A laser frequency stabilization front-end light source system and device

Abstract

The present application belongs to the technical field of laser frequency stabilization light source, aiming at the defects of the existing iodine molecule, such as poor anti-interference, poor repeatability, difficult integration, high operation and maintenance cost and unable to be applied in batches, a laser frequency stabilization front-end light source system and device are provided. The system is matched with special optical path module, modulation and frequency multiplication device, and three light beams of monitoring, pumping and detection are divided, and differential optical path design suitable for the MTS principle of the present application is adopted; at the same time, all-optical fiber closed fusion optical path is adopted, all devices are integrated, and temperature control, driving and monitoring units are equipped. The product has the advantages of compact structure, strong stability, anti-interference, no need for frequent debugging, low operation and maintenance cost, convenient miniaturization integration and batch use, and can be used in precise optical measurement, quantum communication and other high-precision laser frequency stabilization scenes.

Description

Technical Field

[0001] This invention relates to the field of laser frequency stabilization technology, and in particular to a laser frequency stabilization front-end light source system and device, adapted to the 532nm iodine molecule modulation transfer spectroscopy (MTS) atomic frequency standard stabilization scenario, for achieving ultra-high precision and long-term stability locking of laser frequency. Background Technology

[0002] Iodine molecule transition lines are the core reference frequency source for constructing laser frequency standards. Among various laser frequency stabilization technologies, modulation-transfer spectroscopy (MTS) stabilization technology has the best overall performance. Compared with saturated absorption spectroscopy and frequency modulation spectroscopy, this technology has excellent noise suppression capabilities and can output high-quality frequency-locking error signals, making it widely used in various high-precision laser frequency stabilization scenarios. The 532nm iodine molecule MTS frequency stabilization system is divided into two parts: a front-end optical path and a back-end optical path. The front-end optical path generates a 1064nm single-frequency laser. After parameter adjustment, optical field modulation, and frequency doubling of the laser, it outputs a pump light with a modulated signal and an unmodulated probe light, respectively. The back-end optical path guides the two beams into an iodine vapor cell to complete spectral interaction, collects the frequency error signal, and achieves precise laser frequency locking through a servo control circuit. To ensure that the system obtains a high signal-to-noise ratio probe signal, the front-end optical path must strictly meet several technical indicators, including narrow laser linewidth, stable and adjustable optical power and beam splitting ratio, and the modulation signal being loaded only onto the pump light, while ensuring long-term stability of the optical field mode and polarization state of the frequency-doubled output beam.

[0003] Currently, the front-end optical path of existing iodine molecule MTS frequency stabilization systems generally adopts an architecture combining spatial optical path and local fiber coupling. The mainstream technical solution is as follows: an 808nm semiconductor laser is used as the pump source to excite an Nd:YAG solid-state laser to generate a 1064nm single-frequency laser. The 1064nm fundamental frequency laser is second-harmonicized by a frequency doubling crystal to output a 532nm laser beam. The 532nm beam is collimated and beam-expanded by a spatial optical system, and then split by a spatial polarization beam splitter prism (PBS) to obtain a high-power pump beam and a low-power probe beam. A spatial acousto-optic modulator (AOM) and a spatial electro-optic modulator (EOM) are connected in series in the pump optical path to realize beam power control, beam frequency shift, and phase modulation functions, respectively. The optical path structure mainly relies on a large number of discrete large-volume spatial optical components such as mirrors, lenses, and waveplates to complete the free space transmission and light field shaping of the beam. All optical components are distributed and installed on the optical platform. The beam transmission between components is in free space transmission mode. The alignment accuracy of the optical path needs to be repeatedly adjusted. Only at the output end of the front-end optical path is a local fiber coupling method used to guide the prepared pump light and probe light into the subsequent iodine spectral unit to realize the spectral detection and laser frequency stabilization functions of the system.

[0004] In practical engineering applications, the existing iodine-based MTS front-end optical path structure has many inherent defects, which seriously restrict the system's integration and engineering application. Specifically, these defects include: inability to achieve modular integration; complex optical path debugging and alignment processes; high sensitivity of free-space optical paths to external environmental disturbances; poor long-term system stability; high degree of customization in optical path configuration; difficulty in repeated assembly; and poor consistency and repeatability of equipment performance. Summary of the Invention

[0005] The present invention aims to provide a laser frequency stabilization front-end light source system and device, which solves the problems of poor stability, low optical path repeatability, high integration difficulty and weak engineering adaptability caused by the discrete structure of the existing iodine molecule MTS frequency stabilization optical path. It realizes the miniaturization and integration of the laser frequency stabilization front-end light source, high stable operation, no daily maintenance and rapid engineering deployment.

