PATENT DOCUMENT

Publication Number: US-10697830-B1
Application Number: US-201715690145-A
Country: US
Kind Code: B1

Title: Multicomb light source and spectrometer

Abstract:
A comb light source and spectrometer is disclosed. The comb light source and spectrometer can include a plurality of light emitters, where each light emitter can be configured to emit light included in a plurality of wavelength bands. Each wavelength band can be separated from an adjacent wavelength band by a noise band. Due to the separated wavelength bands for a light emitter, any signal received outside of the one or more wavelength bands can originate from noise (e.g., drift, ambient light, electrical noise), thereby enhancing signal analysis and noise rejection. In some examples, the comb light emitters can be activated sequentially such that a plurality of wavelengths across a spectrum can be measured. In some examples, the resolution and the number of spectral lines in the comb light source can be tuned by changing the properties of the quantum dots and/or increasing the number of comb light emitters.

Claims:
What is claimed is: 
     
       1. A spectrometer comprising:
 a plurality of light emitters configured to emit a plurality of wavelengths of light across a spectrum, each light emitter configured to emit light in a plurality of wavelength bands, each of the plurality of wavelength bands separated from each of the other of the plurality of wavelength bands by a noise band comprising one or more wavelengths, wherein at least two of the plurality of light emitters include different wavelengths bands; and 
 one or more detectors configured to detect a reflection of light emitted by the plurality of light emitters and configured to generate one or more signals indicative of the reflection of light. 
 
     
     
       2. The spectrometer of  claim 1 , further comprising:
 a plurality of sets of first openings, each set coupled to one of the plurality of light emitters, wherein each set comprises light emitters having different optical properties; and 
 one or more second openings coupled to the one or more detectors, wherein the plurality of sets of first openings forms a ring and the one or more second openings are located in a center of the ring. 
 
     
     
       3. The spectrometer of  claim 1 , further comprising:
 one or more first openings, each first opening coupled to one of the plurality of light emitters, 
 one or more second openings, each second opening coupled to the one or more detectors, 
 wherein the one or more first openings and the one or more second openings are interleaved. 
 
     
     
       4. The spectrometer of  claim 3 , wherein the one or more first openings and the one or more second openings alternate. 
     
     
       5. The spectrometer of  claim 1 , wherein the plurality of wavelength bands of adjacent light emitters include a same wavelength. 
     
     
       6. The spectrometer of  claim 1 , further comprising:
 a plurality of openings configured to allow light to pass through; and 
 a waveguide configured to optically couple at least one of the plurality of light emitters to at least one of the plurality of openings. 
 
     
     
       7. The spectrometer of  claim 6 , wherein the waveguide is one or more of an optical fiber and a silicon photonics chip. 
     
     
       8. The spectrometer of  claim 6 , wherein the waveguide is coupled to at least two of the plurality of light emitters. 
     
     
       9. The spectrometer of  claim 6 , wherein the waveguide comprises a plurality of waveguides, and wherein the waveguide is coupled to one of the plurality of light emitters. 
     
     
       10. The spectrometer of  claim 1 , wherein the spectrometer is capable of measuring multiple wavelengths at a same time. 
     
     
       11. The spectrometer of  claim 1 , wherein the spectrometer is capable of measuring multiple wavelengths without spatial movement. 
     
     
       12. The spectrometer of  claim 1 , wherein the spectrometer excludes a filter. 
     
     
       13. The spectrometer of  claim 1 , wherein a number of the plurality of wavelength bands is equal to a number of the plurality of light emitters multiplied by a number of the one or more detectors, the spectrometer further comprising:
 one or more filters optically coupled to the one or more detectors, wherein a number of the one or more filters is equal to the number of the one or more detectors. 
 
     
     
       14. The spectrometer of  claim 1 , wherein a separation distance between each light emitter and an optically coupled detector is the same. 
     
     
       15. The spectrometer of  claim 1 , wherein at least one of the one or more detectors is configured to detect a reflection of at least two of the plurality of light emitters. 
     
     
       16. The spectrometer of  claim 1 , further comprising:
 a processor capable of: 
 receiving the one or more signals from the one or more detectors, 
 determining one or more properties of a sample using a portion of the one or more signals. 
 
     
     
       17. The spectrometer of  claim 1 , wherein at least one of the plurality of light emitters includes a plurality of quantum dots, each quantum dot configured to emit light included in one wavelength band, separate and distinct from the wavelength bands of the other of the plurality of quantum dots. 
     
     
       18. The spectrometer of  claim 17 , wherein each of the plurality of quantum dots has a size different from the other of the plurality of quantum dots, the size associated with the one wavelength. 
     
     
       19. The spectrometer of  claim 18 , wherein the at least one of the plurality of light emitters includes a plurality of layers, each of the plurality of layers including one or more of the plurality of quantum dots having a same size.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application No. 62/381,905 filed Aug. 31, 2016, the entire disclosure of which is herein incorporated by reference for all purposes. 
    
