Reconfigurable on-chip spectrometer based on low-loss gst superlattice phase change material

Abstract

The application belongs to the field of reconfigurable on-chip spectrometer, and specifically discloses a reconfigurable on-chip spectrometer based on a low-loss GST superlattice phase change material. The application combines the GST-SL2 material with a double-cascade micro-ring array architecture to achieve a breakthrough in device performance, and a large number of spectral responses can be generated with only a limited number of micro-ring resonators on the chip, while supporting flexible regulation of spectral resolution and working bandwidth to meet the customized needs of different application scenarios. A resolution regulation array is composed of a plurality of first MRRs arranged at equal intervals along the extension direction of the bus waveguide, and the resonant micro-ring lengths of the first MRRs increase. This cascade design significantly enhances the overall regulation capability through the synergistic effect of multiple MRRs, ensuring that the sampling points can uniformly cover the entire working bandwidth of the on-chip spectrometer. The measurement bandwidth regulation array divides the working bandwidth into multiple channels, successfully enhancing the non-correlation of the system response function and providing a reliable foundation for spectral reconstruction.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of reconfigurable on-chip spectrometer, more particularly, it relates to a reconfigurable on-chip spectrometer based on low-loss GST (Ge-Sb-Te) superlattice phase change material. BACKGROUND

[0002] Spectrometers play a vital role in biochemical analysis, environmental monitoring, aerospace, and other fields. However, traditional free-space spectrometers are usually bulky and expensive, limiting their popularity in cost-sensitive portable applications. In recent years, researchers have developed various miniaturized spectrometer technologies, including designs based on compact dispersive elements and Fourier transform techniques, significantly reducing the size of the spectrometer. Despite this, there is still a trade-off between occupied space and performance. To address this issue, on-chip spectrometers based on narrowband filters have emerged, offering significant advantages in miniaturization and achieving full flattening without the need for long optical paths. With the development of computing power and compressed sensing theory, new spectrometers based on reconstruction algorithms have gradually become a research hotspot. These spectrometers combine reconstruction algorithms with various spectrometer designs, further improving the performance of miniaturized spectrometers, making them one of the most promising research directions. However, achieving a balance between small size, large working bandwidth, and high resolution in small spectrometers remains a challenging task.

[0003] The core performance indicators of on-chip spectrometers are working bandwidth, wavelength resolution, and chip device area. The performance of current on-chip spectrometers still needs to be balanced among the three, and it is difficult to achieve high performance in all three. There are currently four main technical routes for on-chip spectrometers:

[0004] (1) Miniaturized dispersive optical system, which uses miniaturized gratings, waveguides, and other dispersive elements to disperse different wavelengths of light to a detector array. Typical structures include concave gratings, grating-Fresnel lens integration, photonic crystals, and arrayed waveguide gratings. The volume is generally in centimeters. The advantages are: the structure is relatively mature, and the resolution in the visible range can reach about 10 nm; the disadvantages are: the reduction in volume leads to a reduction in optical path, resulting in a decrease in resolution; the manufacturing tolerance of waveguides (such as sidewall roughness) limits further miniaturization.

[0005] (2) Narrowband filter system, which directly samples the spectrum within the working bandwidth using adjustable filters (such as Fabry-Perot resonant cavities), fixed filter arrays / linearly varying filters. The volume is generally in millimeters. The advantages are: it can be integrated on-chip, greatly reducing the size of the spectrometer, and the resolution of the spectrometer is 1-25 nm depending on the number of channels; the disadvantages are: the process of integrating a large number of filter channels on-chip is difficult, the number of filter channels limits the resolution, temperature stability, and complex manufacturing process.​

[0006] (3) Fourier transform spectrometer, which is based on the interference phenomenon of light and the mathematical method of Fourier transform. Specifically, by measuring the interference pattern of the interference light intensity with the change of the optical path difference, and using Fourier transform to convert the time-domain interference signal to frequency-domain spectral information, high-resolution spectral data is obtained. The general volume is in centimeter level, and the working waveband is generally in the mid-infrared. The advantages are: only a single photodetector is needed, the cost is low; the signal-to-noise ratio is high, the resolution is high, and it can reach pm level; the defects are: the refractive index of the waveguide changes with temperature, resulting in phase drift (need temperature control or real-time calibration), high-precision Fourier transform and phase correction algorithm are needed; the maximum optical path difference of the miniaturized system is limited, the resolution is lower than that of the traditional Fourier transform spectrometer, and it is difficult to be extremely miniaturized.

[0007] (4) Reconstruction spectrometer, which is a new type of miniaturized technology for realizing spectral analysis through coding-decoding strategy. Its core idea is to encode the spectral information into the response signal of the detector array, and then reconstruct the original spectrum through algorithm. The general volume is in millimeter level. The advantages are: it can be extremely miniaturized to micron level, and the performance can be optimized through algorithm upgrade (such as deep learning) without hardware modification. The randomness of optical coding can be compensated through calibration, reducing the processing precision requirement, and having high resolution potential.

[0008] With the development of compressed sensing and deep learning technology, reconstruction spectrometer has become a research hotspot due to its performance potential, and is expected to realize high resolution, wide spectral range and ultra-miniaturization. Reconstruction spectrometer is a spectral measurement device based on compressed sensing theory, and its core principle is to sparsely sample the spectral signal through special optical structure, and calculate the complete spectral information by using reconstruction algorithm. Its reconstruction process can be represented by the following equation: wherein, and is the working range of the spectrometer, is the light source spectrum, is the spectral response of the th spectrometer response unit. is the detected light power of the th group. When , , and are known, the spectrum of the light source can be restored by the reconstruction algorithm .

