System and method for locking cavity length of Fabry-Perot cavity and stabilizing laser frequency

Abstract

The invention discloses a cavity length locking and laser frequency stabilization system and method of a Fabry-Perot cavity. The cavity length locking system of the Fabry-Perot cavity comprises a laser, a laser modulation module, the Fabry-Perot cavity and a cavity length locking module. Wherein the laser modulation module is arranged at the emitting end of the laser and is used for receiving laser emitted by the laser, outputting first laser and second laser, emitting the first laser into the Fabry-Perot cavity from the first end of the Fabry-Perot cavity and emitting the second laser into the Fabry-Perot cavity from the second end of the Fabry-Perot cavity. And the cavity length locking module is connected with the Fabry-Perot cavity and the laser modulation module, and is used for locking the cavity length of the Fabry-Perot cavity in response to the first reflection laser reflected from the first end of the Fabry-Perot cavity and a signal received from the laser modulation module.

Description

Technical Field

[0001] This application relates to the technical field of laser frequency stabilization, and particularly to a cavity length locking and laser frequency stabilization system and method for a Fabry - Perot cavity. Background Art

[0002] Currently, the technology for laser frequency stabilization based on a Fabry - Perot cavity (FP cavity) either relies on a cavity with an ultra - stable low - thermal - expansion rate such as a ULE cavity, or requires further locking the cavity length on a molecular / atomic absorption line to ensure the long - term stability of the cavity length. The former requires expensive low - thermal - expansion rate materials (such as ULE glass) to fabricate the FP cavity and needs to place the FP cavity in a vacuum to stabilize the gas refractive index. The latter requires an additional set of molecular / atomic vapor cells to lock the cavity length. As a result, the laser frequency stabilization system becomes more complex and is not easy to integrate. Summary of the Invention

[0003] The present disclosure provides a cavity length locking and laser frequency stabilization system and method for a Fabry - Perot cavity, so as to at least solve the technical problem that the laser frequency stabilization system in the prior art is more complex and not easy to integrate.

[0004] According to one aspect of the present application, a cavity length locking system for a Fabry - Perot cavity is provided, including: a laser, a laser modulation module, a Fabry - Perot cavity, and a cavity length locking module. Among them, the laser modulation module is disposed at the output end of the laser, and is configured to receive the laser emitted by the laser and output a first laser and a second laser, and inject the first laser into the Fabry - Perot cavity from the first end of the Fabry - Perot cavity and inject the second laser into the Fabry - Perot cavity from the second end of the Fabry - Perot cavity. Among them, the second laser emitted by the laser modulation module is locked in the Fabry - Perot cavity, and the frequency difference between the first frequency sideband of the first laser emitted by the laser modulation module and the second laser corresponds to an integer multiple of the free spectral range of the Fabry - Perot cavity; and the cavity length locking module is connected to the Fabry - Perot cavity and the laser modulation module, and is configured to lock the cavity length of the Fabry - Perot cavity in response to the first reflected laser reflected from the first end of the Fabry - Perot cavity and the signal received from the laser modulation module.

[0005] According to another aspect of the present application, a laser frequency stabilization system is provided, including the above cavity length locking system, and the laser frequency stabilization system further includes a second PID controller and a second photodetector. Wherein, the second photodetector is disposed corresponding to the second end of the Fabry-Perot cavity and is connected to the laser modulation module, and is configured to generate a corresponding second detection signal in response to the second reflected laser reflected from the second end of the Fabry-Perot cavity, and input the second detection signal into the laser modulation module; the laser modulation module is configured to generate a third carrier signal based on the second detection signal; the second PID controller is connected to the laser modulation module and the laser, and is configured to lock the frequency of the laser in response to the third carrier signal received from the laser modulation module.

[0006] According to another aspect of the present application, a method for locking the cavity length of a Fabry-Perot cavity is provided, including: using a laser modulation module to receive the laser emitted by a laser and output a first laser and a second laser, and injecting the first laser into the Fabry-Perot cavity from the first end of the Fabry-Perot cavity and injecting the second laser into the Fabry-Perot cavity from the second end of the Fabry-Perot cavity. Wherein, the second laser emitted by the laser modulation module is locked in the Fabry-Perot cavity, and the frequency difference between the first frequency sideband of the first laser emitted by the laser modulation module and the second laser corresponds to an integer multiple of the free spectral range of the Fabry-Perot cavity; and using a cavity length locking module to lock the cavity length of the Fabry-Perot cavity in response to the first reflected laser reflected from the first end of the Fabry-Perot cavity and the signal received from the laser modulation module.

[0007] According to another aspect of the present application, a laser frequency stabilization method is provided, including: using a laser modulation module to receive the laser emitted by a laser and output a first laser and a second laser, and injecting the first laser into the Fabry-Perot cavity from the first end of the Fabry-Perot cavity and injecting the second laser into the Fabry-Perot cavity from the second end of the Fabry-Perot cavity. Wherein, the second laser emitted by the laser modulation module is locked in the Fabry-Perot cavity, and the frequency difference between the first frequency sideband of the first laser emitted by the laser modulation module and the second laser corresponds to an integer multiple of the free spectral range of the Fabry-Perot cavity; using a cavity length locking module to lock the cavity length of the Fabry-Perot cavity in response to the first reflected laser reflected from the first end of the Fabry-Perot cavity and the signal received from the laser modulation module; using a second photodetector to generate a corresponding second detection signal in response to the second reflected laser reflected from the second end of the Fabry-Perot cavity, and input the second detection signal into the laser modulation module; using the laser modulation module to generate a third carrier signal based on the second detection signal; and using a second PID controller to lock the frequency of the laser in response to the third carrier signal received from the laser modulation module.

[0008] Therefore, the technical solution of the present application does not require expensive materials with ultra-low thermal expansion rates and vacuum chambers, nor does it require molecular / atomic vapor chambers, and can also ensure the stability of the cavity length of the Fabry-Perot cavity. Therefore, it is simpler, easier to integrate, and has a lower cost. The technical solution of the present disclosure locks the free spectral range of the Fabry-Perot cavity onto the carrier signal of the microwave, thereby locking the cavity length of the Fabry-Perot cavity.

