Optical lock-in system and method

Abstract

The application provides an optical locking cavity system and method, which comprises a laser assembly, a mode control assembly, an optical resonant cavity assembly, a detection assembly and a servo controller; the laser assembly is used for generating incident laser and adjusting parameters of the incident laser; the mode control assembly is used for splitting the incident laser into a first laser and a second laser; the optical resonant cavity assembly is used for generating a transmission peak signal through the first laser, transmitting the second laser and generating a first optical signal and a second optical signal through a nonlinear process; the detection assembly is used for converting the first optical signal into an intensity signal, performing a difference frequency operation on the intensity signal and a microwave signal to generate a difference frequency signal, amplifying the difference frequency signal to obtain an error signal; the servo controller is used for receiving the error signal generated by the detection assembly; based on the error signal, a feedback signal is generated and transmitted to a feedback actuator of the laser assembly, so as to solve the problem of difficulty in locking between a high-power laser and a high-quality factor optical resonant cavity.

Description

Technical Field

[0001] This application relates to the field of optical and optoelectronic modulation technology, and in particular to an optical cavity locking system and method. Background Technology

[0002] A series of high-power applications based on optical resonators represent a key research direction in the field. The high reflectivity of optical resonators allows for the observation of various nonlinear optical effects when high-power lasers propagate within the cavity, including but not limited to: pulsed laser generation and compression, optical parametric oscillations, and optical parametric amplification. In high-power applications, cavity-locking techniques are needed to improve laser frequency stability, which is of great significance for further exploration of nonlinear optical effects, the future development of novel optical devices, and the advancement of cutting-edge technologies.

[0003] In an optical resonant cavity, high-power input signals can cause thermal and nonlinear optical effects, including thermal drift of the optical resonant cavity length, thermo-optical effects, self-modulation effects, etc., which lead to unstable mode spacing and laser waveform distortion.

[0004] If traditional cavity-locking techniques are used to directly lock an optical resonator in high-power scenarios, it will cause distortion of the transmission peak signal and error signal, making it difficult for the feedback system to accurately identify and track the frequency and phase information in the optical cavity. This can lead to locking failure or large frequency fluctuations. These effects from intracavity nonlinearity need to be overcome by adjusting the signal processing algorithm or introducing additional compensation measures. Real-time dynamic adjustment of the feedback signal is required to counteract the effects of external interference and internal effects, but this approach requires complex equipment and systems and is difficult to implement. Summary of the Invention

[0005] This application provides an optical cavity locking system and method to solve the technical problem of difficulty in locking between existing high-power lasers and high-quality factor optical resonators.

[0006] The first aspect of this application provides an optical cavity-locking system, including: a laser assembly, a mode modulation assembly, an optical resonant cavity assembly, a detection assembly, and a servo controller;

[0007] The laser assembly is used to generate incident laser light and adjust the parameters of the incident laser light.

[0008] The mode control component is used to split the incident laser beam into a first laser and a second laser, and to perform modulation, frequency shifting, and optical amplification operations on the first laser and the second laser, so that the cavity power of the first laser is less than the cavity power of the second laser.

[0009] The optical resonant cavity assembly is used to generate a transmission peak signal through the first laser, and to generate a first optical signal and a second optical signal by passing through the second laser and undergoing a nonlinear process.

[0010] The detection component is used to convert the first optical signal into an intensity signal. The intensity signal is then subjected to a difference frequency operation with a microwave signal from a radio frequency signal generator to generate a difference frequency signal, which is then amplified to obtain an error signal.

[0011] The servo controller is used to receive the error signal generated by the detection component; based on the error signal, it generates a feedback signal and transmits it to the feedback actuator of the laser component, so that the deviation value of the incident laser frequency generated by the laser component relative to the resonant frequency of the optical resonant cavity component is within a set range.

[0012] In some embodiments, the laser assembly includes:

[0013] A laser used to generate incident laser light;

[0014] A feedback actuator, which is arranged in the same optical path as the laser, is used to adjust the parameters of the incident laser.

[0015] In some embodiments, the mode control component includes:

[0016] A first mode controller, which is configured with the same optical path as the laser assembly, is used to adjust the ratio of the in-cavity power of the first laser and the second laser.

[0017] A first beam splitter, which is configured with the same optical path as the first mode controller, is used to split the incident laser beam into the first laser and the second laser.

[0018] A first electro-optic modulator, which is arranged in the same optical path as the first beam splitter, is used to perform phase modulation operation on the first laser.

[0019] First high-power component: The first high-power component is arranged in the same optical path as the first beam splitter and is used to perform modulation, frequency shifting and optical amplification operations on the second laser.

[0020] The first beam combiner is arranged in the same optical path as the first high-power component and the first electro-optic modulator, and is used to combine the first laser and the second laser.