[0009] According to the compression sensing theory, the effect of spectral reconstruction is closely related to the characteristics of the spectral response function of the system. Specifically, the greater the difference between the response functions of each optical response unit in the on-chip spectrometer, that is, the smaller the correlation between the response functions, the more ideal the reconstruction effect. Therefore, designing a response function with high non-correlation is the key to the reconstruction type on-chip spectrometer.

[0010] In order to obtain high resolution, high precision sampling of the original spectral signal is required, which reflects in the response function of the system, that is, a high quality factor optical response function is required. At the same time, in order to obtain a larger working bandwidth, the response function of the system needs to cover a larger range, that is, a large free spectral range optical response function. However, high quality factor and large free spectral range are often mutually balanced, and finally, after obtaining the balance of the above two, the device area of the designed photonic chip needs to be further considered. SUMMARY

[0011] In view of the defects of the prior art, the purpose of the present application is to provide a reconfigurable on-chip spectrometer based on low-loss GST superlattice phase change material, which aims to solve the problem that high quality factor and large free spectral range are often mutually balanced.

[0012] To achieve the above purpose, the present application provides a reconfigurable on-chip spectrometer based on low-loss GST superlattice phase change material, comprising: a resolution control array, a mode field converter and a measurement bandwidth control array.

[0013] The resolution control array comprises a plurality of first MRRs (Microring Resonator, micro ring resonator) arranged at equal intervals along the extension direction of the bus waveguide in cascade, The Q value of the first MRR is not less than 30,000, is not less than 3, the resonant micro ring length of each first MRR increases, and a part of the resonant micro ring of each first MRR away from the coupling region is wrapped by the GST superlattice phase change material, and by changing the phase state of the GST superlattice phase change material, different resolution and different wavelength spectral sampling of the measured spectrum is realized;

[0014] The mode field converter is used to connect the resolution control array and the measurement bandwidth control array.

[0015] The measurement bandwidth control array is formed by cascading a plurality of second MRRs with increasing resonant micro ring lengths, and the second MRR is used for filtering and outputting the spectral signal output by each first MRR.

[0016] The waveguide width of the first MRR is greater than the waveguide width of the second MRR, and the free spectral range FSR of the first MRR satisfies wherein, The average moving range of the resonance peak of the first MRR when the GST superlattice changes from amorphous state to crystalline state.

[0017] Preferably, the GST superlattice phase change material is The layer GST superlattice is stacked by 3nm-thick The layer and 3nm-thick The layer, .

[0018] Preferably, n is 2, and the phase change state of the GST-SL2 superlattice includes amorphous state, crystalline state and at least 4 intermediate states.

[0019] Preferably, the first MRR waveguide is a multi-mode waveguide with a width of , and the second MRR waveguide is a single-mode waveguide with a width of .

[0020] Preferably, the part of the resonant micro-ring wrapped by the GST superlattice phase change material is at least 10μm away from the coupling area.

[0021] Preferably, the first MRR includes a first bus waveguide, a second bus waveguide and a runway-type resonant micro-ring;

[0022] The two ends of the first bus waveguide are respectively provided with an input end and a straight-through end of the optical signal;

[0023] The two ends of the second bus waveguide are respectively provided with an output end and an ADD end of the optical signal;

[0024] A part of the surface of the runway-type resonant micro-ring is integrated with the GST superlattice phase change material;

[0025] The first bus waveguide and the second bus waveguide are arranged in parallel with each other;

[0026] The runway-type resonant micro-ring is arranged between the two bus waveguides and coupled with the two bus waveguides;

[0027] The optical signal enters from the input end of the first bus waveguide, part of the light is transmitted to the straight-through end, and the other part of the light is coupled into the runway-type resonant micro-ring for resonance; the first part of the light in the resonance area is coupled out of the output end of the second bus waveguide, the second part of the light continues to resonate in the resonance area, and the third part of the light is coupled out to the straight-through end of the first bus waveguide, and all the light coupled out of the straight-through end enters the next first MRR.

[0028] Preferably, the first bus waveguide and the second bus waveguide have the same structure and are composed of a straight waveguide and curved waveguides located on both sides of the straight waveguide, and the straight waveguide is arranged on the same side of the straight waveguide of the runway-type resonant micro-ring and has a gap to form a coupling area.

[0029] Preferably, the reconfigurable on-chip spectrometer can obtain group optical power signals, the number of states of the GST superlattice phase transition material, the number of second MRRs in the measurement bandwidth regulation array.

[0030] Preferably, it further comprises:

[0031] A first input grating coupler for inputting a light source for calibrating the resolution regulation array;

[0032] A second input grating coupler for inputting a light source to be measured;

[0033] A third output grating coupler for outputting the light response of the resolution regulation array to a conventional spectrometer when calibrating the resolution regulation array;

[0034] A fourth input grating coupler for inputting a light source for calibrating the measurement bandwidth regulation array;

[0035] A plurality of first output grating couplers for outputting the light response processed by the on-chip spectrometer to a photodetector when measuring the spectrum;

[0036] A plurality of second output grating couplers for outputting the light response of the measurement bandwidth regulation array to a conventional spectrometer when calibrating the measurement bandwidth regulation array;

[0037] A plurality of photodetectors for receiving the light response of the on-chip spectrometer and converting the light signal into an electrical signal;

[0038] A plurality of lasers for outputting laser light to regulate the phase transition state of the GST superlattice phase transition material.

