A Brillouin single-frequency laser and a method for self-stabilizing laser frequency

Abstract

The present invention provides a Brillouin single-frequency laser and a method for self-stabilizing the frequency of a laser. The device includes a pump laser, a polarization beam splitter, a fast-axis control branch, a slow-axis control branch, a Brillouin cavity, a Brillouin frequency-stabilizing feedforward loop, and a local oscillator driver. The single-frequency laser generated by the pump laser is divided into a fast-axis pump laser and a slow-axis pump laser by the polarization beam splitter. The fast-axis and slow-axis control branches respectively control the phase and frequency of the laser signal, and then input it into the Brillouin cavity. According to the reverse Brillouin laser detected by the fast-axis and slow-axis control branches, the frequency change caused by the Brillouin temperature drift is calculated, and the frequency feedforward compensation is performed on the fast-axis reverse Brillouin laser, and a Brillouin laser with stable frequency is output, and the electrical drive frequency signal required for realizing phase-locked control is provided by the local oscillator driver. Through this scheme, Brillouin laser feedforward compensation can be realized, the temperature influence can be reduced, and the stability and reliability of the laser frequency stabilization system can be guaranteed.

Description

Technical Field

[0001] The invention belongs to the field of laser technology, and in particular relates to a Brillouin single-frequency laser and a laser frequency self-stabilization method. Background Art

[0002] The core issue of the current large-scale application of optical atomic clock systems focuses on achieving the portability of optical clock systems, which requires a lot of modifications to the existing optical clock architecture, including the miniaturization and lightweighting of the clock laser. The performance of the optical clock laser is the core of the operation of the optical clock. The key is to maintain frequency stability while reducing the size of the optical clock laser. This stability is reflected in two time scales. One is that the laser remains near the atomic narrow linewidth transition for a period of time (about a few minutes) before the optical clock feedback is started; the other is to remain locked to the frequency required for the atomic transition between feedback cycles (about milliseconds). So far, these strict requirements have eliminated many laser system design schemes. Only frequency-stabilized lasers based on bulk cavities can meet this requirement, especially this technology can provide laser linewidths of less than 1Hz. However, the large size of the bulk cavity and the bulky and vibration-prone vacuum system make it difficult to miniaturize and lightweight such lasers.

[0003] Stimulated Brillouin laser is a highly promising technology that can achieve miniaturization and lightweight of frequency-stabilized lasers. Due to the existence of stimulated phonons, it provides an additional mechanism for filtering laser phase and intensity noise, which enables stimulated Brillouin lasers to exceed the limit linewidth level that can be achieved by the resonant cavity Q value. Compared with bulk cavity stabilized lasers, stimulated Brillouin lasers have the advantages of small cavity size, no need for vacuum environment, easy installation on any plane, and possible higher vibration resistance. However, there is a big problem with stimulated Brillouin lasers in frequency stabilization, that is, the temperature sensitivity of the cavity far exceeds that of bulk stabilized lasers. This is because the current stimulated Brillouin cavity relies on a waveguide cavity of a certain length, which causes the laser to produce considerable frequency drift as the temperature changes, which greatly affects the stability and reliability of the frequency stabilization system. Summary of the invention

[0004] In view of this, the embodiments of the present invention provide a Brillouin single-frequency laser and a laser frequency self-stabilization method, which are used to solve the problem that the stimulated Brillouin laser cavity has high temperature sensitivity, affecting the stability and reliability of the frequency stabilization system.

[0005] In a first aspect of an embodiment of the present invention, a Brillouin single-frequency laser is provided, comprising:

[0006] A pump laser for providing a single-frequency laser to stimulate the stimulated Brillouin effect;

[0007] A polarization beam splitter, used for splitting the input single-frequency laser into a fast-axis pump laser and a slow-axis pump laser according to the polarization state;

[0008] The fast axis control branch is used to control the phase of the fast axis pump laser, amplify the frequency and input it into the Brillouin cavity, and detect the fast axis reverse Brillouin laser;

[0009] The slow axis control branch is used to control the phase of the slow axis pump laser, amplify the frequency and input it into the Brillouin cavity, and detect the slow axis reverse Brillouin laser;

[0010] A Brillouin cavity, used for generating a stimulated Brillouin effect according to input fast-axis pump laser and slow-axis pump laser, and generating Brillouin laser;

[0011] The Brillouin frequency stabilization feedforward loop is used to receive the reverse Brillouin laser detected by the fast-axis control branch and the slow-axis control branch, calculate the frequency change caused by the Brillouin temperature drift according to the reverse Brillouin laser, and perform frequency feedforward compensation on the fast-axis reverse Brillouin laser according to the frequency change, and output a Brillouin laser with stable frequency;

[0012] The local oscillator driver is used to provide the electrical driving frequency signal required for the fast axis control branch, the slow axis control branch and the Brillouin frequency stabilization feedforward loop to realize phase-locked control.

[0013] In a second aspect of an embodiment of the present invention, a laser frequency self-stabilization method is provided, comprising:

[0014] After the single-frequency laser output by the pump laser is split into a fast-axis pump laser and a slow-axis pump laser by a polarization beam splitter;

[0015] After phase control and frequency amplification of the fast-axis pump laser and the slow-axis pump laser respectively, the fast-axis pump laser and the slow-axis pump laser are input into the Brillouin cavity;

[0016] In the Brillouin cavity, a stimulated Brillouin effect is generated based on the fast-axis pump laser and the slow-axis pump laser, and the generated reverse Brillouin laser is detected;

[0017] The frequency change caused by the Brillouin temperature drift is calculated according to the reverse Brillouin laser detected by the fast axis and the reverse Brillouin laser detected by the slow axis, and the frequency feedforward compensation is performed on the reverse Brillouin laser detected by the fast axis according to the frequency change to output the Brillouin laser with stable frequency;

[0018] The local oscillator driver provides an electrical driving frequency signal for fast-axis pump laser regulation, slow-axis pump laser regulation and phase-locked control of Brillouin laser feedforward compensation.

