Fiber FP cavity frequency control device and control method

Abstract

The present application belongs to the technical field of optical resonant cavity frequency stabilization, and discloses a kind of optical fiber FP cavity frequency control device and control method, device includes laser, electro-optic phase modulator, feedback control system, reference FP cavity, first photoelectric detector;Two cavity mirrors of optical fiber FP cavity are fixed on the two cavity mirrors of reference FP cavity respectively, and first piezoelectric driver is arranged on one cavity mirror of reference FP cavity;The light output end of laser is connected with the light input end of reference FP cavity through electro-optic phase modulator, and the output signal of reference FP cavity is sent to feedback control system after being detected and photoelectric converted by first photoelectric detector;Feedback control system is used to control first piezoelectric driver according to the transmission signal of reference FP cavity, and the cavity length of reference FP cavity is locked.The present application can realize the indirect locking of optical fiber FP cavity, and avoid the interference of additional optical field to the material system in optical fiber FP cavity.

Description

Technical Field

[0001] This invention belongs to the field of optical resonant cavity frequency stabilization technology, specifically relating to an optical fiber FP cavity frequency control device and control method. Background Technology

[0002] Optical resonant cavities play a crucial role in quantum optics and quantum information, particularly in cavity quantum electrodynamics (CQED) systems. In these systems, the interaction between light and matter can be effectively enhanced within a confined space, enabling precise control of quantum systems such as single photons and single atoms. These systems hold broad application prospects in quantum information processing, quantum precision measurement, and quantum networks. Fiber optic FP (Fabry-Perot) cavities, typically composed of highly reflective dielectric mirrors fabricated from the end faces of two optical fibers, offer advantages such as small mode volume, high quality factor, and ease of integration with fiber optic systems. They enable efficient optical field confinement and enhancement and have been widely applied in experimental research on various quantum systems, including cold atoms, ions, solid-state emitters, and optomechanical systems.

[0003] In the aforementioned applications, the frequency stability and precise control of the fiber optic FP cavity are crucial for achieving strong coupling and high-fidelity quantum manipulation. Typically, the cavity's resonant frequency needs to be precisely tuned to match the atomic transition frequency or maintained in a controllable detuned state. In cavity quantum electrodynamics experiments, traditional PDH locking methods usually require directly injecting locking light into the experimental fiber cavity to obtain error signals. This method inevitably introduces an additional optical field into the cavity, thereby perturbing the atoms or other quantum matter systems within the cavity and affecting the accuracy of experimental results and the fidelity of quantum states. Therefore, how to achieve frequency stability control of the fiber optic FP cavity without injecting locking light is a pressing technical problem that needs to be solved in this field. Summary of the Invention

[0004] To address the technical problem that existing technologies require the introduction of additional optical fields to achieve FP cavity frequency control, which leads to disturbances in the intracavity atoms or other quantum matter systems, affecting the accuracy of experimental results and the fidelity of quantum states, this invention proposes an optical fiber FP cavity frequency control device and method. This method achieves optical fiber FP cavity frequency control through indirect locking, thereby avoiding interference from additional light on the intracavity material system of the optical fiber FP cavity.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: a fiber optic FP cavity frequency control device, comprising: a laser, an electro-optic phase modulator, a feedback control system, a reference FP cavity, and a first photodetector; The fiber optic FP cavity includes a first cavity mirror and a second cavity mirror, and the reference FP cavity includes a third cavity mirror and a fourth cavity mirror; the first cavity mirror is fixedly connected to the third cavity mirror through a first fixing structure, and the second cavity mirror is fixedly connected to the fourth cavity mirror through a second fixing structure; the fourth cavity mirror is provided with a first piezoelectric actuator for adjusting the cavity length of the reference FP cavity; The optical output terminal of the laser is connected to the optical input terminal of the electro-optic phase modulator, and the optical output terminal of the electro-optic phase modulator is connected to the optical input terminal of the reference FP cavity. The output signal of the reference FP cavity is detected and photoelectrically converted by the first photodetector and then sent to the electrical input terminal of the feedback control system. The first electrical output terminal of the feedback control system is connected to the electrical input terminal of the first piezoelectric driver, and the second electrical output terminal is connected to the electrical input terminal of the electro-optic phase modulator. The feedback control system is used to drive the electro-optic phase modulator to perform phase modulation on the laser at the optical input end of the reference FP cavity, so that the laser generates modulation sidebands for generating error signals; it is also used to generate error signals based on the output signal of the first photodetector under phase modulation conditions and convert them into feedback control signals to be sent to the first piezoelectric driver to lock the cavity length of the reference FP cavity, thereby indirectly locking the frequency of the fiber optic FP cavity.