[0039] Preferably, the reconfigurable on-chip spectrometer has a resolution dynamic selection mechanism, when the least squares method is used, the resolution of the spectrometer is greater than 1 nm; when the sequential least squares method is used, the resolution of the spectrometer is less than 10 pm; when the non-negative least squares method is used, the resolution of the spectrometer is in the interval [10 pm, 1 nm].

[0040] Overall, compared with the prior art, the above technical solutions conceived by the present application have the following beneficial effects:

[0041] (1) On the basis of weighing high resolution, large bandwidth and small device area, the application proposes a reconfigurable on-chip spectrometer based on low-loss GST superlattice phase change material. By combining low-loss GST-SL2 material with double-cascade micro-ring array architecture, the performance of the device is breakthroughly improved. The design only needs a limited number of micro-ring resonators on the chip to generate a large number of spectral responses, while supporting flexible control of spectral resolution and working bandwidth, and can meet the customization needs of different application scenarios.

[0042] (2) The application proposes a reconfigurable on-chip spectrometer based on low-loss GST superlattice phase change material, which adopts a resolution control array composed of first MRR cascades arranged at equal intervals along the extension direction of the bus waveguide. The resonant micro-ring length of each first MRR increases. This cascading design significantly enhances the overall control capability through the synergistic effect of multiple MRRs, ensuring that the sampling points can cover the entire working bandwidth of the on-chip spectrometer. The free spectral range FSR of the first MRR satisfies , so as to cover the working bandwidth of the on-chip spectrometer as evenly as possible and ensure the quality of spectral reconstruction.

[0043] (3) The application proposes a reconfigurable on-chip spectrometer based on low-loss GST superlattice phase change material. The measurement bandwidth control array is composed of multiple second MRRs with increasing resonant micro-ring lengths. The working bandwidth is divided into multiple channels and the structure parameters of the MRR are optimized, successfully enhancing the non-correlation of the system response function, providing a reliable foundation for spectral reconstruction. The above structure design enables the GST-SL reconfigurable on-chip spectrometer to flexibly adapt to spectral reconstruction tasks with different resolution requirements by controlling the state of the resolution array, significantly improving the performance of the on-chip spectrometer. BRIEF DESCRIPTION OF DRAWINGS

[0044] Figure 1 is a structure schematic diagram of a reconfigurable on-chip spectrometer based on low-loss GST superlattice phase change material provided by the embodiment of the application.

[0045] Figure 2 is a structure schematic diagram of a GST superlattice phase change material provided by the embodiment of the application.

[0046] Figure 3 is a structure schematic diagram of a high-Q GST-SL2-MRR provided by the embodiment of the application.

[0047] Figure 4 is a spectral response function provided by the embodiment of the application, wherein (a) is the download end spectral response function of the GST-SL2-MRR; and (b) is the spectral response function of the resolution control array under different states.

[0048] Figure 5 This application provides an embodiment of GST-SL. n - Schematic diagram of the optical system for phase transition processing using MRR.

[0049] Figure 6 This is a schematic diagram of the measurement bandwidth control array provided in the embodiments of this application, wherein (a) is a schematic diagram of the unit structure of the measurement bandwidth control array; and (b) is the spectral response of different channels of the measurement bandwidth control array.

[0050] Figure 7 These are comparison diagrams of reconstruction effects provided in the embodiments of this application, wherein (a) is a comparison diagram of single-wavelength spectral reconstruction effects; (b) is a comparison diagram of dual-wavelength spectral reconstruction effects; (c) is a comparison diagram of multi-wavelength spectral reconstruction effects; and (d) is a comparison diagram of broadband spectral reconstruction effects. Detailed Implementation

[0051] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0052] The embodiments of this application are described below with reference to the accompanying drawings.

[0053] like Figure 1 As shown, this application provides a reconfigurable on-chip spectrometer based on low-loss GST superlattice phase change material, including: a resolution control array, a mode field converter, and a measurement bandwidth control array;

[0054] The resolution-tuning array comprises cascaded arrays arranged at equal intervals along the extension direction of the bus waveguide. The first MRR, wherein the Q value of the first MRR is not less than 30,000. The length of the resonant microring of each first MRR is an integer not less than 3. The portion of the resonant microring of each first MRR away from the coupling region is wrapped by GST superlattice phase change material. By changing the phase state of GST superlattice phase change material, spectral sampling of the spectrum to be measured with different resolutions and different wavelengths can be achieved.

[0055] A mode-field converter is used to connect a resolution control array and a measurement bandwidth control array.

[0056] The measurement bandwidth control array is composed of multiple second MRRs with increasing resonant microring lengths cascaded together. The second MRRs are used to filter and output the spectral signals output by each first MRR.

[0057] The width of the first MRR waveguide is greater than the width of the second MRR waveguide, and the free spectral range (FSR) of the first MRR satisfies... wherein, is the average moving range of the first MRR resonance peak when the GST superlattice changes from amorphous state to crystalline state.

