Tunable laser absolute frequency calibration system

Abstract

The utility model discloses an absolute frequency calibration system for a tunable laser. The absolute frequency calibration system comprises an atomic vapor saturated absorption spectrum measurement module, a signal acquisition module and a data analysis module, the atomic vapor saturated absorption spectrum measurement module receives laser output by the target tunable laser for atomic vapor saturated absorption spectrum measurement and outputs a signal; the signal acquisition module acquires an output signal of the atom vapor saturated absorption spectrum measurement module and transmits the output signal to the data analysis module, the data analysis module analyzes the output signal to obtain an atom saturated absorption wavelength, and then the atom saturated absorption wavelength is processed to obtain a frequency signal of the target tunable laser. According to the absolute frequency calibration system for the tunable laser, the atomic vapor saturated absorption spectrum of the laser output by the tunable laser is measured through the atomic vapor saturated absorption spectrum measurement module for absolute frequency calibration, the frequency precision is high, and the system structure is simple.

Description

Technical Field

[0001] The invention belongs to the technical field of lasers, and in particular relates to a method for calibrating the absolute frequency of a tunable laser, and also relates to a system for calibrating the absolute frequency of a tunable laser. Background Art

[0002] Tunable lasers can output narrow-linewidth lasers whose frequency changes continuously over time. This feature can be used to make tunable laser spectrometers. The resolution of tunable laser spectrometers is much higher than that of grating spectrometers, and they play an important role in the field of precision measurement.

[0003] In the specific implementation of the tunable laser spectrometer, a tunable laser is input into the device to be detected. When the frequency of the laser is tuned over time, the transmission or reflection signal of the detected device will change over time. This time-varying signal reflects the frequency-related response of the device, that is, the transmission or reflection spectrum of the device. The key to converting the time-varying signal into a spectrum is to calibrate the output frequency of the tunable laser. In relative frequency calibration, the use of devices such as fiber unequal-arm interferometers can increase the relative frequency of the laser to the MHz level. However, for absolute frequency calibration, a high-precision and low-cost solution is still needed.

[0004] The current mainstream solution is to use a narrow linewidth fiber laser as a frequency standard laser for absolute frequency calibration. By detecting the beat frequency signal between the tunable laser and the frequency standard laser, the absolute frequency of the tunable laser can be obtained. The frequency of the frequency standard laser needs to be measured by the wavelength meter in the system. The frequency accuracy of the common commercial wavelength meter is 200MHz, which is relatively low. In addition, this solution requires the introduction of a narrow linewidth fiber laser, which makes the system complex, costly, and large in size.

[0005] The present invention uses the saturated absorption spectrum of atomic vapor to calibrate the absolute frequency of a tunable laser, and has high frequency accuracy. The system does not need to introduce an additional laser, and the system is simple, low-cost, and compact. Summary of the invention

[0006] The first object of the present invention is to provide a method for calibrating absolute frequency of a tunable laser, so as to solve the problem of low precision of the method for calibrating absolute frequency of a tunable laser in the prior art.

[0007] A second object of the present invention is to provide a tunable laser absolute frequency calibration system.

[0008] To achieve the above object, the present invention adopts the following technical solutions:

[0009] A method for calibrating absolute frequency of a tunable laser comprises the following steps:

[0010] S1, selecting an element whose saturation absorption wavelength is within the frequency tuning range of the target tunable laser;

[0011] S2, allowing the laser output by the tunable laser to pass through the atomic vapor cell containing the element to excite the atoms and cause saturation absorption, and collecting the output signal of the atomic vapor cell after the atomic vapor is saturatedly absorbed;

[0012] S3, performing data analysis on the output signal to obtain a frequency signal of the tunable laser;

[0013] S4. Calibrate the absolute frequency of the tunable laser using the frequency signal.

