Optical frequency comb frequency control system and control method thereof

Abstract

The present application relates to an optical frequency comb frequency control system and a control method thereof, wherein the control system comprises: a laser generator, which is used to generate a narrowband optical frequency comb signal and inject it into a multi-longitudinal mode laser via a first optical circulator and an optical coupler; a multi-longitudinal mode laser, which is used to generate a multi-longitudinal mode laser signal and receive a narrowband optical frequency comb signal to generate an initial broadband optical frequency comb signal and output it to the optical coupler; an optical coupler, which is used to divide a part of the initial broadband optical frequency comb signal and output it to a feedback modulator; a feedback modulator is used to perform phase modulation, obtain a phase modulated feedback signal and inject it into the multi-longitudinal mode laser, so that the multi-longitudinal mode laser modulates the generated current broadband optical frequency comb signal based on the phase modulated feedback signal to obtain a target broadband optical frequency comb signal, a part of the target broadband optical frequency comb signal is input into the feedback modulator, and the other part is output to the control system; the present application can expand the comb teeth of the optical frequency comb to adapt to different application scenarios, and the signal is stable.

Description

Technical Field

[0001] The present application relates to the field of laser control technology, and in particular to an optical frequency comb frequency control system and a control method thereof. Background Art

[0002] Optical frequency combs have become an indispensable key module in the development of new spectrometers, lidar, and next-generation optical communications due to their comb teeth coherence and wide spectral coverage. Based on photonic integration technology, optical frequency combs have the ability to generate spectrums covering the visible to THz range and are developing in the direction of high compactness, low cost, and low power consumption. However, current optical frequency combs need to weigh design parameters when facing different application scenarios.

[0003] In order to obtain broadband spectral coverage, it is usually necessary to reduce the frequency adjustment range of the comb teeth. In some specific applications, in order to obtain octave-level spectral coverage, the adjustable characteristics of the frequency teeth are directly sacrificed. This means that the optical frequency comb tends to be optimized for a specific frequency adjustment range for different applications.

[0004] The frequency characteristics of the optical frequency comb require precise control and adjustment. The spacing between the comb teeth is the spectral free path of the optical frequency comb, and its special tuning characteristics are an important indicator of the bandwidth of the communication network; the central wavelength of the optical frequency comb is crucial for precision spectroscopy applications; and the frequency domain distribution characteristics of the optical frequency comb, especially the adjustment of the comb teeth amplitude, are extremely important for the energy and spectral characteristics of the generated THz radiation; at the same time, the maintenance of the coherence of the frequency teeth and the relative phase relationship between the comb teeth after frequency conversion restrict the accuracy and resolution of lidar and laser sensing.

[0005] At present, the method of adjusting the spectral characteristics of the optical frequency comb mainly relies on various types of filters, based on the wide-spectrum optical frequency comb, combined with active or passive spectrum control methods to achieve the desired frequency characteristics. However, optical filters are affected by bandwidth limitations, and center frequency control requires complex design, which hinders photonic integration. More importantly, after filtering the optical frequency comb, the power of the frequency teeth is difficult to maintain. Another way to expand the frequency characteristics of the optical frequency comb is to use nonlinear effects to perform frequency conversion, which can flexibly convert wavelengths, but is limited by the threshold characteristics of nonlinear effects and usually has low conversion efficiency.

[0006] To overcome these problems, a variety of technologies are currently used in a hybrid manner to achieve precise frequency characteristic control, such as the use of electro-optic frequency combs combined with nonlinear frequency changes or micro-resonant cavities, which are achieved through cascade filtering and frequency conversion, but this in turn increases the complexity of the system. Summary of the invention

[0007] Based on the above description, the present application provides an optical frequency comb frequency control system and a control method thereof to solve the problem that the frequency of the optical frequency comb is difficult to efficiently adjust in different application scenarios.

[0008] According to a first aspect, the present application provides an optical frequency comb frequency control system, comprising: a laser generator, a first optical circulator, an optical coupler, a multi-longitudinal mode laser, and a feedback modulator;

[0009] The laser generator is used to generate a narrowband optical frequency comb signal and output it to the first optical circulator;

[0010] The first optical circulator is used to inject the narrowband optical frequency comb signal into the multi-longitudinal mode laser via the optical coupler;

[0011] The multi-longitudinal mode laser is used to generate a multi-longitudinal mode laser signal, and according to the multi-longitudinal mode laser signal and the self-injected narrow-band optical frequency comb signal, an initial broadband optical frequency comb signal is generated and output to the optical coupler;

[0012] The optical coupler is used to output a part of the initial broadband optical frequency comb signal to the feedback modulator, and output another part of the initial broadband optical frequency comb signal to the control system via the first optical circulator;

[0013] The feedback modulator is used to phase-modulate a portion of the initial broadband optical frequency comb signal to obtain a phase-modulated feedback signal and inject it into the multi-longitudinal mode laser through an optical coupler, so that the multi-longitudinal mode laser modulates the current broadband optical frequency comb signal generated in real time based on the self-injected phase-modulated feedback signal to obtain a target broadband optical frequency comb signal;

[0014] Part of the target broadband optical frequency comb signal is output to the feedback modulator via the optical coupler, and another part of the target broadband optical frequency comb signal is output to the control system via the optical coupler and the first optical circulator.

