A fast demodulation system and method for large-scale microcavity array on chip

Abstract

The application relates to a fast demodulation system and method for a large-scale microcavity array on a chip, and the system comprises a frequency-sweeping laser, a first fiber coupler, a microcavity array transmission signal arm, an auxiliary interference reference arm, a same-frequency trigger arm and a signal processing device. The first fiber coupler is used for dividing a light source into a first light source and a second light source. The microcavity array transmission signal arm is used for receiving the first light source of the frequency-sweeping laser, and the first light source enters a large-array microcavity sensor device after polarization processing, and is converted into an electric signal after receiving the disturbance of an external sensing signal. The auxiliary interference reference arm is used for receiving the second light source of the frequency-sweeping laser, and two beams of coherent light with opposite phases are obtained after processing the second light source, and then the coherent light is converted into an electric signal. The same-frequency trigger arm is used for transmitting a same-frequency trigger signal emitted by the frequency-sweeping laser. The signal processing device is used for signal acquisition and processing. The application effectively suppresses the frequency-axis distortion and spectral line broadening caused by the frequency-sweeping nonlinearity of the laser, and can be applied to the accurate demodulation of a large-scale, high-Q microcavity sensing array.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of integrated photonics, and more particularly, to a fast demodulation system and method for a large-scale microcavity array on a chip. BACKGROUND

[0002] In recent years, with the rapid development of on-chip optical technology, light source technology and optical information processing, emerging optical sensors have attracted widespread attention and application due to their high sensitivity, anti-electromagnetic interference and other advantages. In particular, sensors based on on-chip optical microcavities concentrate light field energy in a very small area, achieve ultra-high measurement accuracy by high-Q optical resonance, and can achieve unprecedented sensitivity, which is a unit device with potential for large-scale parallel sensing.

[0003] The current sensing architecture of integrated optical microcavity sensing array can be divided into mechanical type, light splitting type and wavelength division multiplexing type. Among them, the integrated optical sensing architecture based on on-chip wavelength division multiplexing can realize multi-channel parallel sensing, and through wavelength calibration of the corresponding sensing unit signal, the quality of the sensing signal is ensured, and the use of multiple reading devices is avoided. This scheme has advantages in the number of channels, reading signal quality and packaging difficulty. There are two common demodulation schemes, one is to use a narrow linewidth tunable laser combined with a photodetector, which can achieve high-precision sensing, but the ordinary tunable laser has limited sweep speed, can only demodulate slow-changing applications, and the application scenarios are limited. At the same time, the integration of tunable lasers with a wide tuning range and high output power is difficult, and there are still many difficulties in realizing a small system. The other scheme is to use a wide-spectrum light source with a large spectral range combined with a spectrometer. Compared with the wide-spectrum light source, the processing difficulty is lower, but the high-throughput and high-precision sensing array requires a large bandwidth and a high-resolution spectrometer to analyze the output spectrum of the sensing array, which puts higher requirements on the performance of the spectrometer. And the scanning speed of the spectrometer is limited, and it can only be used for slow-changing applications.

[0004] For a large number of microcavity arrays, especially for fast-changing sensing applications, there is still a lack of effective parallel demodulation methods. In recent years, some scholars have proposed optical frequency comb and other methods for parallel demodulation of microcavity arrays, but the limited bandwidth limits the number of demodulations, and the system is relatively complex. Therefore, the research on fast demodulation and recognition systems for large array microcavities is still in the blank field. SUMMARY

[0005] The purpose of the present application is to overcome the deficiencies of the prior art in fast parallel demodulation of large-scale on-chip optical microcavity arrays, such as limited number of demodulations and complex system, and to provide a fast demodulation system and method for a large-scale microcavity array on a chip, which can realize fast parallel demodulation of a large-scale microcavity sensing array, and also reduce the complexity of the system.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is:

[0007] A fast demodulation system for a large-scale microcavity array on a chip is provided, comprising:

[0008] A swept laser;

[0009] A first fiber coupler: for receiving the light source of the swept laser, and dividing the light source into a first light source and a second light source;

[0010] A microcavity array transmission signal arm: for receiving the first light source of the swept laser, and after polarization processing the first light source, the first light source enters a large-scale microcavity sensor device on a chip, receives the disturbance of the external sensing signal, and is converted into an electrical signal to obtain a microcavity array transmission spectrum signal;

[0011] An auxiliary interference reference arm: for receiving the second light source of the swept laser, and after processing the second light source, two coherent lights with opposite phases are obtained, and then the coherent lights are converted into an electrical signal to obtain an auxiliary interference reference signal;

[0012] A same-frequency trigger arm: for transmitting the same-frequency trigger signal emitted by the swept laser;

[0013] A signal processing device: for collecting the microcavity array transmission spectrum signal, the auxiliary interference reference signal, and the same-frequency trigger signal, and after signal processing, obtaining a demodulated sensing signal.

