A cold atom frequency stabilized laser and a method for implementing the same
By using the integrated demodulation technology of cold atom recoil resonance spectral lines, the problems of thermal noise and Doppler broadening in traditional laser frequency stabilization technology have been solved, achieving active stabilization of high-stability laser frequency, simplifying the system structure and improving frequency stability.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- XIDIAN UNIV
- Filing Date
- 2025-12-31
- Publication Date
- 2026-07-07
AI Technical Summary
Existing high-performance laser frequency stabilization technologies are limited by the thermal noise and mechanical vibration of optical resonators, as well as Doppler broadening and collision broadening based on atomic/molecular gas cells, resulting in insufficient frequency stability and accuracy, and complex and costly systems.
By using the cold atom recoil resonance spectral line as a frequency reference and employing second harmonic demodulation technology, the error signal is directly extracted from the transmitted light intensity signal, and a simple feedback control loop is constructed to achieve active stabilization of the laser frequency.
It improves the short-term stability and long-term reliability of laser frequency, simplifies the system structure, reduces sensitivity to environmental disturbances, overcomes the limitations of traditional methods, and provides a new technological path with compact structure and superior performance.
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Figure CN121840352B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of laser technology, and particularly relates to a cold atom frequency-stabilized laser and its implementation method. Background Technology
[0002] In contemporary basic scientific research and cutting-edge technology fields, highly stable lasers have evolved into an indispensable core tool. Their core value stems from the extremely high precision potential inherent in optical frequency itself. As one of the most stable fundamental constants in nature, the frequency of light provides the physical basis for achieving the most precise measurements to date. The stability of laser frequency directly determines the accuracy and upper limit of precision in related fundamental physical processes such as energy measurement, time measurement, and spatial interference. Specifically, in cold atom physics experiments, the stable frequency of the laser determines the resonance conditions for atomic energy level transitions, which is the basis for laser cooling, trapping, and manipulating neutral atoms or ions. Frequency fluctuations will lead to decreased cooling efficiency, drift of the trapping potential well position, and even loss of quantum state coherence. In the field of quantum precision measurement, such as in atomic interferometers and optical lattice clocks, the laser acts as a "probe" for probing and manipulating the internal state of atoms. Its frequency noise directly translates into measurement errors of inertial forces or output noise of time and frequency, limiting these advanced instruments from reaching their theoretical sensitivity limits. In quantum information processing, the frequency stability and coherence length of lasers used to manipulate qubits are directly related to the fidelity of quantum logic gates and the storage time of quantum states. Therefore, developing laser sources capable of generating and maintaining extremely high frequency stability is not only a technological pursuit in the field of optics, but also a key foundation for pushing related disciplines such as atomic and molecular physics, quantum optics, metrology, and even gravitational wave detection to break through existing precision boundaries and explore new physical phenomena.
[0003] Current mainstream high-performance laser frequency stabilization technologies mainly follow two technical paths, both of which have inherent physical or technical limitations. The first path relies on a high-precision optical resonant cavity as a frequency reference. Such systems achieve stabilization by locking the laser frequency to a resonant mode of a Fabry-Perot cavity made of a material with an ultra-low coefficient of thermal expansion. However, its performance is fundamentally limited by the thermodynamic fluctuations (thermal noise) of the cavity length itself and the mechanical vibration noise caused by Brownian motion. Even when the cavity is placed in a multilayer active temperature control and precision vibration isolation device, the intrinsic thermal fluctuations of the dielectric thin film constituting the cavity mirror and its substrate material are still an inescapable physical limit, restricting further improvements in frequency stability. In addition, such systems are usually complex in structure, large in size, extremely expensive, and exceptionally sensitive to changes in ambient temperature and mechanical vibration. The second path utilizes specific transition spectral lines of atomic or molecular vapor chambers as an absolute frequency reference. Common techniques include saturated absorption spectroscopy, modulation transfer spectroscopy, and frequency modulation spectroscopy. Although these methods provide frequency anchors directly related to intrinsic atomic transitions, their performance is limited by the thermal motion of hot atoms (or molecules) in the vapor chamber. The high-speed thermal motion of atoms at room temperature leads to severe Doppler broadening, making the spectral linewidth much larger than the natural linewidth, which greatly reduces the potential sensitivity and accuracy of frequency discrimination. At the same time, collisions between atoms in the vapor chamber introduce collision broadening and frequency shift. These effects are closely related to gas pressure and temperature, and become an important source of long-term frequency drift.