    
     FIELD 
     This relates generally to light sources and spectrometer systems, and more specifically to a comb light source and spectrometer capable of emitting a spectrum of wavelengths. 
     BACKGROUND 
     Fourier transform spectroscopy and broadband light sources can be used for measuring sample properties at a spectrum of wavelengths. The Fourier transform spectroscopy can include a moving mirror that can create a path length difference in one light beam relative to another. The two light beams can recombine, and the resultant interferogram can be formed based on interference. The Fourier transform of the interferogram can be used to determine the spectral absorbance (or transmittance). 
     Although a broadband light source (e.g., white light) spectrometer may be capable of measuring across a spectrum of wavelengths, a broadband source may not be able or may require complicated algorithms to discern between signals associated with one or more sample properties and noise. Furthermore, broadband source spectrometers may use temporal multiplexing, which can lead to long measurement times, moving parts, and/or a large number of light sources. Moreover, broadband spectrometers may use spatial multiplexing, which may lead to a large number of optical components and/or mechanically moving parts. Additionally, broadband source spectrometers may not be capable of resolving specific wavelengths. A spectrometer and light source capable of measuring across a spectrum of wavelengths and capable of discerning between signal associated with one or more sample properties and noise may be desired. 
     SUMMARY 
     This relates to a comb light source and spectrometer. The comb light source and spectrometer can include a plurality of light emitters, where each light emitter can be configured to emit light included in a plurality of wavelength bands. Each wavelength band can be separated from an adjacent wavelength band by a noise band. Due to the separated wavelength bands for a light emitter, any signal received outside of the one or more wavelength bands can originate from noise (e.g., drift, ambient light, electrical noise), thereby enhancing signal analysis and noise rejection. In some examples, the comb light emitters can be activated sequentially such that a plurality of wavelengths across a spectrum can be measured. In some examples, the resolution and the number of spectral lines in the comb light source can be tuned by changing the properties of the quantum dots and/or increasing the number of comb light emitters. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  illustrates an exemplary Fourier transform spectrometer according to examples of the disclosure. 
         FIG. 1B  illustrates an exemplary method for operating the Fourier transform spectrometer according to examples of the disclosure. 
         FIG. 1C  illustrates an exemplary Fourier transform output according to examples of the disclosure. 
         FIG. 2A  illustrates an interface included in a comb spectrometer according to examples of the disclosure. 
         FIG. 2B  illustrates an exemplary comb output according to examples of the disclosure. 
         FIG. 3A  illustrates an exemplary comb spectrometer according to examples of the disclosure. 
         FIG. 3B  illustrates an exemplary method for operating a comb spectrometer according to examples of the disclosure. 
         FIG. 3C  illustrates an exemplary comb light source and spectrometer output according to examples of the disclosure. 
         FIG. 4A  illustrates an exemplary comb spectrometer including multiple waveguides according to examples of the disclosure. 
         FIG. 4B  illustrates an exemplary method for operating a comb spectrometer according to examples of the disclosure. 
         FIG. 4C  illustrates an exemplary configuration for a comb spectrometer interface according to examples of the disclosure. 
         FIGS. 5A-5C  illustrate cross-sectional views of exemplary comb light sources according to examples of the disclosure. 
         FIGS. 6A-6B  illustrate top and cross-sectional views of a QD filter according to examples of the disclosure. 
         FIG. 6C  illustrates exemplary spectral absorbance for QD step filters and the calculated transmittance according to examples of the disclosure. 
         FIG. 7A  illustrates a cross-sectional view of an exemplary QD filter according to examples of the disclosure. 
         FIG. 7B  illustrates a spectral output of an exemplary QD filter according to examples of the disclosure. 
         FIGS. 8A-8B  illustrate exemplary waveguide configurations according to examples of the disclosure. 
         FIG. 9  illustrates a top view of an exemplary configuration for a comb spectrometer interface according to examples of the disclosure. 
         FIG. 10  illustrates a top view of an exemplary configuration for a comb spectrometer interface according to examples of the disclosure. 
         FIG. 11A  illustrates a top view of an exemplary ring configuration for a comb spectrometer interface according to examples of the disclosure. 
         FIG. 11B  illustrates an exemplary method for operating a ring comb spectrometer interface according to examples of the disclosure. 
         FIGS. 12A-12B  illustrate top and cross-sectional views of an exemplary interleaved comb spectrometer according to examples of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     In the following description of examples, reference is made to the accompanying drawings in which it is shown by way of illustration specific examples that can be practiced. It is to be understood that other examples can be used and structural changes can be made without departing from the scope of the various examples. 
     Representative applications of methods and apparatus according to the present disclosure are described in this section. These examples are being provided solely to add context and aid in the understanding of the described examples. It will thus be apparent to one skilled in the art that the described examples may be practiced without some or all of the specific details. Other applications are possible, such that the following examples should not be taken as limiting. 
     Various techniques and process flow steps will be described in detail with reference to examples as illustrated in the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of one or more aspects and/or features described or referenced herein. It will be apparent, however, to one skilled in the art, that one or more aspects and/or features described or referenced herein may be practiced without some or all of these specific details. In other instances, well-known process steps and/or structures have not been described in detail in order to not obscure some of the aspects and/or features described or referenced herein. 
     Further, although process steps or method steps can be described in a sequential order, such processes and methods can be configured to work in any suitable order. In other words, any sequence or order of steps that can be described in the disclosure does not, in and of itself, indicate a requirement that the steps be performed in that order. Further, some steps may be performed simultaneously despite being described or implied as occurring non-simultaneously (e.g., because one step is described after the other step). Moreover, the illustration of a process by its depiction in a drawing does not imply that the illustrated process is exclusive of other variations and modification thereto, does not imply that the illustrated process or any of its steps are necessary to one or more of the examples, and does not imply that the illustrated process is preferred. 
     This disclosure relates to a comb light source and spectrometer. The comb light source and spectrometer can include a plurality of light emitters, where each light emitter can be configured to emit light included in a plurality of wavelength bands (e.g., a plurality of continuous wavelengths). Each wavelength band can be separated from an adjacent wavelength band by a noise band. Due to the separated wavelength bands for each comb light emitter, any light measured outside of the wavelength bands can originate from noise (e.g., drift, ambient light, and/or electrical noise). Signal analysis and noise rejection can be enhanced by limiting the emission wavelengths of a comb light emitter to the one or more wavelength bands. In some examples, the comb light emitters can be activated sequentially such that a plurality of wavelengths across a spectrum can be measured. In some examples, the resolution and the number of spectral lines in the comb light source can be tuned by changing the properties of the quantum dots and/or increasing the number of comb light sources. 
       FIG. 1A  illustrates an exemplary Fourier transform spectrometer, and  FIG. 1B  illustrates an exemplary method for operating the Fourier transform spectrometer according to examples of the disclosure. Spectrometer  100  can include light source  102 , collimator  104 , detector  110 , sample  120 , beamsplitter  130 , mirror  132 , mirror  134 , and controller  140 . 
     Light source  102  can emit multi-band or multi-wavelength light  150  towards collimator  104  (step  162  of process  160 ). Collimator  104  can be a component configured to focus and/or steer light (step  164  of process  160 ). Light  150  can be incident on beamsplitter  130 . Beamsplitter  130  can be any optical component configured to split a beam of light into multiple beams of light. For example, beamsplitter  130  can split light  150  into to multiple light beams: light  152  and light  154  (step  166  of process  160 ). 
     Light  152  can be directed towards mirror  132  (step  168  of process  160 ). Mirror  132  can be any type of optics capable of reflecting light towards sample  120 . In some examples, mirror  132  can be a stationary or fixed mirror. Light  154  can be directed towards mirror  134  (step  170  of process  160 ). Mirror  134  can be any type of optics capable of reflecting light towards beamsplitter  130 . In some examples, mirror  134  can be a moveable mirror. In some examples, mirror  134  can be configured for moving back and forth (e.g., longitudinal movement along a line) towards and away from light source  102  (step  172  of process  160 ). 
