EIT phase noise spectrum-based laser frequency stabilization property evaluation system and method

Abstract

The invention relates to the technical field of laser frequency stabilization, and discloses a laser frequency stabilization property evaluation system and method based on an EIT phase noise spectrum. The system comprises a detection light frequency stabilization unit, a first coupling light frequency stabilization unit, a second coupling light frequency stabilization unit, a first EIT spectrum unit, a second EIT spectrum unit, a third EIT spectrum unit, a first coupling light phase discrimination feedback unit, a second coupling light phase discrimination feedback unit, a first noise evaluation unit, a second noise evaluation unit and a third noise evaluation unit. According to the invention, accurate evaluation of the frequency stabilization property of the coupled laser is realized by using the EIT phase noise spectrum through frequency fluctuation under various frequency stabilization methods.

Description

Technical Field

[0001] The present invention relates to the technical field of laser frequency stabilization, and in particular to a system and method for evaluating the frequency stabilization property of a laser based on an EIT phase noise spectrum. Background Art

[0002] Rydberg atoms are atoms whose outermost electrons are excited to a highly excited state (generally, the principal quantum number n≥15). Rydberg atoms have many unique properties compared to ground-state atoms: their radiation lifetime is proportional to n3, their electric dipole moment is proportional to n4, their polarizability is proportional to n7, etc. These properties make Rydberg atoms an excellent physical platform for studying quantum storage, quantum computing, quantum precision measurement, and other fields.

[0003] Three-level step electromagnetically induced transparency (EIT) is the most widely used method for Rydberg atom detection. A weak probe light excites the alkali metal atoms from the ground state to the intermediate state. At the same time, a strong coupling light excites the atoms from the intermediate state to the required Rydberg state. Locking the laser frequency to the corresponding atomic transition energy level is crucial to achieve precise measurement of Rydberg atoms. In the existing EIT spectral coupled laser frequency stabilization, the methods that can be used include modulation and demodulation, modulation transfer spectroscopy (MTS), and two-color polarization spectroscopy. The first two methods inevitably bring phase noise to the frequency stabilization module.

[0004] The phase noise of the detection field and the coupling field in the EIT medium can be converted into the intensity noise of the detection field. Therefore, the phase noise introduced by the frequency stabilization module will affect the signal-to-noise ratio of the EIT spectrum of the measurement module, thereby affecting the measurement accuracy. However, the existing frequency stabilization evaluation method only evaluates the frequency fluctuations in the time domain and frequency domain under different coupling laser frequency stabilization methods, ignoring whether various coupling laser frequency stabilization methods will introduce noise to the EIT spectrum of the measurement module. Summary of the invention

[0005] In order to solve the above technical problems, the present invention proposes a system and method for evaluating the frequency stabilization properties of a laser based on the EIT phase noise spectrum. The frequency stabilization properties of the laser are evaluated while fully considering various frequency locking methods to improve the accuracy of the evaluation of the frequency stabilization properties of the laser.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is: a laser frequency stabilization property evaluation system based on EIT phase noise spectrum, including a detection light frequency stabilization unit, a first coupled light frequency stabilization unit, a second coupled light frequency stabilization unit, a first EIT spectrum unit, a second EIT spectrum unit, a third EIT spectrum unit, a first coupled light phase discrimination feedback unit, a second coupled light phase discrimination feedback unit, a first noise evaluation unit, a second noise evaluation unit, and a third noise evaluation unit; the first EIT spectrum unit and the first coupled light phase discrimination feedback unit form a first coupled light frequency stabilization unit, and the second EIT spectrum unit and the second coupled light phase discrimination feedback unit form a second coupled light frequency stabilization unit;

[0007] The light output by the detection laser generating device is divided into three beams after passing through the detection light beam splitting unit, one beam is stabilized by the detection light frequency stabilization unit, another beam is sent to the first EIT spectrum unit or the second EIT spectrum unit, and the third beam is sent to the third EIT spectrum unit;

[0008] The light outputted by the coupling laser generating device is divided into two beams after passing through the coupling light beam splitting unit, one beam is sent to the third EIT spectrum unit, and the other beam is sent to the first EIT spectrum unit or the second EIT spectrum unit;

[0009] The third EIT spectrum unit is used to generate an EIT spectrum and send it to the third noise evaluation unit; the first EIT spectrum unit and the second EIT spectrum unit are respectively used to generate EIT spectra, and the generated EIT spectra are divided into two parts, one part of which is sent to the first noise evaluation unit or the second noise evaluation unit, and the other part is locked to the light output by the coupled laser generating device after passing through the first coupling optical phase-discrimination feedback unit or the second coupling optical phase-discrimination feedback unit.

