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

Abstract

The invention discloses an integrated cross-frequency-band reference source based on quantum frequency selection double-color laser and an implementation method. The integrated cross-frequency-band reference source 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. Two-color laser generated by the potassium atom Faraday laser is input into the first polarization beam splitter and then is divided into two beams, one beam is input into the atomic spectrum frequency stabilization system, and the other beam sequentially passes through the acousto-optic modulator and the small-hole diaphragm to enter the second polarization beam splitter; the second polarization beam splitter divides the incident light beam into two beams, one beam enters the third polarization beam splitter, and the other beam is input into the PDH frequency stabilization system; the atomic spectrum frequency stabilization system and the PDH frequency stabilization system are used for stabilizing the frequency of the double-color laser; the third polarization beam splitter divides the incident beam into two beams, one beam serves as an optical frequency signal to be output, the other beam is subjected to frequency down-conversion through an 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 a realization 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, and the frequency interval of its ±1st order sideband is exactly equal to 87 The ground state energy level interval of Rb is used to excite Rb atoms to produce CPT transitions; the highly stable, low-noise terahertz signal has a large bandwidth and strong directionality, which helps to improve the directionality and anti-interference ability of signal propagation and serve 5G and 6G high-speed communication systems; in addition, microwave, terahertz, and optical frequency reference sources also play an important role in high-resolution imaging. For example, synthetic aperture radar uses microwave imaging to penetrate clouds, rain and fog, and even image at night, and is widely used in surface coverage monitoring, topographic mapping, and disaster assessment; laser radar uses laser pulses for distance measurement, which can achieve high-precision three-dimensional imaging; the non-destructiveness of terahertz signals to biological tissues and their sensitivity to water molecules make them have good application potential in medical imaging fields such as skin cancer detection and tissue stratification.

[0003] There are many mechanisms for generating microwave, terahertz and optical frequency reference sources. Each method has its own advantages and limitations in performance with its unique characteristics. The main methods for generating microwave signals include: direct analog frequency synthesis method, which uses a harmonic generator to process a given reference signal to generate a series of harmonics, and then generates a large number of discrete frequencies through multiplication and division operations. This method has a simple implementation principle and low phase noise, but it is easy to have spurious components; phase-locked frequency synthesis method, which uses phase-locked loop (PLL) technology to multiply or divide the low-frequency signal to generate the required microwave frequency. This method can flexibly generate the required frequency by adjusting the division ratio and multiplication ratio, but the phase-locked loop will introduce additional phase noise; direct digital frequency synthesis method, first accumulates and stores the digital control word signal in the register, and then generates the required analog waveform signal through the sine lookup table through the Nyquist sampling theorem. This method has the advantages of high resolution and low power consumption, but it needs to be further improved in terms of phase noise and spurious. Terahertz reference sources are mainly generated by electronic devices 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 and it is difficult to cover wide-band terahertz frequencies. Free electron lasers use the movement of high-energy electron beams in a magnetic field to generate terahertz radiation, which has a large frequency band coverage, but the operating cost is relatively high. Photoconductive antennas that use ultrafast laser pulses to excite carriers in semiconductor materials can also generate terahertz radiation, but the power output is relatively limited. Optical frequency signal reference sources mainly include various types of lasers, light-emitting diodes, etc., which can usually only output optical frequency signals of a single band, and it is difficult to achieve high coherence and large frequency difference dual-wavelength optical frequency signal output.

[0004] In addition, the current microwave, terahertz, and optical frequency reference sources are independent of each other, and there is no integrated cross-band reference source that can cover the three frequency bands of microwave, terahertz, and optical frequency at the same time. In many application scenarios such as quantum state manipulation, modern high-speed communications, and sensing, it is often necessary to use signals of multiple different frequency bands at the same time. Therefore, different reference sources need to be used separately in practical applications, and each reference source requires an independent control and calibration mechanism, which significantly increases the complexity and volume of the system; in addition, independent reference sources may introduce phase noise and frequency drift, and there are problems such as synchronization between signals of different frequency bands. Summary of the invention

[0005] In order 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 expanded to cesium atom and rubidium atom Faraday laser), 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, combines the transmission characteristics of the potassium atom Faraday anomalous dispersion atomic filter at the D1 and D2 transition lines, and precisely controls the temperature and magnetic field strength of the potassium atom ensemble environment in the potassium atom Faraday anomalous dispersion atomic filter 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, wherein the corresponding wavelength of the D1 transition line of the potassium atom is 770nm, and the corresponding wavelength of the D2 transition line of the potassium atom is 767nm, and the frequency difference between the two is about 1.7THz, and further utilizes the cavity mode of the high-fineness ultra-stable resonant cavity and the cold atomic ensemble. The atomic spectrum is used as a frequency reference to narrow the line width of the two-color laser and optimize the short-term and long-term frequency stability of the two-color laser, thereby realizing an ultra-stable two-color optical frequency signal with a large frequency difference; because the two-color laser is generated by the same resonant cavity, the two have excellent coherence, and the terahertz signal generated by its beat frequency is free from the influence of 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 reflector 104. The potassium atom Faraday anomalous dispersion atomic filter 103 comprises a first Glan-Taylor prism 1031, a potassium atom gas chamber 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 atom gas chamber 1032 is filled with potassium of natural abundance;