[0014] The fast demodulation system for a large-scale microcavity array on a chip of the present application utilizes a fast swept laser with a large bandwidth and a high swept frequency rate to cooperate with a photoelectric detector to collect the entire spectrum of the microcavity array for demodulation of the sensing signal, and at the same time, with the help of an auxiliary interference reference arm, the error caused by the swept frequency nonlinearity of the swept laser is compensated, the frequency axis distortion and spectral line broadening caused by the swept frequency nonlinearity of the laser are effectively suppressed, and the fast demodulation system can be applied to accurate demodulation of a large-scale, high-Q microcavity sensing array, solves the pain points of a small number of traditional micro-ring sensing array demodulation and a complex demodulation method, realizes fast and parallel demodulation of a large-scale microcavity sensing array, and reduces the system complexity.

[0015] In the present application, a fast sweep laser is used as the core device of the overall demodulation system, and the sweep bandwidth determines the number of microcavities that can be covered, and the sweep rate determines the sensing applications that can be demodulated. When the system is used to realize the parallel demodulation of the on-chip microcavity array device, the sensing signal is contained in the demodulated transmission spectrum signal, for example, by tracking the drift of the microcavity resonance peak in each frame of transmission spectrum signal, thereby calibrating the external sensing signal causing the change. Exemplarily, the continuous sweep range of the fast sweep laser reaches 500 GHz, which can cover more than 100 microcavities; when the sweep rate of the fast sweep laser reaches hundreds of hertz or thousands of hertz, low-frequency vibration or stress sensing, such as pulse sensing, can be demodulated; when the sweep rate reaches megahertz, high-frequency ultrasonic sensing, photoacoustic imaging, and other applications can be demodulated.

[0016] Further, the microcavity array transmission signal arm comprises a first polarization controller, an on-chip large array microcavity sensor device, and a first photodetector connected in sequence; the input end of the first polarization controller is connected with the first output end of the first optical fiber coupler; and the output end of the first photodetector is connected with a signal processing device. The sweep light source entering the cavity array transmission signal arm, i.e. the first light source, first passes through the first polarization controller, is processed by polarization, and then enters the on-chip large array microcavity sensor device. At this time, after receiving the disturbance of the external sensing signal, it enters the first photodetector to be converted into an electrical signal, i.e. an auxiliary interference reference signal, and finally enters the signal processing device. The signal processing device performs data acquisition and processing on the auxiliary interference reference signal.

[0017] Further, the auxiliary interference reference arm comprises a second fiber coupler, a fiber delay line, a second polarization controller, a third fiber coupler and a second photodetector; the input end of the second fiber coupler is connected with the second output end of the first fiber coupler, the first output end of the second fiber coupler is connected with the first input end of the third fiber coupler, the second output end of the second fiber coupler is connected with the input end of the second polarization controller through the fiber delay line, the output end of the second polarization controller is connected with the second input end of the third fiber coupler, the output end of the third fiber coupler is connected with the input end of the second photodetector, and the output end of the second photodetector is connected with the signal processing device. The swept light source, i.e. the second light source, entering the auxiliary interference reference arm first enters the second fiber coupler, and the second fiber coupler divides the second light source into two light sources entering the upper and lower arms, respectively. The light source of the upper arm directly enters the third fiber coupler, and the light source of the lower arm enters the third fiber coupler after passing through the fiber delay line and the second polarization controller in sequence. In the third fiber coupler, the light of the upper and lower arms interferes to obtain two coherent lights with opposite phases, and the coherent light enters the second photodetector to be converted into an electrical signal, i.e. an auxiliary interference reference signal. Similarly, the auxiliary interference reference signal enters the signal processing device for data acquisition and processing.

[0018] Further, the length of the fiber delay line is usually greater than the length of the device to be measured, because the auxiliary interference reference signal needs to cover the entire signal frequency range of the device to be measured. In the present application, the on-chip large array microcavity sensor device usually has a short length, and a 10m fiber delay line can be used. In actual application, other lengths can also be used.

[0019] Further, the microcavity array transmission signal arm further comprises an adjustable optical attenuator, and the first output end of the first fiber coupler is connected with the first polarization controller through the adjustable optical attenuator. The adjustable optical attenuator is located before the on-chip first polarization controller, the first light source first enters the adjustable optical attenuator, and then enters the on-chip large array microcavity sensor device through the first polarization controller, which is used to adjust the optical power entering the on-chip large array microcavity sensor device, so as to avoid that the light intensity entering the on-chip large array microcavity sensor device is too large and causes the device to be detuned. In actual application, according to the output optical power of the aforementioned fast swept laser and the different splitting ratios of the first fiber coupler, the adjustable optical attenuator can also be omitted.

