US20210215609A1 - Apparatus, a Handheld Electronic Device, and a Method for Carrying Out Raman Spectroscopy - Google Patents

Apparatus, a Handheld Electronic Device, and a Method for Carrying Out Raman Spectroscopy Download PDF

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US20210215609A1
US20210215609A1 US16/743,742 US202016743742A US2021215609A1 US 20210215609 A1 US20210215609 A1 US 20210215609A1 US 202016743742 A US202016743742 A US 202016743742A US 2021215609 A1 US2021215609 A1 US 2021215609A1
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Prior art keywords
laser
excitation radiation
optoelectronic
transistor
raman
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English (en)
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Ann Russell
Hubert Halbritter
Christoph Goeltner
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Ams Osram International GmbH
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Osram Opto Semiconductors GmbH
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Priority to US16/743,742 priority Critical patent/US20210215609A1/en
Assigned to OSRAM OPTO SEMICONDUCTORS GMBH reassignment OSRAM OPTO SEMICONDUCTORS GMBH ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: HALBRITTER, HUBERT, RUSSELL, Ann, GOELTNER, CHRISTOPH
Priority to US17/758,549 priority patent/US20230041170A1/en
Priority to PCT/EP2020/086426 priority patent/WO2021144107A1/en
Priority to CN202080093117.2A priority patent/CN114981643A/zh
Priority to DE112020006527.8T priority patent/DE112020006527T5/de
Publication of US20210215609A1 publication Critical patent/US20210215609A1/en
Abandoned legal-status Critical Current

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
    • G01N21/65—Raman scattering
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28—Investigating the spectrum
    • G01J3/44—Raman spectrometry; Scattering spectrometry ; Fluorescence spectrometry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
    • G01J3/00—Spectrometry; Spectrophotometry; Monochromators; Measuring colours
    • G01J3/28—Investigating the spectrum
    • G01J3/44—Raman spectrometry; Scattering spectrometry ; Fluorescence spectrometry
    • G01J2003/4424—Fluorescence correction for Raman spectrometry
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/62—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light
    • G01N21/63—Systems in which the material investigated is excited whereby it emits light or causes a change in wavelength of the incident light optically excited
    • G01N21/65—Raman scattering
    • G01N2021/653—Coherent methods [CARS]
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2201/00—Features of devices classified in G01N21/00
    • G01N2201/02—Mechanical
    • G01N2201/022—Casings
    • G01N2201/0221—Portable; cableless; compact; hand-held
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2201/00—Features of devices classified in G01N21/00
    • G01N2201/06—Illumination; Optics
    • G01N2201/061—Sources
    • G01N2201/06113—Coherent sources; lasers
    • G01N2201/0612—Laser diodes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2201/00—Features of devices classified in G01N21/00
    • G01N2201/06—Illumination; Optics
    • G01N2201/069—Supply of sources
    • G01N2201/0696—Pulsed
    • G01N2201/0697—Pulsed lasers

Definitions

  • the present disclosure relates to an apparatus for carrying out Raman spectroscopy on a sample.
  • the present disclosure relates to a handheld electronic device and a method for carrying out Raman spectroscopy on a sample.
  • the chemistry of samples can be probed by exposing a sample to laser light and by collecting the inelastically backscattered light.
  • Light at a wavelength of the laser light in the backscattered light also referred to as Rayleigh scattering
  • Rayleigh scattering can be filtered out using, for example, a high pass filter.
  • the remaining red shifted light also called Raman scattered light
  • This method of probing matter is a common way to obtain a unique Raman spectrum with greater accuracy than broadband spectroscopy and it can be used to reliably identify the chemical makeup and structure of the matter in question.
  • a problem can be the occurrence of fluorescence light which can be several orders of magnitude greater than the Raman signal, and the fluorescence light can obfuscate the identifying information.
