Spectrometer apparatus

A spectrometer includes a substrate; a plurality of light detectors in the substrate; and a plurality of light filters over the plurality of light detectors, each of the plurality of light filters transmitting a different wavelength or reflecting a different wavelength, each of the light filters aligned with a corresponding one of the plurality of light detectors.

TECHNICAL FIELD

The present disclosure relates generally to spectrometers, and, in particular embodiments, to miniaturized spectrometers suitable for, e.g., integration with semiconductor devices.

BACKGROUND

An optical spectrometer (also referred to as a spectrometer) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum. The variable measured is the light's intensity for each light frequency. Spectrometers were developed in early studies of physics, astronomy, and chemistry. The capability of spectroscopy to determine chemical composition drove its advancement and continues to be one of its primary uses. Spectrometers are used in astronomy to analyze the chemical composition of stars and planets.

A spectrometer often comprises an optical system and optical detectors. The optical system causes optical dispersion of the light by, e.g., refraction using a prism, or by diffraction using a diffraction grating. The optical detectors detect different components of the dispersed light with different frequencies. For example, in a spectrometer using prism, a slit selects a thin strip of light which passes through the collimator and gets parallelized. The parallelized light then passes through the prism, in which it is refracted twice (once when entering and once when leaving). Due to the nature of the dispersive element, the angle with which light is refracted depends on its wavelength. This leads to a spectrum of thin lines of light, which may be detected by the optical detectors. Replacing the prism with a diffraction grating result in a grating spectrometer.

Recently, there has been a growing interest in developing miniaturized spectrometers that may be integrated into or with semiconductor devices for use in digital mobile devices, such as smart phones, tablets, or the like. New applications enabled by the miniaturized spectrometers integrated in digital mobile devices may encompass many aspects of everyday life, such as assessing the quality of food, material analysis for detecting counterfeit products, fitness and health detection, or telemedicine.

SUMMARY

In some embodiments, a spectrometer includes a substrate, a plurality of light detectors in the substrate, and a plurality of light filters over the plurality of light detectors, each of the plurality of light filters transmitting a different wavelength or reflecting a different wavelength, each of the light filters aligned with a corresponding one of the plurality of light detectors.

In some embodiments, a spectrometer includes a substrate, a plurality of light detectors in the substrate, a first layer over the substrate, and a prism at least partially in the first layer, the prism comprising an electro-optic material.

In some embodiments, a method includes filtering an optical signal using an array of light filters, the array of light filters comprising a first light filter and a second light filter, the first light filter letting through a first transmitted optical signal having a first wavelength, the second light filter letting through a second transmitted optical signal having a second wavelength different from the first wavelength, and detecting the first transmitted optical signal and the second transmitted optical signal. The light filters may be for example polarizing filters, useful to perform a separate spectral analysis for each light polarization component.

DETAILED DESCRIPTION

Embodiments of the present disclosure are discussed in the context of miniaturized spectrometers, and in particular, spectrometers suitable for integration in optoelectronics devices. In some embodiments, a spectrometer includes one or more light filters, and each of the light filters reflects a different wavelength or transmits a different wavelength. The reflected light or the transmitted light from each of the light filters is detected by a corresponding light detector. The light filter may be an interferential filter, a plasmonic filter, a filter based on quantum structures (e.g. quantum dots, quantum wires), or a filter based on subwavelength structures designed to filter selected wavelength(s). The light filters may each comprise an electro-optic material, such that the optical characteristics (e.g., the wavelength of the transmitted and/or the reflected light, or the polarization) can be adjusted electrically. In some embodiments, the optical characteristics of each light filter is adjusted over time, such that a same light filter is used to transmit (or reflect) light having a first wavelength at a first time instant, and the same light filter is subsequently used to transmit (or reflect) light having a second wavelength at a second time instant, where the second wavelength is different from the first wavelength. In some embodiments, a spectrometer includes a prism integrated in a semiconductor device. The prism may comprise an electro-optic material such that the optical characteristics of the prism may be adjusted electrically. In some embodiments, the spectrometer additionally includes movable microelectromechanical systems (MEMS) arms, and the movable MEMS arms mechanically adjust a position of the prism.

FIGS. 1A-1Cillustrate various views (e.g., top view, cross-sectional view) of a spectrometer100.FIG. 1Aillustrate a top view of the spectrometer100. The spectrometer100comprises a plurality of light filters101, which are configured in a matrix form. As illustrated inFIG. 1A, the light filters101form a matrix with multiple rows and multiple columns. In an exemplary embodiment, the number of light filters101in the matrix of light filters101is equal to the number of different wavelengths the spectrometer100detects. The number of rows and the number of columns illustrated inFIG. 1Aserve merely as an example, other numbers of rows and other number of columns are also possible and are fully intended to be included within the scope of the present disclosure.

FIG. 1Billustrates the cross-sectional view of the spectrometer100along cross-section A-A inFIG. 1A. Note that for clarity, not all elements of the spectrometer100are illustrated. As illustrated inFIG. 1B, a plurality of light detectors103, such as photo diodes or other suitable light detectors, are disposed under (e.g., directly under) the light filters101. Each of the light detectors103is optically aligned with a respective light filter101, such that light passing through a light filter101(also referred to as the transmitted light of a light filter, or as a transmitted optical signal of a light filter) is detected by a corresponding light detector103. Therefore, in the example ofFIGS. 1A and 1B, the light detectors103are also configured in a matrix having a same size (e.g., number of rows and number of columns) as the matrix of the light filters101.

FIG. 1Billustrates the filtering of incident light110by the light filters101. The light110(may also be referred to as an optical signal) may be a broad spectrum light that comprises light components having a plurality of wavelengths (e.g., λ1, λ2, λn). For example, the light110may include light components in a portion of the visible light spectrum, such as lights having wavelengths between about 400 nm to about 700 nm. The light110may include invisible lights, such as infrared light, ultraviolet light, or the like, as examples. In some embodiments, each of the light filter101transmits (e.g., passes, or lets through) a light component of the light110, which light component has a wavelength different from wavelengths of other light components transmitted by other light filters101. For example, a light filter101A lets through light component120A having a wavelength λ1, a light filter101B lets through light component120B having a wavelength λ2, and a light filter101C lets through light component120C having a wavelength λ3, where λ1, λ2, and λ3are different. Therefore, although light110impinges on all of the light filters101, the transmitted light components (e.g.,120A,120B, and120C) of the light filters101each has a different wavelength. The transmitted light of each of the light filters101is detected by a respective light detector103. The output of light detectors103indicates the intensity of each transmitted light, which output may be recorded and used to reconstruct the spectrum of the light110, in some embodiments. In some embodiments, a pitch (e.g., distance between centers of adjacent light filters101) of the light filters101is a multiple (e.g., one time (1×), twice (2×), or more) of a pitch (e.g., distance between centers of adjacent light detectors103) of the light detectors103.

In the discussion hereinafter, the phrase “a light filter transmits a wavelength” may be used to describe that the light filter transmits a light component having the wavelength. Similarly, the phrase “a light filter reflects a wavelength” may be used to describe that the light filter reflects a light component having the wavelength.

FIG. 1Cillustrates the cross-sectional view of a single light filter101ofFIGS. 1A and 1B. In the example ofFIG. 1C, the light filter101comprises a plurality of layers, such as layers131,133, and135. Each of the layers131,133, and135may comprises a suitable material such as an oxide (e.g., silicon oxide), a semiconductor material (e.g., silicon, germanium, or the like), a polymer, a metamaterial, a metal (e.g., a thin metal film), a gas, or a fluid. Each of the layers131,133, and135may be formed to be substantially uniform (e.g., having a substantially uniform thickness), patterned (e.g., having openings with designed patterns and formed of selected materials such as gold), or nanostructured (e.g., having material structure like rough surface, quantum dots, nano-wires, nano-tubes, or similar structures having sizes up to, e.g., in the order of 100 nm to enhance the quantum confinement effects). The patterned structures may be, e.g., plasmonic structures or subwavelength structures. It is possible, for example, to modulate the filtered wavelength by adjusting the size of the nanostructure, thereby causing a change in the energy bandgap of the material (e.g. ZnSe, InP), or to modulate the refractive index by adjusting the size of the subwavelength structure. An embodiment method for forming light filters having subwavelength structures is discussed hereinafter with reference toFIGS. 17A-17E.

