A strontium atomic optical clock laser frequency stabilization method, device, equipment and storage medium
By combining the laser of the strontium atomic optical clock system with a femtosecond optical comb, the laser parameters can be automatically found and locked, solving the problems of large size and manual dependence of the optical clock system, achieving miniaturization and automation, and making it suitable for stable operation in complex environments.
Patent Information
- Application Number
- CN202411013662.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2024-07-26
- Publication Date
- 2025-09-09
- Estimated Expiration
- 2044-07-26
AI Technical Summary
Existing strontium atomic optical clock systems are bulky, rely on manual operation and are difficult to use in complex environments, especially in harsh environments such as the wild or space. The laser frequency stability relies on manual locking and cannot be operated automatically.
By linking 689nm, 698nm and 813nm lasers with a femtosecond optical comb, and using a multi-channel fiber switch and wavelength meter combined with PDH frequency stabilization technology, automatic search and locking of laser parameters are achieved, and an ultra-stable optical cavity system is integrated to reduce resource usage and achieve automatic frequency stabilization.
The volume and weight of the optical clock system are significantly reduced, the degree of automation is improved, human operation errors are reduced, and long-term stable operation in complex environments is ensured, making it suitable for unmanned application scenarios.
Smart Images
Figure CN118963093B_ABST
Abstract
Description
Technical Field
[0001] The present invention belongs to the technical field of atomic optical clock frequency control, and in particular relates to a strontium atomic optical clock laser frequency stabilization method, device, equipment and storage medium. Background Art
[0002] In recent years, optical clocks have made tremendous progress in terms of stability and uncertainty. Their performance has far surpassed the current benchmark clock, the cesium microwave clock, and is expected to redefine the second. In fundamental physics research, optical clocks not only excel in time measurement but also have a wide range of applications, including measuring the fine structure constant α, verifying Einstein's general theory of relativity, detecting gravitational waves, and exploring dark matter. They provide powerful tools for a deeper understanding of the fundamental laws of nature.
[0003] However, a complete optical clock system occupies a large laboratory area and consists of multiple components, including a laser system, a physical vacuum system, and an electronic control system. This complexity and cumbersome equipment has limited the widespread application of optical clocks in scientific research and engineering. To this end, many research teams at home and abroad have begun researching transportable optical clocks, striving to develop a compact, lightweight, robust, and autonomous optical clock system. The goal is to free optical clocks from the constraints of the laboratory and expand their application to a wider range of scenarios.
[0004] Among them, the large size of the laser system in the strontium optical clock system has become one of the main limiting factors. This system contains a femtosecond optical comb and six lasers with different wavelengths, namely 461nm, 679nm, 689nm, 698nm, 707nm, and 813nm. Among them, the 689nm, 698nm, and 813nm lasers are referenced to three ultra-stable optical cavity systems to narrow the laser linewidth, such as Figure 3 Figure 2 shows a schematic diagram of an ultra-stable optical cavity system used in traditional optical clock systems to narrow the linewidth of 689, 698, and 813nm lasers. Each of these three lasers requires one such system, which is very expensive and takes up a lot of space (the soundproofing box alone for each system is 1.5*1.5*1m, not including the controller, etc.). Furthermore, a dedicated vibration isolation platform, thermal insulation cover, and soundproofing cotton are also required, taking up a large amount of laboratory space.
[0005] Currently, research on transportable optical clock laser systems primarily focuses on the integration of the laser itself and the optical path, while reports on improvements to ultra-stable optical cavity systems are relatively limited. Previous attempts at transportable optical clocks typically involved transporting a scaled-down optical clock to its destination, then placing the ultra-stable optical cavity system in a nearby laboratory for debugging. While this approach allowed optical clocks to move beyond the laboratory, it still faced numerous limitations, particularly in harsh environments such as the field or space.
[0006] In addition, it is essential for optical clocks to operate automatically outside the laboratory. So far, all known transportable optical clocks rely on manual operation, which limits their operating scenarios, such as high-altitude environments, space stations, etc. Automated operation includes laser frequency stabilization automation and closed-loop operation automation. Closed-loop operation automation is relatively mature, while laser frequency stabilization still relies on manual operation. The six lasers in the optical clock system must operate at a specific target wavelength. Traditional methods require manual search and locking of the working wavelength one by one before experiments can be conducted. In the future, if optical clocks enter space for operation, manual intervention will become difficult. Therefore, it is crucial to realize a laser frequency stabilization system that automatically searches for and locks the working wavelength. Summary of the Invention
[0007] In order to solve the problem of how to automatically find the working wavelength and reduce resource usage, the present invention provides a strontium atomic optical clock laser frequency stabilization method, device, equipment and storage medium. To solve this problem, the present invention uses a femtosecond optical comb to connect 689nm, 698nm and 813nm lasers, reducing three ultra-stable optical cavity systems to one, greatly reducing the volume and weight of the optical clock system, and creating the possibility of conducting experiments in more complex environments. At the same time, it overcomes the problems of manual dependence, frequency drift and large size in the existing technology. Through an innovative laser frequency stabilization solution, the present invention aims to improve the automation and stability of the strontium atomic optical clock system and significantly reduce its resource usage.