[0006] The fiber optic FP cavity frequency control device further includes a regulated power supply. A second piezoelectric driver is provided on the third cavity mirror. The electrical input terminal of the second piezoelectric driver is connected to the electrical output terminal of the regulated power supply for static adjustment of the reference FP cavity length.

[0007] The fiber optic FP cavity frequency control device further includes a vibration isolation base, the second piezoelectric actuator and the first piezoelectric actuator are fixed on the vibration isolation base, and the fourth cavity mirror is fixedly connected to the first piezoelectric actuator and is mounted on the vibration isolation base through the first piezoelectric actuator. The third cavity mirror is fixedly connected to the second piezoelectric actuator and is mounted on the vibration isolation base via the second piezoelectric actuator; The reference FP cavity is a lens cavity, and the second piezoelectric actuator and the first piezoelectric actuator are piezoelectric ceramics.

[0008] The fiber optic FP cavity frequency control device further includes a signal source and an optical field modulator disposed between an electro-optic phase modulator and a reference FP cavity. The optical field modulator is used to modulate the laser frequency entering the reference FP cavity under the drive of the signal source, thereby realizing the adjustment of the cavity-locking frequency of the fiber optic FP cavity.

[0009] The electro-optic phase modulator is a free-space electro-optic phase modulator, and the optical field modulator is an optical fiber electro-optic phase modulator.

[0010] The fiber optic FP cavity frequency control device further includes a beam splitter unit, a polarization controller, a second photodetector, and an oscilloscope. The optical output terminal of the laser is connected to the optical input terminal of the beam splitter unit, the first optical output terminal of the beam splitter unit is connected to the optical input terminal of the polarization controller, the optical output terminal of the polarization controller is connected to the optical input terminal of the fiber optic FP cavity, and the output signal of the fiber optic FP cavity is detected and photoelectrically converted by the second photodetector before being sent to the oscilloscope. The second optical output terminal of the beam splitter unit is connected to the optical input terminal of the electro-optic phase modulator. The oscilloscope is used to receive and display the detection signals of the first and second photodetectors.

[0011] The surfaces of the first fixing structure and the second fixing structure are provided with V-shaped grooves. The first cavity mirror is fixed in the V-shaped groove on the surface of the first fixing structure by the first adhesive layer. The first fixing structure is fixedly connected to the third cavity mirror by the second adhesive layer. The second cavity mirror is fixed in the V-shaped groove on the surface of the second fixing structure by the first adhesive layer, and the second fixing structure is fixedly connected to the fourth cavity mirror by the second adhesive layer; the materials of the first fixing structure and the second fixing structure are quartz.

[0012] The feedback control system includes: a modulation signal generation module, a signal demodulation module, a filtering module, and a PID control module; The modulation signal generation module is used to output a modulation reference signal to the electro-optic phase modulator; the signal demodulation module is used to mix the transmission signal sent by the first photodetector according to the modulation reference signal, and the resulting mixed signal is filtered by the filtering module to extract the low frequency component to obtain an error signal; the PID control module is used to generate a feedback control signal according to the error signal and send it to the first piezoelectric driver to lock the cavity length of the reference FP cavity.

[0013] Furthermore, the present invention also provides a fiber optic FP cavity frequency control method, implemented based on the aforementioned fiber optic FP cavity frequency control device, comprising the following steps: Step 1: Turn on the laser and the spatial electro-optic phase modulator, and modulate the laser at the light incident end of the reference FP cavity through the spatial electro-optic phase modulator; Step 2: The cavity length of the reference FP cavity is locked by outputting a feedback control signal through the feedback control system, thereby realizing the optical injection frequency locking of the fiber FP cavity.