[0019] In the embodiment of the present invention, based on the characteristics of the stimulated Brillouin laser transmitting orthogonal polarization modes in the fast axis and slow axis waveguide structures, and the different temperature sensitivity in the polarization modes, the temperature drift of the Brillouin cavity is characterized by detecting the change in the fixed frequency difference between the reverse Brillouin lasers in the polarization mode, and the Brillouin laser frequency is feed-forward compensated, so that the self-stabilization of the Brillouin resonant cavity temperature can be achieved without introducing a reference temperature, avoiding the problems of high temperature sensitivity and laser frequency drift of the traditional Brillouin laser cavity, and ensuring the stability and reliability of the frequency stabilization system. By introducing a forward feedback mechanism, the temperature of the cavity is not directly regulated, but the frequency of the output Brillouin laser is directly changed, which can avoid the problems of slow temperature feedback closed-loop process and the feedback system being easily disturbed by the external environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 A schematic diagram of the structure of a Brillouin single-frequency laser provided by one embodiment of the present invention;

[0022] Figure 2 A schematic diagram of the structure of a fast axis control branch provided by an embodiment of the present invention;

[0023] Figure 3 A schematic diagram of the structure of a slow axis control branch provided by an embodiment of the present invention;

[0024] Figure 4 A schematic diagram of the structure of a Brillouin frequency stabilization feedforward loop provided by an embodiment of the present invention;

[0025] Figure 5 A schematic diagram of the structure of a local oscillator driver provided by an embodiment of the present invention;

[0026] Figure 6 Another structural schematic diagram of a local oscillator driver provided by an embodiment of the present invention;

[0027] Figure 7 A schematic flow chart of a laser frequency self-stabilization method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] It should be understood that the term "including" and other similar expressions in the specification or claims of the present invention and the above-mentioned drawings are intended to cover non-exclusive inclusions, such as a process, method, system, or device including a series of steps or units is not limited to the listed steps or units. In addition, "first" and "second" are used to distinguish different objects, not to describe a specific order.

[0030] See also Figure 1 , a schematic diagram of the structure of a Brillouin single-frequency laser provided in an embodiment of the present invention, the laser comprising:

[0031] A pump laser 110, used to provide a single-frequency laser to stimulate the stimulated Brillouin effect;

[0032] Stimulated Brillouin effect is also known as stimulated Brillouin scattering. It is caused by the electromagnetic stretching effect generated by light waves, which excites ultrasound waves in the material, and the incident light is scattered by ultrasound waves. Specifically, a pump photon is converted into a Stokes photon with a reduced frequency and an acoustic phonon. When the gain provided by the pump light is greater than the propagation loss of the photon or phonon, a Brillouin photon laser or phonon laser with extremely high coherence can be generated.

[0033] A polarization beam splitter 120, used to split the input single-frequency laser into a fast-axis pump laser and a slow-axis pump laser according to the polarization state;

[0034] The fast axis control branch 130 is used to control the phase of the fast axis pump laser, amplify the frequency and input it into the Brillouin cavity, and detect the fast axis reverse Brillouin laser;

[0035] The slow axis control branch 140 is used to control the phase of the slow axis pump laser, amplify the frequency and input it into the Brillouin cavity, and detect the slow axis reverse Brillouin laser;

[0036] The Brillouin cavity 150 is used to generate a stimulated Brillouin effect according to the input fast-axis pump laser and slow-axis pump laser, and generate Brillouin laser;

[0037] The Brillouin laser generated in the Brillouin cavity 150 can be detected by the fast-axis control branch 130 and the slow-axis control branch 140 , and transmitted as reverse Brillouin laser to the Brillouin frequency stabilization feedforward loop 160 for frequency stabilization output.

[0038] The Brillouin frequency stabilization feedforward loop 160 is used to receive the reverse Brillouin laser detected by the fast axis control branch and the slow axis control branch, calculate the frequency change caused by the Brillouin temperature drift according to the reverse Brillouin laser; and perform frequency feedforward compensation on the fast axis reverse Brillouin laser according to the frequency change, and output a Brillouin laser with stable frequency;

[0039] The local oscillator driver 170 is used to provide the electrical driving frequency signal required for the fast axis control branch, the slow axis control branch and the Brillouin frequency stabilization feedforward loop to realize phase-locked control.

[0040] Among them, the output end of the pump laser 110 is connected to the input end of the polarization beam splitter 120, the output end of the polarization beam splitter 120 is respectively connected to the fast axis control branch 130 and the slow axis control branch 140, the fast axis control branch 130 and the slow axis control branch 140 are both connected to the Brillouin cavity 150, the other end of the fast axis control branch 130 and the slow axis control branch 140 are also connected to the Brillouin frequency stabilization feedforward loop 160, and the output end of the local oscillator driver 170 is respectively connected to the fast axis control branch 130, the slow axis control branch 140 and the Brillouin frequency stabilization feedforward loop 160.

