TWI759480B - Optical device fabrication method - Google Patents

Abstract

An optical device fabrication method includes removing semiconductor material from a semiconductor substrate to form a first curved surface and a second curved surface, forming a bonding material on the first curved surface, and selectively removing semiconductor material from at least one of the first and the second curved surfaces to form one or more subwavelength structures. The semiconductor substrate has a bandgap wavelength associated with a bandgap energy of the semiconductor material. The optical device refracts certain incident electromagnetic radiation and/or filters other electromagnetic radiation. The refracted radiation includes infrared wavelengths longer than the bandgap wavelength and the filtered radiation includes wavelengths shorter than the bandgap wavelength.

Description

Method of manufacturing an optical device

This creation is about coupling light using an optical device.

Light propagates in free space, or an optical medium is coupled to a photodetector that converts optical signals into electrical signals for processing.

Embodiments of the present invention relate to optical devices for directing light, processing or detecting electromagnetic radiation. More specifically, the present embodiments relate to the fabrication of optical devices for refraction and/or filtering of predetermined wavelength bands of electromagnetic radiation.

Generally speaking, one aspect of the present invention can be implemented in a method of manufacturing an optical device; the aforementioned method of manufacturing includes: removing semiconductor material from a semiconductor substrate to form a first curved surface and a second curved surface , forming a bonding material on the first curved surface, and selectively removing semiconductor material from the first and second curved surfaces to form one or more sub-wavelength structures. The semiconductor substrate has a bandgap wavelength, which correlates to the bandgap energy of the semiconductor material. Forming the bonding material includes depositing the bonding material on the first curved surface. The second curved surface is formed on the optical device and is opposite to the first curved surface. The size of at least one dimension of the at least primary wavelength structure is smaller than the bandgap wavelength of the semiconductor substrate. Optical device configured to refract electromagnetic radiation having a first wavelength range, and/or filter There is a second wavelength range of electromagnetic radiation; the first wavelength range is infrared wavelengths greater than the bandgap wavelength, and the second wavelength range is less than the bandgap wavelength.

This and other implementations may each include one or more of the following features, as appropriate. The band gap energy of the semiconductor material of the optical device can be 1.2 electron volts to 1.7 electron volts. In some embodiments, the first wavelength range may be from 800 nanometers to 2000 nanometers. In some embodiments, the second wavelength range may be from 400 nm to 800 nm.

The manufacturing method may further include disposing an optical element relative to the bonding layer, and the optical element will receive the electromagnetic radiation refracted by the optical device. The optical element may be an active element configured to adjust the first wavelength range and/or the second wavelength range. Tuning may include absorbing or emitting electromagnetic radiation of wavelengths corresponding to the tuning range. In some implementations, the optical element is selected from the group consisting of a photodetector, a sensor, a light emitting diode, and a laser. In some implementations, the optical element comprises silicon germanium.

This and other implementations may each optionally also include one or more of the following features. One or more structures that can be used to form an optical element are selected from the group consisting of a photodetector, a sensor, a light emitting diode, and a laser.

In some implementations, the bonding layer has an optical thickness corresponding to a focal length of the optical device. The bonding layer can include a bonding material selected from the group consisting of oxides, nitrides and metals. In some implementations, forming the bonding layer further includes planarizing the bonding layer by chemical mechanical polishing.

The second curved surface may have the same radius of curvature as the first curved surface. In some implementations, at least one of the first curved surface and the second curved surface is formed by a grayscale mask.

Removing semiconductor material from the semiconductor substrate may include etching the semiconductor substrate. The one or more sub-wavelength structures can comprise periodically arranged plural sub-wavelength structures.

In some cases, the optical device has an equivalent refractive index that is dynamically adjusted in response to an applied electric field. The optical device may be a lens.

In some implementations, the optical device is a first optical device, and the bonding layer is a first bonding layer, and the aforementioned manufacturing method further includes coupling a second optical device to the first optical device. For example, the second bonding layer can be formed on the second curved surface of the first optical device by depositing a bonding material on the second curved surface, and the second optical device can be coupled to the second bonding layer and opposite the first optical device. The first optical device and the second optical device are configured to collectively refract electromagnetic radiation having a third wavelength range and/or filter electromagnetic radiation having a fourth wavelength range. In some examples, the third wavelength range is a sub-range of the first wavelength range. In some examples, the fourth wavelength range is a sub-range of the second wavelength range.

In some implementations, the second optical device includes at least one curved surface that includes one or more subwavelength structures. The size of the at least primary wavelength structure in one dimension is smaller than the bandgap wavelength of the semiconductor substrate. In some embodiments, the second bonding layer has an optical thickness sufficient to enable the electromagnetic radiation reflected by the first optical device to be focused on the second optical device.

Implementations of the present disclosure provide one or more of the following advantages. Embodiments provide techniques for mass production of semiconductor lenses that can absorb visible and near-infrared radiation compared to conventional glass lenses that are transparent to visible and infrared radiation. of the present invention Lenses of semiconductors can be used to refract and/or absorb electromagnetic radiation having near-infrared or infrared wavelengths. Furthermore, the semiconductor lenses described herein can be fabricated to absorb and/or refract selectively incident electromagnetic radiation. The semiconductor lenses described in this disclosure have a larger refractive index than glass lenses. This larger index of refraction provides the ability to guide, focus or defocus refracted radiation in shorter transmission paths within the optical device.

Furthermore, forming the optical device for refraction and filtering as one optical component can reduce the complexity of integration with other optical components in the optical system. Forming the refractive element for refraction and filtering as an optical component can reduce manufacturing costs. The refractive elements can be formed planarly on the wafer for integration with photonic integrated circuits. By changing the periodic structure of the corresponding refractive elements, multiple refractive elements with different filter ranges can be formed in the same process. The refractive element can be integrated with the active element to adjust the refractive or filtering range of the refractive element.

The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other potential features and advantages will become apparent from the embodiments, drawings and claims.

100, 200, 210, 400, 600, 610, 620, 700, 710, 810: Photonic Integrated Circuits

101, 131a-131e, 201, 211, 501, 503, 511, 513, 521, 531, 601, 621, 631, 701, 711, 801, 811: Refractive elements

103: Surface

105: Periodic Structure

107, 203, 213, 703, 713, 803, 813: Optical Media

111, 209, 219, 221, 421, 423, 427: Light

113: Focus beam

119: External medium

120: Photonic Integrated Circuits

121: Lens part

123: Periodic Structure Section

125: The first group of periodic structures

127: Second group of periodic structures

140: Multilayer Refractive Elements

141, 143, 145, 151, 153, 155: Layers

150: Multilayer Refractive Elements

160: Laminated Refractive Elements

161, 401: The first refractive element

163, 403: Second refractive element

203, 213: Optical Media

204, 214: Covering elements

205: Substrate

207: Active Components

208, 218: Incident light

215: External dielectric components

331, 332, 334: Periodic Structures

301, 303: a-n periodic structure

305: Two-dimensional Periodic Structures

333: Periodic Structure

307:a-n two-dimensional rectangular periodic structure

308, 310: Layer

321:x direction

322: y direction

405: Third Refractive Element

407: Fourth Refractive Element

411: Light with Broadband Signals

500, 503, 510, 520, 530, 633: Optical Components

523, 533: Sidewalls

602, 612, 635: first doped regions

604, 614, 637: second doped regions

616: the third doping region

622: a-n doped region

630: Photonic Integrated Circuits

705, 715, 805, 815: Voltage source

807, 817: Support elements

809, 819: Arrow

902-906, 1000-1008: Steps

1A is a block diagram of an example of an optical device that is part of a photonic integrated circuit.

1B, 1C and 1D show examples of optical devices.

Figure 1E shows an example of a laminated optical element.

2A and 2B show examples of optical arrangements for filtering or concentrating light.

3A-3D illustrate examples of substructures.

Figure 4 shows an example of a photonic integrated circuit with optical means for filtering light of different wavelengths.

5A-5D illustrate examples of refractive elements with strain-induced curvature.

6A-6D illustrate examples of refractive elements with doped regions.