[0014] In the present invention, the element includes one of Mg, Se, Ir, B, Sb, Bi, Be, V, Cu, Ag, Na, Lu, Pd, Ni, Rh, Re, Ba, Tl, Hf, Fe, Mo, Co, Sc, Ru, Al, Yb, Ti, Er, Mn, Mn, Ga, La, U, Gd, Nd, W, Nb, In, Y, Ho, Tm, Dy, Ca, Cr, Os, Tb, Eu, Sr, Zr, Sm, Li, K, Rb, and Cs.

[0015] Since the saturation absorption wavelength of atomic vapor is mainly concentrated in the visible light band, it is impossible to complete the relative frequency calibration of the tunable laser in the infrared band. In order to solve this technical problem, in the present invention, when the tuning frequency of the tunable laser is in the infrared band, the output wavelength of the tunable laser is frequency-doubled, and the wavelength is converted to the visible light range and then enters the atomic vapor chamber for saturation absorption.

[0016] The present invention processes the output wavelength of the tunable laser in different ways according to the different tuning frequencies of the tunable laser. Specifically, S1 also includes: S11, judging the tuning frequency range of the tunable laser; when the tuning frequency is in the ultraviolet and visible light bands, executing S2; when the tuning frequency is in the infrared band, performing frequency doubling processing on the output wavelength of the tunable laser, and then executing S2.

[0017] In the present invention, S3 comprises the following steps:

[0018] S31, obtaining the atomic saturation absorption wavelength according to the output signal of the atomic vapor saturation absorption;

[0019] S32. Obtaining a frequency signal of the tunable laser according to the relationship between the atomic saturation absorption wavelength and the output wavelength of the tunable laser.

[0020] Furthermore, the specific process of S31 is as follows: according to the output signal of the atomic vapor saturated absorption spectrum measurement module, the atomic absorption spectrum signal with Doppler broadening at the signal extreme value is found, and compared with the shape of the saturated absorption spectrum, the saturated absorption peak is found, and the wavelength corresponding to the saturated absorption peak is obtained, which is the atomic saturated absorption wavelength.

[0021] Furthermore, the atomic saturation absorption wavelength is obtained by linearly fitting the wavelengths corresponding to the multiple saturation absorption peaks and the time t corresponding to the saturation absorption peaks.

[0022] Furthermore, the frequency signal of the tunable laser in S3 is the output frequency of the tunable laser.

[0023] In the present invention, the atomic vapor saturation absorption spectrum measurement module comprises a spectroscopic prism, an atomic vapor chamber, a reflector and a photoelectric detector; the atomic vapor chamber is arranged between the spectroscopic prism and the reflector;

[0024] The spectroscopic prism is used to receive the laser light emitted by the tunable laser and perform spectroscopic processing; the atomic vapor chamber is used to allow the laser light processed by the spectroscopic prism to pass through; the reflector is used to receive the laser light passing through the atomic vapor chamber and reflect it to pass through the atomic vapor chamber in the opposite direction; the photoelectric detector is used to receive the laser light passing through the atomic vapor chamber in the reverse direction and perform photoelectric signal conversion.

[0025] In the present invention, the atomic vapor saturation absorption spectrum measurement module further includes an optical isolator, and the optical isolator is arranged between the tunable laser and the spectroscopic prism.

[0026] The present invention may be improved as follows: the beam splitter prism is a polarization beam splitter prism.

[0027] Furthermore, the atomic vapor saturation absorption spectrum measurement module also includes a 1 / 4 wave plate, and the 1 / 4 wave plate is arranged between the polarization beam splitter prism and the atomic vapor chamber.

[0028] A tunable laser absolute frequency calibration system comprises an atomic vapor saturation absorption spectrum measurement module, a signal acquisition module and a data analysis module; the atomic vapor saturation absorption spectrum measurement module receives laser light output by a target tunable laser to measure the atomic vapor saturation absorption spectrum and outputs a signal; the signal acquisition module acquires the output signal of the atomic vapor saturation absorption spectrum measurement module and transmits it to the data analysis module; the data analysis module analyzes the output signal to obtain the atomic saturation absorption wavelength, and then processes it to obtain the frequency signal of the target tunable laser.