[0020] Further, the first fiber coupler divides the light source into a first light source and a second light source according to a splitting ratio of N1:N2, and the value of N1 is greater than the value of N2. The splitting ratio of the first fiber coupler is 9:1, wherein 90% of the light, that is, most of the light, enters the microcavity array transmission signal arm, which takes into account the relatively large device loss that may be introduced by the subsequent on-chip large array microcavity sensor device. And 10% of the light enters the auxiliary interference reference arm through the second fiber coupler, which has very small loss and requires less light intensity. In actual application, according to the different losses of the microcavity array transmission signal arm and the auxiliary interference reference arm, other splitting ratio fiber couplers can also be selected, such as 8:2, 99:1, etc.

[0021] Further, the second fiber coupler divides the second light source into a third light source and a fourth light source according to a splitting ratio of 1:1.

[0022] Further, the microcavity structure of the on-chip large array microcavity sensor device includes a microring resonant cavity, a Fabry-Perot resonant cavity, or a photonic crystal resonant cavity; and is prepared from a chalcogenide material. The microcavity structure of the on-chip large array microcavity sensor device can be a microring resonant cavity, a Fabry-Perot resonant cavity, a photonic crystal microcavity, etc. In the present application, a chalcogenide material is used to prepare an array microcavity device containing 100 microring resonant cavities. The preparation process of the on-chip large array microcavity sensor device includes: preparing a high-quality chalcogenide thin film on a silicon dioxide substrate by a vacuum thermal evaporation method, spin-coating an electron beam exposure glue, and etching a microcavity array structure by an electron beam lithography method, and then treating by a reactive ion beam etching process after development.

[0023] Further, the first photodetector is an avalanche photodetector, and the second photodetector is a balanced photodetector. The avalanche photodetector uses avalanche multiplication effect to amplify the photo-generated carriers twice inside the device, and has high gain. Since the microcavity array has large device loss, it will cause a significant drop in optical power, so the avalanche photodetector is suitable for detecting weak optical signals after passing through the microcavity array. In actual use, when there is no avalanche photodetector, a common photodetector such as a PIN diode can also be used for detection, but an additional amplifier such as an erbium-doped fiber amplifier needs to be introduced in the front end to further amplify the optical signal, and additional spontaneous emission noise may be introduced.

[0024] Further, the sweep laser, the first fiber coupler, the second fiber coupler, the fiber delay line, the second polarization controller, the third fiber coupler, the second photodetector, the first photodetector, the large array of microcavity sensor on chip and the first photodetector are connected through optical fibers; the sweep laser, the first photodetector and the second photodetector are connected with the signal processing device through cables; and the large array of microcavity sensor on chip is connected with the optical fiber through fiber end face coupling or grating vertical coupling.

[0025] The application further provides a fast demodulation method for a large array of microcavities on chip, which adopts the fast demodulation system for a large array of microcavities on chip and comprises the following steps:

[0026] S1. At the signal processing device, the microcavity array transmission spectrum signal, the auxiliary interference reference signal and the same-frequency trigger signal are acquired respectively;

[0027] S2. The signals are aligned through cross-correlation operation, the time delay difference of the microcavity array transmission spectrum signal, the auxiliary interference reference signal and the same-frequency trigger signal is subtracted, and filtering and denoising processing is performed;

[0028] S3. According to the rising edge of the sweep laser same-frequency trigger signal, the microcavity array transmission spectrum signal and the auxiliary interference reference signal are data-synchronized and sliced, and are divided into multiple sweep cycle segments, and each frame after slicing is a complete sweep cycle;

[0029] S4. The reference phase of the auxiliary interference reference signal in each sweep cycle is extracted through Hilbert transform, and is used to represent the nonlinearity of the sweep process; the instantaneous phase is calculated through the reference phase, and the phase jump is removed through unwrapping operation;

[0030] S5. The instantaneous frequency is calculated according to the time derivative of the reference phase, and is compared with the expected frequency of ideal linear sweep, to obtain the frequency deviation;

[0031] S6. Based on the nonlinearity of the instantaneous frequency, the microcavity array transmission spectrum signal is non-uniformly resampled, the signal is remapped to a uniform frequency axis, and the microcavity array transmission spectrum signal after compensation and correction is obtained;

[0032] S7. The position identification and shape resolution of the microcavity array resonance peak are performed on each frame of the microcavity array transmission spectrum signal after compensation and correction;

[0033] S8. The position or shape change of each microcavity resonance peak in each frame is tracked, and the sensing signal of the outside world is demodulated and read out.

[0034] The application provides a rapid demodulation method for a large-scale microcavity array on a chip.