[0021] In some embodiments, the mode control component includes:

[0022] Second high-power component: The second high-power component is arranged in the same optical path as the laser component and is used for modulation and optical amplification of the laser.

[0023] The second mode controller, which is configured with the same optical path as the second high-power component, is used to adjust the ratio of the inlet power of the first laser and the second laser.

[0024] The second beam splitter, which is configured with the same optical path as the second mode controller, is used to split the incident laser beam into the first laser and the second laser.

[0025] The second electro-optic modulator, which is arranged in the same optical path as the second beam splitter, is used to perform phase modulation operation on the first laser.

[0026] The second beam combiner is arranged in the same optical path as the second beam splitter and the second electro-optic modulator, and is used to combine the first laser and the second laser.

[0027] In some embodiments, the optical resonant cavity assembly includes:

[0028] An optical resonant cavity, which is arranged in the same optical path as the mode control component, is used to generate a transmission peak signal through the first laser and to transmit the second laser and undergo a nonlinear process.

[0029] The third beam splitter is arranged in the same optical path as the optical resonant cavity and the detection component, and is used to split the light beam transmitted through the optical resonant cavity to obtain a first optical signal and a second optical signal.

[0030] In some embodiments, the detection component includes: a photodetector, a mixer, a radio frequency signal generator, a bandpass filter, and a low-noise amplifier;

[0031] The photodetector and the third beam splitter are arranged in the same optical path and are used to convert the first optical signal into an intensity signal;

[0032] The mixer is communicatively connected to the photodetector and is used to perform difference frequency calculation on the intensity signal and the microwave signal from the radio frequency signal generator to generate a difference frequency signal and output it.

[0033] The radio frequency signal generator is communicatively connected to the mode modulation component and the mixer, and is used to transmit a microwave signal of a set frequency to the electro-optic modulator and the mixer.

[0034] The bandpass filter is communicatively connected to the mixer and is used to filter the difference frequency signal;

[0035] The low-noise amplifier is communicatively connected to the bandpass filter and is used to amplify the difference frequency signal to obtain an error signal.

[0036] In some embodiments, the second optical signal can be applied after being emitted through the optical resonant cavity group; the applications include: lidar, gas detection, and optical atomic clock.

[0037] A second aspect of this application provides an optical cavity locking method, applied to an optical cavity locking system as described in any one of the first aspects above, comprising:

[0038] The laser assembly and mode control assembly are adjusted so that the cavity power of the first laser is less than that of the second laser. The beams are combined and transmitted through the optical resonant cavity assembly to generate a second optical signal and a transmission peak signal. The transmission peak signal is then converted into an intensity signal by a photodetector. The frequency of the microwave signal is set according to the frequency of the intensity signal. The difference frequency signal is obtained by performing difference frequency calculation on the intensity signal and the microwave signal using a mixer.

[0039] The difference frequency signal is filtered by a bandpass filter and then input to a low-noise amplifier to convert the frequency drift to obtain an error signal.

[0040] Based on the error signal, the servo controller generates a feedback signal and transmits it to the feedback actuator of the laser assembly, so that the deviation between the frequency of the incident laser generated by the laser assembly and the cavity resonant frequency is within a set range.

[0041] In some embodiments, the step of adjusting the laser assembly and mode control assembly such that the cavity power of the first laser is less than the cavity power of the second laser, and generating a second optical signal and a transmission peak signal by combining the beams through the optical resonator assembly, includes:

[0042] Adjust the incident laser power generated by the laser assembly and the mode controller within the mode control assembly until the cavity power of the first laser is less than the cavity power of the second laser.

[0043] The high-power component within the mode control assembly is adjusted to cause the second laser to undergo a nonlinear process in the resonant cavity assembly, thereby obtaining a second optical signal; the second optical signal can be used in applications including lidar, gas detection, and optical atomic clocks.

[0044] This application provides an optical cavity-locking system and method. The system includes a laser assembly, a mode control assembly, an optical resonant cavity assembly, a detection assembly, and a servo controller. The laser assembly generates an incident laser and adjusts its parameters. The mode control assembly splits the incident laser into a first laser and a second laser, and modulates, frequency-shifts, and amplifies the first and second lasers to make the cavity power of the first laser less than that of the second laser. The optical resonant cavity assembly transmits the first laser to generate a transmission peak signal and transmits the second laser, undergoing a nonlinear process to obtain a first optical signal and a second optical signal. The detection assembly converts the first optical signal into an intensity signal, and performs a difference frequency operation with a microwave signal from a radio frequency signal generator to generate a difference frequency signal. The error signal is amplified and obtained; the servo controller is used to receive the error signal generated by the detection component; based on the error signal, a feedback signal is generated and transmitted to the feedback actuator of the laser component, so that the deviation value of the incident laser frequency generated by the laser component relative to the resonant frequency of the optical resonant cavity component is within a set range, so as to solve the reference cavity locking problem in high-power applications through single-cavity polarization multiplexing or wavelength division multiplexing mode, and to realize the relatively independent application of low-power signal and high-power signal by utilizing the polarization separation or wavelength division multiplexing characteristics of optical resonant cavity, that is: low-power signal is used to lock the optical resonant cavity, and high-power signal is used for the occurrence of nonlinear process in cavity; without affecting the nonlinear process and high-power application, the laser frequency can be accurately locked, further improving the relative stability of laser frequency. Attached Figure Description