  • a repeatable, portable and affordable apparatus and method is sought to carry out Raman spectroscopy on a sample, for example to identify pesticides on food, drugs in urine and contamination in liquid milk.
  • Embodiments of the invention seek to provide an apparatus for carrying out Raman spectroscopy, such as time-gated Raman spectroscopy, on a sample.
  • the apparatus comprises at least one optoelectronic laser for providing excitation radiation to the sample, the excitation radiation being generated by an electric current which flows through the at least one optoelectronic laser during operation of the apparatus, and a transistor, such as a GaN FET, for modulating the electric current flowing through the at least one optoelectronic laser, to thereby switch on and off the generation of the excitation radiation.
  • the at least one optoelectronic laser can be one or more optoelectronic lasers, and the electric currents that flow through the optoelectronic lasers can be different from each other.
  • the transistor can be employed to control each of the electric currents simultaneously.
  • the electric current through an optoelectronic laser causes the generation of coherent laser light.
  • FET field effect transistor
  • the transistor can modulate the electric current such as to switch intermittently an optoelectronic laser between on operational mode and a non-operational mode.
  • the laser can emit pulses of excitation radiation in the operational mode.
  • the electric current is then at a level at which the pulses of excitation radiation can be generated.
  • the non-operational mode the electric current is at a level where light emission does not occur.
  • Raman measurements on a sample will lead to fluorescence when trying to collect a Raman signal.
  • the concept of time-gated Raman scattering is related to the aspect of collecting Raman scattering prior to fluorescence.
  • laser pulses with a time duration in the pico-second range can be used to stimulate the immediate Raman scattering prior to the fluorescing portion saturating a detector, which is used to detect the Raman light.
  • Raman scattering of a sample is proportional to 1/ ⁇ circumflex over ( ) ⁇ 4, wherein ⁇ denotes the wavelength of the excitation radiation. It can for example be possible to use direct transition 520 nm picosecond laser light to stimulate intense Raman scattering without damaging a sample.
  • the at least one optoelectronic laser is configured to provide single mode operation which is wavelength stabilized, and/or to maintain a wavelength in a robust way and for a long time, and/or to provide excitation radiation with a long coherence length.
  • the at least one optoelectronic laser comprises a semiconductor based lasing device, in particular a laser diode.
  • the laser diode emits green light, for example at a wavelength of 520 nm.
  • the optoelectronic laser can be a DBR or DFB laser diode or a VCSEL.
  • a distributed Bragg reflector is a periodic structure, which is formed of alternating dielectric layers having different indices of refraction.
  • a DBR might be used to achieve nearly total reflection within a range of frequencies, wherein the range of frequencies includes the frequencies of the excitation radiation of the laser.
  • the DBR can be formed by use of dielectric layers that are included in the layer structure of the laser.
  • a distributed feedback laser diode can be a type of laser diode, quantum cascade laser or optical fiber laser where the active region of the device contains a periodically structured element or diffraction grating.
  • a VCSEL is a type of semiconductor laser diode that emits laser light in a direction, which is perpendicular to the top surface of the laser diode.
  • the at least one optoelectronic laser is a DFB or DBR laser diode.
  • the at least one optoelectronic laser comprises a laser diode and at least one of an external cavity and a wavelength multiplexer.
  • the at least one optoelectronic laser can be two, three or more lasers.
  • each laser can be a laser diode that provides laser light at a defined wavelength.
  • the light from the laser diodes can be coupled, for example by use of a combiner, into a single fiber or into a single, preferably collimated, beam.
  • a combiner For example, using three laser diodes, one emitting red light, one emitting green light, and one emitting blue light, a laser beam including the red, green and blue light can be obtained.
  • an RGB laser beam could be obtained.
  • the transistor is a Gallium Nitride field effect transistor (GaN FET).
  • GaN FET Gallium Nitride field effect transistor
  • the GaN FET can be configured as a high-power GaN FET.