[0041] The pump laser 110 provides a single-frequency laser to stimulate the stimulated Brillouin effect. The polarization beam splitter 120 divides the input single-frequency laser into a fast-axis laser and a slow-axis laser according to the polarization state. The output ends are connected to the fast-axis control branch 130 and the slow-axis control branch 140 respectively. The fast-axis control branch 130 provides optical power amplification, fast-axis phase control, and fast-axis reverse Brillouin detection functions, and can realize PDH (Pound-Drever-Hall) frequency stabilization and fast-axis stimulated Brillouin laser power stabilization functions. It transmits the fast-axis stimulated Brillouin laser reflected from the Brillouin cavity 150 to the Brillouin frequency stabilization feedforward loop 160; the slow-axis control branch 140 is connected to the Brillouin cavity 150, and can provide optical power amplification, slow-axis optical frequency shift, slow-axis phase control, and slow-axis reverse Brillouin detection functions, and can realize the slow-axis pump laser PDH frequency stabilization and slow-axis stimulated Brillouin laser power stabilization functions. It can input the slow-axis stimulated Brillouin laser reflected from the Brillouin cavity 150 into the Brillouin frequency stabilization feedforward loop 160.

[0042] After receiving the fast and slow axis reverse Brillouin lasers, the Brillouin frequency stabilization feedforward loop 160 can detect the frequency change caused by the Brillouin temperature drift, and use the electro-optical modulation device to implement frequency feedforward compensation, and output the Brillouin laser with stable frequency. The local oscillator driver 170 is used to provide the electrical driving frequency signal required for the phase-locked control of the fast axis control branch 130, the slow axis control branch 140, and the Brillouin frequency stabilization feedforward loop 160.

[0043] In one embodiment, Figure 2As shown, the fast axis control branch 130 includes a fast axis phase modulator 210, a fast axis optical amplifier 220, a fast axis optical circulator 230, a first polarization coupler 240a, a second polarization coupler 240b, a fast axis frequency stabilization control circuit 250, a fast axis coupler 260 and a fast axis optical power feedback circuit 270;

[0044] The fast axis phase modulator 210 is used to perform phase modulation on the fast axis pump laser;

[0045] The fast axis optical amplifier 220 is used to increase the fast axis pump laser power to achieve the optical power required by stimulated Brillouin.

[0046] The fast axis optical circulator 230 is used for laser signal transmission;

[0047] The first port of the fast axis optical circulator 230 is connected to the fast axis optical amplifier 220 , the second port is connected to the first polarization coupler 240 a , and the third port is connected to the fast axis coupler 260 ;

[0048] The first polarization coupler 240a is used to couple fast-axis pump lasers of different polarization states and output them to the Brillouin cavity 150; and receive the reverse Brillouin laser generated by the Brillouin cavity 150;

[0049] The second polarization coupler 240b is used to receive the fast-axis pump laser that passes through the Brillouin cavity and is affected by the Brillouin effect, and transmit the fast-axis pump laser to the fast-axis frequency stabilization control circuit 250;

[0050] The fast-axis frequency stabilization control circuit 250 is used to adjust the fast-axis phase modulator 210 based on the PDH frequency stabilization principle according to the detected phase change of the optical field of the fast-axis pump laser;

[0051] The fast axis coupler 260 is used to split the reverse Brillouin laser beam transmitted from the fast axis optical circulator 230, and connect the low splitting ratio end to the fast axis power feedback circuit 270, and output the high splitting ratio end as the fast axis reverse Brillouin laser;

[0052] The fast-axis optical power feedback circuit 270 is used to feedback control the power of the fast-axis optical amplifier 220 according to the power jitter of the reverse Brillouin laser at the low splitting ratio end of the fast-axis coupler, so as to stabilize the fast-axis pump laser.

[0053] Among them, the fast-axis pump laser enters the fast-axis phase modulator 210, the output end of the fast-axis phase modulator 210 is connected to the fast-axis optical amplifier 220, the output end of the fast-axis optical amplifier 220 is connected to the first port of the fast-axis optical circulator 230, the second port of the fast-axis optical circulator 230 is connected to the first polarization coupler 240a, and the third port is connected to the input end of the fast-axis coupler 260; the first polarization coupler 240a is connected to one end of the Brillouin cavity 150, the other end of the Brillouin cavity 150 is connected to the second polarization coupler 240b, and the other end of the second polarization coupler 240b is connected to the fast-axis frequency stabilization control circuit 250; one end of the output end of the fast-axis coupler 260 is connected to the input end of the fast-axis optical frequency feedback circuit 270, and the other end outputs the fast-axis Brillouin laser; the output end of the fast-axis optical frequency feedback circuit 270 is connected to the fast-axis optical amplifier 220.

[0054] The single-frequency fast-axis pump laser enters the fast-axis optical phase modulator 210 for phase modulation and is transmitted to the fast-axis optical amplifier 220. The fast-axis optical amplifier 220 increases the output optical power to exceed the threshold of stimulated Brillouin generation, enters the fast-axis optical circulator 230, enters the first polarization coupler 240a, and is then injected into the Brillouin cavity 150 to stimulate the generation of Brillouin laser. The remaining fast-axis pump light affected by the Brillouin effect passes through the Brillouin cavity 150 and is transmitted to the fast-axis frequency stabilization control circuit 250 through the second polarization coupler 240b. The fast-axis frequency stabilization control circuit 250 detects the fast-axis pump light modulated by the Brillouin cavity 150. The phase change of the fast-axis pump light field after the PDH frequency stabilization principle is used to adjust the fast-axis optical phase modulator 210 to stabilize the fast-axis pump laser; the stimulated Brillouin laser generated by the Brillouin cavity 150 is reversed to the first polarization coupler 240a, and is output to the fast-axis coupler 260 through the third port of the fast-axis optical circulator 230 for beam splitting. The high-splitting ratio end is used as the output fast-axis Brillouin laser, and the low-splitting ratio end is connected to the fast-axis power feedback circuit 270. The fast-axis power feedback circuit 270 feedback controls the power of the fast-axis optical amplifier 220 according to the power jitter of the fast-axis Brillouin laser to stabilize the fast-axis pump laser.