[0006] To achieve the above objectives, this invention provides a laser frequency stabilization front-end light source system for iodine molecule modulation transfer spectrum frequency stabilization, comprising a pump source module, a narrow-linewidth laser oscillator, a first beam splitting unit, a second beam splitting unit, a first acousto-optic modulator, an electro-optic modulator, a second acousto-optic modulator, a first frequency doubling crystal, and a second frequency doubling crystal; the pump source module is optically connected to the narrow-linewidth laser oscillator; the narrow-linewidth laser oscillator incorporates a temperature control circuit, a current control circuit, and collimation-coupled optical components, and the output laser is transmitted to the first beam splitting unit via a polarization-maintaining fiber; the first beam splitting unit divides the incident laser into a probe beam and a branch beam, the branch beam being incident on the first... The beam splitter divides the laser into a monitoring optical path and a pump beam. The monitoring optical path is used to monitor the laser output status and output a feedback signal. The pump beam passes sequentially through a first acousto-optic modulator, an electro-optic modulator, and a first frequency-doubling crystal. The first acousto-optic modulator is used to control the pump beam power. The electro-optic modulator receives an external radio frequency drive signal and performs phase modulation on the pump beam. The first frequency-doubling crystal doubles the phase-modulated fundamental frequency pump beam and outputs the frequency-doubled pump beam. The probe beam is sequentially transmitted to a second acousto-optic modulator and a second frequency-doubling crystal. The second frequency-doubling crystal doubles the fundamental frequency probe beam and outputs the frequency-doubled probe beam without phase modulation.

[0007] Optionally, the pump light source module adopts an 808nm seed light source module, and the narrow linewidth laser oscillator is a 1064nm narrow linewidth laser oscillator NPRO. The output end of the 808nm seed light source module is optically connected to the 1064nm narrow linewidth laser oscillator NPRO through fiber optic fusion splicing.

[0008] Optionally, both the first and second beam splitting units employ 1:9 polarization-maintaining fiber beam splitters; the high-power output end of the first beam splitting unit and the input end of the second beam splitting unit are fused together, and the low-power output end forms the input port of the detection end; the low-power output end of the second beam splitting unit forms the monitoring end, and the high-power output end forms the pump end input port, thereby achieving precise beam power splitting and optical path partitioning output.

[0009] Optionally, the first and second acousto-optic modulators are both fiber optic acousto-optic modulators, and the electro-optic modulator is a fiber optic electro-optic modulator; the pump input port is connected in series with the first acousto-optic modulator, the fiber optic electro-optic modulator, and the first frequency doubling crystal via fiber optic fusion splicing, and the probe input port is connected in series with the second acousto-optic modulator and the second frequency doubling crystal via fiber optic fusion splicing, forming two independent integrated fiber optic paths.

[0010] Optionally, the fiber electro-optic modulator is connected to a local oscillator radio frequency drive signal to perform phase modulation on the pump beam and generate modulation sidebands, while the probe beam is free from phase modulation throughout, thus meeting the requirements for frequency stabilization of iodine molecule modulation transfer spectrum.

[0011] Optionally, both the first and second frequency doubling crystals are used to complete the second frequency conversion from 1064nm fundamental frequency light to 532nm frequency doubling light, and both frequency doubling crystals are equipped with precision temperature control circuits.

[0012] Optionally, the precision temperature control circuit adopts a closed-loop temperature control mode, which can dynamically adjust the operating temperature of the frequency doubling crystal in real time, effectively improving the frequency doubling conversion efficiency and operating stability of the crystal.

[0013] Optionally, the driving circuits of the first acousto-optic modulator, the second acousto-optic modulator, and the fiber electro-optic modulator are integrated into a single driving module; the driving module has a reserved external control interface, which can configure core parameters such as modulation depth and acousto-optic driving power through external devices.

[0014] Optionally, it also includes a monitoring unit, which leads out a 1064nm monitoring optical path through the second beam splitter. The monitoring unit has a built-in photodetector and an external wavelength meter, which can collect and monitor laser power fluctuation and wavelength change data in real time.

[0015] Furthermore, to achieve the above objectives, the present invention also provides a laser frequency stabilization front-end light source device, applied to the aforementioned laser frequency stabilization front-end light source system, comprising a mounting frame, an optical fiber tray, and an aluminum base plate; all optical fiber devices within the system are positioned and fixed by the mounting frame, the optical fiber lines are neatly routed via the optical fiber tray, and all functional devices and corresponding mounting frames are integrated and mounted on the aluminum base plate; the devices are connected by optical fiber jumpers, all optical path nodes are treated with optical fiber fusion splicing and sealed and fitted with protective sleeves, and the core functional devices are limited and fixed by clamps, forming an integrated all-fiber integrated light source structure.

[0016] Optionally, the device is equipped with an integrated monitoring unit, which collects laser power fluctuation data and wavelength change data in real time through the 1064nm optical path led out by the second beam splitting unit, so as to realize the full-process monitoring of the working status of the light source.

[0017] Optionally, the device has a built-in integrated drive module that integrates the drive circuits of the first acousto-optic modulator, the second acousto-optic modulator, and the fiber electro-optic modulator, and reserves an external control interface to adapt to an external frequency stabilization control system to complete parameter configuration and collaborative operation.

[0018] Optionally, the frequency doubling crystal of the device is equipped with a precision temperature control circuit, which dynamically regulates the crystal's operating temperature through closed-loop temperature control to ensure the conversion efficiency and long-term stability of the 1064nm fundamental frequency light to 532nm frequency doubling light.