7A-7B illustrate an example of controlling the refractive element with the piezoelectric effect.

8A-8B illustrate examples of controlling refractive elements with capacitive effects.

FIG. 9 is a block diagram of an example of making an optical device.

Figure 10 shows an example of a flow chart for fabricating an optical device.

Like reference numbers and names refer to like elements throughout the various figures. It is also to be understood that the various exemplary embodiments shown in the drawings are illustrative only and have not necessarily been drawn to scale.

FIG. 1A shows a block diagram of an example of an optical device 100 that includes a refractive element 101 . A refractive element 101 (also referred to as a "lens") can be used to couple light into or out of the optical device 100 . Exemplary optical devices 100 include, but are not limited to, lenses, optical filters, collimators. Exemplary lenses include light transmissive lenses, reflective lenses, or combinations thereof. Optical device 100 is capable of refracting, filtering, collimating, focusing, defocusing, diverging, converging and/or reflecting light beams.

In general, an optical device may have one or more optical specification parameters. In some implementations, the optical specification parameter may be numerical aperture, which allows the optical element to capture a cone of light within a specific angle. For example, a single mode fiber may have a numerical aperture of 0.14. In some implementations, an optical specification parameter may be a specific dimension that allows the optical element to emit or receive light. For example, an optical detector may have a 100 μm ² detection area for receiving light.

The transmission of light from one optical element to another optical element that does not match its optical specifications usually results in a loss of optical power. To reduce losses, a lens can be used to reduce the mismatch in the optical parameter specifications of the two optical elements; for example, a lens can be used to match the numerical aperture between the two optical elements. In another example, a lens may be used to focus light onto an optical element having a smaller area. Furthermore, light propagating in an optical system can be associated with multiple wavelengths, and filters can be used between optical elements to select one or more target wavelengths among the multiple wavelengths of light. Preferably, the lens or filter can be integrated with other optical devices to reduce integration complexity and manufacturing cost; in addition, the lens and filter are preferably integrated into one optical device to reduce integration complexity and manufacturing cost.

The optical device 100 includes a refractive element 101 and an optical medium 107 . Generally, refractive element 101 is configured to refract and/or filter light from external medium 119 to optical medium 107 or from optical medium 107 to external medium 119 . In one example, the incident light 111 entering the optical device 100 has two wavelengths λ1 and λ2 , the light of the wavelength λ1 is filtered by the refractive element 101 , and the light of the wavelength λ2 is refracted and focused by the refractive element to form a focus entering the optical medium 107 beam. It is noted here that the foregoing examples are not limiting, and that refractive element 101 may be designed to select or filter one or more other wavelengths, or to perform other optical functions, such as defocusing or collimation of a beam of light beam.

The refractive element 101 is composed of one or more semiconductor materials. For example, the refractive element 101 may be made of silicon, germanium, tin or III-V compounds. The refractive element 101 has a band gap energy, which depends on the band gap energy of the semiconductor material contained in the refractive element 101 . The refractive element 101 has a bandgap wavelength, which depends on the bandgap energy of the refractive element 101, eg, determined by the following formula: λ=(hc)/E...(1); where λ is the bandgap wavelength and h is Planck's constant, c is the speed of light, and E is the band gap energy.

Depending on the bandgap energy of the refractive element 101, the refractive element 101 is capable of filtering or refracting electromagnetic radiation within a specific wavelength range. For example, a refractive element 101 with a band gap wavelength of 700 nm can absorb (or filter) incident electromagnetic radiation with wavelengths shorter than 700 nm (eg, visible light wavelengths), and emit (or refract) incident electromagnetic radiation with wavelengths longer than 700 nm (eg, , infrared wavelengths).

In general, refractive element 101 includes one or more curved surfaces (eg, curved surface 103 ) and/or substructures 105 . The curved surface 103 may have a predetermined radius of curvature, and the aforementioned radius of curvature may be configured to refract incident light according to Snell's law (or "refraction law") or any suitable numerical analysis model. Exemplary numerical analysis models include a ray tracing model, a Gaussian beam model, a beam propagation method (BPM) model, or a finite-difference time-domain; Referred to as FDTD) model.

The one or more substructures 105 can comprise a set of periodic substructures in one dimension, two dimensions, three dimensions, or a combination thereof. In the example shown in Figure 1A, a set of two-dimensional periodic substructures formed in the refractive element 101 . As used herein, the substructures 105 may comprise photonic crystals, gratings, or periodic substructures to affect the optical properties of light coupled to the periodic substructures. Other example substructures are described in more detail in Figures 3A-3D.

In some implementations, the set of substructures 105 is periodic (referred to herein as "periodic substructures"), and can be configured to refract light or filter light according to guided mode resonance effects Light. In the guided wave mode resonance effect, a set of substructures are formed of materials having a higher index of refraction than the body of the refractive element 101, the optical medium 107 and the external medium 119 to form at least one guided wave mode in a periodic structure. The guided wave mode interferes with the diffraction mode of the periodic structure to produce a resonant response that can be used as a filter. In some implementations, the combination of curved surface 103 and resonant reaction can refract light into different directions.

In some embodiments, one or more of the substructures 105 are sub-wavelength structures. The subwavelength structures may be smaller in size than the bandgap wavelength of refractive element 101 in at least one dimension. In some embodiments, the set of substructures 105 are arranged in a periodic pattern. In some examples, the period of the periodic structure dependent on the guided wave modal resonance effect is smaller than the bandgap wavelength of the refractive element 101 . Other example sub-wavelength structures are described in more detail in Figure IB.

In some aspects, a set of substructures 105 may be configured to refract or filter light according to an effective index change effect. In the equivalent refractive index changing effect, the design of the set of substructures 105 produces an equivalent refractive index profile along an axis of the refractive element 101 . For example, the set of periodic structures 105 may allow direct The diameter and/or period is varied along the x- and y-axis periodicity to produce an equivalent refractive index profile. In some implementations, the combination of the curved surface 103 and the equivalent refractive index profile can refract light into different directions. In some embodiments, the combination of the curved surface 103 and the equivalent refractive index profile can result in a combined phase change of the refracted light, thereby creating an optical focus/defocuser. In some implementations, the substructure 105 based on the effect of the equivalent refractive index change has a periodicity, and its periodicity may be deep subwavelength in size.

In some implementations, in order to reduce or eliminate polarization effects of incident light 111, a set of periodic structures 105 can be designed to have symmetry rotated about 90 degrees of their optical axis. In this example, the aforementioned optical axis is along the z-axis at the center of the refractive element 101 .

Optical medium 107 may comprise any material capable of transmitting, directing, detecting or generating light. For example, the optical medium 107 may be a semiconductor substrate of silicon, oxide, nitride, or combinations thereof. In other examples, the optical medium 107 may be air. In other examples, the optical medium 107 may include a germanium photodetector that absorbs light. In other examples, the optical medium 107 may be a multilayer vertical-cavity surface-emitting laser (VCSEL for short).

External medium 119 can be any medium capable of transmitting, directing, detecting or generating light. For example, the external medium 119 may be an optical fiber. In other examples, the external medium 119 may be a photodetector. In other examples, the external medium 119 may be a light source. In other examples, the external medium 119 may be air. In other examples, the external medium 119 may be a semiconductor substrate, such as silicon, oxide, nitride, or a combination thereof. In other examples, A cladding layer composed of one or more layers of nitride, oxide, air, or organic material may be formed between the external medium 119 and the refractive element 101 .

In some embodiments, refractive element 101 and optical medium 107 may be composed of different materials. For example, the refractive element 101 may be composed of silicon, and the optical medium 107 may be composed of oxide. In some embodiments, refractive element 101 and optical medium 107 may be composed of the same material. For example, refractive element 101 and optical medium 107 may be composed of germanium or other III-V semiconductor materials. In some embodiments, the refractive element 101 may be composed of multiple layers of materials. 1C and 1D show examples of multilayer refractive elements. Optical medium 107 may be composed of multiple layers of materials. For example, multilayer anti-reflection coatings may be deposited to minimize reflections between refractive element 101 and optical medium 107 . In some embodiments, the refractive element may function as filtering, focusing/defocusing, or both.