[0009] From the following detailed description of specific embodiments of the present application in conjunction with the accompanying drawings, those skilled in the art will become more apparent about the above and other objects, advantages, and features of the present application. Brief Description of the Drawings

[0010] Some specific embodiments of the present application will be described in detail hereinafter with reference to the accompanying drawings in an exemplary but not restrictive manner. The same reference numerals in the drawings denote the same or similar components or parts. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings:

[0011] Figure 1A is a schematic perspective view of the cavity length locking and laser frequency stabilization system of the Fabry-Perot according to an embodiment of the present application

[0012] Figure 1B is an expanded schematic perspective view of the cavity length locking and laser frequency stabilization system of the Fabry-Perot according to an embodiment of the present application;

[0013] Figure 2 is a frequency domain schematic diagram after phase modulation of the first laser and frequency shift of the second laser according to an embodiment of the present application;

[0014] Figure 3 is a schematic flowchart of the cavity length locking method of the Fabry-Perot cavity according to the third aspect of the embodiment of the present application; and

[0015] Figure 4 is a schematic flowchart of the laser frequency stabilization method according to the fourth aspect of the embodiment of the present application. Detailed Description of the Embodiments

[0016] It should be noted that, without conflict, the embodiments in the present disclosure and the features in the embodiments may be combined with each other. The present disclosure will be described in detail below with reference to the drawings and in conjunction with the embodiments.

[0017] To enable those skilled in the art to better understand the present disclosure solution, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only a part of the embodiments of the present disclosure, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments in the present disclosure without creative efforts shall fall within the scope of protection of the present disclosure.

[0018] It should be noted that the terms "first", "second", etc. in the specification and claims of the present disclosure and the above-mentioned drawings are used to distinguish similar objects, and do not necessarily describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances for the embodiments of the present disclosure described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units does not necessarily limit to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0019] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0020] Figure 1A is a schematic perspective view of a Fabry-Perot cavity length locking and laser frequency stabilization system according to an embodiment of the present application. Figure 1B is a further expanded schematic perspective view of a Fabry-Perot cavity length locking and laser frequency stabilization system according to an embodiment of the present application.

[0021] Reference Figure 1AAs shown below, according to the first aspect of this embodiment, a cavity length locking system for a Fabry-Perot cavity is provided. The system includes: a laser 110, a laser modulation module 10, a Fabry-Perot cavity 130, and a cavity length locking module 160. The laser modulation module 10 is disposed at the output end of the laser 110, and is configured to receive the laser emitted by the laser 110 and output a first laser 101 and a second laser 102, and inject the first laser 101 into the Fabry-Perot cavity 130 from the first end of the Fabry-Perot cavity 130 and inject the second laser 102 into the Fabry-Perot cavity 130 from the second end of the Fabry-Perot cavity 130. Among them, the second laser 102 emitted by the laser modulation module 10 is locked in the Fabry-Perot cavity 130, and the frequency difference between the first frequency sideband SB1 of the first laser 101 emitted by the laser modulation module 10 and the second laser 102 corresponds to an integer multiple of the free spectral range of the Fabry-Perot cavity 130; and the cavity length locking module 160 is connected to the Fabry-Perot cavity 130 and the laser modulation module 10, and is configured to lock the cavity length of the Fabry-Perot cavity 130 in response to the first reflected laser 201 reflected from the first end of the Fabry-Perot cavity 130 and the signal received from the laser modulation module 10.

[0022] As described in the background art, currently, the technology for laser frequency stabilization based on a Fabry-Perot cavity (FP cavity) either relies on a cavity with an ultra-stable low thermal expansion rate (such as a ULE cavity) for the cavity length, or requires further locking the cavity length on a molecular / atomic absorption line to ensure the long-term stability of the cavity length. The former requires processing an FP cavity with expensive low thermal expansion rate materials (such as ULE glass), and requires placing the FP cavity in a vacuum to stabilize the gas refractive index. The latter requires an additional set of molecular / atomic vapor chambers to lock the cavity length.

[0023] In view of this, this embodiment proposes a cavity length locking system for a Fabry-Perot cavity. The cavity length locking system uses the laser modulation module 10 to receive the laser emitted by the laser 110 and output a first laser 101 and a second laser 102. Among them, the second laser 102 is locked in the Fabry-Perot cavity, that is, the frequency of the second laser 102 corresponds to an integer multiple of the free spectral range (fsr) of the Fabry-Perot cavity 130. The frequency difference between the first frequency sideband SB1 of the first laser 101 and the second laser 102 corresponds to an integer multiple of the free spectral range (fsr) of the Fabry-Perot cavity 130. Thus, the cavity length locking system of this embodiment can simultaneously resonate the frequency of the second laser 102 and the frequency of the first frequency sideband SB1 of the first laser 101 with the Fabry-Perot cavity 130. Thus, the free spectral range ω of the Fabry-Perot cavity 130 is ensured to be stable. Where ω fsr is defined by the following formula: fsr

[0024] ​

[0025] wherein, L is the cavity length of the Fabry - Perot cavity 130. Therefore, ω fsr The stability ensures the stability of the cavity length of the Fabry - Perot cavity 130. Thus, the technical solution of the present disclosure locks the free spectral range of the Fabry - Perot cavity on the carrier signal of the microwave, thereby locking the cavity length of the Fabry - Perot cavity.

[0026] Therefore, this embodiment does not require expensive materials with ultra - low thermal expansion rate and vacuum chambers, nor does it require molecular / atomic vapor chambers, and can also ensure the stability of the cavity length of the Fabry - Perot cavity. Therefore, it is simpler, easier to integrate, and has lower cost.