In some embodiments, each of the layers131,133, and135has a refractive index that is different from a refractive index of an adjacent layer, and there is a step or gradual change in the refractive indexes of adjacent layers at the interface between the adjacent layers (e.g., an interface between131and133, or an interface between133and135). For example, the layer131may have a first refractive index at the interface131L between the layer131and the layer135, the layer135may have a second refractive index at the interface131L, and there is a change between the first refractive index and the second refractive index. In some embodiments, the layers131,133, and135are formed of a same material, but with each layer comprising a different pattern(s), a different nanostructure(s), or a different subwavelength structure(s).

In some embodiments, the refractive indexes of the layers131,133, and135and the thicknesses of the layers131,133, and135may be determined by, e.g., calculation or simulation using commercial software based on the physics of light interference of multiple beams in multiple layers. For example, the layers131and135may be formed of a material (e.g., SiO2) having a thickness in the order of 100 nm, and the layers133may be formed of a material (e.g., Al) having a thickness in the order of 10 nm.

In an embodiment, one of the layers (e.g.,133) of the light filter101may be formed using a sacrificial material (e.g., silicon oxide), which sacrificial material is removed later using, e.g., an etching process. The etching process may use an etchant having a high etching selectivity (e.g., higher etching rate) for the sacrificial material, such that the sacrificial material is removed without substantially attacking other layers of the light filter101. Once the sacrificial material is removed, the space previously occupied by the sacrificial material may be filled by a gas (e.g., ambient air, a single gas, or a mixture of gases) or a fluid with a target refractive index. Therefore, in some embodiments, the light filter101may have layers (e.g.,131,135) comprising solid materials, and may have at least one layer (e.g.,133) comprising a gas or a fluid.

In some embodiments, the refractive index and/or the thickness of each layer131,133, and135are adjusted, e.g., by calculations or simulations, to determine the optical characteristics of the light filter101, such that the light filter101transmits a wavelength λ1and reflects other wavelengths λ2, λ3, . . . , λn, where λ1, λ2, λ3, . . . , λnare wavelengths of the light components of the incident light110. In other embodiments, the light filter101is designed to reflect a wavelength λ1and transmits other wavelengths λ2, λ3, . . . , λn, in which case (not shown inFIG. 1B) the light detectors103are placed on a same side of the light filters101with the incident light110, with the light detectors103having appropriate angular position with respect to the light filters101such that the reflected light impinges on the light detectors103. The light filter101inFIG. 1Cmay also be referred to as an interferential filter, since the design of the light filter101is based on the physics of light interference. As discussed above, each light filter101has a different design (e.g., different material(s), different thickness of each layer, combinations thereof, or the like) such that each light filter101transmits a different wavelength.

FIG. 1Cshows three layers131,133, and135in the light filer101as a non-limiting example. Other numbers of layers, e.g., two, fourth, or more than four, are also possible and are fully intended to be included within the scope of the present disclosure. In addition, one skilled in the art will appreciate that in the discussion herein, when a light filter (e.g.,101) is said to transmit (or reflect) a wavelength k, the light filter transmits (or reflects) a narrow band of wavelengths around k. In other words, instead of passing a light component with a single wavelength k, the light filter (e.g.,101) passes a narrow band of light components having wavelengths between, e.g., λ−Δ1and λ+Δ2, where Δ1and Δ2are values such as about 50 nm or other suitable values, depending on, e.g., the application of the spectrometer and/or the targeted spectral resolution of the spectrometer.

By forming a matrix of light filters101, where each light filler101passes a different wavelength, the spectrometer100shown inFIGS. 1A-1Callows for a compact, small format factor design for efficient spatial wavelength dispersion and analysis of the incident light110. The spectrometer100is therefore well suited for integration into semiconductor devices to form miniaturized spectrometers.

Referring now temporarily toFIGS. 17A-17E,FIGS. 17A-17Eillustrate a light filter201D having subwavelength structures at various stages of fabrication. InFIG. 17A, a semiconductor substrate1701(e.g., silicon) is provided. Next, inFIG. 17B, a plurality of openings1702are formed at the upper surface of the substrate1701. The openings1702may be formed using, e.g., photolithography and etching techniques. The openings1702may have a width in the order of 1 μm, and a depth in the order of 10 μm, as examples, although other dimensions are also possible, depending on the wavelength of the light. The number of openings1702and the distance between adjacent ones of the openings1702may comprise any suitable number and are determined by the design of the light filter201D.

Next, inFIG. 17C, an epitaxial layer1703(e.g., mono-crystalline silicon) is formed over the substrate1701. The epitaxial layer1703(e.g., a semiconductor layer) seals the openings1702, in some embodiments. A gas may be sealed in the sealed openings1702. The gas sealed in the openings1702may be a process gas in the deposition chamber for forming the epitaxial layer1703. In some embodiments, the gas sealed in the openings1702comprises a gas injected into the openings1702, which injected gas has a target physical (e.g., optical) characteristics for forming the light filter201D. In some embodiments, there is substantially no gas in the sealed openings1702, and the sealed openings1702may be at low pressure that can be obtained through a getter material. In yet other embodiments, the openings1702are not sealed.

Next, inFIG. 17D, openings1704are formed in the epitaxial layer1703, and an epitaxial layer1705(e.g. a semiconductor layer) is formed over the epitaxial layer1703. The epitaxial layer1705may be formed of a same material as the epitaxial layer1703, although a different material may also be used, depending on, e.g., the design of the light filter201D. The number and the dimension of the openings1704are determined by the design of the light filter201D, and therefore, may be different from (or the same as) the number and the dimension of the openings1702. Methods for forming the openings1704may be the same as or similar to those for forming the openings1702, thus are not repeated. The epitaxial layer1705may seal the openings1704, and a gas may be sealed inside the sealed openings1704. In some embodiments, the sealed openings1704comprise a vacuum. In some embodiments, the openings1704are not sealed.

Next, inFIG. 17E, openings1706are formed in the epitaxial layer1705, and an epitaxial layer1707is formed over the epitaxial layer1705. The epitaxial layer1707may be formed of a same material as the epitaxial layer1703or1705, although a different material may also be used, depending on, e.g., the design of the light filter201D. The number and the dimension of the openings1706are determined by the design of the light filter201D, and therefore, may be different from (or the same as) the number and the dimension of the openings1702and/or1704. Methods for forming the openings1706may be the same as or similar to those for forming the openings1702, thus are not repeated. The epitaxial semiconductor layer1707may seal the openings1706, and a gas may be sealed inside the sealed openings1706. In some embodiments, the sealed openings1706comprise a vacuum. In some embodiments, the openings1706are not sealed. The number of layers of the light filter201D illustrated inFIGS. 17A-17Eis for illustration purpose and not limiting, other numbers are also possible and are fully intended to be included within the scope of the present disclosure.

Referring now toFIGS. 2A-2D,FIGS. 2A-2Dillustrate various views (e.g., top view, cross-sectional view) of a spectrometer200(e.g.,200A or200B). The spectrometer200A inFIG. 2A, shown in a top view, comprises a plurality of light filters201arranged in a matrix form (e.g., having multiple columns and multiple rows).FIG. 2Billustrates the top view of the spectrometer200B having an array (e.g., having one row or one column) of light filters201. In some embodiments, the number of light filters201in the spectrometer200A/200B, denoted by N1, is smaller than the number of different wavelengths N2the spectrometer200A/200B detects. In an embodiment, the spectrometer200B has only one light filter201and one corresponding light detector203.