[0015] In one or more embodiments, the feedback modulator includes a second optical circulator, a first phase modulator, a first optical amplifier, and an optical delay device;

[0016] The second optical circulator is used to receive a portion of the initial broadband optical frequency comb signal and input it to the first phase modulator;

[0017] The first phase modulator is used to modulate the phase of a portion of the initial broadband optical frequency comb signal based on the cavity mode phase of the multi-longitudinal mode laser to obtain a first modulated feedback signal and output it to the first optical amplifier;

[0018] The first optical amplifier is used to adjust the amplitude of the first modulated feedback signal based on the cavity mode amplitude of the multi-longitudinal mode laser to obtain a second modulated feedback signal and output it to the optical delay device;

[0019] The optical delay device is used to adjust the delay amount of the second modulated feedback signal relative to a portion of the initial broadband optical frequency comb signal to obtain the phase modulated feedback signal and output it to the multi-longitudinal mode laser through the second optical circulator and the optical coupler.

[0020] In one or more embodiments, the first phase modulator is used to modulate the phase of a portion of the initial broadband optical frequency comb signal to be consistent with the cavity mode phase of the multi-longitudinal mode laser.

[0021] In one or more embodiments, it further includes: a second optical amplifier, used to amplify the narrowband optical frequency comb signal generated by the laser generator, and output the amplified narrowband optical frequency comb signal to the first optical circulator.

[0022] In one or more embodiments, the second optical amplifier is configured as a fiber amplifier, a semiconductor amplifier, or a solid-state amplifier.

[0023] In one or more embodiments, the laser generator includes a continuous laser and a joint modulator;

[0024] The continuous laser is used to generate an initial ultrashort pulse laser signal, and output the initial ultrashort pulse laser signal to the joint modulator;

[0025] The joint modulator is used to perform phase modulation and intensity modulation on the initial ultrashort pulse laser signal to obtain the narrowband optical frequency comb signal.

[0026] In one or more embodiments, the joint modulator includes a second phase modulator and an intensity modulator, the second phase modulator is used to perform phase modulation on the ultrashort pulse laser signal, and the intensity modulator is used to perform intensity modulation on the phase-modulated ultrashort pulse laser signal to output a narrowband optical frequency comb signal.

[0027] According to a second aspect, the present application provides a control method for an optical frequency comb frequency control system, comprising:

[0028] Acquire a narrowband optical frequency comb signal, transmit and inject the narrowband optical frequency comb signal into a multi-longitudinal mode laser;

[0029] Generate a multi-longitudinal mode laser signal by the multi-longitudinal mode laser, and generate an initial broadband optical frequency comb signal according to the multi-longitudinal mode laser signal and the self-injected narrowband optical frequency comb signal;

[0030] Outputting a portion of the initial broadband optical frequency comb signal to a feedback modulator, and outputting another portion of the initial broadband optical frequency comb signal to a control system;

[0031] Phase modulating a portion of the initial broadband optical frequency comb signal through the feedback modulator to obtain a phase modulated feedback signal and injecting it into the multi-longitudinal mode laser;

[0032] Based on the self-injected phase modulation feedback signal, modulate the current broadband optical frequency comb signal generated in real time by the multi-longitudinal mode laser to obtain a target broadband optical frequency comb signal;

[0033] Part of the target broadband optical frequency comb signal is output to the feedback modulator, and another part of the target broadband optical frequency comb signal is output to the control system.

[0034] In one or more embodiments, phase modulating a portion of the initial broadband optical frequency comb signal by the feedback modulator to obtain a phase modulated feedback signal includes:

[0035] Based on the cavity mode phase of the multi-longitudinal mode laser, modulating the phase of a portion of the initial broadband optical frequency comb signal by a first phase modulator to obtain a first modulated feedback signal;

[0036] Based on the cavity mode amplitude of the multi-longitudinal mode laser, adjusting the amplitude of the first modulated feedback signal through a first optical amplifier to obtain a second modulated feedback signal;

[0037] The delay amount of the second modulated feedback signal relative to a portion of the initial broadband optical frequency comb signal is adjusted to obtain the phase modulated feedback signal.