[0010] The first coupling light frequency stabilization unit is a modulation and demodulation frequency stabilization unit, and the second coupling light frequency stabilization unit is a modulation transfer spectrum frequency stabilization unit.

[0011] In the first coupling light frequency stabilization unit, a phase-locked amplifier outputs a sinusoidal signal which is added to the piezoelectric ceramic voltage of the coupling laser generating device as a modulation signal; the detection laser is divided into two beams and then incident on the atomic gas chamber in the same direction, the coupling laser and one of the detection laser beams overlap in the opposite direction in the atomic gas chamber, the two detection laser beams are detected by a first balanced photodetector (21), and then a part of the electrical signal obtained by the first balanced photodetector (21) is input into the phase-locked amplifier for demodulation to generate a differential error signal, and then the differential error signal is input into the PI circuit, and the piezoelectric ceramic voltage of the coupling laser generating device is fed back to the PI controller to lock it, and the other part of the electrical signal is sent to the first noise evaluation unit;

[0012] In the second coupled light frequency stabilization unit, the detection laser is divided into two beams and then incident on the atomic gas chamber in the same direction. The frequency stabilization coupling laser is phase modulated by an electro-optic modulator and then overlapped with a beam of detection laser in the atomic gas chamber in the opposite direction. The unmodulated detection light generates a four-wave mixing effect in the nonlinear medium to generate a sideband of the detection light, and then the sideband of the coupling light is transferred to the detection light. The two detection laser beams are detected by a second balanced photodetector (31) to obtain a beat frequency signal of the detection light and its sideband. A part of the electrical signal obtained by the first balanced photodetector (21) is input into the mixer and the modulation signal of the electro-optic modulator for demodulation and filtering to obtain a modulation transfer spectrum signal. Then, the modulation transfer spectrum signal is fed back to the piezoelectric ceramic voltage of the coupling laser generating device through a PI controller to lock it, and the other part of the electrical signal is sent to the second noise evaluation unit.

[0013] The first noise evaluation unit and the second noise evaluation unit are spectrum analyzers.

[0014] The detection laser frequency stabilization unit is a saturation absorption spectrum frequency stabilization unit.

[0015] The first noise evaluation unit, the second noise evaluation unit and the third noise evaluation unit perform EIT spectrum noise evaluation using a phase noise spectrum technology that converts phase noise into intensity noise.

[0016] In addition, the present invention also provides a method for evaluating the frequency stabilization properties of a laser based on an EIT phase noise spectrum, which is implemented based on the system for evaluating the frequency stabilization properties of a laser based on an EIT phase noise spectrum, and includes the following steps:

[0017] Step 1: Send the light output by the detection laser generating device to the first EIT spectrum unit, and at the same time, send the light output by the coupling laser generating device to the first EIT spectrum unit;

[0018] Step 2: Using the spectrum output by the first EIT spectrum unit, the first coupled optical phase-discrimination feedback unit generates a feedback signal to frequency-lock the coupled laser generating device, and at the same time, the first noise evaluation unit and the third noise evaluation unit are used to respectively obtain the laser phase noise spectrum; and whether phase noise is introduced in the frequency stabilization process is determined according to the obtained laser phase noise spectrum;

[0019] Step 3: Send the light output by the detection laser generating device to the second EIT spectrum unit, and at the same time, send the light output by the coupling laser generating device to the second EIT spectrum unit;

[0020] Step 4: Using the spectrum output by the second EIT spectrum unit, the second coupled optical phase-discrimination feedback unit generates a feedback signal to frequency-lock the coupled laser generating device, and at the same time, the second noise evaluation unit and the third noise evaluation unit are used to obtain the laser phase noise respectively; according to the obtained laser phase noise spectrum, it is determined whether the frequency stabilization process introduces phase noise;

[0021] Step 5: Based on the results of steps 2 and 4, comprehensively evaluate the frequency stabilization properties of the coupled light generating device.