In the illustrated embodiments, each of the light filters201comprises at least one electro-optic material, such that the optical characteristics (e.g., transmitted wavelength or polarization) of the light filter201can be changed by, e.g., adjusting electrical voltage applied to the material. Therefore, the spectrometer200A or200B achieves detection of N2different wavelengths using N1(N1<N2) light filters201by changing the optical characteristics of each light filter201over time, such that the wavelength of the transmitted optical signal of each light filter201is changed over time, thereby allowing each light filter201to pass different wavelengths over time. Details of the light filters201and method for changing the optical characteristics of the light filters201are discussed in details hereinafter.

Referring toFIG. 2C, which illustrates the cross-sectional view of the spectrometer200A along cross-section B-B ofFIG. 2A, or a cross-section view of the spectrometer200B along cross-section C-C ofFIG. 2B. As illustrated inFIG. 2C, the light110, which may be a broad spectrum light having light components with wavelengths λ1, λ2, λ3, . . . , λn, impinges on the light filters201. Each light filter201transmits a wavelength λt, which λtis different from the wavelength transmitted by another light filter201of the spectrometer200A/200B. A plurality of light detectors203are disposed under the light filters201, with each light detector203optically aligned with a respective light filter201to detect the transmitted light from the respective light filter201. Therefore, in a first round of processing, N1different wavelengths pass through the light filters201and are detected by the light detectors203.

Next, the optical characteristics of each light filters201are changed to allow a different wavelength to pass through. Since each light filter201comprises at least one electro-optic material, the optical characteristics of each of the light filters201can be changed, e.g., by changing a voltage applied to the light filter201, or by changing a temperature of the light filter201.FIG. 2Cillustrates a voltage Vtbeing applied to one of the light filters201for illustration purpose only. It is understood that each of the light filters201may have an individual control parameter (e.g., a voltage, or a temperature) applied and modified to change its optical characteristics (e.g., transmitted wavelength or polarization). In some embodiments, N1individual control parameters are modified independently of each other to change the optical characteristics of each of the light filters201. Therefore, in a second round of processing, the light filters201allows another N1different wavelengths to pass through the light filters201and to be detected by the light detectors203. This process can be repeated for M times, until the number of wavelengths detected, denoted as M×N1, is equal to or larger than N2(e.g., M×N1≥N2).

Various methods to change the voltage, or the temperature of each of the light filters201are possible and are fully intended to be included within the scope of the present disclosure. As an example, each light filter201may have a resistive element (e.g., resistor) attached. By changing the voltage applied to the resistive element, the heat generated by an electrical current flowing through the resistive element may be adjusted to modify the temperature of each of the light filters201.

FIG. 2Dillustrates the cross-sectional view of the light filter201inFIGS. 2A-2C. The light filter201include a plurality of layers, e.g.,231,233and235. At least one of the layers231,233and235comprises an electro-optic material, which may have linear or non-linear electro-optic characteristics. The layers231,233and235may comprise any suitable material such as hydrogenated amorphous silicon, liquid crystal, or polymer (e.g., polyimide). The optical characteristics of the electro-optic material may be modified by a control parameter such as voltage, or temperature. By changing the optical characteristics of the electro-optic material (e.g., refractive index or propagation properties for different polarization components), the light propagation in the material (e.g., amplitude, transmission, reflection, polarization) may be modified. This, coupled with the light interference in the different layers of the light filter201, may change the wavelength of the light transmitted (or reflected) by the light filter201and may select different polarization components. Therefore, the light filter201may be referred to as an active light filter or an active interferential filter. In contrast, the optical characteristics of the light filter101inFIG. 1Cis not configured to be adjustable, and therefore, the light filter101may also be referred as a passive filter or a passive interferential filter.

In some embodiments, the material of each layer (e.g.,231,233, or235), the thickness of the each layer, and/or the control parameter (e.g., voltage, or temperature) of the electro-optic material are designed to achieve certain target optical characteristics (e.g., transmitted wavelength, or reflected wavelength) for the light filter201. In some embodiments, one or more layers of the light filter201may be formed by a sacrificial material, which sacrificial material is later removed and replaced by a gas or a fluid, similar to the discussion above with reference toFIG. 1C, thus details are not repeated.

FIG. 2Dillustrates three layers231,233, and235as a non-limiting example. Other number of layers are also possible and are fully intended to be included within the scope of the present disclosure. AlthoughFIG. 2Dillustrates one wavelength λtpassing through the light filter201at a time, the light filter201may be designed to pass through more than one wavelengths at a same time, depending on, e.g., the application and requirements of the spectrometer.

By modifying the optical characteristics of each of the light filters201, each of the light filters201may be used to filter (e.g., pass through or reflect) different wavelengths at different time. This allows for temporal wavelength dispersion in addition to spatial wavelength dispersion, which means the number of light filters (e.g., N1) in the spectrometer200A/200B may be smaller than the number of wavelengths (e.g., N2) to be analyzed by the spectrometer. In other words, a trade-off between speed and size can be made for the spectrometer200A/200B. For example, a smaller number of light filters201may be used to form a very compact spectrometer, but the total time used for analyzing the spectrum of the light may be increased, due to the sequential processing (due to temporal wavelength dispersion) performed to cover all the wavelengths.

In some embodiment, the electro-optic material may be used to control in real time the polarization, in order to perform a separate spectral analysis for each polarization components. This analysis can be performed in separate regions of the passive filter matrix100inFIG. 1Aor in different temporal sequences.

FIG. 2Eillustrates a top view of a spectrometer200C with light filters201A,201B, or201C.FIGS. 2F-2Hillustrate cross-sectional views of various embodiments of the spectrometer200C ofFIG. 2Ealong cross-section D-D.

InFIG. 2E, the spectrometer200C has a plurality of light filters (e.g.,201A,201B, or201C) formed in or on a substrate245. The substrate245may be any suitable substrate, such as a semiconductor substrate (e.g., silicon substrate). The light filters201A/201B/201C are arranged in a matrix form inFIG. 2Eas an example. In other embodiments, the light filters201A/201B/201C may be arranged in an array format, or may include a single light filter.

FIG. 2Fillustrates an embodiment cross-section view of the spectrometer200C ofFIG. 2Ehaving light filters201A. As illustrated inFIG. 2F, each of the light filter201A has a plurality of layers, such as layers237,238, and239. The layer239is formed on an underlying layer247, which underlying layer247may comprise any suitable material, such as a semiconductor material or a dielectric material. The layer237is formed over the layer239, and is attached to the substrate245by springs241(e.g., mechanical springs241attached to sidewalls of the layer237). The layers237and239may be the same as or similar to the layers231,233, or235of the light filter201ofFIG. 2Dor may be the same as or similar to the layers131,133, or135of the light filter101ofFIG. 1C, thus details are not repeated. The layer238of the light filter201A is formed by a gas or a fluid, which gas or fluid is contained in a space240enclosed by the layers237/239, the substrate245, and MEMS arms243. The MEMS arms243may be, e.g., piezoelectric (PZT) beams, or bi-metallic beams. The MEMS arms243may be actuated by, e.g., an electrical voltage applied to the MEMS arms243to move the layer237in various directions, such as up-and-down along the direction indicated by the arrow253, or tilted to the left or right along the direction indicated by arrows251. By adjusting the thickness of the layer238and the relative position of the layers237and239, the optical characteristics of the light filter201A is adjusted. In some embodiments, the optical characteristics of the light filter201A are adjusted in real-time, e.g., by adjusting the position of the layer237in response to a control voltage applied to MEMS arms243. In some embodiments, each of the light filter201A is adjusted individually, e.g., by applying an individual control voltage to the MEMS arms243of each light filter201A. The adjustment of each light filter201A may be asynchronous (e.g., adjusted at different, independent time instants). In other embodiments, two or more filters201A are adjusted by, e.g., a same control voltage applied to respective MEMS arms243.

The design of light filters201A inFIG. 2Fillustrates an additional method (e.g., mechanical movement) to adjust the optical characteristics of the light filters, in additional to changing the properties of the electro-optic material(s) of the light filters as discussed with reference toFIG. 2D.

