Wavelength locking system of silicon oxide micro-ring resonator

Abstract

The invention discloses a wavelength locking system of a silicon oxide micro-ring resonator, which comprises a photoelectric conversion module, a feedback control module, a radio frequency driving module, an interdigital transducer, a zinc oxide film, a phase-locked amplification module, two analog-to-digital conversion modules and a digital-to-analog conversion module, the zinc oxide film generates mechanical vibration to form surface acoustic waves which are transmitted to the vicinity of the silicon oxide micro-ring resonator, mechanical stress and strain are triggered, the refractive index distribution of the silicon oxide micro-ring resonator is changed, and the frequency, phase and intensity of an internal optical signal are modulated. The feedback control module feeds back and adjusts the thermal power of the micro-ring heater based on voltage signals output by the phase-locked amplification module and the photoelectric conversion module, and adjusts the resonant wavelength of the silicon oxide micro-ring resonator, so that the wavelength of an optical signal output by the silicon oxide micro-ring resonator is locked at a target wavelength; the method has the advantages that accurate wavelength locking can be carried out on the silicon oxide micro-ring resonator, and the wavelength locking effect is good.

Description

Technical Field

[0001] The invention relates to a wavelength locking system, in particular to a wavelength locking system of a silicon oxide micro-ring resonator. Background Art

[0002] With the advent of the information age, information technologies such as cloud computing, big data, the Internet of Things, and artificial intelligence are developing rapidly. The digital transformation of traditional industries and the way of life of the masses is accelerating, which undoubtedly poses greater challenges to the data transmission rate and stability of communication networks. Optical communication is a communication method that uses light as a transmission medium, usually transmitting signals through optical fibers. Compared with traditional electrical communications using copper cables as the medium, optical communications have significant advantages in transmission rate, data capacity, network bandwidth, signal crosstalk, transmission distance, signal attenuation, and anti-electromagnetic interference, and are developing towards the goal of longer distances, higher rates, and larger capacities.

[0003] As one of the important photonic devices, the microring resonator (MRR) has a relatively simple structure and is usually composed of straight waveguides and curved waveguides. Common waveguide materials include silicon (Si) and silicon oxide (SiO2). The radius of the microring resonator implemented with silicon material (i.e., silicon-based microring resonator) is only a few microns. It is small in size and has good performance, which is suitable for high integration with very large-scale integrated circuits (VLSI). The microring resonator implemented with silicon oxide material (i.e., silicon oxide microring resonator) has a simple manufacturing process and low waveguide loss. It is usually used to make large-radius sensor devices and optical gyroscopes. Regardless of the material of the microring resonator, it has the advantages of wavelength selection, compact structure, and compatibility with CMOS technology. Due to these characteristics, it is widely used in optical filters, optical delay lines, biosensors, optical neural networks and other fields.

[0004] In practical applications, microring resonators are usually integrated with microring heaters to form an optical chip. When a silicon-based microring resonator is integrated with a microring heater, silicon material is used as the substrate and silicon oxide material is used as the cladding. The microring resonator is attached to the substrate and the microring heater is attached to the cladding. When a silicon oxide microring resonator is integrated with a microring heater, silicon oxide material is used as the substrate and the cladding. The silicon oxide microring resonator is attached to the substrate and the microring heater is attached to the cladding.

[0005] The working performance of the microring resonator is easily affected by the manufacturing process and temperature fluctuations. During the manufacturing process, slight changes in the geometric dimensions of its waveguide often cause the resonant wavelength of the microring resonator to "drift" by ±1nm. In addition, the resonant wavelength of the microring resonator will also "drift" with changes in temperature. The misalignment between the input laser wavelength and the resonant wavelength of the microring resonator will cause the working performance of the microring resonator to deteriorate. Especially in scenarios that require high precision, such as data center interconnection, optical biosensing, quantum communication and other application scenarios, there are more stringent requirements for the accuracy of the resonant wavelength of the microring resonator. Therefore, in order to eliminate the interference caused by "temperature drift" and process errors and ensure the normal operation of the microring resonator, it is necessary to first solve the problem of self-calibration and locking of the resonant wavelength of the microring resonator.

[0006] Bergman et al. of Columbia University designed a microring resonator thermal stability feedback control system, namely, a wavelength locking system for microring resonators. The wavelength locking system includes a jitter signal module, a photoelectric conversion module, an AD633 module, a low-pass filter module, and a feedback control module. The jitter signal module outputs a jitter electrical signal to the microring heater and the AD633 module. Under the control of the jitter electrical signal output by the jitter signal module, the microring heater generates a corresponding thermal wave action to act on the microring resonator. The optical signal in the microring resonator is thermally modulated, and the modulated optical signal is then output to the photoelectric conversion module. The photoelectric conversion module converts the optical signal output by the microring resonator into a voltage signal and outputs it to the AD633 module. The AD633 module mixes the voltage signal from the photoelectric conversion module and the jitter electrical signal from the jitter module to obtain a mixed signal, which is output to the low-pass filter module. The low-pass filter module performs low-pass filtering on the mixed signal from the AD633 module to obtain a filtered signal, that is, an error signal, which is output to the feedback control module. The feedback control module outputs a feedback voltage to the microring heater according to the error signal from the AD633 module. The feedback voltage is superimposed on the jitter electrical signal output by the jitter signal module to adjust the thermal power of the microring heater, change the thermal power output by the microring heater, and then change the resonant wavelength of the microring resonator.

[0007] The thermal stability feedback control system of the microring resonator uses a thermo-optical modulation method to lock the wavelength. Since the thermal conductivity of silicon materials is relatively high, it can lock the resonant wavelength of silicon-based microring resonators more accurately. However, the thermal conductivity of silicon oxide materials is low, and the thermal stability feedback control system of the microring resonator cannot quickly and effectively modulate the optical signal in the silicon oxide microring resonator, so that a series of subsequent responses will be delayed. These delays weaken the ability of the thermal stability feedback control system of the microring resonator to compensate for the drift of the resonant wavelength of the silicon oxide microring resonator in a timely manner. Therefore, the thermal stability feedback control system of the microring resonator cannot accurately lock the wavelength of the silicon oxide microring resonator, and the locking effect of the wavelength of the silicon oxide microring resonator is not ideal. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide a wavelength locking system for a silicon oxide microring resonator which can accurately lock the wavelength of the silicon oxide microring resonator and has a good wavelength locking effect.