[0058] Preferably, as Figure 2 indicated, the GST superlattice phase change material is layer GST superlattice, each layer of GST superlattice is stacked by 3nm-thick layer and 3nm-thick layer, GST-SL n This material structure can effectively reduce the optical loss of GST while almost not affecting the regulation ability of GST material. SL represents the superlattice structure, represents the number of superlattice layers.

[0059] Preferably, The value of 2, the phase change state of GST-SL2 superlattice includes amorphous state, crystalline state and at least 4 intermediate states.

[0060] It should be noted that the GST-SL on-chip spectrometer designed in the present application innovatively uses low-loss GST-SL2 phase change material. Compared with the GST-SL n ( ) material system, this material has more excellent quality factor, significantly improving the performance of the device; at the same time, compared with the traditional GST phase change material, its optical loss is greatly reduced, and it is more suitable for high-precision spectral detection applications.

[0061] Preferably, the first MRR waveguide adopts a multimode waveguide with a width of , and the second MRR waveguide adopts a single-mode waveguide with a width of .

[0062] Preferably, the part of the resonant micro-ring wrapped by the GST superlattice phase change material is at least 10μm away from the coupling area.

[0063] Preferably, the first MRR includes a first bus waveguide, a second bus waveguide and a runway-type resonant micro-ring;

[0064] The two ends of the first bus waveguide are respectively provided with an input end and a straight-through end of the optical signal;

[0065] The two ends of the second bus waveguide are respectively provided with an output end and an ADD end of the optical signal;

[0066] A part of the surface of the runway-type resonant micro-ring is integrated with GST superlattice phase change material;

[0067] The first bus waveguide and the second bus waveguide are arranged in parallel to each other;

[0068] The two bus waveguides are provided with a runway-type resonant micro-ring and are coupled with the two bus waveguides;

[0069] The optical signal enters from the input end of the first bus waveguide, part of the light is transmitted to the through end, and the other part of the light is coupled into the runway-type resonant micro-ring for resonance; the first part of the light in the resonant region is coupled out of the output end of the second bus waveguide for output, the second part of the light continues to resonate in the resonant region, and the third part of the light is coupled out to the through end of the first bus waveguide, and all the light coupled out of the through end enters the next first MRR.

[0070] Preferably, the first bus waveguide and the second bus waveguide have the same structure, which is composed of a straight waveguide and curved waveguides located on both sides of the straight waveguide, and the straight waveguide is arranged on the same side of the straight waveguide of the runway-type resonant micro-ring and has a gap to form a coupling region.

[0071] Preferably, the reconfigurable on-chip optical spectrometer can obtain a group of optical power signals, a number of states of the GST superlattice phase change material, a number of the second MRRs in the measurement bandwidth control array.

[0072] Preferably, it further comprises:

[0073] a first input grating coupler for inputting a light source for calibrating the resolution control array;

[0074] a second input grating coupler for inputting a light source to be measured;

[0075] a third output grating coupler for outputting the light response of the resolution control array to a conventional optical spectrometer when calibrating the resolution control array;

[0076] a fourth input grating coupler for inputting a light source for calibrating the measurement bandwidth control array;

[0077] a plurality of first output grating couplers for outputting the light response processed by the on-chip optical spectrometer to a photodetector when measuring the spectrum;

[0078] a plurality of second output grating couplers for outputting the light response of the measurement bandwidth control array to a conventional optical spectrometer when calibrating the measurement bandwidth control array;

[0079] a plurality of photodetectors for receiving the light response of the on-chip optical spectrometer and converting the light signal into an electrical signal;

[0080] Multiple lasers It is used to output laser light and control the phase transition state of GST-SL2.

[0081] Preferably, the reconfigurable on-chip spectrometer has a dynamic resolution selection mechanism. When the least squares method is used, the spectrometer resolution is greater than 1 nm; when the sequential least squares method is used, the spectrometer resolution is less than 10 pm; and when the non-negative least squares method is used, the spectrometer resolution is in the range of [10 pm, 1 nm].

[0082] Least squares is suitable for reconstructing low-resolution spectral signals, but its reconstruction effect is poor at high resolutions. Non-negative least squares has a more reasonable physical meaning (non-negative spectral intensity), and its reconstruction quality is better than ordinary least squares, with moderate speed. However, it still cannot handle complex constraints (such as smoothness and sparsity) and may underfit high-resolution signals. Sequential least squares is suitable for medium-resolution requirements, balancing reconstruction speed and accuracy. Sequential least squares supports complex constraints and regularization, has the highest reconstruction accuracy at high resolutions, and can effectively suppress noise, but its computational complexity is high, it relies on iterative convergence, and its speed is significantly slower than the former two methods.

[0083] This application intelligently selects the reconstruction algorithm based on the user-input resolution, achieving a balance between reconstruction speed and quality. The specific strategy is as follows: For low resolution, the least squares method (Lstsq) is prioritized for rapid reconstruction, meeting real-time requirements. For medium resolution, the non-negative least squares method (NNLS) is employed to ensure both reconstruction quality and computational efficiency. For high resolution, the sequential least squares method (SLSQP) is used to ensure reconstruction accuracy, and a regularization term is introduced to suppress noise and overfitting. Through this dynamic selection mechanism, the algorithm proposed in this application can adapt to the needs of different application scenarios, optimizing computational efficiency while ensuring reconstruction accuracy, providing strong support for the practical application of the GST-SL reconfigurable on-chip spectrometer.