[0038] In one or more embodiments, before the narrowband optical frequency comb signal is injected into the multi-longitudinal mode laser, it also includes: amplifying the narrowband optical frequency comb signal so that the amplified narrowband optical frequency comb signal is output to the multi-longitudinal mode laser.

[0039] The technical solution of this application has the following beneficial technical effects:

[0040] In the present application, a narrowband optical frequency comb signal is generated by a laser generator and transmitted through a first optical circulator and an optical coupler to be injected into a multi-longitudinal mode laser. Interference occurs between the narrowband optical frequency comb signal and the multi-longitudinal mode laser signal generated by the multi-longitudinal mode laser, new comb teeth are expanded, and an initial broadband optical frequency comb signal is generated. The initial broadband optical frequency comb signal is divided by an optical coupler so that a part of the initial broadband optical frequency comb signal is output to a feedback modulator. A part of the initial broadband optical frequency comb signal is phase-modulated by the feedback modulator to obtain a phase-modulated feedback signal and inject it into the multi-longitudinal mode laser, so that the multi-longitudinal mode laser modulates the current broadband optical frequency comb signal generated in real time based on the self-injected phase-modulated feedback signal to obtain a stable target broadband optical frequency comb signal, improve the coherence of the newly generated comb teeth, and compress the line width of the comb teeth. A part of the target broadband optical frequency comb signal is output to the feedback modulator through the optical coupler for continuous modulation and feedback, and another part of the target broadband optical frequency comb signal is output to the control system through the optical coupler and the first optical circulator. In this way, during the continuous operation of the control system, the frequency comb teeth are expanded based on the narrowband optical frequency comb signal through the multi-longitudinal mode laser, so that the optical frequency comb signal can be suitable for different application scenarios. At the same time, through the phase modulation effect of the feedback modulator, the target broadband optical frequency comb signal output by the control system is stable and available, thereby efficiently adjusting the optical frequency comb frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A principle block diagram of an optical frequency comb frequency control system provided in one embodiment of the present application;

[0042] Figure 2 A schematic diagram of a spectrum of a narrow-band optical frequency comb signal in one embodiment of the present application;

[0043] Figure 3 A schematic diagram of a spectrum of a multi-longitudinal mode laser signal in an embodiment of the present application;

[0044] Figure 4 A schematic diagram of the spectrum of an initial broadband optical frequency comb signal in an embodiment of the present application;

[0045] Figure 5 A schematic diagram of a single comb tooth of an initial broadband optical frequency comb signal in an embodiment of the present application;

[0046] Figure 6 A schematic diagram of a single comb tooth of a target broadband optical frequency comb signal in an embodiment of the present application;

[0047] Figure 7 This is a principle block diagram of a feedback modulator in one embodiment of the present application;

[0048] Figure 8 A principle block diagram of an optical frequency comb frequency control system provided by another embodiment of the present application;

[0049] Fig. 9 A flow chart of a control method of an optical frequency comb frequency control system provided by one embodiment of the present application;

[0050] Fig.10 This is a flowchart of step S104 in a control method of an optical frequency comb frequency control system provided in one embodiment of the present application. DETAILED DESCRIPTION

[0051] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0052] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0053] Figure 1 A principle block diagram of an optical frequency comb frequency control system provided by an embodiment of the present application is shown; Figure 2 A schematic diagram of the spectrum of a narrowband optical frequency comb signal in an embodiment of the present application is shown; Figure 3 A schematic diagram of the spectrum of a multi-longitudinal mode laser signal in an embodiment of the present application is shown; Figure 4 A schematic diagram of the spectrum of an initial broadband optical frequency comb signal in an embodiment of the present application is shown.

[0054] See also Figures 1 to 4An optical frequency comb frequency control system provided by an embodiment of the present application includes a laser generator 101, a first optical circulator 102, an optical coupler 103, a multi-longitudinal mode laser 104 and a feedback modulator 105; the laser generator 101 is used to generate a narrowband optical frequency comb signal and output it to the first optical circulator 102; the first optical circulator 102 is used to inject the narrowband optical frequency comb signal into the multi-longitudinal mode laser 104 through the optical coupler 103; the multi-longitudinal mode laser 104 is used to generate a multi-longitudinal mode laser signal, and generate an initial broadband optical frequency comb signal according to the multi-longitudinal mode laser signal and the self-injected narrowband optical frequency comb signal, and output it to the optical coupler 103; the optical coupler 103 is used to inject a part of the initial broadband optical frequency comb signal into the multi-longitudinal mode laser signal. The output is to the feedback modulator 105, and the other part of the initial broadband optical frequency comb signal is output to the control system via the first optical circulator 102; the feedback modulator 105 is used to phase-modulate a part of the initial broadband optical frequency comb signal to obtain a phase-modulated feedback signal and inject it into the multi-longitudinal mode laser 104 via the optical coupler 103, so that the multi-longitudinal mode laser 104 modulates the current broadband optical frequency comb signal generated in real time based on the self-injected phase-modulated feedback signal to obtain the target broadband optical frequency comb signal; wherein, a part of the target broadband optical frequency comb signal is output to the feedback modulator 105 via the optical coupler 103, and the other part of the target broadband optical frequency comb signal is output to the control system via the optical coupler 103 and the first optical circulator 102.