[0014] The fiber optic FP cavity frequency control method further includes the following steps: splitting a portion of the laser output beam and injecting it into the fiber optic FP cavity; receiving the output signal of the fiber optic FP cavity through a second photodetector, and observing the detection signals of the first and second photodetectors through an oscilloscope; Simultaneously, an optical field modulator is set between the electro-optic phase modulator and the reference FP cavity to shift the frequency of the laser at the incident end of the reference FP cavity; the driving frequency of the optical field modulator is changed, and the peak offset of the detection signals of the first photodetector and the second photodetector is observed with an oscilloscope until the peak offset reaches the set value. The cavity length of the reference FP cavity is locked through step 2 to realize the offset control of the cavity locking frequency of the fiber optic FP cavity relative to the laser output frequency of the laser.

[0015] Compared with the prior art, the present invention has the following advantages: This invention proposes a fiber optic FP cavity frequency control device and method. By introducing a reference FP cavity to indirectly lock the fiber FP cavity, not only can the frequency control of the fiber FP cavity be realized, but also the interference of the additional optical field introduced by the lock on the material system inside the fiber FP cavity can be avoided. For example, the atomic dynamic Stark frequency shift, photon scattering and heating effects caused by the lock light can be avoided. In addition, this invention does not require complex optical path components to separate the lock light, thus reducing the detection background noise and improving the control accuracy. Furthermore, its structure is simple, the frequency locking accuracy is high, and it is easy to implement. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of an optical fiber FP cavity frequency control device provided in Embodiment 1 of the present invention; Figure 2 This is another structural schematic diagram of an optical fiber FP cavity frequency control device provided in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the first fixing structure in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the feedback control system in Embodiment 1 of the present invention; Figure 5 This is a schematic diagram of the signal when the fiber FP cavity and the reference FP cavity are locked simultaneously. Curve a is the frequency discrimination signal curve, curves b and c are the transmission curves of the fiber FP cavity and the reference FP cavity after locking, respectively, and curves d and e are the transmission curves of the fiber FP cavity and the reference FP cavity before locking, respectively. Figure 6 The transmittance curves of the fiber FP cavity obtained at different driving frequencies of the optical field modulator 16 are shown. Explanation of reference numerals in the attached figures: 1 is the first cavity mirror, 2 is the second cavity mirror, 3 is the first fixed structure, 4 is the second fixed structure, 5 is the third cavity mirror, 6 is the fourth cavity mirror, 7 is the second piezoelectric actuator, 8 is the first piezoelectric actuator, 9 is the vibration isolation base, 10 is the laser, 11 is the beam splitting unit, 12 is the first laser, 13 is the second laser, 14 is the electro-optic phase modulator, 15 is the polarization controller, 16 is the optical field modulator, 17 is the signal source, 18 is the regulated power supply, 19 is the feedback control system, 20 is the second photodetector, 21 is the first photodetector, and 22 is the oscilloscope. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example 1 like Figure 1 As shown, Embodiment 1 of the present invention provides a fiber optic FP cavity frequency control device, including: a laser 10, an electro-optic phase modulator 14, a feedback control system 19, a reference FP cavity, and a first photodetector 21; the fiber optic FP cavity includes a first cavity mirror 1 and a second cavity mirror 2, and the reference FP cavity includes a third cavity mirror 5 and a fourth cavity mirror 6; the first cavity mirror 1 is fixedly connected to the third cavity mirror 5 through a first fixing structure 3, and the second cavity mirror 2 is fixedly connected to the fourth cavity mirror 6 through a second fixing structure 4; the fourth cavity mirror 6 is provided with a first piezoelectric actuator 8 for adjusting the cavity length of the reference FP cavity.

[0019] The optical output terminal of the laser 10 is connected to the optical input terminal of the electro-optic phase modulator 14, and the optical output terminal of the electro-optic phase modulator 14 is connected to the optical input terminal of the reference FP cavity. The output signal of the reference FP cavity is detected and photoelectrically converted by the first photodetector 21 and then sent to the electrical input terminal of the feedback control system 19. The first electrical output terminal of the feedback control system 19 is connected to the electrical input terminal of the first piezoelectric driver 8, and the second electrical output terminal is connected to the electrical input terminal of the electro-optic phase modulator 14.