FIG. 2Gillustrates another embodiment cross-section view of the spectrometer200C ofFIG. 2Ehaving light filters201B. The light filter201B is similar to the light filter201A ofFIG. 2F, but with the shape of the space240(thus the shape of the layer238) of the light filter201B being different from that of the light filter201A. In addition, the springs241may be replaced by another elastic structure, such as a membrane (e.g., a silicon membrane), that may seal the space240. The layer237may be comprised in the membrane or may be formed over the membrane. Like reference numerals inFIGS. 2F and 2Grefer to the same or similar components, thus details are not repeated.

FIG. 2Hillustrates yet another embodiment cross-section view of the spectrometer200C ofFIG. 2Ehaving light filters201C. The light filter201C includes a plurality of layers, such as layers271,273and275. The layers271,273and275may be the same as or similar to the layers131,133, or135of the light filter101ofFIG. 1Cor the same as or similar to the layers231,233, or235of the light filter201ofFIG. 2D, thus details are not repeated. As illustrated inFIG. 2H, the light filter201C is supported by a movable beam245C underneath, which movable beam245C may be or include a MEMS arm such as a PZT beam, a bi-metallic beam, a capacitive actuation element, or a magnetic actuation element. The movable beam245may be controlled, e.g., by a control voltage, to tilt the light filter201C to the left or to the right as indicated by the arrows265. The angle between an upper surface271U of each light filter201C and the incident light (not shown) may be adjusted in real-time by, e.g., adjusting the movable beam245C. An advantage of adjusting in real time the angle of incidence is, e.g., in case the incident light is polarized, the light intensity ratio between different polarization components is modulated, which gives additional information for spectral analysis. The number of light filters in the spectrometer200C and the number of layers in the light filters201A/201B/201C illustrated are for illustration purpose and not limiting. Other numbers of light filters and other numbers of layers in each of the light filters are also possible and are fully intended to be included within the scope of the present disclosure.

FIG. 3illustrates the cross-sectional view of a spectrometer300. The spectrometer300includes a substrate311, a plurality of light detectors303and a circuit313(e.g., an integrated circuit) formed in or on the substrate311. The substrate311may include a semiconductor substrate, such as silicon, doped or undoped, or an active layer of a semiconductor-on-insulator (SOI) substrate. The semiconductor substrate311may include other semiconductor materials (e.g. germanium), a compound semiconductor (e.g. silicon carbide), an alloy semiconductor (e.g. SiGe), or a III-V semiconductor (e.g. gallium arsenide), or combinations thereof. Other substrates, such as multi-layered or gradient substrates, may also be used. Devices, such as transistors, diodes, capacitors, resistors, etc., may be formed in and/or on the semiconductor substrate311and may be interconnected by interconnect structures (not shown) formed by, for example, metallization patterns in one or more dielectric layers over the semiconductor substrate311to form the circuit313.

The spectrometer300further includes a layer315over the substrate311, which layer315comprises a suitable dielectric material such as silicon oxide, or the like. The layer315(or portions of the layer315between light detectors303and light filters301) is transparent to the wavelengths of the light to be detected by the light detectors303of the spectrometer300. A plurality of light filters301are formed in a plurality of layers317over (e.g., directly over) the light detectors303. Each of the plurality of layers317may comprise silicon, a dielectric material, a polymer, or other suitable material. In some embodiments, the materials of the layers317are non-transparent (e.g., blocking) to at least the wavelengths of the light to be analyzed by the spectrometer300, such that the wavelengths of the light to be analyzed only reach the light detectors303through the light filters301. A layer319, which may comprise a same material as the layer315, is formed over the light filters301and the layers317. The layer319is transparent to the wavelengths of the light to be analyzed by the spectrometer300, at least in the portion where the light passes through.

InFIG. 3, each light filter301has a corresponding light detector303, such that the light transmitted through each light filter301is detected by a respective underlying light detector303. The light filter301may be the same or similar to the light filter101inFIG. 1C, or the light filter201inFIG. 2D. For example, each of the light filters301may comprise an electro-optic material that is adjustable by a control parameter (e.g., voltage, or temperature), similar to the light filter201. The light detector303may be, e.g., a photo diode, or other suitable detector for detecting light.

In some embodiments, the circuit313manages the light detectors303and adjusts the optical characteristics (e.g., transmitted wavelength, or reflected wavelengths) of each of the light filter301. For example, electrical conductive paths (e.g., conductive lines and vias, not shown inFIG. 3) are formed in the substrate311and in the layers (e.g.,315,317,319) over the substrate311to electrically connect the circuit313with each of the light filter301and each of the light detectors303. In some embodiments, the circuit313adjusts, e.g., the voltage, or the temperature of each of the light filters301, such that the transmitted wavelength of each light filter301changes over time to achieve temporal wavelength dispersion. In some embodiments, the circuit313receives the output of the light detectors303, and performs certain processing, such as data formatting and/or pre-processing of the output of the light detector303. Data formatting may include changing the format of the light detector output from a first format (e.g., a raw data format) to a second format (e.g., two's complementary format) suitable for subsequent processing. Pre-processing may include pre-filtering, such as low-pass filtering or band-pass filtering the output of the light detectors303to remove out-of-band noises and to improve signal quality, as examples. In addition, the circuit313may perform any other suitable functions.

The number of light filters301, the number of light detectors303, as well as the number of layers (e.g.,315,317,319) illustrated inFIG. 3are for illustrated purpose only and not limiting. Other numbers are also possible and are fully intended to be included within the scope of the present disclosure.

FIG. 4illustrates the cross-sectional view of a spectrometer400. Unlike the spectrometer300inFIG. 3, which detects lights passing through the light filters301, the detector403detects light reflected by the light filters401. While the light filter101inFIG. 1Cand the light filter201inFIG. 2Dare discussed in the context of detecting the transmitted light through the light filter, one skilled in the art would readily appreciate that it is possible to apply the same principle discussed above to design the light filter101or201, such that the wavelengths of interest are reflected by the light filter101or201for detection by the light detectors. In other words, instead of detecting the transmitted light (where the light filter is optimized for transmission operation) from each of the light filters (e.g.,101,201), the spectrometer may detect the reflected light (may also be referred to as a reflected optical signal) from each of the light filters (where the light filter is optimized for reflection operation). Each of the light filters401inFIG. 4, therefore, may have a same or similar structure as the light filters101inFIG. 1C or 201inFIG. 2D, and are designed to reflect a light component with a wavelength different from the wavelength of the reflected light of other light filters401.

As illustrated inFIG. 4, a plurality of light detectors403and a circuit413are formed in/on a substrate411. The substrate411, the light detectors403, and the circuit413may be the same or similar to the substrate311, the light detectors303, and the circuit313ofFIG. 3, respectively, thus details may not be repeated. The light detectors403may be, e.g., a photo diode, or any suitable detector for detecting light. For example, the light detector403may use the optoelectronic device with a V-shaped recess for detecting electromagnetic radiation disclosed in U. S. Patent Publication No. 2014/0001521 A1, which patent publication is incorporated herein by reference. Note that for simplicity, the electrical connections (e.g., conductive lines such as copper lines) between the circuit413and the light filters401, and between the circuit413and the light detectors403, are not shown.

Still referring toFIG. 4, a layer415, which may be a dielectric layer, is formed over the substrate411, the light detectors403and the circuit413. The layer415is formed of a material that is non-transparent to (e.g., blocking) the light (e.g., incident light110and the reflected light) to be analyzed and may thus be referred as a non-transparent layer. In addition, a plurality of light filters401are formed over the layer415in one or more layer417. The one or more layers417may comprise any suitable material, e.g., dielectric material such as silicon oxide, silicon nitride, or polymer. Each of the light filters401may include at least one electro-optic material such that the optical characteristics (e.g., the wavelength(s) of the reflected light) of the light filter401are adjustable through at least one control parameter (e.g., voltage, or temperature).