[0055] In one embodiment, Figure 3 As shown, the slow axis control branch 140 includes a first optical frequency shifter 310, a slow axis phase modulator 320, a slow axis optical amplifier 330, a slow axis optical circulator 340, a first polarization coupler 240a, a second polarization coupler 240b, a slow axis frequency stabilization controller circuit 350, a slow axis coupler 360 and a slow axis optical power feedback circuit 370;

[0056] The first optical frequency shifter 310 is used to generate a fixed frequency offset under the control of a local oscillator driver;

[0057] The slow axis phase modulator 320 is used to perform phase modulation on the slow axis pump laser;

[0058] The slow axis optical amplifier 330 is used to increase the slow axis pump laser power to achieve the optical power required for stimulated Brillouin.

[0059] The slow axis optical circulator 340 is used for laser signal transmission;

[0060] The first port of the slow axis optical circulator 340 is connected to the slow axis optical amplifier 330 , the second port is connected to the second polarization coupler 240 b , and the third port is connected to the slow axis coupler 360 ;

[0061] The second polarization coupler 240b is further used to couple slow-axis pump lasers of different polarization states and output them to the Brillouin cavity 150; and receive the reverse Brillouin laser generated by the Brillouin cavity 150;

[0062] The first polarization coupler 240a is also used to receive the slow axis pump laser that passes through the Brillouin cavity and is affected by the Brillouin effect;

[0063] The slow axis frequency stabilization control circuit 350 is used to adjust the slow axis phase modulator 320 based on the PDH frequency stabilization principle according to the detected light field phase change of the slow axis pump laser;

[0064] The slow axis coupler 360 is used to split the reverse Brillouin laser beam transmitted from the slow axis optical circulator 340, and connect the low splitting ratio end to the slow axis optical power feedback circuit 370, and output the high splitting ratio end as the slow axis reverse Brillouin laser.

[0065] The slow axis optical power feedback circuit 370 is used to feedback control the power of the slow axis optical amplifier 330 according to the power jitter of the reverse Brillouin laser at the low splitting ratio end of the slow axis coupler 360 to stabilize the slow axis pump laser.

[0066] Among them, the slow axis pump laser enters the first optical frequency shifter 310, the output end of the first optical frequency shifter 310 is connected to the slow axis phase modulator 320, the output end of the slow axis phase modulator 320 is connected to the slow axis optical amplifier 330, the output end of the slow axis optical amplifier 330 is connected to the first port of the slow axis optical circulator 340, the second port of the slow axis optical circulator 340 is connected to the second polarization coupler 240b, and the third port is connected to the input end of the slow axis coupler 360; the second polarization coupler 240b is connected to one end of the Brillouin cavity 150, the other end of the Brillouin cavity 150 is connected to the first polarization coupler 240a, and the other end of the first polarization coupler 240a is connected to the slow axis frequency stabilization control circuit 350; one end of the output end of the slow axis coupler 360 is connected to the input end of the slow axis optical frequency feedback circuit 370, and the other end outputs the slow axis Brillouin laser; the output end of the slow axis optical frequency feedback circuit 370 is connected to the slow axis optical amplifier 330.

[0067] The single-frequency slow-axis pump light enters the optical frequency shifter 310, and generates a fixed frequency offset under the control of the local oscillator driving circuit 170; the pump laser is phase-modulated by the slow-axis optical phase modulator 320, and the output optical power is increased by the slow-axis optical amplifier 330 to reach the threshold of stimulated Brillouin generation, and the slow-axis pump laser is input to the first port of the slow-axis optical circulator, output from the second port of the slow-axis optical circulator 340, and injected into the Brillouin cavity 150 through the second polarization coupler 240b, and the fast-axis Brillouin laser whose polarization state is transmitted along the slow axis is excited. The rest of the slow-axis pump light affected by the Brillouin effect passes through the Brillouin cavity 150, enters the first polarization coupler 240a, and is transmitted to the slow-axis frequency stabilization circuit 150. The control circuit 350, the slow-axis frequency stabilization control circuit 350 detects the phase change of the slow-axis pump light field modulated by the Brillouin cavity 150, and uses the PDH frequency stabilization principle to adjust the slow-axis optical phase modulator 320 to stabilize the slow-axis pump laser; the stimulated Brillouin laser generated by the Brillouin cavity 150 is reversed back to the second polarization coupler 240b, and is output to the slow-axis coupler 360 through the third port of the slow-axis optical circulator 340 for beam splitting, and the high-splitting ratio end is used as the output slow-axis Brillouin laser, and the low-splitting ratio end is connected to the slow-axis power feedback circuit 270; the slow-axis power feedback circuit 270 feedback controls the power of the slow-axis optical amplifier 330 according to the power jitter of the slow-axis Brillouin laser to stabilize the slow-axis pump laser.