     Mirror  132  and mirror  134  can be configured such that the path length of light  152  can be different from the path length of light  154 . For example, mirror  134  can be located further away from sample  120  than mirror  132 , which can create a longer path length for light  154  than light  152 . In some examples, the path length of light  154  can change by way of movement of mirror  134  at a constant velocity. The difference in intensity of light  152  and light  154  can be a function of the difference of the path lengths. Light  152  and light  154  can recombine, to form light  156 , and can be incident on sample  120  (step  174  of process  160 ). A portion of light  156  can be absorbed by sample  120 , and a portion of light  156  can reflect off (or transmit) sample  120  (step  176  of process  170 ) as light  158 . Detector  110  can detect light  158  and can generate one or more signals including information about light  158  (step  178  of process  170 ). A processor or controller  140  can receive the one or more signals from detector  110  (step  180  of process  170 ). Controller  140  can capture signals (e.g., output waveforms) at one or more wavelengths to produce an interferogram. Controller  140  can take the Fourier Transform of the interferogram to determine the spectral absorbance (or transmittance) (step  182  of process  170 ). 
       FIG. 1C  illustrates an exemplary Fourier transform output according to examples of the disclosure. In some examples, mirror  132  and mirror  134  can be equidistant from beamsplitter  130 , and light  152  and light  154  can have the same path length. Light  152  and light  154  can have the same phase as each other and can interfere constructively to form light  158 . On the other hand, for example, if mirror  134  is located a quarter-wavelength of light  150  from beamsplitter  130 , light  152  and light  154  can be completely out of phase with each other and can interfere destructively to form light  158 . In some examples, mirror  134  can move back and forth, causing light  158  to include partial constructive interference, partial destructive interference, total constructive interference, and total destructive interference. The resultant output can be a wave with full intensity (e.g., when both mirror  132  and mirror  134  are equidistant) to zero intensity (e.g., when mirror  134  is located a quarter-wavelength of light  150 ). 
       FIG. 2A  illustrates an interface included in a comb spectrometer according to examples of the disclosure. Interface  201  can include opening  212 , opening  213 , opening  215 , opening  217 , opening  219 , opening  220 , and opening  221 . The one or more openings can include one or more apertures, openings, and/or windows configured to allow light to pass through. Each opening can be optically coupled to one or more optical components, such as a light source and/or a detector. 
     One or more openings of interface  201  can be coupled to a light source. For example, the outer openings (e.g., opening  212 , opening  213 , opening  215 , opening  217 , opening  219 , and opening  221 ) can each be coupled to a light source. In some examples, each light source can be coupled to a different opening than another light source. One or more openings, such as opening  220 , can be coupled to a detector. 
       FIG. 2B  illustrates an exemplary comb output according to examples of the disclosure. The comb light emitter (e.g., a light emitter coupled to opening  212 ) can be any type of optical component capable of emitting light in a plurality of wavelength bands, where each wavelength band can be quantized and discrete (i.e., separated by one or more wavelengths). For example, the comb light emitter can include wavelength band  239  and wavelength band  241 , where wavelength band  239  and wavelength band  241  can be separated by one or more wavelengths (included in noise band  237 ). In some examples, the comb light emitter can include a plurality of quantum dots (QDs) that can form the spectral quantized outputs, as illustrated in  FIG. 2B . In some examples, each wavelength band can include one or more wavelengths different from the other wavelength bands. For example, wavelength band  247  can include 610-760 nm, whereas wavelength band  243  can include 500-570 nm. 
     The plurality of tuned QDs, in the aggregate, can be configured to emit light in the plurality of wavelength bands. For example, the plurality of wavelength bands can include wavelength band  239 , wavelength band  241 , wavelength band  243 , wavelength band  245 , wavelength band  247 , and wavelength band  249 , which can formed by six tuned QDs. In some examples, each QD can emit light in a unique wavelength band. A first QD can be tuned to emit light in wavelength band  239  (e.g., 405-445 nm). A second QD can be tuned to emit light in wavelength band  241  (e.g., 455-485 nm). A third QD can be tuned to emit light in wavelength band  243  (e.g., 495-555 nm). A fourth QD can be tuned to emit light in wavelength band  245  (e.g., 565-585 nm). A fifth QD can be tuned to emit wavelength band  247  (e.g., 595-630 nm). A sixth QD can be tuned to emit wavelength band  249  (e.g., 640-695 nm). 
     Each wavelength band can be separated from an adjacent wavelength band by a noise band. For example, noise band  237  can include one or more wavelengths between the range limits of wavelength band  239  and wavelength band  241 . The separation of wavelength bands by a noise band can simplify the implementation and analysis of the spectrometer compared to a broadband source (e.g., white light source or globar). In some examples, given that noise may exist in noise band  237  where actual signal may not exist, noise can be eliminated or reduced from the signal without any use of filters or extra processing. In some examples, one or more wavelength bands, one or more noise bands, or both can have a 10 nm bandpass. In some examples, one or more wavelength bands, one or more noise bands, or both can have a 15 nm bandpass. 
       FIG. 3A  illustrates an exemplary comb spectrometer according to examples of the disclosure. Spectrometer  300  can include interface  301 , light source  304 , detector  310 , and controller  340 . Light source  304  can include light emitter  302 , light emitter  303 , light emitter  305 , light emitter  307 , light emitter  309 , and light emitter  311 . In some examples, the outer openings of interface  301  can be coupled to one or more light emitters. For example, opening  312  can be coupled to light emitter  302 ; opening  313  can be coupled to light emitter  303 ; opening  315  can be coupled to light emitter  305 ; opening  317  can be coupled to light emitter  307 ; opening  319  can be coupled to light emitter  309 ; and opening  321  can be coupled to light emitter  311 . In some examples, the inner opening(s) of interface  301  can be coupled to one or more detectors. For example, opening  320  can be coupled to detector  310 . 
     Interface  301  can be coupled to the optical components by one or more waveguides, such as waveguide  304 . Waveguide  304  can be any type of optical component capable of transmitting light. In some examples, waveguide  304  can include one or more optical fibers. In some examples, waveguide  304  can include one or more silicon photonics chips. 
       FIG. 3B  illustrates an exemplary method for operating a comb spectrometer according to examples of the disclosure. Spectrometer  300  can be configured such that the comb light emitters are sequentially activated. A light emitter (e.g., light emitter  302  illustrated in  FIG. 3A ) included in a light source (e.g., light source  304  illustrated in  FIG. 3A ) can be activated to generate a first light (e.g., light  322  illustrated in  FIG. 3A ) (step  352  of process  350 ). In some examples, the first light can be lock-in modulated to eliminate or reduce the inclusion of noise or stray light in the measurement. In some examples, the first light can be lock-in modulated at 60 Hz. The first light can pass through a waveguide (e.g., waveguide  304 ) to a first opening (e.g., opening  312 ) (step  354  of process  350 ). The first light can exit the first opening (e.g., opening  312 ) (and/or spectrometer  300 ) and can be incident on a sample (e.g., sample  320 ) (step  356  of process  350 ). A portion of light can be absorbed by the sample, and a portion of light (e.g., light  323 ) can reflect back to the spectrometer (e.g., spectrometer  300 ) (step  358  of process  350 ). The reflected light (e.g., light  323 ) can enter the spectrometer through another opening (e.g., opening  320 ) (step  360  of process  350 ). The reflected light can pass through the waveguide to a detector (e.g., detector  310 ) (step  362  of process  350 ). The detector can detect the reflected light and can generate one or more signals including information about the reflected light (step  364  of process  350 ). A processor or controller (e.g., controller  340 ) can receive the one or more signals from the detector (e.g., detector  310 ) (step  366  of process  350 ). The process can be repeated until all or some of the plurality of light emitters has been activated (step  368  of process  350 ). The spectrometer can deactivate a light emitter (e.g., light emitter  302 ) included in the light source (e.g., light source  304 ) and can activate another light emitter (e.g., light emitter  303 ) while detecting the reflected light (step  370  of process  350 ). In some examples, each light emitter included in a light source can be sequentially activated, where the detector can generate signals for each activated light emitter. In some examples, light from the different comb light emitters can be lock-in modulated independently. The controller (e.g., controller  340 ) can determine one or more sample properties (e.g., sample  320 ) based on the one or more signals (step  372  of process  350 ). 
     In some examples, each light emitter can be configured to emit a plurality of wavelengths different from the wavelengths emitted by the other light emitters included in a light source and/or spectrometer.  FIG. 3C  illustrates an exemplary comb light source and spectrometer output according to examples of the disclosure. The spectrometer can include any number of comb light sources including, but not limited to, one comb light source. The light source can be capable of outputting a plurality of wavelengths of light across a spectrum (e.g., visible spectrum) using a plurality of comb light emitters (e.g., light emitter  302 , light emitter  303 , light emitter  305 , light emitter  307 , light emitter  309 , and light emitter  311  illustrated in  FIG. 3A ). Each light emitter can output some of the plurality of wavelengths. For example, light emitter  302  can be configured to output light included in wavelength band  339 , wavelength band  341 , wavelength band  343 , wavelength band  345 , wavelength  347 , and wavelength band  349 . In some examples, a light emitter can output one or more wavelengths of light not included in the wavelength bands of another light emitter. For example, light emitter  303  can be configured to emit light, included in wavelength band  337 , but not included in wavelength band  339 . In some examples, the wavelength bands included in each light emitter can be shifted (in wavelength) relative to the wavelength bands included in the other light emitters. In some examples, at least two wavelength bands can include one or more same wavelengths, but can also include one or more different wavelengths. For example, wavelength band  339  can include 405-445 nm, and wavelength band  337  can include 395-435 nm. Wavelengths  405 - 435  can be the same wavelengths included in both wavelength band  339  and wavelength band  337 ; wavelengths 395-405 nm and 435-445 nm can be the different wavelengths included in one wavelength band, but not in the other wavelength band. In this manner, the spectrometer can be capable of measuring one or more sample properties across a spectrum of wavelengths. In some examples, the same wavelengths included in multiple bands can be utilized for signal measurements. In some examples, the same wavelengths included in multiple bands can be utilized for noise measurements (e.g., noise can be detected when multiple signals including the same wavelength have different signal values). The measurement wavelength can be tuned by activating one or more light emitters and/or light sources with a wavelength band including the measurement wavelengths. In some examples, at least two light emitters and/or light sources can be activated at the same time during the measurements. 