FIG. 1B shows examples of refractive elements 131 a - 131 e , which may be used as refractive elements 101 in optical device 100 , respectively. Any of the refractive elements 131a-131e may also be implemented in optical devices described herein or in photonic integrated circuits not described herein.

Conceptually, the refractive element can be divided into a lens portion 121 and a substructure portion 123 . Generally, light incident on the lens portion 121 is refracted on its surface having a predetermined radius of curvature. In some embodiments, the surface curvature can be created by deliberate or unintentional strain in the process, and the resulting radius of curvature is much larger than the size of the refractive element. In some embodiments, the aforementioned surface can be patterned and etched with a grayscale mask to create surface curvature.

Generally, the substructure portion 123 includes one or more one-dimensional, two-dimensional, or three-dimensional substructures. Substructures can create one or more sets of periodic substructures. For example, the substructure portion 123 shown in FIG. 1B includes a first set of periodic substructures 125 and a second set of periodic substructures 127 . The first set of periodic substructures 125 can be designed to produce an equivalent refractive index change effect, and the second set of periodic substructures 127 can be designed to produce a guided wave mode resonance effect. In some embodiments, the superposition of the first set of periodic substructures 125 and the second set of periodic substructures 127 produces substructure portions 123 and serves to refract and filter incident light.

The lens portion 121 and the substructure portion 123 may be combined to form a refractive element. For example, the refractive element 131a may be formed by etching the substructure portion to the bottom of the lens portion to provide a high refractive index contrast between the substructure portion and the lens portion. In other examples, if the lens portion has a convex surface, the refractive element 131b may firstly etch the sub-structure so that the peak portion of the sub-structure changes with the curvature of the lens portion. The refractive element 131b may be formed by etching the substructure after forming the lens portion. In other examples, if the lens portion has a convex surface, the refractive element 131c can etch a sub-structure so that the peak portion of the sub-structure changes with the curvature of the lens portion. The refractive element 131c may be formed by etching the complementary pattern of the substructure after forming the lens portion.

In other examples, if the lens portion is a concave surface, the refractive element 131d can make the concave portion of the sub-structure change with the curvature of the lens portion by etching the sub-structure. The refractive element 131d may be formed by etching the substructure prior to forming the lens portion. In other examples, if the lens portion is a concave surface, the refractive element 131e may be formed by etching the substructure. The peaks of the substructures vary with the curvature of the lens portion. The refractive element 131e may be formed by etching the substructure after forming the lens portion.

In some embodiments, in order to filter, focus, or defocus one or more wavelengths of incident light, one or more substructures may be filled with one or more materials that differ from the equivalent refractive index of the refractive element. For example, the refractive element may be composed of silicon, and the voids of the set of substructures may be at least partially filled with oxide or nitride. In other embodiments, the radius of one or more substructures may be different from the radius of the other one or more substructures in order to filter, focus, or defocus one or more wavelengths of incident light. For example, the radius of the periodic substructure 125 is different from the radius of the periodic substructure 127 . In some embodiments, the set of substructures are sub-wavelength structures that have dimensions in at least one dimension smaller than the bandgap wavelength of the lens. For example, the substructures in the periodic substructure 127 may be sub-wavelength structures with diameters smaller than the bandgap wavelength of the lens 121 . In some embodiments, the plurality of substructures in the set of periodic structures may have locally non-uniform periods in order to filter, focus, or defocus one or more wavelengths of incident light.

FIG. 1C shows a multilayer refractive element 140 that may be implemented in optical device 100 . Although not shown in the figures, the multilayer refractive element 140 may include curved surfaces. The multilayer refractive element 140 includes three layers 141 , 143 and 145 . In some embodiments, layers 141, 143, and 145 may be composed of different materials, such as dielectrics (eg, oxides, nitrides, polymers, or air), semiconductors (eg, silicon, germanium, or III-V materials) or metals (eg: aluminum, tungsten or other metals). For example, any of the one or more layers 141, 143, and 145 may be composed of an absorber material, such as germanium. In other examples, two or more layers 141, 143 and 145 may be composed of gain materials, such as III-V materials. The substructure can be formed on the top layer 145 , and the other two layers 141 and 143 can provide surface stress to the top layer 145 to form the surface curvature of the multilayer refractive element 140 . In some other implementations, the multilayer refractive element 140 may have fewer or more layers. In some other implementations, periodic substructures may be formed over more than one layer.

FIG. 1D shows a multilayer refractive element 150 that may be implemented in the photonic optical device 100 . Although not shown in the figures, the multilayer refractive element 150 may include curved surfaces. The multilayer refractive element 150 includes three layers 151 , 153 and 155 . Layers 151, 153 and 155 may be composed of different materials such as dielectrics (eg oxides, nitrides, polymers or air), semiconductors (eg silicon, germanium or III-V materials) or metals (eg: aluminum, tungsten or other metals). For example, one or more layers 151, 153 and 155 may be composed of an absorbing material, such as germanium. In other examples, two or more layers 151, 153, and 155 may be composed of gain materials, such as III-V materials. In some embodiments, one or more substructures may be formed over layer 153 between two layers 151 and 155 . For example, layer 153 may have a higher index of refraction than layers 151 and 155 to create a guided wave modal resonance effect in multilayer refractive element 150. In some other implementations, the multilayer refractive element 150 may have fewer or more layers. In other embodiments, the substructures may be formed over more than one layer.

FIG. 1E shows a stacked refractive element 160 . In general, laminated refractive elements 160 can provide design flexibility. For example, the stacked refractive element 160 may include a first optical device 161 and a second optical device 163 optically coupled to the first optical device 161 . The first and/or second optical device is a lens, filter, or a combination thereof. For example, the first optical device 161 may be designed to pass (filter out) light (or electromagnetic radiation) having a wavelength range of 930 nm to 945 nm, and the second optical device 163 may be designed to pass (filter out) a wavelength range of 935 nm light (or electromagnetic radiation) to 950 nm. By stacking the first optical device 161 and the second optical device 163, a narrower bandwidth filter with a passing wavelength range of 935 nm to 945 nm can be provided. The first optical device 161 and the second optical device 163 may be implemented using the refractive elements described herein. In some implementations, the first optical device 161 can operate under the equivalent refractive index change effect to change the beam profile, and the second optical device 163 can operate under the guided wave modal resonance effect to select the desired wavelength. In some implementations, the equivalent refractive index of the second optical device 163 is different from the equivalent refractive index of the first optical device 161 . In some implementations, the equivalent refractive index of the second optical device 163 is the same as the equivalent refractive index of the first optical device 161 . In some implementations, the second set of substructures included in the second optical device 163 is different from the first set of substructures included in the first optical device 161 . In some other implementations, the second set of substructures included in the second optical device 163 are the same size as the first set of substructures in the first optical device 161 . In some embodiments, the refractive elements may be filters, while other refractive elements may be focusers or defocusers.

Figure 2A shows a block diagram of an optical device 200 that integrates active and refractive elements. In this example, incident light 208 having two wavelengths λ1 and λ2 is incident on the optical device 200 , wherein the wavelength λ1 light penetrates the optical device 200 to become light 209 , and the wavelength The λ2 light is filtered out by the optical device 200 . Light 209 is focused to a photodetector to measure optical power at wavelength λ1.

The optical device 200 includes a refractive element 201 , an optical medium 203 , a cover element 204 , a substrate 205 and an active element 207 . The refractive element 201 may be implemented by the refractive elements described herein. For example, the refractive element 201 can be realized by the refractive element 101 shown in FIG. 1A . Here, refractive element 201 is configured to focus incident light 208 to active element 207 . Furthermore, the refractive element 201 is configured to filter out one or more light (or electromagnetic radiation) including wavelength λ2.

Optical medium 203 may be composed of materials that allow light 209 to penetrate or partially penetrate. In some implementations, the thickness of optical medium 203 may be the focal length of refractive element 101 . In other implementations, the thickness of the optical medium 203 can be designed to produce a light spot of a particular size on the active element 207 .