[0022] In step 2 and step 4, the setting parameters of the third noise evaluation unit are the same.

[0023] Compared with the prior art, the present invention has the following beneficial effects: the present invention provides a system and method for evaluating the frequency stabilization properties of a laser based on an EIT phase noise spectrum, wherein a signal generated by a first EIT spectrum unit is connected to a first noise evaluation unit under a modulation and demodulation frequency stabilization unit, and a signal generated by a third EIT spectrum unit is connected to a third noise evaluation unit; and a signal generated by a second EIT spectrum unit is connected to a second noise evaluation unit under a modulation transfer spectrum frequency stabilization unit, and a signal generated by a third EIT spectrum unit is connected to a third noise evaluation unit, and an accurate evaluation of the frequency stabilization properties of a coupled laser is achieved by using the EIT phase noise spectrum through frequency fluctuations under various frequency stabilization methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A schematic diagram of the structure of a device used in a method for evaluating the frequency stabilization properties of a laser based on an EIT phase noise spectrum provided in an embodiment of the present invention;

[0025] Figure 2 One of the coupled laser frequency stabilization units provided in the embodiment of the present invention: a schematic diagram of the structure of the modulation and demodulation frequency stabilization unit; wherein the dotted line frame is a schematic diagram of the structure of the third EIT spectrum unit;

[0026] Figure 3 Another coupled laser frequency stabilization unit provided in an embodiment of the present invention: a schematic diagram of the structure of a modulation transfer spectrum frequency stabilization unit; wherein the dotted line frame is a schematic diagram of the structure of a third EIT spectrum unit;

[0027] Figure 4 A phase noise analysis diagram obtained by zero-sweep frequency detection of the first noise evaluation unit and the third noise evaluation unit under the modulation and demodulation unit provided in an embodiment of the present invention;

[0028] Figure 5 Phase noise analysis diagram obtained by zero-sweep frequency detection of the second noise evaluation unit and the third noise evaluation unit under the MTS unit provided in the embodiment of the present invention;

[0029] Figure 6The phase noise of the first EIT spectrum unit and the third EIT spectrum unit under the modulation and demodulation unit provided in the embodiment of the present invention varies with the modulation amplitude;

[0030] Figure 7 The second EIT spectrum unit phase noise provided by the embodiment of the present invention varies with the modulation amplitude. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0032] Embodiment 1

[0033] like Figure 1 As shown, an embodiment of the present invention provides a laser frequency stabilization property evaluation system based on EIT phase noise spectrum, including a detection light frequency stabilization unit, a first coupled light frequency stabilization unit, a second coupled light frequency stabilization unit, a first EIT spectrum unit, a second EIT spectrum unit, a third EIT spectrum unit, a first coupled light phase-discrimination feedback unit, a second coupled light phase-discrimination feedback unit, a first noise evaluation unit, a second noise evaluation unit, and a third noise evaluation unit; the first EIT spectrum unit and the first coupled light phase-discrimination feedback unit form a first coupled light frequency stabilization unit, and the second EIT spectrum unit and the second coupled light phase-discrimination feedback unit form a second coupled light frequency stabilization unit.

[0034] In this embodiment, the 852nm laser output by the detection laser generating device is divided into three beams after passing through the detection light beam splitting unit, one beam is stabilized for the detection laser generating device by the detection light frequency stabilization unit, the other beam is sent to the first EIT spectrum unit or the second EIT spectrum unit, and the third beam is sent to the third EIT spectrum unit; the 509nm laser output by the coupling laser generating device is divided into two beams after passing through the coupling light beam splitting unit, one beam is sent to the third EIT spectrum unit, and the other beam is sent to the first EIT spectrum unit or the second EIT spectrum unit; the third EIT spectrum unit is used to generate an EIT spectrum and send it to the third noise evaluation unit; the first EIT spectrum unit and the second EIT spectrum unit are respectively used to generate EIT spectra, and the generated EIT spectra are divided into two parts, one part of which is sent to the first noise evaluation unit or the second noise evaluation unit, and the other part is locked to the light output by the coupling laser generating device after passing through the first coupling light phase-discrimination feedback unit or the second coupling light phase-discrimination feedback unit.