  • the GaN FET can be configured to allow picosecond rise times, thereby enabling the optoelectronic laser to generate pulses with a time duration in the pico-second range.
  • the transistor is embedded in a substrate, wherein an optoelectronic laser is arranged on the substrate.
  • the optoelectronic laser and the transistor can be accommodated in a single package.
  • the transistor can be placed directly underneath the optoelectronic laser, basically none or only very short wiring is required to connect electrically the transistor to the optoelectronic laser.
  • the transistor can be electrically coupled to the optoelectronic laser at least in substance without using bond wires. This allows short switching times of a voltage provided by use of the transistor to the optoelectronic laser.
  • a change in voltage (V) over time (t), dV/dt can be larger than 100 V/s.
  • dV/dt For an optoelectronic laser with approximately 8V forward bias, this can for example result in a turn on and off time of 160 ps.
  • the at least one optoelectronic laser and optionally the transistor can be arranged in a package.
  • a connecting pad can be placed under the at least one optoelectronic laser, and the transistor can be placed on or beyond the connecting pad.
  • the at least one optoelectronic laser in the package is preferably a DFB or DBR laser diode.
  • the GaN FET has an electric contact and an optoelectronic laser has an electric contact, and the electric contact of the transistor is directly coupled electrically to the electric contact of the optoelectronic laser. Basically no bond wire is used to connect the electric contacts of the transistor and the optoelectronic laser.
  • the transistor can be an FET transistor which has a drain electrode.
  • the optoelectronic laser can be a laser diode which has a cathode and an anode.
  • the drain of the FET transistor can be directly coupled to the cathode of the laser diode. This allows for short switching times.
  • a driver is configured to operate the transistor such as to cause the optoelectronic laser to cause the generation of pulsed excitation radiation.
  • the driver can provide a control signal to the transistor.
  • the control signal can also be called frame sync signal.
  • the driver can provide the control signal to the gate of the transistor.
  • the cathode of the laser diode can be connected to the drain of the FET transistor.
  • the application of a voltage to the gate by use of the control signal allows modulating the electric current through the laser diode.
  • the control signal can for example be a square-wave signal.
  • the at least one optoelectronic laser can be configured to generate pulsed excitation radiation, with pulses having a time duration of less than 100 picosecond.
  • the pulse duration can therefore correspond to the full width at half of the maximum of the time signal of a pulse.
  • the at least one optoelectronic laser can be operated to generate pulses of excitation radiation, wherein each pulse has for example a time duration of less than 500 ps or less than 500 fs.
  • the apparatus comprises a temperature sensor configured to monitor a temperature of an optoelectronic laser.
  • a change in temperature can cause a wavelength shift in the emitted excitation radiation from the optoelectronic laser. Such a wavelength shift can thus be accounted for by monitoring the temperature.
  • the apparatus comprises a Bragg grating.
  • the Bragg grating can be helpful in producing laser light with a long coherence length.
  • the Bragg grating can be integrated into a package, which further includes the optoelectronic light source and the transistor.
  • a package may have, but does not require a non-hermetic facet coating, which is preferably used in conjunction with DFB or DBR laser diodes.
  • the apparatus comprises a spectrometer for analyzing Raman light scattered from the sample in response to exposing the sample to the excitation radiation, the Raman light comprising one or more spectral components, and wherein the spectrometer comprises a diffraction element configured to split the Raman light into its spectral components.
  • the diffraction element can divide the Raman light into its spectral components and thereby spread the Raman light into an optical spectrum of spatially separated wavelength components.
  • the spectrometer can further comprise a focusing lens system for directing at least a portion of the spectrum to a detector, such as a one- or two-dimensional array detector.
  • the spectrometer can comprise an entrance slit.
  • the slit can help to tighten the window of observation for Raman scattering prior to fluorescence, thereby eliminating fluorescence, which will prevent collection of the Raman signal.
  • the diffraction element comprises at least one of the following: a diffraction grating, a photonic crystal, and a plasmonic Fabry Perot filter.