[0020] The feedback control system 19 is used to drive the electro-optic phase modulator 14 to perform phase modulation on the laser at the optical input end of the reference FP cavity, so that the laser generates a modulation sideband for generating an error signal; it is also used to generate an error signal based on the output signal of the first photodetector 21 under the phase modulation condition, and to convert the error signal into a feedback control signal and send it to the first piezoelectric driver 8 to lock the cavity length of the reference FP cavity, thereby indirectly locking the frequency of the fiber optic FP cavity.

[0021] Furthermore, the fiber optic FP cavity frequency control device of this embodiment also includes a regulated power supply 18. A second piezoelectric driver 7 is provided on the third cavity mirror 5. The electrical input terminal of the second piezoelectric driver 7 is connected to the electrical output terminal of the regulated power supply 18 for static compensation of the reference FP cavity length, so as to make up for the limited cavity length adjustment range of the feedback modulation system 19.

[0022] Furthermore, the fiber optic FP cavity frequency control device further includes a vibration isolation base 9, the second piezoelectric actuator 7 and the first piezoelectric actuator 8 are fixed on the vibration isolation base 9, the fourth cavity mirror 6 is fixedly connected to the first piezoelectric actuator 8 and is mounted on the vibration isolation base 9 through the first piezoelectric actuator 8; the third cavity mirror 5 is fixedly connected to the second piezoelectric actuator 7 and is mounted on the vibration isolation base 9 through the second piezoelectric actuator 7.

[0023] Furthermore, in this embodiment, the reference FP cavity is a lens cavity, and the third cavity mirror 5 and the fourth cavity mirror 6 are lens cavity mirrors. The second piezoelectric actuator 7 and the first piezoelectric actuator 8 are piezoelectric ceramics.

[0024] Furthermore, the fiber optic FP cavity frequency control device further includes a signal source 17 and an optical field modulator 16 disposed between the electro-optic phase modulator 14 and the reference FP cavity. The electrical output terminal of the signal source 17 is connected to the electrical input terminal of the optical field modulator 16. The optical field modulator 16 is used to modulate the optical field entering the reference FP cavity under the drive of the signal source 17, causing its frequency to shift, thereby realizing the adjustment of the locked frequency of the fiber optic FP cavity.

[0025] Specifically, in this embodiment, the electro-optic phase modulator 14 is a free-space electro-optic phase modulator, and the optical field modulator 16 is an optical fiber electro-optic phase modulator.

[0026] To observe the locking effect of the fiber FP cavity, such as Figure 2As shown, this embodiment of a fiber optic FP cavity frequency control device further includes a beam splitter 11, a polarization controller 15, a second photodetector 20, and an oscilloscope 22. The optical output terminal of the laser 10 is connected to the optical input terminal of the beam splitter 11. The first and second optical output terminals of the beam splitter 11 output a first laser 12 and a second laser 13, respectively. The first laser 12 is injected into the fiber optic FP cavity to observe the locking effect, and the second laser 13 is modulated and injected into a reference FP cavity. Specifically, the first optical output terminal of the beam splitter 11 is connected to the optical input terminal of the polarization controller 15, and the optical output terminal of the polarization controller 15 is connected to the optical input terminal of the fiber optic FP cavity. The output signal of the fiber optic FP cavity is detected and photoelectrically converted by the second photodetector 20 and then sent to the oscilloscope 22. The second optical output terminal of the beam splitter 11 is connected to the optical input terminal of the electro-optic phase modulator 14. The oscilloscope 22 is used to receive and display the detection signals of the first photodetector 21 and the second photodetector 20.

[0027] It should be noted that, in practice, after locking the fiber FP cavity, the first laser 12 entering the fiber FP cavity can be directly shut off, achieving optical injection-free locking of the fiber FP cavity. Furthermore, although the above... Figure 1 and Figure 2 The first photodetector 21 and the second photodetector 20 detect the transmitted signal of the corresponding cavity. In this embodiment, the first photodetector 21 and the second photodetector 20 can also detect the reflected signal of the corresponding cavity. In this case, an optical path splitter needs to be set at the optical input end of the cavity. Under the above teachings, those skilled in the art know how to set the optical path splitter to realize the detection of the reflected signal of the fiber FP cavity and the reference FP cavity.