A cover element 204 is formed over the refractive element 201 to reduce reflection of incident light 208 and/or protect the refractive element 201 . In some embodiments, the equivalent refractive index of cover element 204 is lower than the equivalent refractive index of refractive element 201 . In some embodiments, the capping element 204 may be composed of one or more layers of nitride, oxide, air, or organic materials.

Substrate 205 may be any substrate suitable for fabricating photonic integrated circuits. For example, the substrate 205 may be a silicon wafer, a silicon-on-insulator (SOI) wafer, a III-V material (eg, gallium arsenide or indium phosphide), a flexible organic substrate, a quartz wafer, or a glass wafer. in other embodiments In this case, the substrate 205 may be a passive material layer or an active material layer deposited on an integrated electronic circuit.

Active element 207 may be an optical element that transmits, modulates, switches or absorbs light. In this example, the active element 207 is a photodetector and is configured to absorb a portion of the light 209, thereby measuring the optical power of light of wavelength λ1. In other embodiments, the active device 207 may be formed of one or more layers of silicon, germanium, tin, or III-V compounds.

Figure 2B shows an optical device 210 for directing light. In this example, incident light 218 has two wavelengths λ1 and λ2 incident on optical device 210 , where wavelength λ1 light penetrates optical device 210 and wavelength λ2 light is filtered out by optical device 210 . Light 219 is focused into an optical medium and exits optical device 210 as light 221. Light 221 may be directed to another optical device or another optical system for further processing.

The optical device 210 includes at least one refractive element 211 , an optical medium 213 , a cover element 214 and an external medium element 215 . The refractive element 211 may be implemented by the refractive elements described herein. For example, the refractive element 211 may be implemented using the refractive element 150 as shown in FIG. 1D . Here, refractive element 211 is configured to focus incident light 218 . Furthermore, the refractive element 211 can also be configured to filter out one or more light (or electromagnetic radiation) comprising wavelength λ2.

Optical medium 213 may be implemented using the optical medium described herein. For example, the optical medium 213 may be implemented using the optical medium 203 depicted in FIG. 2A. Cover element 214 may be implemented using cover elements described herein, such as cover element 204 of Figure 2A. external Medium 215 may be implemented using external media described herein. For example, the external medium 215 may be implemented using the external medium 119 described in FIG. 1A . In other embodiments, the equivalent refractive index of cover element 214 is higher than the equivalent refractive index of refractive element 211 .

Figure 3A shows a set of periodic structures 331 in the xy plane. The set of periodic structures 331 is an example of a substructure formed in a refractive element. The disclosure of FIG. 3A is applicable to any of the refractive elements described herein. The set of periodic structures 331 comprises an array of one-dimensional periodic structures 301a-n and 303a-n along the x-direction, where n is an integer greater than one. The set of periodic structures can be one-dimensional gratings or one-dimensional photonic crystals. In some embodiments, the set of periodic structures 301a-n and 303a-n may be composed of different materials. The set of periodic structures may be one-dimensional gratings or one-dimensional photonic crystals. In other embodiments, the set of periodic structures 301a-n and 303a-n may be composed of different materials. For example, the periodic structures 301a-n may be composed of silicon, while the periodic structures 303a-n may be composed of oxide. In other embodiments, the periodic structures 303a-n may comprise a layer of translucent metal, such as ITO, and produce a surface plasmonic effect. The arrangement of 301a, 303a, 301b, 303b . . . 301n and 303n may constitute a periodic structure of the refractive element.

FIG. 3B shows an example of a set of periodic structures 332 in the xy plane. The set of periodic structures 332 are examples of substructures that can be formed in the substructure portion of the refractive element. The description of Figure 3B is applicable to any of the refractive elements described herein. The set of periodic structures 332 includes a two-dimensional periodic structure 305a and layers 305b. In other implementations, the periodic structure 305a may correspond to the peaks of the grating. In other implementations, the periodic structures 305a may correspond to recesses of a grating. The arrangement of the two-dimensional periodic structures 305a constitutes the The periodic structure of the radiating element. In other implementations, layer 305b may be oxide and periodic structure 305a may be silicon.

Figure 3C shows an example of a set of periodic structures 333 in the xy plane. The set of periodic structures 333 is an example of a substructure that can be formed in the substructure portion of the refractive element. The description of Figure 3C is applicable to any of the refractive elements described herein. The set of periodic structures 333 includes an array of two-dimensional rectangular periodic structures 307a to 307n arranged along the x-direction, and an array of 307a to 307k arranged along the y-direction. In other embodiments, the periodic structure 307a may be a grating or a peak portion of a photonic crystal. In other embodiments, the periodic structure 307a may be a grating or a recess of a photonic crystal. In other embodiments, periodic structure 307a and layer 308 may be composed of the same material, such as silicon. In other embodiments, periodic structure 307a and layer 308 may be composed of different materials. For example, the periodic structure 307a may be composed of silicon, and the layer 308 may be composed of oxide or nitride. In other implementations, the periodic structures 307a may be square, circular, non-square, or a combination of different geometric structures. The arrangement of periodic structures 307a-n and 307a-k in the xy plane forms the periodic structure of the refractive element. In other embodiments, the periodicity of the periodic structure along the x-direction 321 and along the y-direction 322 and the interference pattern along the x-direction and along the y-direction within layer 308 (under guided wave mode resonance effects) are approximately match.

Figure 3D shows an example of a periodic structure 334 on the xy plane. The set of periodic structures 334 are examples of substructures that can be formed in the substructure portion of the refractive element. The description of Figure 3D is applicable to any of the refractive elements described herein. The set of periodic structures 334 includes a two-dimensional array of arbitrary-shaped periodic structures 309a to 309n, where n is an integer greater than 1 number. In other embodiments, the arbitrarily shaped periodic structure 309a may be a grating or the peaks of a photonic crystal. In other embodiments, the arbitrarily shaped periodic structures 309a may be gratings or recesses of photonic crystals. In other embodiments, the arbitrarily shaped periodic structure 309a and layer 310 may be composed of different materials. For example, the arbitrarily shaped periodic structure 309a may be composed of silicon dioxide and the layer 310 may be composed of silicon. In other embodiments, the arbitrary shape in periodic structure 309a can be triangular, circular, elliptical, or a combination of different shapes. The periodic structures 309a-n of arbitrary shape in the xy plane constitute the periodic structure of the refractive element. In other implementations, the specific shape and relative distance of any of the arbitrarily shaped periodic structures 309a-309n can be determined using numerical analysis. For example, a finite difference time domain analysis program can be used to design the shape of each of the arbitrarily shaped periodic structures 309a to 309n.

FIG. 4 shows an example of a photonic integrated circuit 400 with multiple refractive elements for filtering light of different wavelengths. In short, refractive elements can be formed on a single substrate, and each refractive element can be used to filter its corresponding wavelength range and used for wavelength-division multiplexing (WDM) or imaging/spectral sensing applications, to monitor optical power over multiple wavelength ranges. Additionally or alternatively, each refractive element may be designed to refract light (or electromagnetic radiation) of the corresponding wavelength range in a desired manner.

In this example, the photonic integrated circuit 400 includes a first refraction element 401, a second refraction element 403, a third refraction element 405 and a fourth refraction element 407, and can be fabricated by semiconductor processes such as lithography and etching. The first refractive element 401 is configured to fold It emits and transmits light (or electromagnetic radiation) in the wavelength range including λ1, but not λ2, λ3 or λ4. The second refractive element 403 is used to refract and transmit light (or electromagnetic radiation) in the wavelength range including λ2, but not λ1, λ3 or λ4. The third refractive element 405 is used to refract and transmit light (or electromagnetic radiation) in the wavelength range including λ3, but not λ1, λ2 or λ4. The fourth refractive element 407 serves to refract and transmit light (or electromagnetic radiation) in the wavelength range including λ4, but not λ1, λ2 or λ3. When a light 411 containing broadband signals with wavelengths λ1, λ2, λ3 and λ4 is incident on the photonic integrated circuit 400, the first refraction element 401, the second refraction element 403, the third refraction element 405 and the fourth refraction element 407 Each wavelength of light is filtered out separately for further processing. In various implementations, different numbers of refractive elements may be formed in a photonic integrated circuit, and each of the refractive elements may not refract and/or filter out a particular wavelength range as in this example. In other embodiments, the incident light 411 has a broadband signal, wherein λ1 covers the red spectrum, λ2 covers the green spectrum, λ3 covers the blue spectrum, and λ4 covers the infrared spectrum. In other embodiments, the photonic integrated circuit 400 is viewed as a spectral filter that can be directly integrated with a CMOS image sensor on a single wafer to reduce the complexity and manufacturing cost of subsequent integration. Multiple refractive elements can be designed to have different photonic crystal structures and fine-tuned wavelength ranges for specific target spectra, and then fabricated using the same semiconductor lithography steps. In this way, the sensor can be integrated with more filters and have finer spectral filtering, which means finer spectral resolution for capturing more realistic images.