[0029] In the present invention, the atomic vapor saturation absorption spectrum measurement module comprises a spectroscopic prism, an atomic vapor chamber, a reflector and a photoelectric detector; the atomic vapor chamber is arranged between the spectroscopic prism and the reflector;

[0030] The spectroscopic prism is used to receive the laser light emitted by the tunable laser and perform spectroscopic processing; the atomic vapor chamber is used to allow the laser light processed by the spectroscopic prism to pass through; the reflector is used to receive the laser light passing through the atomic vapor chamber and reflect it to pass through the atomic vapor chamber in the opposite direction; the photoelectric detector is used to receive the laser light passing through the atomic vapor chamber in the reverse direction and perform photoelectric signal conversion.

[0031] In the present invention, the atomic vapor saturation absorption spectrum measurement module further includes an optical isolator, and the optical isolator is arranged between the tunable laser and the spectroscopic prism.

[0032] The present invention may be improved as follows: the beam splitter prism is a polarization beam splitter prism.

[0033] Furthermore, the atomic vapor saturation absorption spectrum measurement module further includes a quarter wave plate, which is arranged between the polarization beam splitter prism and the atomic vapor chamber. By such an arrangement, the signal strength can be increased fourfold, thereby improving the signal-to-noise ratio of the system.

[0034] In the present invention, the tunable laser absolute frequency calibration system also includes a frequency doubling module, which is movably arranged between the tunable laser and the atomic vapor saturation absorption spectrum measurement module and can switch between frequency doubling processing and non-frequency doubling processing. By adding the frequency doubling module, it can be used to perform absolute frequency calibration on the mid-infrared tunable laser.

[0035] Furthermore, the frequency doubling module includes an optical power amplifier and a nonlinear crystal.

[0036] Furthermore, the nonlinear crystal includes one of a BBO nonlinear crystal, an LBO nonlinear crystal, a PPLN periodically poled nonlinear crystal, a PPKDP periodically poled nonlinear crystal and a waveguide.

[0037] In the present invention, the signal acquisition module includes an oscilloscope and an acquisition card, and the data analysis module includes an algorithm processor.

[0038] The present invention has the following beneficial effects:

[0039] (1) The method for calibrating the absolute frequency of a tunable laser of the present invention uses the output signal after saturated absorption of atomic vapor to perform data analysis to obtain the frequency signal of the tunable laser and calibrate the absolute frequency of the tunable laser. The method has high accuracy and does not rely on a complex calibration system.

[0040] (2) The method for calibrating the absolute frequency of a tunable laser of the present invention utilizes the narrow line width and Doppler shift-free characteristics of the atomic vapor saturation absorption spectrum to perform absolute frequency calibration of tunable lasers in the ultraviolet, visible light, and mid-infrared bands. By finding the atomic saturation absorption wavelength at the corresponding moment of the saturation absorption peak from the saturation absorption spectrum, the output wavelength of the tunable laser can be obtained, thereby achieving calibration of the absolute frequency.

[0041] (3) The tunable laser absolute frequency calibration system of the present invention measures the atomic vapor saturation absorption spectrum of the tunable laser output laser through an atomic vapor saturation absorption spectrum measurement module to perform absolute frequency calibration, with high frequency accuracy and simple system structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] The technical solution of the present invention is further described below in conjunction with the accompanying drawings and specific implementation methods.

[0043] Figure 1 It is a schematic diagram of the overall structure of the tunable laser absolute frequency calibration system according to Embodiment 1 of the present invention;

[0044] Figure 2 It is a schematic diagram of the overall structure of the tunable laser absolute frequency calibration system according to Embodiment 1 of the present invention;

[0045] Figure 3 It is a schematic diagram of the overall structure of the tunable laser absolute frequency calibration system according to Embodiment 1 of the present invention;

[0046] Figure 4 It is a schematic diagram of the overall structure of the tunable laser absolute frequency calibration system according to Embodiment 1 of the present invention;

[0047] Figure 5 is the saturation absorption spectrum of rubidium atomic vapor;

[0048] Figure 6 It is a signal transmission diagram of a tunable laser absolute frequency calibration system of the present invention;