[0027] Optionally, as shown in Figure 1B the laser modulation module 10 includes: a beam splitting module 120, a frequency modulation module 140, and a phase modulation module 150. The beam splitting module 120 is disposed at the output end of the laser 110 and is used to split the laser emitted by the laser 110 into a first laser 101 propagating along a first optical path and a second laser 102 propagating along a second optical path. The first optical path guides the first laser 101 to enter the Fabry - Perot cavity 130 from the first end of the Fabry - Perot cavity 130, and the second optical path guides the second laser 102 to enter the Fabry - Perot cavity 130 from the second end of the Fabry - Perot cavity 130. The frequency modulation module 140 is disposed on the second optical path and is used to shift the frequency of the second laser 102 so that the frequency - shifted second laser 102 is locked to the Fabry - Perot cavity 130. The phase modulation module 150 is disposed on the first optical path and is used to perform phase modulation on the first laser 101 so that the first laser 101 generates a first frequency sideband SB1, and the frequency difference between the first frequency sideband SB1 and the frequency - shifted second laser 102 corresponds to an integer multiple of the free spectral range of the Fabry - Perot cavity 130. And, the cavity length locking module 160 is connected to the Fabry - Perot cavity 130 and the phase modulation module 150, and is used to lock the cavity length of the Fabry - Perot cavity 130 in response to the first reflected laser 201 reflected from the first end of the Fabry - Perot cavity 130 and the signal received from the phase modulation module 150.

[0028] Thus, the cavity length locking system of the Fabry - Perot cavity described in this embodiment first uses the beam splitting module 120 to divide the laser emitted by the laser 110 into the first laser 101 and the second laser 102. Then, the system uses the frequency modulation module 140 to shift the frequency of the second laser 102, as shown in Figure 2 to shift the second laser 102 by ω aomand locked in the Fabry - Perot cavity 130, that is, by feedback adjustment, the frequency of the second laser 102 after frequency shift is made to correspond to an integer multiple of the free spectral range (FSR) of the Fabry - Perot cavity 130. And the system uses the phase modulation module 150 to perform phase modulation on the first laser 101, and referring to Figure 2 as shown, after the first laser 101 passes through the phase modulation module 150, the first frequency sideband SB1 is generated. And referring to Figure 2 as shown, the frequency difference ω1 between the first frequency sideband SB1 and the main frequency of the first laser 101 is

[0029] ω1 = n * ωf sr -ω aom

[0030] where n is a positive integer, and ω fsr is the frequency corresponding to the free spectral range of the Fabry - Perot cavity 130. Thus, the frequency difference between the first frequency sideband SB1 of the first laser 101 and the second laser 102 is n * ω fsr . That is, the frequency difference between the first frequency sideband SB1 of the first laser 101 and the second laser 102 corresponds to an integer multiple of the free spectral range of the Fabry - Perot cavity 130.

[0031] Since the second laser 102 after frequency shift is locked on a certain resonance peak of the Fabry - Perot cavity 130, the first frequency sideband SB1 of the first laser 101 also resonates with the Fabry - Perot cavity 130. And the system locks the Fabry - Perot cavity 130 on the first frequency sideband SB1 of the first laser 101 through the cavity length locking module 160.

[0032] Thus, the cavity length locking system of this embodiment can make the frequency of the second laser 102 and the frequency of the first frequency sideband SB1 of the first laser 101 resonate with the Fabry - Perot cavity 130 simultaneously. Thus, it ensures that the free spectral range ω fsr of the Fabry - Perot cavity 130 is stable. Where ω fsr is defined by the following formula:

[0033]

[0034] where L is the cavity length of the Fabry - Perot cavity 130. Therefore, the stability of ω fsr ensures the stability of the cavity length of the Fabry - Perot cavity 130. Thus, the technical solution of the present disclosure locks the free spectral range of the Fabry - Perot cavity on the carrier signal of the microwave, thereby locking the cavity length of the Fabry - Perot cavity.

[0035] Therefore, this embodiment does not require expensive materials with ultra-low thermal expansion rates and vacuum enclosures, nor does it require molecular / atomic vapor chambers, and can also ensure the stability of the cavity length of the Fabry-Perot cavity. Therefore, it is simpler, easier to integrate, and has a lower cost.

[0036] Optionally, the phase modulation module 150 includes: a radio frequency signal generator 151, a microwave generator 152, and an electro-optic modulator 153. The radio frequency signal generator 151 is connected to the microwave generator 152 and sends a radio frequency signal to the phase modulation port of the microwave generator 152. The microwave generator 152 is connected to the radio frequency signal generator 151 and the electro-optic modulator 153, and is configured to receive the radio frequency signal and send a first carrier signal phase-modulated by the radio frequency signal to the electro-optic modulator 153. The electro-optic modulator 153 is disposed on the first optical path and is configured to perform phase modulation on the first laser 101 in response to the first carrier signal, so that the first laser generates a first frequency sideband SB1 and a second frequency sideband SB2. The frequency difference ω1 between the first frequency sideband SB1 and the main frequency of the first laser corresponds to the frequency of the first carrier signal sent by the microwave generator 152, and the frequency difference ω2 between the first frequency sideband SB1 and the second frequency sideband SB2 corresponds to the frequency of the radio frequency signal.

[0037] Therefore, in this embodiment, the radio frequency signal generator 151 sends a radio frequency signal to the microwave generator 152, and the frequency of the radio frequency signal is ω2. Thus, the microwave generator 152 emits a carrier signal phase-modulated by the radio frequency signal to the electro-optic modulator 153, and its frequency is ω1. Thus, the electro-optic modulator 153 performs phase modulation on the first laser 101, thereby generating Figure 2 the first frequency sideband SB1 and the second frequency sideband SB2 shown, where the frequency difference between the first frequency sideband SB1 and the main frequency of the first laser is also ω1, and the frequency difference between the first frequency sideband SB1 and the second frequency sideband SB2 is ω2.

[0038] Further, the cavity length locking module 160 can be a PDH module. The second frequency sideband SB2 is the frequency sideband required by the PDH frequency stabilization technology. The specific value of the frequency difference ω2 can be set according to the experience of the PDH frequency stabilization technology, which will not be elaborated here.

[0039] Since the radio frequency technology can more precisely control the frequency of the radio frequency signal, the technical solution of this embodiment can more precisely control the electro-optic modulator 153 to generate the first frequency sideband SB1 and the second frequency sideband SB2, thereby locking the cavity length of the Fabry-Perot cavity by means of the first sideband SB1 and the second sideband SB2.

