A microcavity multi-optical comb repetition frequency difference broadband tuning system and tuning method

Abstract

The application provides a kind of repeat frequency difference wideband tunable microcavity multi-optical comb system and repeat frequency tuning method, solve the existing microcavity soliton optical frequency comb repeat frequency and microcavity multi-optical comb system repeat frequency difference tuning difficult problem.The system and method adopt single pump or double pump scheme to generate multiple sets of microcavity soliton optical frequency comb, monitor the repeat frequency and repeat frequency difference of multiple sets of soliton optical frequency comb, based on the thermal light effect of microcavity, through a set of negative feedback system and temperature control module to control the temperature of microcavity, realize the change of microcavity free spectral range, and then realize the change of repeat frequency.The system and method can realize the rapid, efficient and flexible tuning of optical frequency comb repeat frequency, which has important significance for promoting the application of microcavity soliton optical frequency comb in precision measurement field.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of microcavity optical frequency comb, and particularly relates to a microcavity multi-optical comb repetition frequency difference wideband tuning system and a tuning method. BACKGROUND

[0002] Optical frequency comb (referred to as "light frequency comb" for short) promotes the development of the field of precision measurement with its excellent time-frequency characteristics. The light frequency comb generated based on traditional mode-locked lasers or electro-optical modulation generally has low repetition frequency, large volume and high price, which is not conducive to wide application. The emerging microcavity light frequency comb based on Kerr effect has the characteristics of high repetition frequency, light weight and easy on-chip integration, which can solve the difficulties faced by traditional light frequency comb and is expected to become the main technical solution for future light frequency comb generation.

[0003] Since the first wideband Kerr light frequency comb was realized in a microdisk cavity in 2007, domestic and foreign researchers have carried out a large amount of research work, developed various experimental techniques for generating soliton light frequency comb, and realized soliton light frequency comb on various material platforms, with wavelength range covering from visible light to mid-infrared band. With the development of microcavity soliton light frequency comb generation technology, application research based on microcavity soliton light frequency comb in coherent optical communication, optical frequency synthesis, quantum key distribution, precision ranging, double light comb spectrum and other aspects has also been carried out. As a branch of the application of microcavity soliton light frequency comb, the microcavity double light comb system provides many conveniences for high-speed precision ranging and precision spectrum measurement. For example: high-speed precision ranging by using double light comb time domain asynchronous sampling; non-blurred distance of double light comb dispersion interference ranging; gas sensing research by using double light comb; etc.

[0004] One problem existing in the above-mentioned double light comb system is that when two sets of soliton light frequency combs are generated, their repetition frequencies and repetition frequency differences are determined and do not change, and the repetition frequencies and repetition frequency differences are completely determined by process errors and are difficult to be flexibly controlled by humans. In the case that process errors are difficult to improve, in order to select appropriate repetition frequencies and repetition frequency differences, a large number of suitable microcavities need to be searched, which will lead to a very tedious process and randomness, which is not conducive to its practical application in precision measurement. Therefore, in order to realize the flexible application of microcavity soliton light frequency comb, a technical solution is needed to realize the flexible control of the repetition frequency and the repetition frequency difference. SUMMARY

[0005] The purpose of the present application is to solve the problem of difficult tuning of the repetition frequency of the existing microcavity soliton light frequency comb and the repetition frequency difference of the microcavity multi-optical comb system, and to provide a microcavity multi-optical comb repetition frequency difference wideband tuning system and a tuning method. The system and method can realize rapid, efficient and flexible tuning of the repetition frequency of the light frequency comb, which is of great significance to promote the application of microcavity soliton light frequency comb in the field of precision measurement.