  • the apparatus includes a scanning mirror in a light path of the Raman scattered light, in particular between a spectrometer and a detector, wherein the transistor is operated based on a control signal, and wherein the scanning mirror is also operated based on the control signal.
  • Embodiments of the invention relate to a handheld electronic device which comprises a housing, and an apparatus with at least one optoelectronic laser for providing excitation radiation to the sample, the excitation radiation being generated by an electric current which flows through the at least one optoelectronic laser during operation of the apparatus, and the apparatus further comprising a transistor for modulating the electric current flowing through the at least one optoelectronic laser, to thereby switch on and off the generation of the excitation radiation and the apparatus being arranged in the housing of the handheld electronic device.
  • the handheld electronic device is a smartphone or a tablet.
  • Embodiments of the invention also relate to a method of carrying out Raman spectroscopy on a sample, wherein the method comprises providing an apparatus in accordance with at least some of the embodiments as described herein, and operating the transistor, for example a GaN FET, such as to cause the optoelectronic laser to generate pulses of excitation radiation.
  • the transistor for example a GaN FET, such as to cause the optoelectronic laser to generate pulses of excitation radiation.
  • the sample is not a part of the claimed apparatus, handheld electronic device or method. Rather, the sample is the piece of matter or a volume of gas or liquid on which Raman spectroscopy is carried out.
  • the electric current flows through the optoelectronic laser during operation of the laser and thus during the intended use of the apparatus or handheld electronic device.
  • a handheld electronic device can comprise an apparatus for carrying out Raman spectroscopy on a sample using time gated Raman spectroscopy via direct modulation of a laser diode and MEMS mirrors plus slits to image Raman scattering prior to fluorescence as well as various instantiations using Bragg gratings (single wavelength laser) versus multiwavelengths (surface relief gratings).
  • MEMS mirrors plus a double slits and various types of detectors filter array, electrostatically charged deep well large pixels, Chromation device, etc.
  • the use of double slits with a MEMS mirror prevents saturation of the Raman signal by the following fluorescence.
  • an apparatus for carrying out Raman spectroscopy comprises a GaN FET, and a directly modulated (by the GaN FET), visible DFB or DBR laser which is used to generate laser pulses fast enough (for example ⁇ 200 ps) to capture Raman scattering prior to fluorescence.
  • Tandem slits and/or MEMS mirrors can be used to image while a laser modulation signal is used to as a frame sync.
  • the laser modulation signal can be provided by a driver which drives the transistor based on the laser modulation signal.
  • the use of small laser diodes, MEMS mirrors, and linear arrays as detectors can mean that the apparatus can fit into a handheld device, such as a cell phone, smart phone, tablet, etc.
  • FIG. 1 shows a block diagram of an exemplary embodiment of an apparatus
  • FIG. 2 shows schematically an exemplary embodiment of a handheld electronic device
  • FIG. 3 illustrates schematically a functional approach for carrying out time-gated Raman spectroscopy
  • FIG. 4 illustrates schematically a further functional approach for carrying out time-gated Raman spectroscopy
  • FIG. 5 shows schematically a further exemplary embodiment of an apparatus
  • FIG. 6 shows schematically a further exemplary embodiment of an apparatus
  • FIG. 7 shows schematically a further exemplary embodiment of an apparatus
  • FIG. 8 shows schematically yet a further exemplary embodiment of an apparatus.
  • the apparatus 101 as shown in FIG. 1 can be used for carrying out Raman spectroscopy, such as time-gated Raman spectroscopy, on a sample 103 , which is not part of the apparatus 101 .
  • the apparatus 101 comprises an optoelectronic laser 105 for providing excitation radiation to the sample 103 .
  • the sample 103 can be arranged, for example by a user of the apparatus, such that it can be exposed to the excitation radiation, which usually consists of or comprises laser light.