5A shows an example of a refractive element 500 with surface curvature due to compressive stress due to lattice mismatch or thermal expansion coefficient mismatch. Refractive element 500 includes refraction element 501 and optical medium 503. Generally speaking, when the optical medium 503 has a smaller lattice size than the refractive element 501, the resulting compressive strain a will make the surface of the refractive element 501 a convex curved surface. For example, the optical medium 503 may be composed of oxide, and the refractive element 501 may be composed of silicon. In some implementations, a convex curved surface can be used to partially focus incident light.

Figure 5B shows a refractive element 510 with surface curvature due to lattice mismatch or thermal expansion coefficient mismatch resulting in tensile stress. The refractive element 510 includes a refractive element 511 and an optical medium 513 . Generally, if the optical medium 513 has a larger lattice size than the refractive element 511, the resulting tensile strain will make the surface of the refractive element 511 concave. For example, the optical medium 513 may be composed of germanium, and the refractive element 511 may be composed of silicon. In other embodiments, concave surfaces can be used to partially defocus incident light.

Figure 5C shows refractive element 520 with surface curvature due to compressive stress on the sidewalls. The refractive element 520 includes a refractive element 521 and a sidewall 523 surrounding at least a portion of the circumference of the refractive element 521 . Under the action of compressive strain, the surface of the refractive element 521 becomes a convex curved surface. For example, the sidewalls 523 may be formed of thermal oxide or dense nitride, and the refractive element 521 may be formed of silicon. In other embodiments, convex surfaces can be used to partially focus incident light.

Figure 5D shows refractive element 530 with surface curvature due to tensile stress on the sidewalls. The refractive element 530 includes a refractive element 531 and a side wall 533 surrounding at least a portion of the circumference of the refractive element 531 . Under the action of tensile strain, the surface of the refractive element 531 becomes a concave curved surface. For example, the sidewall 533 may be composed of porous oxide or nitride, and the refractive element 531 may be composed of silicon. In other embodiments, concave surfaces can be used to partially defocus incident light.

FIG. 6A shows an example of a photonic integrated circuit 600 . The photonic integrated circuit 600 includes a modulating element having two doped regions coupled to the refractive element by at least partially embedding or integrating with the refractive element. The equivalent refractive index of the refractive element can be changed (by depletion or injection of free carriers) by varying the free carrier concentration of the doped region. By modulating the equivalent refractive index of the refractive element, the wavelength range of the light it filters or its corresponding refractive properties can vary. In some implementations, the modulating element may be configured to change the direction or depth of focus of at least a portion of the light exiting the refractive element, or to change one or more wavelengths of light filtered by a set of periodic structures of the refractive element scope. The photonic integrated circuit 600 includes a refractive element 601, and the refractive element may include a periodic structure used with any of the refractive elements described herein. In some implementations, the refractive element 601 may have a curved surface. Furthermore, the refractive element 601 includes a first doped region 602 and a second doped region 604 . For example, the first doped region 602 can be a p-type doped region, the second doped region 604 can be an n-type doped region, etc., which can form a PN junction in the refractive element 601 . In other embodiments, applying a reverse bias voltage to the PN junction can deplete the carriers therein and correspondingly change the equivalent refractive index. In other embodiments, applying a forward bias to the PN junction increases the carriers therein, which correspondingly changes the equivalent refractive index.

FIG. 6B shows an example of a photonic integrated circuit 610 . The photonic integrated circuit 610 includes a modulating element having three doped regions, and the modulating element can be coupled to the refractive element by being at least partially embedded in or integrated with the refractive element. Roughly speaking, within a refractive element, an increase in the number of doped regions can correspondingly increase the number of depletion regions, thereby increasing the number of depletion regions. Increase the total amount of tunable equivalent refractive index. The photonic integrated circuit 610 includes a refractive element 611, and the refractive element 611 may include a periodic structure used with any of the refractive elements described herein. In some embodiments, the refractive element 611 may have a curved surface. In this example, the refractive element 611 includes a first doped region 612 , a second doped region 614 and a third doped region 616 . For example, the first doped region 612 can be a p-type doped region, the second doped region 614 can be an n-type doped region, the third doped region 616 can be a p-type doped region, the first to third doped regions The impurity regions form PNP junctions in the refractive element 611 . In other examples, the first doped region 612 can be a p-type doped region, the second doped region 614 can be an intrinsic region, the third doped region 616 can be an n-type doped region, etc. in the refractive element 611 A P-I-N junction is formed. In other implementations, applying a reverse bias to the PN junction can deplete the carriers therein, thereby changing its equivalent refractive index. In other embodiments, applying a forward bias to the PN junction increases the carriers therein, thereby changing its equivalent refractive index.

FIG. 6C shows a photonic integrated circuit 620 . The photonic integrated circuit 620 includes a modulating element, and the modulating element has doped regions arranged to cross each other. Roughly speaking, the interdigitated doped regions are used when the diameter of the refractive element is much larger than the depletion region created by the PN junction. The equivalent refractive index can be greatly changed by forming doped regions in the refractive element that are arranged to cross each other. Photon integration circuit 620 includes refractive element 621, which may comprise a set of periodic structures used with any of the refractive elements described herein. In other implementations, the refractive element 621 may comprise a curved surface. In addition, the refractive element 621 includes doped regions 622a to 622n which are arranged to cross each other, wherein n is an integer. In one example, the interdigitated doped regions 622a to 622n may have alternating p-type doping impurity regions and n-type doped regions to form pnpnp... junctions within the refractive element 621. In other examples, the interdigitated doped regions 622a to 622n may have alternately arranged p-type doped regions, intrinsic regions (i) and n-type doped regions to form a pinpinp-.. . junction. In other embodiments, applying a reverse bias to a pn or pin junction can deplete the carriers therein, thereby changing the equivalent refractive index. In some embodiments, applying a forward bias to a pn or pin junction increases the carriers therein, thereby changing the equivalent refractive index.

FIG. 6D shows an example of a photonic integrated circuit 630 . The photonic integrated circuit 630 includes an optical medium integrated in a modulating element, and the modulating element includes a plurality of doped regions. The equivalent refractive index of an optical medium can be modulated by depletion or injection of free carriers. Modulation of the equivalent refractive index of the optical medium changes the refractive properties of light exiting the refractive element. Photonic integrated circuit 630 includes refractive elements 631 formed on optical medium 633, which may include a set of periodic structures used with any of the refractive elements described herein. In some implementations, the refractive element 631 may have a curved surface. The optical medium 633 may include a first doped region 635 and a second doped region 637 . For example, the first doped region 635 can be a p-doped region, the second doped region 637 can be an n-doped region, and the like form a PN junction within the optical medium 633 . In some implementations, applying a reverse bias to the PN junction can deplete the carriers therein, thereby changing the equivalent refractive index. In some embodiments, applying a forward bias to the PN junction can increase carriers, thereby changing the equivalent refractive index.