[0055] Specifically, the laser generator 101 outputs an ultrashort pulse laser, whose output bandwidth (i.e., spectrum coverage) is usually narrow and has a spectrum coverage of several nm. The ultrashort pulse laser contains dozens to hundreds of comb teeth, and the comb tooth spacing is greater than 3GHz, which is used to provide a frequency-stable and accurate narrowband optical frequency comb signal, such as Figure 2 As shown. The first optical circulator 102 has a first port, a second port, a third port and a fourth port. The first port of the first optical circulator 102 is used to receive a narrowband optical frequency comb signal, the second port is used to output the narrowband optical frequency comb signal to the optical coupler 103, the third port is used to receive the other part of the initial broadband optical frequency comb signal / target broadband optical frequency comb signal, and the fourth port is used to output the other part of the initial broadband optical frequency comb signal / target broadband optical frequency comb signal to the control system. In this embodiment, by using the first optical circulator 102, the transmission direction of the narrowband optical frequency comb signal can be constrained, and the transmission direction of the other part of the initial broadband optical frequency comb signal / target broadband optical frequency comb signal can be constrained to avoid crosstalk.

[0056] The optical coupler 103 has a first port, a second port, a third port, a fourth port and a fifth port. The first port of the optical coupler 103 is used to receive the narrowband optical frequency comb signal from the first optical circulator 102, the second port is used to output the narrowband optical frequency comb signal to the multi-longitudinal mode laser 104, the third port is used to receive the initial optical frequency comb signal / target broadband optical frequency comb signal from the multi-longitudinal mode laser 104, the fourth port is used to output a part of the initial optical frequency comb signal / target broadband optical frequency comb signal to the feedback modulator 105, and the fifth port is used to output another part of the initial optical frequency comb signal / target broadband optical frequency comb signal to the fourth port of the first optical circulator 102. In this embodiment, the initial optical frequency comb signal / target broadband optical frequency comb signal is processed by using the optical coupler 103, so that a part of the initial optical frequency comb signal / target broadband optical frequency comb signal is output to the feedback modulator 105 and modulated, and the other part of the initial optical frequency comb signal / target broadband optical frequency comb signal can finally be output to the control system.

[0057] It should be noted that if Figure 3 As shown, the multi-longitudinal mode laser 104 can output a multi-longitudinal mode laser signal in a free-running state. The multi-longitudinal mode laser signal is represented in the frequency domain as a plurality of longitudinal modes with a certain frequency interval, and the longitudinal mode interval f t Much larger than the comb tooth spacing f of the narrowband optical frequency comb signal FSR , and the output single longitudinal mode has a laser linewidth of MHz.

[0058] When the control system starts to operate, the multi-longitudinal mode laser 104 receives the self-injected narrowband optical frequency comb signal, and by adjusting the gain of the multi-longitudinal mode laser 104 and the interference effect of the FP cavity of the multi-longitudinal mode laser 104 itself, a series of new frequency comb teeth are generated around each longitudinal mode frequency of the multi-longitudinal mode laser signal under the action of the self-injected narrowband optical frequency comb signal, thereby generating an initial broadband optical frequency comb signal covering the output spectrum of the multi-longitudinal mode laser signal, such as Figure 4 As shown, the comb teeth are expanded to make the optical frequency comb signal suitable for different application scenarios. Due to the influence of the loss, fineness, and gain spectrum of the FP cavity of the multi-longitudinal mode laser 104 itself, the line width of the newly generated comb teeth in the initial broadband optical frequency comb signal is the same as the line width of a single longitudinal mode in the multi-longitudinal mode laser signal, which is relatively wide, as shown in FIG. Figure 5 As shown, the phase coherence between the newly generated comb teeth in the initial broadband optical frequency comb signal is poor, resulting in poor stability of the initial broadband optical frequency comb signal.