[0035] Specifically, in this embodiment, the detection light output by the detection laser generating device 111 is divided into three paths after passing through the detection light beam splitting unit 112: path 1121 passes through the detection light frequency stabilization unit 113 to perform detection light frequency stabilization through saturated absorption spectrum; path 1122 enters the first / second EIT spectrum unit 126; path 1123 enters the third EIT spectrum unit 123. The coupled laser generating device 121 is divided into two paths after passing through the coupled optical beam splitting unit 122: path 1221 enters the first / second EIT spectrum unit 126, and after both paths 1122 and 1221 enter the first / second EIT spectrum unit 126, the first / second EIT spectrum unit 126 is connected to a balanced photodetector and then divided into two paths, path 1271 is connected to the first / second coupled optical phase-discrimination feedback unit 129 to achieve frequency stabilization of the coupled laser; path 1272 is connected to the first / second noise evaluation unit 128; path 1222 enters the third EIT spectrum unit 123, and after both paths 1123 and 1222 enter the third EIT spectrum unit 123, the unit is connected to the third noise evaluation unit 125.

[0036] Furthermore, in this embodiment, the first coupling light frequency stabilization unit is a modulation and demodulation frequency stabilization unit, and the second coupling light frequency stabilization unit is a modulation transfer spectrum frequency stabilization unit.

[0037] like Figure 2 As shown, the first coupling light frequency stabilization unit of this embodiment is a modulation and demodulation frequency stabilization unit, and the coupling laser generating device is divided into two beams after passing through the coupling light beam splitting device composed of a half-wave plate and a polarization beam splitting prism, one beam is sent to the third EIT spectrum unit, and the other beam is used as a coupling laser for frequency stabilization. Furthermore, changing the angle between the fast axis or slow axis of the half-wave plate and the polarization direction of the coupling laser can realize the control of the light intensity of the coupling laser with a wavelength of 509nm.

[0038] like Figure 3 As shown, in this embodiment, the phase-locked amplifier outputs a sinusoidal signal with a frequency of 52.5kHz and an amplitude of 0.004V, which is added to the piezoelectric ceramic voltage of the coupling laser generating device 121 as a modulation signal; the detection laser is divided into two beams and then incident on the atomic gas chamber in the same direction, and the coupling laser and one of the detection laser beams overlap in the opposite direction in the atomic gas chamber, and the two detection laser beams are detected by the first balanced photodetector 21, and then a part of the electrical signal obtained by the first balanced photodetector 21 is input into the phase-locked amplifier for demodulation to generate a differential error signal, and then the differential error signal is input into the PI circuit after passing through the low-pass filter LPF, and is fed back to the piezoelectric ceramic voltage of the coupling laser generating device through the PI controller to lock it, and the other part of the electrical signal is sent to the first noise evaluation unit.

[0039] Figure 2In the figure, the third EIT spectrum unit is shown in the dotted box, which includes an atomic gas chamber and a third balanced photodetector 33. In the third EIT spectrum unit, the detection laser is divided into two beams, one of which overlaps with the coupling laser in the atomic gas chamber in reverse, and the other directly passes through the atomic gas chamber. The two detection lights are sent to the third noise evaluation unit after the EIT spectrum is obtained by the third balanced photodetector 33.

[0040] like Figure 3 As shown, the second coupling light frequency stabilization unit of this embodiment is a modulation transfer spectrum frequency stabilization unit. Specifically, the coupling laser generating device 121 is divided into two beams after passing through the coupling light beam splitting device composed of a half-wave plate and a polarization beam splitting prism. One beam is sent to the third EIT spectrum unit to generate an EIT spectrum together with the detection light, and the other beam is used as a coupling laser for frequency stabilization. Furthermore, changing the angle between the fast axis or slow axis of the half-wave plate and the polarization direction of the coupling laser can achieve the control of the light intensity of the coupling laser with a wavelength of 509nm.