[0068] In one embodiment, Figure 4 As shown, the Brillouin frequency stabilization feedforward loop includes an optical beam splitter 410, an optical coupler 420, a second optical frequency shifter 430, a balanced detector 440 and an optical mixer 450;

[0069] The optical beam splitter 410 is used to split the fast-axis reverse Brillouin laser, input the first split beam as the Brillouin laser to be stabilized into the second optical frequency shifter 430, and input the second split beam together with the slow-axis reverse Brillouin laser into the optical coupler 420;

[0070] The optical coupler 420 is used to couple the second split beam of the fast-axis reverse Brillouin laser to the slow-axis reverse Brillouin laser;

[0071] The second optical frequency shifter 430 is used to receive the Brillouin laser to be frequency-stabilized and the control signal of the local oscillator driver 170 transmitted by the optical beam splitter 410, and output the Brillouin laser with a stabilized frequency;

[0072] The balanced detector 440 is used to convert the Brillouin cavity jitter signal caused by temperature into a voltage signal through optical heterodyne detection, and output it to the optical mixer 450;

[0073] The optical mixer 450 is used to mix the voltage signal transmitted by the balanced detector 440 with the control signal output by the local oscillator driver 170 to obtain a frequency error signal corresponding to the temperature change, and load the frequency error signal to the electrical signal of the local oscillator driver 170 to drive the second optical frequency shifter, so as to control the operating frequency of the second optical frequency shifter 430 and compensate for the temperature drift.

[0074] Wherein, the splitting ratio between the first beam and the second beam in the optical beam splitter is 9:1.

[0075] Among them, the fast-axis reverse Brillouin laser enters the optical beam splitter 410, that is, the optical beam splitter 410 is connected to the output end of the fast-axis coupler, the output end of the optical beam splitter 410 is respectively connected to the optical coupler 420 and the second optical frequency shifter 430, the input end of the optical coupler 420 can be connected to the optical beam splitter 410 and the slow-axis coupler, the output end of the optical coupler 420 is connected to the balanced detector 440, the output end of the balanced detector 440 is connected to the mixer 450, the input end of the mixer 450 is also connected to the local oscillator driver 170, the output end of the mixer 450 is connected to the local oscillator driver 170, the output end of the local oscillator driver 170 is connected to the second optical frequency shifter 430, and the second optical frequency shifter 430 outputs a stabilized frequency Brillouin laser.

[0076] After the high-power fast-axis Brillouin laser is input into the optical beam splitter 410 for splitting, the high splitting ratio end is connected to the second optical frequency shifter 430 as the Brillouin laser to be stabilized, and the low splitting ratio end is coupled to the optical coupler 420 together with the slow-axis Brillouin laser. The two output ports of the optical coupler 420 are connected to the balanced detector 440. The Brillouin cavity jitter signal caused by temperature is converted into a voltage signal through optical heterodyne detection and input into the mixer 450. In the mixer 450, it is mixed with the control signal in the local oscillator driver 170 to obtain a frequency error signal corresponding to the temperature change, and is loaded on the electrical signal in the local oscillator driver 170 to drive the second optical frequency shifter 430, so as to control the operating frequency of the second optical frequency shifter 430 and compensate for the temperature drift.

[0077] In one embodiment, the output end of the local oscillator driver 170 is connected to the pump laser 110 to provide a driving signal for the pump laser 110 .

[0078] In one embodiment, Figure 5 As shown, the local oscillator driver 170 includes an external clock 510, a voltage-controlled oscillator 520, a first digital frequency divider 530, a first mixer 540, a first PID controller 550, a second mixer 560 and a second PID controller 570;

[0079] The external clock 510 is used to provide a basic clock signal;

[0080] The voltage controlled oscillator 520 is used to provide a frequency signal of a predetermined frequency as a frequency source;

[0081] The first digital frequency divider 530 is used to divide the frequency signal;

[0082] Wherein, the output end of the first digital frequency divider 530 is connected to the first mixer 540, the fast axis phase modulator 210, the second mixer 560, and the slow axis phase modulator 320 respectively;

[0083] The first mixer 540 is used for mixing and phase-detecting the output signal of the first digital frequency divider 530 and the signal of the slow-axis frequency stabilization control circuit to obtain an error signal and output it to the first PID controller;

[0084] The first PID controller 550 is used to generate a driving signal for controlling the optical frequency shifter in the slow axis control branch according to the error signal;

[0085] The second mixer 560 is used for mixing and phase-detecting the output signal of the first digital frequency divider 530 and the signal of the fast-axis frequency stabilization control circuit to obtain an error signal and output it to the second PID controller;

[0086] The second PID controller 570 is used to generate a driving signal for controlling the pump laser 110 according to the error signal.

[0087] The voltage-controlled oscillator 520 provides a frequency signal of 1 GHz, the frequency division coefficient of the first digital frequency divider is 5, and the generated signal frequency is 200 MHz.

[0088] Among them, the external clock 510 is connected to one end of the voltage-controlled oscillator 520, the other end of the voltage-controlled oscillator 520 is connected to the first digital frequency divider 530, the output end of the first digital frequency divider 530 is respectively connected to the first mixer 540, the fast-axis phase modulator 210, the second mixer 560, and the slow-axis phase modulator 320, the input end of the first mixer 540 is also connected to the slow-axis frequency stabilization control circuit 350, the output end of the first mixer 540 is connected to the first PID controller 550, and the output end of the first PID controller 550 is connected to the first optical frequency shifter 310 in the slow-axis control branch; the input end of the second mixer 560 is connected to the first digital frequency divider 530 and the fast-axis frequency stabilization control circuit 250, and the output end is connected to the second PID controller 570, and the output end of the second PID controller 570 is connected to the pump laser 110.