[0004] Given the limitations of traditional methods, using ultracold atoms obtained through laser cooling technology as a frequency reference source demonstrates immense potential and significant advantages. The core advantages of cold atom systems lie in their extremely low velocity (temperatures reaching the micro-Kelvin or even nano-Kelvin levels) and highly isolated experimental environment (ultra-high vacuum). The extremely low temperature means that the thermal velocity of atoms is minimal, suppressing the Doppler effect to a negligible level. This allows the observed atomic spectral linewidths to approach their natural linewidths, which are more than three orders of magnitude narrower than the transmission lines of room-temperature atomic gas chambers, providing an intrinsic and extremely sharp "yardstick" for frequency locking. Secondly, cold atoms exist in an ultra-high vacuum, resulting in an extremely low probability of interatomic collisions, effectively eliminating collision broadening and frequency shifts. The spectral center frequency is closer to the isolated atomic transition frequency, leading to better long-term stability. Therefore, the cold atom transition spectral lines themselves integrate almost all the key properties of an ideal frequency reference source, such as narrow linewidth, low noise, and absolute frequency accuracy. Using cold atom ensembles directly as the frequency discrimination reference for lasers is expected to break through the traditional performance limits set by thermal noise and the Doppler effect in principle, providing a more fundamental technical approach to realizing the next generation of ultra-high stability lasers. Summary of the Invention
[0005] To overcome the inherent defects of laser frequency stabilization techniques that utilize traditional high-precision optical resonators and atomic / molecular gas cells as frequency references, and addressing the intrinsic cavity length thermal noise caused by thermal fluctuations in the cavity mirror substrate and coating materials, as well as the limitations of Doppler broadening, collision broadening, and collision frequency shift inherent in atomic / molecular gas cell-based frequency stabilization techniques, this invention proposes for the first time a laser frequency stabilization method utilizing cold atom recoil resonance spectral lines. Based on integrated demodulation of the recoil resonance dispersive spectral lines of the cold atom system, the high signal-to-noise ratio dispersive spectral characteristics—recoil resonance spectral lines—naturally emerge in the probe light transmission measurement of the cold atom system itself are directly used as the source of frequency error signals. By applying precise frequency modulation and employing second harmonic demodulation techniques for the dispersive signal, a high-background-suppression error signal is efficiently extracted directly from the transmitted light intensity signal, and a simple feedback control loop is constructed to achieve active stabilization of the laser frequency. This scheme achieves a high degree of unity between the "measurement medium" and the "reference standard" in terms of physical entity and system function: the cold atom ensemble for scientific observation also serves as the frequency reference for stabilizing the detection laser itself, which can improve the short-term frequency stability, long-term reliability and structural compactness of the frequency stabilization system. It is of great value for promoting core instruments and key technologies in cutting-edge fields such as cold atom physics, quantum information science and high-precision spectroscopy.
[0006] The purpose of this invention is to propose a cold atom-stabilized laser and its implementation method. It utilizes the dispersive recoil resonance spectral line realized by the cold atom system in the probe light transmission measurement as the frequency error signal generation source, suppresses the effects of Doppler broadening, collision broadening and other influences, realizes the integration of the reference source and the probe body, and achieves laser frequency stabilization based on cold atoms. It is expected to improve the frequency stability and long-term reliability of the stabilized laser.
[0007] To achieve the above objectives, the present invention adopts the following technical solution.
