CN115389021B - A polarization-insensitive high-resolution chip spectrometer - Google Patents

Abstract

The invention provides a polarization insensitive high-resolution chip spectrometer, which adopts time division multiplexing to 3 inputs, and can realize a spectrometer with 3x (N-2) channels and 1/3 delta lambda of wavelength interval only by N output ports, and the designed AWG has the channel interval of delta lambda. After determining the waveguide parameters, the occupation area of the phase region of the AWG can be greatly reduced because the radius R of the first and second free transmission regions of the AWG is inversely proportional to the output waveguide wavelength interval. The novel microchip spectrometer provided by the invention has the advantages of super-compact size, high resolution and realization of a large number of wavelength channels by reducing the number of receiving channels, and has a very good prospect for a miniaturized spectrum analysis system.

Description

Polarization insensitive high-resolution chip spectrometer

Technical Field

The invention relates to the field of optical waveguide devices and sensing detection, in particular to a polarization insensitive high-performance microchip spectrometer with high resolution and large bandwidth.

Background

The spectrometer recognizes a specific substance by detecting an absorption/reflection spectrum of light after passing through a sample to be measured or by monitoring an intensity change at a known wavelength, and has an important role in the fields of environmental monitoring, chemical detection, industrial and agricultural production, medical diagnosis, astronomical detection, and the like. Conventional commercial spectrometers are composed primarily of discrete components such as dispersive gratings, tunable filters and photodetectors, but they are typically bulky and expensive. On-chip spectrometers employing integrated photon technology have been intensively studied in recent years due to their ultra-compact size, high reliability, low cost, low power consumption, and the possibility of hybrid integration on the same chip as the light source and/or photodetector. In particular, the use of Complementary Metal Oxide Semiconductor (CMOS) based silicon photofabrication processes can enable mass production of on-chip spectrometers with greatly reduced costs. In recent years, with rapid development of fields of smart home, wearable equipment, health monitoring and the like, miniaturized, light-weight and low-cost chip spectrometers are urgent, and are hot spots in spectrometer research.

Optical waveguide-based on-chip spectrometers can be largely divided into three categories. The first is a Fourier Transform Spectrometer (FTS) that uses a set of mach-zehnder interferometers (MZI) with linearly increasing path length differences (also known as spatially heterodyning FTS, SH-FTS) or with a balanced MZI to tune an arm using thermo-optic or electro-optic effects. An important advantage of FTS is Fellgett multiplexing advantage, which allows for a higher signal to noise ratio of FTS. However, for SH-FTS, there is a tradeoff between spectral resolution δλ and bandwidth BW (bw=n/2×δλ, where N is the number of MZI) due to the limited chip size. In a tunable MZI-based FTS, the measurement time is very long due to thermo-optic effects, and the power consumed to heat one arm of the MZI is very large in order to create sufficient optical path difference to achieve high resolution. In addition, high thermal power can also affect the stability of the measurement and cause non-linearity problems, complicating calibration of spectral reduction. The second is to use a filter array, such as a micro-ring resonator array. However, ring resonators are generally very susceptible to fabrication errors and have a limited Free Spectral Range (FSR). The third type is based on dispersive elements such as Echelle Diffraction Gratings (EDGs), arrayed Waveguide Gratings (AWGs). Despite their high stability, a disadvantage is that the device footprint is proportional to resolution, and high spectral resolution and large channel numbers are difficult to combine simultaneously. In particular on material platforms with high refractive index differences, such as SOI platforms, the spectral performance of EDG/AWG deteriorates rapidly with resolution up to sub-nanometer levels. On the other hand, for high refractive index platforms, their waveguides tend to have high structural birefringence, which makes spectrometers based on them very sensitive to polarization. For unpolarized input light there will be 3dB of additional loss, resulting in a reduced signal-to-noise ratio of the spectrometer. Thus, additional control over the polarization state of the input light is required, but this complicates the measurement system and is not suitable for most field test applications.

Therefore, a chip spectrometer that can solve the above-mentioned difficulties becomes particularly important, and particularly with the development of portable sensors and miniaturized on-chip detection systems in recent years, the demand for such chip spectrometers is urgent.