[0009] The technical solution adopted by the present invention to solve the above technical problems is: a wavelength locking system of a silicon oxide microring resonator, including a photoelectric conversion module and a feedback control module, wherein the photoelectric conversion module is used to receive an optical signal output by the silicon oxide microring resonator and convert the optical signal into a voltage signal for output, and further includes a radio frequency driving module, an interdigital transducer, a zinc oxide film for generating a piezoelectric effect, a phase-locked amplifier module, two analog-to-digital conversion modules and a digital-to-analog conversion module, wherein the two analog-to-digital conversion modules are respectively referred to as a first analog-to-digital conversion module and a second analog-to-digital conversion module; the radio frequency driving module is used to generate an alternating electrical signal output, and the zinc oxide film is covered on a cladding of an optical chip formed by integrating the silicon oxide microring resonator and the microring heater. , the cladding is separated from the micro-ring heater, and the micro-ring heater is attached thereto, the interdigital transducer is attached to the zinc oxide film, the interdigital transducer is used to access the alternating electric signal output by the radio frequency driving module, and under the excitation of the alternating electric signal, a periodic surface acoustic wave is generated and transmitted to the silicon oxide micro-ring resonator, and the optical signal inside the silicon oxide micro-ring resonator is periodically interacted, and the optical signal inside the silicon oxide micro-ring resonator is modulated, and the modulated optical signal is output to the photoelectric conversion module, and the photoelectric conversion module is used to convert the optical signal output by the silicon oxide micro-ring resonator to the optical signal, and the voltage signal is output to the phase-locked amplifier module, and the phase-locked amplifier module The first analog-to-digital conversion module is used to access the voltage signal output by the photoelectric conversion module and the alternating electric signal output by the radio frequency driving module, and coherently demodulate the accessed voltage signal and the alternating electric signal to obtain a voltage signal that characterizes the spectrum information and spectrum slope information of the optical signal inside the silicon oxide microring resonator and output it to the first analog-to-digital conversion module. The first analog-to-digital conversion module is used to periodically sample the voltage signal output by the phase-locked amplifier module, and each period of sampling obtains a sampling signal that is output to the feedback control module. The second analog-to-digital conversion module is used to access the voltage signal output by the photoelectric conversion module, and periodically sample the accessed voltage signal, and each period of sampling obtains a sampling signal. The signal is output to the feedback control module, the sampling frequency of the second analog-to-digital conversion module is the same as that of the first analog-to-digital conversion module, the feedback control module is used to obtain the feedback control signal of each cycle according to the sampling signal outputted thereto by the first analog-to-digital conversion module and the second analog-to-digital conversion module in each cycle, and output it to the digital-to-analog conversion module, the digital-to-analog conversion module is used to perform digital-to-analog conversion on the feedback control signal of each cycle outputted thereto by the feedback control module, obtain the feedback control voltage and output it to the micro-ring heater, adjust the thermal power of the micro-ring heater in real time, and then adjust the resonant wavelength of the silicon oxide micro-ring resonator, so that the optical signal outputted by the silicon oxide micro-ring resonator is locked at the target wavelength.

[0010] Compared with the prior art, the advantages of the present invention are that by setting a radio frequency driving module, an interdigital transducer, a zinc oxide film, a phase-locked amplifier module, two analog-to-digital conversion modules and a digital-to-analog conversion module, when the alternating electrical signal generated by the radio frequency driving module is applied to the interdigital transducer, since the interdigital transducer is attached to the zinc oxide film, the zinc oxide film will generate mechanical vibration due to the electrostrictive effect, and a surface acoustic wave will be formed on its surface. When the surface acoustic wave propagates to the vicinity of the silicon oxide microring resonator, mechanical stress and strain are induced, thereby changing the refractive index distribution of the silicon oxide microring resonator, and modulating the frequency, phase and intensity of the optical signal inside the silicon oxide microring resonator. In addition, the phase-locked amplifier module accesses the voltage signal output by the photoelectric conversion module and the alternating electrical signal output by the radio frequency driving module, and coherently demodulates the accessed voltage signal and the alternating electrical signal to obtain a voltage signal representing the spectrum information and spectrum slope information of the optical signal inside the silicon oxide microring resonator. The first analog-to-digital conversion module and the second analog-to-digital converter respectively convert the voltage signal and the photoelectric signal output by the phase-locked amplifier module into a voltage signal. The voltage signal output by the conversion module is periodically sampled in real time to obtain periodic sampling data. The feedback control module obtains an error signal based on the periodic sampling data obtained by the first analog-to-digital conversion module and the second analog-to-digital converter. The thermal power of the microring heater is adjusted based on the error signal feedback, and the resonant wavelength of the silicon oxide microring resonator is adjusted to lock the wavelength of the optical signal output by the silicon oxide microring resonator at the target wavelength. It can be seen that the present invention adopts an acousto-optic modulation mechanism based on an interdigital transducer and a feedback mechanism implemented by a feedback control module to synchronously tune the resonant wavelength of the silicon oxide microring resonator, which is independent of the thermal conductivity characteristics of the material and is thus not limited by the low thermal conductivity efficiency of the silicon oxide material. The error signal characterizing the current state of the silicon oxide microring resonator can be extracted more quickly to tune the silicon oxide microring resonator, and the response speed is fast, which significantly improves the modulation rate of the silicon oxide microring resonator, has strong real-time feedback capability and adjustment capability, and can accurately lock the wavelength of the silicon oxide microring resonator, achieving a wavelength locking effect.