[0008] A cold atom frequency-stabilized laser includes a laser, an optical isolator, a mirror, a beam splitter, a vacuum atomic gas cell, a photodetector, a high-pass filter, a low-noise preamplifier, a low-pass filter, a lock-in amplifier, a dual-channel function generator, an isolation amplifier, a summing circuit, a frequency multiplier, a PID controller, and a high-voltage amplifier.
[0009] The laser output light passes through an optical isolator and a reflector in sequence before being incident on a beam splitter. The beam splitter splits the incident light into a probe light and an output light. The probe light passes through cold atoms in a vacuum atom chamber along the optical path to obtain a recoil resonance spectrum based on cold atoms.
[0010] The photodetector is positioned after the vacuum atomic gas cell to receive the detection light passing through the vacuum atomic gas cell and output an electrical signal corresponding to the change in light intensity.
[0011] The output of the photodetector is connected to the signal input of the lock-in amplifier after passing through a high-pass filter, a low-noise preamplifier, and a low-pass filter in sequence.
[0012] The main output channel of the dual-channel function generator is used to output a frequency of The sinusoidal signal is input to the first input terminal of the summing circuit after being isolated by an isolation amplifier;
[0013] The other synchronous output channel of the dual-channel function generator is used to output a sine wave signal with the same frequency and phase as the main output channel. This sine wave signal is processed by a frequency multiplier to obtain a frequency of... The reference signal is input to the reference input terminal of the lock-in amplifier;
[0014] The lock-in amplifier is based on the input received at the reference input terminal. A frequency reference signal is used to perform phase-sensitive demodulation on the electrical signal from the low-pass filter, outputting an error signal, which is then input to the PID controller.
[0015] The output terminal of the PID controller is connected to the second input terminal of the summing circuit for outputting a correction voltage;
[0016] The summing circuit is used to sum the correction voltage with the frequency. The sinusoidal signals are linearly superimposed, and their output is connected to the control port of the laser via a high-voltage amplifier to perform feedback modulation on the output frequency of the laser, thereby forming a closed-loop frequency stabilization structure.
[0017] Furthermore, the laser may be, but is not limited to, an external cavity semiconductor laser or a fiber laser.
[0018] Furthermore, the control ports of the laser include a piezoelectric ceramic (PZT) modulation port and / or a current control port.
[0019] A method for implementing a cold atom frequency-stabilized laser includes the following steps:
[0020] 1) The laser to be stabilized is output from the laser. The laser passes through an optical isolator and a reflector in sequence and then enters a beam splitter. The beam splitter splits the laser into a probe beam and an output beam. The probe beam passes through cold atoms in a vacuum atom chamber along the optical path to obtain a recoil resonance spectrum based on cold atoms.
[0021] 2) The photodetector receives the probe light after passing through the vacuum atomic gas cell, converts the intensity change of the probe light into a voltage signal, and then filters and amplifies the voltage signal by passing it through a high-pass filter, a low-noise preamplifier, and a low-pass filter in sequence before inputting it to the signal input terminal of the lock-in amplifier.
[0022] 3) The frequency generated by the main output channel of the dual-channel function generator is... The sinusoidal signal is then passed through an isolation amplifier and input to the first input terminal of the summing circuit.
[0023] 4) A sine wave signal with the same frequency and phase as the main output channel is output from another synchronous output channel of the dual-channel function generator, and this sine wave signal is processed by a frequency multiplier to obtain a frequency of... The reference signal is input to the reference input terminal of the lock-in amplifier;
[0024] 5) Using a lock-in amplifier based on the above The reference signal is used to perform phase-sensitive demodulation on the electrical signal from the low-pass filter, outputting an error signal, which is then input to the PID controller.
[0025] 6) The PID controller performs proportional, integral, and derivative operations on the error signal, outputs a correction voltage, and inputs the correction voltage to the second input terminal of the summing circuit, along with the frequency... The sinusoidal signals are superimposed to form a composite signal;
[0026] 7) The composite signal is amplified by a high-voltage amplifier and then input to the control port of the laser to modulate the output frequency of the laser, so that the output frequency of the laser is stabilized at the position corresponding to the cold atom recoil resonance spectral line.