[0084] Example

[0085] In this embodiment, the resolution control array is composed of 3 cascaded GST-SL2-MRRs (micro-ring resonators integrating GST-SL2), and the measurement bandwidth control array is composed of 9 MRRs (silicon micro-ring resonators).

[0086] The following is a detailed description of the resolution control array in this embodiment.

[0087] The resolution control array (MRR) is one of the core components of an on-chip spectrometer, and its main function is to finely sample the raw spectral signal according to resolution requirements. Therefore, a download-side spectral response function with an extremely high Q value is required for the MRR to achieve this fine sampling. Furthermore, to ensure that the sampling points uniformly cover the entire operating bandwidth of the on-chip spectrometer, the MRR needs to have the largest possible controllability, i.e., the ability to generate the largest possible phase shift. Therefore, the on-chip spectrometer places a dual requirement on the design of the GST-SL-MRR: a high Q value and a large phase shift.

[0088] There is a trade-off between the tuning range and optical loss of GST-SL. To prioritize resolution performance, this embodiment preferentially uses GST-SL2 as the phase transition material and designs a GST-SL2-MRR. The GST-SL2 phase transition not only causes a rightward shift of the center wavelength of the resonance peak but also reduces the Q value, effectively lowering the sampling resolution.

[0089] like Figure 3 As shown, a complete GST-SL2-MRR is formed by the central resonant region (the closed ring in the figure) and the coupling regions on both sides, wherein part of the waveguide in the resonant region covers the GST-SL2. This embodiment uses a multimode waveguide and an Euler bending structure to reduce overall loss and improve Q value.

[0090] like Figure 3 As shown, the light source enters from the Input end. Part of the light is transmitted to the Through end for direct output, and part of the light is coupled into the resonant region for resonance. Part of the light from the resonant region is coupled out to the Drop end for output, while part of the light continues to resonate in the resonant region, and part of the light is coupled out to the Through end. This is a continuously cyclical process until the light intensity decays to zero. Ultimately, the spectral response output at each end is the overall result of the entire resonant process.

[0091] like Figure 3 As shown, the specific parameters of GST-SL2-MRR include: coupling length The length of GST-SL2 is 50 μm, the coupling distance is 100 nm, and the length of GST-SL2 is... It is 9 μm.

[0092] Because the control capability of a single GST-SL2-MRR is limited and cannot uniformly cover the entire operating bandwidth of the on-chip spectrometer, this embodiment uses three GST-SL2-MRRs cascaded together to form a resolution control array. The runway length of each GST-SL2-MRR for μm. This cascaded design significantly enhances the overall controllability through the synergistic effect of multiple MRRs, ensuring that sampling points can uniformly cover the entire working bandwidth.

[0093] The download-side spectral response of the first GST-SL2-MRR is as follows: Figure 4 As shown in (a), state 1 represents GST-SL2 in an amorphous state, state 6 represents GST-SL2 in a crystalline state, and the remaining states represent intermediate states. As GST-SL2 transitions from an amorphous to a crystalline state, the resonant center wavelength of the GST-SL2-MRR gradually redshifts, while the Q value gradually decreases. This dynamic change provides flexibility and diversity for spectral sampling. Furthermore, each GST-SL2-MRR in the resolution-tuning array can be independently state-tuned.

[0094] This embodiment establishes an optical system for monitoring GST-SL. n -MRR (taking n=2 as an example) is subjected to phase transition treatment and its response spectrum is measured. The optical system design is as follows: Figure 5 As shown, the specific composition and working principle are as follows: A 1064 nm pulsed laser serves as the light source for phase transition processing (1064 nm Laser). This 1064 nm pulsed laser passes through two beam splitters (BS) before entering the beam shaper. The beam shaper transforms the Gaussian distribution of light intensity into a flat-top distribution, making the laser intensity incident on the GST-SL2 through the objective lens more uniform, thus ensuring the uniformity of the phase transition processing. A 632 nm laser serves as the monitoring light source, used to monitor the phase transition state of the GST-SL2 in real time. When the GST-SL2 undergoes a phase transition, the intensity of the light reflected into the photodetector (PD) changes due to the change in refractive index. By monitoring the changes in the PD signal, it can be determined whether the phase state of the GST-SL2 has changed. The objective lens is used to focus a 1064 nm pulsed laser onto the GST-SL2. Simultaneously, a white light source is tilted to illuminate the GST-SL2-MRR, and a camera is placed on the opposite side to observe whether the laser focus is on the GST-SL2, ensuring that the laser energy is concentrated in the target area. The spectrometer module is used to measure the response spectrum of the GST-SL2-MRR to verify its optical performance.

[0095] Figure 4Figure (b) illustrates the spectral response of the resolution-tuning array in two states: state 661 means the first two GST-SL2-MRRs are in state 6, and the last GST-SL2-MRR is in state 1; state 666 indicates that all GST-SL2-MRRs are in state 6. This encoding-like approach allows for various forms of data sampling of the original spectrum using only three GST-SL2-MRRs, significantly improving the system's flexibility and adaptability.

[0096] The following is a detailed description of the measurement bandwidth control array in this embodiment.

