Integrated cross-band reference source based on quantum frequency-selective two-color laser and its implementation method

Abstract

The present invention discloses an integrated cross-band reference source based on quantum frequency-selective two-color laser and an implementation method thereof, which comprises a potassium atom Faraday laser, an atomic spectrum frequency stabilization system, a PDH frequency stabilization system, an optical frequency comb system, and a terahertz detector; the potassium atom Faraday laser generates a two-color laser which is input into a first polarization beam splitter and then split into two beams, one of which is input into the atomic spectrum frequency stabilization system, and the other is incident on a second polarization beam splitter via an acousto-optic modulator and a pinhole aperture in sequence; the second polarization beam splitter splits the incident light beam into two beams, one of which is incident into a third polarization beam splitter, and the other is input into the PDH frequency stabilization system; the atomic spectrum frequency stabilization system and the PDH frequency stabilization system are used to stabilize the frequency of the two-color laser; the third polarization beam splitter splits the incident light beam into two beams, one of which is output as an optical frequency signal, and the other is frequency-down-converted by the optical frequency comb system to obtain a microwave signal, and the remaining optical frequency signal is mixed by a terahertz detector to obtain a terahertz signal.

Description

Technical Field

[0001] The present invention belongs to the field of laser technology, and in particular relates to an integrated cross-band reference source based on quantum frequency-selective two-color laser and an implementation method thereof. Background Art

[0002] Microwave, terahertz, and optical frequency reference sources play an important role in the fields of quantum precision measurement, high-speed wireless communication, and high-resolution imaging. For example, highly stable microwaves and highly coherent light sources are key components for realizing CPT atomic clocks, atomic interferometers, and atomic gravimeters. 87 Taking the Rb CPT atomic clock as an example, a microwave source is used to generate a 3.417 GHz microwave signal, which is modulated and loaded into the optical frequency signal to generate multi-frequency Raman light. The frequency interval of its ±1st order sideband is exactly equal to 87 The ground-state energy level gap of Rb is used to excite Rb atoms to produce CPT transitions. Highly stable, low-noise terahertz signals have large bandwidth and strong directionality, helping to improve the directional nature and anti-interference capabilities of signal propagation, serving 5G and 6G high-speed communication systems. Furthermore, microwave, terahertz, and optical frequency reference sources also play an important role in high-resolution imaging. For example, synthetic aperture radar (SAR) uses microwave imaging, capable of penetrating clouds, rain, fog, and even imaging at night, and is widely used in surface cover monitoring, topographic mapping, and disaster assessment. LiDAR (lidar) uses laser pulses for distance measurement, enabling high-precision three-dimensional imaging. Terahertz signals' non-destructive nature to biological tissue and their sensitivity to water molecules give them considerable potential for medical imaging applications such as skin cancer detection and tissue stratification.

[0003] There are numerous mechanisms for generating microwave, terahertz, and optical frequency reference sources, each with its own unique characteristics, advantages, and limitations. Microwave signal generation primarily involves direct analog frequency synthesis, which uses a harmonic generator to process a given reference signal to generate a series of harmonics. These harmonics are then multiplied and divided to produce a large number of discrete frequencies. This method offers a simple implementation principle and low phase noise, but is susceptible to spurious components. Phase-locked frequency synthesis utilizes phase-locked loop (PLL) technology to multiply or divide a low-frequency signal to generate the desired microwave frequency. This method allows for flexible frequency generation by adjusting the division and multiplication ratios, but the PLL introduces additional phase noise. Direct digital frequency synthesis first accumulates and stores a digital control word signal in a register. Then, using the Nyquist sampling theorem, a sinusoidal lookup table is used to generate the desired analog waveform. This method offers advantages such as high resolution and low power consumption, but requires further improvement in aspects such as phase noise and spurious signals. Terahertz reference sources are primarily generated through electronic and photonic devices. For example, the quantum cascade effect in semiconductor materials can be used to generate high-frequency and high-power terahertz signals, but the frequency tuning range is relatively narrow, making it difficult to cover a wide bandwidth of terahertz frequencies. Free electron lasers generate terahertz radiation by the motion of high-energy electron beams in a magnetic field, offering a wide frequency band coverage but relatively high operating costs. Photoconductive antennas, which use ultrafast laser pulses to excite carriers in semiconductor materials, can also generate terahertz radiation, but their power output is relatively limited. Optical frequency signal reference sources primarily include various types of lasers and light-emitting diodes, which typically can only output optical frequency signals in a single wavelength band, making it difficult to achieve high-coherence, large-frequency-difference dual-wavelength optical frequency signal output.