FIG. 4further illustrates transparent regions421which extend through the substrate411, through the layer415, and to the light filters401. The transparent regions421are transparent to (e.g., pass through) the incident light110.FIG. 4also illustrates transparent regions423extending through the layer415and disposed between the light filters401and the light detectors403. Each of the transparent regions421is disposed close to a respective transparent region423, and both the transparent regions421and the respective transparent region423are adjacent to (e.g., in physical contact with) a respective light filters401, as illustrated inFIG. 4. In some embodiments, the incident light110passes through the transparent regions421to reach the light filters401, and the reflected lights (not shown) from the light filters401travel through the transparent regions423to reach the light detectors403.

In some embodiments, the transparent regions421and the transparent regions423are formed of a same material. In some embodiments, the transparent regions421and the transparent regions423are formed of different materials. In particular, the transparent regions421may comprise a material(s) that passes through all light components (e.g., all wavelengths) of the incident light110, while each of the transparent regions423may comprise a material(s) that only passes through the reflected light (e.g., reflected wavelength(s)) from a corresponding light filter401. In other words, each of the transparent regions423may pass through a wavelength (or a plurality of wavelengths) different from the wavelength(s) of other transparent regions423. The wavelength to be transmitted in regions423may be controlled by using an electro-optic material for the transparent regions423, and by applying different control parameters (e.g., voltage, or temperature) to different transparent regions423.

In some embodiments, the transparent regions421comprise an electro-optic material. By adjusting the optical characteristics (e.g., refractive index) of the electro-optic material of the transparent regions421, the angle of incidence of the light110on the light filters401are adjusted. Similarly, the angle of incidence of the reflected light on the light detectors403may be adjusted by adjusting the optical characteristics (e.g., refractive index) of the electro-optic material of the transparent regions423. For example, the voltage, or the temperature of the electro-optic material of the transparent regions421(or423) may be adjusted to achieve the target refractive index. An advantage of adjusting in real time the angle of incidence is, e.g., in case the incident light is polarized, the light intensity ratio between different polarization components is modulated, which gives additional information for spectral analysis.

FIG. 5Aillustrates the cross-sectional view of a spectrometer500. The spectrometer500is similar to the spectrometer400ofFIG. 4, but with different light filters501. As illustrated inFIG. 5A, the spectrometer500has a substrate511, light detectors503, circuit513, transparent regions521, transparent regions523, and non-transparent layers515, which are the same as or similar to the substrate411, light detectors403, circuit413, transparent regions421, transparent regions423, and non-transparent layers415ofFIG. 4, respectively, thus details are not repeated. Note that for simplicity, the electrical connections (e.g., conductive material) between the circuit513and the light filters501, and between the circuit513and the light detectors503, are not shown.

FIG. 5Afurther illustrates a transparent layer517on the non-transparent layer515. The light filters501are formed in one or more layer519, which may be the same or similar to the layer417ofFIG. 4, or may be the same or similar to the layer511. The light filters501may extend partially into the transparent layer517. As illustrated inFIG. 5A, the incident light110travels through the transparent regions521to reach light filters501(seeFIG. 5Bfor more details), and the light reflected by the light filters501travels through the transparent regions523to reach the light detectors503.

FIG. 5Billustrates a cross-sectional view showing details of the light filter501ofFIG. 5A. Unlike the light filters (e.g.,301,401) discussed above, the light filter501comprises V-shaped layers (e.g.,541,543). Although not shown, other suitable shapes, e.g., U-shape, or semispherical shape, may also be used for the layers (e.g.,541,543). The layers541and543of the light filter501may comprise the same or similar materials as the layers of the light filter101inFIG. 1Cor the layers of the light filter201inFIG. 2D. In some embodiments, at least one of the layers541and543comprises an electro-optic material, such that the optical characteristics (e.g., reflected wavelength(s)) of the light filter501is adjustable through a control parameter (e.g., voltage, or temperature). The number of layers of the light filter501illustrated inFIG. 5Bis merely an example, other numbers of layers are also possible and are fully intended to be included within the scope of the present disclosure.

FIG. 5Bfurther shows a transparent region545of the light filter501, which transparent region545fills a V-shaped (or other suitable shape such as U-shaped, or semispherical shaped) recess between the intersecting segments of the layers541/543. The transparent region545is formed of a material that is transparent to the incident light110. In some embodiments, the light filter501comprises an electro-optic material. By adjusting the optical characteristics of the electro-optic material (e.g., by changing the voltage, or the temperature of the electro-optic material), the filtered wavelength can be adjusted. In other embodiments, the transparent region545is an electro-optical material, and the angle of incidence of the incident light110on the light filter501is adjusted to a target value by controlling, e.g., the voltage or the temperature of the electro-optical material. The light filter501with the V-shaped recess may advantageously increase the detection efficiency, and may also achieve better wavelength selection. Another advantage of adjusting in real time the angle of incidence is, e.g., in case the incident light is polarized, the light intensity ratio between different polarization components is modulated, which gives additional information for spectral analysis.

FIG. 6illustrates the cross-sectional view of a spectrometer600. Note that for clarity, not all elements of the spectrometer600are illustrated. The spectrometer600improves the detection efficiencies by detecting both the transmitted light and the reflected light. The spectrometer600includes light filters601and light detectors603A and603B. As illustrated inFIG. 6, the light110, which includes light components having a plurality of wavelengths, impinges on the light filters601. In the illustrated example, each of the light filters601transmits (e.g., passes, or lets through) a different wavelength(s), and reflects another different wavelength(s). The transmitted light120is detected by a respective light detector603A, and the reflected light130is detected by a respective light detector603B.

One skilled in the art will readily appreciate that the principles discussed above regarding light filters, e.g.,101,201, and401, may be used to form the light filter601. Therefore, the spectrometer600is a combination of the transmission type spectrometer (e.g.,100,200, and300) and the reflection type spectrometers (e.g.,400and500), and may be referred to as a transmission-and-reflection type spectrometer. The various structures and combinations of materials for the various light filters (e.g.,101,201,401) discussed above can be readily used to form the light filters601. For example, the light filters601may be formed in a matrix form (see, e.g.,FIG. 1A) to achieve spatial wavelength dispersion. As another example, each of the light filters601may comprise an electro-optic material such that the optical characteristics (e.g., reflected wavelength(s) and transmitted wavelength(s)) of the light filter601can be adjusted by a control parameter (e.g., the voltage, or the temperature of the electro-optic material) to achieve temporal wavelength dispersion. In embodiments where temporal wavelength dispersion is used, trade-off between speed and size can be made, and therefore, the spectrometer600may comprise light filters601formed in an array (see, e.g.,FIG. 2B) to achieve small form factor. In an embodiment, the spectrometer600comprises a single light filter601to achieve even smaller form factor.

FIG. 7illustrates a transmission-and-reflection type spectrometer700. The substrate711, light detectors703, circuit713, light filters701, transparent regions721/723, non-transparent layer715(e.g., non-transparent to the incident light110), and layer717form a reflection-type spectrometer similar to the spectrometer400inFIG. 4. Like reference numerals inFIG. 7refer to like elements inFIG. 4, thus details are not repeated here. For example, substrate711inFIG. 7is formed of a same or similar material as the substrate411inFIG. 4.

FIG. 7further illustrates non-transparent layer715B, light detectors703B, transparent regions723B, substrate711B, and circuit713B. The non-transparent layer715B, the light detectors703B, the substrate711B, and the circuit713B may be the same or similar to the non-transparent layer715, the light detectors703, the substrate711, and the circuit713, thus details are not repeated. In some embodiments, the transparent regions721,723and723B are formed of a same material, e.g., a material transparent to (passing through all wavelengths of) the incident light110. In some embodiments, the transparent regions721is formed of a material transparent to the incident light110, while each of the transparent regions723is formed of a material transparent to the reflected light of a respective light filter701, and each of the transparent regions723B is formed of a material transparent to the transmitted light of a respective light filter701.