[0011] Further, the voltage signal output by the photoelectric conversion module is recorded as V0, the voltage signal output by the phase-locked amplifier module is recorded as V1, the sampling frequencies of the first analog-to-digital conversion module and the second analog-to-digital conversion module are the same, the sequence index of the sampling moments of the first analog-to-digital conversion module and the second analog-to-digital conversion module is recorded as n, n=1, 2, 3, ...; the sampling signal obtained by the second analog-to-digital conversion module at the nth sampling moment is recorded as V0[n], the sampling signal obtained by the first analog-to-digital conversion module at the nth sampling moment is recorded as V1[n], and the feedback control signal at the nth sampling moment obtained by the feedback control module according to the sampling signal output by the first analog-to-digital conversion module and the second analog-to-digital conversion module at the nth sampling moment is recorded as Vheater[n]; the specific process of the feedback control module obtaining the feedback control signal Vheater[n] at the nth sampling moment according to the sampling signal output by the first analog-to-digital conversion module and the second analog-to-digital conversion module at the nth sampling moment is:

[0012] Step 1: Set the feedback error signal at the nth sampling moment to Feedback[n] and the slope to k[n], and use formulas (1) and (2) to calculate Feedback[n] and k[n] respectively:

[0013] Feedback[n]=V1[n] / V0[n] (1)

[0014] k[n]={V1[n]-V1[n-1]} / {V0[n]-V0[n-1]} (2)

[0015] In formula (1), when n=1, V1[n-1]=0, V0[n-1]=0, when n≠1, V1[n-1] represents the sampling signal obtained by the first analog-to-digital conversion module at the n-1th sampling time, and V0[n-1] represents the sampling signal obtained by the second analog-to-digital conversion module at the n-1th sampling time;

[0016] Step 2: Determine Vheater[n] based on Feedback[n] and k[n], specifically:

[0017] If Feedback[n] is less than 0, and k[n] is less than or equal to 0, then Vheater[n] = Vheater[n-1] + 0.1;

[0018] If Feedback[n] is less than 0 and k[n] is greater than 0, then Vheater[n] = Vheater[n-1] + 0.01;

[0019] If Feedback[n] is greater than 0 and k[n] is greater than 0, then Vheater[n] = Vheater[n-1]-0.01;

[0020] If Feedback[n] is greater than 0, and k[n] is less than or equal to 0, then Vheater[n] = Vheater[n-1]-0.1;

[0021] If Feedback[n] is equal to 0, then directly set Vheater[n] = Vheater[n-1];

[0022] Among them, when n=1, Vheater[n-1]=0, when n≠1, Vheater[n-1] represents the feedback control signal at the n-1th sampling moment obtained by the feedback control module based on the sampling signal output to it by the first analog-to-digital conversion module and the second analog-to-digital conversion module at the n-1th sampling moment.

[0023] Furthermore, the photoelectric conversion module includes a photodiode, a first operational amplifier, a first resistor and a first capacitor. The first operational amplifier has a non-inverting end, an inverting end, an output end, a positive power supply end and a negative power supply end. The positive electrode of the photodiode and the non-inverting end of the first operational amplifier are both grounded, the negative electrode of the photodiode, the inverting end of the first operational amplifier, one end of the first resistor and one end of the first capacitor are connected, the positive power supply end of the first operational amplifier is connected to a positive voltage VCC, the negative power supply end of the first operational amplifier is connected to a negative voltage VEE, the output end of the first operational amplifier, the other end of the first resistor and the other end of the first capacitor are connected, and the connection end is the output end of the photoelectric conversion module. The photodiode is used to receive the optical signal generated by the silicon oxide microring resonator under the excitation of an external optical signal, and the output end of the photoelectric conversion module is used to output a voltage signal.

[0024] Furthermore, the phase-locked amplifier module includes a multiplier and a low-pass filter. The multiplier includes a first chip of model AD633, a second capacitor and a second resistor. The X1 pin of the first chip is respectively connected to one end of the second capacitor and one end of the second resistor, the other end of the second resistor, the X2 pin, the Y2 pin and the Z pin of the first chip are all grounded, the other end of the second capacitor is the first input end of the multiplier, which is used to access the voltage signal output by the photoelectric conversion module, the Y1 pin of the first chip is the second input end of the multiplier, which is used to access the alternating electric signal output by the radio frequency driving module, the W pin of the first chip is the output end of the multiplier, the VS+ pin of the first chip is connected to the positive power supply, and the VS- pin of the first chip is connected to the negative power supply; the low-pass filter has an input end and an output end, the input end of the low-pass filter is connected to the output end of the multiplier, and the output end of the low-pass filter is used to output a voltage signal representing the spectrum information and spectrum slope information of the silicon oxide microring resonator.

[0025] Further, the low-pass filter includes a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a seventh capacitor, an eighth capacitor, a ninth capacitor, a second operational amplifier, a third operational amplifier, a fourth operational amplifier and a fifth operational amplifier. The second operational amplifier, the third operational amplifier, the fourth operational amplifier and the fifth operational amplifier all have a common-phase terminal, an inverting terminal, an output terminal, a positive power supply terminal and a negative power supply terminal. The positive power supply terminals of the second operational amplifier, the third operational amplifier, the fourth operational amplifier and the fifth operational amplifier are all connected to a positive voltage VCC, and the negative power supply terminals of the second operational amplifier, the third operational amplifier, the fourth operational amplifier and the fifth operational amplifier are all connected to a negative voltage VEE. One end of the third resistor is the input end of the low-pass filter, and the other end of the third resistor is respectively connected to one end of the fourth resistor and one end of the fourth capacitor. The other end of the fourth resistor is respectively connected to one end of the third capacitor and the common-phase terminal of the second operational amplifier. The second operational amplifier The inverting end and output end of the fourth operational amplifier, the other end of the fourth capacitor and one end of the fifth resistor are connected, the other end of the fifth resistor is respectively connected to one end of the sixth resistor and one end of the sixth capacitor, the other end of the sixth resistor is respectively connected to one end of the fifth capacitor and the non-inverting end of the third operational amplifier, the inverting end and output end of the third operational amplifier, the other end of the sixth capacitor and one end of the eighth resistor are connected, the other end of the eighth resistor is respectively connected to one end of the seventh resistor and one end of the eighth capacitor, the other end of the seventh resistor is respectively connected to one end of the seventh capacitor and the non-inverting end of the fourth operational amplifier, the inverting end and output end of the fourth operational amplifier, the other end of the eighth capacitor and one end of the ninth resistor, the other end of the ninth resistor is respectively connected to one end of the ninth capacitor and the non-inverting end of the fifth operational amplifier, the inverting end and output end of the fifth operational amplifier are connected, and the connection end thereof is the output end of the low-pass filter, the other end of the third capacitor, the other end of the fifth capacitor, the other end of the seventh capacitor and the other end of the ninth capacitor are all grounded.