Disclosure of Invention

To meet the requirements of miniaturization, high resolution, low loss, low polarization wavelength drift and low polarization dependent loss of spectrometers. The invention provides a polarization insensitive high-resolution chip spectrometer.

The invention aims at realizing the following technical scheme:

A polarization insensitive high-resolution chip spectrometer comprises 3 polarization processors, two groups of input waveguides, a first free transmission area, an array waveguide with a constant length difference delta L between adjacent array waveguides, a second free transmission area, two groups of output waveguides and a detector, wherein each group of input waveguides comprises 3 input waveguides, 3 input waveguides are time division multiplexed, and each group of output waveguides comprises N output waveguides #j _a or #j _b (j=1, 2,., N);

The polarization processor is used for decomposing incident light with random polarization states into two identical polarized lights TE _a and TE _b and inputting the two identical polarized lights into two groups of input waveguides, wherein N outputs corresponding to TE _a are #j _a,TE_b and N outputs corresponding to TE _b. One of the output ends of the two groups of input waveguides is connected with the first free transmission area, the other group of the output ends of the two groups of output waveguides is connected with the second free transmission area, the first free transmission area and the second free transmission area are connected through the array waveguides with constant length difference delta L between the adjacent array waveguides, and the output ends of the two groups of output waveguides are connected with the detector.

Further, the channel spacing between the input waveguides in each group of input waveguides isThe channel spacing of the N waveguides in each set of output waveguides is Δλ.

Still further, the following relationship is satisfied between three inputs of the corresponding TE _a in each set of input waveguides and the corresponding N outputs #j _a in each set of output waveguides and between three inputs of the corresponding TE _b in each set of input waveguides and the corresponding N outputs #j _b in each set of output waveguides

n_sd_asinθ_i+n_aΔL+n_sd_asinβ_j＝mλ_{i_j}(i＝1,2,3;j＝1,2,...,N-1,N)

Where subscripts i and j denote the input waveguide ordinal number and the output waveguide ordinal number, respectively. n _s and n _a are the effective refractive indices in the first and second free transmission regions and the arrayed waveguide at wavelength lambda _{i_j} (input waveguide ordinal i, output waveguide ordinal j). d _a is the constant projection period of the end point of the array waveguide on the tangent to the grating pole. m is the diffraction order, θ _i is the angle between the input waveguide #i and the central axes of the first and second free transmission regions, and β _j is the angle between the output waveguide #j and the central axes of the first and second free transmission regions.

A polarization insensitive high resolution chip spectrometer comprises 1 polarization processor, two 1 x 3 optical switches, two groups of input waveguides, a first free transmission area, an array waveguide with constant length difference delta L between adjacent array waveguides, a second free transmission area, two groups of output waveguides and a detector. Wherein the input waveguides comprise 3 input waveguides, and the output waveguides comprise N output waveguides;

The polarization processor is used for decomposing incident light with random polarization states into two identical polarized lights TE _a and TE _b, and TE _a and TE _b are respectively connected with the input end of the 1X 3 optical switch;

The output ends of the two groups of input waveguides and one of the input ends of the two groups of output waveguides are connected with a first free transmission area, the other group of output ends of the two groups of output waveguides are connected with a second free area, the first free transmission area and the second free area are connected through array waveguides with constant length difference delta L between adjacent array waveguides, and the output ends of the two groups of output waveguides are connected with a detector.

Further, the channel spacing between the input waveguides in each group of input waveguides isThe channel spacing of the N waveguides in each set of output waveguides is Δλ.

Still further, the following relationship is satisfied between three inputs of the corresponding TE _a in each set of input waveguides and the corresponding N outputs #j _a in each set of output waveguides and between three inputs of the corresponding TE _b in each set of input waveguides and the corresponding N outputs #j _b in each set of output waveguides

n_sd_asinθ_i+n_aΔL+n_sd_asinβ_j＝mλ_{i_j}(i＝1,2,3;j＝1,2,...,N-1,N)

Where subscripts i and j denote the input waveguide ordinal number and the output waveguide ordinal number, respectively. n _s and n _a are the effective refractive indices in the first and second free transmission regions and the arrayed waveguide at wavelength lambda _{i_j} (input waveguide ordinal i, output waveguide ordinal j). d _a is the constant projection period of the end point of the array waveguide on the tangent to the grating pole. m is the diffraction order, θ _i is the angle between the input waveguide #i and the central axes of the first and second free transmission regions, and β _j is the angle between the output waveguide #j and the central axes of the first and second free transmission regions.