  • the apparatus 101 further comprises a transistor 107 , for example a Gallium Nitride field effect transistor, for modulating an electric current, which flows during operation of the apparatus 101 through the optoelectronic laser 105 and which causes the generation of the excitation radiation.
  • a transistor 107 for example a Gallium Nitride field effect transistor, for modulating an electric current, which flows during operation of the apparatus 101 through the optoelectronic laser 105 and which causes the generation of the excitation radiation.
  • the apparatus 101 can be incorporated into a handheld electronic device, such as a cell phone, a smartphone or a tablet computer.
  • the handheld electronic device 201 of FIG. 2 comprises such an apparatus having an optoelectronic laser 203 , for example a DFB or DBR laser diode, for providing excitation radiation 207 to sample 205 , which is arranged outside a housing 209 of the handheld electronic device 201 .
  • an optoelectronic laser 203 for example a DFB or DBR laser diode
  • the excitation radiation 207 can have an average power of more than wo mW.
  • the excitation radiation can comprise green laser light, and the excitation radiation can include one or more wavelengths. For example, two wavelengths, one in the visible and one in the infrared, can help to obtain a better confirmation of the Raman signal.
  • the apparatus 201 also comprises a transistor 211 , such as a GaN FET, for modulating an electric current, which can flow through the optoelectronic laser 203 to cause the generation of the excitation radiation 207 .
  • a transistor 211 such as a GaN FET
  • the apparatus 201 also includes an objective 213 , for example in form of a focusing lens system which can comprise a plano convex lens.
  • the objective 213 can focus the excitation radiation 207 to a spot 215 outside the housing 209 .
  • the sample 207 is placed such that the spot 215 is located on the surface of the sample 205 .
  • the objective 213 also serves to collect light scattered from the sample 205 .
  • the scattered light includes Raman scattered light with wavelengths that are different from the wavelengths of the excitation radiation 207 .
  • a high pass filter 217 is configured to reflect the excitation radiation 207 from the optoelectronic laser 203 and to guide the excitation radiation 207 to the objective 213 .
  • the high pass filter 217 is furthermore transparent for light with wavelengths, which are longer than the wavelengths of the excitation radiation 207 .
  • the red shifted portion of the Raman scattered light can pass the high pass filter 217 and it can be focused through a slit 219 of a spectrometer 221 .
  • the spectrometer 221 comprises a diffraction element 223 , such as a diffraction grating, a photonic crystal, or a plasmonic Fabry Perot filter, which spatially splits the Raman light into its spectral components.
  • the diagram 15 as shown in FIG. 3 illustrates a time-gated Raman spectroscopy process.
  • the diagram 15 is also related to the setup of FIG. 5 , which will be described further below in more detail.
  • an optoelectronic laser is operated such as to provide laser pulses.
  • the laser can be a low power (for example with an average power of 100 mW) DFB or DBR laser diode.
  • a laser diode 9 is shown in FIG. 5 .
  • a VCSEL and a green laser such as a direct transition green laser, could be used to provide laser light.
  • the VCSEL can for example be configured to emit light in the infrared.
  • a control signal (frame sync signal) 11 is generated in 303 , which is used for controlling the operation of the laser 9 .
  • the signal 11 can also trigger the flashing of a detector array, for example, a linear array, from existing charges according to 305 .
  • the generated laser pulse it is reflected off the filter 2 (see FIG. 5 ) according to 307 .
  • the pulse travels through objective 1 and hits sample 215 (see also FIG. 5 ).
  • Light which includes Raman light is back scattered and collected by the objective 1 according to 311 of FIG. 3 .
  • the red-shifted Raman light passes the high pass filter 2 , and lens 3 focuses the light through slit 4 into the spectrometer according to 313 of FIG. 3 .
  • the Raman light further passes through collimation and aberration correction optics 5 and diffracting element 6 which spatially splits the Raman light into its spectral lines. At least some of the spectral lines in the Raman light are imaged by use of imaging lens 7 on the detector 8 .