[0040] Optionally, the frequency modulation module 140 includes: a lock-in amplifier 142 and an acousto-optic modulator 143. The lock-in amplifier 142 is connected to the acousto-optic modulator 143 and is configured to output a frequency-modulated second carrier signal to the acousto-optic modulator 143, driving the acousto-optic modulator 143 to perform frequency shift on the second laser 102. The acousto-optic modulator 143 is disposed on the second optical path and is configured to perform frequency shift on the second laser 102 in response to the second carrier signal received from the lock-in amplifier 142.

[0041] Therefore, in this embodiment, the lock-in amplifier 142 outputs a frequency-modulated carrier signal to the acousto-optic modulator 143, so that the acousto-optic modulator 143 can be accurately controlled, and accurate frequency shift can be performed on the second laser 102.

[0042] Optionally, the cavity length locking module 160 includes: a phase shifter 161, a mixer 162, a first photodetector 163, a first PID controller 164, and a length regulator 165 disposed on the Fabry-Perot cavity 130. The phase shifter 161 is connected to the radio frequency signal generator 151 and the mixer 162, and is configured to perform phase shift on the radio frequency signal emitted by the radio frequency signal generator 151 and send the phase-shifted radio frequency signal to the mixer 162. The first photodetector 163 is disposed corresponding to the first end of the Fabry-Perot cavity 130 and is connected to the mixer 162, and is configured to generate a corresponding first detection signal in response to the first reflected laser 201 reflected from the first end of the Fabry-Perot cavity 130 and send the first detection signal to the mixer 162. The mixer 162 is respectively connected to the phase shifter 161, the first photodetector 163, and the first PID controller 164, and is configured to perform mixing operation on the radio frequency signal received from the phase shifter 161 and the first detection signal, and send the mixed signal after mixing to the first PID controller 164. The first PID controller 164 is connected to the mixer 162 and the length regulator 165, and is configured to control the length regulator 165 to lock the cavity length of the Fabry-Perot cavity 130 in response to the mixed signal.

[0043] Therefore, in this embodiment, the above-mentioned cavity length locking module can more stably lock the Fabry-Perot cavity 130 at the first frequency sideband SB1 of the first laser 101.

[0044] Optionally, the system further includes a first polarization beam splitter prism 171 and a first quarter-wave plate 181 sequentially disposed between the electro-optic modulator 153 and the Fabry-Perot cavity 130 on the first optical path. The first laser 101 is incident on the first end of the Fabry-Perot cavity 130 via the first polarization beam splitter prism 171 and the first quarter-wave plate 181. The first reflected laser 201 is incident on the first polarization beam splitter prism 171 via the first quarter-wave plate 181, and is reflected by the first polarization beam splitter prism 171 and guided to the first photodetector 163.

[0045] Optionally, the system further includes a second polarization beam splitter prism 172 and a second quarter-wave plate 182 which are sequentially arranged on the second optical path between the acousto-optic modulator 143 and the Fabry-Perot cavity 130. The second laser 102 is reflected by the second polarization beam splitter prism 172 to the second quarter-wave plate 182 and is incident on the second end of the Fabry-Perot cavity 130 via the second quarter-wave plate 182.

[0046] In addition, referring to Figure 1B As shown, according to the second aspect of the present embodiment, a laser frequency stabilization system is provided. The laser frequency stabilization system includes the cavity length locking system described in any one of the above. And the laser frequency stabilization system further includes a second PID controller 190 and a second photodetector 141. The second photodetector 141 is arranged corresponding to the second end of the Fabry-Perot cavity 130 and is connected to the laser modulation module 10, and is configured to generate a corresponding second detection signal in response to the second reflected laser 202 reflected from the second end of the Fabry-Perot cavity 130, and input the second detection signal to the laser modulation module 10; the laser modulation module 10 is configured to generate a third carrier signal based on the second detection signal; and the second PID controller 190 is connected to the laser modulation module 10 and the laser 110, and is configured to lock the frequency of the laser 110 in response to the third carrier signal received from the laser modulation module 100. Wherein, the second reflected laser 202 is incident on the second photodetector 141 via the second quarter-wave plate 182 and the second polarization beam splitter prism 172.

[0047] Thus, since Figure 1B the system shown can ensure the stability of the cavity length of the Fabry-Perot cavity 130, the frequency stability of the laser 110 can be further ensured based on the Fabry-Perot cavity 130, and finally the frequency stabilization operation of the laser 110 is realized.

[0048] Further referring to Figure 1B As shown, the second photodetector 141 is connected to a lock-in amplifier 142, so as to generate the lock-in amplifier 142 with the second detection signal. Thus, since the lock-in amplifier 142 inputs a frequency-modulated second carrier signal to the acousto-optic modulator 143, the signal received by the second photodetector 141 will carry a modulation component corresponding to the frequency of the second carrier signal. The second carrier signal and the second detection signal are mixed inside the lock-in amplifier 142 to output a DC error signal to the second PID controller 190, thereby locking the laser emitted by the laser 110 on the Fabry-Perot cavity 130.

[0049] According to the third aspect of the present embodiment, a method for locking the cavity length of a Fabry-Perot cavity is provided, wherein Figure 3 the flowchart of the method is shown. Referring to Figure 3 as shown, the method includes:

[0050] S302: The laser modulation module 10 is used to receive the laser emitted by the laser 110 and output a first laser 101 and a second laser 102, and to inject the first laser 101 into the Fabry-Perot cavity 130 from the first end of the Fabry-Perot cavity 130 and inject the second laser 102 into the Fabry-Perot cavity 130 from the second end of the Fabry-Perot cavity 130. Among them, the second laser 102 emitted by the laser modulation module 10 is locked in the Fabry-Perot cavity 130, and the frequency difference between the first frequency sideband SB1 of the first laser 101 emitted by the laser modulation module 10 and the second laser 102 corresponds to an integer multiple of the free spectral range of the Fabry-Perot cavity 130; and

[0051] S304: The cavity length locking module 160 is used to lock the cavity length of the Fabry-Perot cavity 130 in response to the first reflected laser 201 reflected from the first end of the Fabry-Perot cavity 130 and the signal received from the laser modulation module 10.