[0097] The measurement bandwidth control array consists of nine cascaded MRRs. Since the on-chip spectrometer in this embodiment is designed with a working bandwidth of 20 nm (1540 nm to 1560 nm), the bandwidth of each channel is approximately... 2.22 nm, meaning that the required FWHM (full width at half maximum) of each MRR is approximately 2.22 nm, and its FSR (free spectral range) is approximately 20 nm. This design allows the measurement bandwidth modulation array to uniformly divide the working bandwidth into 9 channels while suppressing resonance peaks outside the channels, thereby significantly improving the uncorrelation of the system response function.

[0098] Since MRRs with an FSR of 20 nm typically require extremely small bending radii, they are prone to significant bending losses. This embodiment employs a 420 nm wide silicon-based waveguide. This design better tolerates small bending radii and reduces losses. Specific parameters for each MRR are as follows: Figure 6 As shown in (a), its bending radius The length is 4.5 μm, the coupling spacing is 150 nm, and the runway length of each MRR is slightly different to produce different center resonant wavelengths. The runway length of each MRR for This design allows the center resonant wavelength of each MRR to be uniformly and gradually redshifted, thus covering the entire operating bandwidth. The spectral response of the measurement bandwidth modulation array was obtained by simulating it using INTERCONNECT software, as shown below. Figure 6 As shown in Figure (b), C1 to C9 represent filter channels 1 to 9, respectively. It can be observed that the resonant center wavelength gradually redshifts uniformly, relatively uniformly covering the operating bandwidth of the on-chip spectrometer in this embodiment. This uniform channel division and center wavelength distribution significantly enhances the non-correlation of the system's spectral response function, laying a good foundation for subsequent spectral reconstruction.

[0099] The three GST-SL2-MRRs of the resolution tuning array achieve the tuning of spectral resolution by changing the state of GST-SL2. For example, when the GST-SL2 of GST-SL2-MRR1 is in the amorphous state, the GST-SL2 of GST-SL2-MRR2 and GST-SL2-MRR3 can be in the crystalline state. If each GST-SL2 is divided into 6 states, the resolution tuning array can obtain a total of 6 3 = 216 state combinations. Such multi-state combinations enable the resolution tuning array to cover a wide range of spectral resolution.

[0100] After the spectral signal passes through the resolution tuning array, it enters the measurement bandwidth tuning array through the mode field converter. The measurement bandwidth tuning array is composed of 9 MRRs, each of which filters the spectral signal, and finally measures 9 groups of optical power signals at the to ports. Therefore, the GST-SL n reconfigurable on-chip spectrometer can obtain 9 groups of optical power signals through one reconfiguration, and these signals are used to recover the original spectral information through a reconstruction algorithm.

[0101] In addition, in order to facilitate the actual manufacturing and calibration process of the later device, the GST-SL n reconfigurable on-chip spectrometer also designs additional calibration ports for separately calibrating the resolution tuning array and the measurement bandwidth tuning array. When the light source is input from the port, the spectral response of the resolution tuning array can be measured at the port. This design can separately evaluate the performance of the resolution tuning array without involving the measurement bandwidth tuning array. When the light source is input from the port, the spectral response of each MRR in the measurement bandwidth tuning array can be measured at the to port. In this way, the filtering characteristics of each MRR can be calibrated to ensure the stability and consistency of the measurement bandwidth tuning array.

[0102] The dynamic spectral reconstruction algorithm is used to perform spectral reconstruction tests on the simulation data, and the performance of the reconfigurable on-chip spectrometer based on the low-loss GST superlattice phase change material is verified. The spectral reconstruction test results are shown in Figure 7 , and the specific analysis is as follows:

[0103] (1) Single-wavelength spectral reconstruction

[0104] In the Figure 7 ​In (a), the original spectrum is a single-wavelength spectrum with a full width at half maximum (FWHM) of 0.05 nm. After processing by the dynamic spectral reconstruction algorithm, the reconstructed spectrum matches the original spectrum very well. This result demonstrates that the GST-SL of this application... n Reconfigurable on-chip spectrometers offer extremely high precision and stability in single-wavelength spectral detection, enabling accurate reconstruction of spectral signal characteristics.

[0105] (2) Dual-wavelength spectral reconstruction

[0106] exist Figure 7 In (b), the original spectrum is composed of two sets of spectra with an FWHM of 2 pm and a center wavelength interval of 5 pm. After processing by the reconstruction algorithm, although the reconstructed spectrum shows slight deviations in the degree of agreement with the original spectrum at some wavelength points, it still successfully resolves the two sets of extremely close center wavelengths. This result proves that the GST-SL of this application... n The reconfigurable on-chip spectrometer achieves a maximum resolution of 5 pm, demonstrating its outstanding performance in ultra-high resolution spectral detection.

[0107] (3) Multiwavelength spectral reconstruction

[0108] exist Figure 7 In (c), the original spectrum is composed of six sets of spectra with a center wavelength interval of 1 nm and an FWHM of 0.1 nm superimposed. The reconstruction algorithm successfully reconstructed this complex spectral signal with good overall consistency. However, some differences in the peak values ​​of each set of spectra can be observed, mainly due to... This is due to the limited number of [items / resources] and the insufficient accuracy of the reconstruction algorithm. Nevertheless, this result still demonstrates the superiority of the GST-SL [technology / method / engineering] proposed in this application. n Reconfigurable on-chip spectrometers can effectively process multi-wavelength spectral signals, providing reliable support for complex spectral analysis.