  • a shutter 14 is placed in front of the detector 8 and the shutter 14 is operated based on the frame sync signal 11 by use of which the laser 9 is operated. As indicated in 315 , the frame sync signal 11 allows the detector to collect the spectral lines of the Raman light by causing the opening of the shutter 14 .
  • Fluorescence is generated by the sample according to 317 with a time delay with regard to the Raman light. Fluorescence light can arrive at the detector 8 according to 319 , but data about the spectral lines in the Raman signal have already been collected due to the use of the frame sync signal as shown in 315 which has in the meantime closed the shutter 14 . Thus, the detector 8 will not collect fluorescence light.
  • the data collected in 315 will be further processed in 312 , for example by use of an artificial intelligence (AI) system or the like, in order to identify the spectral lines and/or the sample.
  • AI artificial intelligence
  • a result is output in 323 .
  • the diagram 25 as shown in FIG. 4 differs from the diagram 15 in FIG. 3 by block 401 .
  • MEMS Micro-Electro-Mechanical System
  • the use of a MEMS scanning mirror 47 allows reduction of exposure time and prevents saturation of the linear array 8 , trimming out the undesirable fluorescence in a different manner than shutter 14 .
  • tandem scanning slit microscope is for example described in the scientific publication by Stephen C. Baer “Tandem Scanning Slit Microscope”, Proc. SPIE 1139, Optical Storage and Scanning Technology, (28 Sep. 1989); https://doi.org/10.1117/12.961780.
  • a tandem scanning mirror can be used similar to an epi-illumination tandem scanning pinhole microscope using slits instead.
  • Epi-illumination is an operational mode used in microscopy in which illumination and detection occurs from the same side of the sample.
  • the mirror image of one field aperture is coincident with the other, where an opaque mirror is used at the edge of the plane defined by the viewing slit and the center of the objective aperture.
  • the mirror can then reflect light from the illuminated slit onto just one semicircle of the objective aperture. The remaining semicircle can be used for projecting light from the specimen to the viewing slit.
  • Scanning can be accomplished by reciprocally rotating the two slits and the mirror.
  • MEMS can be used to achieve rotating movements.
  • the operation of optoelectronic laser 9 is controlled via GaN FET 10 .
  • the laser 9 comprises an anode A and a cathode C.
  • the anode A is connected to a voltage supply provided by a voltage source (not shown).
  • the cathode C is electrically connected to the drain D of transistor 10 .
  • the source S of transistor 10 is connected to ground gnd.
  • the control signal (frame sync signal) 11 is applied to the gate of transistor 10 .
  • the control signal 10 can for example be a square-wave signal, and it can be configured to rapidly switch the electric current that drives the laser 9 between a level at which lasing occurs and a level at which the laser 9 is not emitting light.
  • the control signal 10 is provided to the shutter 14 to open and close the shutter 14 in dependence on the control signal 14 .
  • the control signal 10 can be used to control the operation of the scanning mirror 47 .
  • the laser 9 is turned on and off using the GaN FET 10 , which can for example switch at dV/dt>100V/s.
  • the laser 9 can have an approximate 8V forward bias, a turn on and off time of 160 ps is then possible.
  • the laser 9 can be a low power laser, it will not require a high voltage rail.
  • the GaN FET 10 is well suited for these types of fast switching applications.
  • the generated pulses of the excitation radiation provided by the laser diode 9 is collimated using a lens 12 , which can produce a Gaussian beam which is desirable for accurate Raman scattering analysis.
  • the pulses of the excitation radiation are then condensed via objective 1 , also referred to as probe optics, for example by using a common low f-number optics.
  • the pulses of laser light can be focused down to a spot size of approximately 20 microns to stimulate Raman scattering on the sample 215 .
  • the backscattered light is mostly rejected at high pass filter 2 , which can be a dichroic mirror, except the red-shifted component of the Raman scattered light.
