and optical engineering.

Description

BROADBAND MICROSPECTROSCOPIC DYNAMIC TESTING SYSTEM

CROSS-REFERENCE TO RELATED APPLICATION(S)

[0001] The present application claims priority to, and the benefit of, United States Provisional Patent Application No. 63/570,377 titled “Broadband Microspectroscopic Dynamic Tester”, filed on March 27, 2024, the entire contents which are incorporated herein by reference.

FIELD

[0002] The present invention generally relates to measurement and analysis of light-matter interactions, and more particularly, to a broadband microspectroscopic dynamic testing system.

BACKGROUND

[0003] When developing a successful device, beyond fabrication, establishing reliable methods to accurately measure and characterize its optical response is crucial — this response should be in close alignment with the simulated one. Therefore, device characterization methodologies are fundamental in the realms of experimental physics and engineering.

[0004] Typically, characterizing thin films involves sequential ellipsometry and profilometric measurements to ascertain optical constants and thicknesses. Ellipsometry gauges light polarization alterations to deduce properties such as film thickness and optical constants.

[0005] To this end, traditional techniques for film characterization, including ellipsometry, often require large spot sizes between 2-10 mm for trustworthy measurements, leading to elevated fabrication expenses. Additionally, mainstream ellipsometry instruments are specialized for a singular type of measurement, limiting modifications to the setup. Consequently, producing a custom optical system that simulates the requisite conditions for device measurements is pivotal.

[0006] Post-measurement, a sample-specific model is often constructed, serving as a basis for calculating predicted responses through Fresnel’s equations, which detail each property. Initial property estimates are compared with experimental data, refining unknown properties for improved alignment between experimental and theoretical calculations, usually achieved through regression and minimizing Mean Squared Error (MSE). However, pitfalls - including “local” minimums - can misdirect regression algorithms, emphasizing the necessity for reliable data-fitting validation methods, such as comparing experimental setups measuring reflection and transmission at normal incidence with simulated FDTD responses.

[0007] Beyond standard film and device level characterizations, a setup adept at determining the switching speeds and endurance of optoelectronically reconfigurable alloys is essential given the growing prominence of these alloys in reconfigurable nanophotonics and quantum and neuromorphic computing. A standard optical measurement setup capable of accurately gauging various switching speeds and powers required to invoke these light-induced phenomena is invaluable. This would not only facilitate studies into switching dynamics but also aid the development of a fully reversible switching framework.

[0008] Furthermore, employing these switching parameters could lead to the development of an automated system, capable of conducting thousands of switching cycles on PCM alloy thin films, thereby providing insight into the endurance limits of these alloys. Such a system would be a significant asset to researchers, outlining the constraints of these chalcogenide alloys films. The profound understanding acquired through such precise, versatile, and reliable characterization techniques not only propels advancements in device fabrication and material sciences but also spurs innovations, addressing the complexities and unique attributes of emerging materials in nanophotonics.

SUMMARY

[0009] Disclosed examples generally relate to a broadband microspectroscopic dynamic testing system.

[0010] In some examples, the disclosed apparatus is adept at conducting proficient measurements of a broad band optical response, extending from nanostructured to unstructured thin films across the visible to NIR wavelengths (400nm<l<1700nm) at near-normal incidences. It is calibrated to secure accurate spectral data from metasurfaces, either plasmonic or dielectric, formed on varying substrates.

[0011] The disclosed system is particularly significant due to its capability, in at least some examples, to effectively measure small footprint patterns of less than approximately 30 pm owing to its high magnification of 150X and minimized angle of incidence less than approximately 15° -75°, pivotal for structures synthesized through high-resolution techniques like Electron Beam and Focused Ion Beam Lithography. The system integrates extensive measurement faculties, allowing assessments of reflection and transmission at diverse polarizations, catering to a wide spectrum of structured and unstructured films. The system can also give dark field imaging of any samples and allows the measurement of optical response from extremely obliquely incident angles.

[0012] In some examples, the described system delivers precise optical pulse energies, crucial for inducing reversible non-volatile transitions in diverse optoelectronically reconfigurable materials. It standardizes the assessment of optical switching energies amidst the rapid advancements in chalcogenide materials for high-grade applications, serving as an important determinant of precise energies and a meticulous informant on the switching endurance of various alloys, thereby illuminating the true performance and reliability of these innovative materials and their corresponding devices.

[0013] Furthermore, the disclosed system is optimized to function as a refined probe station, enabling random addressing of specific pixels to reprogram and analyze multifunctional metasurfacebased devices. It integrates an advanced FPGA-based probing mechanism, ensuring accurate programming and documentation of alterations in the optical spectrum, providing a comprehensive platform for synchronized probe positioning and operations.

[0014] In at least one example, the system is configured to facilitate transient volatile reflection change measurements in the nanosecond time domain, operating as a pump-probe setup to observe ultrafast response capabilities by optically stimulating a given thin film and analyzing subsequent reflection responses at telecom range wavelengths. [0015] In at least one broad aspect, there is provided a broadband dynamic testing system, comprising: a sample stage configured to hold a sample for testing; an inverted microscope optical assembly, comprising (i) a light source input port, (ii) a sample observation port, (iii) an imaging output port, and (iv) a binocular output port; one or more of a reflection source optical assembly, comprising a first broadband light source for measuring light reflection properties of the sample, wherein the reflection optical assembly comprises an output port coupled to the light source input port; a transmission source optical assembly, comprising a second broadband light source for measuring light transmission properties of the sample, wherein the transmission source optical assembly includes an output port aligned over an opposite side of the sample from the sample observation port; and an observation optical assembly, configured to magnify an image of a region of interest on the sample and enabling at least one of (i) measurement of the sample properties in the region of interest, and (ii) imaging of the region of interest.

[0016] In some examples, the sample is a nano- structured or unstructured thin film.

[0017] In some examples, the region of interest is a nanostructured region.

[0018] In some examples, one or more of the first and second broadband light sources comprise halogen lamps.

[0019] In some examples, one or more of the optical assemblies comprise an off-axis parabolic (OAP) mirror.

[0020] In some examples, the reflection source arm further comprises one or more lasers for pump-probe microscopy, wherein the one or more lasers transmit a laser signal along a first light path extending through an aperture formed in the OAP mirror, and the first light source transmits light along a second light path that reflects of a surface of the OAP mirror.

[0021] In some examples, the observation arm includes optical components configured to apply a magnification of 10X to an input optical image of the region of interest.

[0022] In some examples, the system includes a reflective objective lens having a 15X magnification, and the system outputs, from the observation arm, a 150X magnification of the region of interest on the sample.

[0023] In some examples, the angle of incidence of light on the sample is less than approximately 15°- 75°. [0024] In some examples, one or more of the reflection and transmission source arms include polarizing elements for measuring reflection and transmission properties, respectively, of the sample at various polarization angles.

[0025] In some examples, the transmission source arm further comprises a laser arm portion comprising a laser source.

[0026] In some examples, the transmission source arm include an OAP, and the laser signal follows a first optical path to the sample stage via a central aperture of the OAP, the light from the second light source follows a second optical path to the sample stage by reflecting of a surface of the OAP.

[0027] In some examples, the laser source is used for inducing a reversible transition in optoelectronically reconfigurable materials comprising the sample.

[0028] In some examples, the system further comprises an electro-optic probing system.

[0029] In some examples, the reflection source arm is configured with pump-probe measurement capabilities.

[0030] In some examples, the system further comprises a sample stage support system for the sample stage, the support system comprising an automated stage translation mechanism coupled to a motion control mechanism.

[0031] In some examples, the system further comprises a controller coupled to one or more of: a shutter control system, for controlling one or more ring actuated iris diaphragms that control light output from the broadband light sources; a variable focus control system, for controlling switching between a laser and visible focal spot; a laser pulse width control system, for varying a pulse width of a laser pulse from the laser; a laser power control system, for controlling a power of a laser signal from the laser; a camera control system, for programmatically taking reflection or transmission mode snapshots of the sample; a repetition rate control system for controlling a repetition rate of the pulsed laser; a spectrum control system measure the reflection and transmission spectrum; and a stage motion control system for controlling movement of a support stage.

[0032] In some examples, the system is used for generating a static matrix on the sample comprising one or more rastered portions, and testing the various rastered portions for reflection and/or transmission properties. [0033] In some examples, the system is further configured for endurance testing of samples.

[0034] In some examples, one or more of the optical assemblies is removably coupled to a housing of the inverted microscope optical assembly.

[0035] In some examples, the sample stage and the reflection and transmission arms are configured for Photonic Integrated Circuit (PIC) measurements, and the system further comprises a further assembly with position translation stages mounted on the sample stage to enable precise alignment of a multichannel fiber v-groove on top of a photonic chip.

[0036] In some examples, the sample stage is configured for the positioning of electrical probes, enabling optoelectronic measurements on the photonic chip.

[0037] In another broad aspect there is provided the sample stage, inverted microscope optical assembly, reflection source optical assembly, transmission source optical assembly and observation optical.

[0038] Other features and advantages of the present application will become apparent from the following detailed description taken together with the accompanying drawings. It should be understood, however, that the detailed description and the specific examples, while indicating preferred embodiments of the application, are given by way of illustration only, since various changes and modifications within the spirit and scope of the application will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0039] For a better understanding of the various embodiments described herein, and to show more clearly how these various embodiments may be carried into effect, reference will be made, by way of example, to the accompanying drawings which show at least one example embodiment, and which are now described. The drawings are not intended to limit the scope of the teachings described herein.

[0040] FIG. 1A illustrates an optical path in an inverted optical microscope with fully characterized optical path elements. [0041] FIG. IB shows a schematic diagram of a Kohler illumination optical assembly used to defocus a lamp and achieve a uniform illumination of a sample.

[0042] FIG. 2 shows a complete three-dimensional (3D) representation of a complete system as disclosed herein.

[0043] FIG. 3 A shows an example optical layout of a broadband microspectroscopic dynamic testing system.

[0044] FIG. 3B shows another example optical layout of a broadband microspectroscopic dynamic testing system.

[0045] FIG. 4A shows an example optical layout for a reflection source arm.

[0046] FIGs. 4B - 4D show various three-dimensional (3D) representations of the reflection source arm.

[0047] FIG. 5 shows an example optical layout for an observation arm.

[0048] FIG. 6 shows plots of (a) the refractive index of amorphous and crystalline GST (Germanium Antimony Telluride), (b) the measured vs. simulated reflection of a thin film of amorphous GST, (c) the extinction coefficient of amorphous and crystalline GST, and (d) the measured vs. simulated reflection of crystalline GST.

[0049] FIG. 7A shows an example optical layout for a transmission source arm.

[0050] FIG. 7B shows a three-dimensional (3D) representation of the transmission source arm.

[0051] FIG. 8 shows an example hardware configuration for a control system.

[0052] FIG. 9 shows the scanning electron microscope (SEM) and microscopic images of a nanograting structure patterned on gold.

[0053] FIG. 10 shows a comparison of the optical response of a nanograting structure between simulated, CRAIC and inhouse-built optical setup of the broadband micospectroscopic dynamic testing system. The SEM image of the nanograting structure is shown in FIG. 9. The nanograting was created using FIB (Focused Ion beam) using four (4) different dose setting, namely lOmC (a), 20mC (b), 30mC (c) and 40mC (d).

[0054] FIG. 11 shows both reflection and transmission measurements of a nanostructured sample at TE and TM polarizations, in particular showing (a) the SEM image of the nanograting patterned on SiN membrane. The alignment marks can be used as a guide to align the sample for TE and TM polarization measurements; (b)-(c) the microscope image under transmission and reflection illuminations; (d)-(e) the transmission and reflection measurement of the sample under TE and TM polarizations. The sample during each measurement was completely covering the circular aperture at the center of the circular viewport seen in the image in (b)-(c).

[0055] FIG. 12 shows a perspective three-dimensional (3D) view of a mechanical design of a dual-axis stage motion configuration.

[0056] FIG. 13 shows: (a)-(b) a three-dimensional (3D) view of an automatic stepper motor actuated iris shutter controller placed in front of the broadband light source for both transmission and reflection illumination arm; (c) a detailed view of the actuated iris shutter controllers, whereby the iris is also connected to a rotary encoder via a gear. The rotary encoder provides feedback control to the stepper to accurately control the rotation of the iris to open and close by desired amount; (d) an example where the controller is mounted on the transmission arm; (e) the stepper motor actuated power controller 3D design schematic where a stepper and rotary encoder is attached to an neutral density (ND) filter wheel placed in the path of the laser in the transmission arm of the broadband dynamic tester; and (f) the detailed view of the design. The central gear holds the continuously variable ND filter wheel.

[0057] FIG. 14 shows an example flowchart for executing a static testing. On the left a schematic view of the static test pattern as seen on the camera view of the optical setup. This view shows various exposure doses are applied on the sample as the pulse width is varied in the Y axis and the power is varied in the X axis.

[0058] FIG. 15 shows an example flowchart for executing an endurance measurement. [0059] FIG. 16 illustrates the static testing process conducted on as-deposited GST film to determine the pulse energy required for crystallization, showing: (a) the final microscope image in reflection mode of the static test matrix. Each cell in the matrix is exposed with a different pulse energy. The pulse width is increasing, and the peak power is decreasing in the direction of the arrow; (b) the final microscope image in transmission mode; (c)-(d) the reflection, transmission, and absorption spectra as a function of pulse energy used to expose each cell at l=1575nm; and (e)-(f) the reflection, transmission, and absorption spectra as a function of pulse energy used to expose each cell at A=850nm.

[0060] FIG. 17 illustrates the static testing process conducted on a crystalline film formed by laser-induced crystallization of a 6 mm x 6 mm area, using laser parameters established during the previous static test phase performed on as-deposited GST film, and showing (a) the final microscope image in reflection mode of the static test matrix. Each cell in the matrix is exposed with different pulse energy. The pulse width is increasing, and the peak power is decreasing in the direction of the arrow; (b) the final microscope image in transmission mode; (c)-(e) the reflection, transmission, and absorption spectra as a function of pulse energy used to expose each cell at l=475nm; and (f)-(h) the reflection, transmission, and absorption spectra as a function of pulse energy used to expose each cell at l=1025nm.

[0061] FIG. 18 shows a modified sample stage to add a removeable optical components for precise positioning of a fiber groove on a photonic chip, and showing (a) the modified broadband dynamic spectroscopic tester view; (b) a multi-axis micro positioner for a precise fiber v-groove aligner; (c) a detailed view of the L arm holding the servo and fiber v groove; (d) a closeup view of the fiber v groove sitting on the shaft connected to servo; and (e) a v groove on photonic integrated circuit and a photonic chip comprising of input and output grating couplers.

[0062] FIG. 19 shows schematics of the modified transmission arm of the broadband dynamic spectroscopic tester for alignment of the fiber v groove to the grating couplers on a photonic chip.

[0063] FIG. 20 shows two windows on a dual monitor setup, and showing (a) the signal analysis viewer allowing the user to probe the photonic chip and measure the response; and (b) various camera views for assisting in alignment and achieving highest coupling efficiency. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0064] Disclosed examples generally relate to a broadband microspectroscopic dynamic testing system.

I. DEFINITIONS

[0065] “Chalcogenide materials" refers to a class of chemical compounds comprising one or more chalcogen elements selected from sulfur (S), selenium (Se), or tellurium (Te) chemically bonded with one or more electropositive elements, such as metals or metalloids. These materials exhibit distinct physical and chemical properties, including variable electrical conductivity, high refractive indices, and phase-change behavior, depending on their composition and structure.

[0066] “Inverted optical microscope" is an optical imaging device configured such that the objective lenses are positioned below the specimen stage, allowing the sample to be observed from underneath. The optical path is arranged to direct illumination through the sample from above or below the stage, depending on the specific configuration.

[0067] "Memory" refers to a non-transitory tangible computer-readable medium for storing information in a format readable by a processor, and/or instructions readable by a processor to implement an algorithm. The term "memory" includes a plurality of physically discrete, operatively connected devices despite use of the term in the singular. Non-limiting types of memory include solid- state, optical, and magnetic computer readable media. Memory may be non-volatile or volatile. Instructions stored by a memory may be based on a plurality of programming languages known in the art, with non-limiting examples including the C, C++, Python ™, MATLAB ™, and Java ™ programming languages.

[0068] “Microspectroscopic" systems refers to systems that integrate microscopy and spectroscopy to enable spatially resolved spectroscopic analysis of a sample at microscopic scales. A microspectroscopic system is configured to focus electromagnetic radiation onto a localized region of a sample using optical components such as objective lenses and apertures, while simultaneously collecting spectral information — such as absorption, emission, scattering, or reflectance spectra — from the same region.

[0069] ""Microscale" or "Microscopic" refers to a size range of approximately between 1 micrometer (pm) to 100 micrometers (pm), but in some cases, can extend below 1 pm to a nanometer (nm) range.

[0070] ""Nanoscale" or ""Nanoscopic" refers to dimensions ranging approximately from 1 to 100 nanometers (nm). A nanometer is one-billionth of a meter (10 ⁹ meters),

[0071] ""Nanostructured region" refers to a defined area or volume comprising material features, patterns, or structures having characteristic dimensions on the nanometer scale, typically less than 1000 nanometers (nm).