[0004] Furthermore, current microwave, terahertz, and optical reference sources are independent of one another, and there is no integrated cross-band reference source that can simultaneously cover all three frequency bands. In numerous applications, such as quantum state manipulation, modern high-speed communications, and sensing, it is often necessary to simultaneously utilize signals from multiple frequency bands. Therefore, separate reference sources are required in practical applications, each requiring independent control and calibration mechanisms, significantly increasing the complexity and size of the system. Furthermore, independent reference sources can introduce phase noise and frequency drift, leading to synchronization issues between signals from different frequency bands. Summary of the Invention

[0005] To overcome the above difficulties, the present invention intends to develop an integrated cross-band reference source based on quantum frequency-selective two-color laser, which mainly includes a potassium atom Faraday laser (which can also be extended to cesium atom and rubidium atom Faraday lasers), an atomic spectrum frequency stabilization system, a PDH frequency stabilization system, an optical frequency comb system, and a terahertz detector. The present invention utilizes the Faraday effect when the laser frequency is nearly resonant with the D1 and D2 transition frequencies of potassium atoms to achieve the selection and control of the laser frequency. In combination with the transmission characteristics of the potassium atom Faraday anomalous dispersion atomic filter at the D1 and D2 transition lines, the temperature and magnetic field strength of the potassium atom ensemble environment in the potassium atom Faraday anomalous dispersion atomic filter are precisely controlled to change the relative intensity of the Faraday effect at different frequencies, thereby achieving a two-color laser with wavelengths automatically corresponding to the D1 and D2 transition lines of potassium atoms. The wavelength corresponding to the D1 transition line of potassium atoms is 770nm, and the wavelength corresponding to the D2 transition line of potassium atoms is 767nm, with a frequency difference of about 1.7THz. The invention further utilizes the cavity mode of the high-fineness ultrastable resonant cavity and the cold atomic ensemble to achieve the two-color laser with wavelengths automatically corresponding to the D1 and D2 transition lines of potassium atoms. The atomic spectrum is used as a frequency reference to narrow the linewidth of the two-color laser and optimize the short-term and long-term frequency stability of the two-color laser respectively, thereby realizing an ultra-stable two-color optical frequency signal with a large frequency difference; because the two-color lasers are generated by the same resonant cavity, the two have excellent coherence, and the terahertz signal generated by their beat frequency is not affected by the laser resonant cavity drift jitter caused by external vibration and thermal noise, and has excellent stability; further, using a high signal-to-noise ratio optical frequency comb as a large coefficient frequency divider, combined with the principle of optical frequency division, the relative stability of the local oscillator light can be losslessly transferred to the microwave band, thereby realizing a highly stable microwave, terahertz, and optical frequency integrated cross-band reference source, solving the problem of the independence of traditional microwave, terahertz, and optical frequency reference sources. See the following description for details:

[0006] The potassium atom Faraday laser 1 comprises a laser diode 101 coated with an anti-reflection film, a collimating lens 102, a potassium atom Faraday anomalous dispersion atomic filter 103, and a partial reflection mirror 104. The potassium atom Faraday anomalous dispersion atomic filter 103 comprises a first Glan-Taylor prism 1031, a potassium atom gas cell 1032, a second Glan-Taylor prism 1033, and a permanent magnet 1034.