[0008] In order to achieve the above object, the present invention provides the following technical solutions:
[0009] A method for laser frequency stabilization of a strontium atomic optical clock comprises the following steps:
[0010] Lasers emitted by multiple lasers of different wavelengths in a strontium atomic optical clock system are input into a wavelength meter through a multi-channel fiber optic switch. Parameter ranges for all lasers are set, parameter changes for each laser are controlled, and all parameter combinations are traversed. The lasers of different wavelengths are a 689nm laser, a 698nm laser, and an 813nm laser. The parameters of each laser include current, temperature, and voltage. The traversal of each parameter combination involves arbitrarily combining the three parameters within the preset parameter range of the laser, and observing the wavelength data output by the wavelength meter based on the combination results.
[0011] Multiple parameter combinations corresponding to the target wavelength are found based on the wavelength data recorded by the wavelength meter during the parameter combination traversal process; the parameters of each laser are adjusted to be consistent with the multiple parameter combinations found; the piezoelectric ceramic inside the laser is then scanned, and based on the wavelength data synchronously recorded by the wavelength meter, the combination with the largest frequency tuning range among the multiple parameter combinations found is found as the optimal parameter for each laser; the frequency tuning range refers to the range within which the laser frequency can be continuously varied;
[0012] Based on the optimal parameters, the PDH frequency stabilization technology is used to lock the 698nm laser to a unique ultra-stable optical cavity, then the femtosecond optical comb is locked to the 698nm laser, and finally the 689nm and 813nm lasers are locked to the femtosecond optical comb.
[0013] Preferably, the method of using PDH frequency stabilization technology to lock the 698nm laser to a single ultra-stable optical cavity, then locking the femtosecond optical comb to the 698nm laser, and finally locking the 689nm and 813nm lasers to the femtosecond optical comb specifically includes:
[0014] A wavelength meter was used to find the target wavelengths of the 689nm laser, 813nm laser, and 698nm laser, and the 698nm laser was locked to an ultra-stable optical cavity to achieve linewidth narrowing of the 698nm laser.
[0015] Locking the femtosecond optical comb to the hydrogen clock;
[0016] The frequency of the 698nm laser is measured using a femtosecond optical comb. If the frequency does not match the preset target frequency, the frequency of the acousto-optic modulator (AOM) is adjusted until the 698nm laser frequency matches the target frequency.
[0017] The femtosecond optical comb was unlocked from the hydrogen clock and locked to a 698nm laser, with a fixed repetition frequency and carrier-envelope phase shift each time the comb was locked.
[0018] The beat signal of the 689nm laser and 813nm laser with the femtosecond optical comb is fed back to the 689nm laser and 813nm laser to control the opening of the integration switch. The analog circuit completes the final laser frequency locking to achieve linewidth narrowing.
[0019] During the closed-loop operation of the optical clock, the strontium atomic spectrum is used as the frequency reference, and the frequency drift introduced by the ultra-stable optical cavity is compensated in real time by the AOM.
[0020] Preferably, the lasers of different wavelengths further include a 461 nm laser, a 679 nm laser, and a 707 nm laser. After finding the optimal parameters of the 461 nm laser, the 679 nm laser, and the 707 nm laser, the following steps are further included:
[0021] The wavelength of the 679nm laser is monitored in real time by a wavelength meter. If the wavelength drifts out of the set working range, the piezoelectric ceramic is adjusted to keep the wavelength within the set wavelength range.
[0022] For a 707nm laser, the laser is controlled to sweep around its target center wavelength of 707.202nm, with a sweep range of 4GHz;
[0023] For the 461nm laser, turn on the integration switch of the analog circuit and reference it to the strontium atom through the saturation absorption spectrum stabilization technology. 1 S0→ 1 P1 transition.
[0024] Preferably, when traversing each parameter combination, the wavelength meter records wavelength data every 500 milliseconds.