[0041] like Figure 3 As shown, in the second coupled light frequency stabilization unit, the detection laser is divided into two beams and then incident on the atomic gas chamber in the same direction. The frequency stabilization coupling laser is phase modulated by an electro-optic modulator driven by a modulation signal with a frequency of 10.3MHz and an amplitude of 1.0V, and then overlaps with a beam of detection laser in the atomic gas chamber in the opposite direction. The unmodulated detection light undergoes a four-wave mixing effect in the nonlinear medium to generate a sideband of the detection light, and then the sideband of the coupling light is transferred to the detection light. The two detection laser beams are detected by the second balanced photodetector 31 to obtain the beat frequency signal of the detection light and its sideband. A part of the electrical signal obtained by the first balanced photodetector 21 is input into the mixer and the modulation signal of the electro-optic modulator for demodulation and filtering to obtain a modulation transfer spectrum signal; then the modulation transfer spectrum signal is converted into a frequency discrimination signal through a low-pass filter LPF and a PI controller, and then fed back to the piezoelectric ceramic voltage of the coupling laser generating device to lock it, and the other part of the electrical signal is sent to the second noise evaluation unit.

[0042] Figure 3 In the figure, the dotted frame shows a third EIT spectrum unit, which includes an atomic gas chamber and a third balanced photodetector 23.

[0043] Specifically, in this embodiment, the first noise evaluation unit, the second noise evaluation unit and the third noise evaluation unit are all spectrum analyzers SA.

[0044] Specifically, in this embodiment, the detection laser frequency stabilization unit is a saturated absorption spectrum frequency stabilization unit.

[0045] Specifically, in this embodiment, the first noise evaluation unit, the second noise evaluation unit, and the third noise evaluation unit perform EIT spectrum noise evaluation using a phase noise spectrum technology that converts phase noise into intensity noise.

[0046] Embodiment 2

[0047] Embodiment 2 of the present invention provides a method for evaluating the frequency stabilization properties of a laser based on an EIT phase noise spectrum, which is implemented based on a system for evaluating the frequency stabilization properties of a laser based on an EIT phase noise spectrum described in Embodiment 1, and includes the following steps:

[0048] Step 1: Send the light output by the detection laser generating device to the first EIT spectrum unit, and at the same time, send the light output by the coupling laser generating device to the first EIT spectrum unit.

[0049] Step 2: Using the spectrum output by the first EIT spectrum unit, the first coupled optical phase-discrimination feedback unit generates a feedback signal to frequency-lock the coupled laser generating device. At the same time, the first noise evaluation unit and the third noise evaluation unit are used to obtain the laser phase noise spectrum respectively; based on the obtained laser phase noise spectrum, it is determined whether phase noise is introduced in the frequency stabilization process.

[0050] In this embodiment, the phase-locked amplifier of the first coupling light phase-detection feedback unit undertakes the modulation and demodulation tasks, generates a phase-detection signal of the coupling laser, and feeds back the phase-detection signal voltage of the detection coupling light to the coupling laser generating device in real time to achieve frequency stabilization of the coupling laser.

[0051] Step 3: Send the light output by the detection laser generating device to the second EIT spectrum unit, and at the same time, send the light output by the coupling laser generating device to the second EIT spectrum unit;

[0052] Step 4: Using the spectrum output by the second EIT spectrum unit, the second coupled optical phase-discrimination feedback unit generates a feedback signal to lock the frequency of the coupled laser generating device. At the same time, the second noise evaluation unit and the third noise evaluation unit are used to obtain the laser phase noise respectively; according to the obtained laser phase noise spectrum, it is determined whether the frequency stabilization process introduces phase noise.

[0053] In the second coupled light phase-discrimination feedback unit of this embodiment, the modulated detection light is mixed with the modulation signal to generate a phase-discrimination signal of the coupled laser, and the phase-discrimination signal voltage of the coupled light is fed back to the coupled laser generating device in real time to achieve frequency stabilization of the coupled laser;

[0054] Step 5: Based on the results of steps 2 and 4, comprehensively evaluate the frequency stabilization properties of the coupled light generating device.

[0055] In step 2 and step 4, the setting parameters of the third noise evaluation unit are the same.