[0052] Optionally, the operation of using the laser modulation module 10 to receive the laser emitted by the laser 110 and output a first laser 101 and a second laser 102 includes: using the beam splitting module 120 of the laser modulation module 10 to split the laser emitted by the laser 110 into a first laser 101 propagating along a first optical path and a second laser 102 propagating along a second optical path. The first optical path guides the first laser 101 to be injected into the Fabry-Perot cavity 130 from the first end of the Fabry-Perot cavity 130, and the second optical path guides the second laser 102 to be injected into the Fabry-Perot cavity 130 from the second end of the Fabry-Perot cavity 130; using the frequency modulation module 140 of the laser modulation module 10 to perform frequency shifting on the second laser 102 so that the frequency-shifted second laser 102 is locked in the Fabry-Perot cavity 130; and using the phase modulation module 150 of the laser modulation module 10 to perform phase modulation on the first laser 101 so that the first laser 101 generates a first frequency sideband SB1, and the frequency difference between the first frequency sideband SB1 and the frequency-shifted second laser 102 corresponds to an integer multiple of the free spectral range of the Fabry-Perot cavity 130. And among them, the operation of using the cavity length locking module 160 to lock the cavity length of the Fabry-Perot cavity 130 in response to the first reflected laser 201 reflected from the first end of the Fabry-Perot cavity 130 and the signal received from the laser modulation module 10 includes: using the cavity length locking module 160 to lock the cavity length of the Fabry-Perot cavity 130 in response to the first reflected laser 201 and the signal received from the phase modulation module 150.

[0053] Optionally, the operation of phase modulating the first laser 101 by using the phase modulation module 150 includes: sending a radio frequency signal from the radio frequency signal generator 151 of the phase modulation module 150 to the phase modulation port of the microwave generator 152 of the phase modulation module 150; receiving the radio frequency signal by the microwave generator 152 and sending a first carrier signal phase modulated by the radio frequency signal to the electro-optic modulator 153 of the phase modulation module 150; and using the electro-optic modulator 153 to phase modulate the first laser 101 in response to the first carrier signal, so that the first laser generates a first frequency sideband SB1 and a second frequency sideband SB2, where the frequency difference ω1 between the first frequency sideband SB1 and the main frequency of the first laser corresponds to the frequency of the first carrier signal, and the frequency difference ω2 between the first frequency sideband SB1 and the second frequency sideband SB2 corresponds to the frequency of the radio frequency signal. And wherein, the operation of frequency shifting the second laser 102 by using the frequency modulation module 140 includes: outputting a frequency-modulated second carrier signal from the lock-in amplifier 142 of the frequency modulation module 140 to the acousto-optic modulator 143 of the frequency modulation module 140 to drive the acousto-optic modulator 143 to frequency shift the second laser 102; and using the acousto-optic modulator 143 to frequency shift the second laser 102 in response to the second carrier signal received from the lock-in amplifier 142. And wherein, the operation of adjusting the cavity length of the Fabry-Perot cavity 130 by using the cavity length locking module 160 in response to the first reflected laser 201 reflected from the first end of the Fabry-Perot cavity 130 and the signal received from the phase modulation module 150 includes: phase shifting the radio frequency signal emitted by the radio frequency signal generator 151 by using the phase shifter 161 of the cavity length locking module 160 and sending the phase-shifted radio frequency signal to the mixer 162 of the cavity length locking module 160; generating a corresponding first detection signal by using the first photodetector 163 of the cavity length locking module 160 in response to the first reflected laser 201 reflected from the first end of the Fabry-Perot cavity 130 and sending the first detection signal to the mixer 162; performing a mixing operation on the radio frequency signal received from the phase shifter 161 and the first detection signal by using the mixer 162 and sending the mixed signal after mixing to the first PID controller 164 of the cavity length locking module 160; and using the first PID controller 164 to control the length regulator 165 of the cavity length locking module 160 to adjust the cavity length of the Fabry-Perot cavity 130 in response to the mixed signal.

[0054] According to the fourth aspect of this embodiment, a laser frequency stabilization method is provided. Figure 4 The flowchart of this method is shown. Refer to Figure 4 As shown, this method includes:

[0055] S402: The laser modulation module 10 receives the laser emitted by the laser 110 and outputs the first laser 101 and the second laser 102, and injects the first laser 101 into the Fabry-Perot cavity 130 from the first end of the Fabry-Perot cavity 130 and injects the second laser 102 into the Fabry-Perot cavity 130 from the second end of the Fabry-Perot cavity 130. Among them, the second laser 102 emitted by the laser modulation module 10 is locked in the Fabry-Perot cavity 130, and the frequency difference between the first frequency sideband SB1 of the first laser 101 emitted by the laser modulation module 10 and the second laser 102 corresponds to an integer multiple of the free spectral range of the Fabry-Perot cavity 130;

[0056] S404: The cavity length locking module 160 locks the cavity length of the Fabry-Perot cavity 130 in response to the first reflected laser 201 reflected from the first end of the Fabry-Perot cavity 130 and the signal received from the laser modulation module 10;

[0057] S406: The second photodetector 141 generates a corresponding second detection signal in response to the second reflected laser 202 reflected from the second end of the Fabry-Perot cavity 130, and inputs the second detection signal into the laser modulation module 10;

[0058] S408: The laser modulation module 10 generates a third carrier signal based on the second detection signal; and

[0059] S410: The second PID controller 190 locks the frequency of the laser 110 in response to the third carrier signal received from the laser modulation module 10.