[0059] In this embodiment, a portion of the initial broadband optical frequency comb signal is output to the feedback modulator 105 through the optical coupler 103. The feedback modulator 105 performs phase modulation on the portion of the initial broadband optical frequency comb signal to adjust the phase and intensity of the comb teeth, obtains a phase modulated feedback signal and injects it into the multi-longitudinal mode laser 104 through the optical coupler 103, modulates the current broadband optical frequency comb signal generated in real time, suppresses phase error and intensity jitter, thereby obtaining a target broadband optical frequency comb signal, improving the coherence of the newly generated comb teeth, and compressing the line width of the comb teeth, such as Figure 6 As shown, the line width of a single comb tooth in the target broadband optical frequency comb signal becomes narrower, and the stability of the target broadband optical frequency comb signal is higher.

[0060] It should be noted that when the control system starts to operate, the other part of the initial optical frequency comb signal output is an unstable broadband optical frequency comb signal. After the feedback modulator 105 starts to work continuously, the other part of the target broadband optical frequency comb signal output is feedback modulated and becomes a stable broadband optical frequency comb signal.

[0061] In this embodiment, the laser generator 101 generates a narrowband optical frequency comb signal and transmits it through the first optical circulator 102 and the optical coupler 103 to be injected into the multi-longitudinal mode laser 104. The narrowband optical frequency comb signal interferes with the multi-longitudinal mode laser signal generated by the multi-longitudinal mode laser 104, and new comb teeth are expanded to generate an initial broadband optical frequency comb signal, which can be suitable for corresponding application scenarios. However, since the initial broadband optical frequency comb signal is unstable, the initial broadband optical frequency comb signal is divided by the optical coupler 103, so that a part of the initial broadband optical frequency comb signal is output to the feedback modulator 105, and the other part of the initial broadband optical frequency comb signal is output to the feedback modulator 105 through the first optical circulator 102. The control system is output, and a part of the initial broadband optical frequency comb signal is phase modulated by the feedback modulator 105 to obtain a phase modulated feedback signal and inject it into the multi-longitudinal mode laser 104, so that the multi-longitudinal mode laser 104 modulates the current broadband optical frequency comb signal generated in real time based on the self-injected phase modulated feedback signal to obtain a stable target broadband optical frequency comb signal, improve the coherence of the newly generated comb teeth, and compress the line width of the comb teeth. A part of the target broadband optical frequency comb signal is output to the feedback modulator 105 through the optical coupler 103 for continuous modulation and feedback, and another part of the target broadband optical frequency comb signal is output to the control system through the optical coupler 103 and the first optical circulator 102. In this way, in the continuous operation of the control system, the multi-longitudinal mode laser 104 performs tooth expansion adjustment based on the narrowband optical frequency comb signal, so that the optical frequency comb signal can be applied to different application scenarios. At the same time, through the phase modulation effect of the feedback modulator 105, the target broadband optical frequency comb signal output by the control system is stable and available, thereby efficiently adjusting the optical frequency comb frequency.

[0062] See also Figure 7In some embodiments, the feedback modulator 105 includes a second optical circulator 1051, a first phase modulator 1052, a first optical amplifier 1053 and an optical delay device 1054; the second optical circulator 1051 is used to receive a portion of the initial broadband optical frequency comb signal and input it to the first phase modulator 1052; the first phase modulator 1052 is used to modulate the phase of a portion of the initial broadband optical frequency comb signal based on the cavity mode phase of the multi-longitudinal mode laser 104 to obtain a first modulated feedback signal and output it to the first optical amplifier 1053; the first optical amplifier 1053 is used to adjust the amplitude of the first modulated feedback signal based on the cavity mode amplitude of the multi-longitudinal mode laser 104 to obtain a second modulated feedback signal and output it to the optical delay device 1054; the optical delay device 1054 is used to adjust the delay amount of the second modulated feedback signal relative to a portion of the initial broadband optical frequency comb signal to obtain a phase modulated feedback signal and output it to the multi-longitudinal mode laser 104 via the second optical circulator 1051 and the optical coupler 103. Furthermore, the first phase modulator 1052 is used to modulate the phase of a portion of the initial broadband optical frequency comb signal to be consistent with the cavity mode phase of the multi-longitudinal mode laser 104 .

[0063] It should be noted that the second optical circulator 1051 has a first port, a second port and a third port. The first port of the second optical circulator 1051 is used to receive a portion of the initial broadband optical frequency comb signal / target broadband optical frequency comb signal, the second port is used to output a portion of the initial broadband optical frequency comb signal / target broadband optical frequency comb signal to the first phase modulator 1052, and the third port is used to receive a phase modulation feedback signal from the optical delay device 1054. In this embodiment, the phase modulation feedback signal includes frequency comb teeth, which are used to control the optical field of the multi-longitudinal mode laser 104.