[0056] Specifically, the step 2 also includes the step of changing the modulation amplitude of the phase-locked amplifier and repeating the measurement; the step 4 also includes the step of changing the modulation amplitude applied to the acousto-optic modulator EOM and repeating the measurement. When performing the above noise evaluation, the spectrum analyzer is set to zero sweep detection,

[0057] like Figure 4 As shown, it is a laser phase noise analysis diagram obtained by zero-sweep detection of the first noise evaluation unit and the third noise evaluation unit under the modulation and demodulation unit. Specifically, the balanced photodetector 21 is connected to the spectrum analyzer 22, and the balanced photodetector 23 is connected to the spectrum analyzer 24. The center frequency is set to 52.5kHz, the video bandwidth is 5.1Hz, the resolution bandwidth is 5.1Hz, and the sweep width is 0Hz. The black line is the measurement result of the first noise evaluation unit, and the blue line is the measurement result of the third noise evaluation unit. It can be seen that both curves are M-shaped. According to the EIT phase noise spectrum method, that is to say, there is a conversion of phase noise to detection field intensity noise in both the frequency stabilization module and the measurement module. The measurement module, that is, the third EIT spectrum unit, introduces phase noise to the EIT spectrum due to the modulation and demodulation frequency stabilization method.

[0058] like Figure 5 As shown, it is a laser phase noise analysis diagram obtained by zero-sweep detection of the second noise evaluation unit and the third noise evaluation unit under the MTS unit. Specifically, the balanced photodetector 31 is connected to the spectrum analyzer 32, and the balanced photodetector 33 is connected to the spectrum analyzer 34. The center frequency is set to 10.3MHz, the video bandwidth is 10Hz, the resolution bandwidth is 100Hz, and the sweep width is 0Hz. The black line is the measurement result of the second noise evaluation unit, and the blue line is the measurement result of the third noise evaluation unit. It can be seen that only the black curve is M-shaped. According to the EIT phase noise spectrum method, that is to say, only the frequency stabilization module has the conversion of phase noise to detection field intensity noise, and the measurement module, that is, the third EIT spectrum unit, does not introduce phase noise to the EIT spectrum due to the MTS frequency stabilization method.

[0059] like Figure 6 As shown, the phase noise of the first EIT spectrum unit and the third EIT spectrum unit under modulation and demodulation varies with the modulation amplitude. Specifically, the first EIT spectrum unit is shown as a black dot, and the third EIT spectrum unit is shown as a blue dot. The modulation amplitude of the phase-locked amplifier is changed, and the zero-sweep detection of the first and third noise evaluation units is repeated, and the average value of the maximum phase noise is taken as the evaluation point.

[0060] like Figure 7Specifically, the EOM modulation amplitude is changed, the second noise evaluation unit zero sweep detection is repeated, and the average value of the phase noise maximum value is taken as the evaluation point.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A laser frequency stabilization property evaluation system based on EIT phase noise spectrum, characterized in that: It includes a detection light frequency stabilization unit, a first coupling light frequency stabilization unit, a second coupling light frequency stabilization unit, a first EIT spectrum unit, a second EIT spectrum unit, a third EIT spectrum unit, a first coupling light phase discrimination feedback unit, a second coupling light phase discrimination feedback unit, a first noise evaluation unit, a second noise evaluation unit, and a third noise evaluation unit; the first EIT spectrum unit and the first coupling light phase discrimination feedback unit form a first coupling light frequency stabilization unit, and the second EIT spectrum unit and the second coupling light phase discrimination feedback unit form a second coupling light frequency stabilization unit; The light output by the detection laser generating device is divided into three beams after passing through the detection light beam splitting unit, one beam is stabilized by the detection light frequency stabilization unit, another beam is sent to the first EIT spectrum unit or the second EIT spectrum unit, and the third beam is sent to the third EIT spectrum unit; The light outputted by the coupling laser generating device is divided into two beams after passing through the coupling light beam splitting unit, one beam is sent to the third EIT spectrum unit, and the other beam is sent to the first EIT spectrum unit or the second EIT spectrum unit; The third EIT spectrum unit is used to generate an EIT spectrum and send it to the third noise evaluation unit; the first EIT spectrum unit and the second EIT spectrum unit are respectively used to generate EIT spectra, and the generated EIT spectra are divided into two parts, one part of which is sent to the first noise evaluation unit or the second noise evaluation unit, and the other part is locked to the light output by the coupled laser generating device after passing through the first coupling optical phase-discrimination feedback unit or the second coupling optical phase-discrimination feedback unit.

2. The laser frequency stabilization property evaluation system based on EIT phase noise spectrum according to claim 1, characterized in that: The first coupling light frequency stabilization unit is a modulation and demodulation frequency stabilization unit, and the second coupling light frequency stabilization unit is a modulation transfer spectrum frequency stabilization unit.