[0025] Another object of the present invention is to provide a strontium atomic optical clock laser frequency stabilization device, comprising:
[0026] A traversal module is used to input the lasers emitted by multiple lasers of different wavelengths in the strontium atomic optical clock system into the wavelength meter through a multi-channel fiber optic switch, set the parameter range of all lasers, control the parameter changes of each laser, and traverse all parameter combinations. The lasers of different wavelengths are 689nm lasers, 698nm lasers, and 813nm lasers. The parameters of each laser include current, temperature, and voltage. The traversal of each parameter combination involves arbitrarily combining the three parameters within the preset parameter range of the laser and observing the wavelength data output by the wavelength meter based on the combination results.
[0027] The parameter optimization module is used to find multiple parameter combinations that correspond to the target wavelength based on the wavelength data recorded by the wavelength meter during the parameter combination process; adjust the parameters of each laser to match the target wavelength; then scan the piezoelectric ceramic inside the laser and, based on the wavelength data synchronously recorded by the wavelength meter, find the combination with the largest frequency tuning range among all parameter combinations, which is used as the optimal parameter for each laser. The frequency tuning range refers to the range within which the laser frequency can be continuously varied;
[0028] The laser locking module is used to lock the 698nm laser to a single ultra-stable optical cavity based on optimal parameters using PDH frequency stabilization technology. It then locks the femtosecond optical comb to the 698nm laser, and finally locks the 689nm and 813nm lasers to the femtosecond optical comb.
[0029] The present invention also provides a computer device, comprising a memory, a processor, and a computer program stored in the memory, wherein the processor executes the computer program to implement any one of the steps in the strontium atomic optical clock laser frequency stabilization method.
[0030] The present invention also provides a computer-readable storage medium, on which a computer program is stored. The computer program is characterized in that when loaded by a processor, the computer program can execute any one of the steps in the strontium atomic optical clock laser frequency stabilization method.
[0031] The strontium atomic optical clock laser frequency stabilization method provided by the present invention has the following beneficial effects:
[0032] The present invention combines and traverses multiple parameters of the laser, and is used to find multiple parameter combinations corresponding to the target wavelength according to the wavelength data recorded during the parameter combination traversal process, and further searches for the parameter combination with the largest frequency tuning range by scanning the piezoelectric ceramics as the optimal parameters of each laser, thereby realizing automatic target wavelength search and locking of all lasers in the strontium optical clock system, greatly improving the efficiency of frequency search, while reducing the possibility of human operation error, and ensuring that the system reaches a stable state in a shorter time. Finally, according to the optimal parameters, the PDH frequency stabilization technology is used to lock the 698nm laser to a single ultra-stable optical cavity, and then the femtosecond optical comb is locked to the 698nm laser, and finally the 689nm and 813nm lasers are locked to the femtosecond optical comb. By introducing the femtosecond optical comb technology, the ultra-stable optical cavity system is integrated, significantly simplifying the structure of the traditional strontium optical clock system, replacing the original three sets of ultra-stable optical cavity systems, not only reducing the cost, complexity and resource requirements of the system, but also improving the stability of the system, making it more suitable for complex actual working environments. BRIEF DESCRIPTION OF THE DRAWINGS
[0033] To more clearly illustrate the embodiments of the present invention and its design, the following briefly introduces the drawings required for this embodiment. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be derived from these drawings without inventive effort.
[0034] Figure 1 Schematic diagram of a solution for automatically searching for a target wavelength for a laser in the strontium atomic optical clock laser frequency stabilization method according to Example 1 of the present invention.
[0035] Figure 2 Schematic diagram of automatic frequency stabilization of 689nm laser and 813nm laser.
[0036] Figure 3 Schematic diagram of the optical path of the ultra-stable optical cavity in a traditional optical clock system. DETAILED DESCRIPTION
[0037] In order to enable those skilled in the art to better understand the technical solution of the present invention and to be able to implement it, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments. The following embodiments are only used to more clearly illustrate the technical solution of the present invention and are not intended to limit the scope of protection of the present invention.
[0038] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "axial", "radial", "circumferential" and the like to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the technical solutions of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.
[0039] In addition, the terms "first", "second", etc. are used for descriptive purposes only and are not to be understood as indicating or implying relative importance. In the description of the present invention, it should be noted that, unless otherwise expressly specified or limited, the terms "connected" and "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meaning of the above terms in the present invention can be understood according to the specific circumstances. In the description of the present invention, unless otherwise specified, "plurality" means two or more, which will not be described in detail here.