[0045] To more clearly illustrate the technical solution of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a first schematic diagram of the optical cavity locking system in this application;

[0047] Figure 2 This is a second schematic diagram of the optical cavity locking system in this application;

[0048] Figure 3 This is a flowchart illustrating the optical cavity locking system in one embodiment of the present application.

[0049] Figure 4 This is a flowchart of the optical cavity locking system in another embodiment of the optical cavity locking system in this application.

[0050] Explanation of reference numerals in the attached figures:

[0051] 1-Laser assembly; 11-Laser; 12-Feedback actuator; 2-Mode control assembly; 21-First mode controller; 22-First beam splitter; 23-First high-power assembly; 24-First electro-optic modulator; 25-First beam combiner; 26-Second high-power assembly; 27-Second mode controller; 28-Second beam splitter; 29-Second electro-optic modulator; 30-Second beam combiner; 3-Optical resonator assembly; 31-Optical resonator; 32-Third beam splitter; 4-Detection assembly; 41-Photodetector; 42-Mixer; 43-RF signal generator; 44-Bandpass filter; 45-Low noise amplifier; 5-Servo controller. Detailed Implementation

[0052] To enable those skilled in the art to better understand the technical solutions in this application, the technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this application.

[0053] In some technologies, locking between high-power lasers and high-quality factor optical resonators is difficult. To address this problem, this application provides an optical cavity-locking system and method, which are described below:

[0054] For example, high-power cavity-locking technology is a key research direction in the field of optical resonators, aiming to solve the problem of stable locking of optical resonators in high-power applications. The high reflectivity of optical resonators allows for the observation of various nonlinear optical effects when high-power lasers propagate within the cavity, including but not limited to: pulsed laser generation and compression, optical parametric oscillations, and optical parametric amplification. In optical microcavities, high-power input signals can induce thermal and optical nonlinear effects, including thermal drift of the optical resonator length, thermo-optical effects, and self-modulation effects, leading to unstable mode spacing and laser waveform distortion. In high-power applications, improving system stability through cavity-locking technology is of great significance for further exploration of nonlinear optical effects and for the future development of novel optical devices and advancements in cutting-edge technologies. Therefore, high-power cavity-locking technology has broad prospects for development in the research and application of optical microcavities.

[0055] Locking optical resonators in high-power scenarios is relatively complex because high power can introduce additional thermal and optical nonlinear effects, affecting the stability and accuracy of locking. Directly locking optical resonators in high-power scenarios using traditional cavity-locking techniques leads to distortion of the transmission peak and error signals, making it difficult for the feedback system to accurately identify and track the frequency and phase information within the optical cavity. This results in locking failure or significant frequency fluctuations. These effects from intracavity nonlinearities need to be overcome by adjusting signal processing algorithms or introducing additional compensation measures. Real-time dynamic adjustment of the feedback signal is required to counteract external interference and internal effects, but this approach demands complex equipment and systems, making implementation difficult.

[0056] For example, PDH (Pound-Drever-Hall) technology is a widely used and powerful laser frequency stabilization method that achieves frequency stabilization by locking the laser to a stable optical cavity. The principle of PDH frequency stabilization is as follows: the laser whose frequency needs to be stabilized is locked onto the optical cavity, thereby realizing the transfer of the stability of the reference cavity to the stability of the laser frequency.

[0057] Depend on Figure 1 As can be seen, to address the aforementioned problems, the first aspect of this application provides an optical cavity-locking system, comprising: a laser assembly 1, a mode control assembly 2, an optical resonant cavity assembly 3, a detection assembly 4, and a servo controller 5; the laser assembly 1 is used to generate an incident laser and adjust the parameters of the incident laser; the parameters include, but are not limited to, laser wavelength and laser power; the mode control assembly 2 is used to split the incident laser into a first laser and a second laser, and to perform operations including, but not limited to, modulation, frequency shifting, and optical amplification on the first laser and the second laser, such that the cavity power of the first laser is less than the cavity power of the second laser; the optical resonant cavity assembly 3 is used to generate a transmission peak signal through the first laser, and to generate a transmission peak signal through the second laser and undergo a nonlinear process to obtain a second laser. The system comprises a first optical signal and a second optical signal; the detection component 4 is used to convert the first optical signal into an intensity signal, and the intensity signal is subjected to a difference frequency operation with a microwave signal from a radio frequency signal generator to generate a difference frequency signal and amplify it to obtain an error signal; the error signal is used to reflect the deviation between the frequency of the incident laser and the resonant frequency of the optical resonant cavity component; the servo controller 5 is used to receive the error signal generated by the detection component 4; based on the error signal, a feedback signal is generated and transmitted to the feedback actuator 12 of the laser component 1, so that the deviation value of the incident laser frequency generated by the laser component 1 relative to the resonant frequency of the optical resonant cavity component 3 is within a set range; the feedback actuator 12 includes, but is not limited to: piezoelectric ceramics and acousto-optic modulators.