[0049] Figure 7 It is a flow chart of a method for calibrating absolute frequency of a tunable laser according to the present invention;

[0050] Figure 8 It is the output signal of the rubidium atomic vapor saturation absorption spectrum measurement module;

[0051] Fig. 9 It is the peak search result of rubidium atomic vapor saturation absorption spectrum;

[0052] Fig.10 It is a fitting method to calibrate absolute frequency;

[0053] The markings in the figure are as follows: 1. Tunable laser; 2. Atomic vapor saturation absorption spectrum measurement module; 3. Frequency doubling module; 4. Signal acquisition module; 5. Data analysis module; 201. Optical isolator; 202. Spectral prism; 203. Atomic vapor chamber; 204. Reflector; 205. Photodetector; 206. Polarization spectroscopic prism; 207. 1 / 4 wave plate. DETAILED DESCRIPTION

[0054] The present invention utilizes the narrow line width and Doppler shift-free characteristics of the atomic vapor saturation absorption spectrum to perform absolute frequency calibration of the tunable laser. Since the saturation absorption wavelength of atomic vapor is mainly concentrated in the visible light band, the atomic vapor saturation absorption spectrum measurement module is used to measure the absolute frequency of the tunable laser in the ultraviolet and visible light bands. For the tunable laser in the infrared band, it is necessary to use a nonlinear crystal to perform frequency doubling frequency conversion before performing absolute frequency calibration.

[0055] Example 1

[0056] like Figure 1 The tunable laser absolute frequency calibration system shown includes an atomic vapor saturation absorption spectrum measurement module 2; the atomic vapor saturation absorption spectrum measurement module 2 includes an optical isolator 201, a spectroscopic prism 202, an atomic vapor chamber 203, a reflector 204 and a photodetector 205. The optical isolator 201, the spectroscopic prism 202, the atomic vapor chamber 203 and the reflector 204 are arranged in sequence; the spectroscopic prism 202 is used to receive the laser light emitted by the tunable laser 1 and perform spectroscopic processing; the atomic vapor chamber 203 is used to allow the laser light processed by the spectroscopic prism 202 to pass through; the reflector 204 is used to receive the laser light passing through the atomic vapor chamber 203 and reflect it to pass through the atomic vapor chamber 203 in the reverse direction; the photodetector 205 is used to receive the laser light passing through the atomic vapor chamber 203 in the reverse direction and perform photoelectric signal conversion.

[0057] Example 2

[0058] like Figure 2 The tunable laser absolute frequency calibration system shown in the embodiment is different from the embodiment 1 in that the beam splitter prism 202 in the atomic vapor saturation absorption spectrum measurement module 2 is a polarization beam splitter prism 206, and the atomic vapor saturation absorption spectrum measurement module 2 further includes a 1 / 4 wave plate 207, which is arranged between the polarization beam splitter prism 206 and the atomic vapor chamber 203. By such an arrangement, the signal strength can be increased four times, and the system signal-to-noise ratio can be improved.

[0059] Example 3

[0060] like Figure 3As shown, the difference between this embodiment and embodiment 1 is that the tunable laser absolute frequency calibration system also includes a frequency doubling module 3. The frequency doubling module 3 is movably arranged between the tunable laser 1 and the atomic vapor saturation absorption spectrum measurement module 2, and can switch between frequency doubling processing and non-frequency doubling processing. By adding the frequency doubling module 3, it can be used to perform absolute frequency calibration on the mid-infrared tunable laser 1.

[0061] Specifically, the frequency doubling module 3 includes an optical power amplifier and a nonlinear crystal. The operating bands of the power amplifier and the nonlinear crystal are sufficient to cover the frequency doubling to measure the saturated absorption spectrum of the atom.

[0062] Frequency doubling is a nonlinear optical process in which two photons with the same frequency interact with nonlinear materials and can combine to produce a new photon with twice the energy of the initial photon (doubled frequency, halved wavelength) while maintaining coherence. The realization of this frequency conversion relies on nonlinear materials, and nonlinear crystals such as BBO and LBO and periodically polarized nonlinear crystals and waveguides such as PPLN and PPKDP can all achieve this function.