[0060] Optionally, the operation of using the laser modulation module 10 to receive the laser emitted by the laser 110 and output the first laser 101 and the second laser 102 includes: using the beam splitting module 120 of the laser modulation module 10 to split the laser emitted by the laser 110 into the first laser 101 propagating along the first optical path and the second laser 102 propagating along the second optical path, where the first optical path guides the first laser 101 to enter the Fabry-Perot cavity 130 from the first end of the Fabry-Perot cavity 130, and the second optical path guides the second laser 102 to enter the Fabry-Perot cavity 130 from the second end of the Fabry-Perot cavity 130; using the frequency modulation module 140 of the laser modulation module 10 to shift the frequency of the second laser 102 so that the frequency-shifted second laser 102 is locked to the Fabry-Perot cavity 130; and using the phase modulation module 150 of the laser modulation module 10 to perform phase modulation on the first laser 101 so that the first laser 101 generates a first frequency sideband SB1 and a second frequency sideband SB2, and the frequency difference between the first frequency sideband SB1 and the frequency-shifted second laser 102 corresponds to an integer multiple of the free spectral range of the Fabry-Perot cavity 130. And the operation of using the cavity length locking module 160 to lock the cavity length of the Fabry-Perot cavity 130 in response to the first reflected laser 201 reflected from the first end of the Fabry-Perot cavity 130 and the signal received from the laser modulation module 10 includes: using the cavity length locking module 160 to adjust the cavity length of the Fabry-Perot cavity 130 in response to the first reflected laser 201 reflected from the first end of the Fabry-Perot cavity 130 and the signal received from the phase modulation module 150.

[0061] Optionally, the operation of using the laser modulation module 10 to generate a third carrier signal based on the second detection signal includes: using the lock-in amplifier 142 of the laser modulation module 10 to receive the second detection signal and generate the third carrier signal.

[0062] Therefore, this embodiment does not require expensive materials with ultra-low thermal expansion rates and vacuum enclosures, nor does it require a molecular / atomic vapor chamber, and can also ensure the stability of the cavity length of the Fabry-Perot cavity. Therefore, it is simpler, easier to integrate, and has a lower cost. And the technical solution of the present disclosure locks the free spectral range of the Fabry-Perot cavity to the carrier signal of the microwave, thereby locking the cavity length of the Fabry-Perot cavity.

[0063] Unless otherwise specifically stated, the relative arrangements of components and steps, numerical expressions, and numerical values set forth in these embodiments do not limit the scope of the present disclosure. At the same time, it should be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn in actual proportional relationships. Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such technologies, methods, and devices should be regarded as part of the authorization specification. In all the examples shown and discussed here, any specific values should be construed as merely exemplary and not as a limitation. Thus, other examples of the exemplary embodiments may have different values. It should be noted that like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, further discussion thereof is not required in subsequent drawings.

[0064] For ease of description, spatial relative terms such as "above", "over", "on the upper surface", "above", etc. may be used herein to describe the spatial positional relationship of one device or feature to other devices or features as shown in the figures. It should be understood that the spatial relative terms are intended to encompass different orientations in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figure is inverted, the device described as "above" or "over" other devices or structures will then be positioned "below" or "beneath" other devices or structures. Thus, the exemplary term "above" can include both the orientations of "above" and "below". The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and corresponding interpretations should be made for the spatial relative descriptions used herein.

[0065] In the description of the present disclosure, it should be understood that the orientation or positional relationships indicated by orientation terms such as "front, rear, upper, lower, left, right", "lateral, vertical, perpendicular, horizontal", and "top, bottom" are generally based on the orientation or positional relationships shown in the drawings, and are only for ease of describing the present disclosure and simplifying the description. Without contrary description, these orientation terms do not indicate and imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and thus should not be construed as limiting the protection scope of the present disclosure; the orientation terms "inside, outside" refer to the inside and outside relative to the contour of each component itself.

[0066] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the technical field of the present application within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A cavity length locking system for a Fabry - Perot cavity, characterized in that, Including: a laser (110), a laser modulation module (10), a Fabry - Perot cavity (130), and a cavity length locking module (160), where the laser modulation module (10) is disposed at an output end of the laser (110), and is configured to receive the laser emitted by the laser (110) and output a first laser (101) and a second laser (102), and inject the first laser (101) into the Fabry - Perot cavity (130) from a first end of the Fabry - Perot cavity (130) and inject the second laser (102) into the Fabry - Perot cavity (130) from a second end of the Fabry - Perot cavity (130). Wherein, the second laser (102) emitted by the laser modulation module (10) is locked in the Fabry - Perot cavity (130), and a frequency difference between a first frequency sideband (SB1) of the first laser (101) emitted by the laser modulation module (10) and the second laser (102) corresponds to an integer multiple of a free spectral range of the Fabry - Perot cavity (130); and the cavity length locking module (160) is connected to the Fabry - Perot cavity (130) and the laser modulation module (10), and is configured to lock a cavity length of the Fabry - Perot cavity (130) in response to a first reflected laser (201) reflected from the first end of the Fabry - Perot cavity (130) and a signal received from the laser modulation module (10).

2. The system according to claim 1, wherein The laser modulation module (10) includes: a beam splitting module (120), a frequency modulation module (140), a phase modulation module (150), and a cavity length locking module (160), where the beam splitting module (120) is disposed at an output end of the laser (110), and is configured to split the laser emitted by the laser (110) into a first laser (101) propagating along a first optical path and a second laser (102) propagating along a second optical path. The first optical path guides the first laser (101) to be injected into the Fabry - Perot cavity (130) from the first end of the Fabry - Perot cavity (130), and the second optical path guides the second laser (102) to be injected into the Fabry - Perot cavity (130) from the second end of the Fabry - Perot cavity (130); the frequency modulation module (140) is disposed on the second optical path, and is configured to shift the frequency of the second laser (102) so that the frequency - shifted second laser (102) is locked in the Fabry - Perot cavity (130); the phase modulation module (150) is disposed on the first optical path, and is configured to perform phase modulation on the first laser (101) so that the first laser (101) generates a first frequency sideband (SB1), and a frequency difference between the first frequency sideband (SB1) and the frequency - shifted second laser (102) corresponds to an integer multiple of a free spectral range of the Fabry - Perot cavity (130); and The cavity length locking module (160) is connected to the Fabry - Perot cavity (130) and the phase modulation module (150), and is configured to lock the cavity length of the Fabry - Perot cavity (130) in response to a first reflected laser (201) reflected from the first end of the Fabry - Perot cavity (130) and a signal received from the phase modulation module (150).