[0026] Furthermore, the thickness of the zinc oxide film is 2.2 microns. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural block diagram of the wavelength locking system of the silicon oxide microring resonator of the present invention;

[0028] Figure 2A top view of the optical chip when the interdigital transducer and the zinc oxide film of the wavelength locking system of the silicon oxide microring resonator of the present invention are integrated on the optical chip;

[0029] Figure 3 A cross-sectional view of an optical chip when the interdigital transducer and the zinc oxide film of the wavelength locking system of the silicon oxide microring resonator of the present invention are integrated on the optical chip;

[0030] Figure 4 A circuit diagram of a photoelectric conversion module of a wavelength locking system of a silicon oxide microring resonator of the present invention;

[0031] Figure 5 The circuit diagram of the phase-locked amplifier module of the wavelength locking system of the silicon oxide microring resonator of the present invention. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below with reference to the accompanying drawings.

[0033] Embodiment 1: Figures 1 to 3As shown, a wavelength locking system for a silicon oxide microring resonator includes a photoelectric conversion module and a feedback control module. The photoelectric conversion module is used to receive an optical signal output by the silicon oxide microring resonator and convert the optical signal into a voltage signal for output. The system also includes a radio frequency driving module, an interdigital transducer, a zinc oxide film for generating a piezoelectric effect, a phase-locked amplifier module, two analog-to-digital conversion modules and a digital-to-analog conversion module. The two analog-to-digital conversion modules are respectively referred to as a first analog-to-digital conversion module and a second analog-to-digital conversion module. The radio frequency driving module is used to generate an alternating electrical signal output. The zinc oxide film is covered on a cladding layer of an optical chip formed by integrating the silicon oxide microring resonator and the microring heater. The cladding is separated from the micro-ring heater so that the micro-ring heater is attached thereto. The interdigital transducer is attached to the zinc oxide film. The interdigital transducer is used to access the alternating electric signal output by the radio frequency driving module, and under the excitation of the alternating electric signal, a periodic surface acoustic wave is generated and transmitted to the silicon oxide micro-ring resonator, and the optical signal inside the silicon oxide micro-ring resonator is periodically interacted with to modulate the optical signal inside the silicon oxide micro-ring resonator. The modulated optical signal is output to the photoelectric conversion module. The photoelectric conversion module is used to convert the optical signal output by the silicon oxide micro-ring resonator to a voltage signal, and the voltage signal is output to the phase-locked amplifier module. The phase-locked amplifier module The first analog-to-digital conversion module is used to access the voltage signal output by the photoelectric conversion module and the alternating electric signal output by the radio frequency driving module, and coherently demodulate the accessed voltage signal and the alternating electric signal to obtain a voltage signal representing the spectrum information and spectrum slope information of the optical signal inside the silicon oxide microring resonator, and output it to the first analog-to-digital conversion module. The first analog-to-digital conversion module is used to periodically sample the voltage signal output by the phase-locked amplifier module, and each period of sampling obtains a sampling signal output to the feedback control module. The second analog-to-digital conversion module is used to access the voltage signal output by the photoelectric conversion module, and periodically sample the accessed voltage signal, and each period of sampling obtains a sampling signal. The sampling signal is output to the feedback control module, the sampling frequency of the second analog-to-digital conversion module is the same as that of the first analog-to-digital conversion module, the feedback control module is used to obtain the feedback control signal of each cycle according to the sampling signal outputted thereto by the first analog-to-digital conversion module and the second analog-to-digital conversion module in each cycle, and output it to the digital-to-analog conversion module, the digital-to-analog conversion module is used to perform digital-to-analog conversion on the feedback control signal of each cycle outputted thereto by the feedback control module, obtain the feedback control voltage and output it to the micro-ring heater, and adjust the thermal power of the micro-ring heater in real time, thereby adjusting the resonant wavelength of the silicon oxide micro-ring resonator, so that the optical signal outputted by the silicon oxide micro-ring resonator is locked at the target wavelength.

[0034] In this embodiment, the thickness of the zinc oxide film is 2.2 microns.

[0035] In this embodiment, when the alternating electric signal generated by the RF driving module is applied to the IDT, since the IDT is attached to the zinc oxide film, the zinc oxide film will generate mechanical vibration due to the electrostrictive effect, and a surface acoustic wave will be formed on its surface. When the surface acoustic wave propagates to the vicinity of the silicon oxide microring resonator, mechanical stress and strain will be induced, thereby changing the refractive index distribution of the silicon oxide microring resonator, and modulating the frequency, phase and intensity of the optical signal inside the resonator. In addition, the phase-locked amplifier module receives the voltage signal output by the photoelectric conversion module and the alternating electric signal output by the RF driving module, and phase-couples the received voltage signal with the alternating electric signal. Dry demodulation is performed to obtain a voltage signal representing the spectrum information and spectrum slope information of the optical signal inside the silicon oxide microring resonator. The first analog-to-digital conversion module and the second analog-to-digital converter respectively perform periodic real-time sampling on the voltage signal output by the phase-locked amplifier module and the voltage signal output by the photoelectric conversion module to obtain periodic sampling data. The feedback control module obtains an error signal based on the periodic sampling data obtained by the first analog-to-digital conversion module and the second analog-to-digital converter. The thermal power of the microring heater is adjusted based on the error signal feedback, and the resonant wavelength of the silicon oxide microring resonator is adjusted to lock the wavelength of the optical signal output by the silicon oxide microring resonator at the target wavelength.