     Although a broadband (e.g., white light) source spectrometer may also be capable of measuring across a spectrum of wavelengths, a broadband source may not be able to discern between signals associated with one or more sample properties and noise. In a comb light source, a light emitter can be activated at times different from other light emitters. Due to the separated (i.e., quantized) wavelength bands for each light emitter, any signal received outside of the wavelength bands (e.g., noise band  237  illustrated in  FIG. 2B ) of a light emitter can originate from noise (e.g., drift, ambient light, and/or electrical noise). In this manner, analysis of the one or more signals from the detector can be simplified and noise rejection and signal-to-noise ratio (SNR) can be improved. 
     Furthermore, broadband source spectrometers may use temporal multiplexing for measurements across the spectrum of wavelengths. Each light source can be activated sequentially across the spectrum. Alternatively, a moving mirror (e.g., mirror  134 ) can be continually enabled as the measurement is being performed across the spectrum. This may lead to long measurement times, moving parts, and/or a large number of light sources. Instead, the comb spectrometer may not require temporal multiplexing to measure multiple wavelengths. Multiple wavelength bands can be measured at a single time. 
     Moreover, broadband source spectrometers may not be capable of resolving specific wavelengths. For example, broadband source spectrometers may only have a resolution of 2 cm −1 , where the resolution can be limited by the traveling distance of the moving mirror (e.g., mirror  134 ). However, in a comb spectrometer, the resolution and the number of spectral lines can be tuned (e.g., increased) by changing the properties (e.g., including more QDs of different sizes) of the QDs and/or the number of comb light emitters and/or light sources. 
     In some examples, the spectrometer can include a plurality of detectors or detector pixels.  FIG. 4A  illustrates an exemplary comb spectrometer including multiple waveguides, and  FIG. 4B  illustrates an exemplary method for operating the comb spectrometer according to examples of the disclosure. Spectrometer  400  can include light source  404 , a plurality of detector pixels (e.g., detector  410 , detector  432 , detector  433 , detector  434 , detector  435 , and detector  436 ), and controller  440 . Light source  404  can include light emitter  402 , light emitter  403 , light emitter  405 , light emitter  407 , light emitter  409 , and light emitter  411 . Each detector or detector pixel can be coupled to one or more different light emitters. In some examples, one or more openings, one or more waveguides, one or more light emitters, and/or one or more detectors (or detector pixels) can be coupled together to form an opening-waveguide-light emitter-detector unit. For example, opening  412  can be optically coupled to waveguide  406 , which can be optically coupled to light emitter  402 . A first light emitter (e.g., light emitter  402 ) can emit a first light (e.g., light  422 ) (step  452  of process  450 ). The first light (e.g., light  422 ) can pass through a first waveguide (e.g., waveguide  406 ) to a first opening (e.g., opening  412 ) (step  454  of process  450 ). The first light can exit the first opening and can be incident on a sample (e.g., sample  420 ) (step  456  of process  450 ). A portion of the first light can be absorbed by the sample, and a portion of the first light (e.g., light  423 ) can reflect back to the spectrometer (e.g., spectrometer  400 ) (step  458  of process  450 ). The reflected light (e.g., light  423 ) can enter the spectrometer through another opening (e.g., opening  420 ) (step  460  of process  450 ). A detector can be optically coupled to the reflected light to form an opening-waveguide-light emitter-detector unit, such as opening  412 -waveguide  406  and waveguide  404 -light emitter  402 -detector  410  unit. The reflected light can pass through the same or another waveguide (e.g., waveguide  404 ) to a first detector (e.g., detector  410 ) (step  462  of process  450 ). The first detector can detect the reflected light and can generate one or more first signals including information about the reflected light (e.g., light  423 ) (step  464  of process  450 ). 
     In some examples, one or more opening-waveguide-light emitter-detector units can be activated at the same time as another opening-waveguide-light emitter-detector unit. For example, opening  417  can be optically coupled to waveguide  408 , which can be optically coupled to light emitter  407 . A second light emitter (e.g., light emitter  407 ) can emit a second light (e.g., light  424 ) (step  466  of process  450 ). The second light (e.g., light  424 ) can pass through a second waveguide (e.g., waveguide  408 ) to a second opening (e.g., opening  417 ) (step  468  of process  450 ). The second light can exit the second opening and can be incident on the sample (e.g., sample  420 ) (step  470  of process  450 ). A portion of the second light can be absorbed by the sample, and a portion of the second light (e.g., light  425 ) can reflect back to the spectrometer (e.g., spectrometer  400 ) (step  472  of process  450 ). The reflected light (e.g., light  425 ) can enter the spectrometer through another opening (e.g., opening  420 ) (step  474  of process  450 ). The same or another (second) detector (e.g., detector  436 ) can be optically coupled to the reflected light (e.g., light  425 ) to form an opening-waveguide-light emitter-detector unit, such as opening  417 -waveguide  408  and waveguide  404 -light emitter  407 -detector  436  unit. The reflected light can pass through the same or another waveguide (e.g., waveguide  404 ) to the second detector (e.g., detector  436 ) (step  476  of process  450 ). The second detector can detect the reflected light and can generate one or more second signals including information about the reflected light (e.g., light  425 ) (step  478  of process  450 ). A processor or controller (e.g., controller  440 ) can receive the one or more first signals from the first detector (e.g., detector  410 ) and one or more second signals from the same or another (second) detector (e.g., detector  436 ) (step  480  of process  450 ). The controller (e.g., controller  440 ) can determine one or more sample properties (e.g., sample  420 ) based at least partially on the one or more first signals and one or more second signals (step  482  of process  450 ). 
     In some examples, the spectrometer can include a plurality of detectors; each detector can be coupled to a comb light source.  FIG. 4C  illustrates an exemplary configuration for a comb spectrometer interface according to examples of the disclosure. Interface  401  can include a plurality of sets of openings, such as set  430 , set  431 , and set  432 . Each set can include a plurality of openings coupled to a comb light source. For example, set  430  can include opening  412 , opening  413 , opening  415 , opening  417 , opening  419 , and opening  421 , where each opening in a set can be coupled to a different comb light emitter. A set can further include an opening coupled to a detector. For example, set  430  can include opening  420 , which can be coupled to a detector. Within a set, the detector can detect reflected light off a sample from light emitted by the comb light emitters. 
     In some examples, an opening can be included in more than one set. For example, opening  417  can be included in both set  430  and set  431 . In some examples, at least two sets can include an opening coupled to the same comb light emitter. For example, opening  413  included in set  430  can be coupled to the same comb light emitter as opening  422  included in set  431 . In some examples, at least two sets can include an opening coupled to different comb light emitters, where the different comb light emitters can have the same optical properties (e.g., wavelength bands). 
     Although  FIG. 4C  illustrates one configuration, examples of the disclosure can include any configuration including a plurality of comb light emitters and at least one detector within a set. In some examples, the configuration can be such that the comb light emitters are intermeshed together to prevent optical interference with each other. For example, relative to opening  421 , opening  413  can be located on the opposite side of opening  420 . Opening  419  can be adjacent to opening  421  and can be located on the same side of set  430  with respect to opening  420  as opening  421 . Relative to opening  413 , opening  415  can be located on the same side of set  430  with respect to opening  420  as opening  415 . In this manner, opening  421  and opening  419  can be located on opposite sides of opening  420  as opening  413  and opening  415 . Opening  412  and opening  417  can be adjacent to opening  420 , but located on opposite sides of opening  420 . In some examples, the configuration can be such that each detector can be surrounded by unique (i.e., different wavelength bands) comb light emitters. As illustrated in  FIG. 4C , opening  420  can be surrounded by opening  412 , opening  413 , opening  415 , opening  417 , opening  419 , and opening  421 , where each opening can be coupled to a unique comb light emitter. Set  431  can be configured such that interference of the same comb light emitter or comb light emitters with the same optical properties (e.g., one or more same wavelength bands) can be prevented. Opening  441  can be coupled to the same comb light emitter (or comb light emitters having the same optical properties) as opening  421 , but can be separated from opening  421  by opening  419 . Opening  439  can be coupled to the same comb light emitter (or comb light emitters having the same optical properties) as opening  419 , but can be separated from opening  419  by opening  417 . Opening  422  can be coupled to the same comb light emitter (or comb light emitters having the same optical properties) as opening  413 , but can be separated from opening  413  by opening  415 . Opening  435  can be coupled to the same comb light emitter (or comb light emitters having the same optical properties) as opening  415 , but can be separated from opening  415  by opening  422 . Opening  432  can be coupled to the same comb light emitter (or comb light emitters having the same optical properties) as opening  421 , but can be located on the outer edge of set  431 , whereas opening  412  can be located on the outer edge of set  430 . In this manner, opening  420 , opening  417 , and opening  440  can be located between and can separate (i.e., prevent or reduce interference) light emitted through opening  432  from light emitted through opening  412 . 