FIG. 7A shows a photonic integrated circuit 700 composed of refractive elements controlled by the piezoelectric effect. In general, in piezoelectric materials, applying a bias voltage imparts stress that alters the piezoelectric material shape. In such an example, the photonic integrated circuit 700 includes an optical medium 703, a refractive element 701 formed on the optical medium 703, and a voltage source 705 coupled to the refractive element. The refractive element 701 may comprise a set of periodic structures, which may be implemented by any of the refractive elements described herein. In some implementations, refractive element 701 may comprise a curved surface. Furthermore, the refractive element 701 may comprise a piezoelectric material. In some implementations, the voltage of the voltage source 705 produces a mechanical force that changes the predetermined radius of curvature of the surface in the refractive element 701 . In some embodiments, the voltage of the voltage source 705 produces a mechanical force that causes the radius or period of the photonic crystal structure in the refractive element 701 to change.

FIG. 7B shows a photonic integrated circuit 710 composed of refractive elements controlled by the piezoelectric effect. In this example, the photonic integrated circuit 710 includes an optical medium 713, a refractive element 711 formed on the optical medium 713, and a voltage source 715 coupled to the optical medium. The refractive element 711 may comprise a set of periodic structures, which may be implemented by any of the refractive elements described herein. In some implementations, refractive element 711 may comprise a curved surface. Optical medium 713 may include piezoelectric material. In some implementations, the voltage of the voltage source 715 generates a mechanical force on the optical medium 713 that changes the predetermined radius of curvature of the surface of the refractive element 711 formed on top of the optical medium 713 . In other embodiments, the voltage of the voltage source 715 produces a mechanical force on the optical medium 713 to change the path length of light propagating along the z-axis within the optical medium 713.

FIG. 8A shows a photonic integrated circuit 800 composed of a refractive element controlled by a capacitive effect. Generally speaking, static electricity is generated between the refracting element and the optical medium by the Micro-Electro-Mechanical System (MEMS) force, which in turn causes displacement of the refractive element relative to the optical medium. In this example, the photonic integrated circuit 800 includes an optical medium 803 , a refractive element 801 , a support element 807 , and a voltage source 805 coupled to the refractive element 801 and the optical medium 803 . The refractive element 801 may comprise a curved surface or a set of periodic structures, and may be implemented by any of the refractive elements described herein. In addition, the refractive element 801 and the optical medium 803 can be used as electrodes at both ends of the capacitor, and an electrostatic force is generated between the refractive element 801 and the optical medium 803 by applying an external electric field through the voltage source 805 . In one example, positive charges can accumulate on the bottom of refractive element 801 and negative charges can accumulate on the top of optical medium 803 , which can create electrostatic forces to change the relative distance between refractive element 801 and optical medium 803 . Since the supporting element 807 can support at least two ends of the refractive element 801 , the electrostatic force can make the position of the refractive element relative to the optical medium change as shown by the arrow 809 . In some embodiments, the change in distance can be used to adjust the optical path of the focused beam exiting the refractive element 801 . In some implementations, the application of an external electric field by the voltage source 805 can change the radius, period, or predetermined radius of curvature of the surface of the photonic crystal of the refractive element 801 .

FIG. 8B shows a photonic integrated circuit 810 composed of refractive elements controlled by capacitive effects. Generally speaking, electrostatic force can be generated between the refracting element and the optical medium by the micro-electromechanical system, thereby causing the direction of the optical axis of the incident light of the refracting element to change. In this example, the photonic integrated circuit 810 includes an optical medium 813 , a refractive element 811 , a support element 817 , and a voltage source 815 coupled to the refractive element 811 and the optical medium 813 . The refractive element 811 can include a curved surface or a set of periodic structures, and can be implemented with any of the refractive elements described herein. In one example, positive charges can accumulate at the bottom end of the refractive element 811 and negative charges can accumulate at the top end of the optical medium 813 near the bottom end of the refractive element 811, which can create electrostatic forces to alter the refractive element 811 and the optical Distance between media 813. Since the supporting element 817 supports only one end of the refractive element 811, the refractive element 811 can be regarded as a cantilever. Electrostatic forces can cause a change in the orientation of the refractive element relative to the optical axis of the incident light, as indicated by arrow 819. In some embodiments, changes in the aforementioned directions can be used to adjust the angle of incidence of incident light into refractive element 811 . In some embodiments, changes in the aforementioned directions can be used to adjust the angle of incidence of the light signal entering the refractive element 811 from the optical medium 813 .

Figure 9 shows an example of a flow chart for making a refractive element. Process 900 may be used to fabricate optical devices 100, 200, 210, or other optical devices disclosed herein. The fabricated optical device can form an optical device attached to or integrated on other optical devices.

Process 900 includes forming a first curved surface 904 on a substrate 902 . The substrate 902 may be a semiconductor wafer or an SOI wafer. The first curved surface 904 can be formed by removing or adding semiconductor material to the substrate. The semiconductor material may be deposited on the substrate 902 and then patterned by a lithographic imaging process. In addition, the semiconductor material can also be removed from the substrate 902 to form the first curved surface. For example, etching may be used to remove semiconductor material from the substrate 902 . The etching includes dry etching, wet etching or other suitable etching processes to form the first curved surface 904 . For example, a grayscale mask can be used to etch the substrate 902 to form the first curved surface 904 . . For example, the substrate 902 can be etched by controlled lithography, and the UV dose can be controlled to vary the etch depth.

The semiconductor material 922 of the substrate 902 may have a predetermined band gap energy. The bandgap energy of semiconductor 922 helps the optical device to transmit (or refract) incident electromagnetic radiation having a first wavelength range and absorb electromagnetic radiation having a second wavelength range. In some embodiments, the first wavelength range exceeds 700 nm (eg, infrared radiation). For example, semiconductor 922 may have a bandgap energy between 1.2 and 1.7 electron volts (eV).

In some examples, semiconductor 922 is transparent to electromagnetic radiation having wavelengths in excess of 940 nm. In some embodiments, the second wavelength range is below 800 nm. For example, semiconductor 922 may have a bandgap wavelength between 400 nm and 800 nm. The band gap wavelength can be calculated by the aforementioned formula (1).

A bonding layer 924 is deposited on the first curved surface 904 (see structure 908). The bonding layer may form at least a portion of the optical medium 107 shown in FIG. 1A . The bonding layer may be deposited on the first curved layer by thin film deposition techniques such as chemical vapor deposition, plasma enhanced chemical vapor deposition, sputtering, or any other suitable thin film deposition technique. The bonding layer may be a semiconductor material, oxide, nitride, metal, or a combination thereof. The bonding layer may be transparent to all wavelengths of light (or electromagnetic radiation) refracted by the semiconductor material 922, or may absorb some of the aforementioned wavelengths of light (or electromagnetic radiation).

In some embodiments, the bonding layer 924 has an optical thickness corresponding to the focal length of the optical device. For example, the optical thickness of the bonding layer (eg, optical medium 203 in FIG. 2A ) may be sufficient to focus light (or electromagnetic radiation) refracted by a refractive element (eg, 201 ) to a particular point (eg, active element 207 ). The optical thickness of the bonding layer 924 depends on the bonding layer 924 thickness and refractive index. The thickness of the bonding layer may depend on the radius of curvature of the first curved surface (and/or the second curved surface). In this way, the bonding layer can be set to have a specific thickness.

The bonding layer may have a predetermined thickness by depositing a layer having a predetermined thickness by deposition techniques. In order to adjust the thickness of the bonding layer, the bonding layer can also be planarized or polished, eg by chemical mechanical polishing. For example, the bonding layer can be rubbed with a pad and abrasive and/or aggressive chemical slurries to the desired thickness. Depending on the initial thickness of the element and the desired thickness of the bonding layer, the rubbing process can take place at a certain speed and for a certain period of time. In addition, any irregularities in the surface of the bonding layer can be made uniform by the planarization process. Irregular topographies on the surface of the bonding layer can cause unintentional refraction or scattering of electromagnetic radiation into or out of the optical device. A homogenized bonding layer can improve the uniformity of refraction and/or filtering of electromagnetic radiation across the cross-section of the optical device.

In some embodiments, the second curved surface 934 is formed on the semiconductor material 922 and is opposite the first curved surface 904 . The techniques described above for forming the first curved surface can also be used to form the second curved surface. The first and second curved surfaces may be symmetrical, or both may have different shapes. The first and second surfaces can have the same radius of curvature, or both can have different radii of curvature. In some embodiments, the optics are fabricated for the target focal length. In some examples, the second curved surface is formed to cooperate with the first curved surface to provide the target focal length. In some examples, the second curved surface is formed to provide a target focal length in conjunction with the first curved surface and the bonding layer.