[0006] To achieve the above object, the technical scheme adopted by the present application is:

[0007] A kind of microcavity multi-optical comb repeat frequency difference wideband tuning system, it is special in that: including microcavity soliton light frequency comb generation module, repeat frequency monitoring module, negative feedback module and temperature control module;

[0008] The microcavity soliton light frequency comb generation module includes at least two microcavity soliton light frequency comb generators, for generating soliton light frequency comb;

[0009] The output end of each microcavity soliton light frequency comb generator is divided into two ways, one of which is combined by polarization maintaining optical fiber and output, and the other is connected with the input end of the repeat frequency monitoring module;

[0010] The repeat frequency monitoring module is used to monitor the repeat frequency of each microcavity soliton light frequency comb generator output light frequency comb, and the repeat frequency difference of multiple light frequency combs;The output end of the repeat frequency monitoring module is connected with the input end of the negative feedback module;

[0011] The negative feedback module is used to compare the repeat frequency value and the repeat frequency difference value monitored by the repeat frequency monitoring module with the preset value, and output feedback signals after judgment and processing;The output end of the negative feedback module is connected with the input end of the temperature control module;

[0012] The temperature control module is used to heat or cool each microcavity soliton light frequency comb generator according to the feedback signal received from the negative feedback module, and simultaneously monitors the temperature of each microcavity soliton light frequency comb generator in real time, to realize the wideband tuning of the repeat frequency and the repeat frequency difference of the microcavity soliton light frequency comb.

[0013] Further, the microcavity soliton light frequency comb generator includes a pump laser, a first optical amplifier, a microcavity, an acousto-optic modulator, a second optical amplifier, and a radio frequency source for providing excitation radio frequency to the acousto-optic modulator;

[0014] The pump light output by the pump laser is divided into two ways, one of which is amplified by the first optical amplifier and enters the microcavity from the first coupling end of the microcavity straight waveguide;The other pump light is used as auxiliary light to maintain the thermal balance in the microcavity, and the auxiliary light is first frequency-shifted by the acousto-optic modulator and then incident to the second optical amplifier, and is amplified by the second optical amplifier and enters the microcavity from the second coupling end of the microcavity straight waveguide;

[0015] The microcavity soliton light frequency comb output by the microcavity soliton light frequency comb generator is again divided into two ways, one of which is combined by polarization maintaining optical fiber and output, for practical application of multi-optical comb;The other light frequency comb is connected with the repeat frequency monitoring module.

[0016] Further, the microcavity is a micro-ring cavity, a micro-disk cavity, a micro-sphere cavity, a rod cavity or a crystal cavity, has obvious thermal effect, and its free spectral range and resonance peak position can be tuned in a wide band by changing the temperature.

[0017] Further, the microcavity is an up-and-down channel micro-ring resonant cavity based on a high-refractive-index-difference doped glass photonic integrated platform, has a free spectral range of 48-50 GHz, and a quality factor greater than 2.0*10 6 A heat-conducting tungsten sheet is attached to the bottom of the microcavity chip.

[0018] Further, the pump laser is a wavelength-tunable narrow-line-width continuous laser, has a wavelength adjustment range of about 1 nm, which is greater than one free spectral range of the microcavity, and can excite the microcavity to generate a soliton optical frequency comb with a center wavelength of 1560 nm and a line width less than 1 kHz.

[0019] Further, the acousto-optic modulator is excited by a radio frequency source to provide an electrical signal with a frequency of 60-180 MHz, so as to realize auxiliary light frequency shift in the microcavity soliton optical frequency comb.

[0020] Further, the repetition frequency monitoring module comprises an optoelectronic detector and a repetition frequency monitor connected in sequence, the optical frequency comb first passes through the optoelectronic detector to convert the optical signal into an electrical signal, and the electrical signal is transmitted to the repetition frequency monitor for repetition frequency detection.

[0021] The optoelectronic detector is a commercial high-bandwidth optoelectronic detector, and the repetition frequency monitor can display and read data; the repetition frequency monitor is a spectrum analyzer, a frequency counter or an oscilloscope.

[0022] Further, the negative feedback module comprises an FPGA circuit or a computer program of the repetition frequency monitor, which is used for judging and processing the repetition frequency values and repetition frequency difference values of the multiple microcavity soliton optical frequency combs detected by the repetition frequency monitor, and giving a feedback signal to the temperature control module.