[0072] ""Optical assembly" refers to a combination of optical components configured to manipulate, direct, focus, or modify light within a system, by way of non-limiting examples..

[0073] ""Optical component" or ""optical element" refers to any individual element designed to manipulate, control, or interact with light through reflection, refraction, transmission, absorption, diffraction, or scattering. Optical components include, but are not limited to, lenses, mirrors, prisms, beam splitters, optical filters, diffraction gratings, optical fibers, waveguides, and coatings.

[0074] ""Phase change material (PCM) alloy" is a material composed of multiple elements, typically including chalcogens such as sulfur, selenium, or tellurium, which can reversibly transition between amorphous and crystalline states upon heating and cooling. This phase change results in distinct changes in the material’s physical properties, such as electrical conductivity or optical reflectivity, making PCM alloys useful in applications requiring data storage or thermal regulation.

[0075] "Processor" refers to one or more electronic devices that is/are capable of reading and executing instructions stored on a memory to perform operations on data, which may be stored on a memory or provided in a data signal. The term "processor" includes a plurality of physically discrete, operatively connected devices despite use of the term in the singular. Non-limiting examples of processors include devices referred to as microprocessors, microcontrollers, central processing units (CPU), and digital signal processors. II. GENERAL OVERVIEW

[0076] An important aspect of designing optical devices, apart from their fabrication, is a providing a reliable method to measure and characterize its optical response, which should match very closely with the simulated response. Thus device characterization techniques play a major role in experimental physics or engineering.

[0077] Apart from thin film and device level characterization through optical measurements, an optical setup capable of determination of switching speeds and endurances of a phase change chalcogenide alloys is highly desirable.

[0078] Today, a wide set of chalcogenide alloys are rapidly emerging in the field of reconfigurable nanophotonics. Advancements are heavily focused on a very diverse range of reconfigurable properties exhibited by these materials such as rapid switching between amorphous and crystalline phases, photodarkening, photo dissolution and many more.

[0079] It would be highly beneficial to have a standardized optical measurement setup capable of precisely determining various laser parameters such as pulse energy, repetition rate or peak power required to induce this diverse light induced phenomena. A thorough record of these would not only further enable studying various switching dynamics, but also facilitate developing a perfectly reversible switching framework. Moreover, the switching parameters can be utilized further to have an automated system that can repeatedly switch a thin film of PCM (Phase Change Material) alloy thousands of times and provide a detailed account of the limit of the number of switching cycles that these phase change alloys can endure. Such a system would also help the research community by demonstrating the limitations of these bare films of various chalcogenide alloys.

[0080] In view of the foregoing, as explained herein, the disclosed broadband dynamic testing system is configured for one or more of following:

(i) Broad Band Optical Response [0081] Disclosed examples provide for a microspectroscopic system capable of acquiring spectral data from both plasmonic and dielectric range of metasurfaces patterned on both opaque substrates as well as transparent substrates. More broadly, the system is able to efficiently measure a broad band optical response from nanostructures, as well as unstructured thin films covering visible to NIR range of wavelengths at near normal angle of incidences.

(ii) Small Footprint Patterns

[0082] While measurement capability of the structured regions is desirable, it is also extremely important that the system is capable of measuring reliably very small footprint patterns.

[0083] Fabrication of subwavelength structures for optical metasurfaces, are typically performed using high resolution lithographic techniques such as Electron Beam Lithography (EBL) or Focused Ion Beam (FIB) Lithography, where the cost to fabricate is directly proportional to the overall dimension of the structured area. Thus, a desired objective is achieving a high magnification of the system capable of measuring reasonably small, structured regions while keeping a low angle of incidences.

(iii) Polarization

[0084] While optical responses from a nanostructured film also depend heavily on the polarization state of the incident light, it is desirable to introduce the capability to measure reflection and transmission of such structured regions at both TE and TM polarizations along with the feature to also measure at various intermediate polarization angles.

(iv) Reversible Phase Transitions for Chalcogenide-Based Phase Change Materials

[0085] Chalcogenide materials are widely used in optical devices due to their unique infrared transmission and nonlinear optical properties. These materials, composed of elements like sulfur,

selenium, or tellurium, enable the fabrication of lenses, windows, and fibers for thermal imaging, night vision, and infrared sensors, operating effectively in the mid- to far-infrared range.

[0086] Chalcogenide glasses also exhibit high refractive indices and strong nonlinear behavior, making them ideal for photonic devices, waveguides, and optical switches. Additionally, chalcogenide alloys are used in phase-change memory and optical data storage, taking advantage of their ability to rapidly switch between amorphous and crystalline states.

[0087] In recent years, the chalcogenide material spectrum has seen an exponential grown with new high-quality alloys being introduced rapidly for various telecom and high power computing applications for which are of interest. Each of these materials requires different ranges of energies for optical switching. Therefore, it is important to realize a routine and standardized mechanism to determine the precise amount of energies to achieve effective phase transition between the two phase states.

[0088] Accordingly, in at least one example, disclosed systems deliver precise optical pulse energies needed to achieve reversible phase transitions across the two phases for a wide range of chalcogenide-based phase change materials. Apart from this information, the same system using an automated mechanism is able to provide precise information about the switching endurances for each of these new alloyed compositions.

[0089] As used herein, “switching endurance” refers to the total number of times a chalcogenide material can be switched between the two the phase states in a reversible manner. Therefore, this is an extremely important number as it highlights the true performance and reliability of the material as well as the reconfigurable device demonstration.

(v) Integrated Probe Station

[0090] Disclosed examples also provide a device that integrates an optical setup with a probe station. In at least one example, an FPGA-based probing mechanism is provided. The mechanism is controllable to provide access to individual pixels of such devices.

[0091] The disclosed devices provide an enhanced platform with enough space to position the probes to program the fabricated device simultaneously and record the change in reflection and transmission spectrum. In at least one example, the probe station is controllable to address a specific pixel to reprogram and measuring a crossbar-based reconfigurable multifunctional metasurface-based device.

[0092] In at least one example, the system further includes more specific electro-optic probing capability that is integrated into the system for measuring photonic integrated circuits.

[0093] The main functionalities of this capability include fast and efficient manual alignment of a grating coupler to an input and output fiber, measuring and recording optical response over a desired range of wavelengths with a resolution of 1 pico meter (pm), offering ability to scan all the parameters of a voltage or a current pulse generated by a high speed pulse generator and generating a map of various types of transmission as a function of voltage amplitude levels and pulse widths. The system has the ability to repeatedly switch between two (2) phases of chalcogenide on the photonic circuit and record the switching endurance of the device. The system is also able to record the speed of switching by the incorporation of ultrafast oscilloscope in the range of approximately 6 GHz.

(vi) Measuring Transient Reflection Changes

[0094] In at least one example, the disclosed system provides a feature to measure transient reflection changes in the nanosecond time domain by optically heating a phase change thin film at a spot by a nanosecond laser pulse and measuring reflection response at each nanosecond time instant. In some examples, this is performed at the telecom range of wavelengths such as 1=1550 nm or 1310 nm. To achieve these type of measurement capability the optical setup incorporate pump probe measurement capabilities.

III. CONVENTIONAL INVERTED OPTICAL MICROSCOPE

[0095] FIG. 1A illustrates an example configuration for a conventional inverted optical microscope 100, and exemplifying the optical path therein. The design configuration of the inverted microscope 100 provides a basis for understanding disclosed systems.

[0096] At a general level, the optical microscope 100 includes a main optical assembly 102. Assembly 102 includes the collection of internal lenses, mirrors, beam splitters, and prisms enabling image formation.

[0097] Assembly 102 has a number of input/output ports through which light may enter or exit therefrom. These include: (i) a light source input port 104; (ii) a sample observation port 106; (iii) an imaging output port 108; and (iv) a binocular output port 110.

[0098] Light source port 104 is the entry point for a light source 112 (e.g., a 5 W chip-on- board (CoB) LED) used to illuminate a sample 150 observed. The light source 112 may be used with focusing optics.

[0099] Sample observation port 106 provides a path where light interacts with the sample 150 and passes through the objective lens 114.

[00100] Imaging output port 108 provides a path where light is directed to an imaging sensor 116 (e.g., camera) for digital image capture.

[00101] Binocular output port 110 provides a path where the light is directed to the binoculars for direct human observation.

[00102] In some examples, the sample 150 is further disposed on a moveable stage 152. Stage 152 allows moving and translating the sample to image different portions thereof. In some examples, the sample is a nano-structured or unstructured thin film

[00103] The following is a more detailed discussion of the various components of the inverted optical microscope 100: (i) Light Source and Kohler Illumination Lens Configuration

[00104] A major component in an optical path of an inverted microscope 100 comprises of a white light source 112, e.g., a 5W COB LED. The light source 112 often illuminates the sample 150 through a Kohler illumination lens configuration.

[00105] FIG. IB exemplifies a typical lens configuration to achieve a Kohler illumination. The lens configuration is used to illuminate a sample 150 using an illumination source 112 (e.g., an LED). The Kohler illumination technique ensures even illumination of the sample 150 without forming an image of the illumination source 112.

[00106] In particular, to avoid forming this image, the lens configuration ensures that the light from the source 112 is collected using a high numerical aperture (NA) condenser lens 206 and focused on a point where an iris 208 is placed. The next lens 210 in the optical path is positioned to have its focal spot near the position of the iris 212. This lens 210 takes a defocused image of the light source 112 and propagates it to the input of the objective 114, which then focuses the light on the sample 150, thus evenly illuminating it.

[00107] Furthermore, a diffuser is also used between the condenser lens 208 and the iris to achieve even further illumination. This setup further provides control of the amount of light entering the sample 150 by altering the condenser diaphragm 208 or the iris, which in turn allows the alteration of the sample contrast.

[00108] To this end, the role of the condenser diaphragm 208 in a microscope is analogous to the aperture in photography. While the condenser diaphragm 208 controls the specimen's illumination, the camera's aperture controls the detector's illumination. The configuration shown in the light source section of the microscope schematics in FIG. 1A shows the Kohler illumination setup of the microscope.

(ii) Beam Splitters

[00109] As shown in FIG. IB, a beam splitter 216 is also used. Beam splitters function to split a propagating beam into two beams with a specific splitting ratio. Based on the splitting mechanism, splitters are designed to be efficient in a specific range of wavelengths. Thus, it is critical to characterize and determine the splitting ratios of all the beam splitters present in an optical path within a desired wavelength range and account for the losses in the optical path.

[00110] Two main types of splitters are identified in the optical path of the inverted microscope 100:

Dichroic Mirrors 216 (FIG. IB): The light from the source travels towards the sample 150 through the objective 114, using a reflective dichroic mirror 216 (FIG. IB) with significantly different reflection and transmission properties in the visible and NIR range of wavelengths. Characterization measurements indicate that the mirror's reflection ratio to transmission is around 60:40 in the visible range (400<l<700) but decreases notably in the NIR. Understanding the behavior of these beam splitters at different wavelengths is essential in determining the total losses in the optical path, which helps determine the power requirements of the light sources.

- Prism Beam Splitter 116 (FIG. 1A): This splitter is a prism-based broadband splitter that mainly splits the beam in two directions in a 70:30 manner. Typically, the path where the beam comes out towards the camera 116 has 30% transmission, whereas the other path has 70% transmission. The main reason is that a camera detector 116 has a higher sensitivity and is optimized for low-light operations compared to the human eye.

(iii) Microscope Objectives

[00111] Microscope objectives 114 are one of the crucial components of an optical microscope 100. They are responsible for primary image formation and play a central role in determining the quality of images the microscope 100 can produce. They can be classified as finite and infinite conjugate objectives based on the position where the microscope objective forms the image.

[00112] If the image plane is at infinity, the microscope is an infinity corrected system. These objectives need an additional lens, known as a tube lens, having a specific focal length, which focuses the beam from the objective onto an image plane near the eyepiece.

[00113] On the other hand, traditional finite conjugate microscope objectives have a finite focal distance of about 160 mm, set as a standard by the Royal Microscope Society (RMS). [00114] Therefore, the inverted microscope design 100 is often fixed to accommodate only finite conjugate objectives with the image plane set at a distance of about 180 mm from the objective.

[00115] Furthermore, traditional microscope objectives are refractive in design, which means they comprise a series of lenses to achieve desired magnification. However, due to refractive index variations with wavelengths, traditional lens-based objectives suffer from chromatic aberration. They are thus only optimized for use in a very narrow range of wavelengths, thus limiting their use in broadband-based applications.

[00116] While both refractive and reflective objectives can be used in the setup for broadband spectroscopic applications, reflective objectives are highly preferred mainly to achieve increased performance and image quality from deep-UV to the far IR.

[00117] The most common type of reflective objective is a two-mirror Schwarzschild objective. This system consists of a small diameter "secondary" mirror, held in position by a spider mount, and a large diameter "primary" mirror with a central aperture.

(iv) Relay Lenses

[00118] As shown in FIG. 1 A, relay lenses often comprise of two lenses already fixed into the inverted microscope, which captures the image from the objective and relay it to the eyepiece lens. The focal length of each of these lenses is typically determined to be around 50 mm by treating this group of two lenses as a single unit.

(v) Output Ports

[00119] In general, an inverted microscope has two main output ports 108, 110 for light. As discussed above, in relation to beam splitters - the prism beam splitter 116 splits the light propagation path into two paths, as shown in FIG. 1 A. One of the paths is directed straight through the prism 116 to the eyepiece (via port 110), whereas the other path is directed towards the camera viewport (via port 108). Since the prism introduces significant losses - allowing only 30% of the light to pass to the camera port and 70% to the eyepiece - disclosed examples use the port for the eyepiece for further magnification and measurements. (vi) Sample Stage

[00120] In FIG. 1A, the sample stage 152 provides an effective platform for probing samples during imaging.

[00121] While the sample 150 needs to be illuminated from the bottom to be imaged, typical substrates such as glass slides and cover slips must be transparent. Samples comprising of thin films patterned or deposited on a transparent substrate can be measured by either orienting the patterned region facing upwards or downwards. In the former, light is incident onto the sample through the substrate and thus travels twice through the transparent material.

[00122] In contrast, light directly interacts with the sample in the latter scenario. However, the latter viewing technique, primarily adopted for measurements on opaque substrates such as silicon, poses serious limitations on the possibility of probing while viewing the sample. Therefore, disclosed examples provide a feature to view the sample on opaque substrates to overcome this limitation.

IV. EXAMPLE BROADBAND MICROSPECTROSCOPIC DYNAMIC TESTING SYSTEM

[00123] The following is a discussion of an example system 300 for dynamic microspectroscopy testing and probing. As provided below, various modifications are made to the conventional inverted microscope to provide enhanced functionality for the disclosed system.

[00124] FIG. 2 shows a three-dimensional (3D) representation of the system 300. FIGs. 3A - 3B show a schematic illustration of the various components of the system.

[00125] Broadly, as shown in FIGs. 3A - 3B, the disclosed system includes the following components: (i) the inverted optical microscope assembly 102 - this includes components of a conventional inverted optical microscope, including the reflective objective 114; (ii) a reflection source arm 302 - this is used for transmitting the illuminating light onto sample 150 for measuring reflective properties of the sample 150, as well as being used for housing one or more probing lasers; (iii) an observation arm 304 - this is used for additional magnification of the imaged region of the sample 150, as well as directing the magnified image to both the camera and one or more measuring devices (e.g., spectral analyzers); and (iv) a transmission source arm 306 - this is used for providing transmissive illumination for measuring transmissive properties of the sample 150, as well as housing a laser source.

[00126] In at least one example, the output port of the reflection source arm 302 is coupled to the light source input port 104, of the inverted microscope assembly 102. Further, an input port of the observation arm 304 is coupled to the binocular output port 110, of assembly 102. An output port of the transmission source arm 306 is disposed above the sample stage 152, or otherwise, opposite the reflective objective 114 of the inverted optical assembly 102.

[00127] As used herein, an “input port” refers to an entry point of light into a given arm, and an “output port” refers to an exit point of light out of a given arm. Each “arm” may be interchangeably referred to herein as an “optical assembly”.

[00128] The coupling between the arms and various ports, of the inverted optical microscope 102, may be effected in any manner. For example, this includes coupling (e.g., mechanical coupling) of an arm housing to a housing of the inverted optical assembly (e.g., housings of the respective optical assemblies). This allows the disclosed system to be couplable to any pre-existing inverted optical microscope (e.g., modularly couplable, or removably couple). In other examples, the entire system 300 may be integrated into a single housing unit.

[00129] In some examples, the light passing through the magnifying arm 304 is sent to one or more spectrometers 310 or spectral analyzers. More broadly, the system 300 allows for a clear image of the sample as well as to isolate a nanostructured region (e.g., 30 pm x 30 pm) and relay the light from this region to the spectrometer to record the spectral response. The light may be relayed to the spectrometers through a bifurcated fiber optic cable (see as well 310a, 310b in FIG. 2). In some examples, this cable has a high numerical aperture (NA) (e.g., of 60) to record reflection or transmission spectrum across a broad range of wavelengths spanning, for instance, from 400nm to 1700 nm. [00130] The system also includes a sample stage 152 for holding the sample 150. In some examples, a 15X reflective objective 114 is provided. This objective 114 is primarily selected for the best possible optical performance of the system 300, and further magnification is limited to 10X by the measurement arm 304, as discussed herein.