A polarization insensitive high-resolution chip spectrometer comprises an input waveguide, a first free transmission area, an array waveguide with a constant length difference delta L between adjacent array waveguides, a second free transmission area, an output waveguide and a detector, wherein the input waveguide comprises 3 input waveguides, the 3 input waveguides are subjected to time division multiplexing, the output waveguide comprises N output waveguides, the output end of the input waveguide is connected with the first free transmission area, the input end of the output waveguide is connected with the first free transmission area, the first free transmission area is connected with the first free transmission area through the array waveguide, and the output end of the output waveguide is connected with the detector.

Further, the channel spacing between the input waveguides in the input waveguides isThe channel spacing of N output waveguides in the output waveguides is delta lambda.

Further, the following relationship is satisfied between three input waveguides #i of the input waveguides and N output waveguides #j of the output waveguides

n_sd_asinθ_i+n_aΔL+n_sd_asinβ_j＝mλ_i-j(i＝1,2,3;j＝1,2,...,N-1,N)

Where subscripts i and j denote the input waveguide ordinal number and the output waveguide ordinal number, respectively. n _s and n _a are the effective refractive indices in the first and second free transmission regions and the arrayed waveguide at wavelength lambda _{i_j} (input waveguide ordinal i, output waveguide ordinal j). d _a is the constant projection period of the end point of the array waveguide on the tangent to the grating pole. m is the diffraction order, θ _i is the angle between the input waveguide #i and the central axis of the first free transmission region, and β _j is the angle between the output waveguide #j and the central axis of the second free transmission region.

Still further, a1 x 3 optical switch is included, wherein an input terminal of the 1 x 3 optical switch is used for inputting light, and 3 output terminals of the 1 x 3 optical switch are connected to an input terminal of the input waveguide.

The invention has the advantages of 1, high resolution, large bandwidth and insensitive polarization, and 2, is suitable for various material platforms, such as SiO ₂, silicon nitride (Si ₃N₄), silicon (Si), geSi and other material platforms.

Drawings

FIG. 1 is a high resolution chip spectrometer architecture for polarization sensitive waveguide structures in accordance with the present invention;

FIG. 2 is a schematic diagram of another high resolution chip spectrometer architecture for polarization sensitive waveguide structures in accordance with the present invention;

FIG. 3 is a high resolution chip spectrometer architecture for polarization insensitive waveguide structures in accordance with the present invention;

FIG. 4 is a schematic diagram of another high resolution chip spectrometer architecture for polarization insensitive waveguide structures in accordance with the present invention;

FIG. 5 shows two examples of embodiments of the X-polarization processor of FIGS. a and b;

FIG. 6 is an exemplary embodiment of the S-1×3 optical switch of FIGS. 2 and 4;

FIG. 7 shows two exemplary F-detector embodiments;

FIG. 8 is an exemplary embodiment of the structure of FIG. 1 utilizing the present invention;

FIG. 9 is a schematic diagram of the micro spectrometer shown in FIG. 8 utilizing three inputs and N outputs to produce 3× (N-2) wavelengths with a wavelength spacing of 1/3 Δλ of the wavelength spacing of the N output waveguides;

FIG. 10 is a graph of transmission spectra of the fabricated structure of FIG. 8 for all 29 output channels corresponding to three input waveguides under TE and TM polarization;

FIG. 11 is a graph of 81 channels obtained by combining three inputs for the configuration of FIG. 8, with wavelength intervals of 0.4 nm;

Detailed Description

The invention is further described below with reference to the accompanying drawings.