[0023] Further, the temperature control module comprises a temperature controller, a micro-heater and a thermistor; the input end of the temperature controller is connected with the output end of the negative feedback module, the output end of the temperature controller is connected with the micro-heater, and the temperature controller is used for controlling the micro-heater to work according to the received feedback signal; the micro-heater is located on the lower surface of the microcavity or contacts the heat-conducting tungsten sheet on the lower surface of the microcavity, and is used for heating or cooling the microcavity; the thermistor contacts the upper surface of the micro-heater and is located near the microcavity, and is used for monitoring the temperature of the microcavity in real time.

[0024] The micro-heater is a commercial semiconductor refrigerator, which can heat and cool the microcavity, and the temperature controller is a commercial temperature controller, which is used for monitoring the temperature of the micro-heater.

[0025] The application also provides a microcavity multi-optical comb repetition frequency difference wideband tuning method based on the above microcavity multi-optical comb repetition frequency difference wideband tuning system, which is characterized by comprising the following steps:

[0026] Step one, based on the auxiliary optical thermal compensation technology, each microcavity soliton optical frequency comb generation module generates a microcavity soliton optical frequency comb;

[0027] Step two, the repetition frequency monitoring module is used to monitor the repetition frequency and the repetition frequency difference of each microcavity soliton optical frequency comb, and transmit them to the negative feedback module;

[0028] Step three, the negative feedback module judges and processes the received repetition frequency and repetition frequency difference value, and obtains a feedback signal transmitted to the temperature control module;

[0029] Step four, the temperature control module changes the temperature of the corresponding microcavity according to the received feedback signal, so as to realize the wideband flexible tuning of the repetition frequency and the repetition frequency difference of the microcavity soliton optical frequency comb.

[0030] Compared with the prior art, the application has the following beneficial technical effects:

[0031] 1. The microcavity multi-optical comb repetition frequency difference wideband tuning system provided by the application realizes the change of the free spectral range of the microcavity and the change of the repetition frequency through temperature control of the microcavity by a negative feedback system based on the thermal effect (thermo-optic effect and thermal expansion effect) of the microcavity, and the repetition frequency tuning idea has strong universality and can realize wideband tuning of the repetition frequency.

[0032] 2. The microcavity multi-optical comb repetition frequency difference wideband tuning method provided by the application does not need to randomly search for a microcavity with matched repetition frequency and repetition frequency difference, and the repetition frequency and repetition frequency difference tuning process can be directly operated in the soliton state throughout the process without complicated processes such as terminating the soliton state, so that the repetition frequency of the soliton optical frequency comb can be quickly, efficiently, flexibly and widely tuned, which is conducive to promoting the engineering application of the microcavity soliton optical frequency comb in the field of precision measurement.

[0033] 3. The microcavity multi-optical comb repetition frequency difference wideband tuning method provided by the application is not limited to a specific microcavity soliton optical frequency comb generation technology, as long as the microcavity has obvious thermal effect, the idea of the application can be used for repetition frequency and repetition frequency difference tuning, and in addition, the cavity temperature can be changed by appropriately changing the pump power and the phase mismatch of the pump light and the microcavity resonance peak, and then the repetition frequency and the repetition frequency difference can be tuned. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 It is a structural schematic diagram of the microcavity double-optical comb repetition frequency difference wideband tuning system of the application.

[0035] Figure 2 A schematic diagram of the principle of the repetition frequency difference wideband tuning system of the microcavity dual optical comb of the present application;

[0036] Figure 3 A flow chart of the repetition frequency difference wideband tuning method of the microcavity dual optical comb of the present application;

[0037] Figure 4 A spectrum diagram of the single soliton state optical frequency comb generated by the tuning system in the embodiment of the present application;

[0038] Figure 5 A waterfall diagram of the microcavity resonance peak change with temperature by the tuning system in the embodiment of the present application;

[0039] Figure 6 A waterfall diagram of the repetition frequency change with temperature of the soliton state optical frequency comb after tuning by the tuning method in the embodiment of the present application;