[00131] To that end, at least one problem with current microscope design’s magnification is that it is insufficient to isolate a nanostructured region (e.g., a 30 pm x 30 pm region) of interest on a sample 150, and measure its optical response at a near-normal angle of incidence. Moreover, the dimensions of any structured region must fall within the 10 pm - 30 pm range as per conventional device standards.

[00132] As a near-normal angle of incidence is required for broadband measurements, higher magnification objectives cannot be used, and the system must operate using lower numerical aperture (NA) objectives, such as a 15X objective.

[00133] To accommodate these limitations, the disclosed system 300 is extended to achieve ten times more magnification. This will allow the nanostructured region to be magnified sufficiently to isolate it using an aperture on a mirror while simultaneously observing the sample’s image on the camera.

[00134] The path of light passing through the binocular output port 110 (FIG. 1 A) is appreciated as being the most favorable route for introducing magnification components. The reason being is that the intensity of light, as determined by the prism beam splitter 116, is at its highest along this path. This would result in more light entering the system, reducing the integration times for the camera and a spectrometer, thus enabling faster and more accurate measurements.

[00135] A series of optical elements are selected from a range of components to build an optical path to magnify the image relayed to the eyepiece port by 10X.

[00136] As provided herein, the system 300 also uses 90° Off-Axis Parabolic (OAP) mirrors with a through-hole (e.g., 3 mm) in the various arms 302 - 306. These are used because they provide minimal loss of energy as compared to other reflective mirrors. [00137] The various components of the dynamic testing system 300 are now described in greater detail.

V. REFLECTION SOURCE ARM (302)

[00138] The following is a discussion of a reflection source arm 302, in accordance with disclosed examples. The reflection source arm 302 allows light, from a light source 302 to follow an optical path into the light source input port 104, of the inverted optical microscope body 102. In turn, this allows illuminating the sample 150 from beneath to measure reflection properties of the sample 150.

[00139] The reflection source arm 302 may be used by itself, or in any combination or subcombination with other features or elements described herein.

[00140] Reference is made to FIG. 4A, which shows an example optical assembly configuration for the reflection source arm.

(i) Light Source (350)

[00141] Light source 350 is selected to provide a broadband response. In at least one example, the light source 350 is a halogen lamp, which is able to provide more broad response as compared to conventional LED white light.

[00142] In some examples, the halogen lamp is a silica or glass encapsulation-based halogen lamp (e.g., a 150 W halogen lamp). In other examples, the light source 350 is quartz encapsulationbased tungsten halogen lamp covering light from UV to far IR (e.g., with 200 W power). In some examples, the lamp 350 is housed in a aluminum box with heat sink to radiate out all the heat to ambient.

[00143] More broadly, tungsten-halogen incandescent lamps operate as thermal radiators, which means that light is generated by heating a solid body (the filament) to a very high temperature. With higher operating temperatures, brighter light is produced. Further, all tungsten-based lamps exhibit emission spectral profiles resembling that of a blackbody radiator, and the spectral output profile of tungsten-halogen lamps is qualitatively similar to those of tungsten and carbon filament incandescent lamps.

[00144] The majority of the emitted energy (up to 85 percent) from tungsten-halogen lamps lies in the infrared and near-infrared regions of the spectrum, with 15-20 percent falling into the visible (400 to 700 nm), and less and 1 percent in the ultraviolet wavelengths (below 400 nm). The soft glass envelope of ordinary incandescent lamps absorbs most of the ultraviolet radiation generated by the tungsten filament, but the fused silica quartz envelope in tungsten-halogen lamps absorbs very little of the emitted ultraviolet light above 200 nm. Since the lenses and the dichroic mirror in the optical path of the microscope are optimized for high performance in the visible, a high-power quartz- tungsten halogen lamp source became highly desired to achieve higher intensity in the NIR range of wavelengths.

(ii) Collection and Collimation Optical Assembly

[00145] The reflection source arm 302 also includes a collection and collimation optical assembly 312 (FIG. 4A).

[00146] Optical assembly 312 includes a series of optical elements selected to produce a collimated light path. In operation, light follows an optical path 314 from the light source 350, through the optical assembly 312, and into the light source input port 104 of the inverted microscope 102.

[00147] In some examples, the optical elements in assembly 312 are selected to produce a collimated light path with a beam diameter comparable to the diameter of the rear aperture of the reflective objective 114.

[00148] The rear aperture diameter of the objective 114 heavily depends on the magnification of the objective and is inversely proportional to the magnification of the objective. This means that the high magnification objectives 114 have very small apertures, which means a high intensity collimated beam needs to be formed to achieve high quality imaging. However, for the disclosed system 300, low NA objectives are used since the purpose is to illuminate the sample 150 at near normal incidences, which leads to the use of low magnification objectives 114. Thus, in at least one example, a beam diameter of half an inch is selected, and a set of lens and mirrors in optical assembly 312 are used to achieve the desired beam profile.

[00149] In at least one example, the optical elements in assembly 312 are arranged and configured to achieve a Kohler illumination in the reflection illumination arm 302. The Kohler illumination is mainly required to achieve epi illumination of the sample 150 where the light reflected from the sample 150 is collected and measured.

[00150] FIG. 4A shows an isolated view of the reflection illumination arm 302, which provides an exemplary configuration for the optical assembly 312. In other examples, other optical assemblies 312 may be used to achieve the Kohler illumination. The optical assembly 312 is also used to achieve the desired output beam diameter.

[00151] As shown, the light from the tungsten lamp 350 - following the optical path 314 - is initially collected using a pair of aspheric lens 402. In some examples, the pair of aspheric lenses 402 have an approximately 20 mm focal length and focus the light on a tight spot.

[00152] The optical path 314 then passes through a further aspheric lens 404. In some examples, the aspheric lens 404 has an approximately 20 mm focal length, and 2 inch thickness.

[00153] The light passing through the lens 404 is then collimated, and is incident on an off axis parabolic (OAP) mirror 406. In some example, the OAP mirror 406 has a 3 mm hole 406’. The OAP 406 may be designed to accept and focus a collimated beam of light at a reflected focal length of 100 mm. The OAP 406 functions to focus the light at a right angle. In some examples, the OAP 406 is designed to focus the light at a 100 mm distance from one end at a right angle.

[00154] Following this, the light is focused onto an iris, and a lens with a focal length of 36 mm is placed 3 6mm away on the opposite side of the iris 408 to re-collimate the beam.

[00155] In some examples, the collimated beam is then passed through a polarizer 410 for polarization dependent measurements. This allows transmission measurements not only for both TE and TM but also at various intermediate polarization angles. [00156] Inside the inverted optical microscope assembly 102, the beam is focused by a focal length lens 120 (e.g., a 50 mm focal length lens) (FIGs. 3A - 3B), which may be positioned inside a varifocal lens tube thus allowing the beam diameter at the aperture of the 15X objective 114 after reflection from the dichroic mirror 122 (beam splitter) placed at an angle of 45° to horizontal, to be less that the aperture diameter.

[00157] The beam, after entering the objective 114 is first incident on a secondary mirror which is then reflected to another mirror which is also known as the primary mirror of the objective. The primary mirror further focusses the beam to a spot on the sample 150, e.g., having a field of view of 1.2 mm.

[00158] FIGs. 4B - 4D illustrate perspective 3D views of the reflection source arm 302 in detail, along with the cross-sectional view of the body showing the lens position.

(iii) Pump-Probe Microscopy

[00159] The reflection source arm 302 may also include one or more lasers for pump-probe measurements. For example, as shown in FIG. 4 A, there may be one or more probe lasers 412a, 412b provided in the arm 302.

[00160] More broadly, pump-probe microscopy is a powerful and versatile technique that plays a crucial role in the field of microscopy, especially for investigating dynamic processes in materials and biological samples at ultrafast timescales. This technique involves using one laser beam to excite the sample (the pump) and another to probe the state of the system after a controlled delay (the probe).

[00161] The importance of pump-probe measurements in microscopy can be highlighted in several key areas such as Ultrafast Dynamics, Non-invasive Imaging, High Spatial Resolution, and determining Chemical and Material Contrast.

[00162] Pump-probe microscopy allows understanding processes occurring on femtosecond (10-15 seconds) to picosecond (10-12 seconds) timescales. This capability is essential for understanding the fundamental interactions and dynamics within materials and biological systems, such as vibrational modes in molecules, electron dynamics in semiconductors, and energy transfer processes in photosynthetic complexes.

[00163] The pump-probe microscopy technique provides a non-destructive means to investigate the structural and electronic properties of samples. By carefully controlling the pump energy, it is possible to excite specific transitions without causing damage, making it ideal for sensitive biological specimens or delicate materials.

[00164] When combined with high-resolution microscopy techniques, such as confocal microscopy or scanning near-field optical microscopy (SNOM), pump-probe measurements can achieve spatial resolutions beyond the diffraction limit. This allows for detailed imaging of sub-micron features and interfaces within complex materials and devices.

[00165] To that end, pump-probe microscopy can offer unique insights into the chemical composition and material properties of the sample. Different materials and molecular structures respond differently to excitation, allowing for the differentiation of components within heterogeneous samples based on their dynamic responses.

[00166] One of the primary materials of interest are chalcogenide alloys. Particularly those like Germanium Antimony Telluride (GST), are of significant interest due to their unique ability to exist in both amorphous and crystalline phases at room temperature (RT). These phases are stable at RT and require only a brief and precise stimulus, delivered either optically via a laser pulse or electrically through Joule heating, to transition between the two states. Each phase exhibits distinct optical and electrical properties; for example, the crystalline phase is more electrically conductive and optically reflective than its amorphous counterpart. This stark contrast in properties has led to the widespread use of chalcogenides in both optical and electronic memory applications.

[00167] Due to their non-volatile nature, low power requirements, and ultrafast transition capabilities between the two phase states, the last decade has seen significant growth in exploring the extensive range of optical properties these material alloys offer. This research primarily focuses on applications in the telecommunications domain. A key area of interest is the speed at which these materials can switch between phases. Recent observations have shown that these materials possess a very high thermo-optic coefficient, indicating that they do not need to undergo a complete phase transition to achieve two distinctly contrasting states.

[00168] One of the primary challenges with these materials has been their relatively slow switching speed compared to other platforms like silicon, especially in applications such as ultrafast modulators that require a full phase transition to achieve high modulation contrast. However, the high thermo-optic coefficients of chalcogenide materials suggest that a complete phase transition may not be necessary to achieve the desired modulation contrast. As a result, these materials can be engineered to require very little power and operate at ultrafast speeds, overcoming one of the main bottlenecks in their application.

[00169] In view of the foregoing, as shown in FIG. 4 A, the reflection source arm 302 may include the probe lasers 412a, 412b. The laser beams are directed through the parabolic mirror 406 via the central aperture 406’.

[00170] As depicted in this figure, it can be seen that the optical path which transmits broadband light can also be used to send monochromatic light allowing single wavelength measurements as well.

[00171] In at least one example, the reflection source arm 302 accommodates two types of lasers: a 650nm laser and a 1310-1550nm NIR laser, utilizing a dichroic mirror 414. The dichroic mirror 414 may be 100% reflective in the NIR wavelength range and 100% transmissive in the visible wavelength range. This optical path is engineered to also channel laser light from the opposite side of the parabolic mirror 406 through the aperture 406’.

[00172] During pump-probe measurements, one of the continuous wave (CW) lasers is directed at the sample 150, with the incident light then being reflected back into the objective 114 and passed to the magnifying arm 304. However, the light at the output of the magnifying arm 304 is now collected by a photodetector 320 (FIG. 3B).

[00173] The PIN photodetector 320 (e.g., which may have a rise/fall time of 200 ps) (FIG. 3B), is connected to an oscilloscope 310 (e.g., a 6 GHz oscilloscope). The pump beam is continuously incident on the chalcogenide thin film sample and is collected by the photodetector 320, thus measuring the reflection of the pump beam from the sample.

[00174] Subsequently, a nanosecond pulsed laser on the transmission arm 306 is programmed to deliver a pulse of 6-10 ns onto the sample, potentially heating it. If the heating is sufficient, the reflection response of the pump beam, as recorded on the oscilloscope 310, will change for a few nanoseconds and can be quantifiably measured. The change in reflection, attributed to the high thermooptic coefficient of chalcogenide materials, allows for the determination of operation speed through a nonvolatile stimulus mechanism.

[00175] Furthermore, the pump-probe measurement capability of the setup enables the measurement of the material’s switching speed. This is measured when the power of the nanosecond probe pulse is high enough to switch an entire 30 pm area in a single pulse, altering the reflection response as recorded by the pump beam on the oscilloscope. This change is recorded almost instantly, and since the oscilloscope can record changes with a resolution of 100 ps, it is possible to quantify how swiftly the reflection changes. Thus, the switching speed of the material can be accurately determined.

VI. OBSERVATION ARM (304)

[00176] The following is a discussion of an observation arm 304, that can be used by itself or with any combination or sub-combination of features disclosed here.

[00177] FIG. 5 shows a close up view of the observation arm 304, according to an example. The observation arm 304 includes three portions: (i) a magnifying arm portion 502; (ii) a beam reducer relay arm portion 504; and (iii) a measurement arm portion 506.

[00178] As used herein through, each “arm portion” may also be referenced herein interchangeably as an “optical assembly”.

[00179] As exemplified, light exits the inverted optical microscope 102 via the binocular output port 110, and follows an optical path 550 through the magnifying arm portion 502. The light is then split - via an OAP mirror 510 with an aperture 510’ (e.g., 3 mm aperature) - along a first optical path 550a, that follows through the beam reducer relay arm portion 504 to the imaging sensor 116a. The light also follows a second optical path 550b through the measurement arm portion 506, to one or more measurement devices 310 (e.g., spectroscopy devices).

(i) Magnifying Arm Portion (502)

[00180] As shown in FIGs. 3 A - 3B, the light reflected from the sample 150 is focused at the back focal plane of the reflective objective 114 which, in some example, is at a distance of 160 mm from the aperture of the objective. The real image formed at this plane is then relayed through a set of relay lenses through the binocular output port 110, where the magnification is set at 15X. However, to further magnify the sample by 10X, a series of lenses is used to form an image on the camera 116a with an overall magnification of 150X. This is necessary to view the smaller nanostructures within the sample 150.

[00181] In view of the foregoing, the magnification arm portion 502 functions to achieve a further magnification of 10X, and within a short distance to keep a minimum possible magnification arm length. To effect this, a lens with a very short focal length is used. In at least one example, a 1 ” aspheric lens with a high numerical aperture of 0.78 and a focal length of f=8 mm is used.

[00182] In at least one example, using this length and a magnification fixed to 10X (m=10), the image distance is calculated to be 88 mm based on the object position of 8.8 mm. The object here is the image output from the objective relayed to the binocular output port 110. Thus, after the introduction of the aspheric lens, a set of two piano convex (PCX) 508 lenses are located along the path 550.

[00183] In some examples, the two PCX lenses 508 are at a distance of around 90 mm from the aspheric lens, and are separated by a distance of around 5 mm. These lenses may have a focal length of 100 m to focus the highly diverging magnified beam at the reflected focal spot of the 90° OAP mirror 506 (e.g., RFL = 100 mm) with a through hole of, e.g., 3 mm. [00184] This magnified image at the focal spot is then propagated, via optical path 550a, to the imaging sensor 116a (e.g., a high resolution (20mp) Amscope camera detector) as a collimated beam via the OAP mirror 510.

[00185] In at least one example, to avoid spherical aberration only 70% of the aperture of the 2” lens is utilized. Thus, an aperture stops to physically limit the solid angle of rays may be used before the first 2” lens allowing 70% of the light to reach the image plane.

[00186] In some examples, to further reduce spherical and chromatic aberrations, the separation between the two PCX lenses 508 is kept at zero with the curved surfaces facing towards each other. Since the image is further converted into a collimated beam by the OAP mirror 510, aberrations were further reduced.

(ii) Beam Reducer Relay Arm Portion (504)

[00187] As shown in FIG. 5, the beam reduced relay arm portion 504 operates to reduce the diameter (size) of the optical beam, and relay the reduced beam to the imaging sensor 116a.

[00188] In the illustrated example, the collimated beam coming out of the OAP mirror 510 has a diameter of around 30 mm, which needs stepping down by half. Therefore, in at least one example, as shown in FIG. 5 - the beam reducer 504 comprises a Keplerian beam reducer configuration.

[00189] In at least one example, to achieve this configuration, a PCX lens 512 is used to collect the collimated beam. Accordingly, the light following optical path 550a enters the relay arm potion 504 by initially passing through the PCX lens 512. In some cases, a 100 mm focal length 2” PCX lens 512 is used to collect a 30 mm collimated beam, which was stepped down by 40% by placing a 40 mm PCX lens 512 placed at a distance of 140 mm from the 2” lens.