[0019] The beneficial effects of this invention are: The laser frequency stabilization front-end light source system and device proposed in this invention, through a novel optical path architecture design and integrated structure, specifically solves the technical problems of poor stability, low repeatability, high integration difficulty, and high operation and maintenance costs caused by the existing discrete optical path structure of iodine molecule MTS frequency stabilization. The specific beneficial effects are as follows: This invention integrates core optical components such as the pump source module, narrow linewidth laser oscillator, first beam splitting unit, second beam splitting unit, acousto-optic modulator, electro-optic modulator, and frequency doubling crystal into a closed, integrated fiber optic path through fiber fusion splicing, replacing the traditional spatial discrete optical path structure. The closed polarization-maintaining fiber optic path can completely isolate the interference of external vibrations, airflow, and temperature fluctuations on laser transmission, thoroughly avoiding problems such as optical path offset and spot distortion that are prone to occur in discrete optical paths. This ensures that the power parameters and transmission modes of the pump beam and probe beam remain constant and stable over a long period of time, effectively improving the signal-to-noise ratio of the iodine molecule modulation transfer spectrum (MTS) error signal, and fundamentally improving the stability and reliability of laser frequency locking.

[0020] This invention employs two sets of 1:9 polarization-maintaining fiber beam splitters to form the first and second beam splitting units, achieving precise splitting of the incident laser beam and independently dividing it into three functional optical paths: a pump optical path, a probe optical path, and a monitoring optical path. It strictly matches the system's optical path design logic, deploying a fiber electro-optic modulator only in the pump optical path to complete phase modulation and generate modulation sidebands. The probe optical path remains in a phase-free state throughout, precisely matching the core working principle of iodine molecule modulation-transfer spectroscopy, ensuring the effectiveness of the frequency-stabilized signal and the accuracy of detection. Simultaneously, the pump and probe optical paths are deployed independently, effectively eliminating beam crosstalk problems and further optimizing laser frequency stabilization accuracy.

[0021] This invention utilizes an aluminum base plate, a dedicated mounting frame, and an optical fiber tray to achieve the standardized integration of all functional components. Combined with fiber optic splicing and sealing, protective sleeves, and clamping and limiting mechanisms, it integrates various dispersed optical fiber devices and optical components into a standardized integrated module. This significantly reduces the overall system size, achieving the advantages of miniaturized and portable equipment for engineering applications. Furthermore, this standardized all-fiber integrated structure eliminates the need for manual daily optical path alignment and debugging, freeing it from reliance on operators' professional experience. This significantly improves the consistency and repeatability of optical path operation, supports mass production of equipment, and effectively reduces the overall cost of system engineering deployment and subsequent maintenance.

[0022] This invention provides precision temperature control circuits for the first and second frequency-doubling crystals. Through a closed-loop temperature control mode, the operating temperature of the frequency-doubling crystals is precisely adjusted, stabilizing the second-harmonic conversion efficiency from the 1064nm fundamental frequency light to the 532nm frequency-doubled light, ensuring the stability of the frequency-doubling output from both optical paths. Simultaneously, the driving circuits of the first and second acousto-optic modulators and the fiber electro-optic modulator are integrated into a single driving module. Through a reserved external control interface, core operating parameters such as modulation depth and acousto-optic driving power can be flexibly configured to adapt to different laser frequency stabilization scenarios. Furthermore, the system is equipped with an independent monitoring unit. A 1064nm monitoring optical path is led out through the second beam splitter unit. Relying on a built-in photodetector and an external wavelength meter, real-time data on laser power and wavelength fluctuations can be collected, enabling dynamic monitoring and feedback adjustment of the light source's operating status. This effectively improves the long-term reliability and adaptability to complex environments of the entire system.

[0023] This invention uses a standardized fiber optic interface to connect the front-end light source system with the back-end iodine spectroscopy unit, making disassembly, integration, and replacement convenient. It can be quickly adapted to various iodine molecule MTS laser frequency stabilization systems, greatly improving the equipment's versatility and engineering adaptability. At the same time, it facilitates subsequent system function upgrades and large-scale industrial application. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the system architecture of the present invention; Figure 2This is a schematic diagram of the device structure of the present invention.

[0025] In the figure: 1 Aluminum base plate; 2 Second acousto-optic modulator; 3 Fiber optic disk; 4 Second beam splitting unit; 5 Electro-optic modulator; 6 First acousto-optic modulator; 7 Fiber optic line; 8 Narrow linewidth laser oscillator; 9 First frequency doubling crystal; 10 Second frequency doubling crystal; 11 First beam splitting unit; 12 Pump light source module. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] In related technologies, laser frequency stabilization technology relies on temperature control and cavity length adjustment to compensate for environmental disturbances, thereby stabilizing the laser frequency and compressing the linewidth, and is widely used in the field of precision lasers. Current laser frequency stabilization schemes based on iodine molecule modulation transfer spectroscopy mostly employ discrete spatial optical structures, which suffer from problems such as susceptibility to environmental influences, poor frequency locking performance, large equipment size, low integration, difficulty in debugging and replication, and lack of real-time monitoring and control functions. Therefore, this invention proposes a laser frequency stabilization front-end light source system and device to solve many of the shortcomings of existing technologies.