[0028] Furthermore, such as Figure 3 As shown, in this embodiment, the surface of the first fixing structure 3 is provided with a V-shaped groove. The first laparoscope 1 is fixed in the V-shaped groove on the surface of the first fixing structure 3 by a first adhesive layer. The first fixing structure 3 is fixedly connected to the third laparoscope 5 by a second adhesive layer. The second fixing structure 4 has the same structure as the first fixing structure 3. Specifically, the surface of the second fixing structure 4 is provided with a V-shaped groove. The second laparoscope 2 is fixed in the V-shaped groove on the surface of the second fixing structure 4 by a first adhesive layer. The second fixing structure 4 is fixedly connected to the fourth laparoscope 6 by a second adhesive layer. Furthermore, the material of the first fixing structure 3 and the second fixing structure 4 is quartz.

[0029] In this embodiment, since the fiber FP cavity and the reference FP cavity share the first piezoelectric driver 8 for cavity locking, the cavity length of the fiber FP cavity is locked synchronously when the cavity length of the reference FP cavity is locked, thereby achieving indirect frequency locking of the fiber FP cavity; wherein, the modulation laser used for locking is injected only into the reference FP cavity and does not enter the fiber FP cavity, which can avoid interference of additional injected light on the material system inside the fiber FP cavity during the locking process.

[0030] Furthermore, such as Figure 4 As shown, in this embodiment, the feedback control system 19 includes: a modulation signal generation module, a signal demodulation module, a filtering module, and a PID control module; wherein, the modulation signal generation module is used to output a modulation reference signal to the electro-optic phase modulator 14; the signal demodulation module is used to mix the detection signal sent by the first photodetector 21 according to the modulation reference signal, and the resulting mixed signal is filtered by the filtering module to extract the low-frequency component to obtain an error signal; the PID control module is used to generate a feedback control signal according to the error signal and send it to the first piezoelectric driver 8, thereby locking the cavity length of the reference FP cavity.

[0031] Example 2 Embodiment 2 of the present invention provides a fiber optic FP cavity frequency control method, which is implemented based on the fiber optic FP cavity frequency control device described in Embodiment 1, and includes the following steps: Step 1: Turn on the laser 10 and the spatial electro-optic phase modulator 14, and modulate the laser at the light incident end of the reference FP cavity through the spatial electro-optic phase modulator 14; Step 2: The cavity length of the reference FP cavity is locked by outputting a feedback control signal through the feedback control system 19, thereby realizing the frequency locking of the fiber FP cavity without light injection.

[0032] Furthermore, the fiber optic FP cavity frequency control method further includes the following steps: A portion of the output beam from the laser 10 is split off, and the split beam is polarized by the polarization controller 15 and then injected into the fiber FP cavity. The output signal of the fiber FP cavity is received by the second photodetector 20, and the detection signals of the first photodetector 21 and the second photodetector 20 are observed by the oscilloscope 22. Simultaneously, an optical field modulator 16 is positioned between the electro-optic phase modulator 14 and the reference FP cavity to frequency-shift the laser at the incident end of the reference FP cavity. The optical field modulator 16 is driven by a signal source 17. The driving frequency of the optical field modulator 16 is changed, and the peak offset of the detection signals of the first photodetector 21 and the second photodetector 20 is observed using an oscilloscope 22 until the peak offset reaches the frequency offset set value Δν1. Then, the cavity length of the reference FP cavity is locked through step 2, thereby controlling the offset Δν2 of the cavity-locking frequency of the fiber optic FP cavity relative to the laser frequency output by the laser 10. Here, Δν1 = Δν2. For example, if it is necessary to make the cavity-locking frequency of the fiber optic FP cavity resonate with the laser frequency output by the laser 10, the driving frequency of the optical field modulator 16 can be changed, and the peak offset of the detection signals of the first photodetector 21 and the second photodetector 20 can be observed using an oscilloscope 22 until the peak offset is zero.