[0036] It can be seen that, unlike the conventional wavelength locking system that uses conventional thermo-optical modulation and relies on the thermal conductivity of the material, the wavelength locking system of the present invention uses an acousto-optic modulation mechanism based on an interdigital transducer and a feedback mechanism implemented by a feedback control module to synchronously tune the resonant wavelength of the silicon oxide microring resonator, thereby avoiding dependence on the thermal conductivity of the material, overcoming the limitations of the wavelength locking system that uses conventional thermo-optical modulation and relies on the thermal conductivity of the material in the silicon oxide microring resonator, and can more quickly extract the error signal characterizing the current state of the silicon oxide microring resonator, has a faster response speed, has a strong real-time feedback capability, can efficiently and accurately lock the wavelength of the silicon oxide microring resonator to the target wavelength, and has a good wavelength locking effect on the silicon oxide microring resonator.

[0037] Embodiment 2: This embodiment is basically the same as Embodiment 1, except that: in this embodiment, the voltage signal output by the photoelectric conversion module is recorded as V0, the voltage signal output by the phase-locked amplifier module is recorded as V1, the sampling frequencies of the first analog-to-digital conversion module and the second analog-to-digital conversion module are the same, the sequence index of the sampling moments of the first analog-to-digital conversion module and the second analog-to-digital conversion module is recorded as n, n=1, 2, 3, ...; the sampling signal obtained by the second analog-to-digital conversion module at the nth sampling moment is recorded as V0[n], the sampling signal obtained by the first analog-to-digital conversion module at the nth sampling moment is recorded as V1[n], the feedback control signal at the nth sampling moment obtained by the feedback control module according to the sampling signal output by the first analog-to-digital conversion module and the second analog-to-digital conversion module at the nth sampling moment is recorded as Vheater[n]; the specific process of the feedback control module obtaining the feedback control signal Vheater[n] at the nth sampling moment according to the sampling signal output by the first analog-to-digital conversion module and the second analog-to-digital conversion module at the nth sampling moment is as follows:

[0038] Step 1: Set the feedback error signal at the nth sampling moment to Feedback[n] and the slope to k[n], and use formulas (1) and (2) to calculate Feedback[n] and k[n] respectively:

[0039] Feedback[n]=V1[n] / V0[n] (1)

[0040] k[n]={V1[n]-V1[n-1]} / {V0[n]-V0[n-1]} (2)

[0041] In formula (1), when n=1, V1[n-1]=0, V0[n-1]=0, when n≠1, V1[n-1] represents the sampling signal obtained by the first analog-to-digital conversion module at the n-1th sampling time, and V0[n-1] represents the sampling signal obtained by the second analog-to-digital conversion module at the n-1th sampling time;

[0042] Step 2: Determine Vheater[n] based on Feedback[n] and k[n], specifically:

[0043] If Feedback[n] is less than 0, and k[n] is less than or equal to 0, then Vheater[n] = Vheater[n-1] + 0.1;

[0044] If Feedback[n] is less than 0 and k[n] is greater than 0, then Vheater[n] = Vheater[n-1] + 0.01;

[0045] If Feedback[n] is greater than 0 and k[n] is greater than 0, then Vheater[n] = Vheater[n-1]-0.01;

[0046] If Feedback[n] is greater than 0, and k[n] is less than or equal to 0, then Vheater[n] = Vheater[n-1]-0.1;

[0047] If Feedback[n] is equal to 0, then directly set Vheater[n] = Vheater[n-1];

[0048] Among them, when n=1, Vheater[n-1]=0, when n≠1, Vheater[n-1] represents the feedback control signal at the n-1th sampling moment obtained by the feedback control module based on the sampling signal output to it by the first analog-to-digital conversion module and the second analog-to-digital conversion module at the n-1th sampling moment.

[0049] In this embodiment, during the operation of the wavelength locking system of the silicon oxide microring resonator, the optical signal generated by the external laser always exists and is output to the silicon oxide microring resonator, so the photoelectric conversion module can sense the optical signal, and the voltage signal V0 outputted by it is not 0, and the sampling signal V0[n] obtained by the second analog-to-digital conversion module sampling the voltage signal V0 at the nth sampling time will not be 0, that is, the situation that V0[n] is equal to 0 and cannot be calculated will not appear in formula (1). Secondly, before reaching the locked state (that is, when Feedback[n] is equal to 0), the feedback control signal input to the microring heater is always changing, and the feedback control signal at the current sampling time and the previous sampling time are different. The optical signal outputted by the silicon oxide microring resonator after being adjusted by the thermal power of the microring heater will also be different, that is, the voltage signals V0[n] and V0[n-1] outputted by the photoelectric conversion module are also different, so the situation that V0[n]-V0[n-1] is equal to 0 and cannot be calculated will not appear in formula (2). In actual use, if V0[n]=0 or V0[n]-V0[n-1]=0, it indicates that the wavelength locking system fails. At this time, the feedback control module will report an abnormal error and terminate the feedback control work.

[0050] In this embodiment, Feedback[n] calculated by dividing V1[n] by V0[n] is essentially a normalization of V1[n], which can eliminate the influence of the power change of the optical signal input from the laser (external light source) to the silicon oxide microring resonator on the wave field locking system, so that the feedback control of the wavelength locking system only depends on the signal ratio change obtained after the normalization of V1[n], and is not disturbed by the power fluctuation of the optical signal input from the laser (external light source) to the silicon oxide microring resonator, ensuring that the wavelength locking system maintains stable control performance. In addition, by introducing the slope k[n], the wavelength locking system can accurately distinguish the rising and falling sections of the feedback curve, avoiding the ambiguity caused by the non-monotonic feedback curve, and avoiding the multiple solutions caused by relying solely on the Feedback[n] threshold, ensuring that the adjustment direction of the feedback control signal Vheater[n] is unique. According to different combinations of Feedback[n] and k[n], the wavelength locking system adopts a segmented adjustment strategy. This design enables the wavelength locking system to respond specifically to different state changes, avoiding over-adjustment or under-adjustment, and improving the stability and accuracy of the wave field locking system.