[0089] The external clock 510 is used as the system clock signal to provide the basic clock for the entire control circuit and is connected to the voltage-controlled oscillator 520. The voltage-controlled oscillator 520 provides a frequency source with a frequency of 1 GHz. Other mixing, phase detection, and electro-optical device driving operations are based on this frequency source. The first digital frequency divider 530 divides the frequency signal into four paths, which are respectively connected to the first mixer 540, the fast-axis phase modulator 210, the second mixer 560, and the slow-axis phase modulator 320. The first path signal and the detected slow-axis pump laser are mixed and phase-detected in the first mixer 540 to obtain the error signal. The signal is input into the first PID controller 550 to generate a driving signal for controlling the slow-axis optical frequency shifter, and the driving signal frequency is 200MHz; the second path directly drives the fast-axis phase modulator, and the third path directly drives the slow-axis phase modulator, which are used to generate the modulation signal required for PDH frequency stabilization; the first path signal and the detected slow-axis pump laser are mixed and phase-detected in the second mixer 560 to obtain an error signal which is input into the second PID controller 570. The second PID controller 570 generates a driving signal for controlling the pump laser, and the driving signal is an error signal close to DC.

[0090] In one embodiment, Figure 6 As shown, the local oscillator driver further includes: a second digital frequency divider 610, a third mixer 620, a fourth mixer 630, a third PID controller 640, a first DDS 650, a bias circuit 660, a subtractor 670 and a second DDS 680;

[0091] The second digital frequency divider 610 is used to divide the frequency signal generated by the voltage controlled oscillator 520;

[0092] The third mixer 620 is used for mixing and phase-detecting the output signal of the second digital frequency divider 610 and the output signal of the balanced detector 440 in the Brillouin frequency stabilization feedforward loop to obtain a first frequency shift signal;

[0093] The fourth mixer 630 is used for mixing and phase-detecting the follow-up frequency signal of the first DDS 650 and the first frequency-shifted signal to obtain a second frequency-shifted signal;

[0094] a third PID controller 640, configured to control the first DSS 650 according to the second frequency shift signal and output a control signal;

[0095] The first DDS 650 is used to receive the control signal output by the third PID controller and output a follow frequency signal;

[0096] A bias circuit 660, for generating a bias signal according to a temperature change of the Brillouin cavity;

[0097] a subtractor 670 for performing a subtraction operation on the bias signal generated by the bias circuit 660 and the control signal of the third PID controller 640 to obtain a low-frequency drift signal;

[0098] The second DDS 680 is used to load the low frequency drift signal to generate a radio frequency driving signal that follows the frequency drift caused by temperature, so as to control the optical frequency shifter in the Brillouin frequency stabilization feedforward loop to perform temperature drift compensation.

[0099] Among them, the input end of the second digital frequency divider 610 is connected to the voltage-controlled oscillator 520, the output end of the second digital frequency divider 610 is connected to the third mixer 620, the input end of the third mixer 620 is also connected to the balanced detector 440 in the Brillouin frequency stabilization feedforward loop, the output end of the third mixer 620 is connected to the input end of the fourth mixer 630, the input end of the fourth mixer 630 is also connected to the output end of the first DDS 650, the output end of the fourth mixer 630 is connected to the third PID controller 640, and the output end of the third PID controller 640 is respectively connected to the first DDS 650 and the subtractor 670; the input end of the subtractor 670 is also connected to the bias circuit, the output end of the subtractor 670 is connected to the input end of the second DDS 680, and the output end of the second DDS 680 is connected to the second optical frequency shifter 430 in the Brillouin frequency stabilization feedforward loop.

[0100] The external clock 510 is used as the system clock signal to provide the basic clock for the entire control circuit. The voltage-controlled oscillator 520 provides a frequency source with a frequency of 1 GHz. Other mixing, phase detection, and electro-optical device driving operations are based on this frequency source and are connected to the second digital frequency divider 610; the second digital frequency divider 610 generates a signal with a frequency of 250 MHz; the signal detected by the balanced detector 440 corresponds to the signal generated by the slow-axis optical frequency shifter, which is mixed with the signal generated by the second digital frequency divider 610 in the third mixer 620, and the frequency shift signal caused by the temperature drift is extracted and converted into a voltage signal, and a voltage-following phase-locked loop is introduced, that is, the first DDS 650 is set to a frequency of 50 MHz, and the fourth mixer 630 is used for phase detection, and then the following signal is output through the third PID controller 640 to control the first DDS The output frequency of 650 follows the frequency signal, and the output end of the third PID controller 640 enters the subtractor 670 together with the bias signal to obtain a low-frequency drift signal, which is loaded on the second DDS 680 to generate a RF drive signal that follows the frequency drift caused by temperature to control the second optical frequency shifter 430 to compensate for the temperature offset.

[0101] Figure 7 A schematic flow chart of a laser frequency self-stabilization method provided by an embodiment of the present invention, the method comprising:

[0102] S701, after the single-frequency laser output by the pump laser is divided into a fast-axis pump laser and a slow-axis pump laser by a polarization beam splitter;

[0103] S702, after frequency amplification and phase control of the fast-axis pump laser and the slow-axis pump laser respectively, the fast-axis pump laser and the slow-axis pump laser are input into the Brillouin cavity;

[0104] S703, generating a stimulated Brillouin effect based on the fast-axis pump laser and the slow-axis pump laser in the Brillouin cavity, and detecting the generated reverse Brillouin laser;

[0105] S704, calculating the frequency change caused by the Brillouin temperature drift according to the reverse Brillouin laser detected by the fast axis and the reverse Brillouin laser detected by the slow axis, and performing frequency feedforward compensation on the reverse Brillouin laser detected by the fast axis according to the frequency change, and outputting Brillouin laser with stable frequency;

[0106] S705, providing an electrical driving frequency signal for fast-axis pump laser regulation, slow-axis pump laser regulation, and phase-locked control of Brillouin laser feedforward compensation through a local oscillator driver.