[00190] From the PCX lens 512, the light passes through a long pass filter 514. In some examples, the final beam diameter from the PCX lens 512 is 12 mm (0.4 mm x 30 mm), which is then passed through the long pass filter 514. In some examples, the long pass filter 514 is configured to allow all wavelengths higher than 550 nm. [00191] The main purpose of the long pass filter 514 is to protect the camera detector from a 450 nm laser. In some examples, a 550 nm filter 514 is used, rather than a 450 nm filter, because the transmission at or around 450 nm is still around 0.1% . This is high enough to saturate the camera detector when a 1600 mW laser beam is scattered from the sample or a highly reflective surface.

[00192] The output beam, from the filter 514, then passes through a further PCX lens 516, which focuses the beam onto the reduction lens of the imaging sensor 116a. For example, the output beam comprising of a 30 pm nanostructured region fully covering the 3 mm through hole on the OAP mirror 510, is focused using PCX lens 516 having focal lens of 40 mm onto the reduction lens of the camera.

[00193] The camera’s reduction lens further reduces the magnification by half. However, this reduction allows a live high-resolution image of the full view of the OAP mirror surface with the aperture at the center of the view.

(iii) Measurement Arm Portion (506)

[00194] Continuing reference to FIG. 5, the function of the measurement arm portion 506 is to collect light and direct it to an optical measurement system 310. In some examples, the measurement system 310 is one or more spectrometers (FIG. 3 A). In other cases, it may be an oscilloscope (FIG. 3B).

[00195] In at least one example, the measurement arm portion 506 includes an achromatic convex lens 520 (FIG. 5). For example, a ’A” achromatic convex lens with focal length of 50 mm is used. The lens 520 may be placed in a zoom lens housing. The housing may have a linear travel of 18 mm.

[00196] As shown in FIGs. 3 A and 3B, the image formed may be captured using a fiber cable 314 (e.g., a high NA multimode fiber cable). This cable may be coupled to an SMA fiber adapter 522 (FIG. 5). This adapter may be placed into another zoom lens housing. In some examples, this housing has a linear travel of 1.16”.

[00197] Both the lens and the fiber positions are adjusted for nominal visible and maximum NIR signal strength. The main reason for this arrangement was the difference in focusing abilities of the lenses in the optical path for visible and NIR range of wavelength leading to different position of focal spots for visible and NIR wavelengths.

VII. TRANSMISSION SOURCE ARM (306)

[00198] The following is a discussion of a transmission source arm 306, that can be used by itself or with any combination or sub-combination of features disclosed here.

[00199] As shown in FIGs. 3A - 3B, in some examples, the system 300 further comprises a transmission source arm 306.

[00200] The transmission source arm 306 is facilitates three functions: (i) to provide an illumination source to measure transmission properties of the sample 150; (ii) in some examples, provide a laser source 318 to modify different portions of the sample 150, such as to have different optical properties (which are then tested) - e.g., phase switching the sample; and (iii) provide an imaging sensor 116b for viewing the sample 150 over the top.

[00201] In some examples, the arm 306 may not necessarily include the laser 318 and/or transmission illumination source 316.

[00202] FIG. 7A exemplifies an optical assembly configuration for the arm 306. As exemplified, the arm 306 comprises one or more of: (i) a light transmission arm portion 702, and (ii) a laser arm portion 704. In some examples, the arm 306 may include only one of the arm portions. The arm 306 also include the transmissive objective lens 706.

[00203] FIG. 7B provides a three-dimensional (3D) representation of the arm 306.

(i) Light Transmission Arm Portion (702)

[00204] While the capability to routinely measure reflection is heavily important for studying metallic films, it is also highly desirable to study both reflection and transmission in various dielectric films since it allows us to better understand the losses in the film. [00205] The transmission arm portion 702 may include a transmission light source 710. Transmission light source 710 may be substantially similar to the reflection light source 302 (FIG. 4A) to provide broadband optical properties. For instance, it may a 250W quartz tungsten lamp, which may be enclosed in a copper box, or any other broadband light source.

[00206] The transmitted light, from the transmission light source 710, may follow an optical path 750a. In particular, along optical path 750a, light from the transmission source 710 is collected using a condenser lens 722 (e.g., a 1” condenser lens with a focal length, f = 20.4 mm) which is then focused at a point where an iris diaphragm 724 is placed. Another condenser lens 726 with same focal length may then be positioned at a distance from the iris 724 (e.g., a distance of 20.4mm) in order to collimate the beam.

[00207] In some examples, the collimated beam is passed through a polarizer 720 for polarization dependent measurements. This allows transmission measurements not only for both TE and TM but also at various intermediate polarization angles.

[00208] Along the optical path 750a, the light is collimated and passes through a beam splitter 712 (e.g., a pellicle beam splitter). In some examples, this beam splitter has approximately a 90% transmission and 10% reflection. The reflected light from the source 710 is directed opposite to the imaging sensor 116b (e.g., camera).

[00209] The transmitted part of the beam is incident on the 90° OAP parabolic mirror 714 with a through aperture 714a (e.g., a 3 mm through hole and a 100 mm focal length), reflected, and directed to a condenser lens 708 along optical path 750. This condenser lens 708 further focusses the beam on to the sample 150 through the reflective objective 706. Reflective objective 706 may be mounted on a variable zoom housing, e.g., with a travel of 1.16”. The reflective objective 706 may have a 15X magnification.

[00210] This focused light is collected by the reflective objective 114, placed at the bottom of the sample, which then relays the light to the measurement device, via the observation arm 304 (FIGs. 3A and 3B). [00211] The alignment of the transmission source arm 306 is critical since the focal spot on the sample 150 needs to be perfectly aligned with the focal spot on the sample incident from bottom in the reflection arm configuration.

[00212] In at least one example, the numerical of the reflective objective 706 used to focus the beam onto the sample 150 was 0.28 to achieve similar mode excitations conditions for both reflection and transmission measurements.

(ii) Laser Arm Portion (704)

[00213] The laser arm portion 704 includes a laser source 318. In some examples, this is a pump pulsed laser (e.g., wavelength (1) of 450 nm).

[00214] As explained in further detail below, the purpose of the laser 318 is to modify the sample 150, such as by triggering an optical switching behavior of a chalcogenide material. This allows the system 300 to both modify the optical properties via the laser 318, and then measure the reflection and/or transmission properties of that modified material. In this manner, the system 300 is able to not only measure static properties of materials, but also the variable dynamic properties (e.g., as modified by the laser 318).

[00215] As shown in FIG. 7A, it is readily apparent that the optical path for transmission of light 750a and the laser beam path 750b share a common route 750. The primary motivation behind this is to enable the concurrent measurement of both reflection and transmission at the exact location where the focused laser spot was switched.

[00216] In order to achieve this, the optical path 750, 750b extending from the reflective objective 706 to the output port of the laser incorporates a condenser lens 708 (e.g., a 1” condenser lens) immediately after the objective 706. In some examples, this is followed by a varifocal zoom housing that facilitates the movement of the objective 706 and lens assembly, allowing for adjustments in focal spot.

[00217] The laser beam then proceeds through an aperture 714’ (e.g., a 3 mm through aperture) of the 90-degree off-axis parabolic (OAP) mirror 714. Along the optical path 750b, this mirror is followed by a continuously variable neutral density (ND) filter wheel 716. This filter wheel may have optical density values that range from 0.04 to 4.

[00218] The image displayed on the camera 116b view port shows the aperture of the OAP 714 through which the laser beam passes. The specific region of interest (ROI) on the sample is navigated by translating the sample stage 152 and brought under the aperture 714a of the OAP 714 displays on the camera view port, rendering the sample invisible. This ensures that the laser beam, which passes through the same aperture 714’, is focused on the vicinity of the ROI. However, to guarantee that the ROI is entirely exposed, a large area covering the ROI is rastered to allow for full exposure. This feature is only useful for exposing relatively large areas comprising features since the magnification in the top viewing arm is limited to only 15X.

VIII. LASER SOURCE

[00219] The following is a discussion of an example laser source 318 that may be used, in the laser arm portion 704 (FIG. 7A).

[00220] To achieve a significant tuning of the optical response of chalcogenide based reconfigurable range of devices, an optical switching framework comprising of a tightly focused pulsed laser is highly desirable at a specific region of interest.

[00221] Disclosed embodiments are capable of delivering precise laser pulse energies to rapidly switch between the amorphous and crystalline phases for a thin film of chalcogenide deposited on a device or simply on a silicon or glass substrate.

[00222] Currently, a wide range of chalcogenides are rapidly emerging in the field of photonics with widely varying energy requirements for achieving reversible phase switching. These energy requirements not only vary with deposition conditions such as base pressure, the also vary with thickness of the film.

[00223] It has also been observed that doping the chalcogenide with metals, such as silver, also affect drastically the pulse energies to switch between the two phases. Thus, it is extremely important to determine the exact amount of energy required to achieve successfully phase transition between amorphous and crystalline phases.

[00224] Furthermore, repeated phase switching in chalcogenides have also shown a slow and steady drift in the optical response of the devices due to various reasons such as elemental segregation and void formation. Because of these chalcogenides exhibit limited endurances to repeated phase switching.

[00225] Apart from the non-volatile phase switching behavior, chalcogenides also exhibit a plethora of other light induced affects such as photodarkening, photo dissolution, photobleaching and many more.

[00226] A severely overlooked property of metal-doped amorphous chalcogenide semiconductors (MdACs), particularly certain sulphides and selenides, is that they exhibit directional photo-induced long-range movement of their constituent metallic ions when exposed to light with a photon energy equivalent to or higher than the band gap of the glass. This “photo-ionic” movement can result in non-volatile changes of material properties (refractive index and conductivity) at the nanoscale facilitating robust, non-binary dynamic modulation of light without needing a phase transition.

[00227] Thus, the system 300 is configured to not only include static measurement capability, but also dynamic measurement capability. In particular, the dynamic measurement capability is such that the material can be optically treated with precisely controlled laser pulses to achieve desired interaction of light with the material.

[00228] In at least one example, the laser 318 is a nanosecond pulsed laser. It may have a peak power of 1600 mW was integrated which has been focused to a spot size of around 8-10 pm.

[00229] It has been shown that the amount of energy required to achieve amorphization and crystallization is the in the order of few nanojoules. And it had been shown earlier that even though chalcogenides, such as GST (Ge2Sb2Tes (Germanium-Antimony-Tellurium)), can be amorphized with a single femtosecond pulse, the crystallization still requires a train of femtosecond pulses spaced by a few nanoseconds. This suggests that to incorporate an initial switching functionality a nanosecond pulsed laser is good enough. However, the input port in the system 300 can be replaced with a femtosecond pulsed laser setup to further incorporate feature to study nonlinear properties in various materials.

(i) Nanosecond Pulsed Laser and Optical Path Configuration

[00230] The utilization of blue lasers offers the ability to generate much shorter wavelengths, resulting in the capacity to focus the beam to sizes that are extremely close to diffraction limits. This capability allows for the concentration of beam energy into an extremely small spot, thus producing high power densities. Combining this feature with the high absorption of chalcogenide in the visible to UV range of wavelength makes it possible to realize extremely small phase switched spots using ultra-low power pulses.

[00231] Accordingly, in at least one example, the laser 318 comprises a Thorlabs™ 450 nm nanosecond pulsed laser, which has a maximum peak power of 1600 mW and a pulse width that can be adjusted in 15 discreet intervals ranging from 6 ns to 129 ns. This laser 318 is used for phase switching measurements on chalcogenide thin films. Additionally, the maximum repetition rate allowable by the laser 318 is 50 kHz, signifying that each nanosecond pulse is spaced 20 ps apart.

[00232] It is important to note that the output beam profile of the pulse laser diode is elliptical, and due to its differing divergence for the major and orthogonal minor axis, it leads to a rectangular beam profile. The different divergence of major and minor axis results in a varying beam profile as a function of distance from the output of the laser diode. It was observed that the initial horizontal thin rectangular beam profile changed to a vertical rectangular beam after a certain amount of distance.

[00233] Nonetheless, at a distance of 45 cm from the output port of the laser 318, the beam shape is square, with a size of around 1.5 mm. This square beam was then passed through a 1 " aspheric condenser lens having a focal length of 20.4 mm and NA of 0.6, leading to an alteration of the beam divergence. This alteration causes the beam to be incident on the secondary mirror of the reflective mirror at a distance of around 30 mm, with sufficient size to fill the secondary mirror of the reflective objective. Finally, the reflected beam from the secondary beam, after undergoing reflection from the primary mirror, is focused onto the sample 150, leading to an achieved spot size of around 8-10 pm. (ii) Laser Mount

[00234] In some examples, to ensure maximum flexibility in terms of beam alignment, the laser 318 is affixed to a laser mount. The laser mount may be a kinematic mount, such as part of a Thorlabs™ cage system. This mount allows for 1 mm XY translation, a 4- degree tip and tilt, and 3 mm translation along the optical axis.

[00235] A Sigilent function generator and power supply may also be connected to the pulsed laser 318 to regulate its operation. In at least one example, the function generator produces a 1VPP square trigger pulse at a maximum frequency of 50 kHz. By rotating a screw that is linked to a stepper motor, a mount located at the rear end of the pulsed laser diode can be controlled to vary the pulse width, with 16 discrete pulse width configurations that range from 6ns to 129ns.

[00236] In order to achieve even greater control over the pulse width, a mount may be 3D printed and attached to the shaft that is coupled to a stepper motor. A controller (e.g., Arduino) may be employed to manage this mechanism and is linked to a front-end desktop software component that is installed on the system. This software control mechanism allows for precise control over the pulse width via the controller-coupled stepper.

[00237] Additionally, a desktop-installed software may be capable of operating the function generator using specific commands that turn the laser on and off, establish a desired trigger pulse frequency, and perform other related operations.

[00238] A more comprehensive discussion of this software and automation component is provided further herein.

IX. USING SPECTRAL ANALYZER TO CAPTURE REFLECTION AND TRANSMISSION SPECTRUM

[00239] As exemplified in FIG. 3 A, the reflected and transmitted light signals, from a specific region of interest from the sample 150, may be analyzed using one or more spectral analyzers 310.

[00240] In doing so, the optical output from the observation arm 304 is fed into a fiber cable 314 (e.g., a high NA bifurcated fiber cable). In some examples, the filter cable 314 is used to split up the output signal into two and feed separately into two different spectrometers, namely: visible spectrometer (310a) and NIR spectrometers (310b) (FIG. 2).

[00241] While the visible range of spectrometer 310a has the capability to measure the reflection and transmission in the visible range with 400 < <1100, the NIR spectrometer 310b is used to measure the spectrum in the range from 930<k<1670.

(i) Spectral Analyzer to Capture Reflection Spectrum

[00242] With respect to the reflection spectrum, this is measured by: (i) initially, measure a light spectrum property of the system 300; (ii) a dark spectrum property of the system 300; and (iii) determine the measured spectrum based on the measured light and dark spectrum properties.

[00243] fa) Light Spectrum (RD

[00244] The measured light spectrum corresponds to the photon count signal gathered directly from the reflection light source 350. During reflection measurements, the light source signal is captured by simply replacing the sample 150 with a mirror. To determine the light spectrum, the following steps are undertaken:

[00245] First, the sample 150 - placed on the stage 152 - is brought into focus such that a clear image of the sample is visible on the reflection camera 116a. This step sets and fixes the Z-axis position of the sample 150. At this position the light incident on the sample has the maximum intensity.

[00246] Second, the sample 150 is simply replaced with a mirror and all the reflected light is captured by the reflective objective 114 and passed to the spectrometer 310 as a light spectrum. [00247] It needs to be noted here based on the optical path in FIG. 3, that the light from the source 350 first goes to the beam splitter or the dichroic mirror which splits the beam into two right angle paths. The beam going to the sample is reflected and comes back to the dichroic mirror and is split again into two orthogonal paths. The light passing through the dichroic mirror in this case reaches the spectrometer 310 as the light spectrum signal.

[00248] (b) Dark Spectrum (RD)

[00249] After capturing the light spectrum, the next step is to capture a dark spectrum. The dark spectrum is defined as the background noise in the system 300 which is mainly due to various reasons such as light scattering and absorption from the dichroic mirror in the optical path. The dark spectrum may be determined as follows:

[00250] First, the reflective light source 350 is switched OFF and a spectrum is recorded.

[00251] Second, the light source 350 is switched ON and no sample is placed at the focal spot of the objective to capture the spectrum when no reflective surface is present in the optical path.

[00252] Comparing the two spectra showed significant differences for NIR and visible range of wavelengths. In the visible wavelength range the OFF-state spectrum and the no reflection spectrum matches perfectly as compared to significant difference between the two in the NIR wavelength range. This suggests significant scattering at the dichroic mirror for the NIR wavelength range resulting in an offset signal which is always present in the system. Thus, the dark spectrum for the NIR measurement is measured differently than the visible range measurement in order to extract the embedded background in all measurements and discard it.

[00253] During reflection measurements in the visible range the dark spectrum was recorded by blocking the path of the reflected light to the spectrometer.