Referring to FIG. 1, a novel high resolution chip spectrometer of the present invention includes 3X-polarization processors, two sets of A-input waveguides, B-first free transmission regions, C-array waveguides with a constant length difference DeltaL between adjacent array waveguides, D-second free transmission regions, two sets of E-output waveguides, F-detectors. Wherein the A-input waveguide comprises 3 input waveguides, the E-output waveguide comprises N output waveguides #j _a or #j _b (j=1, 2, once again, n.). The X-polarization processor splits incident light of random polarization into two identical polarized light TEs _a and TE _b, and the N outputs corresponding to TE _a are #j _a,TE_b and the N outputs corresponding to TE _a are #j _b. The corresponding three inputs of TE _a in A and the corresponding N outputs #j _b of E are connected with the D-second free transmission area, the corresponding three inputs of TE _b in A and the corresponding N outputs #j _a of E are connected with the B-first free transmission area, B and D are connected through C, and output waveguides #j _a and #j _b are connected with the F-detector.

Referring to fig. 2, since the 3X-polarization processors employed by the microchip spectrometer of the present invention are time division multiplexed, the three X-polarization processors can be replaced with one X-polarization processor, which connects two S-1×3 optical switches. In this case, the structure of FIG. 1 of the present invention can be changed to the structure of FIG. 2, namely, 1X-polarization processor, two S-1X 3 optical switches, two groups of A-input waveguides, B-first free transmission area, C-array waveguides with constant length difference DeltaL between adjacent array waveguides, D-second free transmission area, two groups of E-output waveguides, F-detector are needed. Wherein the A-input waveguide comprises 3 input waveguides, the E-output waveguide comprises N output waveguides #j _a or #j _b (j=1, 2, once again, n.). The X-polarization processor splits incident light of random polarization into two identical polarized lights TE _a and TE _b, and TE _a and TE _b are connected to the input end of S. The three outputs of S and N outputs #j _b of E corresponding to TE _a are connected to the D-second free transport region, the three outputs of S and N outputs #j _a of E corresponding to TE _b are connected to the B-first free transport region, B and D are connected through C, and output waveguides #j _a and #j _b are connected to the F-detector.

Referring to FIG. 3, when each cell structure A, B, C, D, E, F in the microchip spectrometer is insensitive to the polarization state of the input light, the structure of FIG. 1 of the present invention can be simplified to the structure of FIG. 3, i.e., the need for an A-input waveguide, a B-first free transmission region, an array waveguide with a constant length difference ΔL between C-adjacent array waveguides, a D-second free transmission region, an E-output waveguide, and an F-detector. Wherein the a-input waveguide comprises 3 input waveguides, the E-output waveguide comprises N output waveguides #j (j=1, 2.), N), A and B are connected, B and D are connected through C, D and E are connected, E is connected with a group of F arrays.

Referring to FIG. 4, when each unit structure A, B, C, D, E, F, S in the microchip spectrometer is insensitive to the polarization state of the input light, the structure of FIG. 2 of the present invention can be simplified to the structure of FIG. 4, i.e., 1S-1×3 optical switch, A-input waveguide, B-first free transmission region, C-array waveguide with constant length difference ΔL between adjacent array waveguides, D-second free transmission region, E-output waveguide, F-detector. Wherein the a-input waveguide comprises 3 input waveguides and the E-output waveguide comprises N output waveguides #j (j=1, 2,., N). The output of S is connected with A, A is connected with B, B is connected with D through C, D is connected with E, E is connected with a group of F arrays.

Referring to fig. 5, the X-polarization processor is responsible for converting the input light of random polarization in the fiber into TE polarization in the waveguides 2, 3. Two exemplary implementations of the X-polarization processor are shown in fig. 5, where 4 in fig. 5 (a) is the splitting of the input light of random polarization in the fiber into two orthogonal components with respect to the output waveguides 2 and 3, and 5 in fig. 5 (b) is the coupling of the light of random polarization in the fiber into TE ₀ and TM ₀ polarization in the input waveguide 1. The first polarization processor can couple two orthogonal polarization components in the optical fiber to TE basic modes in the waveguide respectively for transmission by using a 2D grating coupler, and the second polarization processor couples the two orthogonal polarization components in the optical fiber to TE (TRANSVERSE ELECTRIC, transverse electricity) and TM (TRANSVERSE MAGNETIC, transverse magnetism) basic modes 5 in the waveguide respectively, and simultaneously the TM basic modes are rotated into TE basic modes again, and finally become two paths of TE basic modes.