     Unlike a broadband source spectrometer, the comb spectrometer, as disclosed, can be capable of measuring different spatial locations along the sample without the need for mechanical moving parts, a beamsplitter (e.g., beamsplitter  130 ) or prism to measure multiple locations along the sample. Instead, one or more different comb light emitters corresponding to different opening (in the interface) locations can be activated in the comb spectrometer, forming a spectrometer capable of measuring multiple wavelengths without spatial multiplexing. In some examples, the sample may be heterogeneous, so inclusion of the plurality of detectors can reduce measurement uncertainty due to heterogeneity. 
     Spectrometer  400  can include a plurality of detectors, where each detector can be associated with a different wavelength band. Referring back to  FIG. 2B  and  FIG. 4A , for example, detector  410  can be associated with wavelength band  239 . Detector  432  can be associated with wavelength band  241 . Detector  433  can be associated with wavelength band  243 . Detector  434  can be associated with wavelength band  245 . Detector  435  can be associated with wavelength band  247 . Detector  436  can be associated with wavelength band  249 . Each detector can generate a separate signal(s). Controller  440  can receive the plurality of signals and can reject noise based on the association of each detector with wavelength band. For example, controller  440  can receive one or more signals generated by detector  436 . Any signal outside wavelength band  249  can be rejected in the analysis of the sample properties. 
     In some examples, the spectrometer can include comb light sources.  FIGS. 5A-5B  illustrate cross-sectional views of exemplary comb light sources according to examples of the disclosure. In some examples, the comb light source can be a QD comb light source. The QD comb light source can be configured with one or more QDs, where one or more wavelengths of light emitted by the comb light source can be based on the properties of the QDs. Light source  502  can include pump source  504  and tuning layer  506 , as illustrated in  FIG. 5A . Pump source  504  can be any source capable of generating light, including, but not limited to, a lamp, a laser, a light emitting diode (LED), an organic LED (OLED), an electroluminescent (EL) source, a super-luminescent laser diode, any super-continuum source (e.g., a fiber-based source), or a combination of one or more of these sources. Tuning layer  506  can be any optical component capable of filtering or selecting one or more wavelengths of light emitted by pump source  504 . For example, tuning layer  506  can include one or more QDs, such as quantum dot  508 , quantum dot  510 , and quantum dot  512 . The one or more QDs can be small, nanocrystal phosphors with quantized energy levels. Energy from pump source  504  can excite electrons with sufficient energy to jump to the next energy level. The electron may want to return to its lowest energy state or the ground state, and in doing so, can release energy in the form of electromagnetic radiation with a wavelength corresponding to a difference between the lowest energy state and the ground state. The size of the QDs can lead to quantum confinement resulting in energy levels that can be discrete and quantized with finite separation. By changing the size of the QD, the emission wavelength of the QD can be shifted and nearly any frequency of light in the visible spectrum can be achieved. 
     The QDs can be pumped by any pump source having a shorter wavelength (i.e., higher energy) of light. For example, a UV source (&lt;400 nm) can be used to excite a blue (450 nm-500 nm), green (500 nm-570 nm), and/or red (610 nm-760 nm) QDs. Larger QDs can emit longer wavelengths of light. For example, 6 nm diameter QDs can be fabricated for red light; 4 nm diameter QDs can be fabricated for green light; and 2 nm QDs can be fabricated for blue light. In some examples, tuning layer  506  can include a plurality of QDs with different sizes. For example, quantum dot  510  (e.g., emitting blue light) can have a smaller diameter and shorter wavelength emission than quantum dot  508  (e.g., emitting red light). Quantum dot  508  can have a smaller diameter and shorter wavelength emission than quantum dot  512  (e.g., emitting green light). In this manner, a single tuning layer can be used for emitting a plurality (e.g., three) of wavelength bands (e.g., wavelength band  341 , wavelength band  343 , and wavelength band  347  illustrated in  FIG. 3C ) 
     In some examples, the light source can comprise a plurality of tuning layers, as illustrated in  FIG. 5B . Light source  522  can include pump source  524 , tuning layer  526 , tuning layer  528 , and tuning layer  530 . Pump source  524  can be any source capable of generating light, including, but not limited to, a lamp, a laser, a LED, an OLED, an EL source, a super-luminescent laser diode, any super-continuum source, or a combination of one or more of these sources. Tuning layer  526 , tuning layer  528 , and/or tuning layer  530  can be any optical component capable of filtering or selecting one or more wavelengths of light emitted by pump source  524 . For example, one or more of the tuning layers can be configured to receive light emitted by pump source  524  and can allow one or more wavelengths of light to pass through. Tuning layer  526  can include quantum dots  538 ; tuning layer  528  can include quantum dots  540 ; and tuning layer  530  can include quantum dots  542 . In some examples, at least one tuning layer can have QDs with a different size than the QDs in another tuning layer. For example, quantum dots  538  can have a larger diameter (and longer wavelength emission) than quantum dots  540 . In some examples, quantum dots  540  can have a larger diameter (and longer wavelength emission) than quantum dots  542 . In some examples, light source  522  can have a non-gradient variation in QD size. For example, quantum dots  542  can have a larger diameter (and longer wavelength emission such as red light) than quantum dots  540 , which can have a smaller diameter than quantum dots  538 . 
     The QDs included in the comb light source can have one or more properties based on the performance output of the light source. In some examples, the density of the QDs can be tuned based on the intensity of light emitted by the light source. For example, a greater density of QDs can increase the amount of energy absorbed by the QDs, which can in turn increase the total amount of energy (i.e., intensity) emitted. In some examples, the density of the QDs can be based on the relative location of the tuning layer within the light source stackup. For example, tuning layer  526  can have a lower density of quantum dots  538  (than the density of quantum dots  540  included in tuning layer  528 ) to prevent quantum dots  538  from absorbing all the incoming energy from pump source  524 . The density of quantum dots  538  can be configured such that at least some energy from pump source  524  “leaks” out to tuning layer  528 . In some examples, tuning layer  528  can have a lower density of quantum dots  540  (than the density of quantum dots  542  included in tuning layer  528 ) to prevent quantum dots  540  from absorbing all remaining (e.g., energy not absorbed by tuning layer  526 ) energy from pump source  524 . In this manner, at least some of the energy from pump source  524  can reach all the tuning layers (e.g., tuning layer  526 , tuning layer  528 , and tuning layer  530 ). 
     In some examples, the thickness of a tuning layer can be based on the output wavelength. For example, a tuning layer can be configured with a greater thickness for longer wavelengths, or a tuning layer can be configured with a lower thickness for shorter wavelengths. In some examples, the thicknesses of the tuning layers can be different. In some examples, tuning layer  526  can be thicker than tuning layer  528 , which can be thicker than tuning layer  530 . In some examples, with the comb light sources, one or more filters can be excluded from the spectrometer. 
     Although  FIG. 5B  illustrates three tuning layers, examples of the disclosure can include any number of tuning layers. Furthermore, although  FIG. 5B  illustrates a gradient change in QD densities in the light source stackup, examples of the disclosure can include any configuration of QD densities (e.g., tuning layer  528  has the highest density of QDs relative to the density of QDs in tuning layer  530  and tuning layer  526 ). 
     In some examples, the light source can include a plurality of tuning layers, where at least one tuning layer can have at least two QDs with different sizes, as illustrated in  FIG. 5C . Light source  542  can include pump source  524 , tuning layer  532 , tuning layer  534 , and tuning layer  536 . Tuning layer  532  can include quantum dots  560 , quantum dots  561 , and quantum dots  562 , where each can have different sizes. In some examples, the number of differently sized QDs can be different relative to other tuning layers. For example, tuning layer  532  can include three differently sized QDs (e.g., quantum  560 , quantum dot  561 , and quantum dot  562 ), whereas tuning layer  534  can include two differently sized QDs (e.g., quantum dot  563  and quantum dot  564 ). In some examples, at least one tuning layer can include QDs with one size (e.g., quantum dot  565  included in tuning layer  536 ). 