[0040] Figure 7 A distribution diagram of the repetition frequency change with temperature of the soliton state optical frequency comb after tuning by the tuning method in the embodiment of the present application;

[0041] Reference signs:

[0042] 1-microcavity soliton optical frequency comb generation module, 2-repetition frequency monitoring module, 3-negative feedback module, 4-temperature control module, 5-polarization maintaining optical fiber, 6-radio frequency cable;

[0043] 11-pump laser, 12-first optical amplifier, 13-microcavity, 14-acousto-optic modulator, 15-second optical amplifier, 16-radio frequency source;

[0044] 21-optoelectronic detector, 22-repetition frequency monitor;

[0045] 41-temperature controller, 42-micro-heater, 43-thermistor. DETAILED DESCRIPTION

[0046] In order to make the purpose, advantages and characteristics of the present application clearer, the following will further describe a microcavity multi-comb repetition frequency difference wideband tuning system and tuning method in the present application in combination with the drawings and specific embodiments. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present application, and the purpose is not to limit the protection scope of the present application.

[0047] In view of the application value and prospect of the microcavity double optical comb in the field of precision spectroscopy and precision ranging, a microcavity multi-comb repetition frequency difference wideband tuning system and a tuning method are provided. The system and method generate multiple sets of microcavity soliton optical frequency combs by using single-pumping or double-pumping technology. The repetition frequency and the repetition frequency difference of the multiple sets of microcavity soliton optical frequency combs are monitored. The repetition frequency and the repetition frequency difference are judged and processed by using a negative feedback system. According to the comparison between the preset repetition frequency and the actual repetition frequency and the comparison between the preset repetition frequency difference and the actual repetition frequency difference, a feedback electrical signal is output. The feedback electrical signal is input to a temperature controller. The microcavity temperature is changed from 10 DEG C to 80 DEG C. The wideband continuous tuning of the microcavity repetition frequency of about 30 MHz is realized.

[0048] As shown in Figure 1 The microcavity double optical comb repetition frequency difference wideband tuning system provided by the embodiment comprises a microcavity soliton optical frequency comb generation module 1, a repetition frequency monitoring module 2, a negative feedback module 3 and a temperature control module 4.

[0049] The microcavity soliton optical frequency comb generation module 1 comprises two microcavity soliton optical frequency comb generators. The microcavity soliton optical frequency comb generators generate microcavity soliton optical frequency combs by using single-pumping or same-polarization double-pumping technology. The two output ends of the microcavity soliton optical frequency comb generators are both divided into two paths by an optical beam splitter. One path is combined by a polarization maintaining optical fiber 5 and output, which is used for the actual application of the double optical comb. The other path is connected with the repetition frequency monitoring module 2.

[0050] The repetition frequency monitoring module 2 is used for monitoring the repetition frequencies Frep1 and Frep2 of the output optical frequency combs of the two microcavity soliton optical frequency comb generators and the repetition frequency difference AFrep of the two optical frequency combs.

[0051] The negative feedback module 3 is used for receiving the repetition frequency value and the repetition frequency difference value monitored by the repetition frequency monitoring module 2. The measured repetition frequency and the repetition frequency difference are further compared with the preset values by using an FPGA circuit or a computer program. A feedback signal is output after the judgment and processing.

[0052] The temperature control module 4 is used for heating or cooling the microcavity according to the feedback signal sent by the negative feedback module 3. The temperature of the microcavity is monitored in real time by using a thermistor 43. The wideband flexible tuning of the repetition frequency and the repetition frequency difference of the microcavity soliton optical frequency comb is realized.

[0053] In the whole system as shown in Figure 1 The microcavity soliton optical frequency comb generation module 1 and the repetition frequency monitoring module 2 and the double optical frequency output end of the microcavity soliton optical frequency comb generation module 1 are connected by using a polarization maintaining optical fiber 5 (solid line). The electrical devices involved in the repetition frequency monitoring module 2, the negative feedback module 3 and the temperature control module 4 are connected by using a radio frequency cable 6 (dashed line).