[0040] First, the term optical clock involved in the present invention is explained:
[0041] An optical clock is an atomic clock that uses optical frequencies as a reference. It consists of three main components: an oscillator that generates a stable periodic signal, known as a frequency-stabilized laser (equivalent to the local oscillator of an atomic frequency standard); a frequency detector (equivalent to the atomic transition lines of an atomic frequency standard) used to lock the frequency-stabilized laser; and a frequency divider (equivalent to the atomic frequency standard's atomic transition lines) that links the optical and atomic frequencies. This allows the optical clock to be linked to a microwave clock, enabling convenient frequency comparisons and corrections to the atomic clock.
[0042] The purpose of this invention is to provide an innovative method for strontium atomic optical clock laser frequency stabilization. This method can automatically search and lock all laser frequencies in the optical clock system while significantly reducing resource usage (including volume, mass, and power consumption).
[0043] The laser system of the strontium atomic optical clock includes a femtosecond optical comb and six lasers with different wavelengths, namely 461nm, 679nm, 689nm, 698nm, 707nm and 813nm. During the operation of the optical clock, all lasers need to operate within a specific wavelength range, but the requirements for frequency accuracy vary. For example, the frequency accuracy requirements of the 707nm laser are almost negligible, and only the frequency scan around 707.202nm is required. The frequency accuracy requirements of the 679nm laser are relatively low, and its normal operating frequency range can reach more than 300MHz. The operating frequency of the 461nm laser is required to be accurate to the MHz level, and the 689nm and 813nm lasers have higher requirements, requiring the operating frequency to be accurate to the kHz level. The 698nm laser with the highest requirements needs to achieve Hz level accuracy.
[0044] Specifically, the implementation of the strontium atomic optical clock laser frequency stabilization method provided by the present invention includes the following steps:
[0045] Step 1: The lasers emitted by multiple lasers of different wavelengths in the strontium atomic optical clock system are respectively input into a wavelength meter through a multi-channel optical fiber switch, the parameter range of all lasers is set, the parameter changes of the lasers are controlled by software, all parameter combinations are traversed, and each parameter combination is traversed; the lasers of different wavelengths are respectively 689nm lasers, 698nm lasers and 813nm lasers, and the parameters of each laser include current, temperature and voltage. The parameters of each parameter combination are traversed to be within the parameter range of the laser, and the three parameters are arbitrarily combined, and the wavelength data output by the wavelength meter is observed according to the combination result; in the present invention, multiple lasers are simultaneously input into the optical fiber switch, and the switch inputs these lasers into the wavelength meter separately by switching channels, with a very fast switching speed of about 12 milliseconds. The present invention changes the parameters of the lasers through software control to achieve the purpose of traversing all laser parameters; the wavelength meter is used to record wavelength data.
[0046] Step 2: Find multiple parameter combinations that match the target wavelength based on the wavelength data recorded by the wavelength meter during the parameter combination traversal process. When traversing each parameter combination, the wavelength meter records the wavelength data every 500 milliseconds. Adjust the parameters of each laser to match the multiple parameter combinations found. Then, scan the piezoelectric ceramic inside the laser and, based on the wavelength data synchronously recorded by the wavelength meter, find the combination with the largest frequency tuning range among the multiple parameter combinations found, which serves as the optimal parameter for each laser. The frequency tuning range refers to the range within which the laser frequency can continuously change; beyond this range, the laser will mode hop. Because more than one parameter combination can achieve the target wavelength, multiple parameter combinations may be able to achieve the target wavelength. All lasers need to find a suitable parameter combination. The present invention can operate all lasers simultaneously, improving the search efficiency and finding the optimal parameter combination for each laser in the shortest possible time.
[0047] Step 3: Based on the optimal parameters, PDH frequency stabilization technology is used to lock the 698nm laser to a single ultra-stable optical cavity. The femtosecond optical comb is then locked to the 698nm laser, and finally the 689nm and 813nm lasers are locked to the femtosecond optical comb.
[0048] Example 1
[0049] The following is a detailed example of the strontium atomic optical clock laser frequency stabilization method provided by the present invention. This method involves two steps. First, each laser automatically searches for its target center wavelength without human intervention. Second, based on the varying frequency accuracy requirements of each laser, different frequency standards are referenced to ensure the system achieves the required accuracy level.
[0050] Figure 1A schematic diagram shows how all lasers in the strontium atomic optical clock system automatically search for their target central wavelength. This automatic search is accomplished using a wavelength meter, a multi-channel fiber optic switch, and a microcomputer. All lasers are fed into the wavelength meter via the multi-channel fiber optic switch. Control software within the computer presets the target wavelengths and parameter ranges for all lasers (parameters include temperature, current, and voltage, for example, a current range of 55mA-65mA, a temperature range of 20°C-22°C, and a voltage range of 50V-60V). The software controls the loop through various parameter combinations (a parameter combination is any combination of the three parameters within their set ranges. For example, 56mA, 21°C, and 55V is one parameter combination, and 57mA, 22°C, and 55V is another). Setting all possible parameter combinations through the software and observing the wavelength meter data is called looping through all parameter combinations. The wavelength meter records wavelength data every 500 milliseconds. After looping through the recorded wavelength data, the software finds multiple parameter combinations that correspond to the target wavelength. Subsequently, the parameters of each laser are set to the above-mentioned matching parameter combination in turn through software control, and the piezoelectric ceramics inside the laser are scanned to find the parameter combination with the largest frequency tuning range as the optimal parameters of the laser.