[0007] The polarization directions of the first Glan-Taylor prism 1031 and the second Glan-Taylor prism 1033 are orthogonal, and the potassium atomic gas chamber 1032 is filled with potassium of natural abundance;

[0008] The anti-reflection coated laser diode 101 outputs a fluorescence signal with a spectral range covering both 770 nm and 767 nm. After being collimated by the collimating lens 102, the light passes through the first Glan-Taylor prism 1031 and the potassium atomic gas chamber 1032 in sequence. The Faraday rotation effect occurs in the potassium atomic gas chamber 1032, causing the polarization direction of the incident light to rotate. The light then passes through the second Glan-Taylor prism 1033. The partial reflector 104 reflects part of the light back to the anti-reflection coated laser diode 101, forming an optical resonant cavity. The generated laser light is then transmitted and outputted from the partial reflector 104.

[0009] When the temperature of the potassium atom gas chamber 1032 and the magnetic field strength of the permanent magnet 1034 are appropriate, the potassium atom Faraday laser 1 simultaneously emits two-color lasers with wavelengths of 770 nm and 767 nm.

[0010] The dual-color laser is split into two laser beams by the first half-wave plate 2 and the first polarization beam splitter 3. The two laser beams are then reflected twice by the first reflector 4 and the second reflector 5 and enter the atomic spectrum frequency stabilization system 6. The atomic spectrum frequency stabilization system 6 then outputs a servo signal that is fed back to the current and cavity length control terminals of the potassium atom Faraday laser 1 to lock the dual-color laser frequency.

[0011] The reflected path passes through the acousto-optic modulator 7 to obtain 0th-order and +1st-order diffracted light, of which the 0th-order light is blocked by the pinhole diaphragm 8, and the +1st-order light is transmitted through the pinhole diaphragm 8 and then split into two paths by the second half-wave plate 9 and the second polarization beam splitter 10. The reflected path passes through the PDH frequency stabilization system 11, and the output servo signal is fed back to the driving end of the acousto-optic modulator 7 to achieve re-locking of the dual-color laser frequency;

[0012] The two-color laser light transmitted through the second polarization beam splitter 10 is split by the third half-wave plate 12 and the third polarization beam splitter 13, and is reflected as the output end of the optical frequency signal.

[0013] The two-color laser light transmitted through the third polarization beam splitter 13 enters the optical frequency comb system 14 and beats with the two comb teeth of the optical frequency comb system 14, thereby achieving high-precision transmission of the optical frequency signal to the microwave frequency and generating a highly stable microwave signal.

[0014] The two-color laser light after interacting with the optical frequency comb system 14 is mixed by the terahertz detector 15 and then separated to obtain a terahertz signal.

[0015] The innovative features and beneficial effects of the technical solution provided by the present invention are:

[0016] 1. This invention utilizes the broad spectrum characteristics of an antireflection-coated laser diode and the unique transmission characteristics of a potassium atom Faraday anomalous dispersion atomic filter. The proposed potassium atom Faraday laser can simultaneously output two-color lasers with wavelengths of 770nm and 767nm, with a wavelength interval of 3nm. This enables the simultaneous output of two-color lasers with a large frequency difference within a single laser, and the wavelengths automatically correspond to the potassium atom D1 and D2 transition lines.

[0017] 2. The present invention utilizes the cavity mode of the ultrastable resonant cavity as a macroscopic frequency reference, which can effectively narrow the linewidth of the two-color laser and optimize the short-term frequency stability of the two-color laser. It also utilizes the atomic transition line as a microscopic frequency reference to optimize the long-term frequency stability of the two-color laser, thereby realizing an optical frequency signal with low phase noise, narrow linewidth, and high frequency stability.

[0018] 3. The dual-color lasers implemented in the present invention share the same resonant cavity and therefore have high coherence characteristics. Furthermore, the terahertz signal generated by the dual-color laser beat frequency exhibits high frequency stability and is immune to the influence of laser resonant cavity drift jitter caused by external vibrations and thermal noise.