[0109] (4) Broadband spectral reconstruction

[0110] exist Figure 7 In (d), the original spectrum is a broadband spectral signal. After processing by the reconstruction algorithm, the reconstructed spectrum highly overlaps with the original spectrum, demonstrating the GST-SL of this application. n The reconfigurable on-chip spectrometer demonstrates excellent performance in broadband spectral detection. This result shows that the spectrometer is not only suitable for narrowband spectral analysis, but also capable of efficiently processing broadband spectral signals, further expanding its application range.

[0111] Overall, the GST-SL proposed in this application nThe reconfigurable on-chip spectrometer performs well in the reconstruction test of four different spectral signals, especially under ideal light source conditions, the reconstructed spectrum is in good agreement with the original spectrum. It is worth noting that the ultimate resolution of this spectrometer can reach 5 pm, which highlights its high performance in ultra-high resolution spectral detection. In addition, the successful application of its dynamic spectral reconstruction algorithm further verifies the reliability and flexibility of the spectrometer in complex spectral signal processing.

[0112] In order to comprehensively measure the GST-SL n based reconfigurable on-chip spectrometer proposed in this application, its key performance is compared with typical on-chip spectrometers reported in recent years in Table 1. Through comparison, it can be found that it is still a major challenge in current on-chip spectrometer design to simultaneously achieve ultra-high resolution and large bandwidth on a device area less than 0.5 mm 2 The following is a specific analysis of the comparison results.

[0113] The ratio of the working bandwidth to the resolution of the on-chip spectrometer is one of the important indicators to measure the performance of the spectrometer, which directly reflects the comprehensive ability of the spectrometer in complex spectral signal detection and analysis. From the comparison analysis in Table 1, it can be seen that the GST-SL n based reconfigurable on-chip spectrometer proposed in this application is at an excellent level in this indicator. Although the on-chip spectrometers reported in Table 1 have achieved an ultra-high resolution of 0.001 nm and a ratio of working bandwidth to resolution of 12000, their device area is as high as 13.87 mm 2 , which greatly limits their practicality in miniaturized application scenarios. In contrast, the GST-SL n based reconfigurable on-chip spectrometer proposed in this application achieves a wavelength resolution of 5 pm within a device area of only 0.3 mm 2 , while maintaining a working bandwidth of 20 nm, with a bandwidth-to-resolution ratio of up to 4000, which is about 40% of the performance of the on-chip spectrometer with less than 3% of its device area. Not only does it achieve an excellent balance between miniaturization and high performance, but it also sets a new record for all-optical on-chip spectrometers with a device area less than 0.5 mm 2 .

[0114] It is worth noting that the on-chip spectrometer design architecture proposed in this application has very high flexibility, which can be adjusted in structure parameters according to actual application requirements. For example, it can further enhance the performance by sacrificing part of the area, or increase the working bandwidth by sacrificing part of the resolution. This design flexibility enables it to adapt to the needs of different application scenarios, making it possible to develop customized spectral analysis equipment.

[0115] Table 1 Comparison of key performance with typical spectrometers

[0116]

[0117] The simulation results show that the on-chip spectrometer designed in the application achieves excellent performance on an ultra-compact chip area (0.3 mm 2 ) with a working bandwidth of 20 nm and a wavelength resolution of up to 5 pm, and the ratio of the working bandwidth to the resolution breaks through 4000. This performance index breaks the record of the all-optical reconfigurable on-chip spectrometer with a device area less than 0.5 mm 2 . It shows excellent performance in the field of miniaturized spectral analysis. In addition, the design of the spectrometer is fully compatible with the standard CMOS manufacturing process, which enables it to be easily integrated with a silicon-germanium photodetector on the same chip to build a complete optoelectronic system. This feature not only reduces the manufacturing complexity, but also provides the possibility for large-scale integration and commercial application.

[0118] It should be understood that expressions such as "include" and "may include" used in the present application indicate the presence of the disclosed functions, operations or constituent elements, and do not limit one or more additional functions, operations and constituent elements. In the present application, terms such as "include" and / or "have" can be interpreted to mean that a specific feature, number, operation, constituent element, component or combination thereof is present, but cannot be interpreted to exclude the presence or addition of one or more other features, numbers, operations, constituent elements, components or combinations thereof.

[0119] In addition, in the present application, the expression "and / or" includes any and all combinations of the associated listed terms. For example, the expression "A and / or B" can include A, can include B, or can include both A and B.

[0120] In the description of the embodiments of the present application, it should be noted that, unless otherwise explicitly specified and limited, the term "connection" should be understood broadly, for example, "connection" can be detachable connection, or can be non-detachable connection; can be direct connection, or can be indirect connection through an intermediate medium. Among them, "fixed connection" means that the relative positional relationship after connection is unchanged. "Rotary connection" means that the relative rotation after connection is connected. "Sliding connection" means that the relative sliding after connection is connected. The orientation language mentioned in the embodiments of the present application, such as "top", "bottom", "inner", "outer", "left", "right", etc., is only the direction of the drawing, therefore, the orientation language used is to better, more clearly illustrate and understand the embodiments of the present application, and is not indicative or implied that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, therefore, it cannot be understood as a limitation on the embodiments of the present application.