[0051] After completing the automatic search for the target frequency, the control software develops a different frequency stabilization scheme based on the characteristics of each laser. For the 707nm laser, the software controls the laser to sweep around its target center wavelength of 707.202nm, with a sweep range of 4GHz. Since the wavelength meter's accuracy meets the operating requirements of the 679nm laser, the 679nm laser is directly referenced to the wavelength meter. Specifically, the 679nm laser is in a free-running state, but its operating wavelength range is set in the software. The wavelength of the 679nm laser is monitored in real time using the wavelength meter. If the wavelength drifts outside the set operating range, the control software will provide feedback to the laser's piezoelectric ceramic, fine-tuning the wavelength to ensure dynamic stability within the operating wavelength range (i.e., by adjusting the piezoelectric ceramic to ensure that the wavelength always operates within the set wavelength range). Piezoelectric ceramics are ceramics with piezoelectric properties. Depending on the voltage applied to them, the length of the piezoelectric ceramic will vary. Therefore, adjusting the piezoelectric ceramic actually changes the voltage applied to the piezoelectric ceramic (that is, the voltage among the three laser parameters), thereby changing the length of the piezoelectric ceramic.
[0052] For 461nm, 689nm, 698nm and 813nm, they have high frequency accuracy requirements, while the accuracy of the wavelength meter is usually in the range of 10MHz to 100MHz, which cannot meet the requirements. Among them, the reference source of the 461nm laser is consistent with the traditional optical clock, both of which are strontium atomic spectrum. The integration switch of the analog circuit is turned on by software control, and it is referenced to the strontium atomic spectrum through the saturation absorption spectrum stabilization technology.1 S0→ 1 P1 transition.
[0053] In traditional optical clock systems, 689nm, 698nm, and 813nm are referenced to three ultra-stable optical cavities respectively to achieve linewidth narrowing of the laser frequency. However, ultra-stable optical cavities occupy a huge amount of volume and weight. To ensure that optical clocks can operate in complex outdoor environments or space stations, more robust structural designs and vibration isolation platforms must be used to shield mechanical vibrations in the environment, and more thermal insulation materials must be used to isolate external temperature fluctuations. This makes the space and weight resources occupied by the three sets of ultra-stable optical cavity systems far exceed the carrying capacity of a mobile optical clock or space optical clock. In addition, solving the cavity length drift problem of ultra-stable optical cavities is also a huge challenge faced by optical clocks working outside the laboratory.
[0054] To address these issues, the present invention leverages the wide spectral coverage of a femtosecond optical comb to link 689nm, 698nm, and 813nm lasers via the femtosecond comb. This allows a strontium optical clock system to require only one ultrastable optical cavity, while also addressing the frequency drift issue of the cavity. As a clock laser, the 698nm laser has the most stringent linewidth requirements. Therefore, the present invention utilizes PDH frequency stabilization technology to lock the 698nm laser to a single ultrastable optical cavity, achieving a laser linewidth in the Hz range. The 689nm and 813nm lasers are then locked to the femtosecond comb.
[0055] Figure 2 The schematic diagram of the automatic frequency stabilization scheme for 689nm laser and 813nm laser is shown. Through the femtosecond optical comb, the 689(813)nm laser is connected with the 698nm clock laser, solving the linewidth and frequency drift problems. The specific operation is as follows:
[0056] 1. Use a wavelength meter to find the target wavelengths of the 689(813)nm and 698nm lasers, and lock the 698nm laser to an ultra-stable optical cavity to achieve linewidth narrowing of the 698nm laser.
[0057] 2. Lock the femtosecond optical comb to the hydrogen clock.
[0058] 3. Use a femtosecond optical comb to precisely measure the frequency of the 698nm laser (accurate to hundreds of Hz). If the frequency does not match the target frequency value preset in the control software (caused by drift of the ultrastable optical cavity), the frequency of the acousto-optic modulator (AOM) is adjusted through software control until the 698nm laser frequency matches the target frequency.