The optical device 910 formed in the above-described manner includes a refractive element 930 formed of a semiconductor material 922 and a bonding layer 924 . The refractive element 930 is formed of a first curved surface and a second curved surface; alternatively, the refractive element may have only one curved surface (eg, refractive element 101).

The refractive element 930 can be separated from the bonding layer 924 to form a separate lens, and can then be attached to a photonic integrated circuit, for example. For example, if the bonding layer 924 is composed of oxides and/or nitrides, it can be etched from the optical device by wet etching techniques, eg, by hydrofluoric acid (HF), ammonium fluoride (NH4F), or the like etc. Combination of wet etching.

In some implementations, a refractive element may comprise one or more substructures, such as substructure 123 shown in Figure IB. In some embodiments, the substructure can be formed on another semiconductor substrate and bonded to the refractive element and/or bonding layer. For example, the substructure portion 123 may be formed by etching a semiconductor substrate, and may be bonded to a refractive element (eg, the lens portion 121).

In some embodiments, the substructure is formed on the refractive element. The substructures may be formed by selectively etching one or both of the first curved surface 904 and/or the second curved surface 934 . The substructures may be unfilled structures, or the substructures may be filled with a different material than the semiconductor material of the substrate 922 . In some examples, a set of substructures is filled with a material with a higher index of refraction than the substrate 922, which can provide a guided wave mode in the optical device. Substructures can also be formed by thin film deposition. For example, a photomask can be used to deposit periodic patterns, gratings or photonic crystals on corresponding curved surfaces to form a set of substructures. The deposited substructure may be of the same material as refractive element 930 , or the substructure may be composed of a different material than refractive element 930 . For example, the substructure can be made of semiconductor material (eg, silicon) or a combination of nitrides, oxides, or the like. In some examples, more than one reticle may be used to deposit different materials for the substructures. For example, a first reticle can be used to deposit semiconductor materials and a second reticle can be used to deposit nitride materials. The semiconductor and nitride substrates can form alternating gratings. The one or more substructures formed have a dimension in one dimension that is at least smaller than the bandgap wavelength of the refractive element 930 .

As described in Figure 2, the optical device may be attached to or integrated with the optical element. The optical elements may be positioned relative to the bonding layer 924 to allow the optical device to receive electromagnetic radiation refracted by the optical elements. The optical element may be positioned relative to the refractive element 930, allowing the optical element to transmit electromagnetic radiation into the optical device. The optical element may be configured to alter the light (or electromagnetic radiation) of the first wavelength range that is refracted by the optical device, and/or the light (or electromagnetic radiation) that is absorbed by the optical device of the second wavelength range.

The optical element attached to the optical device may also be an active optical element. Active optical elements may be active optical elements used to transmit, modulate, switch, or absorb light. For example, the active optical element may be a photodetector configured to absorb at least a portion of the light refracted by the optical device, thereby measuring the optical power of the light at one or more wavelengths. Other examples of active optics include, but are not limited to, sensors, light emitting diodes, and lasers. Active optical elements may be composed of one or more layers of silicon, germanium, tin, or III-V compounds.

The optical element attached to the optical device may be the second optical device. The combination of the first and second optical elements can provide greater flexibility in the refraction and/or filtering of incident electromagnetic radiation sex. For example, the first optical device may refract incident electromagnetic radiation having a first wavelength range and/or filter electromagnetic radiation having a second wavelength range.

The first optical device and the second optical device may be configured to collectively refract incident electromagnetic radiation having a third wavelength range and/or filter electromagnetic radiation having a fourth wavelength range. The third wavelength range may be a sub-range of the first wavelength range. The fourth wavelength range may be a sub-range of the second wavelength range. The first optical device and the second optical device may each have refractive elements. The refractive element may have one or more curved surfaces and/or one or more substructures. The one or more substructures may comprise a periodically configured set of substructures. A set of sub-structures may be sub-wavelength structures. At least one sub-wavelength structure of the first and/or second optical element has a dimension (eg, diameter) along at least one dimension that is smaller than the bandgap wavelength of the refractive element of the first and/or second optical device. For example, the second refractive element may have a sub-wavelength structure that is smaller in size along at least one dimension than the bandgap wavelength of the first refractive element.

When fabricating the first optical device, the optical element and the first optical device can be integrated. For example, in step 912 , optical element 926 is bonded to bonding layer 924 of structure 912 . Structure 908 includes a refractive element having a first curved surface. After bonding optical element 926, structure 912 can be further fabricated to form a refractive element (eg, refractive element 930) having two curved surfaces. Alternatively, the optical element may be attached to the optical device at any time after fabrication of the optical device is completed. For example, in step 914, optical unit 926 and optical device 910 are joined. When the optical device or active element has curvature, the active element can be bonded to the optical device by various bonding techniques, including hybrid Alloy metal/dielectric wafer bonding technology, metal eutectic bonding technology, oxide-oxide bonding technology, or use polymer or other adhesives and adhesive materials to bond active elements and optical components.

Optical element 926 may be an active optical element or a second optical device. The optical element 926 may be a semiconductor substrate on which a portion of the optical medium 107 may be formed. Optical element 926 may also be a semiconductor substrate used to fabricate another optical element or device. For example, optical element 926 may be a carrier wafer on which a second optical device may be fabricated.

Optical element 926 may be coupled with refractive element 930 or bonding layer 924 . In some implementations, the optical element 926 is coupled (or bonded) to the optical device by a second bonding element. For example, a second bonding layer can be formed on the second curved surface 934 of the optical device 910 , and the second optical element can be coupled to the second bonding layer opposite the first optical device 910 . The second bonding layer may have sufficient optical thickness to allow the electromagnetic radiation refracted by the first optical device to be focused to the second optical device. The second bonding layer can also be designed so that the electromagnetic radiation refracted by the first optical device is focused on a specific point on the second optical device. For example, the second bonding layer can direct electromagnetic radiation refracted by the first optical device to specific points on the second optical device, wherein the sub-wavelength structures are located at specific points on the second optical device.

In some embodiments, optical element 926 is embedded within refractive element 930. In some examples, optical element 926 may be embedded within one or more substructures of refractive element 930 . For example, one or more of the substructures may be filled with a semiconductor material that functions to sense, transmit, or absorb a predetermined range of wavelengths. For example, silicon germanium can be filled into one or more substructures for use as photodetectors to measure optical power at one or more wavelengths refracted by the optical device. The composition of silicon germanium can range from only a small amount of germanium to 100% germanium. Depending on the percentage of germanium, the bandgap energy of silicon germanium can be changed for detection of different wavelengths.

The curvature of the first and/or second curved surfaces may be created by fabrication techniques and/or by process induced strain, as described in FIG. 5 . The curvature of the first and/or second curved surfaces can also be dynamically adjusted by applying an external electric field (adjusting the carrier concentration), applying a mechanical force (via the piezoelectric effect) or using MEMs. 6A-8B provide example techniques for dynamically adjusting the curvature of a curved surface.

Photonic integrated circuits may include one or more of the optical devices disclosed in this disclosure. Photonic integrated circuits with multiple optical devices can be used, for example, in image sensing applications. Figure 4 provides an exemplary photonic integrated circuit with multiple refractive elements for filtering different wavelengths of light. Similarly, photonic integrated circuits with multiple optical devices can be formed. Each optical device may have one or more refractive elements and/or one or more substructures to filter and/or refract light of different wavelengths. Different optical devices may have different sizes or forms of refractive elements. Different optical devices can be fabricated by applying different masks, depositing different materials, depositing layers of different thicknesses, and/or etching different patterns of photonic crystal patterns, gratings, or other periodic substructures. For example, the refractive elements in two or more regions may have the same or different radii of curvature. In some implementations, one or more optical devices of a photonic integrated circuit may include only substructures without refractive elements. Substructures can be made of different periods, sizes, materials form. The substructures can be formed on a single substrate. The substrate may be planar, or have curvature as a whole. In some examples, the photonic integrated circuit may form a pixel, and each optical device may form a sub-pixel capable of transmitting a specific wavelength range.