[0054] As shown in the figure, in this embodiment, the microcavity soliton optical frequency comb generation module 1 adopts auxiliary optical thermal compensation technology to generate the microcavity soliton optical frequency comb. Figure 2

[0055] The microcavity soliton optical frequency comb generator of the microcavity soliton optical frequency comb generation module adopts a double-pumping structure, including a pump laser 11, a first optical amplifier 12, a microcavity 13, an acousto-optic modulator 14, a second optical amplifier 15, and a radio frequency source 16 for providing excitation radio frequency to the acousto-optic modulator 14.

[0056] The pump light output by the pump laser 11 is divided into two paths, one of which is amplified by the first optical amplifier 12 and then enters the microcavity from the first coupling end of the straight waveguide on the microcavity 13; the other pump light is used as auxiliary light to maintain the thermal balance in the microcavity 13, and the auxiliary light is first frequency-shifted by the acousto-optic modulator 14 and then enters the second optical amplifier 15, and then enters the microcavity from the second coupling end of the straight waveguide on the microcavity 13 after being amplified by the second optical amplifier 15.

[0057] The microcavity 13 has strong nonlinear optical effects, as the detuning of the in-cavity pump light with respect to the resonance peak of the microcavity 13 gradually decreases, the in-cavity optical power gradually increases, meeting the conditions for four-wave mixing to occur, and the in-cavity cascaded four-wave mixing is excited. The main role of the auxiliary light is to provide thermal compensation and maintain the thermal balance in the cavity. When the pump light wavelength and the auxiliary light wavelength are at the red detuning and blue detuning of the microcavity resonance peak, respectively, the microcavity soliton optical frequency comb output is realized.

[0058] In this embodiment, the pump laser 11 is a wavelength-tunable narrow-line-width continuous laser, and its wavelength adjustment range is about 1 nm, which is larger than one free spectral range of the microcavity, and can excite the microcavity to generate a soliton optical frequency comb with a center wavelength near 1560 nm and a line width less than 1 kHz.

[0059] The microcavity 13 can be a micro-ring cavity, a micro-disk cavity, a micro-sphere cavity, a rod cavity, or a crystal cavity, and has obvious thermal effects (thermal-optical effects and thermal expansion effects), and can perform wideband tuning on its free spectral range and resonance peak position by changing the microcavity temperature. The microcavity 13 in the microcavity soliton optical frequency comb generator is prepared by the same process, and there is a small difference in its free spectral range, which is caused by process errors. In this embodiment, the microcavity 13 is an up-and-down channel micro-ring resonant cavity based on a high-refractive-index-difference doped glass photonic integrated platform, and its free spectral range is about 48-50 GHz, and the quality factor is greater than 2.0×10 6 The free spectral range of the microcavity 13 determines the repetition frequency of the microcavity soliton optical frequency comb, and the repetition frequency and repetition frequency difference of the microcavity soliton optical frequency comb can be tuned by changing the free spectral range.

[0060] ​In this embodiment, the acousto-optic modulator 14 can provide an electrical signal of about 100 MHz (60-180 MHz) after being excited by the radio frequency source 16, realizing the auxiliary light frequency shift in the microcavity soliton optical frequency comb.

[0061] The microcavity soliton optical frequency comb output by the microcavity soliton optical frequency comb generator is again divided into two paths, one of which is combined by the polarization maintaining fiber 5 and output for actual application of the dual optical comb; the other optical frequency comb is connected with the repetition frequency monitoring module 2.

[0062] The repetition frequency monitoring module 2 includes a photodetector 21 and a repetition frequency monitor 22 connected in sequence. The optical frequency comb first passes through the photodetector 21 to convert the optical signal into an electrical signal, and the electrical signal is transmitted to the repetition frequency monitor 22 for repetition frequency detection.

[0063] The repetition frequency monitor 22 detects the repetition frequencies Frep1 and Frep2 of the two optical frequency combs output by the microcavity soliton optical frequency comb generator, as well as the repetition frequency difference AFrep of the two, and transmits the three frequency values to the negative feedback module 3.