[0035] Compared with the prior art, the application has the beneficial effects that:

[0036] The application provides a rapid demodulation system and method for a large-scale microcavity array on a chip, which utilizes a fast frequency-sweeping laser with a large bandwidth and a high frequency-sweeping rate to cooperate with a photodetector to collect the entire spectrum of the microcavity array for demodulation of a sensing signal, and simultaneously utilizes an auxiliary interference reference arm to compensate for errors caused by frequency-sweeping nonlinearity of the laser, so as to effectively suppress frequency-axis distortion and spectral line broadening caused by the frequency-sweeping nonlinearity of the laser, and the application can be applied to accurate demodulation of a large-scale, high-Q microcavity sensing array, solves the pain points of a small number of demodulation numbers and a complex demodulation method of a traditional microcavity sensing array, realizes rapid parallel demodulation of a large-scale microcavity sensing array, and reduces the system complexity. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 FIG. 1 is a structural schematic diagram of a rapid demodulation system for a large-scale microcavity array on a chip in an embodiment;

[0038] Figure 2 FIG. 2 is a schematic diagram of a 10*10 microcavity array in an embodiment;

[0039] Figure 3 FIG. 3 is a schematic diagram of transmission spectrum lines of 100 microcavity arrays in an embodiment;

[0040] Figure 4 FIG. 4 is a flowchart of a rapid demodulation method for a large-scale microcavity array on a chip in another embodiment.

[0041] In the drawings: 100, microcavity array transmission signal arm; 200, auxiliary interference reference arm; 300, same-frequency triggering arm; 1, frequency-sweeping laser; 2, first optical fiber coupler; 3, adjustable optical attenuator; 4, first polarization controller; 5, large-array microcavity sensor device on a chip; 6, first photodetector; 7, second optical fiber coupler; 8, optical fiber delay line; 9, second polarization controller; 10, third optical fiber coupler; 11, second photodetector; 12, signal processing device; 101, microcavity array transmission spectrum signal; 201, auxiliary interference reference signal; 301, same-frequency triggering signal. DETAILED DESCRIPTION

[0042] The application will be further described below in conjunction with the specific embodiments. Among them, the drawings are only used for exemplary description, and the representation is only a schematic diagram, not a physical diagram, and cannot be understood as a limitation on the application; in order to better illustrate the embodiments of the application, some components in the drawings will be omitted, enlarged or reduced, and do not represent the size of the actual product; for those skilled in the art, it is understandable that some well-known structures in the drawings and their descriptions can be omitted.

[0043] The same or similar reference numerals in the drawings of the embodiments of the application correspond to the same or similar components; in the description of the application, it should be understood that if the terms "upper", "lower", "left", "right" and the like indicate the orientation or positional relationship shown in the drawings, they are only for the convenience of describing the application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore the terms describing the positional relationship in the drawings are only used for exemplary description, and cannot be understood as a limitation on the application, for those skilled in the art, the specific meaning of the above terms can be understood according to the specific situation.

[0044] Embodiment one

[0045] The present embodiment is a first embodiment of a fast demodulation system for a large-scale microcavity array on a chip, as shown in Figure 1 , comprising:

[0046] a sweep laser 1;

[0047] a first fiber coupler 2: for receiving the light source of the sweep laser 1, and dividing the light source into a first light source and a second light source;

[0048] a microcavity array transmission signal arm 100: for receiving the first light source of the sweep laser 1, and after polarization processing of the first light source, entering the large array microcavity sensor device 5 on the chip, receiving the disturbance of the external sensing signal, and then converting into an electrical signal to obtain a microcavity array transmission spectrum signal 101;

[0049] an auxiliary interference reference arm 200: for receiving the second light source of the sweep laser 1, and processing the second light source to obtain two coherent lights with opposite phases, and then converting the coherent light into an electrical signal to obtain an auxiliary interference reference signal 201;

[0050] a same-frequency trigger arm 300: for transmitting the same-frequency trigger signal 301 emitted by the sweep laser 1;

[0051] a signal processing device 12: for collecting the microcavity array transmission spectrum signal 101, the auxiliary interference reference signal 201 and the same-frequency trigger signal 301, and after signal processing, obtaining a demodulated sensing signal.

[0052] This invention discloses a fast demodulation system for large-scale on-chip microcavity arrays. It utilizes a high-bandwidth, high-sweep-rate fast-sweep laser 1 in conjunction with a photodetector to acquire the entire spectrum of the microcavity array for demodulation of the sensing signal. Simultaneously, an auxiliary interferometric reference arm 200 compensates for errors caused by the sweep nonlinearity of the laser 1, effectively suppressing frequency axis distortion and spectral broadening resulting from the laser's sweep nonlinearity. This system is applicable to the precise demodulation of large-scale, high-Q microcavity sensing arrays, solving the problems of limited demodulation numbers and complex demodulation methods in traditional micro-ring sensing arrays. It achieves fast parallel demodulation of large-scale microcavity sensing arrays, reducing system complexity.