[0027] Furthermore, the cold atom clusters in the vacuum atomic chamber described in step 1) are prepared by one of the following methods: diffuse reflection laser cooling, optical agglomeration, or magneto-optical trap.
[0028] Furthermore, the cold atoms in the vacuum atomic chamber described in step 1) are rubidium atoms, cesium atoms, or strontium atoms, and the output wavelength of the laser is matched with the atomic transition wavelength of the corresponding cold atom.
[0029] Further, in step 1), when the cold atom is a rubidium-87 atom, the output wavelength of the laser is 780 nm, corresponding to the rubidium-87 atom's... to Energy level transition.
[0030] Furthermore, the frequency of the sinusoidal signal mentioned in step 3) The typical value is 25 kHz, with amplitude settings ranging from 50 to 500 millivolt peak-to-peak.
[0031] Furthermore, the correction voltage mentioned in step 6) is linearly superimposed on the sinusoidal signal in the summing circuit.
[0032] Further, the composite signal mentioned in step 7) is input to the piezoelectric ceramic modulation port and / or current control port of the laser.
[0033] This invention proposes a laser frequency stabilization method based on integrated demodulation of cold atom recoil resonance dispersive spectral lines. For the first time, the cold atom system itself is used as both a frequency reference and a frequency discriminator. It innovatively utilizes the high-contrast, narrow-linewidth recoil resonance dispersive signal in the transmission spectrum of cold atom clusters and employs second-harmonic optimal demodulation technology to achieve high-precision, robust, and active frequency stabilization. This method overcomes the limitations of traditional external reference sources in terms of thermal and Doppler noise, enabling frequency stabilization while simultaneously detecting cold atoms. It significantly improves the overall performance of the frequency stabilization system, particularly overcoming the extreme sensitivity to environmental disturbances inherent in traditional optical resonator-based schemes and the limitations of hot atom-based schemes due to spectral linewidth and collision frequency shifts. Therefore, it provides a simple and high-performance new technological path for realizing next-generation ultra-stable lasers.
[0034] The innovation of this invention is also reflected in the following aspects.
[0035] 1. Innovative System Architecture: This system is the first to propose and implement an integrated frequency stabilization architecture where the "probe medium is also the reference standard." The measured cold atom cluster is simultaneously used as the source of the frequency error signal, eliminating the need for additional, separate frequency reference devices (such as Fabry-Perot cavities or hot atom reference chambers), simplifying the system's optical path, and reducing environmental sensitivity.
[0036] 2. Innovation in signal processing methods: Addressing the inherent dispersion profile of recoil resonance transmission signals, innovative methods are employed to utilize second harmonics (…). Optimal demodulation. This method differs from traditional first harmonic techniques for processing absorptive signals. By extracting the second derivative of the dispersion function, it directly regenerates the dispersive error signal with excellent linearity from the signal superimposed on the background.
[0037] 3. Innovative Utilization of Reference Source Physical Properties: This invention innovatively utilizes the unique advantages of cold atom spectral lines as a frequency reference. Compared to hot atom references, cold atoms suppress Doppler broadening by several orders of magnitude, allowing the spectral linewidth to approach the natural linewidth; simultaneously, the ultra-high vacuum environment significantly reduces collision frequency shift. These physical advantages are directly translated into higher sensitivity of the frequency discrimination signal and a more accurate absolute frequency reference point. This invention is the first to experimentally observe recoil resonance lines with excellent dispersion linearity and extremely narrow linewidth using meter-scale lengths of cold rubidium atoms, a phenomenon previously unreported.