[0028] First embodiment: Reference Figure 1 The first embodiment of the present invention provides a laser frequency stabilization front-end light source system, the front-end light source laser frequency stabilization system comprising: a pump light source module 12, a narrow linewidth laser oscillator 8, a first beam splitting unit 11, a second beam splitting unit 4, a first acousto-optic modulator 6, an electro-optic modulator 5, a second acousto-optic modulator 2, a first frequency doubling crystal 9, and a second frequency doubling crystal 10.

[0029] The pump source module 12 is optically connected to the narrow linewidth laser oscillator 8, providing stable pump energy to ensure laser oscillation and output. The narrow linewidth laser oscillator 8 incorporates a temperature control circuit, a current control circuit, and a collimation-coupled optical component. The output laser is transmitted to the first beam splitting unit 11 via a polarization-maintaining fiber. The temperature control circuit and current control circuit enable precise control of the laser oscillator's operating state, suppressing frequency drift of the light source itself. The collimation-coupled optical component collimates and shapes the output laser and couples it to the fiber, ensuring high-quality, low-loss laser transmission.

[0030] The first beam splitting unit 11 splits the incident laser into a probe beam and a branch beam; the branch beam is incident on the second beam splitting unit 4, which splits the monitoring optical path and the pump beam. The monitoring optical path is used to monitor the laser output status and output feedback signals, so as to realize real-time monitoring of parameters such as laser power and wavelength of the entire optical path, and provide data support for closed-loop frequency stabilization of the system.

[0031] The pump beam passes sequentially through a first acousto-optic modulator 6, an electro-optic modulator 5, and a first frequency doubling crystal 9. The first acousto-optic modulator 6 regulates the power of the pump beam to achieve precise and stable pump light power. The electro-optic modulator 5 receives an external radio frequency drive signal and performs phase modulation on the pump beam, causing the pump light to carry a specific modulation sideband. The first frequency doubling crystal 9 doubles the phase-modulated fundamental frequency pump light and outputs frequency-doubled pump light, meeting the light source band requirements for frequency stabilization of iodine molecule modulation transfer spectrum.

[0032] The probe beam is sequentially transmitted to the second acousto-optic modulator 2 and the second frequency doubling crystal 10. The second frequency doubling crystal 10 doubles the fundamental frequency probe beam and outputs a frequency doubling probe beam that has not undergone phase modulation, so that the final output pump frequency doubling beam and the probe frequency doubling beam form a difference in modulation characteristics, which is in line with the core working principle of MTS frequency stabilization technology.

[0033] This embodiment presents the core architecture of a laser frequency stabilization system. By constructing a dual-optical-path independent control structure, it achieves differentiated output of pump light phase modulation and probe light unmodulated output, precisely matching the operational requirements of iodine molecule modulation transfer spectrum frequency stabilization. A two-stage beam splitting structure enables partitioned multiplexing of the laser beam, completing the separation of the pump and probe beams required for frequency stabilization while reserving a laser state monitoring optical path, thus balancing the needs of light source stability monitoring and frequency stabilization. Simultaneously, through the hierarchical coordination of an acousto-optic modulator, an electro-optic modulator, and a frequency doubling crystal, it achieves multi-dimensional precise control of laser power, phase, and wavelength, ensuring the accuracy and stability of laser frequency stabilization from the optical path principle.

[0034] As a preferred embodiment, the pump light source module 12 adopts an 808nm seed light source module, and the narrow linewidth laser oscillator 8 is a 1064nm narrow linewidth laser oscillator NPRO. The output end of the 808nm seed light source module is optically connected to the 1064nm narrow linewidth laser oscillator NPRO through fiber optic fusion splicing.

[0035] The 808nm seed light source module is a commercially mature pump light source with stable output beam quality and high spectral purity. It can be used as a stable pump source to excite a 1064nm narrow-linewidth laser oscillator (NPRO). The NPRO oscillator features a single longitudinal mode, ultra-narrow linewidth, and low frequency drift, making it the preferred light source for precision laser frequency stabilization applications. The two components are connected using fiber optic fusion splicing, which, compared to spatial docking, completely eliminates optical path misalignment and air disturbance interference, achieving lossless and highly stable optical path conduction.

[0036] The combination of an 808nm seed light source pumping a 1064nm NPRO narrow-linewidth laser ensures that the laser source possesses the fundamental characteristics of ultra-narrow linewidth, low noise, and low drift, improving the laser output quality from the source and laying the foundation for subsequent high-precision frequency stabilization. The fiber optic fusion splicing method abandons the traditional spatial optical path docking mode, resulting in extremely low optical path loss and strong structural stability. It effectively avoids laser power fluctuations and mode distortions caused by light source docking deviations, significantly improving the reliability of the light source during long-term operation.

[0037] As a preferred embodiment, both the first beam splitter 11 and the second beam splitter 4 employ a 1:9 polarization-maintaining fiber beam splitter; the high-power output end of the first beam splitter 11 is fused with the fiber at the input end of the second beam splitter 4, and the low-power output end forms the input port of the detector end; the low-power output end of the second beam splitter 4 forms the monitoring end, and the high-power output end forms the pump end input port, thereby achieving precise beam power splitting and optical path partitioning output.