[0019] 4. The present invention combines optical frequency division technology with the use of an optical frequency comb as a large-coefficient frequency divider to divide the low-noise optical frequency signal into the microwave band, which can achieve the lossless transfer of the relative stability of the two-color laser to the microwave signal, thereby realizing a highly stable, simultaneously output microwave, terahertz, and optical frequency cross-band integrated reference source. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of the structure of the integrated cross-band reference source based on quantum frequency-selective two-color laser proposed in the present invention.

[0021] Figure 2 This is a schematic structural diagram of the potassium atom Faraday laser based on quantum frequency selection provided by the present invention.

[0022] Figure 3 for 39 Energy level diagram related to K D1 and D2 transition lines.

[0023] Figure 4 Schematic diagram of the principle of using an optical frequency comb to down-convert a two-color laser into a microwave radiation source provided by the present invention.

[0024] Among them, 1-potassium atom Faraday laser; 2-first half-wave plate; 3-first polarization beam splitter; 4-first reflector; 5-second reflector; 6-atomic spectrum frequency stabilization system; 7-acousto-optic modulator; 8-pinhole aperture; 9-second half-wave plate; 10-second polarization beam splitter; 11-PDH frequency stabilization system; 12-third half-wave plate; 13-third polarization beam splitter; 14-optical frequency comb system; 15-terahertz detector; 101-antireflection coated laser diode; 102-collimating lens; 103-potassium atom Faraday anomalous dispersion atomic filter; 104-partial reflector; 1031-first Glan-Taylor prism; 1032-potassium atom gas chamber; 1033-second Glan-Taylor prism; 1034-permanent magnet. DETAILED DESCRIPTION

[0025] In order to make the purpose, content, and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below with reference to the accompanying drawings and examples.

[0026] like Figure 1 As shown, the device includes:

[0027] Potassium atom Faraday laser 1 is the source of 770nm and 767nm dual-color lasers. Its internal structure is as follows: Figure 2 As shown, it includes a laser diode 101 coated with an anti-reflection film, which outputs a wide-spectrum fluorescence signal with a high gain at wavelengths of 770nm and 767nm; a collimating lens 102, which is used to collimate the light comb with a large divergence angle emitted from the laser diode 101 coated with an anti-reflection film into a parallel light beam; a potassium atom Faraday anomalous dispersion atomic filter 103, which includes a first Glan-Taylor prism 1031, a potassium atom gas chamber 1032, a second Glan-Taylor prism 1033, and a permanent magnet 1034. The first Glan-Taylor prism 1031 converts the collimated incident light beam into linearly polarized light; the potassium atom gas chamber 1032 is filled with natural potassium, wherein 39 K accounts for the vast majority, accounting for 93.3%, and the outer surface of the potassium atom gas chamber 1032 is wrapped with a thermoelectric cooler (TEC) for regulating the temperature inside the potassium atom gas chamber 1032; the polarization direction of the second Glan-Taylor prism 1033 is orthogonal to the polarization direction of the first Glan-Taylor prism 1031; the magnetic field intensity direction of the permanent magnet is consistent with the light propagation direction, and is used to generate Zeeman energy level splitting of the potassium atoms in the potassium atom gas chamber 1032; when the frequency of the incident light is located at the D1 transition line or the D2 transition line of the potassium atom (such as Figure 3When the incident light is near the potassium atom Faraday anomalous dispersion atomic filter (as shown), a Faraday rotation effect will be generated, and its polarization plane will rotate. When the rotation angle is 90° and its odd multiples, it can pass through the second Glan-Taylor prism 1033 with low loss. When the frequency of the incident light is far away from the D1 transition line or the D2 transition line of the potassium atom, its polarization direction will not rotate and it cannot pass through the second Glan-Taylor prism 1033; the partial reflector 104 reflects a part of the light emitted from the potassium atom Faraday anomalous dispersion atomic filter back to the laser diode 101 coated with the anti-reflection film, forming an optical resonant cavity, realizing the oscillation of the light beam between the rear end face of the laser diode 101 coated with the anti-reflection film and the partial reflector 104, thereby generating laser light, which is transmitted and output from the partial reflector 104.