[0064] The repetition frequency monitor 22 can be a spectrum analyzer, a frequency counter, or an oscilloscope. In this embodiment, a spectrum analyzer is used. The photodetector 21 is a commercial high-bandwidth photodetector, which can be displayed and data read by a spectrum analyzer, a frequency counter, and an oscilloscope.

[0065] The negative feedback module 3 includes a negative feedback system connected with the repetition frequency monitor 22. The negative feedback system is an FPGA circuit or a computer program, which is used to judge and process the repetition frequency values and the repetition frequency difference values of the two microcavity soliton optical frequency combs detected by the repetition frequency monitor 22, and give a feedback signal transmitted to the temperature control module 4.

[0066] The temperature control module 4 includes a temperature controller 41, a micro-heater 42, and a thermistor 43 connected in sequence. Two control ends of the temperature controller 41 are connected with the negative feedback system and the micro-heater 42 respectively, for controlling the micro-heater 42 according to the feedback signal output by the negative feedback system. The micro-heater 42 is in contact with or beside the heat-conducting tungsten sheet under the microcavity 13 chip, for heating or cooling the microcavity 13. The thermistor 43 is in contact with the upper surface of the micro-heater 42 and located near the microcavity 13, for monitoring the microcavity temperature in real time, so as to realize the wideband flexible tuning of the repetition frequency and the repetition frequency difference of the microcavity soliton optical frequency comb.

[0067] The micro-heater 42 is a commercial semiconductor refrigerator, which can heat and cool the microcavity. The temperature controller 41 is a commercial temperature controller, which is used to monitor the temperature of the micro-heater 42.

[0068] As Figure 3As shown, the method for wideband tuning of the repetition frequency difference of the microcavity dual optical comb provided by the present application comprises the following steps:

[0069] Step one, based on the auxiliary optical thermal compensation technology, the microcavity soliton optical frequency comb generation module 1 generates a microcavity soliton optical frequency comb;

[0070] The microcavity soliton optical frequency comb generation module 1 comprises two microcavity soliton optical frequency comb generators;

[0071] Step two, the repetition frequency monitor 22 monitors the repetition frequency and the repetition frequency difference of the microcavity soliton optical frequency comb and transmits them to the negative feedback module 3;

[0072] Step three, the negative feedback module 3 judges and processes the received repetition frequency and repetition frequency difference value to obtain a feedback signal transmitted to the temperature control module 4;

[0073] Step four, the temperature controller 41 changes the temperature of the microcavity 13 by changing the current or voltage of the micro-heater 42 according to the received feedback signal, so as to realize the wideband flexible tuning of the repetition frequency and the repetition frequency difference of the microcavity soliton optical frequency comb.

[0074] In the above method, the generation of the microcavity soliton optical frequency comb is not limited to a specific scheme. As long as the microcavity has obvious thermal effect, the idea of the present application can be used for tuning the repetition frequency and the repetition frequency difference. In addition, by appropriately changing the pump power and the phase detuning of the pump light and the microcavity resonance peak, the temperature in the cavity can be changed, and then the repetition frequency and the repetition frequency difference can be tuned.

[0075] In this embodiment, in order to characterize the formation of the soliton state, Figure 4 The generated single soliton state optical frequency comb spectrum is given, the center wavelength is about 1560 nm, the spectral width is greater than 100 nm, and the spectral envelope is approximately a perfect hyperbolic secant function shape.

[0076] In order to characterize the thermal effect of the microcavity, Figure 5 The waterfall plot of the microcavity resonance peak changing with temperature is given. When the temperature changes from 10℃ to 125℃ at an interval of 5℃, the microcavity resonance peak moves to the long wavelength by about 1.7nm, which is more than 4 times the free spectral range (about 0.4nm).

[0077] In order to illustrate the tuning effect of the repetition frequency, Figure 6 The waterfall plot of the repetition frequency changing with temperature after the generation of the soliton state optical frequency comb is given. When the temperature changes from 10℃ to 80℃ at an interval of 5℃, the repetition frequency decreases by about 30MHz, and the tuning rate is approximately constant. If the temperature range changes more in other embodiments, the repetition frequency can be tuned in a wider range.