[0059] 4. The femtosecond optical comb is unlocked from the hydrogen clock and locked to the 698nm laser. Each time the femtosecond optical comb is locked, a fixed repetition frequency and carrier-envelope phase shift are used.
[0060] 5. Feed the beat signal of the 689(813)nm laser and the femtosecond optical comb back to the 689(813)nm laser, turn on the integration switch through software control, and complete the final laser frequency locking by the analog circuit to achieve linewidth narrowing.
[0061] 6. Closed-loop operation of the strontium optical clock: During the closed-loop operation of the optical clock, the strontium atomic spectrum is used as the frequency reference. The frequency drift introduced by the ultra-stable optical cavity is compensated in real time by the AOM, which solves the frequency drift problem and ensures the long-term stable operation of the strontium optical clock.
[0062] This solution not only saves the space and weight of two ultra-stable optical cavities but also avoids manual adjustment of the AOM frequency. It is particularly suitable for resource-constrained, unmanned field or space station experiments. The successful implementation of this technical solution is not only of great significance for the advancement of optical clock technology, but also provides a useful reference for automatic frequency control of other high-precision measuring instruments. This invention can promote the development of optical clock technology, improve its automation and resource efficiency, and lay the foundation for the widespread use of strontium atomic optical clocks in practical applications.
[0063] Based on the same inventive concept, the present invention also provides a strontium atomic optical clock laser frequency stabilization device, including a traversal module, a parameter optimization module and a laser locking module.
[0064] Specifically, the traversal module is used to input the lasers emitted by multiple lasers of different wavelengths into the wavelength meter through a multi-channel optical fiber switch, set the parameter range of all lasers, control the parameter changes of each laser, and traverse all parameter combinations; the lasers with different wavelengths are 461nm laser, 679nm laser, 689nm laser, 698nm laser, 707nm laser and 813nm laser, and the parameters of each laser include current, temperature and voltage. The traversal of each parameter combination is to arbitrarily combine the three parameters within the preset parameter range of the laser, and observe the wavelength data output by the wavelength meter according to the combination result.
[0065] The parameter optimization module is used to find multiple parameter combinations that correspond to the target wavelength based on the wavelength data recorded by the wavelength meter during the traversal of parameter combinations; adjust the parameters of each laser to match the target wavelength; then scan the piezoelectric ceramics inside the laser and, based on the wavelength data synchronously recorded by the wavelength meter, find the combination with the largest frequency tuning range among all parameter combinations as the optimal parameters for each laser; the frequency tuning range refers to the range within which the laser frequency can be continuously changed.
[0066] The laser locking module is used to lock the 698nm laser to a single ultra-stable optical cavity based on the optimal parameters using PDH frequency stabilization technology. It then locks the femtosecond optical comb to the 698nm laser, and finally locks the 689nm and 813nm lasers to the femtosecond optical comb.
[0067] The wavelength of the 679nm laser is monitored in real time by a wavelength meter. If the wavelength drifts out of the set working range, the piezoelectric ceramic is adjusted to keep the wavelength within the set wavelength range.
[0068] For a 707nm laser, the laser is controlled to sweep around its target center wavelength of 707.202nm, with a sweep range of 4GHz;
[0069] For the 461nm laser, turn on the integration switch of the analog circuit and reference it to the strontium atom through the saturation absorption spectrum stabilization technology. 1 S0→ 1 P1 transition.
[0070] Each module in the aforementioned strontium atomic optical clock laser frequency stabilization device can be implemented in whole or in part through software, hardware, or a combination thereof. Each module can be embedded in or independent of a processor within a computer device in hardware form, or stored in a computer device's memory as software, allowing the processor to call and execute the corresponding operations of each module.
[0071] The present invention also provides a computer device comprising a memory, a processor, and a computer program stored in the memory. The processor executes the computer program to implement the steps in the embodiment of the method for strontium atomic optical clock laser frequency stabilization. The specific implementation method can be found in the method embodiment and will not be repeated here.
[0072] Furthermore, the present invention also provides a non-temporary computer-readable storage medium containing instructions, on which a computer program is stored. For example, a memory containing instructions, the instructions can be executed by a processor of a computer device to complete the above method. For example, the non-temporary computer-readable storage medium can be a ROM, a random access memory (RAM), a CD-ROM, a magnetic tape, a floppy disk, and an optical data storage device. When the computer program is executed by the processor, it can implement the steps in the embodiment of the strontium atomic optical clock laser frequency stabilization method. The specific implementation method can be found in the method embodiment, which will not be repeated here.