[0064] Specifically, there is a phase difference between the phase between the comb teeth in the initial broadband optical frequency comb signal and the cavity mode phase of the multi-longitudinal mode laser 104. According to the required phase adjustment amount, by changing the voltage and chirp of the external driving electrical signal corresponding to the first phase modulator 1052, the phase characteristics of a part of the initial broadband optical frequency comb signal input into the first phase modulator 1052 are changed, so that the phase between each comb tooth in the part of the initial broadband optical frequency comb signal is consistent with the cavity mode phase of the multi-longitudinal mode laser 104, and the part of the initial broadband optical frequency comb signal after modulation is used as the first modulation feedback signal. Further, the first phase modulator 1052 outputs the first modulation feedback signal to the first optical amplifier 1053, and the first optical amplifier 1053 can quickly respond to the voltage change of the corresponding external driving electrical signal to change the amplitude of the first modulation feedback signal to match the cavity mode amplitude of the multi-longitudinal mode laser 104, and obtain the second modulation feedback signal, which can compensate for the loss in the phase modulation and adjust the intensity jitter of the self-injection locking. Finally, the optical delay device 1054 is used to adjust the delay between the second modulated feedback signal and the initial broadband frequency comb signal to obtain a phase modulated feedback signal, so that the phase modulated feedback signal returns to the multi-longitudinal mode laser 104 at a fixed time. The main purpose is to avoid the time jitter caused by the change of the optical path from affecting the self-injection feedback.

[0065] See also Figure 8 In some embodiments, the control system of the present application further includes: a second optical amplifier 106, which is used to amplify the narrowband optical frequency comb signal generated by the laser generator 101, and output the amplified narrowband optical frequency comb signal to the first optical circulator 102. Further, the second optical amplifier 106 is configured as a fiber amplifier, a semiconductor amplifier, or a solid amplifier. Specifically, the narrowband optical frequency comb signal generated by the laser generator 101 is amplified by the second optical amplifier 106, so that the weak narrowband optical frequency comb signal can be amplified, and the power can be adjusted to increase the energy of a single comb tooth.

[0066] In some embodiments, the laser generator 101 includes a continuous laser and a joint modulator; the continuous laser is used to generate an initial ultrashort pulse laser signal, and output the initial ultrashort pulse laser signal to the joint modulator; the joint modulator is used to perform phase modulation and intensity modulation on the initial ultrashort pulse laser signal to obtain a narrowband optical frequency comb signal. Further, the joint modulator includes a second phase modulator and an intensity modulator, the second phase modulator is used to perform phase modulation on the ultrashort pulse laser signal, and the intensity modulator is used to perform intensity modulation on the phase-modulated ultrashort pulse laser signal to output a narrowband optical frequency comb signal.

[0067] Specifically, a stable initial ultrashort pulse laser signal is generated by a continuous laser. Under the action of an external phase modulation driving signal, a second phase modulator performs phase modulation on the ultrashort pulse laser signal. At the same time, under the action of an external intensity driving signal, an intensity modulator performs intensity modulation on the phase-modulated ultrashort pulse laser signal to output a narrowband optical frequency comb signal with stable and accurate frequency.

[0068] See also Figure 1 and Fig. 9 Based on the same inventive concept, the present application also provides a control method for an optical frequency comb frequency control system, including:

[0069] S101, obtaining a narrowband optical frequency comb signal, transmitting the narrowband optical frequency comb signal and injecting it into a multi-longitudinal mode laser 104;

[0070] S102, generating a multi-longitudinal mode laser signal by the multi-longitudinal mode laser 104, and generating an initial broadband optical frequency comb signal according to the multi-longitudinal mode laser signal and the self-injected narrowband optical frequency comb signal;

[0071] S103, outputting a portion of the initial broadband optical frequency comb signal to the feedback modulator 105, and outputting another portion of the initial broadband optical frequency comb signal to the control system;

[0072] S104, phase modulating a portion of the initial broadband optical frequency comb signal through the feedback modulator 105 to obtain a phase modulated feedback signal and injecting it into the multi-longitudinal mode laser 104;

[0073] S105, based on the self-injected phase modulation feedback signal, modulate the current broadband optical frequency comb signal generated in real time by the multi-longitudinal mode laser 104 to obtain a target broadband optical frequency comb signal;

[0074] S106, outputting a portion of the target broadband optical frequency comb signal to the feedback modulator 105, and outputting another portion of the target broadband optical frequency comb signal to the control system.

[0075] Specifically, interference occurs between the narrowband optical frequency comb signal and the multi-longitudinal mode laser signal generated by the multi-longitudinal mode laser 104, and new comb teeth are extended on the multi-longitudinal mode laser signal to generate an initial broadband optical frequency comb signal, which can be suitable for corresponding application scenarios. However, the initial broadband optical frequency comb signal is unstable.