[0053] Example 2

[0054] This embodiment is a second embodiment of a fast demodulation system for on-chip large-scale microcavity arrays. This embodiment is similar to the first embodiment, except that, as Figure 1 As shown, in this embodiment, the microcavity array transmission signal arm 100 includes a first polarization controller 4, an on-chip large array microcavity sensor 5, and a first photodetector 6 connected in sequence. The input end of the first polarization controller 4 is connected to the first output end of the first fiber coupler 2; the output end of the first photodetector 6 is connected to the signal processing device 12. The swept-frequency light source entering the cavity array transmission signal arm, i.e., the first light source, first passes through the first polarization controller 4, and after polarization processing, enters the on-chip large array microcavity sensor 5. At this time, after receiving disturbances from external sensing signals, it enters the first photodetector 6 and is converted into an electrical signal—an auxiliary interference reference signal 201. Finally, it enters the signal processing device 12, which performs data acquisition and processing on the auxiliary interference reference signal 201.

[0055] The auxiliary interference reference arm 200 comprises a second fiber coupler 7, a fiber delay line 8, a second polarization controller 9, a third fiber coupler 10 and a second photodetector 11; the input end of the second fiber coupler 7 is connected with the second output end of the first fiber coupler 2, the first output end of the second fiber coupler 7 is connected with the first input end of the third fiber coupler 10, the second output end of the second fiber coupler 7 is connected with the input end of the second polarization controller 9 through the fiber delay line 8, the output end of the second polarization controller 9 is connected with the second input end of the third fiber coupler 10, the output end of the third fiber coupler 10 is connected with the input end of the second photodetector 11, and the output end of the second photodetector 11 is connected with the signal processing device 12. The swept light source entering the auxiliary interference reference arm 200, i.e. the second light source, first enters the second fiber coupler 7, and the second fiber coupler 7 divides the second light source into two light sources, which enter the upper and lower arms respectively, wherein the light source of the upper arm directly enters the third fiber coupler 10, and the light source of the lower arm enters the third fiber coupler 10 after passing through the fiber delay line 8 and the second polarization controller 9 in sequence; in the third fiber coupler 10, the light of the upper and lower arms interferes to obtain two coherent lights with opposite phases, and the coherent light enters the second photodetector 11 to be converted into an electrical signal, i.e. an auxiliary interference reference signal 201, and the auxiliary interference reference signal 201 enters the signal processing device 12 for data acquisition and processing.

[0056] In the present application, the fast swept laser 1 is used as the core device of the overall demodulation system, and the swept bandwidth thereof determines the number of microcavities that can be covered, and the swept rate thereof determines the sensing applications that can be demodulated. When the system is used to realize parallel demodulation of a microcavity array device on a chip, the sensing signal is contained in the demodulated transmission spectrum signal, for example, by tracking the drift of the microcavity resonance peak in each frame of transmission spectrum signal, so as to calibrate the external sensing signal causing the change. For example, the continuous swept range of the fast swept laser 1 reaches 500 GHz, and the range can cover more than 100 microloops; when the swept rate of the fast swept laser 1 reaches hundreds of hertz or thousands of hertz, low-frequency vibration or stress sensing and the like can be demodulated, for example, pulse sensing; when the swept rate reaches megahertz, high-frequency ultrasonic sensing, photoacoustic imaging and the like can be demodulated.

[0057] In the present embodiment, the length of the fiber delay line 8 is generally greater than the length of the measured device, because the auxiliary interference reference signal 201 needs to cover the entire signal frequency range of the measured device. In the present application, the on-chip large-array microcavity sensor device 5 is generally short in length, and a 10 m fiber delay line 8 can be used, and other lengths can also be used in actual application.

[0058] In the embodiment, the first fiber coupler 2 divides the light source into the first light source and the second light source according to the splitting ratio of N1:N2, and the value of N1 is greater than the value of N2. The splitting ratio of the first fiber coupler 2 is 9:1, wherein 90% of the light, that is, most of the light, enters the microcavity array transmission signal arm 100, which takes into account the large device loss that may be introduced by the subsequent on-chip large array microcavity sensor device 5. And 10% of the light enters the auxiliary interference reference arm 200 through the second fiber coupler 7, which has very small loss and requires less light intensity. In actual application, according to the different losses of the microcavity array transmission signal arm 100 and the auxiliary interference reference arm 200, other splitting ratio fiber couplers can also be selected, such as 8:2, 99:1, etc.

[0059] In the embodiment, the second fiber coupler 7 divides the second light source into the third light source and the fourth light source according to the splitting ratio of 1:1.