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

[0010] The two-color laser is divided into two laser beams by the first half-wave plate 2 and the first polarization beam splitter 3, and then enters the atomic spectrum frequency stabilization system 6 after being reflected twice by the first reflector 4 and the second reflector 5. Then the atomic spectrum frequency stabilization system 6 outputs a servo signal to feed back to the current and cavity length control end of the potassium atom Faraday laser 1 to achieve the locking of the two-color laser frequency;

[0011] After the reflection path passes through the acousto-optic modulator 7, the 0th order and +1st order diffracted lights are obtained, wherein the 0th order light is blocked by the pinhole aperture 8, and the +1st order light passes through the pinhole aperture 8, and then is split into two paths by the second half-wave plate 9 and the second polarization beam splitter 10, and the reflection 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 the re-locking of the dual-color laser frequency;

[0012] The two-color laser 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 an output end of the optical frequency signal;

[0013] The two-color laser 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 high-stability microwave signal;

[0014] The two-color laser 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. The present invention utilizes the wide spectrum characteristics of the laser diode coated with an anti-reflection film and the unique transmission characteristics of the 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, thereby achieving the simultaneous output of two-color lasers with a large frequency difference in a single set of lasers, and the wavelengths automatically correspond to the D1 transition line and the D2 transition line of the potassium atom.

[0017] 2. The present invention utilizes the cavity mode of the ultrastable resonant cavity as a macroscopic frequency reference, which can effectively narrow the line width of the two-color laser and optimize the short-term frequency stability of the two-color laser; and 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 line width, and high frequency stability.

[0018] 3. The two-color laser realized by the present invention shares the same resonant cavity and therefore has a high coherence characteristic; furthermore, the terahertz signal generated by the two-color laser beat frequency exhibits high stability in frequency and is immune to the influence of laser resonant cavity drift jitter caused by external vibration and thermal noise.

[0019] 4. The present invention combines optical frequency division technology and uses an optical frequency comb as a large coefficient 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 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 associated with K D1 and D2 transition lines.

[0023] Figure 4 A 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-acoustic-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-anti-reflection film-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 in conjunction with the accompanying drawings and examples.

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

[0027] The 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, and its spectral range has 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, wherein the first Glan-Taylor prism 1031 converts the incident light beam after collimation 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 produce 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 in the figure), 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 will reflect a part of the light emitted from the potassium atom Faraday anomalous dispersion atomic filter back to the anti-reflection filmed laser diode 101 to form an optical resonant cavity, so as to realize the oscillation of the light beam between the rear end face of the anti-reflection filmed laser diode 101 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 two-color laser and are used to change the propagation direction of the two-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, so as 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 influence 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-precision ultra-stable resonant cavity, which uses the cavity mode of the resonant cavity to provide a macro frequency reference for comparing the difference between the dual-color laser frequency and the cavity mode frequency, and generates a servo signal to feed back to the control end of the acousto-optic modulator 7 to achieve secondary locking of the dual-color laser frequency, thereby narrowing the line width 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 lower frequency. 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 , thereby achieving high-precision transmission from optical frequency to microwave frequency, and outputting two frequencies respectively f b1 and f b2 of microwave signals.

[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 lasers with wavelengths of 770nm and 767nm, and its frequency depends on the difference frequency between the 770nm and 767nm two-color lasers, which is about 1.4THz; the actual frequency value can be changed 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, and 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 protection scope of the present invention; for ordinary technicians in this technical field, without departing from the technical principles of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope 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 be divided into two beams, one beam is input into the atomic spectrum frequency stabilization system (6), and the other beam is 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) contains 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 two-color laser to generate multi-order diffraction light, and to perform compensation control on the frequency of the two-color laser by receiving a servo signal from a 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, 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 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 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, characterized in that: 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 light, thereby changing 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 gas chamber of the potassium atom Faraday laser is wrapped with a thermoelectric cooler for regulating the temperature inside the atomic gas chamber.

6. A method for realizing an integrated cross-band reference source based on quantum frequency-selective two-color laser, the steps of which include: 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) to split the two-color laser into two beams, one of which is input into the atomic spectrum frequency stabilization system (6), and the other is sequentially incident on the second polarization beam splitter (10) via 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 to feed back the servo signal to the potassium atom Faraday laser. The current and cavity length control end of the laser (1) optimizes 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 two-color laser to generate multi-order diffraction light, and compensates 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 through; 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 it and the received two-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, and the other beam is frequency-down-converted by the optical frequency comb system (14) to output a microwave signal, and the remaining two-color laser signal is input into the terahertz detector (15); 4) The terahertz detector (15) mixes 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 two-color laser light which is input into the first polarization beam splitter (3) through the 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, 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 light, 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 light, 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 gas chamber of the potassium atom Faraday laser is wrapped with a thermoelectric cooler for regulating the temperature inside the atomic gas chamber.

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