[00254] (c) Measured Spectrum (RM)

[00255] After measurement of the dark and light spectrum, the reflection from the sample is calculated based on the Equation (1), RM is the reflected signal from the sample and the RL and RD are light and dark signal. RM RD (Tl

Reflection (%) = — - — x 100 '

RL ~ RD

(ii) Spectral Analyzer to Capture Transmission Spectrum

[00256] The sample viewing under transmission settings is very similar to the reflection setup. The main difference in this situation in the sample illumination source. Only transmissive samples such as glass or silicon can be used for transmission measurements. While glass is transmissive in visible to NIR range of wavelengths, silicon is transmissive in only NIR wavelength range.

[00257] To view the sample on the camera 116b, the bottom light source can be used to bring the silicon-based sample in focus and for viewing samples on glass substrates both the bottom or the top light sources can be used view the sample and focus it. Once the sample is in focus and the region of the interest is positioned over the aperture displayed on the viewing screen, the spectrometers can be connected, and the following steps are followed to collect the transmission response from the sample.

[00258] (a) Light Spectrum (TL)

[00259] The process to gather the light spectrum is dependent on the substrate on which the film is deposited. For example, if the substrate is a glass slide, then the sample needs to be replaced with a glass slide and the light passing through the glass slide is captured as a light spectrum, TL. Similarly for silicon substrate-based samples, a clean silicon substrate needs to be used to replace the sample and the light passing through this substrate needs to be collected as a light spectrum

[00260] (b) Dark Spectrum (Tp)

[00261] The dark spectrum is a simple blocking of the light passing through the sample which needs to be collected and saved as a dark background spectrum.

[00262] (c) Measured Spectrum (TM)

[00263] Finally, after the measurement of the dark and light spectrum, the overall transmission from the sample can now be calculated based on the Equation (2), where TM is the transmitted signal from the sample and the TL and TD are light and dark signal. T_M — T_D

Reflection (%) = — - — X 100

TL ~ T_D

X. REFLECTION TESTS - MEASUREMENTS AND COMPARISON WITH SIMULATIONS

[00264] Various broadband reflection and transmission measurements using the system 300 were performed on both structured, as well as unstructured films with known spectra, to test the accuracy of the system.

[00265] For any system to be reliable, it is critical that the results generated by it are reliable. This can be ensured only when the results are compared with commercially reliable and tested equipment, such as an CRAIC microspectrophotometer by CRAIC Technologies™.

(i) Comparison of Structured Sample with CRAIC Measurements and Reliability Check

[00266] The initial measurements were conducted on structured gold films deposited on silicon, comprising of nanograting patterns of four different variations, as illustrated in FIG. 9, which displays microscope and SEM images of the gratings on silicon.

[00267] The patterns were fabricated using four different dose settings in a focused ion beam lithography session, resulting in varying etch line width and depth across the four patterns, leading to different optical responses.

[00268] These films were produced at the Optoelectronic Research Centre at the University of Southampton, and a commercially available CRAIC spectroscopic microscope was used to measure and record the reflection. The spectroscopic measurements and image clarity served as a benchmark for designing the optical setup. Additionally, a LUMERICAL FDTD model of the patterns was developed and simulated to enable easy comparison between experimental and simulation spectra. [00269] Once the design of the optical experimental setup was finalized, reflection measurements for all structured components were taken for TE polarization and compared with CRAIC results.

[00270] FIGs. 10 (a)-(d) provide a comparison of the results extracted from simulation, CRAIC, and the optical setup measurements of system 300.

[00271] While the optical setup results significantly matched the simulated results for each sample, the results sometimes deviated from the CRAIC results due to sample degradation over 4-5 years, which could allow the deposition of dust or unwanted particles within the etched line patterns, resulting in slight variations in the geometry of the grating lines.

[00272] By sweeping the etched line widths and height of the line, a specific geometric configuration was found where the simulated reflection spectrum matched well with the measured spectrum taken by the system 300. Therefore, the optical setup reliably reproduces the high-quality polarization- dependent resonances expected from structured films.

[00273] System 300 was also used to record reflection responses from structured films. A measurement was performed on a SiN membrane with a metasurface structure, which displays asymmetric transmission. This is demonstrated in FIG. 11, where FIG. 11 (a) exhibits an SEM image of the periodic nanograting structure patterned on an Si deposited on top of a 300 pm thick silicon nitride membrane using FIB lithography. FIGs. 11 (d) and (e) show the reflection and transmission measurements taken at TE and TM polarization, respectively.

[00274] The microscope images depicted in FIGs. 11 (b)-(c) illustrate the reflection and transmission view of the sample placed on top of the circular aperture while being measured with visible and NIR spectrometers. Linearly polarized light along a specific direction was enabled by a polarizer in front of the light source to capture TE and TM polarization.

[00275] Initially, the reflection and transmission measurements were performed by orienting the sample to align the grating lines along the direction of the electric field oscillation. Subsequently, the sample was rotated to make the electric field direction perpendicular to the grating lines, and the measurements were repeated. (ii) Comparison of Reflection Measurements Performed on Unstructured Samples with Simulations

[00276] The system 300 was used to validate the optical constants obtained by fitting the ellipsometry data. As discussed earlier, ellipsometry data analysis involves creating a model to describe various sample properties. This model is then used to calculate the predicted response from Fresnel’s equations describe each material with their thickness and optical constants. If the thickness and optical constants are unknown, an initial estimate is used, and the calculated values are compared against experimental values.

[00277] During this process, unknown material properties such as surface roughness, thickness, optical constants, etc., are varied to match the experimental data. The best match between the model and experiment is achieved through regression, and an estimator such as MSE is used to quantify the differences. The best match is found at the global minimum of the variation of the MSE in the parameter space, which comprises the list of material properties varied to achieve the best fit of the model to experimental data.

[00278] While the global minimum is highly desired, it is often possible that the regression algorithm will stop at a local minimum instead of a global minimum, depending on the starting material properties such as thickness or surface roughness and other MSE structural conditions. In such scenarios, the derived optical constants may not be correct. However, it is possible to check the correctness and reliability of the derived optical constants by simulating a simple thin film on a glass/silicon substrate model using Lumerical FDTD solver.

[00279] The model mainly involves a thin film with the derived optical constants and thickness derived through fitting. The FDTD simulation region includes periodic boundary conditions in the X- and Y-direction and a perfectly matched layer in the Z-direction. The reflection monitor placed above the source can be used to collect the reflection data, which can be compared to the reflection spectrum recorded using the experimental optical setup developed here. If there is significant overlap of the two spectra across the entire wavelength range from 400 nm to 1700 nm, the optical constants can be documented and used for various device simulations. [00280] FIGs. 6 (a)-(d) show an example of the optical constants derived through fitting of the ellipsometry data for a thin film of GST. The thickness of this film was approximately 120 nm, which was used along with the optical constants to generate a simulated reflection spectrum using the FDTD model described as before. This simulated spectrum is then compared against a measured reflection at near-normal incidence using the experimental setup. It can be observed in the figure that there is significant match of the experimental and theoretical reflection results, giving us confidence in the optical constants derived through the fitting of the ellipsometry data.

XI. SAMPLE STAGE SUPPORT SYSTEM

[00281] The following is a description of a support stage assembly, for a sample stage 152, that can be used by itself or in any combination or sub-combination with the features and components described herein.

[00282] FIG. 12 provides an illustration of an example support stage assembly 1200, in accordance with at least one example. The exemplified support stage 1200 may be used for support alignment and levelling of a sample stage 152.

[00283] More broadly, it is important to maintain a precise angle of incidence of light on the sample 150, particularly when dealing with structured samples that are highly sensitive to such factors. The majority of nanostructuring is engineered for near normal illumination - accordingly, any tilting or deviation from this angle results in optical responses that deviate from the expected values.

[00284] Additionally, tilting of the sample stage 152 can lead to a shift in the focus position of the sample 150 from one stage position to another, resulting in the sample going out of focus when moved to another spot. Therefore, it is crucial to take special care to maintain the flatness of the stage and eliminate any tilt.

[00285] As exemplified in FIG. 12, the support stage 1200 includes an external support framework to lift up the support stage to accommodate a reflective objective 114. In some examples, the stage accommodates a reflective objective 114 of approximately 2" in length, which has dimensions much greater than a traditional refractive objective. [00286] As shown, an extended aluminum plate 1202 is provided around the sample stage 152. In some examples, the extended plate 1202 is placed at a height of 25.4 cm above the optical table.

[00287] To ensure that the stage 152 is perfectly parallel to the optical table, in some examples, four sets of optical posts 1204 of the same height are used to maintain the height of all corners of the extended plate 1202. The extended plate 1202 is then connected to the sample stage 152 from the top using aluminum extended connectors.

[00288] In some cases, long screws may be used to maintain a parallel distance between the stage 152 and the extended plate 1202, and the offset distance between the stage 152 and the extended plate 1202 may be maintained equally by introducing an equal number of nuts. This ensures that the sample stage 152 is perfectly parallel to the optical table, and the optical axis to the sample 150 is perfectly orthogonal to the sample plane.

(i) Stage Translation Mechanism

[00289] In at least one example, the sample stage 1202 comprises a translation mechanism, which may include an inbuilt mechanism for X and Y translation of the sample 150.

[00290] As exemplified, this mechanism may be achieved using two plates that slide on each other. In some examples, the motion of the mechanism may be made smooth with ball bearings and precisely made smooth surfaces.

[00291] When this stage is coupled to the extended plate 1202, the upper part of the sample stage 152 is able to move freely in X and Y directions. In some examples, the stage has a travel length of about 4" in each direction.

[00292] To eliminate possibility of slipping or movement of the sample on the stage 152, an additional stage accessory may be used, and may be made quartz material. This accessory may couple to a vacuum supply (e.g., via a doughnut- shaped aluminum chuck located on the bottom of the accessory), which has an inner cavity connected to the vacuum supply. The quartz accessory is fashioned to contain a central circular hole (e.g., of roughly 10 mm diameter), where a sample of specific dimensions is placed for measurement purposes. [00293] In order to hold the sample securely in place, the central hole may be surrounded by three miniature holes (e.g., of 1 mm diameter) on each side. In some examples, these miniature holes are coupled to the vacuum supply through the aluminum doughnut-shaped chuck placed on the bottom side of the quartz plate.

[00294] As a result of this design, any sample of sufficient size to cover all of the small holes would not move or slip once the vacuum is turned ON. The primary objective of this infrastructure is to eliminate any vibrations in the phase switch patterns that may have been generated by the rapid movement of the dual-axis stage.

(ii) Motion Control Mechanism

[00295] The sample stage 152 may be made movable and translatable using any movable configuration. In some examples, the stage 152 is equipped with a manual control mechanism for X and Y travel via a shaft coupled to the stage through a gear assembly.

[00296] In other examples, a more sophisticated motorized design is used for the purpose of fully automated rastering functionality via the laser 318 (FIGs. 3 A and 3B). The fully automated design enables the precise movement of the tightly focused laser beams on the sample 150. In some examples, this automated design is enabled by a stage motion control system 818 (FIG. 8), which is described in greater detail below.

[00297] As noted previously, the laser 318 may be used to vary optical properties of different portions of the sample, which can then be tested (e.g., for reflective and transmissive properties). For example, this can be used for determining the accurate laser pulse energy dose required to achieve different phase transitions in a sample material.

[00298] Accordingly, the motorized motion mechanism can be used for moving a tightly focused 8-10 pm phase switched spot in a particular direction, while simultaneously moving in the orthogonal direction. This can produce an incredibly closely spaced set of phase-switched laser scan lines, thereby generating square-shaped phase switched areas, e.g., with dimensions exceeding 30 pm. Further, this facilitates the comfortable measurement of both reflection and transmission by positioning these switched areas on top of the 3 mm aperture of the 90° OAP mirror during the measurement. [00299] In at least one example, automation motion control enables the generation of an array of closely spaced squares in the sample (see the static test matrix in FIG. 14) created by extremely closely spaced line scans. This array of squares is created with varying laser pulse energies, which are measured as part of the static testing workflow to determine the accurate laser pulse energy dose required to achieve phase transition. Once the dose is determined, a large area scan should be performed using the determined dose to create a large enough phase-switched (crystalline or amorphous) spot, which can be reliably measured using ellipsometry to determine the optical constants.

[00300] Additionally, the automated stage movement can be used to center the sample 150, enabling polarization measurements without moving the sample out of the field of view. Presently, polarization measurements are performed manually, and automation would allow for faster measurements. The design also allows for precise navigation and measurements on the sample with a simple drag of the mouse on the live view image on the screen.

[00301] In at least one example, the motorized movement is achieved using a two-axis motion controller design. This mechanism may be placed on the extended support plate 1202 and coupled to the sample stage 152 from below the support plate.

[00302] At least one goal of the automation motion control design is to enable computer or joystick-controlled movement of the sample stage 152, which would facilitate a wide range of functionalities such as laser beam pattern writing.

[00303] In some examples, a user can upload any pattern (e.g., in the form of a GDS mask file), and the software can trigger precise stage movements in two dimensions to draw various patterns on the sample using a focused laser beam.

[00304] As further exemplified in FIG. 12, to achieve precise movement of the stage 152 in two orthogonal directions, the first axis may be implemented on top of the extended stage plate 1202. In some examples, this involves installing three guide rails each supporting a wide sleeve bearing carriage (e.g., a 70 mm wide sleeve bearing carriage). These carriages are then coupled to a single aluminum plate, which allowed only uniaxial motion with no room for tip or tilt of the carriage. The triple carriage connected plate system results in a highly stable error-free single-axis motion.

[00305] A motor, such as a stepper motor (e.g., NEMA 23 stepper motor with a load capacity of 2001bs) may be used for precise movement. The motor may be coupled with a lead screw offering a travel distance of 8 pm per full step for high- resolution movement.

[00306] The stepper motor may be controlled with a driver capable of driving the stepper with multiple step resolution settings. For example, the resolution setting may cover 1, 1/2, 1/10, 1/25, 1/64, and 1/100^th of a step, allowing the realization of a maximum travel resolution of 80 nm per step.

[00307] Since such high resolution comes at the cost of reduced torque, the motors may be driven at a resolution setting of 1/10^th of a step. The lead screw of the stepper may then be connected to a flange nut anchored to the aluminum plate fixed to the three carriages running on the guide rails. Continuous rotation of the lead screw would allow the forward or backward motion of the platform.

[00308] In some examples, the initial single axis setup is enhanced to a dual axis system by adding another motor, such as another stepper motor. The stepper motor have a lead screw in a perpendicular direction to the first axis platform. This produces orthogonal high-resolution travel by connecting the second motor to a 70 mm carriage on a guide rail fixed on top of the first axis platform, which is then connected to the sample stage.

[00309] The sample stage 152 includes two parts, with the top part sliding on top of the bottom plate, allowing precise control over the translation of the sample in two dimensions. The stepper motors were operated at 1/2 and 1/10 step resolutions using stepper drivers controlled by a controller 1206 (forming part of the stage motion control system 818). The controller 1206 may be programmed to control the sample stage position to produce, via the laser 318, rastered squares and other patterns on the sample at various speeds by controlling the pulse clock frequency.

[00310] The speed of translation is crucial when scanning a laser pulse across the sample, as the cumulative effects of multiple pulses can change the material properties. For example, if a material does not have time to cool down before another pulse was delivered, it could experience a cumulative rise in temperature. The number of pulses delivered at a spot is generally directly proportional to the amount of change observed in reflection or transmission due to ionic movement in the film. Therefore, the speed of the motors is programmable through a software interface or a joystick-based potentiometer control, allowing manual speed control over the two-axis motion of the sample stage.

XII. ELECTRONIC CONTROL SYSTEM

[00311] To enable the system 300 for fully automated control - embedded electronics are introduced in various parts of the optical path of the system.

[00312] FIG. 8 shows an example control system 800 for the dynamic testing system 300. As shown, the system 800 includes a controller 802 (e.g., an Arduino controller). Controller 802 can include a processor 802a coupled to a memory 802b, and in some cases a communication interface 802c (e.g., an antenna or other communication port).

[00313] Communication interface 802c may be used to transmit and receive data (wired or wireless) from external computing systems, such as a user computer terminal 202 (FIG. 2). In some cases, the user terminal 202 may include a display interface 204 for displaying a graphical user interface (GUI) allowing the user to interact with the system 300. For example, the user terminal 202 may also include a processor and memory, whereby the memory stores a system control software that incorporates the GUI.

[00314] As shown in FIG. 8, controller 802 may be coupled to one or more of: (i) a shutter control system 804; (ii) a variable focus control system 806; (iii) a laser pulse width control system 808; (iv) a laser power control system 810; (v) a camera control system 812; (vi) a laser repetition rate control system 814; and/or (v) a spectrum control system 816.

[00315] In at least one example, one or more of the control systems 804 - 818 includes one or more motors to vary hardware positions (e.g., stepper motors). Accordingly, controller 802 can control the motor positions via data control signals sent thereto. One or more of the system may also comprise sensors (e.g., encoders) coupled to the motors. These sensors can transmit sensor data back to the controller 802, which may be analyzed to determine a stepper motor position. For instance, this may be part of a feedback mechanism.

(i) Shutter Control System (804)

[00316] Shutter control system 804 may be used for controlling the automated transmission and reflection measurements of samples.