3. The laser frequency stabilization property evaluation system based on EIT phase noise spectrum according to claim 1, characterized in that: In the first coupling light frequency stabilization unit, a phase-locked amplifier outputs a sinusoidal signal which is added to the piezoelectric ceramic voltage of the coupling laser generating device as a modulation signal; the detection laser is divided into two beams and then incident on the atomic gas chamber in the same direction, the coupling laser and one of the detection laser beams overlap in the opposite direction in the atomic gas chamber, the two detection laser beams are detected by a first balanced photodetector (21), and then a part of the electrical signal obtained by the first balanced photodetector (21) is input into the phase-locked amplifier for demodulation to generate a differential error signal, and then the differential error signal is input into the PI circuit, and the piezoelectric ceramic voltage of the coupling laser generating device is fed back to the PI controller to lock it, and the other part of the electrical signal is sent to the first noise evaluation unit; In the second coupled light frequency stabilization unit, the detection laser is divided into two beams and then incident on the atomic gas chamber in the same direction. The frequency stabilization coupling laser is phase modulated by an electro-optic modulator and then overlapped with a beam of detection laser in the atomic gas chamber in the opposite direction. The unmodulated detection light generates a four-wave mixing effect in the nonlinear medium to generate a sideband of the detection light, and then the sideband of the coupling light is transferred to the detection light. The two detection laser beams are detected by a second balanced photodetector (31) to obtain a beat frequency signal of the detection light and its sideband. A part of the electrical signal obtained by the first balanced photodetector (21) is input into the mixer and the modulation signal of the electro-optic modulator for demodulation and filtering to obtain a modulation transfer spectrum signal. Then, the modulation transfer spectrum signal is fed back to the piezoelectric ceramic voltage of the coupling laser generating device through a PI controller to lock it, and the other part of the electrical signal is sent to the second noise evaluation unit.

4. The laser frequency stabilization property evaluation system based on EIT phase noise spectrum according to claim 1, characterized in that: The first noise evaluation unit and the second noise evaluation unit are spectrum analyzers.

5. The laser frequency stabilization property evaluation system based on EIT phase noise spectrum according to claim 1, characterized in that: The detection laser frequency stabilization unit is a saturation absorption spectrum frequency stabilization unit.

6. The laser frequency stabilization property evaluation system based on EIT phase noise spectrum according to claim 1, characterized in that: The first noise evaluation unit, the second noise evaluation unit and the third noise evaluation unit perform EIT spectrum noise evaluation using a phase noise spectrum technology that converts phase noise into intensity noise.

7. A method for evaluating the frequency stabilization properties of a laser based on an EIT phase noise spectrum, implemented based on a system for evaluating the frequency stabilization properties of a laser based on an EIT phase noise spectrum as claimed in any one of claims 1 to 4, characterized in that: The following steps are involved: Step 1: Send the light output by the detection laser generating device to the first EIT spectrum unit, and at the same time, send the light output by the coupling laser generating device to the first EIT spectrum unit; Step 2: Using the spectrum output by the first EIT spectrum unit, the first coupled optical phase-discrimination feedback unit generates a feedback signal to frequency-lock the coupled laser generating device, and at the same time, the first noise evaluation unit and the third noise evaluation unit are used to respectively obtain the laser phase noise spectrum; and whether phase noise is introduced in the frequency stabilization process is determined according to the obtained laser phase noise spectrum; Step 3: Send the light output by the detection laser generating device to the second EIT spectrum unit, and at the same time, send the light output by the coupling laser generating device to the second EIT spectrum unit; Step 4: Using the spectrum output by the second EIT spectrum unit, the second coupled optical phase-discrimination feedback unit generates a feedback signal to frequency-lock the coupled laser generating device, and at the same time, the second noise evaluation unit and the third noise evaluation unit are used to obtain the laser phase noise respectively; according to the obtained laser phase noise spectrum, it is determined whether the frequency stabilization process introduces phase noise; Step 5: Based on the results of steps 2 and 4, comprehensively evaluate the frequency stabilization properties of the coupled light generating device.

8. The method for evaluating the frequency stabilization properties of a laser based on the EIT phase noise spectrum according to claim 7, characterized in that: In step 2 and step 4, the setting parameters of the third noise evaluation unit are the same.

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