FIG. 8Aillustrates a cross-sectional view of a device800having an integrated spectrometer803. The device800may be a digital mobile device, such as a smart phone, a tablet, a hand-held medical device, or the like.FIG. 8Afurther illustrates the analysis of a sample811using the device800with the integrated spectrometer803. As illustrated inFIG. 8A, the device800has a housing805and a screen801, which screen801may comprise screen portions801A,801B, and801C. The screen801may be, e.g., a liquid crystal screen. The integrated spectrometer803may be any suitable spectrometer, such as the spectrometer300,400,500,700disclosed above, or the spectrometer900,1000,1100,1200, or1200A disclosed hereinafter.

To analyze the sample811using the spectrometer803, the device800transmits (e.g., sends out) light813A and light813B through the screen portion801A and screen portion801B, respectively, toward the sample811. The lights813A/813B may be generated by sources823of the device800. The lights813A/813B may be monochromatic, or may be non-monochromatic (e.g., comprising light components with a plurality of wavelengths). In some embodiments, the lights813A and813B are the same (e.g., having the same wavelength(s)). In some embodiments, the light813A is different (e.g., having different wavelengths) from the light813B. The reflected light815travels through the screen portion801C to arrive at the spectrometer803. The spectrometer803analyzes the sample811by analyzing the reflected light815.

FIG. 8Billustrates the calibration process for the spectrometer803of the device800. To calibrate the spectrometer803, a calibration source821of the device800transmits (e.g., sends out) a light814with a known spectrum (e.g., a plurality of known wavelengths). The light814impinges on a diffusing surface825and the reflected light816travels through the screen portion801C to reach the spectrometer803. The diffusing surface825may be, e.g., a white surface that reflects light814without changing its spectrum contents (e.g., wavelengths). The diffusing surface825diffuses the light814in different direction (e.g., isotropically), in some embodiments. The output of the spectrometer803is then compared with the known spectrum of the light814for the calibration process.

FIGS. 9-11illustrates cross-sectional views of various embodiments of spectrometers using a prism.FIG. 9illustrates a spectrometer900having a substrate911, light detectors903, a circuit913, and a non-transparent layer915. The substrate911, the light detectors903, the circuit913, and the non-transparent layer915are the same or similar to the substrate411, light detectors403, circuit413, and the non-transparent layer415ofFIG. 4, respectively, thus details are not repeated.

FIG. 9further illustrates a transparent region923extending from an upper side of the non-transparent layer915to a lower side of the non-transparent layer915. The transparent region923is formed of a material that is transparent to the incident light110, in the illustrated embodiment. Layers917and919, each of which may comprise a suitable material such as silicon, ceramic, or plastic, are over the non-transparent layer915and may each be referred to as a substrate. In some embodiments, the layers917and919are the same substrate wafer (e.g., formed of a same material). A prism901is embedded in the substrate917and919. A transparent region921, formed of a material that is transparent to the incident light110, extends from an upper side of the substrate919to a lower side of the substrate919, in the illustrated embodiment. A top portion of the prism901is in the transparent region921. A bottom surface901B of the prism901at least partially overlaps with the transparent region923. A transparent layer918, transparent to the incident light110, is formed over the substrate919. The layer918may be formed in such a way that portions of the layer918outside the light path are formed of a material that is not transparent to the incident light110.

In some embodiments, the substrate917and919are non-transparent to the light110. Therefore, the light110enters the prism901from top portions of the prism901disposed in the transparent region921. As illustrated inFIG. 9, the light110travels through the transparent layer918and the transparent region921, enters the prism901through top portions of a surface901A of the prism901in the transparent region921, gets refracted by the prism901, exits the prism901at the bottom surface901B of the prism901, and travels through the transparent region923to reach the light detectors903. Due to the prism901, the light110is refracted and forms a spectrum of light with different wavelengths after exiting the prism901. The light detectors903may therefore each detect a different wavelength of the spectrum.

In another embodiment, portions of the light110may also enter the prism901through top portions of a surface901C of the prism901in the transparent region921. These portions of the light110, after being refracted by the prism901, exit the prism901and passes through the transparent region923to be detected by the detector903. In this case, the lateral size and the location of the transparent region923, and the location of the detectors903, may be adjusted to be in the path of the refracted light (not shown inFIG. 9).

In some embodiments, the substrate911, the light detectors903, the circuit913, the non-transparent layer915, and the transparent region923are formed in a first semiconductor device (e.g., an integrated circuit (IC)), whereas the prism901, the layers917/919/918, and the transparent region921are formed in a second semiconductor device (e.g., an optical IC). Once formed, the second semiconductor device is attached to the first semiconductor device as illustrated inFIG. 9to form the spectrometer900. Other methods to form the spectrometer900are possible and are fully intended to be included within the scope of the present disclosure.

In some embodiments, the prism901is formed of an optical material transparent to the incident light110, and the optical characteristics of the prism901are not configured to be adjustable. In other embodiments, the prism901comprises an electro-optic material such that the optical characteristics of the prism901are adjustable by a control parameter, e.g., an electrical voltage applied to the electro-optic material, or a temperature of the electro-optic material. In the illustrated embodiments, the circuit913applies an electrical voltage to the electro-optic material of the prism901to change at least one of the optical characteristics of the prism901.

FIG. 10illustrates a cross-sectional view of a spectrometer1000having a prism1051. The spectrometer1000has a substrate1021, light detectors1053, and a circuit1023. The substrate1021, the light detectors1053, and the circuit1023are the same or similar to the substrate411, the light detectors403, and the circuit413ofFIG. 4, respectively, thus details are not repeated. The spectrometer1000further has a transparent layer1011over the substrate1021and over the light detectors1053. In addition, a plurality of layers, such as1013,1015,1017and1019are over the transparent layer1011, and may each be referred to as a substrate. The layer1019is formed of a material that is transparent to the incident light110(at least in the region below the lens1031and in the light path), and the layer1013may be formed of one or more materials that may be non-transparent to the incident light110, in some embodiments.

As illustrated inFIG. 10, openings1001(e.g., empty spaces) are formed in the layer1013, the substrate1015, and the substrate1017. The prism1051is disposed in the openings1001. The prism1051may comprise a same or similar material as the prism901ofFIG. 9, thus details are not repeated. The shape and the location of the prism1051, together with the shapes and the locations of the openings1001, are designed to allow the light110to enter the prism1051from the left surface1051A of the prism1051and to exit the prism1051from the bottom surface1051B of the prism1051. An optional lens1031is formed over the openings1001and the layer1019to help focus the incident light110on the prism1051.

FIG. 10further illustrates movable MEMS arms1029under the prism1051. The movable MEMS arms1029may be, e.g., piezoelectric (PZT) beams, or bi-metallic beams such that the movable MEMS arms1029may be controlled by the circuit1023to adjust the position (e.g., rotate) of the prism1051, e.g., rotate along the direction1025or1027. Therefore, the movable MEMS arms1029may be used to adjust the angle of incidence of the incident light110. In some embodiments, the prism1051comprises an electro-optic material, and the circuit1023adjusts the optical characteristics of the prism1051by adjusting, e.g., a voltage applied to the electro-optic material, or a temperature of the electro-optic material. In some embodiments, the propagation angle of the light110in the prism1051is changed by changing the refractive index of the electro-optic material of the prism1051. Note that for simplicity, electrical connections between the circuit1023and other electrical components, such as light detectors1053, the movable MEMS arms1029, and the electro-optic material of the prism1051(if any), are not shown inFIG. 10.

FIG. 11illustrates a cross-sectional view of a spectrometer1100having a prism1151. The spectrometer1100has a substrate1101, light detectors1153, a circuit1103, and a transparent layer1111. The substrate1101, the light detectors1153, the circuit1103, and the transparent layer1111are the same or similar to the substrate311, the light detectors303, the circuit313, and the transparent layer315ofFIG. 3, respectively, thus details are not repeated.