[0058] This application provides an optical cavity-locking system. An incident laser is generated by a laser assembly 1. The incident laser is split into a first laser and a second laser by a mode modulation assembly 2. The first and second lasers are subjected to operations including but not limited to modulation, frequency shifting, and optical amplification before being combined and incident on an optical resonant cavity assembly 3. The second laser is reflected multiple times by the optical resonant cavity 31 of the optical resonant cavity assembly 3, forming multiple interferences that enhance the intensity of certain wavelengths of light signals, thereby generating a nonlinear process to prepare for subsequent applications, such as the generation of an optical frequency comb or frequency doubling. The first laser generates a transmission peak signal within the optical resonant cavity assembly 3 to prepare for subsequent feedback. After beam combining, the first and second lasers are split into a first optical signal and a second optical signal by the output of the optical resonant cavity assembly 3. The second optical signal can then be used for subsequent applications, such as generating an optical frequency comb, which can be used for lidar, gas detection, etc. The first optical signal is converted by photoelectric conversion by the detection assembly 4 and then mixed with a microwave signal to generate an error signal. Finally, the servo controller 5 generates a feedback signal and sends it to the feedback actuator of the laser assembly 1 to suppress the frequency drift of the laser output by the laser assembly 1, so that the deviation of the laser output frequency of the laser assembly 1 from the resonant frequency of the optical resonant cavity assembly 3 is within a set range.

[0059] In this embodiment, the laser assembly 1 includes, but is not limited to: a laser 11 for generating incident laser light; and a feedback actuator 12, which is arranged along the same optical path as the laser 11 and is used to adjust the parameters of the incident laser light.

[0060] Depend on Figure 3It is understood that the mode control component 2 includes, but is not limited to: a first mode controller 21, which is set in the same optical path as the laser component 1 and is used to adjust the ratio of the input power of the first laser and the second laser; the first mode controller 21 is an optical device that can change the polarization state or frequency of light waves, and by adjusting the polarization state or frequency of light waves, the power and characteristics of the laser can be controlled. A first beam splitter 22, which is set in the same optical path as the first mode controller 21 and is used to split the incident laser into the first laser and the second laser. A first electro-optic modulator 24, which is set in the same optical path as the first beam splitter 22 and is used to perform phase modulation operations on the first laser; phase modulation is an important information transmission method that transmits information by changing the phase of the laser. A first high-power component 23, which is set in the same optical path as the first beam splitter 22 and is used to perform modulation, frequency shifting, optical amplification, and other operations on the second laser; the purpose of modulating the second laser is to modulate the intensity, frequency, phase, or polarization state of the second laser to achieve subsequent nonlinear processes. The modulation methods include: (1) frequency modulation: using a modulator to change the frequency of the laser to achieve frequency conversion; (2) phase modulation: using a modulator to modulate the phase of the laser for beat frequency measurement; the ratio of the cavity power of the first laser and the second laser needs to be relatively large, and the power of the second laser can be amplified by the first high-power component 23; the first beam combiner 25 is set in the same optical path as the first high-power component 23 and the first electro-optic modulator 24, and is used to combine the first laser and the second laser. For example, in this application, the first mode controller 21 is provided with two types, one is a polarization controller and the other is an optical switch; the first beam splitter 22 is provided with two types, one is a polarization beam splitter and the other is a wavelength division multiplexer; the first high-power component 23 is an optical fiber amplifier or an electro-optic frequency shifter; the beam combiner 25 is provided with two types, one is a polarization beam combiner and the other is a general beam combiner.