[0028] The temperature of the potassium atom gas chamber 1032 and the magnetic field strength of the permanent magnet 1034 will affect the transmission characteristics of the potassium atom Faraday anomalous dispersion atomic filter 103 at the potassium atom D1 transition line and the D2 transition line, thereby affecting the mode competition in the cavity of the potassium atom Faraday laser 1; when the peak transmittance of the potassium atom Faraday anomalous dispersion atomic filter 103 at the potassium atom D1 transition line and the D2 transition line is approximately the same, the potassium atom Faraday laser 1 can simultaneously output 770nm and 767nm two-color lasers, and the wavelengths automatically correspond to the potassium atom D1 and D2 transition lines, respectively.

[0029] The first half-wave plate 2 can change the polarization direction of the two-color laser and cooperate with the first polarization beam splitter 3 to realize the splitting of the two-color laser. Rotating the first half-wave plate 2 can change the power distribution of the transmitted light and the reflected light; the two-color laser transmitted through the first polarization beam splitter 3 is used for atomic spectrum frequency stabilization, and the two-color laser reflected by the first polarization beam splitter 3 is used for the next application.

[0030] The first reflector 4 and the second reflector 5 have high reflectivity to the dual-color laser and are used to change the propagation direction of the dual-color laser.

[0031] The atomic spectrum frequency stabilization system 6 is used to compare the difference between the two-color laser frequency and the potassium atom resonant transition line frequency, and generate a servo signal to feed back to the current and cavity length control ends of the potassium atom Faraday laser 1 to achieve frequency locking of the two-color laser and optimize the long-term stability of the two-color laser; the atomic spectrum frequency stabilization system 6 contains a potassium cold atom system, which specifically uses Doppler cooling, polarization gradient cooling and other methods to reduce the movement speed of potassium atoms and achieve cooling of potassium atoms, thereby suppressing the effects of collision broadening and Doppler broadening, and providing a stable and reliable microscopic reference for the atomic spectrum frequency stabilization system; the atomic spectrum frequency stabilization system can adopt a modulation transfer spectrum frequency stabilization system, a saturated absorption spectrum frequency stabilization system, an atomic dichroism frequency stabilization system, etc.

[0032] The acousto-optic modulator 7 performs frequency modulation on the dual-color laser to generate modulation sidebands such as level 0 and level +1. Its function is to precisely control the frequency of the dual-color laser by receiving the servo signal from the PDH frequency stabilization system 11, thereby achieving secondary locking of the dual-color laser frequency.

[0033] The pinhole aperture 8 is used to block the 0th order and other order diffraction light to ensure that only the +1st order diffraction light passes through.

[0034] The second half-wave plate 9 and the second polarization beam splitter 10 further split the two-color laser light passing through the pinhole aperture 8 into a transmission path and a reflection path. The reflection path is used for the PDH frequency stabilization system 11, and the transmission path is used for the next application.

[0035] The PDH frequency stabilization system 11 contains a high-fineness ultrastable resonant cavity. The cavity mode of the resonant cavity provides a macroscopic frequency reference for comparing the difference between the dual-color laser frequency and the cavity mode frequency. It also generates a servo signal that is fed back to the control end of the acousto-optic modulator 7 to achieve secondary locking of the dual-color laser frequency, thereby narrowing the linewidth of the dual-color laser and optimizing the short-term stability of the dual-color laser.

[0036] The third half-wave plate 12 and the third reflector 13 are used to further split the two-color laser transmitted by the second polarization beam splitter 10 into a transmission path and a reflection path. The reflection path serves as the output end of the optical frequency signal, specifically including high-coherence, large-frequency-difference two-color lasers with wavelengths of 770nm and 767nm, and the transmission path is used for the next application.