[00317] FIG. 13 shows various example images for a controllable ring actuated iris diaphragm that control the light in the measurement path, as part of the system 804. Rotation of the ring via the shutter control system 804 allows the opening and closing off of the iris, thus controlling the light in the measurement path. These iris diaphragm can be placed in front of the broadband reflection and transmission sources 350, 710 to allow or block light therefrom.

[00318] More broadly, to enable automated reflection and transmission measurement during static testing, light from both reflection and transmission arm light sources 350, 710 require synchronization (FIGs. 3A, 3B). This means that when a transmission data is being acquired, the reflection arm light source 350 needs to be OFF, and the transmission arm source 710 needs to be in ON state. Similarly, the opposite configuration needs to be followed for reflection data acquisition. Accordingly, the controllable iris diaphragm configuration is used to achieve the switch ON and OFF of the light in the optical path.

[00319] As exemplified in FIG. 13, each ring is connected using a pair of gears to the shaft of a stepper motor, forming part of the control system 804. The stepper motor may be fixed on a 3D printed mount fixed on to the lens tube connecting the iris.

[00320] The steppers are connected to the controller 802. In some examples, the controller 802 itself is controlled via a graphical user interface (GUI) presented to the operator. For example, it may be controlled through serial port communication (e.g., via communication interface 802c) using a feature rich graphic user interfaced based software module. Using this software module, the stepper motors rotation angles are configured and saved such that during each measurement a single command is passed to the steppers to close and open the iris shutters based on the type of measurement.

[00321] In some examples, a feedback mechanism is implemented using a rotary encoder which determines the angular movement of the stepper. These encoders are attached to the iris using another gear.

[00322] In at least one example, the calibration mechanism includes a unique algorithm where first the stepper is rotated in a particular direction in which iris is 100% open and wherever it stops rotating, the code records the position and saves this position as a homing position. Then the stepper rotates in the opposite direction and wherever it stops, that angle is recorded as the 2^nd homing position. Using simple arithmetic the total steps needed to fully open and fully close the iris is determined. After this calibration an accurate partial opening of the iris is possible allowing partial light entry into the optical path of the system.

(ii) Variable Focus Control System (806)

[00323] Variable focus control system 806 may allow switching between a laser and visible focal spot. In some examples, the feature is used to accurately record the correct focal position of the reflective objective for laser and the broad band light source. Since the focal position of any lens or a focusing mirror depends on the wavelength of light, therefore, during phase switching mode, the reflective objective position is different from the objective position in the imaging mode.

[00324] Thus, for situations when it is required to view and isolate the region of interest on the sample for switching, a mechanism to switch between the two focused positions of the objective quickly and accurately is desired. In some examples, this is implemented using a stepper and gear assembly coupled to the GUI based software through the controller 802 capable of accepting serial commands from the desktop user interface and relay the equivalent machine level instructions to the stepper motor.

[00325] The GUI interface allows recording and saving the two positions of the stepper motor and thus imparts a memory to the system allowing reversible switching between the two positions without disturbing the system alignment. During manual focusing, repeatable focal positions cannot be achieved. Furthermore, every time the varifocal zoom housing is touched to vary the objective position the laser spot position changes thus causing a disturbance in the beam alignment on the sample. And finally with this feature, a significant amount of time is saved.

(iii) Laser Pulse Width Control System (806)

[00326] A complete automation over the laser delivery mechanism on the sample may be needed to implement the feature of static testing. This specific feature, as described above, involves the creation of a matrix with power varying in one axis and the pulse width on the other axis. Such a capability to scan or sweep all the laser parameters to precisely determine the right laser parameters to achieve reversible phase switching is the primary goal.

[00327] Thus, a control of the pulse width is the first part, which may be realized through a motorized rotation of the knob responsible to vary the pulse width of the laser pulse, e.g., in 16 discreet steps from 6 ns to 129 ns. This knob which is present at the rear end of the nanosecond pulsed laser module of Thorlabs™ is attached to the shaft of a stepper motor.

[00328] In at least one example, the stepper is mounted and fixed to the body of the laser 318 using a 3D printed assembly which statically holds the motor in place such that the shaft having a 1.5 mm size flat head sits onto the screw slot of the rotatable knob.

[00329] The stepper may be fully controlled through the GUI via a controller capable of accepting serial commands from the desktop installed software user interface. This user interface is designed to switch between different pulse width as well as store the last known value of the pulse width selected on the pulsed laser module.

(iv) Laser Power Control System (810)

[00330] In some examples, the system also includes a power controller, and is used for static testing feature. For this aspect, a stepper motor is mounted and installed near the continuously variable filter wheel 716 (FIG. 7A) which is present in the optical path of the laser.

[00331] A rotary encoder may also couple the gear on the filter wheel 716 thus incorporating a feedback mechanism allowing accurate rotation of the filter wheel. A detailed design of the filter wheel attached to stepper and rotary encoder can be seen in FIG. 13(e)-(f). This stepper similar to previous control mechanism, is also controlled using the desktop-based GUI through the controller 802.

[00332] The GUI is programmed to calibrate the position of the filters wheel and can remember the last position of the wheel. Apart from recording the last known position of the filter wheel, the user interface can also accurately rotate the filter wheel leading to a precise control of the power attenuation and thus can linearly increase or decrease the energy delivered to the sample.

(v) Camera Control System (812)

[00333] A camera controller may be included such as to enable not only viewing a live image feed of the sample, but also programmatically take reflection or transmission mode snapshots of the sample and store them. This component is used extensively in the static testing module to capture the image of each laser scanned square, to store a record of the sample view for both reflection and transmission modes.

(vi) Repetition Rate Control System (814)

[00334] Another important aspect of laser scanning of sample and static testing is the speed of stage movement or the repetition rate of the pulsed laser. The repetition rate is the frequency of the pulsed laser. It determines the minimum space between subsequent laser pulses. For the pulsed laser module which has been used in the experimental setup, the maximum repetition rate possible as per the specification sheet is 50 kHz, which means the laser pulses are separated by 20 ps.

[00335] In some examples, this component is controlled using a function generator which is in turn connected to the desktop installed user interface through serial port communication capable of sending well known commands to control the amplitude, waveform, and frequency. The GUI provides a configuration page to connect to the instrument and set an amplitude of 1 VPP and a frequency of 50 kHz.

(vii) Spectrum Control System (816)

[00336] A spectrum controller provides a framework to constantly measure the reflection and transmission spectrum from the sample. To achieve this two spectrometers are integrated to the system. The same user interface described previously is used to connect to the two spectrometers.

[00337] A configuration page is provided to configure the two spectrometers for both reflection and transmission measurements. This mainly involves the capability to acquire light and dark spectrum which can be saved along with integration time and averaging such that even if the software restarts the saved calibration gets loaded back in the software.

[00338] Using the light and dark save spectrum, the user interface may be programmed to display live spectrum acquisition. Thus this module is designed to interact with the shutter control module to close the right shutters for reflection and transmission measurements thus allowing automated reflection and transmission measurements which is one of the main goal for the static testing work flow.

(viii) Stage Motion Control System (818)

[00339] As discussed above, there may be a single-axis or dual-axis translational stage controller for controlling the stage positioning. This may also include stepper motors, and sensors (e.g., rotary encoders).

XIII. STATIC TEST MATRIX ON SAMPLE

[00340] Using the control system 800 exemplified in FIG. 8, the broadband dynamic testing system 300 may be controlled to produce a matrix of square patterns on the sample 150, which is also known as static test matrix. This matrix is basically an effective sweep of all laser parameters where each square in the matrix is generated with a specific laser pulse energy.

[00341] This matrix square exemplified in FIG. 14, which shows different portions of a sample 150 with different squares 1450. Each square 1450 is produced by rastering the sample with a laser pulse have varying pulse width and power. The purpose is to vary the optical features of the sample with different pulse energies and powers. In other examples, the matrix is not necessarily formed of square shapes, and any other suitable shape may be used for the rastered portions 1450.

[00342] Once the sample is rastered with various rastered portions 1450, they may be tested for their reflective and transmissive properties. This allows testing the sample behavior under different laser conditions, which can assist in understanding sample behavior (e.g., sample optical switching properties under different laser conditions). This, in turn, allows for the system to be used for dynamic testing of the sample under different laser conditions.

(i) Process for Generating Static Matrix

[00343] To produce a static matrix on a sample, the squares are produced first turning on the laser beam of laser 318, and moving the dual-axis stage back and forth while simultaneously also moving in an orthogonal direction in very small increments thus creating a rastered square shaped pattern of dimensions (e.g., of more than 30 pm x 30 pm) and then turning OFF the beam. Thus, between each spot the beam is switched OFF.

[00344] The main purpose of the matrix to vary the pulse width in a direction and power in orthogonal direction while keeping same repetition rate and deliver an array of pulse energies and measure the change in reflection and transmission.

[00345] A GUI can provide a configuration page for configuring the matrix size and the dimensions of each square and speed with which each square would be created can also be configured. The user may control the range of pulse width and power that need to be scanned during the static testing matrix creation.

[00346] Before starting the testing, it may be ensured that the laser 318 is perfectly focused and aligned onto the sample 150 and the beam is at the right position such that at the end of a single raster the scanned spot should cover the aperture on the parabolic mirror. This would ensure that the spectrum controller 816 would effectively capture the scanned spot and not the as-deposited region of the sample.

[00347] In some examples, the spectrometers are calibrated and checked and the sample is in focus. Apart from this, the filter wheel 716 (FIG. 7A) may be reset to the no filter zone. Finally, when the process is initiated, the dual axis stage automatically starts by switching the laser beam at full power and draws a signature pattern and switch off the beam. This signature pattern is mainly required to identify the direction and orientation of the start of start of static testing.

[00348] After this, first the pulse width controller 808 may set the pulse width to the start value of the pulse width in the matrix. After the pulse width is selected, the power is set to the first optical density (OD) value of the matrix following the laser beam is switch ON and the first square pattern is generated by the dual-axis stage movement.

[00349] When finished the laser beam is switched OFF and the power controller is set to the next optical density value which rotates the filter wheel 716 to the next higher OD position. Then the beam is switch ON again and using stage controller 2^nd square patterned is generated with different laser pulse energy.

[00350] This continues until the end of the OD list is reached after which the pulse width controller sets the next pulse width value, and the power is set to the first OD value of the matrix. This process continues until all the set pulse width and OD values value been scanned and for each square a reflection, transmission spectra is created and saved along with the metadata files which consists of the laser beam parameters, such as unattenuated average power of the beam at that pulse width, and repetition rate, delivered peak power, and delivered pulse energy. The generated database is then viewed and analyzed.

[00351] FIG. 14 shows an example process flow for a method 1400 for generating and testing a static matrix on a sample. In some examples, method 1400 is performed using a processor of the controller 802 (FIG. 8). Method 1400 may be automated using the appropriate control system in FIG. 8, although not explicitly described as such.

[00352] As shown, at 1402 the process is initiated. At 1404, one or more laser settings are initialized for the laser 318 (e.g., frequency, pulse width and max power peak). These can be adjusted via the pulse width control system 808 and power control system 810.

[00353] At 1406, the laser 318 is operated to raster an area of the sample 150, such as to generate a raster portion 1450. In some examples, the raster portion 1450 may have dimensions of 30 pm x 30 m. To that end, the stage motion control system 818 (FIG. 8) may be operated such that the laser 318 can scan the respective raster portion area. In some cases, prior to 1406, the stage motion control system 818 is also initiated to align a correct portion of the sample 150 that is to be rastered.

[00354] At 1408, the transmission and/or reflection spectra of the rastered portion 1450 may be determined. This may be determined in a manner as previously described.

[00355] At 1410, the laser 318 may be paused or turned OFF. In some cases, this may occur prior to act 1408.

[00356] At 1412, the laser power may be reduced, such as by controlling the filter wheel 716 (FIG. 7A) associated with the laser 318 - e.g., via the power control system 810. At 1414, the stage motion control system 818 (FIG. 8) may be operated to translate to a new position along the same matrix row (e.g., a new X position). The laser 318 may be operated again to generate a new raster portion 1450 on the new area of the sample 150. At 1416, the transmission and/or reflection spectra of the new raster portion 1450 is again determined.

[00357] At 1418, a determination is made as to whether the laser power is at a minimum (i.e., an absolute minimum or a predefined desired minimum). For example, this is determined based on the filter wheel 716 settings. If not, the method can return to act 1410 or 1412 and continue to iterate under the determination at 1418 is positive.

[00358] Otherwise, at 1420, the laser settings are modified. This can include incrementing the pulse width, via the pulse width control system 808. The power is then reset to the maximum (e.g., absolute maximum or a predefined desired maximum), via the power control system 810.

[00359] At 1422, it is determined whether the pulse width is at a maximum (e.g. absolute maximum or a predefined desired maximum). If so, the method ends at 1424. Otherwise, at 1426, the stage 152 is repositioned in the Y-axis to generate the next row (using a new pulse width) in the matrix and the X-position is reset to the initial position. This may be done via the stage motion control system 818.

[00360] The method can then return to act 1406 to operate a new raster portion 1450 via the laser 318. The method can continue iterating until the matrix is completed. [00361] It is understood that various aspects of the method 1400 can be varied. For example, rather than increasing power along a given matrix row, the power may be decreased. Likewise, rather than increase pulse width with each new row, the pulse width may be decreased. In other cases, it is not necessary that the system is controlled to generate a grid like matrix. For example, the raster portions 1450 can be arranged in any other suitable shape configuration on the sample 150.

[00362] In some examples, method 1400 is used to perform static testing and measure reflection and transmission spectra across a broad range of wavelengths spanning from l=400nm to 1=1650nm.

(ii) Plotting Measured Reflection, Transmission and Absorption

[00363] Using method 1400, and the acquired reflection and transmission spectra data for each raster portion 1450 - it is possible to plot the variation of reflection, transmission, and absorption at all wavelengths as a function of pulse energy, the exact pulse energy required to achieve both full and partial crystallization can be extracted. This allows selecting a specific laser parameter and producing a large crystallization area on the film and rerunning the static testing on this crystallized area to determine the laser parameters, such as pulse width or peak power required for amorphization. Further analysis may be performed on the data and study the impact of pulse widths with the same pulse energy to deduce various capabilities such as switching speeds.

(iii) Example Test Results

[00364] In at least one example, the above set of steps in method 1400 were performed on a widely known chalcogenide material such as GST, for which the switching speeds and the pulse energies required for switching are already known. Thus, a static test was first performed on a 25 nm GST film to derive the pulse parameters required to achieve full crystallization.

[00365] FIG. 16 shows the reflection, transmission, at various wavelengths (1=1575 nm and 850 nm) as a function of pulse energy in nJ as well as microscope reflection and transmission of the static testing matrix on the sample. It can be observed in the reflection plot at 1=1575 nm that the crystallization begins at 6 nJ, and the film is fully crystallized at 10 nJ of energy. From 6-10 nJ the film attains various partial levels of crystallization which can be seen at difference reflection percent. After 16 nJ the reflection drops and then saturates. In this range, it is possible that the energy is high enough that the material can undergo melting or even ablate.

[00366] Thus, this region is labelled as ablation region. At this point specific laser parameter was selected capable of delivering the desired pulse energy, and a large area was crystallized by setting the laser parameters and scanning a large area of 6mm using the motorized programmable sample stage translational controller module. Another round of static testing was performed on this large, crystallized area to determine the laser parameters for amorphization.

[00367] FIG. 17 shows the reflection, transmission, and absorption plots as a function of pulse energy. It can be observed in the transmission plot that at a pulse energy of 10 nJ, there transmission begins to increase suggestion the onset of amorphization and maximizes until 25 nJ, demarcating the minimum energy required to fully amorphize.

[00368] It is difficult to demarcate the maximum energy after which amorphization stops and ablation starts. To better understand and establish a clear difference between amorphization and ablation region it is thus important to look at the reflection, transmission, and absorption at other wavelengths. Current literature demonstrates 31.2 nJ and 1.25 nJ for crystallization and amorphization respectively for a 70 nm thick GST film. One important thing to note here is the thickness of the film, which is very important, as the volume of material being switched dictates the speed of the switching and would thus shift these values achieved for GST towards higher or lower pulse energy values.

XIV. ENDURANCE MEASUREMENTS

[00369] FIG. 15 shows an example flowchart of a method 1500 for executing an endurance measurement. In some examples, method 1500 is performed using a processor of the controller 802 (FIG. 8). Method 1500 may be automated using the appropriate control system in FIG. 8, although not explicitly described as such.

[00370] At 1502, the process starts. At 1504, the XY translation stage is controlled to position a fresh spot on the sample for laser application, and set it as origin. At 1506, the transmission and reflection spectra are measured and saved. At 1508, one or more laser parameters are set (e.g., laser pulse width, power, repetition rate) for crystallization based on static test results.

[00371] At 1510, the laser 318 is turned ON with preset laser parameters. At 1512, the laser is operated to raster a predefined area of the sample (e.g., 30pm x 30 pm area) to produce crystallized area. At 1514, the laser 318 is turned OFF.

[00372] At 1516, the transmission and reflection spectra are measured, and saved as crystalline. At 1518, the stage is translated to bring the X and Y to the origin. At 1520, the laser settings are set for amorphization based on static test results. At 1522, the laser is turned ON. At 1524, the laser is operated to raster an area (e.g., 30 pm x30 pm area) to produce an amorphous area. At 1526, the laser is turned OFF. At 1528, the transmission and reflection spectra are measured and saved as amorphous.