The spectrometer1100further has a prism1151in a substrate1113, placed over the transparent layer1111. The prism1151is partially embedded in the substrate1113, and a top portion of the prism1151is disposed above an upper surface of the substrate1113. The substrate1113(e.g., silicon) may be non-transparent to the incident light110, and therefore, the light110enters the prism1151through top portions of a surface1151A and top portions of a surface1151C of the prism1151, where the top portions of1151A and the top portions of1151C are disposed above the upper surface of the substrate1113. An optional lens1115is formed over the prism, which optional lens1115helps to focus the light110on the prism1151. In embodiments where the optional lens1115is not formed, a transparent layer may be formed over the prism1151and over the substrate1113to protect the prism1151.

The prism1151is formed of an optical material. In some embodiments, the prism1151comprises an electro-optic material such that the optical characteristics of the prism1151can be adjusted. Details are the same or similar to the prism1051ofFIG. 10or the prism901ofFIG. 9, thus are not repeated. Note that inFIG. 10, the incident light110enters the prism1051from one surface of the prism (e.g.,1051A inFIG. 10). In contrast, inFIG. 11, the incident light110enters the prism1151from top portions of two surfaces1151A and1151C. For this reason, the light detectors1153are positioned symmetrically about a vertical center axis (not shown) of the prism1151inFIG. 11. InFIG. 10, the light detectors1053are position non-symmetrically about a vertical center axis of the prism1051(e.g., positioned on one side of the vertical center axis). InFIG. 9, since only portions of the light110entering the prism from the top portions of the surface901A pass through the transparent region923, the light detectors903are also positioned non-symmetrically about a vertical center axis of the prism901(e.g., positioned on one side of the vertical center axis). The prisms901,1051and1151inFIGS. 9, 10 and 11are illustrated to have a triangular shape as non-limiting examples. In other embodiments (not shown), the prism (e.g.,901,1051, and1151) may have other suitable shape such as a trapezoidal shape, a polygonal shape, or the like.

In some embodiments, the substrate1101, the light detectors1153, the circuit1103, and the transparent layer1111are formed in a first IC1180, whereas the layers and components above the transparent layer1111are formed in a second semiconductor device1190(e.g., an optical IC). Once formed, the second semiconductor device1190is attached to the first semiconductor device1180to form the spectrometer1100. Other methods to form the spectrometer1100are possible and are fully intended to be included within the scope of the present disclosure.

FIGS. 12A-12Cillustrate cross-sectional views of various portions of a spectrometer1200. As illustrated inFIG. 12A, the spectrometer1200comprises a substrate1201, light detectors1253, a circuit1203, light filters1251, and a transparent layer1211. The substrate1201, the circuit1203, the light detectors1253, and the transparent layer1211may be the same or similar to the substrate1101, the circuit1103, the light detectors1153, and the transparent layer1111ofFIG. 11, thus details are not repeated.

FIG. 12Billustrates a cross-sectional view of the light filters1251, which is the same or similar to the light filter501ofFIG. 5B. In particular, the light filter1251has layers1231and1233, which are the same or similar to the layers541and543ofFIG. 5B, respectively, in some embodiments. The light filter1251further has a transparent region1234, which is the same or similar to the transparent region545ofFIG. 5B, in the illustrated embodiment. For brevity, details are not repeated.

Referring back toFIG. 12A, the spectrometer1200further includes a transparent layer1210attached to the transparent layer1211. The transparent layer1210may be, e.g., a glass layer, a quartz layer, or the like. Above the transparent layer1210are mirrors1255formed in a layer1213, where the layer1213may be any suitable layer such as a silicon substrate.

FIG. 12Cillustrates a cross-sectional view of the mirror1255. As illustrated inFIG. 12C, the mirror1255comprise a V-shaped reflective layer1241, and a transparent region1243filling the recess of the reflective layer1241. Although not shown, the reflective layer1241may have other suitable shape such as a U-shape, a semispherical shape, or the like. The reflective layer1241is made of a reflective material that does not change the contents (e.g., wavelengths) of the light being reflected. Suitable material, such as silver, gold, or the like, may be used to form the reflective layer1241. The transparent region1243comprises a passive transparent material (e.g., a transparent material with non-adjustable optical characteristics), in an exemplary embodiment, although the transparent region1243may comprise an active transparent material (e.g., an electro-optic material that is transparent) such that its optical characteristics are adjustable.

As illustrated inFIG. 12A, an incident light110passes through the transparent layer1210, gets filtered and reflected by a light filter1251. The reflected light130travels through the transparent layer1210, gets reflected by a respective mirror1255, and the reflected light130from the mirror1255travels through the transparent layer1210again to reach a respective light detector1253. The light detectors1253may be any suitable light detector, e.g., the optoelectronic device with a V-shaped recess disclosed in U. S. Patent Publication No. 2014/0001521 A1. The locations of the light filters1251and the locations of the mirrors1255, as illustrated inFIG. 12A, may be switched to form alternative embodiments. In other words, in other embodiments, the mirrors1255are formed in the substrate1201at locations of the filters1251inFIG. 12A, and the light filters1251are formed in the substrate1213at locations of the mirrors1255inFIG. 12A.

The shape (e.g., V-shape, U-shape, semispherical shape) of the reflective layer1241of the mirror1255, the shape (e.g., V-shape, U-shape, semispherical shape) of the layers (e.g.,1231and1233) of the light filter1251, and/or the V-shaped recess of the light detector1253may improve the geometry of the spectrometer and improve the detection efficiency. In embodiments where the light filter1251or the mirrors1255use active materials (e.g. the layers1231,1233, or1243are electro-optic materials), the electro-optic material may be adjusted to change the filtered wavelength or the angle of incidence of the light110, thus improving the flexibility and accuracy of the spectrometer1200. In embodiments where the mirrors1255use passive transparent material, all of the active structures (e.g., the light detectors1253, the circuit1203, and the light filters1251with electro-optic material) of the spectrometer1200can be fabricated in a first IC, which first IC includes elements below the transparent layer1210inFIG. 12A. The mirrors1255may be fabricated in a second IC that does not have active structures, on the substrate1213. Having all active structures in one IC may simplify the design of the second IC comprising the mirrors1255, and may reduce the manufacturing cost of the spectrometer1200.

FIGS. 13, 14A-14B, 15, and 16illustrate various embodiments of spectrometers (e.g.,1200A,1200B,1200C, and1200D) that are similar to the spectrometer1200ofFIGS. 12A-12C, but with modifications. Unless otherwise specified, like reference numerals inFIGS. 12A, 13, 14A-14B, 15, and 16refer to the same or similar components, thus details are not repeated.FIG. 13illustrates a cross-sectional view of a spectrometer1200A. The spectrometer1200A inFIG. 13is similar to the spectrometer1200ofFIG. 12A, but with the mirrors1255and the layer1213replaced with a single mirror1256.

InFIG. 13, the mirror1256has a planar lower surface that is reflective. The mirror1256does not change the contents (e.g., wavelengths) of the light being reflected. The light110travels through the transparent layer1210, gets filtered and reflected by the light filter1251, the reflected light130from the light filter1251is reflected again by the mirror1256toward the light detector1253. In some embodiments, the light filter1251comprises an electro-optic material, and the optical characteristics of the light filter1251is adjusted to change the filtered wavelength and the various angles (e.g., angle of incidence, angle of reflection) of the light path. The spectrometer1200A uses a mirror1256in place of the IC comprising the plurality of mirrors1255(seeFIG. 12A), thereby simplifying the design and reducing the cost of the spectrometer1200A.