[0051] Embodiment 3: This embodiment is basically the same as Embodiment 1, except that: in this embodiment, Figure 4 As shown, the photoelectric conversion module includes a photodiode D1, a first operational amplifier U1, a first resistor R1 and a first capacitor C1. The first operational amplifier U1 has a non-inverting end, an inverting end, an output end, a positive power supply end and a negative power supply end. The positive electrode of the photodiode D1 and the non-inverting end of the first operational amplifier U1 are both grounded, the negative electrode of the photodiode D1, the inverting end of the first operational amplifier U1, one end of the first resistor R1 and one end of the first capacitor C1 are connected, the positive power supply end of the first operational amplifier U1 is connected to a positive voltage VCC, the negative power supply end of the first operational amplifier U1 is connected to a negative voltage VEE, the output end of the first operational amplifier U1, the other end of the first resistor R1 and the other end of the first capacitor C1 are connected, and the connection end is the output end of the photoelectric conversion module. The photodiode D1 is used to receive the optical signal generated by the silicon oxide microring resonator under the excitation of the external optical signal, and the output end of the photoelectric conversion module is used to output a voltage signal.

[0052] In this embodiment, in the photoelectric conversion module, the photodiode D1 receives the optical signal generated by the silicon oxide microring resonator under the excitation of the external optical signal, and generates a corresponding current based on the optical signal and outputs it to the inverting end of the first operational amplifier U1. The first operational amplifier U1, the first resistor R1 and the first capacitor C1 constitute a transimpedance amplifier. The first resistor R1 serves as a feedback resistor, and the first capacitor C1 serves as a feedback capacitor. The first resistor R1 and the first capacitor C1 are connected in parallel to increase the stability and working bandwidth of the photoelectric conversion module. The voltage signal outputted from the output end of the first operational amplifier U1 is the product of the current generated by the photodiode D1 and the resistance value of the first resistor R1. Without affecting other performances, the first resistor R1 should be as large as possible to overcome the subsequent stage noise.

[0053] Embodiment 4: This embodiment is basically the same as Embodiment 1, except that: in this embodiment, Figure 5 As shown, the phase-locked amplifier module includes a multiplier and a low-pass filter. The multiplier includes a first chip U2 of model AD633, a second capacitor C2 and a second resistor R2. The X1 pin of the first chip U2 is respectively connected to one end of the second capacitor C2 and one end of the second resistor R2. The other end of the second resistor R2, the X2 pin, the Y2 pin and the Z pin of the first chip U2 are all grounded. The other end of the second capacitor C2 is the first input end of the multiplier, which is used to access the voltage signal output by the photoelectric conversion module. The Y1 pin of the first chip U2 is the second input end of the multiplier, which is used to access the alternating electric signal output by the radio frequency driving module. The W pin of the first chip U2 is the output end of the multiplier. The VS+ pin of the first chip U2 is connected to the positive power supply, and the VS- pin of the first chip U2 is connected to the negative power supply. The low-pass filter has an input end and an output end. The input end of the low-pass filter is connected to the output end of the multiplier, and the output end of the low-pass filter is used to output a voltage signal representing the spectrum information and spectrum slope information of the silicon oxide microring resonator.

[0054] In this embodiment, the low-pass filter includes a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7, an eighth capacitor C8, a ninth capacitor C9, a second operational amplifier U3, a third operational amplifier U4, a fourth operational amplifier U5 and a fifth operational amplifier U6, and the second operational amplifier U3, the third operational amplifier U4, the fourth operational amplifier U5 and the fifth operational amplifier U6 all have a non-inverting terminal, an inverting terminal, an input terminal, and a phase difference terminal. The output terminal, the positive power supply terminal and the negative power supply terminal of the second operational amplifier U3, the third operational amplifier U4, the fourth operational amplifier U5 and the fifth operational amplifier U6 are all connected to the positive voltage VCC, the negative power supply terminals of the second operational amplifier U3, the third operational amplifier U4, the fourth operational amplifier U5 and the fifth operational amplifier U6 are all connected to the negative voltage VEE, one end of the third resistor R3 is the input terminal of the low-pass filter, the other end of the third resistor R3 is respectively connected to one end of the fourth resistor R4 and one end of the fourth capacitor C4, the other end of the fourth resistor R4 is respectively connected to one end of the third capacitor C3 and the second operational amplifier The inverting end of the amplifier U3 is connected, the inverting end and the output end of the second operational amplifier U3, the other end of the fourth capacitor C4 and one end of the fifth resistor R5 are connected, the other end of the fifth resistor R5 is respectively connected to one end of the sixth resistor R6 and one end of the sixth capacitor C6, the other end of the sixth resistor R6 is respectively connected to one end of the fifth capacitor C5 and the inverting end of the third operational amplifier U4, the inverting end and the output end of the third operational amplifier U4, the other end of the sixth capacitor C6 and one end of the eighth resistor R8 are connected, and the other end of the eighth resistor R8 is respectively connected to one end of the seventh resistor R7 and one end of the eighth capacitor C8 The other end of the seventh resistor R7 is respectively connected to one end of the seventh capacitor C7 and the non-inverting end of the fourth operational amplifier U5, the inverting end and the output end of the fourth operational amplifier U5, the other end of the eighth capacitor C8 is connected to one end of the ninth resistor R9, the other end of the ninth resistor R9 is respectively connected to one end of the ninth capacitor C9 and the non-inverting end of the fifth operational amplifier U6, the inverting end and the output end of the fifth operational amplifier U6 are connected, and its connection end is the output end of the low-pass filter, the other end of the third capacitor C3, the other end of the fifth capacitor C5, the other end of the seventh capacitor C7 and the other end of the ninth capacitor C9 are all grounded.