[0063] Example 4

[0064] like Figure 4 The tunable laser absolute frequency calibration system shown in this embodiment is different from the embodiment 3 in that it also includes a signal acquisition module 4 and a data analysis module 5. The signal acquisition module 4 acquires the output signal of the atomic vapor saturation absorption spectrum measurement module 2 and transmits it to the data analysis module 5. The data analysis module 5 analyzes the output signal to obtain the atomic saturation absorption wavelength, and then processes it to obtain the frequency signal of the target tunable laser. The signal acquisition module 4 includes data acquisition equipment such as an oscilloscope and an acquisition card, and the data analysis module 5 includes an algorithm processor.

[0065] The principle of absolute frequency calibration of the tunable laser of the present invention is as follows:

[0066] Saturation absorption spectroscopy actually measures the transition frequency of atoms between their ground state and excited state. Figure 1 As shown, the laser output by the tunable laser 1 passes through the atomic vapor chamber 203 from two directions after being processed by the beam splitter prism 202 and the reflector 204. When the frequency of the laser is close to the transition frequency of the elements in the atomic vapor chamber 203, the laser energy will be absorbed by the atoms and stimulate the atomic transition. Therefore, when the frequency of the tunable laser 1 is tuned, the absorption spectrum can be collected by the photodetector 205, as shown in FIG. Figure 5As shown. Due to the thermal motion of atoms, affected by the Doppler effect, the absorption peak width can reach the GHz level. However, when the positive and negative laser beams are irradiated on atoms moving perpendicular to the propagation direction of light, the atoms will not be affected by the Doppler effect and receive lasers of the same frequency. When the laser frequency is consistent with the atomic transition frequency, since the atoms have been excited after absorbing the pump photons, the detection photons will pass through the gas chamber, thereby increasing the transmittance. This is the saturation absorption phenomenon, such as Figure 5 The small peak indicated by the arrow. The position of the saturation absorption peak is determined only by the atomic energy level structure, which is highly reliable. The saturation absorption wavelength of common atoms has been accurately calibrated, as shown in Table 1. On the other hand, the saturation absorption spectrum is not affected by the Doppler effect, and the line width is only about 3MHz, which can greatly improve the frequency calibration accuracy when used for absolute frequency calibration.

[0067] Table 1 Saturation absorption wavelengths of common elements

[0068]

[0069]

[0070] For lasers in the ultraviolet and visible bands, elements with saturated absorption wavelengths within the corresponding tuning range should be selected and placed in the gas chamber. While the wavelength of the tunable laser 1 is being tuned, the output signal of the atomic vapor saturated absorption spectrum measurement module 2 is processed by the signal acquisition module 4 and the data analysis module 5.

[0071] When the output wavelength of the tunable laser 1 scans the saturation absorption wavelength of the corresponding gas, the data acquisition device in the signal acquisition module 4 will collect the saturation absorption peak of the corresponding atom, such as Figure 5 Then the data analysis module 5 uses a processing algorithm to find the time of the saturation absorption peak (as shown by the arrow), and the output wavelength of the tunable laser 1 at this time corresponds to the atomic saturation absorption wavelength. According to this time, the absolute frequency of the tunable laser 1 is obtained and calibrated.

[0072] In terms of specific processing algorithms, for the signal output by the atomic vapor saturation absorption measurement module, we first look for the minimum value of the signal to find the approximate time when the atomic absorption spectrum has Doppler broadening. By comparing the spectral shape of the signal near this time, we find Figure 5 The arrow indicates the position of the characteristic saturation absorption peak, and the time of this position corresponds to the time when the laser output wavelength is the atomic saturation absorption wavelength. The actual atomic saturation absorption spectrum has multiple spectral lines, and the measurement accuracy of the absolute frequency can be improved by fitting methods (see Example 5).

[0073] For a mid-infrared tunable laser, it is difficult to measure the atomic saturation absorption spectrum within its tuning range, so the frequency doubling module 3 can be used to convert the output wavelength into visible light for measurement.