[00373] At 1522, an implement algorithm is used to compare the change with all previous reflection values at a wavelength of interest.

[00374] At 1530, a determination is made as to whether a trend is identified. If so, at 1526, the results are plotted and saved and the method ends at 1528. Otherwise, the method loops back to 1508.

XV. ELECTRO-OPTIC PROBING FUNCTIONALITY

[00375] The exponential growth in the popularity of silicon photonics has ushered in an era where today's photonic integrated circuit (PIC) chips are highly compact, seamlessly integrating a wide range of photonic components such as optical transceivers and optical processors into a single, densely packed chip.

[00376] This technological evolution has necessitated significant advancements in commercial photonic characterization setups, aiming to facilitate ultrafast and fully automated efficient wafer-level tests. These setups now encompass a broad spectrum of capabilities, including swept wavelength optical measurement solutions, comprehensive wavelength and polarization characterization of optical-to-electrical components, and innovative approaches to wafer and chip-level optical tests for solving polarization alignment issues, among others. Consequently, this sophistication in characterization technologies has precipitated a notable increase in the cost of these instruments, underscoring a trend towards more expensive, yet advanced, photonic research tools.

[00377] However, within the research context, the requirements often diverge significantly from those of commercial production environments. Research labs typically prioritize the exploration of specific phenomena, necessitating extensive modelling and simulation before proceeding to the fabrication of the modelled devices. This process leverages the services of various foundries, which provide the means to produce photonic chips that incorporate a broad array of circuits, tailored to address multiple research scenarios. In this context, the need for characterization setups is fundamentally centred around key functionalities: efficient light coupling, swept wavelength optical measurement, and detailed wavelength and polarization characterization of optical-to-electrical components.

[00378] Recognizing these specific needs, the following pertains to an SiPhonics characterization system. This system may be used alone, or in combination or sub-combination with any other features disclosed herein.

[00379] More broadly, this system is not only designed to address these core functionalities in manual mode but also boasts scalability towards a fully automated measurement setup, offering a versatile and cost-effective solution for advancing photonic research and development. This approach represents a strategic pivot, aligning the capabilities of characterization technologies with the nuanced demands of research environments, thereby facilitating focused, efficient, and innovative exploration within the field of silicon photonics.

[00380] The following section outlines of the specifications that have been incorporated in the design and implementation of the disclosed SiPhonics.

(i) Fast and efficient manual alignment of the grating coupler to input and output fiber

[00381] To conduct effective analysis and determine the responses from integrated photonic circuits on chips, a well-established infrastructure designed for optical interaction with these circuits is required. This interaction involves transmitting input signals as optical modes into the circuit and collecting the processed light for various testing and validation measurements. Achieving this necessitates a design conducive to the quick and accurate alignment of the optical mode from a fiber into a grating coupler (GC), which serves as the primary input and output interface of a typical photonic circuit.

[00382] For thorough characterization of photonic circuits, it's critical to efficiently couple light into and out of the circuit. This process begins with the ability to closely examine the photonic circuit on a display device, using a mechanism that allows for magnification and easy navigation to the circuit's GC components. Subsequent steps involve guiding and aligning a fiber, which carries a well- confined input light mode, onto one of the input GCs. A similar alignment is required for another fiber at the output GC to gather the circuit’s response. Ensuring that both the GC and the optical fiber are visible within the same field of view is essential, as it facilitates efficient light coupling.

[00383] In some examples, the fiber is mounted on a specialized holder designed for precise angling relative to the GCs normal, optimizing light coupling. The mount securing the fiber may offer three degrees of freedom for adjustment: it must allow movement in the X- and Y- directions with micrometer accuracy and enable rotation of the fiber up to 1 -degree precision. This adjustability grants the fine control necessary to perfect the angle at which the fiber interfaces with the GC.

[00384] Finally, an integral part of device characterization involves the efficient extraction of light from the chip. Once successfully coupled out, the light may be directed to an optical spectral analyzer. This crucial step allows for the detailed characterization of the device's properties, facilitating a deeper understanding of how light behaves and interacts with the photonic structures. Such insights are invaluable for making further adjustments or conducting in-depth analysis, ensuring accurate assessment of the integrated photonic circuits.

[00385] The system allows quickly moving from one device to another within minimal time. This should be done via the implementation of a motorized sample stage which can be later programmed to have programmable device. (ii) Measure and record optical response over a desired range of wavelengths with a resolution of 1 pm

[00386] The capability to measure and record the optical response over a specific range of wavelengths with a resolution of 1 picometer (pm) is a critical feature for in-depth analysis in optical engineering and photonics research. This process, often referred to as swept wavelength measurement, enables precise evaluation of the frequency response of optical components, particularly within the C and L bands that are crucial for telecommunications applications.

[00387] To conduct these measurements, in some examples, the system provides the ability to specify the start and end wavelengths of interest, allowing for targeted analysis over a defined spectral range. This is particularly important for components operating within the C band (approximately 1530 to 1565 nm) and the L band (approximately 1565 to 1625 nm), where the telecommunications industry demands high precision due to the dense wavelength division multiplexing (DWDM) technologies employed.

[00388] Once the wavelength range is set, the measurement is initiated using an optical spectral analyzer, a sophisticated instrument capable of discerning the optical power present at each wavelength within the specified range.

[00389] The key to this process is the analyzer's resolution of 1 pm, which allows for the detection of extremely fine variations in the optical response. This high resolution is essential for identifying narrow spectral features, assessing the performance of filters, lasers, and other photonic devices, and ensuring that these components meet the stringent specifications required for their intended use.

[00390] The data recorded from these measurements provides insights into the optical characteristics of the device under test. It can reveal details about the wavelength dependence of loss, gain, and reflective properties, among other parameters. This information is crucial for the design, development, and quality assurance of optical components and systems, particularly those used in fiber optic communications where performance at specific wavelengths directly impacts the overall system efficiency and bandwidth capacity. [00391] By offering the ability to perform swept wavelength measurements with a resolution of 1 pm, researchers and engineers are equipped with a powerful tool for advancing the field of optical telecommunications, enabling the development of more efficient, reliable, and higher-capacity communication networks.

(iii) Capability to scan all power pulse levels and generate a map of various types of transmission as a function of voltage amplitude levels and pulse widths

[00392] In at least one example, the system designed to dynamically adjust both the amplitude and pulse width of voltage or current pulses delivered by a pulse generator through high-quality probes to a specific device on a chip.

[00393] The objective is to assess the effects of these adjustments on signal transmission through a photonic device at a predetermined operational wavelength. This functionality is crucial for identifying the optimal operating conditions, understanding the device's limitations, and determining the necessary power levels to toggle between two phases of the chalcogenide material on the chip. Moreover, this feature is invaluable for exploring the operating conditions of various tunable material platforms that depend on voltage driving conditions. In some examples, the system supports frequencies up to 6-10 GHz.

[00394] The system may offer flexibility to select a specific wavelength for operation. This involves tuning the laser to this wavelength while monitoring the peak through an optical spectral analyzer, with the peak’s current position displayed on the graphical user interface (GUI). Once the operational wavelength is set, a connection may be established between the probes on the provided contact pads on the sample to the pulse generator and oscilloscope.

[00395] The oscilloscope may be configured with capturing each pulse programmed on the pulse generator, recording the corresponding pulse, and saving this data. The oscilloscope may also measure the current induced by the pulse in the circuit, display this measurement, and save the data. In some examples, the system may generate a color map plot correlating voltage amplitude and pulse duration with transmission, represented through color, alongside another plot depicting the current in color. [00396] Additionally, the system may allow for similar sweeps using current pulses, generating color maps for these parameters. A DC bias voltage may be selectively applied across the device as a baseline and conduct sweeps over a range of amplitudes and pulse durations.

[00397] Through transmission map analysis, the system can help determine the photonic device's ideal operating conditions, including optimal power levels and pulse widths for different uses. It will also pinpoint critical thresholds for power and pulse width to avoid device damage or signal integrity compromise. This specification emphasizes a holistic strategy for boosting device performance, reliability, and utility by offering detailed control and analysis of optical pulse parameters.

(iv) Ability to repeatedly switch between two phases of chalcogenide on the photonic circuit and record the switching endurance of the device

[00398] In some examples, the system is proficient in facilitating and documenting the repetitive transitions between two phases of chalcogenide material within a photonic circuit, specifically focusing on the device's capability to endure numerous switching cycles.

[00399] Such a system feature is pivotal for evaluating the robustness and longevity of photonic devices employing phase-change materials (PCMs) like chalcogenides, which are foundational for the functionality of adaptable photonic circuits, persistent photonic storage, and optical switching mechanisms.

[00400] Chalcogenides are known for their ability to adopt various structural phases, predominantly amorphous and crystalline, each characterized by unique optical and electrical attributes. The transition between these phases is triggered by external stimuli — heat, light, or electrical current — prompting a structural modification in the material that alters its refractive index and absorption coefficient. This change is reversible, permitting the material to oscillate between states under regulated conditions.

[00401] Building on the features disclosed above, in at least one example, the disclosed system may precisely define the voltage and current levels, along with the pulse durations necessary for reversible phase transitions within the device. [00402] Moreover, the system may allow selecting specific pulse amplitude and duration settings for both amorphization and crystallization, programming the pulse generator to cycle through these phases while concurrently monitoring the waveguide's transmission. In at least one example, the system is able to archive each voltage pulse emitted from the generator, the resultant current pulse from the circuit's voltage drop, and the transition peak at the operational wavelength.

[00403] Additionally, in some examples, the system provides real-time plotting capabilities for all pulsed data alongside the transmission. In these live transmission plots, the transmission variation as a function of the switching cycle between the two phases may be clearly presented. Consequently, the system can execute repeated phase transition cycles, thereby assessing the device's switching endurance by counting the number of successful transitions between the amorphous and crystalline states before encountering failure or notable performance decline. This data is instrumental in gauging the device's dependability and in pinpointing potential failure modes.

[00404] Assessing the switching endurance of chalcogenide-based devices is crucial for their incorporation into reconfigurable photonic circuits and optical data storage technologies. Devices with high endurance are deemed reliable over their expected operational lifespan, rendering them viable for both commercial and industrial usage where durability and consistent performance are crucial. This system feature emphasizes the imperative for sophisticated testing facilities capable of replicating real- world operational stresses, thus offering deep insights into the device's functional integrity and resilience.

(v) Recording speed of switching by the incorporation of ultrafast oscilloscope in the range of 6 GHz

[00405] In some examples, the disclosed system is equipped to document the switching speeds critical for applications requiring high-speed modulation, through the integration of an ultrafast oscilloscope (e.g., with capabilities up to 6 GHz).

[00406] The imperative for this feature arises from the significant variance in switching speeds attributed to different chalcogenide materials; for instance, Germanium Antimony Telluride demonstrates switching speeds ranging from several picoseconds to femtoseconds, contrasting markedly with other materials exhibiting considerably slower speeds.

[00407] Therefore, in at least one example, the designed system possess the capability to accurately measure the rise and fall times of the light output emanating from the device. This functionality complements the previously established capability of the system to facilitate connections between the sample's contact pads and RF probes, alongside a high-frequency pulse generator and oscilloscope.

[00408] By deploying short pulses to toggle between amorphous and crystalline states in specific arms of a balanced or unbalanced Mach-Zehnder interferometer, the light output is then converted into an electrical signal via an InGaAs photodetector. This signal is subsequently relayed to the 6GHz oscilloscope, enabling the isolation of rise times pertinent to both the detector and the device itself. This methodology allows for the extraction and quantification of the devices' switching speeds, underscoring the system's comprehensive design to address the nuances of high-speed modulation applications.

XVI. DESIGN OF ELECTRO-OPTIC PROBING FEATURE

[00409] The following is a design for an electro-optic probing feature that can be used by itself, or any combination or sub-combinations with other features disclosed herein.

(i) General Design Configuration

[00410] In at least one example, the design of the electro-probing feature enables an accurate mechanical micro positioning. More generally, a micro positioning system is provided that enables precise adjustment of the fiber atop a designated grating coupler on the photonic chip. The micro positioning system facilitates movement of the fiber V groove array, carrying input and output light onto the chip, not only in X, Y, and Z directions but also allowing rotation in two planes.

[00411] In some examples, the micro positioning system is complemented by an optical probing system capable of magnifying the grating couplers and displaying them, along with a single input fiber core carrying the input light, within a single field of view. The optical system provides an enlarged view of the grating coupler on the photonic chip from the top perspective. A grating coupler (GC) may then be positioned around a mark on the top camera view. Subsequently, utilizing the bottom SWIR camera, transparent to the silicon substrates, the same GC is brought into focus, ensuring visibility both at the top and bottom cameras.

[00412] Once the GC is positioned, the fiber V groove array is incrementally introduced into the field of view using the mechanical micro positioning system. As one of the fibers in the V groove, carrying an NIR laser, enters the field of view, it appears on the bottom camera where the GC coupler is already visible, allowing light coupling into the photonic circuit via the GC.

[00413] The chip design allows that the input and output GCs to be separated by a precise distance (e.g., of 200um), matching the spacing between adjacent fibers on the V groove array. Consequently, one fiber on the array can serve as input, while the adjacent fiber couples to the output light.

[00414] Subsequently, the user can activate the optical spectral analyser and connect the output fiber. Using the micro positioners, the laser is precisely aligned with the GC coupler to maximize output. This alignment process is crucial as it's the sole method to guide the user towards achieving optimized coupling by scanning X, Y, and Z positions. Additionally, the angle of incidence of the fiber can be controlled using a servo motor system, with the fiber V groove attached to the servo motor shaft, allowing rotation between -180 to +180 degrees.

[00415] In at least one example, the system includes the following subsystem:

[00416] fa) Mechanical Subsystem

[00417] This encompasses all aspects related to the physical structure and movement mechanisms involved in the system. It includes the design of precise micro positioning systems, such as motors, gears, and actuators, necessary for adjusting the position of components like fibers and couplers with accuracy in multiple directions. [00418] (b) Optical Subsystem

[00419] This category relates to the integration of optical elements, including interfacing with an optical probe station equipped to present a magnified image of the photonic chip. This station offers a 150X magnification view from below, providing a closer perspective, along with a 75X magnification view from above, offering an aerial overview of the chip. Additionally, this section involves integrating a slanted camera and additional cob LED lighting to enhance illumination.

[00420] (c) Software and Electronic Subsystem

[00421] The architectural design for integrating software and electronic components involves coordinating their incorporation into the system framework. This encompasses a graphical user interface (GUI) designed for a dual-monitor setup. One monitor is situated inside an enclosure housing the alignment system. This GUI is programmed to showcase live camera feeds from four different sources, including three web cameras or CMOS cameras and one SWIR camera, displaying views from the top, bottom, and two slanted angles from cameras placed at right angles to each other. The second monitor can be configured to connect to a variety of instruments such as a 6 GHz Oscilloscope, Anritsu™ Optical Spectral Analyzer, and an external cavity laser for sweeping wavelengths with a resolution of 1pm within the C-band of the telecom wavelength range. It is utilized for configuration and measurements. Thus, the primary monitor is optimized to assist the user in achieving high coupling to the device on the chip, while the second monitor facilitates configuration and semi-automated measurements.

(ii) Mechanical Subsystem

[00422] FIG. 18 exemplifies mechanical configuration of the measurement setup. The illustrated setup is an extension of the configuration exemplified in FIG. 12.

[00423] As shown in FIG. 18(a), the sample stage 152 can be adapted by attaching a removable component. In some examples, this removable component plays a crucial role in precisely positioning the fiber V groove over the photonic chip. [00424] As shown, the removable components includes translational stages. In some examples, the translational stages are combined to achieve translational freedom of in the X, Y and Z directions (e.g., 18 mm in each direction).

[00425] Emerging from the Z stage is an L bracket 1802, to which a continuous rotation stage 152 is affixed (see FIG. 18(b)). In some examples, this continuous rotation stage 152 is managed by a micrometer control, facilitating the translation motion of the micrometer screw into the rotation of the stage through worm gears. Another L bracket 1804 is coupled to the stage 1202, which in turn is coupled to the V groove array 1806 via a motor (e.g., a servo motor) (FIG. 18(e)).

[00426] The rotation of the stage 1202 enables precise control of the yaw of the V groove, thereby controlling the height of the corners of the V groove chip. The servo motor governs the pitch and consequently regulates the angle of incidence of light to the grating couplers on the chip 1808.

[00427] FIGs. 18 (e)-(f) illustrate the concept of positioning a V groove on the chip and the components typically found in a photonic chip. The primary input and output of the photonic integrated circuit are the grating couplers, which facilitate the coupling of light from the fiber V groove array's output port and into the chip's ports. It's imperative to maintain equal distances between the input and output grating couplers and the input and output ports of the fiber V groove array.

(iii) Optical Subsystem

[00428] The optical subsystem comprises two primary components for viewing samples from both the top and bottom. With the top viewing configuration, samples are illuminated from above (epiillumination) and captured using a low-magnification objective on a CMOS camera.