[0038] The 1:9 polarization-maintaining fiber beam splitter possesses polarization-preserving characteristics, maximizing the preservation of the polarization state of the incident laser and preventing polarization distortion during beam splitting from affecting frequency stabilization accuracy. The first beam splitting unit 11 splits the beam at a 1:9 power ratio. The low-power beam serves as the probe beam, meeting the low-power, high-sensitivity requirements of the probe optical path. The high-power beam is fed into the second beam splitting unit 4 for secondary splitting. The second beam splitting unit 4 again splits the beam at a 1:9 ratio. The low-power beam is extracted as the monitoring beam, used only for status monitoring and not affecting the main optical path operation. The high-power beam serves as the pump beam, providing sufficient energy for the core frequency stabilization optical path. Both beam splitters are interconnected using fiber fusion splicing, eliminating ionized space in the optical path and ensuring precise and consistent splitting ratios.

[0039] Employing a 1:9 polarization-maintaining fiber beam splitter as the core component, it can precisely achieve laser power distribution and splitting, matching the differentiated power requirements of the pump, probe, and monitoring optical paths, and avoiding power overload or insufficient power affecting the operation of the optical paths. The polarization-maintaining characteristic can keep the laser polarization state stable throughout the process, eliminating MTS error signal distortion caused by polarization drift. The two-stage fiber fusion splicing beam splitting structure has no manual alignment error, high beam splitting accuracy, and good repeatability, which can ensure consistent optical path output parameters under different operating conditions, improving the system's frequency stabilization effect and batch consistency.

[0040] As a preferred embodiment, the first acousto-optic modulator 6 and the second acousto-optic modulator 2 are both fiber optic acousto-optic modulators, and the electro-optic modulator 5 is a fiber optic electro-optic modulator. The pump input port is connected in series with the first acousto-optic modulator 6, the fiber optic electro-optic modulator, and the first frequency doubling crystal 9 via fiber optic fusion splicing. The probe input port is connected in series with the second acousto-optic modulator 2 and the second frequency doubling crystal 10 via fiber optic fusion splicing, forming two independent integrated fiber optic paths.

[0041] In this embodiment, the traditional spatial acousto-optic modulator and electro-optic modulator 5 are replaced with fiber-optic integrated devices. All devices are connected in series via fiber optic fusion splicing, completely eliminating the free-space optical path. The pump optical path and the probe optical path are completely independent and do not interfere with each other: the pump optical path achieves integrated processing of power control, phase modulation, and frequency doubling conversion, while the probe optical path achieves independent power control and frequency doubling conversion. The two optical paths have a regular structure and clear function, and the entire process is a closed fiber optic transmission structure.

[0042] The all-fiber modulation device, combined with fiber fusion splicing network, completely eliminates problems such as optical axis misalignment, airflow disturbance, and mechanical vibration in the free space optical path, significantly improving the optical path's anti-interference capability. The two independent integrated fiber optical paths enable independent control of the pump light and probe light, avoiding crosstalk and ensuring that phase modulation only acts on the pump light, accurately meeting the requirements of the MTS frequency stabilization principle. The fiber integrated structure has low optical path loss and strong beam mode stability, with no significant attenuation of beam quality under long-term operation, effectively improving the long-term reliability of the frequency stabilization system.

[0043] Furthermore, the fiber electro-optic modulator is connected to the local oscillator radio frequency drive signal to perform phase modulation on the pump beam and generate modulation sidebands, while the probe beam is phase-free throughout its entire range.

[0044] During system operation, only the pump optical path uses a series-connected fiber electro-optic modulator. After the local oscillator RF drive signal is input to the electro-optic modulator, the 1064nm fundamental frequency pump light can be precisely phase-modulated to generate a stable modulation sideband. The probe optical path, however, does not have any phase modulation device; the probe light maintains its original fundamental frequency characteristics throughout the entire path, and after frequency doubling, it outputs an unmodulated 532nm probe light. The final beam entering the iodine cell consists of the frequency-doubled pump light with modulation sidebands and the unmodulated frequency-doubled probe light, forming a stable modulation transfer signal.

[0045] Through differentiated phase modulation design, the beam characteristics of pump light band modulation and probe light unmodulated are precisely realized, perfectly adapting to the core principle of iodine molecule modulation transfer spectrum frequency stabilization, which can efficiently excite stable MTS error signals; the dedicated local oscillator RF drive can ensure stable phase modulation depth and modulation frequency, and regular modulation sidebands without spurious signals, which greatly improves the signal-to-noise ratio of error signals and improves the laser frequency locking accuracy and stability from the signal source.

[0046] Furthermore, the driving circuits of the first acousto-optic modulator 6, the second acousto-optic modulator 2, and the fiber electro-optic modulator are integrated into a single driving module; the driving module has a reserved external control interface, which can configure core parameters such as modulation depth and acousto-optic driving power through external devices.

[0047] This embodiment integrates the dispersed acousto-optic driving circuit and electro-optic modulation driving circuit into a single design, abandoning the traditional discrete driving structure. The driving control functions of all modulation devices are centralized in a single module. The driving module reserves a standardized external control interface, allowing operators to configure, modify, and store core operating parameters such as modulation depth, acousto-optic driving power, and modulation frequency in real time through external industrial control equipment, debugging terminals, and other devices, achieving precise and controllable adjustment of the optical path modulation state.