[0055] In this embodiment, the multiplier uses the AD633 chip as the main body, and the second capacitor C2 is connected in series with the X1 pin of the AD633 chip as a DC blocking capacitor to isolate the DC component of the voltage signal output by the photoelectric conversion module. At the same time, the second resistor R2 is connected in parallel next to the DC blocking capacitor to form an RC high-pass filter with the DC blocking capacitor to avoid waveform distortion after the AD633 chip is connected in series with the DC blocking capacitor. The low-pass filter is implemented by a Butterworth type low-pass filter circuit, and the signal is processed by a multi-stage operational amplifier to improve the signal-to-noise ratio. At the same time, according to the use requirements, the third resistor R3, the fourth resistor R4, the fifth resistor R5, the sixth resistor R6, the seventh resistor R7, the eighth resistor R8, the ninth resistor R9, the third capacitor C3, the fourth capacitor C4, the fifth capacitor C5, the sixth capacitor C6, the seventh capacitor C7, the eighth capacitor C8 and the ninth capacitor C9 are selected with appropriate parameters to determine the cutoff frequency and gain of the low-pass filter.

[0056] In summary, the wavelength locking system of the silicon oxide microring resonator of the present invention adopts an acousto-optic modulation mechanism based on an interdigital transducer and a feedback mechanism realized by a feedback control module to synchronously tune the resonant wavelength of the silicon oxide microring resonator. When locking the wavelength of the silicon oxide microring resonator, it does not rely on the thermal conductivity of the material and is not limited by the low thermal conductivity efficiency of the silicon oxide material. It can extract the error signal characterizing the current state of the silicon oxide microring resonator more quickly, has a fast response speed, significantly improves the modulation rate and real-time feedback capability, and can efficiently and accurately lock the wavelength to the target wavelength. The wavelength locking system of the silicon oxide microring resonator of the present invention can be effectively used for wavelength locking of silicon oxide microring resonators, and has broad application prospects in the field of silicon oxide microring resonators.

Claims

1. A wavelength locking system for a silicon oxide microring resonator, comprising a photoelectric conversion module and a feedback control module, wherein the photoelectric conversion module is used to receive an optical signal output by the silicon oxide microring resonator and convert the optical signal into a voltage signal for output, characterized in that It also includes a radio frequency driving module, an interdigital transducer, a zinc oxide film for generating a piezoelectric effect, a phase-locked amplifier module, two analog-to-digital conversion modules and a digital-to-analog conversion module, wherein the two analog-to-digital conversion modules are respectively referred to as a first analog-to-digital conversion module and a second analog-to-digital conversion module; the radio frequency driving module is used to generate an alternating electrical signal output, the zinc oxide film is covered on the cladding of an optical chip formed by integrating a silicon oxide microring resonator and a microring heater, the cladding is separated from the microring heater, and the microring heater is attached thereto, the interdigital transducer is attached to the zinc oxide film, and the interdigital transducer is used to access the alternating electrical signal output by the radio frequency driving module , and under the excitation of the alternating electric signal, a periodic surface acoustic wave is generated and transmitted to the silicon oxide microring resonator, and the optical signal inside the silicon oxide microring resonator is periodically interacted, and the optical signal inside the silicon oxide microring resonator is modulated, and the modulated optical signal is output to the photoelectric conversion module, and the photoelectric conversion module is used to convert the optical signal output by the silicon oxide microring resonator to it into a voltage signal, and output the voltage signal to the phase-locked amplifier module, and the phase-locked amplifier module is used to access the voltage signal output by the photoelectric conversion module and the alternating electric signal output by the radio frequency drive module, and the voltage signal is connected to the photoelectric conversion module. The alternating electrical signal is coherently demodulated to obtain a voltage signal representing the spectrum information and spectrum slope information of the optical signal inside the silicon oxide microring resonator, which is output to the first analog-to-digital conversion module. The first analog-to-digital conversion module is used to periodically sample the voltage signal output to it by the phase-locked amplifier module, and each period of sampling obtains a sampling signal which is output to the feedback control module. The second analog-to-digital conversion module is used to access the voltage signal output by the photoelectric conversion module and periodically sample the accessed voltage signal, and each period of sampling obtains a sampling signal which is output to the feedback control module. The second analog-to-digital conversion module The sampling frequency is the same as that of the first analog-to-digital conversion module. The feedback control module is used to obtain the feedback control signal of each cycle according to the sampling signal outputted thereto by the first analog-to-digital conversion module and the second analog-to-digital conversion module in each cycle, and output it to the digital-to-analog conversion module. The digital-to-analog conversion module is used to perform digital-to-analog conversion on the feedback control signal of each cycle outputted thereto by the feedback control module, obtain the feedback control voltage and output it to the micro-ring heater, adjust the thermal power of the micro-ring heater in real time, and then adjust the resonant wavelength of the silicon oxide micro-ring resonator, so that the optical signal outputted by the silicon oxide micro-ring resonator is locked at the target wavelength.