  • the high pass filter 2 can start at the laser wavelength of the pulses as provided by laser 9 , for example corresponding to a wavelength of 520 nm, 785 nm, 850 nm, or 940 nm.
  • Condensing lens 3 focuses the pulses of Raman light through slit 4 which determines the resolution of the system and optical throughput. For example, a 10-50 micron slit 4 is used to filter the signal.
  • the pulses of Raman light pass through collimation and aberration correction optics 5 , such as anachromat.
  • the expanded and somewhat collimated pulses pass through diffracting element 6 which can be a 2D photonic crystal or a volume Bragg grating, and it acts as a wavelength separator.
  • Imaging lens 7 directs the first order of the spatially separated lines of the Raman light towards detector 8 while avoiding the zero order.
  • the shutter 14 is used to prevent fluorescence light from saturating the detector 8 and the shutter 14 is operated based on the frame sync signal 11 .
  • detector 8 for example a linear array 8 such as a SiPM, SPAD, InGaAS detector, or cut filtered silicon with bias voltage applied.
  • the frame sync 11 can also be used to clear excess charges prior to Raman scattering being imaged on the detector 8 .
  • the linear array 8 can be a deep well, large pixel (for example 8 um ⁇ 8 um) linear array, and it can display an extremely tight form factor (8 mm ⁇ 1 mm).
  • a temperature sensor or TEC 13 can be used to monitor the laser diode temperature to account for wavelength shift of laser diode 9 .
  • the setup 55 provides multiple wavelengths of excitation radiation to sample 215 .
  • This can be realized by use of three lasers 9 , 58 , and 59 , each of which provides laser pulses at a particular wavelength.
  • Each laser 9 , 58 , and 59 is a laser diode and the cathode C of each laser diode is connected to the drain D of transistor 10 .
  • the control signal 11 is applied to gate G of transistor 10 to control the electric current through the laser diodes 9 , 58 , and 59 and, thus, to switch the lasers 9 , 58 , and 59 on and off.
  • the control signal 11 is also used to control the operation of the shutter 14 .
  • a blazed diffraction grating 56 is further used to diffract any wavelength. For example, consider a 520 nm laser 9 , a 785 nm laser 58 , and an infrared laser 59 providing pulses at 1064 nm.
  • the control signal 11 is again used along with a shutter 14 and linear array 8 .
  • the Raman scattered light from the sample 215 under investigation can be split into its spectral lines by means of a prism or optical grating to fall onto a linear detector grid.
  • the respective spectrum can be derived from the light intensity on each of the linearly aligned detector elements of detector 8 .
  • the Raman light is directed to a sensor array, where each sensitive element or pixel is using a unique filter that only allows a specified narrow waveband to reach the sensor element. In this way, a diffraction element is not required.
  • the number of pixels and the bandwidth of each corresponding filter in front of each pixel determine the spatial resolution of the detected spectrum.
  • the setup 65 as shown in FIG. 8 includes double slits 46 and 48 as well as scanner 47 instead of the shutter 14 as used in setup 55 of FIG. 7 .
  • the control signal 11 is used to control operation of the scanner 47 , which can be a scanning mirror or a MEMS scanning mirror.
  • a multiplexing waveguide can also be utilized. The waveguide can be used for compactly combining multiple wavelengths such as those used, for example, in communication servers.

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PCT/EP2020/086426 WO2021144107A1 (en) 2020-01-15 2020-12-16 An apparatus, a handheld electronic device, and a method for carrying out raman spectroscopy
CN202080093117.2A CN114981643A (zh) 2020-01-15 2020-12-16 用于执行拉曼光谱法的设备、手持电子装置和方法
DE112020006527.8T DE112020006527T5 (de) 2020-01-15 2020-12-16 Ein apparat, eine tragbare elektronische vorrichtung und ein verfahren zur durchführung von raman-spektroskopie

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WO2021144107A1 (en) 2021-07-22

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