[0037] The optical frequency comb system 14 is used to convert the two-color laser output by the stabilized potassium atom Faraday laser 1 into a down-converted one. The specific conversion principle is as follows: Figure 4 As shown, the frequency of the two-color laser is f L1 and f L2 , respectively beat with the N1th and N2th comb teeth in the optical frequency comb system 14, and obtain frequencies f b1 and f b2 The microwave signal; the initial frequency f0 and repetition frequency f of the optical comb can be strictly controlled by microwave phase-locking technology. r , in order to achieve high-precision transmission from optical frequency to microwave frequency, the two output frequencies are f b1 and f b2 microwave signal.

[0038] The terahertz detector 15 is used to receive the two-color laser after interacting with the optical frequency comb system 14 and extract a high-purity terahertz signal; the terahertz signal is generated by mixing the two-color laser with wavelengths of 770nm and 767nm, and its frequency depends on the difference frequency between the 770nm and 767nm two-color lasers, which is approximately 1.4THz; the actual frequency value can be adjusted by adjusting the temperature of the potassium atom gas chamber 1032 and the magnetic field strength of the permanent magnet 1034.

[0039] The above is only a preferred embodiment of the present invention. It should be pointed out that for other alkali metal elements such as rubidium and cesium, as well as alkaline earth metal elements, the content of the present invention can also be used to realize an integrated cross-band reference source, which should be regarded as the scope of protection of the present invention; for ordinary technicians in this technical field, without departing from the technical principles of the present invention, several improvements and variations can be made, and these improvements and variations should also be regarded as the scope of protection of the present invention.

Claims

1. An integrated cross-band reference source based on quantum frequency-selective two-color laser, characterized in that: It includes a potassium atom Faraday laser (1), an atomic spectrum frequency stabilization system (6), a PDH frequency stabilization system (11), an optical frequency comb system (14), and a terahertz detector (15); The potassium atom Faraday laser (1) is used to generate a two-color laser and input it into a first polarization beam splitter (3) to split it into two beams, one beam being input into the atomic spectrum frequency stabilization system (6), and the other beam being incident on a second polarization beam splitter (10) via an acousto-optic modulator (7) and a pinhole aperture (8) in sequence; The atomic spectrum frequency stabilization system (6) internally includes a potassium cold atom system, which is used to compare the difference between the frequency of the two-color laser generated by the potassium atom Faraday laser (1) and the frequency of the potassium atom resonant transition line in the potassium cold atom system to generate a servo signal and feed it back to the current and cavity length control end of the potassium atom Faraday laser (1), thereby optimizing the frequency stability of the two-color laser output by the potassium atom Faraday laser (1); The acousto-optic modulator (7) is used to perform frequency modulation on the dual-color laser to generate multi-order diffraction light, and to compensate and control the frequency of the dual-color laser by receiving a servo signal from a PDH frequency stabilization system (11), thereby optimizing the frequency stability of the dual-color laser; The pinhole aperture (8) is used to block the 0th order and other order diffraction light, ensuring that only the +1st order diffraction light passes through; The second polarization beam splitter (10) is used to split the incident light beam into two beams, one beam is incident on the third polarization beam splitter (13), and the other beam is input into the PDH frequency stabilization system (11); The PDH frequency stabilization system (11) is used to generate a servo signal based on the difference between the cavity mode frequency of the internal ultra-stable resonant cavity and the input dual-color laser frequency, and feed it back to the control end of the acousto-optic modulator (7); The third polarization beam splitter (13) is used to split the incident light beam into two beams, one beam is output as an optical frequency signal, the other beam is frequency-down-converted by the optical frequency comb system (14) and output as a microwave signal, and the remaining two-color laser is input into a terahertz detector (15); The terahertz detector (15) is used for frequency mixing of the two-color laser to obtain a terahertz signal.

2. The integrated cross-band reference source according to claim 1, characterized in that: The potassium atom Faraday laser (1) generates two-color laser light which is input into a first polarization beam splitter (3) via a first half-wave plate (2); the first half-wave plate (2) is used to adjust the polarization direction of the incident two-color laser light, thereby changing the power distribution of the transmitted light and the reflected light output by the first polarization beam splitter (3).