[0060] In the embodiment, the microcavity structure of the on-chip large array microcavity sensor device 5 includes a micro-ring resonant cavity, a Fabry-Perot resonant cavity, or a photonic crystal resonant cavity; and is prepared by using a chalcogenide material. The microcavity structure of the on-chip large array microcavity sensor device 5 can be a micro-ring resonant cavity, a Fabry-Perot resonant cavity, a photonic crystal microcavity, etc. In the present application, a chalcogenide material is used to prepare an array microcavity device containing 100 micro-ring resonant cavities, the structure and transmission spectrum of which are shown in Figure 2 and Figure 3 The preparation process of the on-chip large array microcavity sensor device 5 includes: preparing a high-quality chalcogenide film on a silicon dioxide substrate by a vacuum thermal evaporation method, spin-coating an electron beam exposure glue, and etching a microcavity array structure by using an electron beam lithography method, and then treating by a reactive ion beam etching after development.

[0061] In the embodiment, the first photodetector 6 is an avalanche photodetector, and the second photodetector 11 is a balanced photodetector. The avalanche photodetector uses the avalanche multiplication effect to amplify the photo-generated carriers twice inside the device, and has high gain. Since the microcavity array has large device loss, it will cause a large drop in optical power, so the avalanche photodetector is suitable for detecting weak optical signals after the microcavity array. In actual use, when there is no avalanche photodetector, a common photodetector such as a PIN diode can also be used for detection, but an additional amplifier needs to be introduced at the front end to further amplify the optical signal, such as an erbium-doped fiber amplifier, and additional spontaneous emission noise may be introduced.

[0062] In the embodiment, the swept laser 1, the first fiber coupler 2, the second fiber coupler 7, the fiber delay line 8, the second polarization controller 9, the third fiber coupler 10, the second photodetector 11, the first photodetector 6, the large array of microcavity sensor on chip 5 and the first photodetector 6 are connected through optical fibers; the swept laser 1, the first photodetector 6 and the second photodetector 11 are connected with the signal processing device 12 through cables; the large array of microcavity sensor on chip 5 is connected with the optical fiber through fiber end face coupling or grating vertical coupling.

[0063] The working principle of the fast demodulation system for the large array of microcavities on chip in the embodiment is as follows:

[0064] The swept laser 1 emits swept light, which is divided into 10% second light source and 90% first light source through the first fiber coupler 2, wherein the 10% light enters the second fiber coupler 7 to serve as the light source of the auxiliary interference reference arm 200, and the other 90% light enters the first polarization coupler to serve as the light source of the microcavity array transmission signal arm 100. After the 10% light enters the second fiber coupler 7, the light is again divided into 50% and 50% two parts, which enter the upper and lower arms, wherein the light of the upper arm directly enters the third fiber coupler 10, and the light of the lower arm enters the third fiber coupler 10 after passing through the fiber delay line 8 and the second polarization controller 9. In the third fiber coupler 10, the light of the upper and lower arms interferes to obtain two coherent lights with opposite phases, which enter the second photodetector 11 to be converted into an electric signal, and the signal processing device 12 collects and processes data. The swept light entering the first polarization coupler enters the large array of microcavity sensor on chip 5 after passing through the second polarization controller 9, receives the disturbance of the external sensing signal, enters the first photodetector 6 to be converted into an electric signal, and then enters the signal processing device 12 to collect and process data. At the same time, the swept laser 1 sends a synchronous trigger signal of sweeping to the signal processing device 12 through the same frequency trigger arm 300.

[0065] Embodiment three

[0066] The third embodiment of the fast demodulation system for the large-scale microcavity array on chip is similar to the second embodiment, except that the microcavity array transmission signal arm 100 further comprises an adjustable optical attenuator 3, and the first output end of the first fiber coupler 2 is connected with the first polarization controller 4 through the adjustable optical attenuator 3. The adjustable optical attenuator 3 is located before the first polarization controller 4 on the chip. The first light source first enters the adjustable optical attenuator 3, and then enters the large-array microcavity sensor device 5 on the chip through the first polarization controller 4, which is used to adjust the optical power entering the large-array microcavity sensor device 5 on the chip, so as to avoid the device from being detuned due to excessive light intensity entering the large-array microcavity sensor device 5 on the chip. In actual application, the adjustable optical attenuator 3 can also be omitted according to the different output optical powers of the aforementioned fast frequency sweeping laser 1 and the different splitting ratios of the first fiber coupler 2.