Fig. 6 is an example of an implementation for the S-1 x 3 optical switch of fig. 2 and 4. The S-1 x 3 optical switch is realized by cascading 2 symmetrical MZIs of 1 x 2, one metal heater 8 is placed on each arm of each MZI, and the selection of one of the two output ends of the MZI can be realized by adjusting the voltage on the metal heater 8. Proper adjustment of the heating voltage on each MZI can select one of the S-1 x 3 optical switches to output, ensuring that the two paths of te_a and te_b light in fig. 2 are only output from the corresponding ports at each time;

Fig. 7 shows two exemplary embodiments of the F-detector, for which a two-way detection structure is suitable, i.e. the left-hand diagram of fig. 7, and the photosensitive region absorbs both TE light 6 and 7, and for which a polarization-insensitive waveguide structure, i.e. the right-hand diagram of fig. 7, and the photosensitive region absorbs the input light 6.

FIG. 8 shows an example of the structure of FIG. 1 of the present invention, where the AWG operates in a counter-propagating mode, with a channel spacing between the three input waveguides in A ofThe channel spacing of N waveguides in E is Deltalambda, the following relationship is satisfied between three inputs corresponding to TE _a in A and N outputs corresponding to E #j _b and between three inputs corresponding to TE _b in A and N outputs corresponding to E #j _a

n_sd_asinθ_i+n_aΔL+n_sd_asinβ_j＝mλ_{i_j}(i＝1,2,3;j＝1,2,...,N-1,N)

Where subscripts i and j denote the input waveguide ordinal number and the output waveguide ordinal number, respectively. n _s and n _a are the effective refractive indices in the free transmission regions (B and D) and C-array waveguides at wavelength lambda _{i_j} (input waveguide ordinal i, output waveguide ordinal j). d _a is the constant projection period of the end point of the array waveguide on the tangent to the grating pole. m is the diffraction order, θ _i is the angle between the input waveguide #i and the central axis of the B-first free transmission region (D-second free transmission region), and β _j is the angle between the output waveguide #j and the central axis of the B-first free transmission region (D-second free transmission region).

The radius of the B-first free transport region (D-second free transport region) can be expressed by the following formula:

Wherein n _gs and n _ga are the group refractive indices of the B-first free transmission region (D-second free transmission region) and the C-array waveguide, respectively. D _o is the spacing between adjacent output waveguides on B and D, D _a is the constant projection period of the end points of the array waveguide on the tangent of the grating pole, λ ₀ and Δλ are the designed center wavelength and channel spacing, respectively, and θ _i is the angle between the input waveguide #i and the central axis of the B-first free transmission region (D-second free transmission region).

FIG. 9 is a graph showing the spectral response of a micro spectrometer of the present invention to produce a channel count of 3X (N-2) with a wavelength spacing of 1/3 Deltaλ, where Deltaλ is the channel wavelength spacing between adjacent output waveguides. Three input waveguides (i=1, 2, 3) are time division multiplexed, i.e. only one input waveguide is excited at a time, and for each input waveguide, a set of N output wavelength signals (λ _{i_1},λ_{i_2},…,λ_{i_N-1},λ_{i_N}) are corresponding to a pitch Δλ. Since the wavelength interval between the three input waveguides is designed to be 4/3 Δλ, the second wavelength set corresponding to the input waveguide 2 has a wavelength shift of 4/3 Δλ and the third wavelength set 8/3 Δλ corresponding to the input waveguide 3, compared to the first wavelength set corresponding to the input waveguide 1. By combining these three wavelength sets, we can obtain a wavelength set with a uniform wavelength interval of 1/3 Deltalambda and a channel number of 3× (N-2).

The invention will be further elucidated below with respect to a practical example:

The chip AWG spectrometer is manufactured on an SOI silicon wafer, the thickness of a surface silicon layer is 220nm, and the thickness of a buried oxide layer is 2 mu m. First, the pattern of the micro-spectrometer shown in FIG. 8 was transferred into a layer of Photoresist (PR) using 193nm lithography and into a SiO ₂ hard mask by inductively coupled plasma etching. A layer of 70nm thick silicon is then etched to form a 2D grating coupler, i.e., an X-polarization processor. Subsequently, the remaining 150nm thick silicon is completely etched to form the channel waveguide. Finally, a SiO ₂ upper cladding layer with a thickness of 2 μm is deposited by Plasma Enhanced Chemical Vapor Deposition (PECVD).