     In some examples, the spectrometer can include one or more filters, such as QD filters. The one or more filters can be located between the light source and the detector. For example, a filter can be disposed on or located in close proximity to the light emitter and/or light source. In some examples, a filter can be disposed on or located in close proximity to the detector. Utilization of the one or more filters can allow the spectrometer capability of direct separation (i.e., separation of light without further processing by the controller) of wavelength bands. Moreover, the spectrometer can be configured to allow reflected light originating from multiple light emitters to be incident on the detector without affecting the direct separation capability. As a result, the number of waveguides can be reduced to one waveguide, for example, configured to allow the reflected light including multiple wavelength bands to pass through. The one or more filters can separate the reflected light based on its wavelength band. 
       FIGS. 6A-6B  illustrate top and cross-sectional views of a QD filter according to examples of the disclosure. Filter layer  605  can include a plurality of filters, such as filter  626 , filter  628 , filter  630 , filter  632 , filter  634 , and filter  636 . Each filter can include a plurality of QDs. Filter  626  can include a plurality of quantum dots  640 ; filter  628  can include a plurality of quantum dots  641 ; and filter  630  can include a plurality of quantum dots  642 . Each filter can be configured for selectively allowing light having one or more wavelengths included in a wavelength band to pass through and configured for rejecting light with all other wavelengths. In some examples, at least two of the filters included in the filter layer can selectively allow different wavelength bands. For example, filter  626  can be configured for selectively allowing light included in one wavelength band (e.g., wavelength band  247  illustrated in  FIG. 2B ), and filter  628  can be configured for selectively allowing light included in another wavelength band (e.g., wavelength band  241  illustrated in  FIG. 2B ). 
       FIG. 6C  illustrates exemplary spectral absorbance for QD step filters and the calculated transmittance according to examples of the disclosure. Filter  626  can be configured to absorb light having a wavelength between wavelength  625  and wavelength  627 . Light with wavelengths longer (i.e., smaller energy) than the output wavelength of quantum dots  640  can pass through filter  626 . Light with wavelengths shorter (i.e., greater energy) than the output wavelength of quantum dots  640  can be absorbed by filter  626 . Filter  626  can be optically coupled to one or more light emitters (e.g., light emitter  402  illustrated in  FIG. 4A ), one or more detectors (e.g., detector  410  illustrated in  FIG. 4A ), one or more openings (e.g., opening  412  illustrated in  FIG. 4A ) included in the interface, or any combination thereof. The detector optically coupled to filter  626  can generate one or more first signals. Filter  628  can be configured to absorb light having a wavelength between wavelength  625  and wavelength  629 . Light with wavelengths longer (i.e., smaller energy) than the output wavelength of quantum dots  641  can pass through filter  628 . Light with wavelengths shorter (i.e., greater energy) than the output wavelength of quantum dots  641  can be absorbed by filter  628 . Filter  628  can be optically coupled to one or more light emitters (e.g., light emitter  403  illustrated in  FIG. 4A ), one or more detectors (e.g., detector  432  illustrated in  FIG. 4A ), one or more openings included in the interface, or any combination thereof. The detector optically coupled to filter  628  can generate one or more second signals. A controller can subtract the one or more first signals (associated with filter  626 ) from the one or more second signals (associated with filter  628 ) to create a passband (illustrated in the calculated transmittance plot on the bottom of  FIG. 6C ) allowing light with a wavelength between wavelength  627  and wavelength  629  to pass through. Although  FIG. 6C  illustrates a bandpass filter formed from subtracting the signals from two step filters, examples of the disclosure can include any number of step filters to create the bandpass filter. In some examples, one or more filters can include QDs with different properties to allow multiple wavelength bands to pass through the filter. In some examples, the spectrometer can be configured with six wavelength bands, formed with three filters and two different QDs per filter. 
       FIG. 7A  illustrates a cross-sectional view of an exemplary QD filter according to examples of the disclosure. Filter  705  can include a plurality of QDs having different properties. Filter  705  can include quantum dots  708 , quantum dots  710 , and quantum dots  712 . Quantum dots  708 , quantum dots  710 , and quantum dots  712  can be configured with different sizes, which can lead to different wavelengths of absorbance and transmittance. Quantum dots  708 , quantum dots  710 , and quantum dots  712  can be further configured with different densities, which can tune the intensity of absorbance and transmittance, as illustrated in the filter spectral output illustrated in  FIG. 7B . In some examples, the distribution of the QDs included in the filter can be tailored based on a targeted passband output. 
     In some examples, a filter can be optically coupled to multiple light emitters and/or light sources, thereby reducing the number of filters, number of light emitters, and/or number of light sources included in the spectrometer. For example, a broadband source spectrometer configured to measure 30 different wavelength bands may require 30 different detectors (or detector pixels) and 30 different filters. On the other hand, a comb spectrometer can be configured to measure the 30 different wavelength bands with six different light sources, five detector pixels, and five filters. 
     In some examples, a filter can be configured to allow light included in different wavelength bands to pass through. In some examples, one or more filters can be configured to allow a wide range (e.g., one or more wavelength bands) of wavelengths to pass through, and a narrow band (e.g., a subset of wavelengths included in a wavelength band) can be selected by illuminating a specific comb light emitter. For example, a filter can be configured to allow light included in wavelength band  337  and wavelength band  339  (illustrated in  FIG. 3C ) to pass through, and either light emitter  302  (for wavelength band  339 ) or light emitter  303  (for wavelength band  337 ) can be activated to select the narrower band including the targeted measurement wavelength(s). 
       FIGS. 8A-8B  illustrate exemplary waveguide configurations according to examples of the disclosure. In some examples, multiple light sources can be coupled to a single waveguide. For example, as illustrated in  FIG. 8A , light source  802 , light source  803 , and light source  805  can be coupled to interface  801  using a single waveguide  804 . By using multiple light sources to generate light including multiple wavelength bands, one or more light sources can be turned off to conserve power. In some examples, a light source can be coupled to multiple waveguides. For example, as illustrated in  FIG. 8B , light source  802  can be coupled to different openings included in interface  801  using at least waveguide  804  and waveguide  806 . In some examples, each waveguide can be coupled to a different wavelength band and/or detector. 
     In some examples, the properties of one or more waveguides (e.g., optical fibers or silicon photonics waveguides) can configured to allow sufficient light mixing. For example, an optical fiber can be configured with a length (e.g., greater than or equal to 1 mm) equal to a multiple of the emission wavelength of the light emitter and/or light source to which the optical fiber is coupled to. In some examples, the multiple can be large, such as a multiple greater than three. In some examples, the diameter of the optical fiber can large compared to the emission wavelength of the light emitter and/or light source to which the optical fiber is coupled to. 
       FIG. 9  illustrates a top view of an exemplary configuration for a comb spectrometer interface according to examples of the disclosure. Interface  901  can include a plurality of openings, such as opening  912 , coupled to one or more light sources. Each opening can include a plurality of sub-openings, such as sub-opening  942  and sub-opening  943 . Each sub-opening can be coupled to a light emitter and can be associated with a wavelength band. In some examples, each sub-opening can be associated with a different wavelength band by, e.g., being associated to a different filter. For example, sub-opening  942  can be associated with wavelength band  339  (illustrated in  FIG. 3C ), and sub-opening  943  can be associated with wavelength band  341  (illustrated in  FIG. 3C ). In some examples, each sub-opening can be optically coupled to a different detector. In some examples, each opening (e.g., opening  912 ) coupled to one or more light sources located within close proximity (e.g., less than 1 mm away) to one or more openings (e.g., opening  920 ) coupled to one or more detectors. 
     Although interface  901  can be configured to allow wavelength bands to be spatially separated and can simplify the implementation and analysis, one or more path lengths within an opening may differ. For example, reflected light entering sub-opening  942  can have a longer path length than reflected light entering sub-opening  943 , merely due to the center of sub-opening  942  being located further away from opening  920  than the center of sub-opening  943 .  FIG. 10  illustrates a top view of an exemplary configuration for a comb spectrometer interface according to examples of the disclosure. Interface  1001  can include a plurality of openings, such as opening  1012 , coupled to one or more light sources (referred to as light source openings). Interface  1002  can further include one or more openings, such as opening  1040  and opening  1041 , coupled to one or more detectors (referred to as detector openings). Each light source opening (e.g., opening  1012 ) can be located a distance away from an opening (e.g., opening  1040  or opening  1041 ) coupled to one or more detectors. In some examples, the distance can be greater than 1 mm. In some examples, the distance can be greater than 2 mm. In some examples, the distance can be such that the reflected light has a long path length. In some examples, due to the greater distance between the one or more detector openings and the one or more light source openings, any path length difference between sub-openings (e.g., opening  1042  and opening  1043 ) may have a negligible effect on the measurement accuracy. In some examples, due to the longer path length(s), the measured sample (e.g., sample  420  illustrated in  FIG. 4A ) can be used for light mixing, in addition to or instead of, using one or more waveguides to light mixing. In some examples, one or more openings can be coupled to a light emitter, and interface  1001  can exclude one or more sub-openings. 