[0038] 4. Innovative Noise Suppression Mechanism: This scheme incorporates a unique noise suppression mechanism. First, second-harmonic demodulation itself has a strong ability to suppress DC background fluctuations and low-frequency noise. Second, by utilizing the inherent insensitivity of the transmission probe optical path to beam directionality fluctuations, the system's robustness to common mechanical vibrations is enhanced. The scheme is expected to achieve excellent short-term frequency stability and good long-term stability, providing a reliable frequency stabilization solution for cutting-edge experiments such as cold atom physics and quantum precision measurement. Attached Figure Description
[0039] The accompanying drawings, which are incorporated in and form part of this specification, provide examples consistent with the invention and, together with the description, serve to explain the principles of the invention.
[0040] Figure 1 This is a schematic diagram of the structure of a cold atom frequency-stabilized laser according to an embodiment of the present invention.
[0041] Figure 2 This is a recoil resonance spectrum diagram of a laser according to an embodiment of the present invention.
[0042] In the diagram: 1-Laser; 2-Optical isolator; 3-Mirror; 4-Beam splitter; 5-Vacuum atomic gas cell; 6-Photodetector; 7-High-pass filter; 8-Low-noise preamplifier; 9-Low-pass filter; 10-Lock-in amplifier; 11-Dual-channel function generator; 12-Isolation amplifier; 13-Summation circuit; 14-Frequency multiplier; 15-PID controller; 16-High-voltage amplifier. Detailed Implementation
[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be further described below with reference to the accompanying drawings in the embodiments, but the scope of protection of the present invention is not limited to the following description.
[0044] like Figure 1 As shown, this embodiment discloses a cold atom frequency-stabilized laser, including an optical system and a circuit system; wherein the optical system includes a laser 1, an optical isolator 2, a reflector 3, a beam splitter 4, and a vacuum atomic gas chamber 5; the electrical system includes a photodetector 6, a high-pass filter 7, a low-noise preamplifier 8, a low-pass filter 9, a lock-in amplifier 10, a dual-channel function generator 11, an isolation amplifier 12, a summing circuit 13, a frequency multiplier 14, a PID controller 15, and a high-voltage amplifier 16.
[0045] Laser 1 can be a common external cavity semiconductor laser, fiber laser, etc., to emit laser light. After the laser output, it first passes through optical isolator 2 to suppress any parasitic interference caused by reflected light returning to the laser cavity. Subsequently, the beam is split into two parts by beam splitter 4 after passing through mirror 3. One part of the light is used as probe light to pass through the cold atoms in vacuum atomic gas chamber 5 and input to photodetector 6, while the other part is used as laser output.
[0046] The photodetector 6 converts changes in light intensity into a voltage signal. This voltage signal first passes through a high-pass filter 7 to attenuate the DC background component in the signal and prevent subsequent amplifier saturation. Then, the signal enters a low-noise preamplifier 8 to amplify the weak AC modulation signal amplitude to a volt level suitable for processing by the lock-in amplifier 10. The amplified signal then passes through a low-pass filter 9 to suppress high-frequency noise, and finally enters the signal input port of the lock-in amplifier 10.
[0047] To achieve the generation of modulation signals and precise control of the laser, the main output channel of the dual-channel function generator 11 generates a frequency of... A sinusoidal signal is generated, the amplitude of which is set according to the modulation sensitivity of the laser piezoelectric ceramic (PZT) of laser 1. This sinusoidal signal is first transmitted to isolation amplifier 12. Isolation amplifier 12 can block ground loops that may form in subsequent feedback loops, ensuring the purity of the modulated signal. The isolated signal is then sent to one input of summing circuit 13.
[0048] To achieve phase-sensitive demodulation, another synchronous channel of the dual-channel function generator 11 outputs a sine wave with the same frequency and phase as the main output channel, which is then multiplied by the frequency multiplier 14. , and then this The signal is fed into the reference input port of the lock-in amplifier 10.