Light from a tunable light source is first passed through a fiber polarization controller that can change the polarization direction of the input light by rotating three fiber loops and then coupling the light through a 2D grating coupler to the first input port of the inventive microchip (AWG) spectrometer. After light is transmitted through the AWG, it is collected at 29 output ports using 2D grating couplers, respectively. Next, the light is coupled to the second and third input ports of the AWG, respectively, and collected again at 29 output ports. FIG. 10 is a graph of transmission spectra of all 29 output channels of the fabricated structure of FIG. 8 corresponding to three input waveguides under TE and TM polarization. Due to the optimized layout design of the AWG spectrometer, all output channels achieve good spectral shape and uniformity. Fig. 11 shows the wavelength set of 81 channels obtained by combining three inputs with the structure shown in fig. 8, with a wavelength interval of 0.4nm.

The AWG spectrometer has the key advantages that the time division multiplexing is adopted for three inputs, only N output ports are needed to realize a spectrometer with 3× (N-2) channels and 1/3 delta lambda of wavelength interval, and the designed AWG has the channel interval of delta lambda. After determining the waveguide parameters, since the radius R of the B-first free transmission region (D-second free transmission region) of the AWG is inversely proportional to the output waveguide wavelength interval, compared with a1×3 (N-2) AWG spectrometer with the same wavelength interval of 1/3 Δλ, the radius R of the AWG spectrometer proposed by the present invention is reduced to 1/3 of that of the conventional AWG spectrometer, and the occupation area of the phase region of the AWG is greatly reduced.

The novel microchip spectrometer provided by the invention has the advantages of super-compact size, high resolution and realization of a large number of wavelength channels by reducing the number of receiving channels, and has a very good prospect for a miniaturized spectrum analysis system.

Furthermore, while the present invention provides a novel microchip spectrometer and provides some embodiments of critical devices, it is within the scope of the present invention for other designs and modifications of critical devices to include, but not limited to, the use of wavelength spacingIt is within the scope of the present invention that the functions they ultimately perform are identical, either an off-chip optical switch or a different type of on-chip optical switch, a different type of wavelength division multiplexer, e.g., based on etched diffraction gratings, etc.

Claims (4)

1. The polarization insensitive high-resolution chip spectrometer is characterized by comprising 3 polarization processors, two groups of input waveguides, a first free transmission area, an array waveguide with a constant length difference delta L between adjacent array waveguides, a second free transmission area, two groups of output waveguides and a detector, wherein each group of input waveguides comprises 3 input waveguides and 3 input waveguides are time division multiplexed;

The polarization processor is used for decomposing incident light in a random polarization state into two identical polarized lights TE _a and TE _b and inputting the two groups of input waveguides, one of the output ends of the two groups of input waveguides and the input ends of the two groups of output waveguides is connected with the first free transmission area, the other group of input ends of the two groups of output waveguides is connected with the second free transmission area, the first free transmission area and the second free transmission area are connected through array waveguides with constant length difference delta L between adjacent array waveguides, and the output ends of the two groups of output waveguides are connected with the detector;

The 3X-polarization processors adopt time division multiplexing, and the channel interval between the input waveguides in each group of input waveguides is Δλ, where the channel spacing of N output waveguides in each group of output waveguides is Δλ;

The following relationship is satisfied between 3 inputs of the corresponding TE _a in each set of input waveguides and N outputs of the corresponding set of output waveguides

n_sd_asinθ_i+n_aΔL+n_sd_asinβ_j＝mλ_i-j(i＝1,2,3;j＝1,2,…,N-1,N)

The subscripts i and j respectively represent the input waveguide ordinal number and the output waveguide ordinal number, n _s and n _a are effective refractive indexes in the first free transmission area, the second free transmission area and the array waveguide at a wavelength lambda _{i_j} of the input waveguide ordinal number i and the output waveguide ordinal number j, d _a is a constant projection period of an endpoint of the array waveguide on a tangent line of a grating pole, m is a diffraction order, theta _i is an included angle between the input waveguide i and central axes of the first free transmission area and the second free transmission area, and beta _j is an included angle between the output waveguide j and the central axes of the first free transmission area and the second free transmission area.