[0061] For example, when the mode control component 2 includes: a polarization controller (i.e., a first mode controller 21) and a polarization beamsplitter (i.e., a first beamsplitter 22), a first high-power component 23 is an optical fiber amplifier, and a first beam combiner 25 is a polarization beam combiner, the accompanying beamsplitter component is composed of a polarization controller and a polarization beamsplitter. The main function of the polarization beamsplitter is to split the optical power while maintaining the original polarization state of the light. This achieves the separation of horizontally polarized light and vertically polarized light, with one path of lower in-cavity power used for locking and the other for high-power applications. Figure 3The flowchart shown corresponds to the various devices in the above embodiments. Laser 11 adjusts the parameters of the incident laser via feedback actuator 12, and the laser is incident on a polarization controller. The polarization controller changes the polarization state of the light wave, and then the laser is incident on a polarization beam splitter, splitting it into a lower-power first laser (horizontally polarized light) and a higher-power second laser (vertically polarized light). The horizontally polarized light is phase-modulated by a first electro-optic modulator 24; the vertically polarized light is amplified by an fiber amplifier. After the above operations, the horizontally and vertically polarized light are incident on a polarization beam combiner for beam combining. The combined light beam is incident on the optical resonant cavity assembly 3 and split into a first optical signal and a second optical signal. The horizontally polarized light generates a transmission peak signal in the optical resonant cavity assembly 3, and then is incident on the detector assembly 4 to generate an error signal that is fed back to the servo controller 5, so that the deviation of the laser frequency output by the laser assembly 1 from the resonant frequency of the optical resonant cavity assembly 3 is within a set range, thereby realizing optical cavity locking. The vertically polarized light is reflected multiple times by the optical resonant cavity 31 of the optical resonant cavity assembly 3, forming multiple interferences to enhance the intensity of certain wavelengths of light signals, thereby generating a nonlinear process, which prepares for subsequent applications, such as the generation of optical frequency combs and frequency doubling processes.

[0062] For example, the mode control component 2 further includes: an optical switch and a wavelength division multiplexer. The optical switch mainly controls the path of light of different wavelengths, thereby affecting their relative intensity. The high-power component is an electro-optic frequency shifter, and the beam combiner is a conventional beam combiner. The beam splitter component is a wavelength division multiplexer. This enables the unshifted low-power beam to be used for locking, and the frequency-shifted high-power beam to be used for subsequent applications.

[0063] Depend on Figure 4 As can be seen, the mode control component 2 includes: a second high-power component 26, which is arranged along the same optical path as the laser component 1 and is used for modulation and optical amplification of the laser; a second mode controller 27, which is arranged along the same optical path as the second high-power component 26 and is used to adjust the ratio of the input power of the first laser and the second laser; a second beam splitter 28, which is arranged along the same optical path as the second mode controller 27 and is used to split the incident laser into the first laser and the second laser; a second electro-optic modulator 29, which is arranged along the same optical path as the second beam splitter 28 and is used to modulate the phase of the first laser; and a second beam combiner 30, which is arranged along the same optical path as the second beam splitter 28 and the second electro-optic modulator 29, and is used to combine the first laser and the second laser. It is understood that the components in the mode control component 2 can also be arranged in the above manner.

[0064] For example, when the mode control component 2 further includes: a polarization controller (i.e., a second mode controller 27) and a polarization beamsplitter (i.e., a second beamsplitter 28), the second high-power component 26 is an optical fiber amplifier, and the second beam combiner 30 is a polarization beam combiner, the beamsplitter component is composed of the polarization controller and the polarization beamsplitter. The main function of the polarization beamsplitter is to split the optical power while maintaining the original polarization state of the light. This achieves the separation of horizontally polarized light and vertically polarized light, with the lower-power input path used for locking and the other path used for high-power applications. Figure 4 The flowchart shown corresponds to the various devices in the above embodiments. Laser 11 adjusts the parameters of the incident laser via feedback actuator 12, and the incident laser is then amplified in the fiber amplifier. Afterward, it is amplified by the polarization controller, which changes the polarization state of the light wave. Finally, it is amplified by the polarization beam splitter, splitting the light into a lower-power first laser (horizontally polarized light) and a higher-power second laser (vertically polarized light). The horizontally polarized light is phase-modulated by the first electro-optic modulator 24. The horizontally and vertically polarized light, after these operations, are then combined in the polarization beam combiner. The combined light beam is incident on the optical resonant cavity assembly 3 and split into a first optical signal and a second optical signal. The horizontally polarized light generates a transmission peak signal in the optical resonant cavity assembly 3, and then is incident on the detector assembly 4 to generate an error signal that is fed back to the servo controller 5, so that the deviation of the laser frequency output by the laser assembly 1 from the resonant frequency of the optical resonant cavity assembly 3 is within a set range, thereby realizing optical cavity locking. The vertically polarized light is reflected multiple times by the optical resonant cavity 31 of the optical resonant cavity assembly 3, forming multiple interferences to enhance the intensity of certain wavelengths of light signals, thereby generating a nonlinear process, which prepares for subsequent applications, such as the generation of optical frequency combs and frequency doubling processes.