[0078] To further illustrate the tuning effect of the repetition frequency, Figure 7 The distribution diagrams of the repetition frequency of the soliton optical frequency comb generated by 7 different microcavities with the change of temperature are given, and it can be seen that the repetition frequencies of the soliton optical frequency comb generated by different microcavities are different, and the maximum repetition frequency difference is about 70 MHz. In addition, the repetition frequencies of all microcavity soliton optical frequency combs change at approximately the same rate with the change of temperature, about 0.43 MHz / ℃. If the temperature range changes more in other embodiments, the repetition frequencies of most microcavity soliton optical frequency combs can be tuned to the same size by temperature, the repetition frequency difference can change from zero to the order of tens of MHz, realizing wideband tuning, which is of great significance to promote the application of microcavity soliton optical frequency comb in the field of precision measurement.

[0079] In summary, the present application provides a microcavity multi-optical comb system with wideband tunable repetition frequency difference and a repetition frequency tuning method, the core of which is to provide a microcavity soliton optical frequency comb repetition frequency tuning idea, to change the temperature of the microcavity through a negative feedback system, and thus to change the repetition frequency of the microcavity soliton optical frequency comb by using the thermal effect of the microcavity. The present application overcomes the problem that the repetition frequency is random and difficult to tune due to process errors, so that the repetition frequency of the soliton optical frequency comb can be quickly, efficiently, flexibly and widely tuned, which is of great significance to promote the engineering application of microcavity soliton optical frequency comb in the field of precision measurement.

[0080] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the present application.

Claims

1. A microcavity multi-optical comb repetition frequency difference wideband tuning system, characterized in that: The system comprises a microcavity soliton optical frequency comb generation module (1), a repetition frequency monitoring module (2), a negative feedback module (3) and a temperature control module (4). The microcavity soliton optical frequency comb generation module (1) comprises at least two microcavity soliton optical frequency comb generators for generating soliton optical frequency combs. The output end of each microcavity soliton optical frequency comb generator is divided into two paths, one of which is combined by a polarization maintaining optical fiber (5) and output, and the other is connected with the input end of the repetition frequency monitoring module (2). The repetition frequency monitoring module (2) is used for monitoring the repetition frequency of the optical frequency comb output by each microcavity soliton optical frequency comb generator and the repetition frequency difference of the multiple optical frequency combs, and the output end of the repetition frequency monitoring module (2) is connected with the input end of the negative feedback module (3). The negative feedback module (3) is used for comparing the repetition frequency value and the repetition frequency difference value monitored by the repetition frequency monitoring module (2) with preset values, judging and processing, and outputting feedback signals, and the output end of the negative feedback module (3) is connected with the input end of the temperature control module (4). The temperature control module (4) is used for heating or cooling each microcavity soliton optical frequency comb generator according to the feedback signals received from the negative feedback module (3), and simultaneously monitoring the temperature of each microcavity soliton optical frequency comb generator in real time to realize the wideband tuning of the repetition frequency and the repetition frequency difference of the microcavity soliton optical frequency comb.

2. The system according to claim 1, wherein the microcavity soliton optical frequency comb generator comprises a pump laser (11), a first optical amplifier (12), a microcavity (13), an acousto-optic modulator (14), a second optical amplifier (15), and a radio frequency source (16) for providing excitation radio frequency to the acousto-optic modulator (14). The pump light output by the pump laser (11) is divided into two paths, one of which is amplified by the first optical amplifier (12) and enters the microcavity (13) from the first coupling end of the microcavity (13) straight waveguide, and the other is auxiliary light which is frequency shifted by the acousto-optic modulator (14) and then enters the microcavity (13) from the second coupling end of the microcavity (13) straight waveguide after being amplified by the second optical amplifier (15). The microcavity soliton optical frequency comb output by the microcavity (13) is again divided into two paths, one of which is combined by a polarization maintaining optical fiber (5) and output for practical application of multiple optical combs, and the other is connected with the input end of the repetition frequency monitoring module (2).