[0049] Lock-in amplifier 10 receives data from its reference input port. The frequency reference performs phase-sensitive demodulation on the signal from the low-pass filter 9 to generate the required error signal. This error signal is output from the output port of the lock-in amplifier 10 and input to the error signal input terminal of the PID controller 15. The PID controller 15 processes the error signal according to a set algorithm (proportional, integral, and derivative operations) to generate a slowly changing correction voltage.
[0050] This correction voltage is output from the PID controller 15 and fed back to the other input of the aforementioned summing circuit 13, where it is linearly superimposed with the sinusoidal modulation signal from the main output channel of the dual-channel function generator 11. Thus, the output of the summing circuit 13 contains a composite signal consisting of the modulation component for high-frequency detection and the signal for slow feedback correction. This composite signal is amplified by the high-voltage amplifier 16, which amplifies the weak modulation voltage to a level sufficient to efficiently drive the PZT of the laser 1, thereby continuously driving the PZT of the laser 1 and forming a complete feedback loop, ultimately automatically locking the laser frequency at the center of the cold atom recoil resonance spectral line.
[0051] In this example, the cold atoms in vacuum atomic chamber 5 are prepared using a diffuse reflection laser cooling method. This method can prepare large-volume cold atom clusters with lengths on the order of meters, making it easier to obtain the recoil resonance spectral lines of cold atoms during detection. Figure 2 As shown in the shaded area, this invention is based on a one-meter-long cold rubidium 87 atom cluster, which for the first time observed a strong recoil resonance spectrum. The frequency of the laser is locked to the center of the recoil resonance spectrum line. Compared with the saturation absorption spectrum line in the MHz range, its linewidth has a narrowing effect of more than three orders of magnitude, and its dispersion linearity is extremely suitable as a frequency stabilization reference.
[0052] In this example, the sine wave signal generated by the main output channel of the dual-channel function generator 11 has a frequency The typical value is 25 kHz, and the amplitude can be between 50 and 500 mV peak-to-peak, depending on the PZT modulation sensitivity of laser 1.
[0053] In this example, the beam splitter 4 ensures that the photodetector 6 remains unsaturated while maximizing the signal-to-noise ratio.
[0054] In this example, the cold atoms in vacuum atomic gas chamber 5 can be cold rubidium 87 ( ( ) atoms, and at the same time, the wavelength of laser 1 matches the transition wavelength of the cold atoms, which is a corresponding atom to 780nm energy level transition.
[0055] In this example, the error signal is fed back to the PZT port of laser 1. However, theoretically, the error signal can also be fed back to the current control port of laser 1 for frequency stabilization, or simultaneously fed back to both the PZT port and the current control port of laser 1.
[0056] This embodiment also provides a method for implementing a cold atom frequency-stabilized laser. The method involves using precise electronic connections and feedback control to convert the physical response of the cold atom system into a stable laser frequency output. Specifically, the method includes the following steps:
[0057] 1) The laser beam to be stabilized is output from laser 1, passes through optical isolator 2 and reflector 3 and is split into two parts by beam splitter 4. One part of the light is used as probe light to pass through the cold atoms in vacuum atomic gas chamber 5 and input to photodetector 6, while the other part is used as laser output.
[0058] 2) The photodetector 6 converts the change in light intensity into a voltage signal. This voltage signal passes through a high-pass filter 7, a low-noise preamplifier 8, and a low-pass filter 9, and is then connected to the signal input port of the lock-in amplifier 10.
[0059] 3) The main output channel of the dual-channel function generator 11 generates a frequency of... The sinusoidal signal is transmitted to the isolation amplifier 12 and then sent to one input of the summing circuit 13.
[0060] 4) The other synchronous channel of the dual-channel function generator 11 outputs a sine wave with the same frequency and phase as the main output channel, which is multiplied by the frequency multiplier 14. , and then this The signal is fed into the reference input port of the lock-in amplifier 10.
[0061] 5) Lock-in amplifier 10 receives data from its reference input port. The frequency reference performs phase-sensitive demodulation on the signal from the low-pass filter 9 to generate the required error signal. This error signal is output from the output port of the lock-in amplifier 10 and input to the error signal input terminal of the PID controller 15.