10 shows a flowchart of an exemplary process 1000 for fabricating an optical device. Process 1000 may be used to fabricate optical device 910 in FIG. 1 . Process 1000 may be performed in the order shown, or it may be performed in a different order than shown. Some steps in process 1000 are optional. Process 1000 may be performed by a system including data processing equipment, such as one or more computers controlling one or more equipment that performs fabrication steps.

Process 1000 may be performed using one or more lithography, etching, and/or thin film deposition techniques. For example, lithography techniques, such as projection lithography, electron beam lithography, contact lithography, or any other suitable lithography technique, may be used to form optical devices. Etching techniques, such as dry etching, wet etching, or any other suitable etching technique, can be used to fabricate components of the optical device. Thin film deposition techniques such as chemical vapor deposition, plasma enhanced chemical vapor deposition, sputtering, or any other suitable thin film deposition technique may be used to deposit one or more layers of material on the optical device.

According to process 1000, semiconductor material is removed from a semiconductor substrate to form a first curved surface (1002). The first curved surface forms the surface of a refractive element of the optical device (eg, refractive element 930 in Figure 9). For example, the substrate 902 may be etched to form the first curved surface 904 . The first curved surface may be formed according to a predetermined radius of curvature. The radius of curvature may depend on the refractive index of the semiconductor material and/or the equivalent refractive index required by the optical device. Examples of semiconductor substrates include, but are not limited to, silicon wafers or silicon-on-insulator wafers. Grayscale light can be used cover to form the first curved surface. The first curved surface may also be formed by process induced strain. The curvature of the first curved surface can also be dynamically adjusted by applying an external electric field, applying mechanical force, and/or using MEMS.

A bonding layer is formed on the first layer (1004). For example, a bonding layer can be deposited on the first layer by thin film deposition techniques. For example, bonding layer 924 is deposited on first curved surface 904 of structure 908 in FIG. 9 . The optical thickness of the bonding layer may correspond to the focal point of the refractive element of the optical device. For example, the refractive index and/or thickness of the bonding layer can be set such that the optical device focuses (or defocuss) the refracted electromagnetic radiation in a predetermined point.

Semiconductor material is removed from the semiconductor substrate to form a second curved surface (1006). For example, semiconductor material 922 in structure 908 is etched to form second curved surface 934 in optical device 910 . The second curved surface and the first curved surface may be formed by the same or different techniques. The second curved surface can be formed by a grayscale mask or by process induced strain. The second curved surface can be formed according to a predetermined radius of curvature. The radius of curvature may depend on the refractive index of the semiconductor material and/or the desired equivalent refractive index of the optical device. The curvature of the second curved surface can be dynamically adjusted by applying an external electric field, applying mechanical force, and/or using MEMS.

The first curved surface may be symmetrical to the second curved surface, or the first curved surface and the second curved surface may have different shapes. The first and second curved surfaces may or may not have the same focal length. The first and second curved surfaces form two surfaces of a refractive element of the optical device. In some implementations, the refractive element is set to have a predetermined focal length. In some examples, the radius of curvature of the first and/or second curved surfaces depends on the focal length of the refractive element.

Semiconductor material is selectively removed from the first and/or second curved surfaces to form substructures (1008). For example, the substructure 105 is formed on the refractive element 101 by etching selected areas of the refractive element 101 . A set of substructures may be configured periodically. The two or more substructures may have different shapes and/or sizes. For example, periodic substructure 125 has a different size than periodic substructure 127 . One or more of the substructures may have at least one sub-wavelength dimension. The sub-wavelength dimension is smaller than the bandgap wavelength of the semiconductor material forming the refractive element. For example, the substructures 127 may have sub-wavelength diameters. One or more of the substructures may be filled with a different material than the semiconductor material of the refractive element. For guided wave modal resonance effects, the index of refraction of the filler material may be higher than the index of refraction of the refractive element.

100: Photonic Integrated Circuits

101: Refractive element

103: Surface

105: Periodic Structure

107: Optical Media

111: Light

113: Focus beam

119: External medium

Claims (20)

A method of fabricating an optical device, comprising: removing semiconductor material from a semiconductor substrate to form a first curved surface of the optical device, the semiconductor substrate having a bandgap wavelength, the bandgap wavelength being associated with a bandgap energy of the semiconductor material; forming a bonding layer on the first curved surface, wherein forming the bonding layer includes depositing bonding material on the first curved surface; removing the semiconductor material from the semiconductor substrate to form a second curved surface of the optical device, the second curved surface is opposite to the first curved surface of the optical device; and selectively removing semiconductor material from one of the first curved surface and the second curved surface of the optical device to form one or more sub-wavelength structures, wherein the sub-wavelength At least one of the structures has at least one dimension smaller than the bandgap wavelength of the semiconductor substrate, wherein the optical device is configured to refract incident electromagnetic radiation at a first wavelength range, and/or filter a second wavelength range of electromagnetic radiation, the first wavelength range is infrared wavelengths greater than the bandgap wavelength, and the second wavelength range is less than the bandgap wavelength; wherein the semiconductor material has a bandgap energy of 1.2 electron volts to 1.7 electron volts. The method of claim 1, wherein the first wavelength ranges from 800 nm to 2000 nm. The method of claim 1, wherein the second wavelength ranges from 400 nm to 800 nm. The method of claim 1, wherein the optical device is a lens. The method of claim 1, further comprising disposing an optical element relative to the bonding layer so that the optical element receives electromagnetic radiation refracted by the optical device. The method of claim 5, wherein the optical element is an active element configured to adjust the first wavelength range and/or the second wavelength range, wherein the adjustment comprises absorption or emission corresponding to adjusting the wavelength in the wavelength range Electromagnetic radiation. The method of claim 5, wherein the optical element is selected from the group consisting of a photodetector, a sensor, a light emitting diode and a laser. The method of claim 5, wherein the optical element comprises silicon germanium. The method of claim 1, further comprising: forming one or more structures on the second curved surface of the optical device, the one or more structures forming an optical element, the optical element being selected from a light A group consisting of a detector, a sensor, a light emitting diode and a laser. The method of claim 1, wherein the optical device is a first optical device, the bonding layer is a first bonding layer, and the method further comprises: depositing a bonding material on the second curved surface to The second curved surface of the optical device forms a second bonding layer; and a second optical device is coupled to the second bonding layer and is opposite to the first optical device; wherein, the first optical device and the second optical device The device is configured to collectively refract incident electromagnetic radiation having a third wavelength range, and/or filter electromagnetic radiation having a fourth wavelength range, wherein the third wavelength range is a sub-range of the first wavelength range, and/or Or the fourth wavelength range is a sub-range of the second wavelength range. The method of claim 10, wherein the second optical device includes at least one curved surface including one or more sub-wavelength structures, wherein the at least sub-wavelength structures have at least one dimension that is smaller than a bandgap wavelength of the semiconductor structure. The method of claim 10, wherein the second bonding layer has an optical thickness sufficient to focus electromagnetic radiation refracted by the first optical device to the second optical device. The method of claim 1, wherein the second curved surface has the same radius of curvature as the first curved surface. The method of claim 1, wherein at least one of the first curved surface and the second curved surface is formed using a grayscale mask. The method of claim 1, wherein removing the semiconductor material from the semiconductor substrate comprises etching the semiconductor substrate. The method of claim 1, wherein the one or more subwavelength structures comprise a plurality of periodically arranged subwavelength structures. The method of claim 1, wherein the bonding layer comprises a bonding material selected from the group consisting of an oxide, a nitride and a metal. The method of claim 1, wherein forming the bonding layer further comprises planarizing the bonding layer by chemical mechanical polishing. The method of claim 1, wherein the optical device has an equivalent refractive index that is dynamically adjustable in response to an applied electric field. The method of claim 1, wherein the bonding layer has an optical thickness corresponding to a focal length of the optical device.

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