[0076] Furthermore, a part of the initial broadband optical frequency comb signal is output to the feedback modulator 105, and another part of the initial broadband optical frequency comb signal is output to the control system, and a part of the initial broadband optical frequency comb signal is phase-modulated by the feedback modulator 105 to obtain a phase-modulated feedback signal and inject it into the multi-longitudinal mode laser 104, so that the multi-longitudinal mode laser 104 modulates the current broadband optical frequency comb signal generated in real time based on the self-injected phase-modulated feedback signal to obtain a stable target broadband optical frequency comb signal, improve the coherence of the newly generated comb teeth, and compress the linewidth of the comb teeth, and a part of the target broadband optical frequency comb signal is output to the feedback modulator 105 for continuous modulation and feedback, and another part of the target broadband optical frequency comb signal is output to the control system.

[0077] In this way, during the continuous operation of the control system, the multi-longitudinal mode laser 104 performs tooth expansion adjustment based on the narrowband optical frequency comb signal, so that the optical frequency comb signal can be suitable for different application scenarios. At the same time, through the phase modulation effect of the feedback modulator 105, the target broadband optical frequency comb signal continuously output by the control system is stable and available, thereby efficiently adjusting the optical frequency comb frequency.

[0078] See also Fig.10 In some embodiments, in step S104, a part of the initial broadband optical frequency comb signal is phase modulated by the feedback modulator 105 to obtain a phase modulated feedback signal, including:

[0079] S201, based on the cavity mode phase of the multi-longitudinal mode laser 104, modulate the phase of a portion of the initial broadband optical frequency comb signal through the first phase modulator 1052 to obtain a first modulated feedback signal;

[0080] S202, based on the cavity mode amplitude of the multi-longitudinal mode laser 104, adjusting the amplitude of the first modulated feedback signal through the first optical amplifier 1053 to obtain a second modulated feedback signal;

[0081] S203, adjusting the delay of the second modulated feedback signal relative to a portion of the initial broadband optical frequency comb signal to obtain a phase modulated feedback signal.

[0082] Specifically, there is a phase difference between the phase between the comb teeth in the initial broadband optical frequency comb signal and the cavity mode phase of the multi-longitudinal mode laser 104. Under the action of the external driving signal, the first phase modulator 1052 modulates the phase of the above-mentioned part of the initial broadband optical frequency comb signal so that the phase between the comb teeth in the part of the initial broadband optical frequency comb signal is consistent with the cavity mode phase of the multi-longitudinal mode laser 104, and obtains a first modulated feedback signal. Further, the first phase modulator 1052 outputs the first modulated feedback signal to the first optical amplifier 1053, and the first optical amplifier 1053 adjusts the amplitude of the first modulated feedback signal based on the cavity mode amplitude of the multi-longitudinal mode laser 104 to obtain a second modulated feedback signal to compensate for the loss in the phase modulation and adjust the intensity jitter of the self-injection locking. Finally, the optical delay device 1054 is used to adjust the delay between the second modulated feedback signal and the initial broadband frequency comb signal to obtain a phase modulated feedback signal, so that the phase modulated feedback signal returns to the multi-longitudinal mode laser 104 at a fixed time, the main purpose of which is to avoid the time jitter caused by the change of the optical path from affecting the self-injection feedback.

[0083] In some embodiments, before the narrowband optical frequency comb signal is injected into the multi-longitudinal mode laser 104, the method further includes: amplifying the narrowband optical frequency comb signal, so that the amplified narrowband optical frequency comb signal is output to the multi-longitudinal mode laser 104. In this way, the weak narrowband optical frequency comb signal can be amplified, and the power can be adjusted to increase the energy of a single comb tooth.

[0084] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. An optical frequency comb frequency control system, characterized in that: include: A laser generator, a first optical circulator, an optical coupler, a multi-longitudinal mode laser and a feedback modulator; The laser generator is used to generate a narrowband optical frequency comb signal and output it to the first optical circulator; The first optical circulator is used to inject the narrowband optical frequency comb signal into the multi-longitudinal mode laser via the optical coupler; The multi-longitudinal mode laser is used to generate a multi-longitudinal mode laser signal, and according to the multi-longitudinal mode laser signal and the self-injected narrow-band optical frequency comb signal, an initial broadband optical frequency comb signal is generated and output to the optical coupler; The optical coupler is used to output a part of the initial broadband optical frequency comb signal to the feedback modulator, and output another part of the initial broadband optical frequency comb signal to the control system via the first optical circulator; The feedback modulator is used to phase-modulate a portion of the initial broadband optical frequency comb signal to obtain a phase-modulated feedback signal and inject it into the multi-longitudinal mode laser through an optical coupler, so that the multi-longitudinal mode laser modulates the current broadband optical frequency comb signal generated in real time based on the self-injected phase-modulated feedback signal to obtain a target broadband optical frequency comb signal; Part of the target broadband optical frequency comb signal is output to the feedback modulator via the optical coupler, and another part of the target broadband optical frequency comb signal is output to the control system via the optical coupler and the first optical circulator; The feedback modulator comprises a second optical circulator, a first phase modulator, a first optical amplifier and an optical delay device; The second optical circulator is used to receive a portion of the initial broadband optical frequency comb signal and input it to the first phase modulator; The first phase modulator is used to modulate the phase of a portion of the initial broadband optical frequency comb signal based on the cavity mode phase of the multi-longitudinal mode laser to obtain a first modulated feedback signal and output it to the first optical amplifier; The first optical amplifier is used to adjust the amplitude of the first modulated feedback signal based on the cavity mode amplitude of the multi-longitudinal mode laser to obtain a second modulated feedback signal and output it to the optical delay device; The optical delay device is used to adjust the delay amount of the second modulated feedback signal relative to a portion of the initial broadband optical frequency comb signal to obtain the phase modulated feedback signal and output it to the multi-longitudinal mode laser through the second optical circulator and the optical coupler.