[0048] The integrated design of the drive circuit greatly simplifies the system circuit structure, reduces electromagnetic interference, line loss and fault points of discrete circuits, and improves the stability and integration of the system circuit. The external adjustable interface enables flexible configuration and precise calibration of system parameters, which can be adapted to the parameter requirements of different frequency stabilization conditions and different experimental scenarios, improving the system's versatility and adjustability. At the same time, the standardized parameter configuration mode can ensure the consistency of parameters of batch equipment, which is convenient for large-scale production and engineering applications.

[0049] As a preferred embodiment, both the first frequency-doubling crystal 9 and the second frequency-doubling crystal 10 are used to perform the second harmonic conversion from the 1064nm fundamental frequency light to the 532nm frequency-doubled light, and both frequency-doubling crystals are equipped with precision temperature control circuits. The 1064nm infrared fundamental frequency light cannot be directly adapted to the frequency-stabilized spectral detection requirements of iodine molecules and needs to be converted to 532nm green light through second harmonic conversion. The first frequency-doubling crystal 9 performs the second harmonic conversion on the phase-modulated pump fundamental frequency light, outputting 532nm pump light with modulation characteristics; the second frequency-doubling crystal 10 performs the second harmonic conversion on the unmodulated probe fundamental frequency light, outputting unmodulated 532nm probe light. Simultaneously, to meet the optimal operating conditions of the frequency-doubling crystals, both crystals are independently equipped with precision temperature control circuits, ensuring that the crystals operate precisely at the phase-matching temperature point.

[0050] The frequency-doubled crystal enables precise band conversion from 1064nm to 532nm, outputting a target band laser that is compatible with the frequency stabilization of iodine molecular spectra, ensuring the effectiveness of frequency stabilization. The dual-crystal independent temperature control structure can be adapted to the frequency doubling requirements of the two optical paths respectively, avoiding phase mismatch caused by temperature deviation, effectively improving the frequency doubling conversion efficiency of the two beams, and ensuring stable output power and consistent beam quality of pump and probe beams.

[0051] Furthermore, the precision temperature control circuit adopts a closed-loop temperature control mode, which can dynamically adjust the operating temperature of the frequency doubling crystal in real time, effectively improving the frequency doubling conversion efficiency of the crystal.

[0052] The precision temperature control circuit is equipped with a temperature acquisition module and a closed-loop control module, which can acquire the operating temperature of the frequency doubling crystal in real time and compare it with the preset optimal phase matching temperature. When temperature drift occurs, the heating / cooling power is automatically and dynamically adjusted to achieve real-time temperature correction and stable locking, so that the crystal always works in the optimal frequency doubling temperature range.

[0053] The temperature closed-loop control mode can completely solve the problem of crystal temperature drift caused by ambient temperature fluctuations and device heat generation, keeping the frequency doubling crystal in the optimal phase matching state for a long time, greatly improving the frequency doubling conversion efficiency and reducing laser energy loss; at the same time, it can ensure that the frequency doubling output power does not fluctuate significantly during long-term operation, improve the stability of the two frequency doubling beams, indirectly optimize the quality of the MTS error signal, and improve the long-term stability of frequency locking.

[0054] As a preferred embodiment, the front-end light source laser frequency stabilization system of this embodiment also includes a monitoring unit. The monitoring unit leads out a 1064nm monitoring optical path through the second beam splitting unit 4. The monitoring unit has a built-in photodetector and an external wavelength meter, which can collect laser power fluctuation and wavelength change data in real time.

[0055] The low-power beam split from the second beam splitter unit 4 serves as a dedicated monitoring optical path, connected to the monitoring unit without occupying the pump or probe energy of the main optical path, thus not affecting the frequency stabilization of the main optical path. The built-in photodetector in the monitoring unit can collect dynamic fluctuation data of the laser output power in real time, while the external high-precision wavelength meter can monitor the drift change of the laser center wavelength in real time. Both types of data can be uploaded to the control system in real time, providing data support for closed-loop frequency stabilization, fault early warning, and parameter calibration.

[0056] The independent monitoring optical path design enables real-time monitoring of both laser power and wavelength, accurately capturing minute drifts and fluctuations in the light source during long-term operation. This solves the shortcomings of traditional frequency stabilization systems, such as lack of real-time monitoring and delayed fault detection. The monitoring data can support dynamic closed-loop control of the system, correcting laser output parameters in real time, further improving the stability of laser frequency and power, and ensuring long-term high-precision operation of the frequency stabilization system.

[0057] Second embodiment: Reference Figure 2The second embodiment of the present invention provides a laser frequency stabilization front-end light source device, which is applied to the laser frequency stabilization system of the front-end light source described in the first embodiment above. The device includes a fixing frame, an optical fiber disk 3, and an aluminum base plate 1. There are four optical fiber disks 3, which are respectively located at the four corners of the aluminum base plate 1. All optical fiber devices in the system are positioned and fixed by the fixing frame. The optical fiber lines 7 are neatly routed through the optical fiber disks 3. All functional devices and corresponding fixing frames are integrated and installed on the aluminum base plate 1. The devices are connected by optical fiber jumpers. All optical path nodes are treated with optical fiber fusion splicing and sealed and equipped with protective sleeves. The core functional devices are limited and fixed by clamps to form an integrated all-fiber integrated light source structure.