[0033] In this embodiment, assuming the output laser frequency of laser 10 is ν0, and the driving frequencies of electro-optic phase modulator 14 and optical field modulator 16 are f1 and f2 respectively, after modulation by electro-optic phase modulator 14, the laser becomes the main peak of frequency ν0 and the sideband of frequency ν0±f1. After passing through optical field modulator 16, the laser becomes the main peak of frequency ν0+f2 and the sideband of frequency ν0+f2±f1. Through feedback control system 19, the frequency of reference FP cavity can be locked at ν0+f2. Since the cavity length of fiber FP cavity is related to the cavity length of reference FP cavity, there is a definite offset relationship between their frequencies. Assuming the offset between the cavity length of fiber FP cavity and the frequency of reference FP cavity is f3, it is equivalent to the frequency of fiber FP cavity being locked at ν0+f2-f3. Therefore, by adjusting the driving frequency f2 of optical field modulator 16 to be equal to f3, the locked frequency of fiber FP cavity can be made equal to the output laser frequency ν0 of laser 10. At this time, the transmittance of fiber FP cavity to output laser 10 is the highest.

[0034] like Figure 5 The diagram shows the signal when the fiber FP cavity and the reference FP cavity are simultaneously locked. Curve a is the frequency discrimination signal curve, curves b and c are the transmission curves of the fiber FP cavity and the reference FP cavity after locking, respectively, and curves d and e are the transmission curves of the fiber FP cavity and the reference FP cavity before locking, respectively. Figure 5 As can be seen, in the locked state, the transmittance within the fiber FP cavity can be maintained at a relatively constant level. The frequency of the modulation reference signal output by the feedback control system 19 is 19.78MHz.

[0035] like Figure 6As shown, the transmittance curve of the fiber FP cavity obtained by changing the driving frequency of the optical field modulator 16 conforms to the Lorentz distribution. It can be seen from the figure that the present invention can achieve precise control of the frequency of the fiber FP cavity.

[0036] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A fiber optic FP cavity frequency control device, characterized in that, include: Laser (10), electro-optic phase modulator (14), feedback control system (19), reference FP cavity, first photodetector (21); The fiber optic FP cavity includes a first cavity mirror (1) and a second cavity mirror (2), and the reference FP cavity includes a third cavity mirror (5) and a fourth cavity mirror (6); the first cavity mirror (1) is fixedly connected to the third cavity mirror (5) through a first fixing structure (3), and the second cavity mirror (2) is fixedly connected to the fourth cavity mirror (6) through a second fixing structure (4); the fourth cavity mirror (6) is provided with a first piezoelectric actuator (8) for adjusting the cavity length of the reference FP cavity. The optical output terminal of the laser (10) is connected to the optical input terminal of the electro-optic phase modulator (14), the optical output terminal of the electro-optic phase modulator (14) is connected to the optical input terminal of the reference FP cavity, and the output signal of the reference FP cavity is sent to the electrical input terminal of the feedback control system (19) after being detected and photoelectrically converted by the first photodetector (21); the first electrical output terminal of the feedback control system (19) is connected to the electrical input terminal of the first piezoelectric driver (8), and the second electrical output terminal is connected to the electrical input terminal of the electro-optic phase modulator (14); The feedback control system (19) is used to drive the electro-optic phase modulator (14) to perform phase modulation on the laser at the optical input end of the reference FP cavity, so that the laser generates a modulation sideband for generating an error signal; it is also used to generate an error signal based on the output signal of the first photodetector (21) under phase modulation conditions and convert it into a feedback control signal before sending it to the first piezoelectric driver (8) to lock the cavity length of the reference FP cavity, thereby indirectly locking the frequency of the fiber FP cavity.

2. The fiber optic FP cavity frequency control device according to claim 1, characterized in that, It also includes a regulated power supply (18), and a second piezoelectric actuator (7) is provided on the third cavity mirror (5). The electrical input terminal of the second piezoelectric actuator (7) is connected to the electrical output terminal of the regulated power supply (18) for statically adjusting the cavity length of the reference FP cavity.

3. The fiber optic FP cavity frequency control device according to claim 2, characterized in that, It also includes a vibration isolation base (9), the second piezoelectric actuator (7) and the first piezoelectric actuator (8) are fixed on the vibration isolation base (9), and the fourth cavity mirror (6) is fixedly connected to the first piezoelectric actuator (8) and is set on the vibration isolation base (9) through the first piezoelectric actuator (8); The third cavity mirror (5) is fixedly connected to the second piezoelectric actuator (7) and is mounted on the vibration isolation base (9) through the second piezoelectric actuator (7); The reference FP cavity is a lens cavity, and the second piezoelectric actuator (7) and the first piezoelectric actuator (8) are piezoelectric ceramics.