[0074] When implementing it, Figure 6 As shown, the mid-infrared laser outputs a laser with a wavelength of λ. After beam splitting, one path is output for normal use, and the other path is input to the frequency doubling module 3. The laser is amplified by the power amplifier in the frequency doubling module 3 and then input to the nonlinear crystal to convert the frequency doubling light with a wavelength of λ / 2. The frequency doubling light is input to the atomic vapor saturation absorption measurement module to measure the saturation absorption spectrum. The signal acquisition module 4 and the data analysis module 5 are used to find Figure 5 The saturation absorption peak is shown at time t 0 , this moment corresponds to the atomic saturation absorption wavelength λ 0 . From this, we can know that t 0 At this moment, the output wavelength of the laser is λ = 2λ 0 .

[0075] Example 5

[0076] like Figure 7 The tunable laser absolute frequency calibration method shown comprises the following steps:

[0077] S1, selecting an element whose saturation absorption wavelength is within the frequency tuning range of the target tunable laser;

[0078] Furthermore, S1 also includes: S11, determining the tuning frequency range of the tunable laser; when the tuning frequency is in the ultraviolet and visible light bands, executing S2; when the tuning frequency is in the infrared band, performing frequency doubling processing on the output wavelength of the tunable laser, and then executing S2.

[0079] S2, allowing the laser output by the tunable laser to pass through the atomic vapor cell containing the element to excite the atoms and cause saturation absorption, and collecting the output signal of the atomic vapor cell after the atomic vapor is saturatedly absorbed;

[0080] S3, performing data analysis on the output signal to obtain a frequency signal of the tunable laser;

[0081] S3 includes the following steps:

[0082] S31, obtaining the atomic saturation absorption wavelength according to the output signal of the atomic vapor saturation absorption;

[0083] The specific process is as follows: According to the output signal of the atomic vapor saturated absorption spectrum measurement module, the atomic absorption spectrum signal with Doppler broadening at the signal extreme value is found, and compared with the shape of the saturated absorption spectrum, the saturated absorption peak is found, and the wavelength corresponding to the saturated absorption peak is obtained, which is the atomic saturated absorption wavelength.

[0084] S32. Obtaining a frequency signal of the tunable laser according to the relationship between the atomic saturation absorption wavelength and the output wavelength of the tunable laser.

[0085] The frequency signal of the tunable laser in S3 is the output frequency of the tunable laser.

[0086] In S11, when the tuning frequency of the tunable laser is in the ultraviolet and visible light bands, the output wavelength of the tunable laser in S3 is equal to the atomic saturation absorption wavelength, and the output frequency of the tunable laser is obtained; when the tuning frequency of the tunable laser in S11 is in the infrared band, the output wavelength of the tunable laser in S3 is equal to twice the atomic saturation absorption wavelength, and the output frequency of the tunable laser is obtained.

[0087] S4. Calibrate the absolute frequency of the tunable laser using the frequency signal.

[0088] The specific process is as follows:

[0089] like Figure 6 As shown, a tunable laser wavelength with a tuning range of 1480-1640nm is used. After the output laser is split by a beam splitter, one path is used for normal output, and the other is used for absolute frequency calibration. The 1mW laser enters the frequency doubling module. In the frequency doubling module, an EDFA is used for power amplification with an output power of 20mW. The amplified laser enters the PPLN waveguide to produce frequency-doubled light. The PPLN waveguide is 2cm long and has a polarization period of 19.6 microns. It produces 100μW of frequency-doubled light, and the wavelength range of the frequency-doubled light covers the D2 saturated absorption spectrum of rubidium atoms. After the frequency-doubled light enters the atomic vapor saturated absorption spectrum measurement module, the output signal is collected by an oscilloscope. Its output signal is near the saturated absorption of rubidium atoms as shown in the figure. Figure 8 As shown in the saturation absorption spectrum Fig. 9 After searching for peaks, we found Fig. 9 The time corresponding to the ten saturation absorption peaks shown by the dotted lines in the middle. The exact frequencies of these ten absorption peaks from small to large are: 384227903407.0kHz, 384227981877.3kHz, 384228115203.2kHz, 384227848551.3kHz, 384227770081.0kHz, 384229149669.5kHz, 384229181369.5kHz, 384229241689.5kHz, 3842 29121049.5kHz, 384229089349.5kHz, the corresponding times are 1.609867519s, 1.609865530s, 1.609858764s, 1.609851602s, 1.609841550s, 1.609761503s, 1.609759009s, 1.609758298s, 1.609755642s, 1.609750751s. The time and determined frequency of these ten absorption peaks are as follows Fig.10 As shown by 'x' in the figure. Due to the jitter of noise and laser tuning speed, it is necessary to use fitting method to reduce the measurement error. Through linear fitting, it can be obtained that at the time 1.60981s, the absolute frequency of the laser doubled light is 384228503423.8kHz, the corresponding absolute frequency of the laser output is 192114251711.9kHz, and the corresponding wavelength is 1560.490465068nm, as shown in Fig.10 As shown in the middle circle, the tunable laser frequency is calibrated using the absolute frequency.

[0090] It will be easily understood by those skilled in the art that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A tunable laser absolute frequency calibration system, characterized in that: It comprises an atomic vapor saturation absorption spectrum measurement module, a signal acquisition module and a data analysis module; the atomic vapor saturation absorption spectrum measurement module receives the laser output by the target tunable laser to measure the atomic vapor saturation absorption spectrum and outputs a signal; the signal acquisition module acquires the output signal of the atomic vapor saturation absorption spectrum measurement module and transmits it to the data analysis module, the data analysis module analyzes the output signal to obtain the atomic saturation absorption wavelength, and then processes it to obtain the frequency signal of the target tunable laser; The atomic vapor saturation absorption spectrum measurement module comprises a spectroscopic prism, an atomic vapor chamber, a reflector and a photoelectric detector; the atomic vapor chamber is arranged between the spectroscopic prism and the reflector; The spectroscopic prism is used to receive the laser light emitted by the tunable laser and perform spectroscopic processing; the atomic vapor chamber is used to allow the laser light processed by the spectroscopic prism to pass through; the reflector is used to receive the laser light passing through the atomic vapor chamber and reflect it to pass through the atomic vapor chamber in the opposite direction; the photoelectric detector is used to receive the laser light passing through the atomic vapor chamber in the reverse direction and perform photoelectric signal conversion.

2. The tunable laser absolute frequency calibration system according to claim 1, characterized in that: The atomic vapor saturation absorption spectrum measurement module further includes an optical isolator, which is arranged between the tunable laser and the beam splitter prism.

3. The tunable laser absolute frequency calibration system according to claim 1, characterized in that: The beam splitter prism is a polarization beam splitter prism.

4. The tunable laser absolute frequency calibration system according to claim 3, characterized in that: The atomic vapor saturation absorption spectrum measurement module further includes a 1 / 4 wave plate, which is arranged between the polarization beam splitter prism and the atomic vapor chamber.

5. The tunable laser absolute frequency calibration system according to claim 1, characterized in that: The tunable laser absolute frequency calibration system also includes a frequency doubling module, which is movably arranged between the tunable laser and the atomic vapor saturation absorption spectrum measurement module and can switch between frequency doubling processing and non-frequency doubling processing.

6. The tunable laser absolute frequency calibration system according to claim 5, characterized in that: The frequency doubling module includes an optical power amplifier and a nonlinear crystal.

7. The tunable laser absolute frequency calibration system according to claim 6, characterized in that: The nonlinear crystal includes one of a BBO nonlinear crystal, an LBO nonlinear crystal, a PPLN periodically poled nonlinear crystal, a PPKDP periodically poled nonlinear crystal and a waveguide.

8. The tunable laser absolute frequency calibration system according to claim 1, characterized in that: The signal acquisition module includes an oscilloscope and an acquisition card, and the data analysis module includes an algorithm processor.

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