[0058] Specifically, the core components of the integrated device adaptation system include: an 808nm seed light source module, a 1064nm narrow-linewidth laser oscillator (NPRO) pumped by 808nm, a 1:9 polarization-maintaining fiber beam splitter for splitting the 1064nm light into a pump end and a probe end, a 1:9 polarization-maintaining fiber beam splitter for extracting one path of light for monitoring, an AOM fiber for controlling the intensity and frequency of the pump and probe light, an EOM fiber for phase modulation of the pump light, a frequency-doubled crystal that doubles the 1064nm light to 532nm, multiple fiber disks 3, a dedicated device mounting bracket, and an aluminum base plate 1.

[0059] The output of the 808nm seed light source module is spliced ​​through optical fiber into a 1064nm laser oscillator NPRO as a pump source. The NPRO operates in a single longitudinal mode with a narrow linewidth and is equipped with current and temperature control circuits to achieve center frequency tuning and stabilization. Its built-in collimation and coupling optical system is coupled into a polarization-maintaining fiber to form a 1064nm polarization-maintaining fiber output port. This output port is spliced ​​through optical fiber into a first 1:9 polarization-maintaining fiber beam splitter. The low-power output end of the beam splitter serves as the input port for the detector, and the high-power output end is then connected to a second 1:9 polarization-maintaining fiber beam splitter. The low-power output end of the latter serves as the monitoring end, and the high-power output end serves as the input port for the pump.

[0060] The pump input port is fused to the input of the first fiber AOM via optical fiber, enabling precise control and stabilization of the 532nm pump light power entering the iodine bath. The output of the first fiber AOM is fused to the input port of the fiber EOM via optical fiber. The fiber EOM is driven by a local oscillator RF to generate a phase modulation sideband on the 1064nm pump light. Only the pump light carries the modulation sideband, while the probe light remains unmodulated, meeting the basic requirements of MTS. The output of the fiber EOM is fused to the first frequency doubling crystal 9 via optical fiber, achieving a second-harmonic conversion from 1064nm to 532nm. The first fiber AOM and the fiber EOM are respectively fixed by dedicated mounting brackets.

[0061] The input port of the probe is fused to the input port of the second fiber AOM via optical fiber, and the output port of the second fiber AOM is fused to the second frequency doubling crystal 10 via optical fiber to complete the power regulation and frequency doubling conversion of the probe light. The second fiber AOM is fixed by the corresponding mounting bracket.

[0062] The device adopts an integrated design, with all optical path nodes fused and sealed and fitted with protective sleeves to prevent dust, moisture, and external force interference; the fiber optic tray 3 organizes all fiber optic lines to avoid fiber bending, tangling, and stress damage; the core components are locked by special clamps and are integrated into the aluminum base plate 1, resulting in a robust structure and excellent heat dissipation performance.

[0063] This embodiment integrates dispersed optical and electronic components into a standardized modular device, completely changing the traditional scattered construction mode of optical platforms, significantly reducing the overall size of the equipment, and achieving miniaturization, encapsulation, and portability, adapting to various precision experimental and engineering scenarios; the all-fiber sealed fusion splicing structure eliminates free-space optical path defects, greatly improving the resistance to vibration, airflow, and temperature drift, and making the system extremely robust; the standardized integration process ensures high consistency of parameters between different batches of equipment, eliminating the need for repeated manual dimming and debugging, reducing the operation threshold and maintenance costs, and facilitating mass replication and engineering promotion; the modular structure supports rapid disassembly, docking, and replacement, and can be quickly adapted and integrated with the back-end iodine spectroscopy unit, making the equipment more versatile and adaptable.

[0064] In combination with all the above embodiments, the present invention has the following core advantages compared with the prior art: This invention integrates all core components, including the seed light source, narrow-linewidth laser, fiber beam splitter, fiber AOM, fiber EOM, and frequency doubling unit, into a closed all-fiber optical path network through fiber fusion splicing. This completely eliminates free-space optical axis alignment errors, effectively resists interference from mechanical vibration, airflow disturbances, and temperature drift on the optical path, and maintains long-term stability in the power, polarization, and mode of the pump light and probe light, significantly improving the signal-to-noise ratio of the MTS error signal and the stability of laser frequency locking.

[0065] All components are uniformly fixed on the aluminum base plate 1, and with the help of a dedicated mounting bracket, fiber optic structure and protective structure, they can be packaged as a standardized front-end light source module. The size of the equipment is greatly reduced, and it supports handling, packaging and rapid integration, completely solving the drawbacks of traditional equipment being bulky and immobile.

[0066] Through dual-optical-path differentiated modulation design, precise temperature control closed-loop regulation, integrated adjustable drive parameters, and real-time optical path monitoring closed loop, the laser power, phase, band, and frequency can be precisely controlled in all aspects, ensuring laser stability throughout the entire process from the source, optical path transmission, and beam output.