4. The fiber optic FP cavity frequency control device according to claim 1, characterized in that, It also includes a signal source (17) and an optical field modulator (16) disposed between the electro-optic phase modulator (14) and the reference FP cavity. The optical field modulator (16) is used to adjust the locked frequency of the fiber optic FP cavity by modulating the laser at the light incident end of the reference FP cavity under the drive of the signal source (17).

5. The fiber optic FP cavity frequency control device according to claim 4, characterized in that, The electro-optic phase modulator (14) is a free-space electro-optic phase modulator, and the optical field modulator (16) is an optical fiber electro-optic phase modulator.

6. The fiber optic FP cavity frequency control device according to claim 1, characterized in that, It also includes a beam splitter (11), a polarization controller (15), a second photodetector (20), and an oscilloscope (22); the optical output end of the laser (10) is connected to the optical input end of the beam splitter (11), the first optical output end of the beam splitter (11) is connected to the optical input end of the polarization controller (15), and the optical output end of the polarization controller (15) is connected to the optical input end of the fiber FP cavity; the output signal of the fiber FP cavity is detected and photoelectrically converted by the second photodetector (20) and then sent to the oscilloscope (22); the second optical output end of the beam splitter (11) is connected to the optical input end of the electro-optic phase modulator (14); the oscilloscope (22) is used to receive and display the detection signals of the first photodetector (21) and the second photodetector (20).

7. The fiber optic FP cavity frequency control device according to claim 1, characterized in that, The surfaces of the first fixing structure (3) and the second fixing structure (4) are provided with V-shaped grooves. The first cavity mirror (1) is fixed in the V-shaped groove on the surface of the first fixing structure (3) by the first adhesive layer. The first fixing structure (3) is fixedly connected to the third cavity mirror (5) by the second adhesive layer. The second cavity mirror (2) is fixed in the V-shaped groove on the surface of the second fixing structure (4) by the first adhesive layer, and the second fixing structure (4) is fixedly connected to the fourth cavity mirror (6) by the second adhesive layer; the materials of the first fixing structure (3) and the second fixing structure (4) are quartz.

8. The fiber optic FP cavity frequency control device according to claim 1, characterized in that, The feedback control system (19) includes: a modulation signal generation module, a signal demodulation module, a filtering module and a PID control module; The modulation signal generation module is used to output a modulation reference signal to the electro-optic phase modulator (14); the signal demodulation module is used to mix the detection signal sent by the first photodetector (21) according to the modulation reference signal, and the resulting mixed signal is filtered by the filtering module to extract the low frequency component to obtain an error signal; the PID control module is used to generate a feedback control signal according to the error signal and send it to the first piezoelectric driver (8) to lock the cavity length of the reference FP cavity.

9. A fiber optic FP cavity frequency control method, implemented based on the fiber optic FP cavity frequency control device according to any one of claims 1-8, characterized in that, Includes the following steps: Step 1: Turn on the laser (10) and the spatial electro-optic phase modulator (14), and modulate the laser at the light incident end of the reference FP cavity through the spatial electro-optic phase modulator (14); Step 2: The cavity length of the reference FP cavity is locked by outputting a feedback control signal through the feedback control system (19), thereby realizing the optical injection frequency lock of the fiber FP cavity.

10. The fiber optic FP cavity frequency control method according to claim 9, characterized in that, It also includes the following steps: A portion of the output beam of the laser (10) is injected into the fiber FP cavity; the output signal of the fiber FP cavity is received by the second photodetector (20), and the detection signals of the first photodetector (21) and the second photodetector (20) are observed by the oscilloscope (22); Meanwhile, an optical field modulator (16) is set between the electro-optic phase modulator (14) and the reference FP cavity to offset the frequency of the laser at the incident end of the reference FP cavity; the driving frequency of the optical field modulator (16) is changed, and the peak offset of the detection signals of the first photodetector (21) and the second photodetector (20) is observed by an oscilloscope (22) until the peak offset reaches the set value. Then, the cavity length of the reference FP cavity is locked through step 2 to realize the offset control of the cavity locking frequency of the fiber optic FP cavity relative to the laser frequency output by the laser (10).

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