3. The system according to claim 2, wherein The phase modulation module (150) includes: a radio frequency signal generator (151), a microwave generator (152), and an electro - optic modulator (153), where the radio frequency signal generator (151) is connected to the microwave generator (152) and sends a radio frequency signal to the phase modulation port of the microwave generator (152); the microwave generator (152) is connected to the radio frequency signal generator (151) and the electro - optic modulator (153), and is configured to receive the radio frequency signal and send a first carrier signal phase - modulated by the radio frequency signal to the electro - optic modulator (153); and the electro - optic modulator (153) is disposed on the first optical path and is configured to perform phase modulation on the first laser (101) in response to the first carrier signal, so that the first laser generates a first frequency sideband (SB1) and a second frequency sideband (SB2), where the frequency difference (ω1) between the first frequency sideband (SB1) and the main frequency of the first laser corresponds to the frequency of the first carrier signal, and the frequency difference (ω2) between the first frequency sideband (SB1) and the second frequency sideband (SB2) corresponds to the frequency of the radio frequency signal.

4. The system according to claim 3, wherein The frequency modulation module (140) includes: a lock - in amplifier (142) and an acousto - optic modulator (143), where the lock - in amplifier (142) is connected to the acousto - optic modulator (143) and is configured to output a frequency - modulated second carrier signal to the acousto - optic modulator (143) to drive the acousto - optic modulator (143) to perform frequency shift on the second laser (102); and the acousto - optic modulator (143) is disposed on the second optical path and is configured to perform frequency shift on the second laser (102) in response to the second carrier signal received from the lock - in amplifier (142).

5. The system according to claim 4, characterized in that, The cavity length locking module (160) includes: a phase shifter (161), a mixer (162), a first photodetector (163), a first PID controller (164), and a length regulator (165) disposed on the Fabry - Perot cavity (130), where the phase shifter (161) is connected to the radio frequency signal generator (151) and the mixer (162), and is configured to perform phase shift on the radio frequency signal emitted by the radio frequency signal generator (151) and send the phase - shifted radio frequency signal to the mixer (162); The first photodetector (163) is disposed corresponding to the first end of the Fabry - Perot cavity (130), and is connected to the mixer (162), and is configured to generate a corresponding first detection signal in response to a first reflected laser (201) reflected from the first end of the Fabry - Perot cavity (130), and send the first detection signal to the mixer (162); The mixer (162) is respectively connected to the phase shifter (161), the first photodetector (163), and the first PID controller (164), and is configured to perform a mixing operation on the radio frequency signal received from the phase shifter (161) and the first detection signal, and send the mixed signal after mixing to the first PID controller (164); and The first PID controller (164) is connected to the mixer (162) and the length regulator (165), and is configured to control the length regulator (165) to adjust the cavity length of the Fabry - Perot cavity (130) in response to the mixed signal.

6. The system according to claim 5, wherein It further includes a first polarization beam splitter prism (171) and a first quarter - wave plate (181) sequentially disposed on the first optical path between the electro - optic modulator (153) and the Fabry - Perot cavity (130), where The first laser (101) is incident on the first end of the Fabry - Perot cavity (130) via the first polarization beam splitter prism (171) and the first quarter - wave plate (181); and The first reflected laser (201) is incident on the first polarization beam splitter prism (171) via the first quarter - wave plate (181), and is reflected by the first polarization beam splitter prism (171) and guided to the first photodetector (163).

7. The system according to claim 5, wherein It further includes a second polarization beam splitter prism (172) and a second quarter - wave plate (182) sequentially disposed on the second optical path between the acousto - optic modulator (143) and the Fabry - Perot cavity (130), where The second laser (102) is reflected by the second polarization beam splitter prism (172) to the second quarter - wave plate (182), and is incident on the second end of the Fabry - Perot cavity (130) via the second quarter - wave plate (182).

8. A laser frequency stabilization system, characterized in that, It includes the cavity length locking system according to any one of claims 1 - 7, and the laser frequency stabilization system further includes a second PID controller (190) and a second photodetector (141), where The second photodetector (141) is disposed corresponding to the second end of the Fabry - Perot cavity (130), and is connected to the laser modulation module (10), and is configured to generate a corresponding second detection signal in response to a second reflected laser (202) reflected from the second end of the Fabry - Perot cavity (130), and input the second detection signal into the laser modulation module (10); The laser modulation module (10) is configured to generate a third carrier signal based on the second detection signal; The second PID controller (190) is connected to the laser modulation module (10) and the laser (110), and is configured to lock the frequency of the laser (110) in response to a third carrier signal received from the laser modulation module (10).

9. A method for locking the cavity length of a Fabry-Perot cavity, characterized in that Comprising: The laser modulation module (10) receives the laser emitted by the laser (110) and outputs a first laser (101) and a second laser (102), and the first laser (101) is incident into the Fabry-Perot cavity (130) from a first end of the Fabry-Perot cavity (130), and the second laser (102) is incident into the Fabry-Perot cavity (130) from a second end of the Fabry-Perot cavity (130). Wherein, the second laser (102) emitted by the laser modulation module (10) is locked in the Fabry-Perot cavity (130), and the frequency difference between the first frequency sideband (SB1) of the first laser (101) emitted by the laser modulation module (10) and the second laser (102) corresponds to an integer multiple of the free spectral range of the Fabry-Perot cavity (130); And The cavity length locking module (160) locks the cavity length of the Fabry-Perot cavity (130) in response to a first reflected laser (201) reflected from a first end of the Fabry-Perot cavity (130) and a signal received from the laser modulation module (10).

10. The method according to claim 9, characterized in that, The operation of using the laser modulation module (10) to receive the laser emitted by the laser (110) and output the first laser (101) and the second laser (102) includes: The beam splitting module (120) of the laser modulation module (10) splits the laser emitted by the laser (110) into a first laser (101) propagating along a first optical path and a second laser (102) propagating along a second optical path. The first optical path guides the first laser (101) to be incident into the Fabry-Perot cavity (130) from a first end of the Fabry-Perot cavity (130), and the second optical path guides the second laser (102) to be incident into the Fabry-Perot cavity (130) from a second end of the Fabry-Perot cavity (130); The frequency modulation module (140) of the laser modulation module (10) performs frequency shifting on the second laser (102) so that the frequency-shifted second laser (102) is locked in the Fabry-Perot cavity (130); and The phase modulation module (150) of the laser modulation module (10) performs phase modulation on the first laser (101) so that the first laser (101) generates a first frequency sideband (SB1), and the frequency difference between the first frequency sideband (SB1) and the frequency-shifted second laser (102) corresponds to an integer multiple of the free spectral range of the Fabry-Perot cavity (130), and wherein, The operation of locking the cavity length of the Fabry - Perot cavity (130) by the cavity length locking module (160) in response to the first reflected laser (201) reflected from the first end of the Fabry - Perot cavity (130) and the signal received from the laser modulation module (10) includes: locking the cavity length of the Fabry - Perot cavity (130) by the cavity length locking module (160) in response to the first reflected laser (201) and the signal received from the phase modulation module (150).