[0073] The strontium atomic optical clock laser frequency stabilization method provided by the present invention achieves the following objectives:
[0074] (1) Implementation of automatic wavelength adjustment. The wavelength of each laser is monitored in real time by a wavelength meter, and the monitoring result is compared with the preset target wavelength. The comparison result is fed back as an error signal to the laser's current, piezoelectric, and temperature control to ensure that each laser can automatically find the target operating wavelength.
[0075] (2) Design of a small and lightweight laser frequency stabilization system. By utilizing the extremely wide spectral range of the femtosecond optical comb, the 689nm and 813nm lasers in the strontium atomic optical clock system are linked to the 698nm laser, omitting two sets of ultra-stable optical cavities and their supporting structures and vacuum devices specifically used to compress the 689 (813)nm laser linewidth, thereby significantly reducing the mass, volume and power consumption of the strontium atomic optical clock laser system. By introducing femtosecond optical comb technology, the present invention integrates the ultra-stable optical cavity system, significantly simplifies the structure of the traditional strontium optical clock system, and replaces the original three sets of ultra-stable optical cavity systems. This integration solution not only reduces the cost, complexity and resource requirements of the system, but also improves the stability of the system, making it more suitable for complex actual working environments.
[0076] (3) Solved the cavity length drift problem of the ultra-stable optical cavity. By combining the hydrogen clock and the femtosecond optical comb, the 698nm clock laser is accurately measured and shifted, which can effectively solve the problem of the cavity length drift of the ultra-stable optical cavity that needs to be manually compensated before each startup. In the traditional strontium optical clock system, due to the drift of the ultra-stable optical cavity, the frequency of the three ultra-stable optical cavities needs to be manually adjusted every time the system is started. In the present invention, the AOM frequency no longer needs to be manually adjusted, and the strontium optical clock can be operated in an unmanned environment, marking an important step for the strontium optical clock system towards engineering and commercialization.
[0077] (4) Solved the long-term operation problem of the strontium optical clock. Through the strontium optical clock closed-loop program, the cavity length drift of the ultra-stable optical cavity during the operation of the optical clock is compensated in real time. At the same time, the frequency drift problem of 689nm, 813nm and 698nm lasers is solved, ensuring the long-term stable operation of the optical clock in an environment without human interference.
[0078] (5) This invention enables automatic target wavelength search and locking for all lasers within the strontium optical clock system. This compares favorably to conventional strontium optical clock systems, which typically rely on manual wavelength search and locking. This automated strategy significantly improves the efficiency of frequency search while reducing the potential for human error, ensuring that the system reaches a stable state in a shorter time.
[0079] (6) Through real-time monitoring and feedback from the wavelength meter, the present invention can achieve rapid and automatic relocking of the laser after it loses lock. Compared with the manual relocking method in traditional strontium optical clock systems, this innovation significantly improves efficiency. Compared with traditional optical clocks, the present invention saves a lot of resources and lays a solid foundation for the engineering application of optical clocks.
[0080] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.
[0081] The present invention is described with reference to flowcharts and / or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.
[0082] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.
[0083] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 The steps for the function specified in one or more boxes.
[0084] It should be pointed out that the specific implementation methods described above can enable those skilled in the art to understand the invention more comprehensively, but do not limit the invention in any way. Therefore, although the present specification and examples have described the invention in detail, those skilled in the art should understand that the invention can still be modified or replaced by equivalents; and all technical solutions and improvements that do not deviate from the spirit and scope of the invention are included in the scope of protection of the patent for the invention. Any figure mark in the claims should not be regarded as limiting the claims involved. Any simple change or equivalent replacement of the technical solution that can be obviously obtained by any person familiar with the art within the technical scope disclosed in the present invention falls within the scope of protection of the present invention.
Claims
1. A method for laser frequency stabilization of a strontium atomic optical clock, characterized in that: The following steps are involved: Lasers emitted by multiple lasers of different wavelengths in a strontium atomic optical clock system are input into a wavelength meter through a multi-channel fiber optic switch. Parameter ranges for all lasers are set, parameter changes for each laser are controlled, and all parameter combinations are traversed. The lasers of different wavelengths are a 689nm laser, a 698nm laser, and an 813nm laser. The parameters of each laser include current, temperature, and voltage. The traversal of each parameter combination involves arbitrarily combining the three parameters within the preset parameter range of the laser, and observing the wavelength data output by the wavelength meter based on the combination results. Multiple parameter combinations corresponding to the target wavelength are found based on the wavelength data recorded by the wavelength meter during the parameter combination traversal process; the parameters of each laser are adjusted to be consistent with the multiple parameter combinations found; the piezoelectric ceramic inside the laser is then scanned, and based on the wavelength data synchronously recorded by the wavelength meter, the combination with the largest frequency tuning range among the multiple parameter combinations found is found as the optimal parameter for each laser; the frequency tuning range refers to the range within which the laser frequency can be continuously varied; Based on the optimal parameters, the PDH frequency stabilization technology is used to lock the 698nm laser to a unique ultra-stable optical cavity, then the femtosecond optical comb is locked to the 698nm laser, and finally the 689nm and 813nm lasers are locked to the femtosecond optical comb.