2. The polarization insensitive high-resolution chip spectrometer is characterized by comprising 1 polarization processor, two 1 multiplied by 3 optical switches, two groups of input waveguides, a first free transmission area, an array waveguide with constant length difference delta L between adjacent array waveguides, a second free transmission area, two groups of output waveguides and a detector, wherein the input waveguides comprise 3 input waveguides, and the output waveguides comprise N output waveguides;

The polarization processor is used for decomposing incident light with random polarization states into two identical polarized lights TE _a and TE _b, and TE _a and TE _b are respectively connected with the input end of the 1X 3 optical switch;

the output ends of the two groups of input waveguides and one of the input ends of the two groups of output waveguides are connected with a first free transmission area, the other group of the output ends of the two groups of output waveguides are connected with a second free area, the first free transmission area and the second free area are connected through array waveguides with constant length difference delta L between adjacent array waveguides, and the output ends of the two groups of output waveguides are connected with a detector;

the channel spacing between the input waveguides in each group of input waveguides is The channel interval of N output waveguides in each group of output waveguides is delta lambda;

The following relationship is satisfied between 3 inputs of the corresponding TE _a in each set of input waveguides and N outputs of the corresponding set of output waveguides

n_sd_a sinθ_i+n_aΔL+n_sd_a sinβ_j＝mλ_i-j(i＝1,2,3;j＝1,2,…,N-1,N)

The subscripts i and j respectively represent the input waveguide ordinal number and the output waveguide ordinal number, n _s and n _a are effective refractive indexes in the first free transmission area, the second free transmission area and the array waveguide at a wavelength lambda _{i_j} of the input waveguide ordinal number i and the output waveguide ordinal number j, d _a is a constant projection period of an endpoint of the array waveguide on a tangent line of a grating pole, m is a diffraction order, theta _i is an included angle between the input waveguide i and central axes of the first free transmission area and the second free transmission area, and beta _j is an included angle between the output waveguide j and the central axes of the first free transmission area and the second free transmission area.

3. The polarization insensitive high-resolution chip spectrometer is characterized by comprising an input waveguide, a first free transmission area, an array waveguide with a constant length difference delta L between adjacent array waveguides, a second free transmission area, an output waveguide and a detector, wherein the input waveguide comprises 3 input waveguides and 3 input waveguides are time division multiplexed, the output waveguide comprises N output waveguides, the output end of the input waveguide is connected with the first free transmission area, the input end of the output waveguide is connected with the first free transmission area, the first free transmission area is connected with the first free transmission area through the array waveguide, and the output end of the output waveguide is connected with the detector;

the channel interval between the input waveguides in the input waveguides is The channel interval of N output waveguides in the output waveguides is delta lambda;

The following relationship is satisfied between 3 inputs of the corresponding TE _a in each set of input waveguides and N outputs of the corresponding set of output waveguides

n_sd_a sinθ_i+n_aΔL+n_sd_a sinβ_j＝mλ_i-j(i＝1,2,3;j＝1,2,…,N-1,N)

The subscripts i and j respectively represent the input waveguide ordinal number and the output waveguide ordinal number, n _s and n _a are effective refractive indexes in the first free transmission area, the second free transmission area and the array waveguide at a wavelength lambda _{i_j} of the input waveguide ordinal number i and the output waveguide ordinal number j, d _a is a constant projection period of an endpoint of the array waveguide on a tangent line of a grating pole, m is a diffraction order, theta _i is an included angle between the input waveguide i and central axes of the first free transmission area and the second free transmission area, and beta _j is an included angle between the output waveguide j and the central axes of the first free transmission area and the second free transmission area.

4. A spectrometer as claimed in claim 3, further comprising a1 x 3 optical switch, wherein the input of the 1 x 3 optical switch is for inputting light and wherein the 3 outputs of the 1 x 3 optical switch are connected to the input of the input waveguide.