[0107] It should be understood that the serial numbers of the steps in the above embodiments do not imply a sequence of execution, and the execution sequence of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0108] Those skilled in the art can clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and modules described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0109] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0110] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features thereof may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A Brillouin single-frequency laser, characterized in that: include: A pump laser for providing a single-frequency laser to stimulate the stimulated Brillouin effect; A polarization beam splitter, used for splitting the input single-frequency laser into a fast-axis pump laser and a slow-axis pump laser according to the polarization state; The fast axis control branch is used to control the phase of the fast axis pump laser, amplify the frequency and input it into the Brillouin cavity, and detect the fast axis reverse Brillouin laser; The slow axis control branch is used to control the phase of the slow axis pump laser, amplify the frequency and input it into the Brillouin cavity, and detect the slow axis reverse Brillouin laser; A Brillouin cavity, used for generating a stimulated Brillouin effect according to input fast-axis pump laser and slow-axis pump laser, and generating Brillouin laser; The Brillouin frequency stabilization feedforward loop is used to receive the reverse Brillouin laser detected by the fast-axis control branch and the slow-axis control branch, calculate the frequency change caused by the Brillouin temperature drift according to the reverse Brillouin laser, and perform frequency feedforward compensation on the fast-axis reverse Brillouin laser according to the frequency change, and output a Brillouin laser with stable frequency; The local oscillator driver is used to provide the electrical driving frequency signal required for the fast axis control branch, the slow axis control branch and the Brillouin frequency stabilization feedforward loop to realize phase-locked control.

2. The Brillouin single-frequency laser according to claim 1, characterized in that: The fast axis control branch includes a fast axis phase modulator, a fast axis optical amplifier, a fast axis optical circulator, a first polarization coupler, a second polarization coupler, a fast axis frequency stabilization control circuit, a fast axis coupler and a fast axis optical power feedback circuit; The fast axis phase modulator is used to perform phase modulation on the fast axis pump laser; The fast axis optical amplifier is used to increase the fast axis pump laser power to achieve the optical power required for stimulated Brillouin. The fast axis optical circulator is used for laser signal transmission; Wherein, the first port of the fast axis optical circulator is connected to the fast axis optical amplifier, the second port is connected to the first polarization coupler, and the third port is connected to the fast axis coupler; The first polarization coupler is used to couple fast-axis pump lasers of different polarization states and output them to the Brillouin cavity; and to receive reverse Brillouin lasers generated by the Brillouin cavity; The second polarization coupler is used to receive the fast-axis pump laser that passes through the Brillouin cavity and is affected by the Brillouin effect, and transmit the fast-axis pump laser to the fast-axis frequency stabilization control circuit; The fast-axis frequency stabilization control circuit is used to adjust the fast-axis phase modulator based on the PDH frequency stabilization principle according to the detected light field phase change of the fast-axis pump laser; The fast axis coupler is used to split the reverse Brillouin laser beam transmitted from the fast axis optical circulator, connect the low splitting ratio end to the fast axis power feedback circuit, and output the high splitting ratio end as the fast axis reverse Brillouin laser. The fast axis optical power feedback circuit is used to feedback control the power of the fast axis optical amplifier according to the power jitter of the reverse Brillouin laser at the low splitting ratio end of the fast axis coupler, so as to stabilize the fast axis pump laser.

3. The Brillouin single-frequency laser according to claim 1, characterized in that: The slow axis control branch includes a first optical frequency shifter, a slow axis phase modulator, a slow axis optical amplifier, a slow axis optical circulator, a first polarization coupler, a second polarization coupler, a slow axis frequency stabilization controller circuit, a slow axis coupler and a slow axis optical power feedback circuit; The first optical frequency shifter is used to generate a fixed frequency offset under the control of a local oscillator driver; The slow axis phase modulator is used to perform phase modulation on the slow axis pump laser; The slow axis optical amplifier is used to increase the slow axis pump laser power to achieve the optical power required for stimulated Brillouin. The slow axis optical circulator is used for laser signal transmission; Wherein, the first port of the slow axis optical circulator is connected to the slow axis optical amplifier, the second port is connected to the second polarization coupler, and the third port is connected to the slow axis coupler; The second polarization coupler is further used to couple slow-axis pump lasers of different polarization states and output them to the Brillouin cavity; and to receive reverse Brillouin lasers generated by the Brillouin cavity; The first polarization coupler is also used to receive the slow axis pump laser that passes through the Brillouin cavity and is affected by the Brillouin effect; The slow-axis frequency stabilization control circuit is used to adjust the slow-axis phase modulator based on the PDH frequency stabilization principle according to the detected light field phase change of the slow-axis pump laser; The slow axis coupler is used to split the reverse Brillouin laser beam transmitted from the slow axis optical circulator, connect the low splitting ratio end to the slow axis optical power feedback circuit, and output the high splitting ratio end as the slow axis reverse Brillouin laser. The slow axis optical power feedback circuit is used to feedback control the power of the slow axis optical amplifier according to the power jitter of the reverse Brillouin laser at the low splitting ratio end of the slow axis coupler to stabilize the slow axis pump laser.