[0062] 6) The PID controller 15 processes the error signal and generates a correction voltage. This correction voltage is output from the PID controller 15 and fed back to the other input of the aforementioned summing circuit 13, where it is linearly superimposed with the sinusoidal modulation signal from the main output channel of the dual-channel function generator 11. Thus, the output of the summing circuit 13 contains a composite signal of modulation components for high-frequency detection and slow feedback correction.
[0063] 7) The composite signal above, after passing through the high voltage amplifier 16, continuously drives the PZT of the laser 1, thereby forming a complete feedback closed loop, and finally automatically locking the laser frequency at the center of the cold atom recoil resonance spectrum line.
[0064] Finally, it should be noted that the above description of the specific embodiments of this patent is merely for illustrative purposes and is not intended to limit its scope of protection. Those skilled in the art should understand that after reading the above description, various modifications or alterations can be made to this invention, but these equivalent forms also fall within the scope defined by the claims of this invention.
[0065] This invention provides a laser frequency stabilization method based on integrated demodulation of cold atom recoil resonance dispersive spectral lines. Its core lies in innovatively using the cold atom system itself as an embedded frequency and discrimination reference, and innovatively utilizing second-harmonic optimal demodulation technology for the original dispersive signal. This scheme effectively overcomes the inherent defects of traditional high-precision optical resonator-based schemes, such as extreme sensitivity to environmental vibrations and temperature fluctuations, and complex and expensive structures. It also avoids the accuracy and stability limitations introduced by Doppler broadening and collision frequency shift in hot atom-based schemes. By unifying the "measurement medium" and the "reference standard," this method provides a novel, simple, and high-performance technical path for obtaining highly stable lasers.
[0066] The method described in this invention is not only applicable to cold atom systems prepared using alkali metal atoms such as rubidium-87, rubidium-85, and cesium, but its principle can also be extended to other atomic (such as strontium, ytterbium, etc.) or molecular systems, as long as the system can generate detectable resonant transmission lines with dispersive characteristics. Furthermore, in specific implementations, the modulation frequency, modulation depth, demodulation phase, PID parameters, etc., can all be optimized and adjusted according to the actual atom type, spectral linewidth, and system noise characteristics; all of these fall within the scope of protection of this invention.
[0067] Therefore, any person skilled in the art can modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features without departing from the spirit and scope of protection defined by the claims. These modifications, equivalent substitutions, and improvements should all be considered to be included within the scope of protection of this invention.
Claims
1. A cold atom frequency-stabilized laser, characterized in that, This includes lasers, optical isolators, mirrors, beam splitters, vacuum atomic gas cells, photodetectors, high-pass filters, low-noise preamplifiers, low-pass filters, lock-in amplifiers, dual-channel function generators, isolation amplifiers, summing circuits, frequency multipliers, PID controllers, and high-voltage amplifiers. The laser output light passes through an optical isolator and a reflector in sequence before being incident on a beam splitter. The beam splitter splits the incident light into a probe light and an output light. The probe light passes through cold atoms in a vacuum atom chamber along the optical path to obtain a recoil resonance spectrum based on cold atoms. The photodetector is positioned after the vacuum atomic gas cell to receive the detection light passing through the vacuum atomic gas cell and output an electrical signal corresponding to the change in light intensity. The output of the photodetector is connected to the signal input of the lock-in amplifier after passing through a high-pass filter, a low-noise preamplifier, and a low-pass filter in sequence. The main output channel of the dual-channel function generator is used to output a frequency of The sinusoidal signal is input to the first input terminal of the summing circuit after being isolated by an isolation amplifier; The other synchronous output channel of the dual-channel function generator is used to output a sine wave signal with the same frequency and phase as the main output channel. This sine wave signal is processed by a frequency multiplier to obtain a frequency of... The reference signal is input to the reference input terminal of the lock-in amplifier; The lock-in amplifier is based on the input received at the reference input terminal. A frequency reference signal is used to perform phase-sensitive demodulation on the electrical signal from the low-pass filter, outputting an error signal, which is then input to the PID controller. The output terminal of the PID controller is connected to the second input terminal of the summing circuit for outputting a correction voltage; The summing circuit is used to sum the correction voltage with the frequency. The sinusoidal signals are linearly superimposed, and their output is connected to the control port of the laser via a high-voltage amplifier to perform feedback modulation on the output frequency of the laser, thereby forming a closed-loop frequency stabilization structure.