11. The method according to claim 10, wherein The operation of phase - modulating the first laser (101) by the phase modulation module (150) includes: Using the radio - frequency signal generator (151) of the phase modulation module (150) to send a radio - frequency signal to the phase modulation port of the microwave generator (152) of the phase modulation module (150); Using the microwave generator (152) to receive the radio - frequency signal and send a first carrier signal phase - modulated by the radio - frequency signal to the electro - optic modulator (153) of the phase modulation module (150); and Using the electro - optic modulator (153) to phase - modulate the first laser (101) in response to the first carrier signal, so that the first laser generates the first frequency sideband (SB1) and the second frequency sideband (SB2), where the frequency difference (ω1) between the first frequency sideband (SB1) and the main frequency of the first laser corresponds to the frequency of the first carrier signal, the frequency difference (ω2) between the first frequency sideband (SB1) and the second frequency sideband (SB2) corresponds to the frequency of the radio - frequency signal, and where The operation of frequency - shifting the second laser (102) by the frequency modulation module (140) includes: Using the lock - in amplifier (142) of the frequency modulation module (140) to output a frequency - modulated second carrier signal to the acousto - optic modulator (143) of the frequency modulation module (140) to drive the acousto - optic modulator (143) to perform the frequency - shifting on the second laser (102); and Using the acousto - optic modulator (143) to perform frequency - shifting on the second laser (102) in response to the second carrier signal received from the lock - in amplifier (142), and where The operation of adjusting the cavity length of the Fabry - Perot cavity (130) by the cavity length locking module (160) in response to the first reflected laser (201) reflected from the first end of the Fabry - Perot cavity (130) and the signal received from the phase modulation module (150) includes: Using the phase shifter (161) of the cavity length locking module (160) to phase - shift the radio - frequency signal emitted by the radio - frequency signal generator (151) and send the phase - shifted radio - frequency signal to the mixer (162) of the cavity length locking module (160); The first photodetector (163) of the cavity length locking module (160) generates a corresponding first detection signal in response to a first reflected laser (201) reflected from the first end of the Fabry-Perot cavity (130), and sends the first detection signal to the mixer (162); The mixer (162) performs a mixing operation on the radio frequency signal received from the phase shifter (161) and the first detection signal, and sends the mixed signal to the first PID controller (164) of the cavity length locking module (160); and The first PID controller (164) controls the length adjuster (165) of the cavity length locking module (160) to adjust the cavity length of the Fabry-Perot cavity (130) in response to the mixed signal.

12. A laser frequency stabilization method, characterized in that, Comprising: The laser modulation module (10) receives the laser emitted by the laser (110) and outputs a first laser (101) and a second laser (102), and injects the first laser (101) into the Fabry-Perot cavity (130) from the first end of the Fabry-Perot cavity (130) and injects the second laser (102) into the Fabry-Perot cavity (130) from the second end of the Fabry-Perot cavity (130), wherein the second laser (102) emitted by the laser modulation module (10) is locked in the Fabry-Perot cavity (130), and the frequency difference between the first frequency sideband (SB1) of the first laser (101) emitted by the laser modulation module (10) and the second laser (102) corresponds to an integer multiple of the free spectral range of the Fabry-Perot cavity (130); The cavity length locking module (160) locks the cavity length of the Fabry-Perot cavity (130) in response to the first reflected laser (201) reflected from the first end of the Fabry-Perot cavity (130) and the signal received from the laser modulation module (10); The second photodetector (141) generates a corresponding second detection signal in response to a second reflected laser (202) reflected from the second end of the Fabry-Perot cavity (130), and inputs the second detection signal into the laser modulation module (10); The laser modulation module (10) generates a third carrier signal based on the second detection signal; and The second PID controller (190) locks the frequency of the laser (110) in response to the third carrier signal received from the laser modulation module (10).

13. The method according to claim 12, characterized in that, The operation of the laser modulation module (10) receiving the laser emitted by the laser (110) and outputting the first laser (101) and the second laser (102) includes: The beam splitting module (120) of the laser modulation module (10) splits the laser beam emitted by the laser (110) into a first laser beam (101) propagating along a first optical path and a second laser beam (102) propagating along a second optical path, wherein the first optical path guides the first laser beam (101) to enter the Fabry-Perot cavity (130) from a first end of the Fabry-Perot cavity (130), and the second optical path guides the second laser beam (102) to enter the Fabry-Perot cavity (130) from a second end of the Fabry-Perot cavity (130); The frequency modulation module (140) of the laser modulation module (10) is used to shift the frequency of the second laser beam (102) so that the frequency-shifted second laser beam (102) is locked to the Fabry-Perot cavity (130); and The phase modulation module (150) of the laser modulation module (10) is used to perform phase modulation on the first laser beam (101) so that the first laser beam (101) generates a first frequency sideband (SB1) and a second frequency sideband (SB2), and the frequency difference between the first frequency sideband (SB1) and the frequency-shifted second laser beam (102) corresponds to an integer multiple of the free spectral range of the Fabry-Perot cavity (130), and The operation of locking the cavity length of the Fabry-Perot cavity (130) by the cavity length locking module (160) in response to the first reflected laser beam (201) reflected from the first end of the Fabry-Perot cavity (130) and the signal received from the laser modulation module (10) includes: adjusting the cavity length of the Fabry-Perot cavity (130) by the cavity length locking module (160) in response to the first reflected laser beam (201) reflected from the first end of the Fabry-Perot cavity (130) and the signal received from the phase modulation module (150).

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