[0065] Depend on Figure 2 It is understood that the optical resonant cavity assembly 3 includes, but is not limited to: an optical resonant cavity 31, which serves as a reference cavity for low-power signal frequency locking and a resonant cavity for high-power signal nonlinear effects; the optical resonant cavity 31 is arranged in the same optical path as the beam combiner 25 and is used to transmit the first laser to generate a transmission peak signal, and the optical resonant cavity 31 transmits the second laser and undergoes a nonlinear process; and a second beam splitter 32, which is arranged in the same optical path as the optical resonant cavity 31 and the detector assembly 4 and is used to split the beam transmitted through the optical resonant cavity into a first optical signal and a second optical signal.

[0066] For example, the optical resonant cavities in this application include, but are not limited to, fiber optic FP resonant cavities (FP cavities for short), air FP cavities, and ultra-low expansion coefficient glass (ULE) FP cavities. The fiber optic FP resonant cavity, also known as a Fabry-Pérot resonant cavity, consists of two parallel mirrors (or reflective surfaces) with high reflectivity. Light is reflected back and forth through these two mirrors, creating interference. At a specific wavelength, the light waves reflected multiple times form a peak signal, while light waves of other wavelengths cancel each other out.

[0067] For example, the second beam splitter 32 is configured in two types: a polarization beam splitter and a wavelength division multiplexer.

[0068] Depend on Figure 2 It is understood that the detection component 4 includes, but is not limited to: a photodetector 41, a mixer 42, a radio frequency signal generator 43, a bandpass filter 44, and a low-noise amplifier 45; the photodetector 41 is arranged in the same optical path as the second beam splitter 32 and is used to convert the first optical signal into an intensity signal; the mixer 42 is communicatively connected to the photodetector 41 and is used to perform difference frequency calculation on the intensity signal and the electrical signal from the radio frequency signal generator 43 and output a difference frequency signal; the radio frequency signal generator 43 is communicatively connected to the electro-optic modulator 24 and the mixer 42 and is used to transmit a local microwave signal of a set frequency to the electro-optic modulator 24 and the mixer 42; the bandpass filter 44 is communicatively connected to the mixer 42 and is used to filter the difference frequency signal; the low-noise amplifier 45 is communicatively connected to the bandpass filter 44 and the servo controller 5 and is used to amplify the difference frequency signal to obtain an error signal. The mixer 42 can mix two signals of different frequencies (i.e., intensity signal and microwave signal) to generate new frequency components, thus realizing frequency conversion. Through mixing, the offset information between the laser frequency and the resonant frequency can be obtained. This is usually related to parameters such as the phase and amplitude of the signal, which is crucial for the subsequent generation and correction of error signals.

[0069] For example, the specific process is as follows: The mixer 42 mixes the intensity signal in the electrical signal with the microwave signal; the mixer 42 outputs the sum and difference of the original signal frequencies to generate new frequency components; the mixed signal usually contains multiple frequency components, and it needs to be filtered to remove unwanted frequency components, retaining only the specific frequency components containing frequency and resonant frequency offset information; the filtered signal is processed to extract the frequency and resonant frequency offset information; this includes demodulation and amplification of the signal for more accurate measurement and analysis; based on the extracted frequency and resonant frequency offset information, the system can generate an error signal. This error signal is used to indicate the difference between the actual signal frequency and the desired frequency, and is the basis for subsequent correction and adjustment. The error signal is connected to the servo controller 5, which outputs a feedback signal to the feedback actuator of the laser assembly 1 to suppress the frequency drift of the laser emitted by the laser assembly 1, thereby reducing the frequency and resonant frequency offset and improving the stability and accuracy of the laser output frequency.

[0070] In this embodiment, after the second optical signal is emitted through the optical resonant cavity assembly 3, it is configured to: perform applications of the second optical signal; if an optical frequency comb is generated, the applications may include: lidar, gas detection, optical atomic clocks, etc. The lidar application includes: using pulsed lasers to perform arbitrary length measurements, accurately measuring the time difference between pulses, which depends on two moments: the start time of the pulse being emitted from the measurement system, and the cutoff time when the emitted pulse is reflected back by the object and received again by the measurement system, thus obtaining detailed information about the target object. The gas detection application includes: using an optical frequency comb to interact with gas molecules and then performing frequency domain analysis, simultaneously obtaining a wide spectral coverage and extremely high spectral resolution, completing high-precision spectral measurements.