3. The system according to claim 2, wherein the microcavity (13) is a micro-ring cavity, a micro-disk cavity, a micro-sphere cavity, a rod cavity or a crystal cavity, and the microcavity (13) has a thermal effect, and the free spectral range and the resonance peak position thereof can be wideband tuned by changing the temperature.

4. The system according to claim 3, wherein the temperature control module (4) comprises a temperature controller (21) and a temperature sensor (22).

5. The system according to claim 4, wherein the temperature controller (21) comprises a heating device (211) and a cooling device (212). ​ The microcavity (13) is an up-and-down channel micro-ring resonant cavity prepared based on a high-refractive-index-difference doped glass photonic integrated platform, has a free spectral range of 48-50 GHz, and a quality factor greater than 2.0x10 6 A heat-conducting tungsten sheet is attached to the lower surface of the microcavity (13). ​ The pump laser (11) is a wavelength tunable narrow linewidth continuous laser, the wavelength adjustment range of which is greater than the free spectral range of the microcavity (13), the center wavelength of which is 1560 nm, and the linewidth of which is less than 1 kHz.

6. The system according to claim 5, wherein the system is characterized in that: The frequency of the acousto-optic modulator (14) is 60-180 MHz, and the acousto-optic modulator (14) is used to realize auxiliary light frequency shift in the microcavity soliton optical frequency comb.

7. The system according to any one of claims 2-6, wherein the system is characterized in that: The repetition frequency monitoring module (2) comprises a photoelectric detector (21) and a repetition frequency monitor (22) connected in sequence, the microcavity soliton optical frequency comb output by the microcavity (13) is converted into an electrical signal by the photoelectric detector (21), and the electrical signal is transmitted to the repetition frequency monitor (22) for display and data reading; The photoelectric detector (21) is a high-bandwidth photoelectric detector, and the repetition frequency monitor (22) is a spectrum analyzer, a frequency counter or an oscilloscope.

8. The system according to claim 7, wherein the system is characterized in that: The negative feedback module (3) comprises an FPGA circuit or a computer program.

9. The system according to claim 8, wherein the system is characterized in that: The temperature control module (4) comprises a temperature controller (41), a micro-heater (42) and a thermistor (43); the input end of the temperature controller (41) is connected with the output end of the negative feedback module (3), the output end of the temperature controller (41) is connected with the micro-heater (42), and the temperature controller (41) is used to control the operation of the micro-heater (42) according to the received feedback signal; the micro-heater (42) is located on the lower surface of the microcavity (13) or in contact with the heat-conducting tungsten sheet on the lower surface of the microcavity (13), and is used to heat or cool the microcavity (13); the thermistor (43) is in contact with the upper surface of the micro-heater (42), and is used to monitor the temperature of the microcavity (13) in real time; The micro-heater (42) is a semiconductor refrigerator, which can heat and cool the microcavity, and the temperature controller (41) is used to monitor the temperature of the micro-heater (42).

10. A method for wideband tuning of the repetition rate difference of a microcavity multi-comb, based on the wideband tuning system of the repetition rate difference of a microcavity multi-comb according to any one of claims 1-9, characterized in that, The method comprises the following steps: Step one, based on the auxiliary light thermal compensation technology, the microcavity soliton optical frequency comb is generated by the microcavity soliton optical frequency comb generation module (1); Step two, the repetition frequency and the repetition frequency difference of each microcavity soliton optical frequency comb are monitored by the repetition frequency monitoring module (2), and are transmitted to the negative feedback module (3); Step three, the received repetition frequency and repetition frequency difference are judged and processed by the negative feedback module (3), and the feedback signal is transmitted to the temperature control module (4); Step four, the temperature control module (4) changes the temperature of the corresponding microcavity (13) according to the received feedback signal, so as to realize the wideband flexible tuning of the repetition frequency and the repetition frequency difference of the microcavity soliton optical frequency comb.

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