FIGS. 14A and 14Billustrate a cross-sectional view and a plan view of a spectrometer1200B, respectively, in an embodiment. In particular,FIG. 14Ais the cross-section view of the spectrometer1200B ofFIG. 14Balong cross-section E-E. For simplicity, not all features are illustrated inFIGS. 14A and 14B. As illustrated inFIG. 14B, the transparent layer1210has a U-shape and surrounds three sides of the region having the mirrors1255in the plan view. As a result, there is an empty space140(seeFIG. 14A) between the substrate1201and the layer1213. Additionally, the light filters1251are formed at the upper surface of the transparent layer1211and are at least partially exposed by the transparent layer1211. Similarly, the mirrors1255are formed at the lower surface of the layer1213and are at least partially exposed by the layer1213. Although not illustrated, each of the light filters1251and each of the mirrors1255may be attached to one or more respective MEMS arms (e.g., PZT beams, bi-metallic beams), and therefore, may be movable (e.g., able to tilt to the left or right, or move up-and-down). The MEMS arms may be controlled, e.g., by a control voltage, in real-time to change the light transmitted or reflected by the light filters1251(as shown inFIG. 2H) and/or the positions of the mirrors1255, thereby changing the various angles (e.g., angle of incidence, angle of reflection) of the light path. In some embodiments, the mirrors1255have a same or similar structure as the light filters1251, thus both the mirrors1255and the light filters1251are used for filtering light and reflecting light.

FIG. 15illustrates a cross-sectional view of a spectrometer1200C. The spectrometer1200C is similar to the spectrometer1200B, but with the transparent layer1210formed around the region of the mirrors1255and over the light filters1251. The transparent layer1210encircles the space140inFIG. 15. The light filters1251are formed below the upper surface of the transparent layer1211, thus are fixed (e.g., not movable). In contrast, the mirrors1255are exposed at the lower surface of the layer1213, and may be attached to MEMS arms (not illustrated), thus are movable. The light path (e.g.,110,130) of the spectrometer1200C includes portions in the transparent layer1210and portions in the space140. In some embodiments, the mirrors1255have a same or similar structure as the light filters1251, thus both the mirrors1255and the light filters1251are used for filtering light and reflecting light.

FIG. 16illustrates a cross-sectional view of a spectrometer1200D. The spectrometer1200D is similar to the spectrometer1200B, but with the transparent layer1210formed under the mirrors1255, and fills a space between the layer1213and the substrate1201. The mirrors1255are fixed (e.g., not movable) in the example ofFIG. 16. In contrast, the light filters1251are exposed at the upper surface of the transparent layer1211, and may be attached to MEMS arms (not illustrated), thus may be movable. In some embodiments, the mirrors1255have a same or similar structure as the light filters1251, thus both the mirrors1255and the light filters1251are used for filtering light and reflecting light.

FIG. 18illustrates a flow chart of a method3000of analyzing a light, in accordance with some embodiments. It should be understood that the embodiment method shown inFIG. 18is merely an example of many possible embodiment methods. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. For example, various steps as illustrated inFIG. 18may be added, removed, replaced, rearranged and repeated.

Referring toFIG. 18, at step3010, an optical signal is filtered using an array of light filters, the array of light filters comprising a first light filter and a second light filter, the first light filter letting through a first transmitted optical signal having a first wavelength, the second light filter letting through a second transmitted optical signal having a second wavelength different from the first wavelength. At step3020, the first transmitted optical signal and the second transmitted optical signal are detected.

Embodiments may achieve advantages. By forming an array or a matrix of light filters, each of which transmitting or reflecting a different light component with a different wavelength, spatial wavelength dispersion is achieved in a compact spectrometer design suitable for integration in semiconductor devices. By using electro-optic material for the light filters, the optical characteristics of each of the light filters may be adjusted over time to achieve temporal wavelength dispersion, thereby furthering reducing the size of the spectrometer through a trade-off between size and detection time. Various embodiments include spectrometers using passive interferential light filters, active interferential light filters, or prism-based light filters. The use of electro-optic material allows for easy adjustment of the optical characteristics of the light filters and design flexibility.

In an embodiment, a spectrometer includes a substrate, a plurality of light detectors in the substrate, and a plurality of light filters over the plurality of light detectors, each of the plurality of light filters transmitting a different wavelength or reflecting a different wavelength, each of the light filters aligned with a corresponding one of the plurality of light detectors.

The spectrometer of example 1, wherein the plurality of light filters are configured in an array.

The spectrometer of example 1, wherein the plurality of light filters are configured in a matrix.

The spectrometer of example 1, wherein each of the plurality of light filters comprises an electro-optic material, and optical characteristics of each of the plurality of light filters are configured to be adjustable.

The spectrometer of example 4, wherein the optical characteristics of each of the plurality of light filters comprise a wavelength transmitted or reflected by the each of the plurality of light filters.

The spectrometer of example 4, wherein the optical characteristics of each of the plurality of light filters are configured to be adjusted by changing an electrical field applied, an electrical voltage applied, or by changing a temperature of each of the plurality of light filters.

The spectrometer of example 1, wherein each of the plurality of light filters comprises a plurality of sublayers, each of the sublayers having a refractive index, wherein there is a step change between refractive indexes of adjacent sublayers.

The spectrometer of example 7, wherein a sublayer of the plurality of sublayers comprises a gas or a fluid.

The spectrometer of example 1, wherein the plurality of light filters comprise electro-optic materials, wherein the spectrometer further comprises a circuit in the substrate, wherein the circuit is electrically coupled to the plurality of light filters, and wherein the circuit is configured to change optical characteristics of the plurality of light filters over time.

The spectrometer of example 9, further comprising: a plurality of first transparent regions at least partially in the substrate and laterally adjacent to the plurality of light detectors; and a plurality of second transparent regions over the substrate and at least partially between the plurality of light filters and the plurality of light detectors.

In an embodiment, a spectrometer includes a substrate, a plurality of light detectors in the substrate, a first layer over the substrate, and a prism at least partially in the first layer, the prism comprising an electro-optic material.

The spectrometer of example 11, further comprising a circuit in the substrate, wherein the circuit is electrically coupled to the prism, wherein the circuit is configured to adjust optical characteristics of the prism.

The spectrometer of example 11 or 12, further comprising a first opening in the first layer, wherein the prism is at least partially in the first opening, wherein the spectrometer further comprises movable microelectromechanical systems (MEMS) arms attached to the prism, wherein the movable MEMS arms are configured to mechanically adjust a position of the prism.

The spectrometer of example 11 or 12 further comprising a lens over the prism, wherein the lens is configured to focus light on two intersecting surfaces of the prism.

In an embodiment, a method includes filtering an optical signal using an array of light filters, the array of light filters comprising a first light filter and a second light filter, the first light filter letting through a first transmitted optical signal having a first wavelength, the second light filter letting through a second transmitted optical signal having a second wavelength different from the first wavelength, and detecting the first transmitted optical signal and the second transmitted optical signal.

The method of example 15, wherein the first light filter comprises a first electro-optic material different from a second electro-optic material of the second light filter.

The method of example 16, wherein the method further comprises: after detecting the first transmitted optical signal and the second transmitted optical signal, changing first optical characteristics of the first light filter and changing second optical characteristics of the second light filter; after the changing, filtering the optical signal using the array of light filters, the first light filter letting through a third transmitted optical signal with a third wavelength, the second light filter letting through a fourth transmitted optical signal with a fourth wavelength different from the third wavelength; and detecting the third transmitted optical signal and the fourth transmitted optical signal.

The method of example 17, wherein the changing comprises changing a voltage, or a temperature of each of the array of light filters.

The method of example 15, wherein the first light filter reflects a first reflected optical signal having a third wavelength, and the second light filter reflects a second reflected optical signal having a fourth wavelength different from the third wavelength, wherein the method further comprises detecting the first reflected optical signal and the second reflected optical signal.

The method of example 19, further comprising: after detecting the first transmitted optical signal, the second transmitted optical signal, the first reflected optical signal, and the second reflected optical signal, changing optical characteristics of the array of light filters such that wavelengths of transmitted optical signals and wavelengths of reflected optical signals are changed; after changing the optical characteristics of the array of light filters, filtering the optical signal using the array of light filters, wherein the first light filter lets through a third transmitted optical signal and reflects a third reflected optical signal, and the second light filter lets through a fourth transmitted optical signal and reflects a fourth reflected optical signal; and detecting the third transmitted optical signal, the fourth transmitted optical signal, the third reflected optical signal, and the fourth reflected optical signal.