2. A wavelength locking system for a silicon oxide microring resonator according to claim 1, characterized in that The voltage signal output by the photoelectric conversion module is recorded as V0, the voltage signal output by the phase-locked amplifier module is recorded as V1, the sampling frequencies of the first analog-to-digital conversion module and the second analog-to-digital conversion module are the same, the sequence index of the sampling moments of the first analog-to-digital conversion module and the second analog-to-digital conversion module is recorded as n, n=1, 2, 3, ...; the sampling signal obtained by the second analog-to-digital conversion module at the nth sampling moment is recorded as V0[n], the sampling signal obtained by the first analog-to-digital conversion module at the nth sampling moment is recorded as V1[n], the feedback control signal at the nth sampling moment obtained by the feedback control module according to the sampling signal output by the first analog-to-digital conversion module and the second analog-to-digital conversion module at the nth sampling moment is recorded as Vheater[n]; the specific process of the feedback control module obtaining the feedback control signal Vheater[n] at the nth sampling moment according to the sampling signal output by the first analog-to-digital conversion module and the second analog-to-digital conversion module at the nth sampling moment is as follows: Step 1: Set the feedback error signal at the nth sampling moment to Feedback[n] and the slope to k[n], and use formulas (1) and (2) to calculate Feedback[n] and k[n] respectively: Feedback[n]=V1[n] / V0[n] (1) k[n]={V1[n]-V1[n-1]} / {V0[n]-V0[n-1]} (2) In formula (1), when n=1, V1[n-1]=0, V0[n-1]=0, when n≠1, V1[n-1] represents the sampling signal obtained by the first analog-to-digital conversion module at the n-1th sampling time, and V0[n-1] represents the sampling signal obtained by the second analog-to-digital conversion module at the n-1th sampling time; Step 2: Determine Vheater[n] based on Feedback[n] and k[n], specifically: If Feedback[n] is less than 0, and k[n] is less than or equal to 0, then Vheater[n] = Vheater[n-1] + 0.1; If Feedback[n] is less than 0 and k[n] is greater than 0, then Vheater[n] = Vheater[n-1] + 0.01; If Feedback[n] is greater than 0 and k[n] is greater than 0, then Vheater[n] = Vheater[n-1]-0.01; If Feedback[n] is greater than 0, and k[n] is less than or equal to 0, then Vheater[n] = Vheater[n-1]-0.1; If Feedback[n] is equal to 0, then directly set Vheater[n] = Vheater[n-1]; Among them, when n=1, Vheater[n-1]=0, when n≠1, Vheater[n-1] represents the feedback control signal at the n-1th sampling moment obtained by the feedback control module based on the sampling signal output to it by the first analog-to-digital conversion module and the second analog-to-digital conversion module at the n-1th sampling moment.

3. The wavelength locking system of a silicon oxide microring resonator according to claim 1, characterized in that The photoelectric conversion module includes a photodiode, a first operational amplifier, a first resistor and a first capacitor. The first operational amplifier has a non-inverting end, an inverting end, an output end, a positive power supply end and a negative power supply end. The positive electrode of the photodiode and the non-inverting end of the first operational amplifier are both grounded. The negative electrode of the photodiode, the inverting end of the first operational amplifier, one end of the first resistor and one end of the first capacitor are connected. The positive power supply end of the first operational amplifier is connected to a positive voltage VCC, and the negative power supply end of the first operational amplifier is connected to a negative voltage VEE. The output end of the first operational amplifier, the other end of the first resistor and the other end of the first capacitor are connected, and the connection end is the output end of the photoelectric conversion module. The photodiode is used to receive the optical signal generated by the silicon oxide microring resonator under the excitation of an external optical signal. The output end of the photoelectric conversion module is used to output a voltage signal.

4. The wavelength locking system of a silicon oxide microring resonator according to claim 1, characterized in that The phase-locked amplifier module includes a multiplier and a low-pass filter. The multiplier includes a first chip of model AD633, a second capacitor and a second resistor. The X1 pin of the first chip is respectively connected to one end of the second capacitor and one end of the second resistor. The other end of the second resistor, the X2 pin, the Y2 pin and the Z pin of the first chip are all grounded. The other end of the second capacitor is the first input end of the multiplier, which is used to access the voltage signal output by the photoelectric conversion module. The Y1 pin of the first chip is the second input end of the multiplier, which is used to access the alternating electric signal output by the radio frequency driving module. The W pin of the first chip is the output end of the multiplier. The VS+ pin of the first chip is connected to a positive power supply, and the VS- pin of the first chip is connected to a negative power supply. The low-pass filter has an input end and an output end. The input end of the low-pass filter is connected to the output end of the multiplier, and the output end of the low-pass filter is used to output a voltage signal representing the spectrum information and spectrum slope information of the silicon oxide microring resonator.

5. A wavelength locking system for a silicon oxide microring resonator according to claim 4, characterized in that The low-pass filter includes a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a seventh capacitor, an eighth capacitor, a ninth capacitor, a second operational amplifier, a third operational amplifier, a fourth operational amplifier and a fifth operational amplifier. The second operational amplifier, the third operational amplifier, the fourth operational amplifier and the fifth operational amplifier all have a non-inverting terminal, an inverting terminal, an output terminal, a positive power supply terminal and a negative power supply terminal. The positive power supply terminals of the second operational amplifier, the third operational amplifier, the fourth operational amplifier and the fifth operational amplifier are all connected to a positive voltage VCC, and the negative power supply terminals of the second operational amplifier, the third operational amplifier, the fourth operational amplifier and the fifth operational amplifier are all connected to a negative voltage VEE. One end of the third resistor is the input end of the low-pass filter, and the other end of the third resistor is respectively connected to one end of the fourth resistor and one end of the fourth capacitor. The other end of the fourth resistor is respectively connected to one end of the third capacitor and the non-inverting terminal of the second operational amplifier. The inverting terminal of the second operational amplifier The inverting terminal and the output terminal of the third operational amplifier, the other end of the sixth capacitor and one end of the eighth resistor are connected, the other end of the eighth resistor is connected to one end of the seventh resistor and one end of the eighth capacitor, the other end of the seventh resistor is connected to one end of the seventh capacitor and the inverting terminal of the fourth operational amplifier, the inverting terminal and the output terminal of the fourth operational amplifier, the other end of the eighth capacitor is connected to one end of the seventh resistor and one end of the eighth capacitor, the other end of the seventh resistor is connected to one end of the seventh capacitor and the inverting terminal of the fourth operational amplifier, the inverting terminal and the output terminal of the fourth operational amplifier, the other end of the eighth capacitor is connected to one end of the ninth resistor, the other end of the ninth resistor is connected to one end of the ninth capacitor and the inverting terminal of the fifth operational amplifier, the inverting terminal and the output terminal of the fifth operational amplifier, and the connection end thereof is the output terminal of the low-pass filter, the other end of the third capacitor, the other end of the fifth capacitor, the other end of the seventh capacitor and the other end of the ninth capacitor are all grounded.

6. The wavelength locking system of a silicon oxide microring resonator according to claim 1, characterized in that The thickness of the zinc oxide film is 2.2 microns.

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