[0121] In addition, in the embodiments of the present application, the mathematical concepts of symmetry, equality, parallel, perpendicular, etc. are mentioned. These limitations are for the current process level, not the absolute strict definition in the mathematical sense, and a small amount of deviation is allowed, such as approximately symmetrical, approximately equal, approximately parallel, approximately perpendicular, etc. For example, A is parallel to B, which means that A and B are parallel or approximately parallel, and the included angle between A and B can be between 0 degrees and 10 degrees. A is perpendicular to B, which means that A and B are perpendicular or approximately perpendicular, and the included angle between A and B can be between 80 degrees and 100 degrees.

[0122] The above is only a specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed in the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A reconfigurable on-chip spectrometer based on low-loss GST superlattice phase transition material, characterized in that, include: Resolution control array, mode field converter, and measurement bandwidth control array; The resolution-tuning array comprises cascaded arrays arranged at equal intervals along the extension direction of the bus waveguide. The first MRR, wherein the Q value of the first MRR is not less than 30,000. The length of the resonant microring of each first MRR is an integer not less than 3. The portion of the resonant microring of each first MRR away from the coupling region is wrapped by GST superlattice phase change material. By changing the phase state of GST superlattice phase change material, spectral sampling of the spectrum to be measured with different resolutions and different wavelengths can be achieved. A mode-field converter is used to connect a resolution control array and a measurement bandwidth control array. The measurement bandwidth control array is composed of multiple second MRRs with increasing resonant microring lengths cascaded together. The second MRRs are used to filter and output the spectral signals output by each first MRR. The width of the first MRR waveguide is greater than the width of the second MRR waveguide, and the free spectral range (FSR) of the first MRR satisfies... ,in, The average shift range of the resonance peak of the first MRR when the GST superlattice changes from an amorphous state to a crystalline state.

2. The reconfigurable on-chip spectrometer as described in claim 1, characterized in that, GST superlattice phase change material is Layered GST superlattices, each layer of the GST superlattice is 3 nm thick Layer and 3nm thick It is made of stacked layers. .

3. The reconfigurable on-chip spectrometer as described in claim 2, characterized in that, With a value of 2, the phase transition states of the GST-SL2 superlattice include amorphous, crystalline, and at least four intermediate states.

4. The reconfigurable on-chip spectrometer as described in claim 1, characterized in that, The first MRR waveguide has a width of The multimode waveguide, the second MRR waveguide adopts a width of Single-mode waveguide.

5. The reconfigurable on-chip spectrometer as described in claim 1, characterized in that, The resonant microring is partially encased in a distance coupling region of at least 10 μm by the GST superlattice phase change material.

6. The reconfigurable on-chip spectrometer as described in claim 1, characterized in that, The first MRR includes a first bus waveguide, a second bus waveguide, and a racetrack-shaped resonant microring; The first bus waveguide has an optical signal input terminal and a through terminal at its two ends, respectively; The second bus waveguide has an optical signal output terminal and an ADD terminal at its two ends, respectively; A portion of the surface of the racetrack-shaped resonant microring is integrated with GST superlattice phase change material. The first bus waveguide and the second bus waveguide are arranged parallel to each other; A racetrack-shaped resonant microring is provided between the two bus waveguides and coupled to the two bus waveguides; The optical signal enters from the input end of the first bus waveguide. Part of the light is transmitted to the through end, and the other part of the light is coupled into the racetrack-shaped resonant microring. The first part of the light in the resonant region is coupled out from the output end of the second bus waveguide. The second part of the light continues to resonate in the resonant region. The third part of the light is coupled out to the through end of the first bus waveguide. All the light coupled out from the through end enters the next first MRR.

7. The reconfigurable on-chip spectrometer as described in claim 6, characterized in that, The first bus waveguide and the second bus waveguide have the same structure, consisting of a straight waveguide and curved waveguides located on both sides of the straight waveguide. The straight waveguide is arranged on the same side as the straight waveguide of the racetrack-shaped resonant microring and there is a gap to form a coupling region.

8. The reconfigurable on-chip spectrometer as described in claim 1, characterized in that, A reconfigurable on-chip spectrometer can obtain [data / improvements] in one reconstruction. Group optical power signal, For the GST superlattice phase transition material, (This refers to the state number.) To measure the number of second MRRs in the bandwidth control array.

9. The reconfigurable on-chip spectrometer according to any one of claims 1 to 8, characterized in that, Also includes: The first input grating coupler is used to input the light source when calibrating the resolution control array; The second input grating coupler is used to input the light source to be tested. The third output grating coupler is used to output the light response of the resolution control array to a conventional spectrometer when calibrating the resolution control array. The fourth input grating coupler is used to input the light source when calibrating the measurement bandwidth control array; Multiple first output grating couplers are used to output the light response processed by the on-chip spectrometer to the photodetector when measuring the spectrum; Multiple second output grating couplers are used to output the light response of the measurement bandwidth control array to a conventional spectrometer when calibrating the measurement bandwidth control array; Multiple photodetectors are used to receive the light response of the on-chip spectrometer and convert the light signal into an electrical signal; Multiple lasers are used to output laser light to control the phase transition state of GST superlattice phase transition materials.

10. The reconfigurable on-chip spectrometer as described in claim 9, characterized in that, The reconfigurable on-chip spectrometer has a dynamic resolution selection mechanism. When the least squares method is used, the spectrometer resolution is greater than 1 nm; when the sequential least squares method is used, the spectrometer resolution is less than 10 pm; when the non-negative least squares method is used, the spectrometer resolution is in the range of [10 pm, 1 nm].

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