     In some examples, interface  1001  can include multiple openings, such as opening  1040  and opening  1041 , and each opening can be coupled to one or more detectors. In some examples, the multiple openings can be located in the center of interface  1001 . The location of the multiple openings can be such that the separation distances between an opening coupled to a light source and an opening coupled to a detector are the same. For example, the separation distance between opening  1012  (coupled to a light source) and opening  1040  (coupled to a detector) can be the same as the separation distance between opening  1017  (coupled to a light source) and opening  1041 . In some examples, each opening coupled to one or more detectors can include one or more different wavelength bands. 
     In some examples, the interface can include a ring of openings coupled to one or more light sources.  FIG. 11A  illustrates a top view of an exemplary ring configuration for a comb spectrometer interface according to examples of the disclosure. Interface  1101  can include a plurality of openings, such as opening  1117 , opening  1118 , opening  1119 , opening  1120 , and opening  1121 , coupled to one or more light sources (referred to as light source openings). In some examples, each opening can include a plurality of sub-openings (e.g., sub-opening  942  and sub-opening  943  illustrated in  FIG. 9 ). The plurality of light source openings can form a ring (or another closed shape) or a partial ring (e.g., one or more arcs or non-circular sections) (or another partial shape). In some examples, interface  1101  can include at least one set of openings, such as set  1130  and set  1131 . A set of openings can include neighboring openings that can be coupled to different comb light sources (and/or comb light emitters). For example, opening  1117 , opening  1118 , opening  1119 , opening  1120 , and opening  1121  can be coupled to different light sources. In some examples, the different light sources can include wavelength bands that are shifted relative to the other light sources coupled to the openings in the same set. In some examples, the different lights sources coupled to the openings in the same set taken together can form a continuous spectrum. In some examples, light source openings within a set can be optically coupled to the same detector opening. For example, opening  1117 , opening  1118 , opening  1119 , opening  1120 , and opening  1121  can be optically coupled to opening  1141 . 
     In some examples, at least one light source opening in one set can be optically coupled to the same light source as another light source opening in another set. For example, opening  1121  included in set  1130  can be optically coupled to the same light source (or different light sources having the same optical properties) as opening  1112  included in set  1131 . In some examples, for openings optically coupled to the same light source (or to different light sources having the same optical properties), the separation distance between the light source opening and detector opening can be the same. For example, the separation distance between opening  1121  and opening  1141  can be the same as the separation distance between opening  1112  and opening  1142 . Some openings (e.g., opening  1141  and opening  1142 ) can be located in the center, and other openings can be located in the periphery (e.g., opening  1121  and opening  1112 ). The separation distances between the openings located in the center and the openings located in the periphery can be the same, which can lead to the same path lengths through the sample. Heterogeneity in the sample (at locations measured between the center openings and peripheral openings) can be addressed by having multiple peripheral openings associated with the combs having the same optical properties (e.g., wavelength). In some examples, the interface can include different ring patterns and/or different opening locations to address heterogeneity in the same at locations in close proximity to the center openings. 
     In some examples, each set of openings (coupled to one or more light sources) included in interface  1101  can have the same configuration. For example, opening  1121  (included in set  1130 ) and opening  1112  (included in set  1131 ) can be optically coupled to the same light source (or to different light sources having the same optical properties). Similarly, opening  1120  (included in set  1130 ) and opening  1113  (included in set  1131 ) can be optically coupled to the same light source (or to different light sources having the same optical properties). Opening  1119  (included in light set  1130 ) and opening  1114  (included in set  1131 ) can be optically coupled to the same light source (or to different light sources having the same optical properties). Opening  1118  (included in light set  1130 ) and opening  1115  (included in light set  1131 ) can be optically coupled to the same light source (or to different light sources having the same optical properties). Opening  1117  (included in light set  1130 ) and opening  1116  (included in light set  1131 ) can be optically coupled to the same light source (or to different light sources having the same optical properties). The spectrometer operation can include activating light comb sources have the same optical properties (e.g., one or more wavelength bands) at the same time to take a measurement, and sequentially activating other light comb sources having the same optical properties to take other measurements until the wavelength bands are measured. 
       FIG. 11B  illustrates an exemplary method for operating a ring comb spectrometer interface according to examples of the disclosure. Light sources having the same optical properties can be referred to as units. The light source coupled to opening  1121  and the light source coupled to opening  1112  (referred to as “first units” in  FIG. 11B ) can have the same optical properties, and one or more sample properties can be measured using these light sources (step  1152  of process  1150 ). The light source coupled to opening  1120  and the light source coupled to opening  1113  (referred to as “second units” in  FIG. 11B ) can have the same optical properties, and one or more sample properties can be measured using these light sources (step  1154  of process  1150 ). The light source coupled to opening  1119  and the light source coupled to opening  1114  (referred to as “third units” in  FIG. 11B ) can have the same optical properties, and one or more sample properties can be measured using these light sources (step  1156  of process  1150 ). The light source coupled to opening  1118  and the light source coupled to opening  1115  (referred to as “fourth units” in  FIG. 11B ) can have the same optical properties, and one or more sample properties can be measured using these light sources (step  1158  of process  1150 ). The light source coupled to opening  1117  and the light source coupled to opening  1116  (referred to as “fifth units” in  FIG. 11B ) can have the same optical properties, and one or more sample properties can be measured using these light sources (step  1160  of process  1150 ). The process can be repeated. Although  FIG. 11B  refers to two light sources and two openings included in a unit, the units can include any number of light sources and any number of openings coupled to the light sources. 
       FIGS. 12A-12B  illustrate top and cross-sectional views of an exemplary interleaved comb spectrometer according to examples of the disclosure. Interface  1201  can include a plurality of light source openings, such as openings  1212  and openings  1213 , coupled to one or more light sources (e.g., light source  1202  and light source  1203 ). Interface  1201  can further include a plurality of detector openings, such as openings  1220  coupled to one or more detectors (e.g., detector  1210 ). In some examples, light source openings can be interleaved with detector openings. For example, interface  1201  can be arranged as rows of openings, as illustrated in  FIG. 12A . A row can alternate between a light source opening and detector opening. In some examples, opening  1212  can be coupled to a different light source (e.g., light source  1202 ) (or a light source having different optical properties) than opening  1213 . In some examples, light source  1202  and light source  1203  can have the same optical properties, but can be coupled to filters having different optical properties. For example, light source  1202  can be coupled to filter  1205 , and light source  1203  can be coupled to filter  1207 . Filter  1205  can allow one or more different wavelength bands (e.g., wavelength band  339  illustrated in  FIG. 3C ) to pass through than filter  1207  can allow (e.g., filter  1207  can allow wavelength band  337  illustrated in  FIG. 3C  to pass through). In some examples, at least two rows can have the same pattern of openings. In some examples, at least two rows can have different patterns of openings (e.g., a first row can have a pattern including opening  1212 , opening  1220 , opening  1213 , opening  1220 , opening  1212 , opening  1220 , and opening  1213 ; and a second row can have a pattern including opening  1212 , opening  1220 , opening  1213 , opening  1220 , opening  1213 , opening  1220 , and opening  1220 ). 