2. The strontium atomic optical clock laser frequency stabilization method according to claim 1, characterized in that: The PDH frequency stabilization technology is used to lock the 698nm laser to a single ultra-stable optical cavity, then lock the femtosecond optical comb to the 698nm laser, and finally lock the 689nm and 813nm lasers to the femtosecond optical comb. Specifically, the process includes: A wavelength meter was used to find the target wavelengths of the 689nm laser, 813nm laser, and 698nm laser, and the 698nm laser was locked to an ultra-stable optical cavity to achieve linewidth narrowing of the 698nm laser. Locking the femtosecond optical comb to the hydrogen clock; The frequency of the 698nm laser is measured using a femtosecond optical comb. If the frequency does not match the preset target frequency, the frequency of the acousto-optic modulator (AOM) is adjusted until the 698nm laser frequency matches the target frequency. The femtosecond optical comb was unlocked from the hydrogen clock and locked to a 698nm laser, with a fixed repetition frequency and carrier-envelope phase shift each time the comb was locked. The beat signal of the 689nm laser and 813nm laser with the femtosecond optical comb is fed back to the 689nm laser and 813nm laser to control the opening of the integration switch. The analog circuit completes the final laser frequency locking to achieve linewidth narrowing. During the closed-loop operation of the optical clock, the strontium atomic spectrum is used as the frequency reference, and the frequency drift introduced by the ultra-stable optical cavity is compensated in real time by the AOM.
3. The strontium atomic optical clock laser frequency stabilization method according to claim 1, characterized in that: Lasers with different wavelengths also include 461nm lasers, 679nm lasers, and 707nm lasers. After finding the optimal parameters of 461nm lasers, 679nm lasers, and 707nm lasers, the following are also included: The wavelength of the 679nm laser is monitored in real time by a wavelength meter. If the wavelength drifts out of the set working range, the piezoelectric ceramic is adjusted to keep the wavelength within the set wavelength range. For a 707nm laser, the laser is controlled to sweep around its target center wavelength of 707.202nm, with a sweep range of 4GHz; For the 461nm laser, turn on the integration switch of the analog circuit and reference it to the strontium atom through the saturation absorption spectrum stabilization technology. 1 S0→ 1 P1 transition.
4. The strontium atomic optical clock laser frequency stabilization method according to claim 1, characterized in that: When traversing each parameter combination, the wavelength meter records wavelength data every 500 milliseconds.
5. A strontium atomic optical clock laser frequency stabilization device, characterized in that: include: A traversal module is used to input the lasers emitted by multiple lasers of different wavelengths in the strontium atomic optical clock system into the wavelength meter through a multi-channel fiber optic switch, set the parameter range of all lasers, control the parameter changes of each laser, and traverse all parameter combinations. The lasers of different wavelengths are 689nm lasers, 698nm lasers, and 813nm lasers. The parameters of each laser include current, temperature, and voltage. The traversal of each parameter combination involves arbitrarily combining the three parameters within the preset parameter range of the laser and observing the wavelength data output by the wavelength meter based on the combination results. The parameter optimization module is used to find multiple parameter combinations that correspond to the target wavelength based on the wavelength data recorded by the wavelength meter during the parameter combination traversal process; adjust the parameters of each laser to be consistent with the multiple parameter combinations found; then scan the piezoelectric ceramic inside the laser and, based on the wavelength data synchronously recorded by the wavelength meter, find the combination with the largest frequency tuning range among the multiple parameter combinations found, which is used as the optimal parameter for each laser; the frequency tuning range refers to the range within which the laser frequency can be continuously changed; The laser locking module is used to lock the 698nm laser to a single ultra-stable optical cavity based on optimal parameters using PDH frequency stabilization technology. It then locks the femtosecond optical comb to the 698nm laser, and finally locks the 689nm and 813nm lasers to the femtosecond optical comb.
6. A computer device comprising a memory, a processor, and a computer program stored in the memory, wherein: The processor executes the computer program to implement the steps of the strontium atomic optical clock laser frequency stabilization method according to any one of claims 1 to 4.
7. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is loaded into a processor, it is capable of executing the steps of the strontium atomic optical clock laser stabilization method described in any one of claims 1 to 4.