[00429] In some examples, the optical subsystem offers a 5X magnification, providing a broad field of view that encompasses both input and output grating couplers in a single image. Conversely, the bottom viewing setup uses a 20X NIR objective and a SWIR camera to collect light that passes through the sample. This method is effective because materials like single silicon are transparent to NIR wavelengths, allowing for clear transmission imaging.

[00430] FIG. 19 exemplifies the optical path that enables viewing of the sample and guides the laser spot towards the input grating coupler, aiming for the highest possible coupling efficiency. This pathway is significant for waveguide measurements. It illustrates the dual functionality of the setup, enabling top-view epi-illumination and bottom-view transmission imaging of the sample.

[00431] The optical configuration incorporates Kohler illumination. As shown, an illumination source 1902 (e.g., a tungsten lamp) generates light which follows optical path 1950. The illuminated light is collimated and focused through two aspheric lenses 190 (e.g., each with a 20 mm focal length), onto an iris 1906.

[00432] The light is then recollimated and directed by lens 1908 through a beam splitter 1910 (e.g., a pellicle beam splitter). In some examples, the beam splitter 1920 has a reflectance-to- transmittance ratio of 8:92 in the visible wavelength range. This setup ensures that 92% of the light is transmitted, focused by a parabolic mirror 1912, and finally collected by an objective lens 1914 (e.g., a 5X NIR objective) that illuminates the sample 150. Reflected light from the sample 150 is then partly redirected by the beam splitter 1910 to the imaging sensor 1916 (e.g., CMOS camera) via a lens 1918, forming an image of the sample.

[00433] In at least one example, a slanted objective 1916 (e.g., 10X objective) is included to assist in observing the illumination spot and guiding electrical probes within the 5X objective’s 1914 view.

[00434] To effectively work around the obstruction caused by the fiber V-groove array 1918 on top of the sample, a user map map a visible point from the CMOS camera's top view to a corresponding point in the SWIR camera's view 1920. This is achieved by first locating an alignment mark on the sample with the CMOS camera. These metallic marks, reflective and opaque to light, are clearly visible in epi-illumination but appear dark in the transmission image captured by the SWIR camera 1920. Mapping these points allows users to maintain accurate laser targeting.

[00435] Once mapping is complete, a user can navigate the chip to measure any photonic circuit, positioning the input grating coupler within the CMOS camera's view, directly beneath the annotation mark. This ensures the annotation mark on the SWIR camera view aligns with the input grating coupler. When the laser, connected via SMF patch cables and FC connectors, is activated, its transmission through the sample is captured by the SWIR camera, even if the fiber V-groove array blocks the CMOS camera's view.

[00436] Adjustments to precisely position the V-groove and laser spot are made using the PT stage's Z translation and a servo motor programmed, e.g., to rotate to 8 degrees. This fine-tuning, along with continuous measurement and wavelength synchronization by the Optical Spectral Analyzer (OSA), ensures optimal light coupling into the photonic structures for accurate measurements and analysis.

[00437] In an experimental test, after successfully achieving strong coupling, the responses from several Mach-Zehnder modulator (MZM) circuits were recorded. This was accomplished by sweeping the wavelengths from 1540nm to 1560nm with a resolution of 1pm and noting the peak power at each wavelength. It was seen that the measured responses closely match the Finite-Difference Time-Domain (FDTD) simulated responses of both the single and dual-arm MZMs. The measurements on a photonic chip fabricated by ANT were tested, featuring circuits with both input and output grating couplers. Two devices were evaluated: one single-arm MZM and one dual-arm MZM. In conclusion, our in-house built measurement setup has proven to be fully capable of accurately characterizing photonic chips. This setup has the full potential to be scaled up.

(iv) Electronic and Software Subsystem

[00438] Once the system is optically aligned and fine-tuned for maximum coupling efficiency, as confirmed by wavelength sweep measurements, the introduction of electrical probing at specific points on the sample is the subsequent step.

[00439] At this step, the focus is on chalcogenide integrated Mach-Zehnder modulators (MZMs), where a precise segment of chalcogenide material is positioned atop a waveguide and covered with a thin layer of an ITO-based nanoheater. This nanoheater contacts a gold pad measuring 100x100pm, which is the target site for positioning electrical probes. Applying a specific voltage heats the nanoheater through Joule heating, transitioning the chalcogenide between its crystalline and amorphous states. This phase change in one arm of the MZM induces a full PI phase shift, modulating the MZM's response. [00440] Characterizing the device's stability and operational speed necessitates a semiautomated system capable of determining the required voltage and the minimum pulse widths needed for reversible switching between the two phases. The switching process involves applying pulsed voltage, necessitating knowledge of both the amplitude and duration of the pulse.

[00441] To facilitate this, the system includes a software with a dual-monitor GUI interface for capturing video feeds from three cameras. In at least one example, the software’s design allows one monitor (the Live Feed monitor) to display four viewports, each configurable to a specific camera type, including CMOS, web, and SWIR cameras. The second monitor (the Configuration monitor) opens a window dedicated to connecting and setting up various peripheral instruments controlled via the software, currently featuring four configuration tabs.

[00442] The first tab connects to a tunable laser and an optical spectral analyzer (OSA). Users input the GPIB addresses for these instruments and define operating parameters like the wavelength range. Initiating a measurement sets the laser to a predetermined wavelength and activates the OSA's peak search feature. Upon identifying a peak, the software displays the peak power and wavelength on a live plot within this tab.

[00443] The second tab also called IV Sweeps tab is dedicated to electrical static testing, allowing connection to a pulse generator and a 6GHz Oscilloscope. The pulse generator, set to software trigger mode, sweeps through selected voltage amplitudes and pulse durations. It simultaneously measures the transmission through the device at a chosen operational wavelength, displaying results as a color map plot of transmission versus pulse duration and amplitude. Additionally, the current through the device under test is recorded and saved for each pulse, aiding in comprehensive device evaluation. The transmission is recorded by the software using the peak search feature of the OSA.

[00444] The third tab, also known as the endurance tab, is dedicated to assessing the switching endurance of the device under test. After conducting static testing and analyzing the data, the user identifies the two critical voltage pulse parameters: amplitude and pulse duration, necessary for switching between the amorphous and crystalline phases, which result in distinct transmission levels. Within this tab, the user inputs these parameters, which are then repeatedly applied to the pulse generator. The system records the transmission through the device at the selected operational wavelength for each switching cycle, potentially repeating this process millions of times. The collected data for each cycle are saved, and a live plot viewer displays both the transmission data and the applied voltage and current pulses. This setup enables users to ascertain the maximum number of switching cycles the device can undergo before it ceases to exhibit reversible switching behavior.

[00445] The fourth tab as shown in FIG. 21 is specifically designed for two purposes: to measure the switching speed of the device and to observe changes in transmission without actual switching. To assess the switching speeds, the system utilizes an InGaAs photodetector connected to the device's output. The oscilloscope records the rise and fall times of the light signal, which are crucial for determining switching speeds. The software, interfaced with a 6GHz oscilloscope, calculates the device's switching speed by taking the overall rise and fall times and subtracting the known rise and fall times of the photodetector.

[00446] Additionally, this tab enables the study of transmission changes in the device that are induced thermally, rather than through actual switching. This functionality underscores the significant thermo-optic coefficient of the chalcogenide materials used in the devices. By applying a voltage pulse of amplitude lower than the switching voltage and simultaneously recording the transmission changes via the oscilloscope, the software captures the signal changes prompted by the photodetector. The transmission should return to its baseline at the pulse's conclusion, illustrating the large thermo-optic effect in chalcogenide films. This effect causes a shift in the refractive index of the material, leading to alterations in the MZM resonances which, in turn, affects the transmission at the operating wavelength. The system records the current through the photodetector and observes the voltage changes across it, which should revert to the initial state post-pulse, demonstrating the material's properties and its impact on device functionality.

XVII. INTERPRETATION

[00447] Various systems or methods have been described to provide an example of an embodiment of the claimed subject matter. No embodiment described limits any claimed subject matter and any claimed subject matter may cover methods or systems that differ from those described below. The claimed subject matter is not limited to systems or methods having all of the features of any one system or method described below or to features common to multiple or all of the apparatuses or methods described below. It is possible that a system or method described is not an embodiment that is recited in any claimed subject matter. Any subject matter disclosed in a system or method described that is not claimed in this document may be the subject matter of another protective instrument, for example, a continuing patent application, and the applicants, inventors or owners do not intend to abandon, disclaim or dedicate to the public any such subject matter by its disclosure in this document.

[00448] Furthermore, it will be appreciated that for simplicity and clarity of illustration, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements. In addition, numerous specific details are set forth in order to provide a thorough understanding of the embodiments described herein. However, it will be understood by those of ordinary skill in the art that the embodiments described herein may be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the embodiments described herein. Also, the description is not to be considered as limiting the scope of the embodiments described herein.

[00449] It should also be noted that the terms “coupled” or “coupling” as used herein can have several different meanings depending in the context in which these terms are used. For example, the terms coupled or coupling may be used to indicate that an element or device can electrically, optically, or wirelessly send data to another element or device as well as receive data from another element or device. As used herein, two or more components are said to be “coupled”, or “connected” where the parts are joined or operate together either directly or indirectly (i.e., through one or more intermediate components), so long as a link occurs. As used herein and in the claims, two or more parts are said to be “directly coupled”, or “directly connected”, where the parts are joined or operate together without intervening intermediate components.

[00450] It should be noted that terms of degree such as "substantially", "about" and "approximately" as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree may also be construed as including a deviation of the modified term if this deviation would not negate the meaning of the term it modifies.

[00451] Furthermore, any recitation of numerical ranges by endpoints herein includes all numbers and fractions subsumed within that range (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.90, 4, and 5). It is also to be understood that all numbers and fractions thereof are presumed to be modified by the term "about" which means a variation of up to a certain amount of the number to which reference is being made if the end result is not significantly changed.

[00452] It should also be noted that there may be some elements that are used to implement at least part of one of the embodiments described herein that may be implemented via software that is written in a high-level computer programming language such as object oriented programming or script-based programming. Accordingly, the program code may be written in Java, Swift/Objective- C, C, C++, Javascript, Python, SQL or any other suitable programming language and may comprise modules or classes, as is known to those skilled in object oriented programming. Alternatively, or in addition thereto, some of these elements implemented via software may be written in assembly language, machine language or firmware as needed. In either case, the language may be a compiled or interpreted language.

[00453] At least some of these software programs may be stored on a storage media (e.g. a computer readable medium such as, but not limited to, ROM, magnetic disk, optical disc) or a device that is readable by a general or special purpose programmable device. The software program code, when read by the programmable device, configures the programmable device to operate in a new, specific and predefined manner in order to perform at least one of the methods described herein.

[00454] Furthermore, at least some of the programs associated with the systems and methods of the embodiments described herein may be capable of being distributed in a computer program product comprising a computer readable medium that bears computer usable instructions for one or more processors. The medium may be provided in various forms, including non-transitory forms such as, but not limited to, one or more diskettes, compact disks, tapes, chips, and magnetic and electronic storage. The computer program product may also be distributed in an over-the-air or wireless manner, using a wireless data connection. [00455] The term “software application” or “application” refers to computer-executable instructions, particularly computer-executable instructions stored in a non-transitory medium, such as a non-volatile memory, and executed by a computer processor. The computer processor, when executing the instructions, may receive inputs and transmit outputs to any of a variety of input or output devices to which it is coupled. Software applications may include mobile applications or “apps” for use on mobile devices such as smartphones and tablets or other “smart” devices.

[00456] A software application can be, for example, a monolithic software application, built inhouse by the organization and possibly running on custom hardware; a set of interconnected modular subsystems running on similar or diverse hardware; a software-as-a-service application operated remotely by a third party; third party software running on outsourced infrastructure, etc. In some cases, a software application also may be less formal, or constructed in ad hoc fashion, such as a programmable spreadsheet document that has been modified to perform computations for the organization’s needs.

[00457] Software applications may be deployed to and installed on a computing device on which it is to operate. Depending on the nature of the operating system and/or platform of the computing device, an application may be deployed directly to the computing device, and/or the application may be downloaded from an application marketplace. For example, user of the user device may download the application through an app store such as the Apple App Store™ or Google™ Play™.

[00458] The present invention has been described here by way of example only, while numerous specific details are set forth herein in order to provide a thorough understanding of the exemplary embodiments described herein. However, it will be understood by those of ordinary skill in the art that these embodiments may, in some cases, be practiced without these specific details. In other instances, well-known methods, procedures and components have not been described in detail so as not to obscure the description of the embodiments. Various modification and variations may be made to these exemplary embodiments without departing from the spirit and scope of the invention, which is limited only by the appended claims.

Claims

CLAIMS:

1. A broadband dynamic testing system, comprising: a sample stage configured to hold a sample for testing; an inverted microscope optical assembly, comprising (i) a light source input port, (ii) a sample observation port, (iii) an imaging output port, and (iv) a binocular output port; one or more of: a reflection source optical assembly, comprising a first broadband light source for measuring light reflection properties of the sample, wherein the reflection optical assembly comprises an output port coupled to the light source input port; and a transmission source optical assembly, comprising a second broadband light source for measuring light transmission properties of the sample, wherein the transmission source optical assembly includes an output port aligned over an opposite side of the sample from the sample observation port; and an observation optical assembly, configured to magnify an image of a region of interest on the sample and enabling at least one of: (i) measurement of the sample properties in the region of interest, and (ii) imaging of the region of interest.

2. The system of claim 1, wherein the sample is a nano-structured or unstructured thin film.

3. The system of claim 2, wherein the region of interest is a nanostructured region.

4. The system of any one of claims 1 to 3, wherein one or more of the first and second broadband light sources comprise halogen lamps.

5. The system of any one of claims 1 to 4, wherein one or more of the optical assemblies comprise an off-axis parabolic (OAP) mirror.

6. The system of claim 5, wherein the reflection source arm further comprises one or more lasers for pump-probe microscopy, wherein the one or more lasers transmit a laser signal along a first light path extending through an aperture formed in the OAP mirror, and the first light source transmits light along a second light path that reflects of a surface of the OAP mirror.

7. The system of any one of claims 1 to 6, wherein the observation arm includes optical components configured to apply a magnification of 10X to an input optical image of the region of interest.

8. The system of claim 7, wherein the system includes a reflective objective lens having a 15X magnification, and the system outputs, from the observation arm, a 150X magnification of the region of interest on the sample.

9. The system of any one of claims 1 to 8, wherein the angle of incidence of light on the sample is less than approximately 15°- 75°.

10. The system of any one of claims 1 to 9, wherein one or more of the reflection and transmission source arms include polarizing elements for measuring reflection and transmission properties, respectively, of the sample at various polarization angles.

11. The system of any one of claims 1 to 10, wherein the transmission source arm further comprises a laser arm portion comprising a laser source.

12. The system of claim 11, wherein the transmission source arm include an OAP, and the laser signal follows a first optical path to the sample stage via a central aperture of the OAP, the light from the second light source follows a second optical path to the sample stage by reflecting of a surface of the OAP.

13. The system of any one of claims 11 or 12, wherein the laser source is used for inducing a reversible transition in optoelectronically reconfigurable materials comprising the sample.

14. The system of any one of claims 1 to 13, further comprising an electro-optic probing system.

15. The system of any one of claims 1 to 14, wherein the reflection source arm is configured with pump-probe measurement capabilities.

16. The system of any one of claims 1 to 15, further comprising a sample stage support system for the sample stage, the support system comprising an automated stage translation mechanism coupled to a motion control mechanism.

17. The system of any one of claims 1 to 16, further comprises a controller coupled to one or more of: a shutter control system, for controlling one or more ring actuated iris diaphragms that control light output from the broadband light sources; a variable focus control system, for controlling switching between a laser and visible focal spot; a laser pulse width control system, for varying a pulse width of a laser pulse from the laser; a laser power control system, for controlling a power of a laser signal from the laser; a camera control system, for programmatically taking reflection or transmission mode snapshots of the sample; a repetition rate control system for controlling a repetition rate of the pulsed laser; a spectrum control system measure the reflection and transmission spectrum; and a stage motion control system for controlling movement of a support stage.

18. The system of any one of claims 1 to 17, wherein the system is used for generating a static matrix on the sample comprising one or more rastered portions, and testing the various rastered portions for reflection and/or transmission properties.

19. The system of any one of claims 1 to 18, being configured for endurance testing of samples.

20. The system of any one of claims 1 to 19, wherein one or more of the optical assemblies is removably coupled to a housing of the inverted microscope optical assembly.

21. The system of any one of claims 1 to 20, wherein sample stage and the reflection and transmission arms are configured for Photonic Integrated Circuit (PIC) measurements, and the system further comprises a further assembly with position translation stages mounted on the sample stage to enable precise alignment of a multichannel fiber v-groove on top of a photonic chip.

22. The system of claim 21, wherein the sample stage is configured for the positioning of electrical probes, enabling optoelectronic measurements on the photonic chip.

22. A kit comprising the sample stage, inverted microscope optical assembly, reflection source optical assembly, transmission source optical assembly and observation optical assembly of any one of claims 1 to 22.