[0067] Embodiment four

[0068] The embodiment is an embodiment of a fast demodulation method for a large-scale microcavity array on chip. The embodiment adopts the fast demodulation system for the large-scale microcavity array on chip in any one of the above embodiments one to three, as shown in FIG. 8, and comprises the following steps: Figure 4

[0069] S1. At the signal processing device 12, the microcavity array transmission spectrum signal 101, the auxiliary interference reference signal 201, and the same-frequency trigger signal 301 are acquired respectively;

[0070] S2. The signal alignment is performed through cross-correlation operation, the time delay difference of the microcavity array transmission spectrum signal 101, the auxiliary interference reference signal 201, and the same-frequency trigger signal 301 is subtracted, and filtering and denoising processing is performed;

[0071] S3. According to the rising edge of the same-frequency trigger signal 301 of the frequency sweeping laser 1, the microcavity array transmission spectrum signal 101 and the auxiliary interference reference signal 201 are data-synchronized and sliced, and are divided into multiple frequency sweeping period segments. Each frame after slicing is a complete frequency sweeping period;

[0072] S4. The reference phase of the auxiliary interference reference signal 201 in each frequency sweeping period is extracted through Hilbert transform, which is used to represent the nonlinearity of the frequency sweeping process. The instantaneous phase is calculated through the reference phase, and the phase jump is removed through unwrapping operation;

[0073] S5. The instantaneous frequency is calculated according to the time derivative of the reference phase, and compared with the expected frequency of the ideal linear frequency sweeping, to obtain the frequency deviation;

[0074] ​S6. Based on the nonlinear characteristics of the instantaneous frequency, the microcavity array transmission spectrum signal 101 is non-uniformly resampled, the signal is remapped to a uniform frequency axis, and a compensated and corrected microcavity array transmission spectrum signal 101 is obtained;

[0075] S7. For each frame of the compensated and corrected microcavity array transmission spectrum signal 101, the position identification and shape resolution of the microcavity array resonance peak are performed.

[0076] S8. The position or shape change of each microcavity resonance peak in each frame is tracked, and the external sensing signal is demodulated and read out.

[0077] The application provides a fast demodulation method for a large-scale microcavity array on a chip, which realizes parallel demodulation of microcavity array sensing by using a fast sweep laser 1 combined with a high-speed photoelectric detector, solves the pain points of the traditional micro-ring sensor array demodulation, such as small number of demodulation and complex demodulation method, and further expands the application scenarios of the microcavity array sensing on the chip.

[0078] The existing sweep laser 1 is difficult to maintain completely linear sweep when the sweep rate is fast. In the transmission spectrum of the microcavity sensor, the position of the resonance peak is the core parameter of the sensor. If the sweep rate of the laser is uneven, the frequency intervals corresponding to the data points collected at equal time intervals are inconsistent. In the finally generated transmission spectrum, the scale of the frequency axis will be nonlinearly distorted, resulting in deviation of the actual position of the resonance peak from the measured position, and even causing distortion of the spectrum line shape and reduction of the resolution. The fast demodulation system and method for a large-scale microcavity array on a chip proposed in the application uses an auxiliary interference arm to compensate for the error caused by the nonlinear sweep of the sweep laser 1, effectively suppresses the frequency axis distortion and spectrum line broadening caused by the nonlinear sweep of the laser, and can be applied to the accurate demodulation of a large-scale, high-Q microcavity sensor array, which opens up a new way for the application of integrated optical microcavity sensing, and has broad application potential in the fields of material detection, trace analysis, wearable physiological signal monitoring, etc.

[0079] In the specific content of the above specific embodiments, any non-contradictory combination of technical features can be made, and in order to make the description concise, not all possible combinations of the above technical features are described, however, as long as the combination of these technical features does not exist contradiction, it should be considered as the scope of the description.

[0080] Obviously, the above embodiments of the present application are merely exemplary but not intended to limit the embodiments of the present application. Based on the above description, any other variations or changes can be made by those skilled in the art without departing from the spirit and principles of the present application. It is not necessary to list all the embodiments here. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall fall within the scope of the claims of the present application.

Claims

1. A fast demodulation system for a large array of on-chip microcavities, characterized in that, include: Frequency-sweeping laser (1); First fiber coupler (2): used to receive the light source of the swept laser (1) and divide the light source into a first light source and a second light source; Microcavity array transmission signal arm (100): used to receive the first light source of the sweep laser (1). After polarization processing, the first light source enters the on-chip large array microcavity sensor device (5). After receiving the disturbance of the external sensing signal, it is converted into an electrical signal to obtain the microcavity array transmission spectrum signal (101). Auxiliary interference reference arm (200): used to receive the second light source of the swept laser (1), and process the second light source to obtain two coherent beams with opposite phases, and then convert the coherent beams into electrical signals to obtain auxiliary interference reference signals (201); the auxiliary interference reference arm (200) includes a second fiber coupler (7), a fiber delay line (8), a second polarization controller (9), a third fiber coupler (10) and a second photodetector (11); the input end of the second fiber coupler (7) is connected to the second output end of the first fiber coupler (2), the first output end of the second fiber coupler (7) is connected to the first input end of the third fiber coupler (10), the second output end of the second fiber coupler (7) is connected to the input end of the second polarization controller (9) after passing through the fiber delay line (8), the output end of the second polarization controller (9) is connected to the second input end of the third fiber coupler (10), the output end of the third fiber coupler (10) is connected to the input end of the second photodetector (11), and the output end of the second photodetector (11) is connected to the signal processing device (12); Same frequency trigger arm (300): used to transmit the same frequency trigger signal (301) emitted by the sweep frequency laser (1); Signal processing device (12): used to acquire the microcavity array transmission spectrum signal (101), auxiliary interference reference signal (201) and same frequency trigger signal (301), and after signal processing, obtain the demodulated sensing signal.