4. The Brillouin single-frequency laser according to claim 1, characterized in that: The Brillouin frequency stabilization feedforward loop includes an optical beam splitter, an optical coupler, a balanced detector, a second optical frequency shifter, an optical mixer and a local oscillator driver; The optical beam splitter is used to split the fast-axis reverse Brillouin laser, input the first split beam as the Brillouin laser to be frequency-stabilized into the second optical frequency shifter, and input the second split beam together with the slow-axis reverse Brillouin laser into the optical coupler; The optical coupler is used to couple the second beam split of the fast-axis reverse Brillouin laser to the slow-axis reverse Brillouin laser; The second optical frequency shifter is used to receive the Brillouin laser to be frequency-stabilized and the local oscillator driver control signal transmitted by the optical beam splitter, and output the frequency-stabilized Brillouin laser; The balanced detector is used to convert the Brillouin cavity jitter signal caused by temperature into a voltage signal through optical heterodyne detection, and output it to the optical mixer; The optical mixer is used to mix the voltage signal transmitted by the balanced detector with the control signal output by the local oscillator driver to obtain a frequency error signal corresponding to the temperature change, and load the frequency error signal to the electrical signal of the local oscillator driver driving the second optical frequency shifter to control the operating frequency of the second optical frequency shifter and compensate for temperature drift.

5. The Brillouin single-frequency laser according to claim 4, characterized in that: The beam splitting ratio between the first beam splitter and the second beam splitter in the optical beam splitter is 9:

1.

6. The Brillouin single-frequency laser according to claim 1, characterized in that: The output end of the local oscillator driver is connected to the pump laser to provide a driving signal for the pump laser.

7. The Brillouin single-frequency laser according to claim 6, characterized in that: The local oscillator driver includes an external clock, a voltage-controlled oscillator, a first digital frequency divider, a first mixer, a first PID controller, a second mixer and a second PID controller; The external clock is used to provide a basic clock signal; The voltage-controlled oscillator is used to provide a frequency signal of a predetermined frequency as a frequency source; The first digital frequency divider is used to divide the frequency signal; Wherein, the output end of the first digital frequency divider is connected to the first mixer, the fast axis phase modulator, the second mixer, and the slow axis phase modulator respectively; The first mixer is used for mixing and phase-detecting the output signal of the first digital frequency divider and the signal of the slow-axis frequency stabilization control circuit to obtain an error signal and output it to the first PID controller; The slow axis frequency stabilization control circuit is located in the slow axis regulation branch, and is used to output a slow axis phase regulation signal based on the PDH frequency stabilization principle according to the detected light field phase change of the slow axis pump laser; The first PID controller is used to generate a driving signal for controlling the optical frequency shifter in the slow axis control branch according to the error signal; The second mixer is used for mixing and phase-detecting the output signal of the first digital frequency divider and the signal of the fast-axis frequency stabilization control circuit to obtain an error signal and output it to the second PID controller; The fast-axis frequency stabilization control circuit is located in the fast-axis regulation branch, and is used to output a fast-axis phase regulation signal based on the PDH frequency stabilization principle according to the detected optical field phase change of the fast-axis pump laser; The second PID controller is used to generate a driving signal for controlling the pump laser according to the error signal.

8. The Brillouin single-frequency laser according to claim 7, characterized in that: The voltage-controlled oscillator provides a frequency signal of 1 GHz, the frequency division coefficient of the first digital frequency divider is 5, and the generated signal frequency is 200 MHz.

9. The Brillouin single-frequency laser according to claim 7, characterized in that: The local oscillator driver further includes: a second digital frequency divider, a third mixer, a fourth mixer, a third PID controller, a first DDS, a bias circuit, a subtractor and a second DDS; The second digital frequency divider is used to divide the frequency signal generated by the voltage-controlled oscillator; The third mixer is used for mixing and phase-detecting the output signal of the second digital frequency divider and the output signal of the balanced detector in the Brillouin frequency stabilization feedforward loop to obtain a first frequency shift signal; The fourth mixer is used for mixing and phase-detecting the follow-up frequency signal of the first DDS and the first frequency-shifted signal to obtain a second frequency-shifted signal; a third PID controller, configured to control the first DSS according to the second frequency shift signal and output a control signal; The first DDS is used to receive the control signal output by the third PID controller and output a follow-up frequency signal; A bias circuit, used for generating a bias signal according to a temperature change of the Brillouin cavity; a subtractor, configured to perform a subtraction operation on a bias signal generated by the bias circuit and a control signal output by the third PID controller to obtain a low-frequency drift signal; The second DDS is used to load the low-frequency drift signal to generate a radio frequency drive signal that follows the frequency drift caused by temperature, so as to control the optical frequency shifter in the Brillouin frequency stabilization feedforward loop to compensate for the temperature drift.

10. A method for self-stabilizing laser frequency using the Brillouin single-frequency laser according to any one of claims 1 to 9, characterized in that: include: After the single-frequency laser output by the pump laser is split into a fast-axis pump laser and a slow-axis pump laser by a polarization beam splitter; After phase control and frequency amplification of the fast-axis pump laser and the slow-axis pump laser respectively, the fast-axis pump laser and the slow-axis pump laser are input into the Brillouin cavity; In the Brillouin cavity, a stimulated Brillouin effect is generated based on the fast-axis pump laser and the slow-axis pump laser, and the generated reverse Brillouin laser is detected; The frequency change caused by the Brillouin temperature drift is calculated according to the reverse Brillouin laser detected by the fast axis and the reverse Brillouin laser detected by the slow axis, and the frequency feedforward compensation is performed on the reverse Brillouin laser detected by the fast axis according to the frequency change to output the Brillouin laser with stable frequency; The local oscillator driver provides an electrical driving frequency signal for fast-axis pump laser regulation, slow-axis pump laser regulation and phase-locked control of Brillouin laser feedforward compensation.

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