     A spectrometer is disclosed. In some examples, the spectrometer comprises: a plurality of light emitters configured to emit a plurality of wavelengths of light across a spectrum, each light emitter configured to emit light in one or more wavelength bands included in the plurality of wavelengths, each of the one or more wavelength bands being separated from another wavelength band by one or more wavelengths, wherein at least two of the one or more wavelength bands of at least two of the plurality of light emitters include different wavelengths; and one or more detectors configured to detect a reflection of light emitted by the plurality of light emitters and configured to generate one or more signals indicative of the reflection of light. Additionally or alternatively, in some examples, the spectrometer further comprises: a plurality of sets of first openings, each set coupled to one of the plurality of light emitters, wherein each set comprises light emitters having different optical properties. Additionally or alternatively, in some examples, the spectrometer further comprises: one or more second openings coupled to the one or more detectors, wherein the plurality of sets of first openings forms a ring and the one or more second openings are located in a center of the ring. Additionally or alternatively, in some examples, the spectrometer further comprises: one or more first openings, each first opening coupled to one of the plurality of light emitters, one or more second openings, each second opening coupled to the one or more detectors, wherein the one or more first openings and the one or more second openings are interleaved. Additionally or alternatively, in some examples, the one or more first openings and the one or more second openings alternate. Additionally or alternatively, in some examples, the one or more wavelength bands of adjacent light emitters include a same wavelength. Additionally or alternatively, in some examples, the spectrometer further comprises: a plurality of openings configured to allow light to pass through; and a waveguide configured to optically couple at least one of the plurality of light emitters to at least one of the plurality of openings. Additionally or alternatively, in some examples, the waveguide is an optical fiber. Additionally or alternatively, in some examples, the waveguide is a silicon photonics chip. Additionally or alternatively, in some examples, the waveguide is coupled to at least two of the plurality of light emitters. Additionally or alternatively, in some examples, the spectrometer further comprises: a plurality of waveguides including the waveguide, wherein the waveguide coupled to one of the plurality of light emitters. Additionally or alternatively, in some examples, the spectrometer is capable of measuring multiple wavelengths at a same time. Additionally or alternatively, in some examples, the spectrometer is capable of measuring multiple wavelengths without spatial movement. Additionally or alternatively, in some examples, the spectrometer excludes a filter. Additionally or alternatively, in some examples, a number of the one or more wavelength bands is equal to a number of the plurality of light emitters multiplied by a number of the one or more detectors, the spectrometer further comprising: one or more filters optically coupled to the one or more detectors, wherein a number of the one or more filters is equal to the number of the one or more detectors. Additionally or alternatively, in some examples, at least one of the one or more detectors is configured to detect a reflection of at least two of the plurality of light emitters. Additionally or alternatively, in some examples, a separation distance between each light emitter and an optically coupled detector is the same. Additionally or alternatively, in some examples, the spectrometer further comprises: a processor capable of: receiving the one or more signals from the one or more detectors, determining one or more properties of a sample using a portion of the one or more signals included in the one or more wavelength bands. 
     A light source is disclosed. In some examples, the light source comprises: a plurality of light emitters configured to emit a plurality of wavelengths of light across a spectrum, each light emitter configured to emit light in one or more wavelength bands included in the plurality of wavelengths, each of the one or more wavelength bands being separated from another wavelength band by one or more wavelengths, wherein at least two of the one or more wavelength bands of at least two of the plurality of light emitters include different wavelengths. Additionally or alternatively, in some examples, the plurality of light emitters includes a first light emitter and a second light emitter, the first light emitter including at least one wavelength band shifted relative to at least one wavelength band of the second light emitter. Additionally or alternatively, in some examples, each of the plurality of light emitters includes a plurality of quantum dots, each quantum dot configured to emit light included in one wavelength band, separate and distinct from the wavelength bands of the other of the plurality of quantum dots. Additionally or alternatively, in some examples, each of the plurality of quantum dots has a size different from the other of the plurality of quantum dots, the size associated with the one wavelength band. Additionally or alternatively, in some examples, each of the plurality of light emitters includes a plurality of layers, each of the plurality of layers including one or more of the plurality of quantum dots having a same size. Additionally or alternatively, in some examples, the plurality of quantum dots is located in a single layer. Additionally or alternatively, in some examples, each of the plurality of light emitters includes a plurality of layers, at least one of the plurality of layers including at least two of the plurality of quantum dots having different sizes. Additionally or alternatively, in some examples, the one or more wavelength bands have bandpass less than or equal to 10 nm. Additionally or alternatively, in some examples, the one or more wavelength bands are separated by at least 15 nm. 
     A method for emitting light across a spectrum is disclosed. In some examples, the method comprises: activating one or more first light emitters, wherein each of the first light emitters emits light included in one or more first wavelength bands, each of the one or more first wavelength bands separated from another first wavelength band by one or more wavelengths; and activating one or more second light emitters, wherein each of the second light emitters emits light included in one or more second wavelength bands, each of the one or more second wavelength bands separated from another second wavelength band by one or more wavelengths, wherein the one or more second wavelength bands are shifted relative to the one or more first wavelength bands, and further wherein the one or more first light emitters and the one or more second light emitters are activated at different times. 
     A method for determining one or more properties of a sample is disclosed. In some examples, the method comprises: activating a plurality of first light emitters, wherein each of the first light emitters emits light included in one or more first wavelength bands, each of the one or more first wavelength bands separated from another first wavelength band by one or more wavelengths; and activating a plurality of second light emitters, wherein each of the second light emitters emits light included in one or more second wavelength bands, each of the one or more second wavelength bands separated from another second wavelength band by one or more wavelengths, wherein the one or more second wavelength bands are shifted relative to the one or more first wavelength bands, and further wherein the plurality of first light emitters and the plurality of second light emitters are activated at different times; the method further comprises detecting a reflection of first light emitted by the plurality of first light emitters; generating a first signal indicative of the detected reflection of the first light; detecting a reflection of second light emitted by the plurality of second light emitters; generating a second signal indicative of the detected reflection of the second light; and determining the one or more sample properties based on at least the first and second signals. Additionally or alternatively, in some examples, the method further comprises: excluding portions of the first signal not associated with the one or more first wavelength bands; and excluding portions of the second signal not associated with the one or more second wavelength bands. Additionally or alternatively, in some examples, each of the plurality of first light emitters are spatially separated and activated at a same time, and each of the plurality of second light emitters are spatially separated and activated at a same time. Additionally or alternatively, in some examples, the method further comprises: mixing one or more of the reflection of the first light and the reflection of the second light using a waveguide. Additionally or alternatively, in some examples, the method further comprises: mixing one or more of the reflection of the first light and the reflection of the second light using the sample. Additionally or alternatively, in some examples, the method further comprises: determining a difference in signal values between at least one of the plurality of first light emitters and at least one of the second light emitters, wherein the signal values are associated with a same wavelength included in both the one or more first wavelength bands and the one or more second wavelength bands. Additionally or alternatively, in some examples, the method further comprises: filtering one or more of the emitted first light to the one or more first wavelength bands by activating the plurality of first light emitters; and filtering the detected reflection of the first light to one or more third wavelength bands using one or more filters, wherein the one or more first wavelength bands are included in the one or more third wavelength bands. 
     A filter is disclosed. In some examples, the filter comprises: a plurality of sets of quantum dots, each set of quantum dots configured to emit light included in one wavelength band, separate and distinct from the wavelength bands of the other sets of quantum dots, wherein the plurality of sets of quantum dots can be located on the same layer and each set of quantum dots can be located in separate sections of the layer. Additionally or alternatively, in some examples, at least two sets of quantum dots are configured to form a step filter, a wavelength of a step for one step filter located at a different wavelength than the wavelength of a step for the other step filter. 
     Although the disclosed examples have been fully described with reference to the accompanying drawings, it is to be noted that various changes and modifications will become apparent to those skilled in the art. Such changes and modifications are to be understood as being included within the scope of the disclosed examples as defined by the appended claims.

Metadata:
Filing Date: 20170829
Publication Date: 20200630
Grant Date: 20200630
Priority Date: 20160831
Inventors: KANGAS, Miikka M.
KOLLER, JEFFREY G.
ATHAS, WILLIAM C.
Assignee: APPLE INC
CPC Classifications: [{"code": "G01J2003/102", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J3/453", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J3/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01J3/0218", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J3/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J3/0218", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J2003/102", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J3/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01J3/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J3/51", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J3/0218", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J3/10", "inventive": true, "first": true, "tree": "[]"}, {"code": "G01J3/42", "inventive": true, "first": false, "tree": "[]"}, {"code": "G01J2003/102", "inventive": false, "first": false, "tree": "[]"}, {"code": "G01J3/51", "inventive": true, "first": false, "tree": "[]"}]
Family ID: 71125179