2. The fast demodulation system for large array of on-chip massive microcavities according to claim 1, wherein, The microcavity array transmission signal arm (100) includes a first polarization controller (4), an on-chip large array microcavity sensor (5), and a first photodetector (6) connected in sequence; the input end of the first polarization controller (4) is connected to the first output end of the first fiber coupler (2); the output end of the first photodetector (6) is connected to the signal processing device (12).

3. The fast demodulation system for large array of on-chip massive microcavities according to claim 2, wherein, The microcavity array transmission signal arm (100) also includes an adjustable optical attenuator (3), and the first output end of the first fiber coupler (2) is connected to the first polarization controller (4) after passing through the adjustable optical attenuator (3).

4. The fast demodulation system for large array of on-chip massive microcavities of claim 1, wherein, The first fiber coupler (2) divides the light source into a first light source and a second light source according to a splitting ratio of N1:N2, and the value of N1 is greater than the value of N2.

5. The fast demodulation system for large array of on-chip massive microcavities of claim 1, wherein, The second fiber coupler (7) divides the second light source into a third light source and a fourth light source according to a splitting ratio of 1:

1.

6. The fast demodulation system for large-scale microcavity array on chip according to any one of claims 2 to 5, characterized in that, The microcavity structure of the large-array-on-chip microcavity sensor device (5) comprises a micro-ring resonant cavity, a Fabry-Perot resonant cavity or a photonic crystal resonant cavity; and the large-array-on-chip microcavity sensor device (5) is prepared from a chalcogenide material.

7. The fast demodulation system for large array of on-chip massive microcavities of claim 2, wherein, The first photodetector (6) is an avalanche photodetector, and the second photodetector (11) is a balanced photodetector.

8. The fast demodulation system for large array of on-chip massive microcavities of claim 5, wherein, The sweep laser (1), the first fiber coupler (2), the second fiber coupler (7), the fiber delay line (8), the second polarization controller (9), the third fiber coupler (10), the second photodetector (11), the large-array-on-chip microcavity sensor device (5) and the first photodetector (6) are connected through optical fibers; the sweep laser (1), the first photodetector (6) and the second photodetector (11) are connected to the signal processing device (12) through cables; and the large-array-on-chip microcavity sensor device (5) is connected to the optical fiber through fiber end face coupling or grating vertical coupling.

9. A fast demodulation method for a large-scale microcavity array on-chip, characterized in that, The fast demodulation system for the large-scale microcavity array on chip according to any one of claims 1 to 8 comprises the following steps: S1. At the signal processing device (12), the microcavity array transmission spectrum signal (101), the auxiliary interference reference signal (201) and the same frequency trigger signal (301) are acquired respectively; S2. The signal alignment is performed through cross-correlation operation, the delay difference of the microcavity array transmission spectrum signal (101), the auxiliary interference reference signal (201) and the same frequency trigger signal (301) is compensated, and the filtering denoising processing is performed; S3. According to the rising edge of the sweep laser (1) same frequency trigger signal (301), the microcavity array transmission spectrum signal (101) and the auxiliary interference reference signal (201) are data-synchronized and sliced, and are divided into multiple sweep frequency period segments; each frame after slicing is a complete sweep frequency period; S4. The reference phase of the auxiliary interference reference signal (201) in each sweep frequency period is extracted through Hilbert transform, and is used to represent the nonlinearity of the sweep process; the instantaneous phase is calculated through the reference phase, and the phase jump is removed through unwrapping operation; S5. The instantaneous frequency is calculated according to the time derivative of the reference phase, and is compared with the expected frequency of the ideal linear sweep, to obtain the frequency deviation; S6. Based on the nonlinearity of the instantaneous frequency, the microcavity array transmission spectrum signal (101) is non-uniformly resampled, the signal is remapped to a uniform frequency axis, and the microcavity array transmission spectrum signal (101) after compensation and correction is obtained; S7. The position identification and shape resolution of the microcavity array resonant peak are performed on each frame of the microcavity array transmission spectrum signal (101) after compensation and correction; S8. The position or shape change of each microcavity resonant peak in each frame is tracked, and the sensing signal of the outside world is demodulated and read out.

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