[0071] This application provides an optical cavity-locking system and method. The system includes: a laser assembly 1 for generating an incident laser and adjusting the parameters of the laser; a mode control assembly 2 for splitting the incident laser into a first laser and a second laser, and performing operations including but not limited to modulation, frequency shifting, and optical amplification on the first and second lasers, such that the cavity power of the first laser is less than that of the second laser; an optical resonant cavity assembly 3 for transmitting the first laser to generate a transmission peak signal, transmitting the second laser and undergoing a nonlinear process, and then splitting it into a first optical signal and a second optical signal; a detection assembly 4 for converting the first optical signal into an intensity signal, performing a difference frequency operation between the intensity signal and an electrical signal from an RF signal generator, and outputting a difference frequency signal; and filtering and amplifying the difference frequency signal to obtain an error signal. The error signal is received by the servo controller 5 from the detection component 4. Based on the error signal, a feedback signal is generated and transmitted to the feedback actuator of the laser component 1 so that the deviation of the laser output frequency from the resonant frequency of the optical resonant cavity component 3 is within a set range. This achieves the solution of the reference cavity locking problem in high-power applications through single-cavity polarization multiplexing or wavelength division multiplexing. The polarization separation or wavelength division multiplexing characteristics of the optical resonant cavity enable the relatively independent application of low-power and high-power signals. That is, the low-power signal is used to lock the optical resonant cavity, and the high-power signal is used for the occurrence of nonlinear processes within the cavity. Without affecting the nonlinear process and high-power application scenarios, the laser frequency can be accurately locked, further improving the relative stability of the laser frequency.

[0072] The second aspect of this application provides an optical cavity-locking method applied to an optical cavity-locking system described in any of the above embodiments, comprising: adjusting a laser assembly and a mode control assembly such that the cavity power of a first laser is less than the cavity power of a second laser; combining the beams and transmitting them through an optical resonant cavity assembly to generate a second optical signal and a transmission peak signal; converting the transmission peak signal into an intensity signal by a photodetector; setting the frequency of a microwave signal according to the frequency of the intensity signal; performing a difference frequency operation on the intensity signal and the microwave signal using a mixer to obtain a difference frequency signal; filtering the difference frequency signal through a bandpass filter and then inputting it to a low-noise amplifier for frequency drift conversion to obtain an error signal; based on the error signal, generating a feedback signal by a servo controller and transmitting it to a feedback actuator of the laser assembly, so that the deviation between the frequency of the incident laser generated by the laser assembly and the cavity resonant frequency is within a set range. The effects of the above method embodiments can be found in the effects of the above system embodiments, and will not be repeated here.

[0073] In this embodiment, the step of adjusting the laser assembly and mode control assembly so that the cavity power of the first laser is less than that of the second laser, and then combining the beams through the optical resonant cavity assembly to generate a second optical signal and a transmission peak signal, includes: adjusting the incident laser power generated by the laser assembly and the mode controller within the mode control assembly until the cavity power of the first laser is less than that of the second laser; adjusting the high-power component within the mode control assembly so that the first laser generates a transmission peak signal in the resonant cavity assembly, and the second laser undergoes a nonlinear process in the resonant cavity assembly to obtain the second optical signal; the second optical signal can be used in applications including lidar, gas detection, and optical atomic clocks. The effects of the above method embodiment can be found in the effects of the above system embodiment, and will not be repeated here.

[0074] The above detailed embodiments further illustrate the purpose, technical solution, and beneficial effects of the embodiments of this application. It should be understood that the above are merely specific embodiments of the embodiments of this application and are not intended to limit the protection scope of the embodiments of this application. Any modifications, equivalent substitutions, improvements, etc., made on the basis of the technical solutions of the embodiments of this application should be included within the protection scope of the embodiments of this application.

Claims

1. An optical lock cavity system, characterized by, The application relates to a laser frequency stabilization system. The system comprises a laser assembly, a mode control assembly, an optical resonant cavity assembly, a detection assembly and a servo controller. The laser assembly is used for generating incident laser and adjusting parameters of the incident laser. The mode control assembly is used for splitting the incident laser into a first laser and a second laser, modulating, frequency shifting and optically amplifying the first laser and the second laser, so that the intracavity power of the first laser is less than that of the second laser. The optical resonant cavity assembly is used for generating a transmission peak signal through the first laser, transmitting the second laser and generating a first optical signal and a second optical signal through a nonlinear process. The detection assembly is used for converting the first optical signal into an intensity signal, performing frequency difference operation on the intensity signal and a microwave signal from a radio frequency signal generator to generate a frequency difference signal, amplifying the frequency difference signal to obtain an error signal. The servo controller is used for receiving the error signal generated by the detection assembly. Based on the error signal, a feedback signal is generated and transmitted to a feedback actuator of the laser assembly, so that the frequency deviation of the incident laser generated by the laser assembly relative to the resonant frequency of the optical resonant cavity assembly is within a set range. The low-power signal is used for locking the optical resonant cavity, and the high-power signal is used for generating the nonlinear process in the cavity; the precise locking of the laser frequency and the improvement of the stability of the laser frequency are realized without affecting the nonlinear process and the high-power scene.