[0067] The fully solidified fiber optic path eliminates the need for daily dimming and alignment, freeing it from reliance on operator experience and significantly reducing maintenance difficulty and cost. The standardized integrated process and parameter configuration system ensures consistent performance of batch products, making it suitable for large-scale production and engineering applications.

[0068] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A laser frequency stabilization front-end light source system, characterized in that, It includes a pump light source module, a narrow linewidth laser oscillator, a first beam splitting unit, a second beam splitting unit, a first acousto-optic modulator, an electro-optic modulator, a second acousto-optic modulator, a first frequency doubling crystal, and a second frequency doubling crystal; The pump light source module is connected to the optical path of the narrow linewidth laser oscillator; the narrow linewidth laser oscillator has a built-in temperature control circuit, current control circuit and collimation coupling optical component. The current control circuit and temperature control circuit are respectively electrically connected to the laser chip inside the narrow linewidth laser oscillator. The collimation coupling optical component is located on the output optical path of the laser chip, and sends the shaped and coupled laser into the polarization-maintaining fiber and transmits it to the first beam splitting unit. The first beam splitting unit splits the incident laser into a probe beam and a branch beam; the branch beam is incident on the second beam splitting unit, which splits the monitoring optical path and the pump beam, and the monitoring optical path is used to monitor the laser output status and output a feedback signal; The pump beam passes sequentially through an electro-optic modulator, a first acousto-optic modulator, and a first frequency-doubling crystal. The first acousto-optic modulator regulates the power of the pump beam, the electro-optic modulator receives an external radio frequency drive signal and performs phase modulation on the pump beam, and the first frequency-doubling crystal doubles the phase-modulated fundamental frequency pump beam to output frequency-doubled pump beam. The detection beam is sequentially transmitted to the second acousto-optic modulator and the second frequency doubling crystal. The second frequency doubling crystal doubles the frequency of the fundamental frequency detection beam and outputs a frequency doubling detection beam that has not undergone phase modulation.

2. The laser frequency stabilization front-end light source system according to claim 1, characterized in that, The pump light source module adopts an 808nm seed light source module, and the narrow linewidth laser oscillator is a 1064nm narrow linewidth laser oscillator NPRO. The output end of the 808nm seed light source module is optically connected to the 1064nm narrow linewidth laser oscillator NPRO through fiber optic fusion splicing.

3. The laser frequency stabilization front-end light source system according to claim 1, characterized in that, Both the first and second beam splitting units employ 1:9 polarization-maintaining fiber beam splitters. The high-power output end of the first beam splitter is optically connected to the input end of the second beam splitter, and the low-power output end forms the input port of the detector end. The low-power output end of the second beam splitter forms the monitoring end, and the high-power output end forms the pump input port.

4. The laser frequency stabilization front-end light source system according to claim 1, characterized in that, The first and second acousto-optic modulators are both fiber optic acousto-optic modulators, and the electro-optic modulator is a fiber optic electro-optic modulator. The pump beam is connected in series with an optical fiber electro-optic modulator, a first acousto-optic modulator, and a first frequency doubling crystal via optical fiber fusion splicing. The probe beam is connected in series with a second acousto-optic modulator and a second frequency doubling crystal via optical fiber fusion splicing, forming two independent integrated optical fiber paths.

5. The laser frequency stabilization front-end light source system according to claim 4, characterized in that, The fiber electro-optic modulator is connected to the local oscillator radio frequency drive signal to perform phase modulation on the pump beam and generate modulation sidebands, while the probe beam is free from phase modulation throughout its entire range.

6. The laser frequency stabilization front-end light source system according to claim 1, characterized in that, Both the first and second frequency doubling crystals are used to complete the second frequency conversion from 1064nm fundamental frequency light to 532nm frequency doubling light, and both frequency doubling crystals are equipped with precision temperature control circuits.

7. The laser frequency stabilization front-end light source system according to claim 6, characterized in that, The precision temperature control circuit adopts a closed-loop temperature control mode.

8. The laser frequency stabilization front-end light source system according to claim 4, characterized in that, The driving circuits of the first acousto-optic modulator, the second acousto-optic modulator, and the fiber electro-optic modulator are integrated into a single driving module. The drive module has a reserved external control interface, which can be configured with core parameters such as modulation depth and acousto-optic drive power through external devices.

9. The laser frequency stabilization front-end light source system according to claim 1, characterized in that, It also includes a monitoring unit, which leads out a 1064nm monitoring optical path through a second beam splitter. The monitoring unit has a built-in photodetector and an external wavelength meter.

10. A laser frequency stabilization front-end light source device, characterized in that, The laser frequency stabilization front-end light source system described in any one of 1-9 above includes a fixing frame, an optical fiber tray, and an aluminum base plate. All fiber optic devices in the system are positioned and fixed by a mounting bracket, and the fiber optic lines are neatly routed via fiber optic reels. All functional devices and their corresponding mounting brackets are integrated and mounted on an aluminum base plate. The components are connected by fiber optic patch cords, all optical path nodes are sealed with fiber optic fusion splicing and fitted with protective sleeves, and the core functional components are fixed by clamps to form an integrated all-fiber integrated light source structure.

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