3. The integrated cross-band reference source according to claim 1, characterized in that: A second half-wave plate (9) is provided between the pinhole aperture (8) and the second polarization beam splitter (10); the second half-wave plate (9) is used to adjust the polarization direction of the incident two-color laser light, thereby changing the power distribution of the transmitted light and the reflected light output by the second polarization beam splitter (10).

4. The integrated cross-band reference source according to claim 1, wherein: A third half-wave plate (12) is arranged before the third polarization beam splitter (13); the third half-wave plate (12) is used to adjust the polarization direction of the incident two-color laser and change the power distribution of the transmitted light and the reflected light output by the third polarization beam splitter (13).

5. The integrated cross-band reference source according to claim 1, characterized in that: The outer surface of the atomic chamber of the potassium atom Faraday laser is wrapped with a thermoelectric cooler for regulating the temperature inside the atomic chamber.

6. A method for realizing an integrated cross-band reference source based on quantum frequency-selective two-color laser, comprising the following steps: 1) A potassium atom Faraday laser (1) is used to generate a two-color laser and input the two-color laser into a first polarization beam splitter (3) and then split into two beams, one beam being input into an atomic spectrum frequency stabilization system (6), and the other beam being incident into a second polarization beam splitter (10) in sequence through an acousto-optic modulator (7) and a pinhole aperture (8); wherein the atomic spectrum frequency stabilization system (6) is used to generate a servo signal based on the difference between the two-color laser frequency output by the potassium atom Faraday laser (1) and the potassium atom resonance transition line of the potassium cold atom system in the atomic spectrum frequency stabilization system (6) and feedback to the potassium atom Faraday laser. The current and cavity length control ends of the optical device (1) optimize the frequency stability of the two-color laser output by the potassium atom Faraday laser (1); the acousto-optic modulator (7) is used to frequency modulate the two-color laser to generate multi-order diffraction light, and compensate the frequency of the two-color laser by receiving a servo signal from the PDH frequency stabilization system (11), so that the two-color laser is locked to the cavity mode frequency of the ultra-stable resonant cavity of the PDH frequency stabilization system (11), thereby optimizing the frequency stability of the two-color laser; the pinhole aperture (8) is used to block the 0th order and other order diffraction light to ensure that only the +1st order diffraction light passes; 2) The second polarization beam splitter (10) splits the incident light beam into two beams, one beam is incident on the third polarization beam splitter (13), and the other beam is input into the PDH frequency stabilization system (11); wherein the PDH frequency stabilization system (11) is used to generate a servo signal based on the difference between the cavity mode frequency of the ultra-stable resonant cavity inside the system and the received dual-color laser frequency, and feed it back to the control end of the acousto-optic modulator (7); 3) The third polarization beam splitter (13) splits the incident light beam into two beams, one beam is output as an optical frequency signal, the other beam is frequency-down-converted by the optical frequency comb system (14) and outputs a microwave signal, and the remaining two-color laser signal is input into the terahertz detector (15); 4) The terahertz detector (15) performs frequency mixing on the received two-color laser to output a terahertz signal.

7. The method according to claim 6, characterized in that The potassium atom Faraday laser (1) generates a two-color laser which is input to a first polarization beam splitter (3) via a first half-wave plate (2); the first half-wave plate (2) is used to adjust the polarization direction of the incident two-color laser and change the power distribution of the transmitted light and the reflected light output by the first polarization beam splitter (3); a second half-wave plate (9) is arranged between the pinhole aperture (8) and the second polarization beam splitter (10); the second half-wave plate (9) is used to adjust the polarization direction of the incident two-color laser and change the power distribution of the transmitted light and the reflected light output by the second polarization beam splitter (10); a third half-wave plate (12) is arranged before the third polarization beam splitter (13); the third half-wave plate (12) is used to adjust the polarization direction of the incident two-color laser and change the power distribution of the transmitted light and the reflected light output by the third polarization beam splitter (13).

8. The method according to claim 6, characterized in that The outer surface of the atomic chamber of the potassium atom Faraday laser is wrapped with a thermoelectric cooler for regulating the temperature inside the atomic chamber.

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