2. An optical cavity system according to claim 1, wherein The laser assembly comprises a laser used for generating incident laser, and a feedback actuator arranged in the same optical path as the laser and used for adjusting parameters of the incident laser. The mode control assembly comprises a first mode controller arranged in the same optical path as the laser assembly and used for adjusting the intracavity power ratio of the first laser and the second laser, a first beam splitter arranged in the same optical path as the first mode controller and used for splitting the incident laser into the first laser and the second laser, a first electro-optical modulator arranged in the same optical path as the first beam splitter and used for modulating the phase of the first laser, and a first high-power assembly arranged in the same optical path as the first beam splitter and used for modulating, frequency shifting and optically amplifying the second laser. The mode control assembly comprises a first combiner arranged in the same optical path as the first high-power assembly and the first electro-optical modulator respectively and used for combining the first laser and the second laser.

3. An optical cavity system according to claim 1, wherein The mode control assembly comprises a second high-power assembly arranged in the same optical path as the laser assembly and used for modulating and optically amplifying the laser, a second mode controller arranged in the same optical path as the second high-power assembly and used for adjusting the intracavity power ratio of the first laser and the second laser, and a second beam splitter arranged in the same optical path as the second mode controller and used for splitting the incident laser into the first laser and the second laser. ​ ​ ​ ​ ​ 4. An optical cavity system according to claim 1, wherein ​ ​ ​ ​ A second electro-optical modulator is arranged in optical path with the second beam splitter, for performing a modulated phase operation on the first laser; A second beam combiner is arranged in optical path with the second beam splitter and the second electro-optical modulator, for combining the first laser and the second laser.

5. An optical cavity system according to claim 1, wherein The optical resonant cavity assembly comprises: An optical resonant cavity is arranged in optical path with the mode control assembly, for generating a transmission peak signal by the first laser, and for transmitting the second laser and causing a nonlinear process; A third beam splitter is arranged in optical path with the optical resonant cavity and the detection assembly, for splitting the light beam transmitted by the optical resonant cavity to obtain a first optical signal and a second optical signal.

6. An optical cavity system according to claim 5, wherein The detection assembly comprises a photodetector, a frequency mixer, a radio frequency signal generator, a band-pass filter, and a low-noise amplifier. The photodetector is arranged in optical path with the third beam splitter, for converting the first optical signal into an intensity signal; The frequency mixer is communicatively connected with the photodetector, for performing a difference frequency operation on the intensity signal and a microwave signal from the radio frequency signal generator to generate a difference frequency signal and output the difference frequency signal; The radio frequency signal generator is communicatively connected with the mode control assembly and the frequency mixer, for emitting a microwave signal with a set frequency to the mode control assembly and the frequency mixer; The band-pass filter is communicatively connected with the frequency mixer, for filtering the difference frequency signal; The low-noise amplifier is communicatively connected with the band-pass filter, for amplifying the difference frequency signal to obtain an error signal.

7. An optical cavity system according to claim 1, wherein The second optical signal after being emitted by the optical resonant cavity assembly can be applied, and the application includes laser radar, gas detection, and optical atomic clock.

8. An optical trapping method applied to an optical trapping system according to any one of claims 1 to 7, characterized in that, The method comprises: Adjusting the laser assembly and the mode control assembly so that the in-cavity power of the first laser is less than the in-cavity power of the second laser, combining and transmitting through the optical resonant cavity assembly to generate a second optical signal and a transmission peak signal, converting the transmission peak signal into an intensity signal by a photodetector, setting the frequency of a microwave signal according to the frequency of the intensity signal, performing a difference frequency operation on the intensity signal and the microwave signal by a frequency mixer to obtain a difference frequency signal; After the difference frequency signal is filtered by a band-pass filter, the difference frequency signal is input to a low-noise amplifier to convert the frequency drift to obtain an error signal; Based on the error signal, a feedback signal is generated by a servo controller and transmitted to a feedback actuator of the laser assembly, so that the frequency deviation between the incident laser generated by the laser assembly and the cavity resonance frequency is within a set range.

9. An optical cavity method according to claim 8, wherein, The step of adjusting the laser assembly and the mode control assembly so that the in-cavity power of the first laser is less than the in-cavity power of the second laser, and combining and transmitting through the optical resonant cavity assembly to generate a second optical signal and a transmission peak signal, comprises: Adjusting the incident laser power generated by the laser assembly and the mode controller in the mode control assembly until the in-cavity power of the first laser is less than the in-cavity power of the second laser; Adjusting the high-power component in the mode regulation component, so that the first laser generates a transmission peak signal in the resonant cavity component, and the second laser generates a second optical signal by a nonlinear process in the resonant cavity component; the second optical signal can be applied, and the application includes: laser radar, gas detection, optical atomic clock.

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