2. The optical frequency comb frequency control system according to claim 1, characterized in that: The first phase modulator is used to modulate the phase of a portion of the initial broadband optical frequency comb signal to be consistent with the cavity mode phase of the multi-longitudinal mode laser.

3. The optical frequency comb frequency control system according to claim 1, characterized in that: Also includes: The second optical amplifier is used to amplify the narrowband optical frequency comb signal generated by the laser generator, and output the amplified narrowband optical frequency comb signal to the first optical circulator.

4. The optical frequency comb frequency control system according to claim 3, characterized in that: The second optical amplifier is configured as a fiber amplifier, a semiconductor amplifier or a solid-state amplifier.

5. The optical frequency comb frequency control system according to any one of claims 1 to 4, characterized in that: The laser generator includes a continuous laser and a joint modulator; The continuous laser is used to generate an initial ultrashort pulse laser signal, and output the initial ultrashort pulse laser signal to the joint modulator; The joint modulator is used to perform phase modulation and intensity modulation on the initial ultrashort pulse laser signal to obtain the narrowband optical frequency comb signal.

6. The optical frequency comb frequency control system according to claim 5, characterized in that: The joint modulator includes a second phase modulator and an intensity modulator. The second phase modulator is used to perform phase modulation on the ultrashort pulse laser signal. The intensity modulator is used to perform intensity modulation on the phase-modulated ultrashort pulse laser signal to output a narrowband optical frequency comb signal.

7. A control method for an optical frequency comb frequency control system according to any one of claims 1 to 6, characterized in that: include: Acquire a narrowband optical frequency comb signal, transmit and inject the narrowband optical frequency comb signal into a multi-longitudinal mode laser; Generate a multi-longitudinal mode laser signal by the multi-longitudinal mode laser, and generate an initial broadband optical frequency comb signal according to the multi-longitudinal mode laser signal and the self-injected narrowband optical frequency comb signal; Outputting a portion of the initial broadband optical frequency comb signal to a feedback modulator, and outputting another portion of the initial broadband optical frequency comb signal to a control system; Phase modulating a portion of the initial broadband optical frequency comb signal through the feedback modulator to obtain a phase modulated feedback signal and injecting it into the multi-longitudinal mode laser; Based on the self-injected phase modulation feedback signal, modulate the current broadband optical frequency comb signal generated in real time by the multi-longitudinal mode laser to obtain a target broadband optical frequency comb signal; Part of the target broadband optical frequency comb signal is output to the feedback modulator, and another part of the target broadband optical frequency comb signal is output to the control system.

8. The control method of the optical frequency comb frequency control system according to claim 7, characterized in that: The phase-modulating a portion of the initial broadband optical frequency comb signal by the feedback modulator to obtain a phase-modulated feedback signal comprises: Based on the cavity mode phase of the multi-longitudinal mode laser, modulating the phase of a portion of the initial broadband optical frequency comb signal by a first phase modulator to obtain a first modulated feedback signal; Based on the cavity mode amplitude of the multi-longitudinal mode laser, adjusting the amplitude of the first modulated feedback signal through a first optical amplifier to obtain a second modulated feedback signal; The delay amount of the second modulated feedback signal relative to a portion of the initial broadband optical frequency comb signal is adjusted to obtain the phase modulated feedback signal.

9. The control method of the optical frequency comb frequency control system according to claim 7, characterized in that: Before the narrowband optical frequency comb signal is injected into the multi-longitudinal mode laser, the method further includes: amplifying the narrowband optical frequency comb signal so that the amplified narrowband optical frequency comb signal is output to the multi-longitudinal mode laser.

Images