2. The cold atom frequency-stabilized laser as described in claim 1, characterized in that, The laser is an external cavity semiconductor laser or a fiber laser.
3. The cold atom frequency-stabilized laser as described in claim 1, characterized in that, The control ports of the laser include a piezoelectric ceramic modulation port and / or a current control port.
4. A method for implementing the cold atom frequency-stabilized laser according to any one of claims 1-3, characterized in that, Includes the following steps: 1) The laser to be stabilized is output from the laser. The laser passes through an optical isolator and a reflector in sequence and then enters a beam splitter. The beam splitter splits the laser into a probe beam and an output beam. The probe beam passes through cold atoms in a vacuum atom chamber along the optical path to obtain a recoil resonance spectrum based on cold atoms. 2) The photodetector receives the probe light after passing through the vacuum atomic gas cell, converts the intensity change of the probe light into a voltage signal, and then filters and amplifies the voltage signal by passing it through a high-pass filter, a low-noise preamplifier, and a low-pass filter in sequence before inputting it to the signal input terminal of the lock-in amplifier. 3) The frequency generated by the main output channel of the dual-channel function generator is... The sinusoidal signal is then passed through an isolation amplifier and input to the first input terminal of the summing circuit. 4) A sine wave signal with the same frequency and phase as the main output channel is output from another synchronous output channel of the dual-channel function generator, and this sine wave signal is processed by a frequency multiplier to obtain a frequency of... The reference signal is input to the reference input terminal of the lock-in amplifier; 5) Using a lock-in amplifier based on the above The reference signal is used to perform phase-sensitive demodulation on the electrical signal from the low-pass filter, outputting an error signal, which is then input to the PID controller. 6) The PID controller performs proportional, integral, and derivative operations on the error signal, outputs a correction voltage, and inputs the correction voltage to the second input terminal of the summing circuit, along with the frequency... The sinusoidal signals are superimposed to form a composite signal; 7) The composite signal is amplified by a high-voltage amplifier and then input to the control port of the laser to modulate the output frequency of the laser, so that the output frequency of the laser is stabilized at the position corresponding to the cold atom recoil resonance spectral line.
5. The implementation method as described in claim 4, characterized in that, The cold atom clusters in the vacuum atom chamber described in step 1) are prepared by one of the following methods: diffuse reflection laser cooling, optical agglomeration, or magneto-optical trap.
6. The implementation method as described in claim 4 or 5, characterized in that, The cold atoms in the vacuum atomic gas chamber mentioned in step 1) are rubidium atoms, cesium atoms or strontium atoms, and the output wavelength of the laser is matched with the atomic transition wavelength of the corresponding cold atom.
7. The implementation method as described in claim 6, characterized in that, In step 1), when the cold atom is a rubidium-87 atom, the output wavelength of the laser is 780 nm, corresponding to the rubidium-87 atom. to Energy level transition.
8. The implementation method as described in claim 4, characterized in that, The frequency of the sinusoidal signal mentioned in step 3) The typical value is 25 kHz, with amplitude settings ranging from 50 to 500 millivolt peak-to-peak.
9. The implementation method as described in claim 4, characterized in that, In step 6), the correction voltage and the sinusoidal signal are linearly superimposed in the summing circuit.
10. The implementation method as described in claim 4, characterized in that, The composite signal mentioned in step 7) is input to the piezoelectric ceramic modulation port and / or current control port of the laser.