Method for calibrating wavelength meter error by using F-P resonator and saturation absorption module

Abstract

The present invention discloses a method for calibrating the error of a wavemeter by using an F-P resonator and a saturation absorption module. First, during the process of frequency sweeping and tuning of a laser, the absorption peak of the transmitted light of a gas cell is obtained by using a saturation absorption module containing a vacuum alkali metal atomic gas cell. At the same time, a wavemeter and an F-P resonator are used to record the laser frequency change respectively. Finally, taking the laser frequency change measured by the F-P resonator as a reference, the measurement deviation of the wavemeter is obtained through frequency alignment and data processing to complete the calibration. By using the hyperfine energy level transition frequency of alkali metal atoms as a reference benchmark, the present invention realizes the ultra-precise calibration of the frequency measurement error of the wavemeter, improves the authenticity and reliability of the frequency shift data in the measurement of the pressure broadening of the atomic gas cell, and is conducive to analyzing the gas component content. Compared with the existing method, the measurement accuracy of the wavemeter is significantly improved, and the problems of poor frequency measurement accuracy caused by long-term error accumulation and difficulty in meeting the requirements of quantum precision measurement are solved.

Description

Technical Field

[0001] The present invention relates to the technical field of laser frequency measurement and error evaluation, and particularly to a method for calibrating the error of a wavelength meter by using an F-P resonator and a saturation absorption module. Background Art

[0002] Quantum precision measurement devices such as atomic gyroscopes and atomic magnetometers are precision measurement devices that use lasers to polarize and control alkali metal atoms in an atomic gas chamber, and then use the Faraday magneto-optical rotation effect to detect magnetic signals. The core sensitive element - the atomic gas chamber filled with alkali metal and gas atoms - is an important part restricting the overall performance of the device, and the measurement and analysis of physical quantities such as the component ratio pressure of gas atoms in the gas chamber are the key to improving the device performance.

[0003] In current research, for the component pressure of the gas inside the atomic gas chamber, the commonly used solution is to perform tests by means of pressure broadening and calculate the content of each gas component. It is difficult to achieve accurate measurement without physically damaging the gas chamber. Therefore, a wavelength meter is needed. However, when using a wavelength meter to measure the frequency of alkali atom energy levels, due to changes in the mechanical structure and optical devices during long-term use, frequency drift occurs, and the frequency data is often not accurate enough. There are errors in the measured frequency values of the hyperfine energy level structure of alkali atoms, which directly affects the calculation result of the final component pressure and leads to large deviations in the data. Therefore, the present invention uses a scanning F-P resonator to calibrate the true frequency quantity and reduce the measurement error of the wavelength meter. Summary of the Invention

[0004] Aiming at the problem that the existing wavelength meter is difficult to completely remove the measurement error through self-calibration, resulting in the inability to accurately measure the hyperfine energy level structure of alkali metal atoms, the present invention proposes a method for calibrating the error of a wavelength meter by using an F-P resonator and a saturation absorption module, ensuring the measurement accuracy of the hyperfine energy level frequency of alkali atoms and the reliability of atomic devices.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A method for calibrating the error of a wavelength meter by using an F-P resonator and a saturation absorption module, comprising the following steps:

[0007] S1. Use a laser to perform a large-range frequency sweep near the energy level transition frequency of alkali metal atoms;

[0008] S2. Use an optical polarization device to divide the laser beam output by the laser into three beams. The first beam is input to the wavelength meter to record frequency information, the second beam is input to the saturation absorption module to measure the light absorption intensity during the energy level transition of alkali metal atoms, and the third beam is input to the F-P resonator to perform precise measurement of laser frequency changes;

[0009] S3. The second beam of light entering the saturation absorption module, after passing through the alkali metal atomic gas cell, outputs a curve graph of the gas cell transmittance varying with the wavelength meter frequency through a photodetector, which is used as waveform one;

[0010] S4. The third beam of light uses an F-P resonator to scan and output a frequency peak shift graph, calculates the frequency shift amount of the moving frequency peak through the sweep time, and further obtains the relationship between frequency and time;

[0011] S5. Take the gas cell transmittance data output by the saturation absorption module as the dependent variable, and take the frequency information measured by the F-P cavity as the independent variable to obtain waveform two;

[0012] S6. Perform standard alignment and data processing on waveform one and waveform two. At this time, the deviation between the two is the calibration deviation of the wavelength meter frequency.

[0013] Further, in step S1, the alkali metal atoms are two isotopes of rubidium element.

[0014] Further, the two isotopes of rubidium element are 85 Rb and 87 Rb.

[0015] Further, the internal optical path of the saturation absorption module in step S3 is in the opposite propagation direction, which is used to eliminate the Doppler broadening effect of alkali metal atoms.

[0016] Further, the free spectral range of the F-P resonator in step S4 is 1.5 GHz and below.

[0017] Further, in step S5, the horizontal axis and vertical axis of waveform 2 use the scan time as the common independent variable.

[0018] On the other hand, the present invention also provides a device for calibrating the error of a wavelength meter, including:

[0019] An optical polarization device for splitting the laser output beam into three beams. The first beam is input to the wavelength meter to record frequency information, the second beam is input to the saturation absorption module to measure the light absorption intensity during the energy level transition of alkali metal atoms, and the third beam is input to the F-P resonator for precise measurement of laser frequency change;

[0020] An F-P resonator for precise measurement of laser frequency change and outputting a frequency peak shift graph;

[0021] A saturation absorption module for measuring the light absorption intensity during the energy level transition of alkali metal atoms. The saturation absorption module includes an alkali metal atomic gas cell and a photodetector. After the second beam of light passes through the alkali metal atomic gas cell, a curve graph of the gas cell transmittance varying with the wavelength meter frequency is output through the photodetector;

[0022] An error calculation module for calculating the calibration deviation of the wavelength meter frequency.

[0023] Furthermore, the method of the error calculation module is as follows:

[0024] (1) Output a curve of the gas cell transmittance varying with the wavelength meter frequency through the photodetector of the saturation absorption module as waveform one.

[0025] (2) Calculate the frequency peak shift of the moving frequency by the sweep time of the F-P resonator, and then obtain the relationship between the frequency and time.

[0026] (3) Take the gas cell transmittance data output by the saturation absorption module as the dependent variable and the frequency information measured by the F-P cavity as the independent variable to obtain waveform two.

[0027] (4) Perform standard alignment and data processing on waveform one and waveform two. At this time, the deviation between the two is the calibration deviation of the wavelength meter frequency.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] The present invention proposes a method for calibrating the error of a wavelength meter using an F-P resonator and a saturation absorption module. First, during the process of frequency sweeping and tuning of the laser, a saturation absorption module containing a vacuum alkali metal atom gas cell is used to obtain the absorption peak of the transmitted light of the gas cell. At the same time, the wavelength meter and the F-P resonator are used to record the laser frequency changes respectively. Finally, taking the laser frequency measured by the F-P resonator as the reference, the measurement deviation of the wavelength meter is obtained through frequency alignment and data processing to complete the calibration. By using the hyperfine energy level transition frequency of alkali metal atoms as the reference benchmark, the present invention realizes the ultra-precise calibration of the frequency measurement error of the wavelength meter, improves the authenticity and reliability of the frequency shift data in the measurement of the pressure broadening of the atomic gas cell, and is conducive to analyzing the gas component content. Compared with the method of determining the laser frequency using interference fringes, the measurement accuracy is significantly improved by 2-5 times, solving the problems of poor frequency measurement accuracy caused by long-term error accumulation and difficulty in meeting the requirements of quantum precision measurement, especially in the field of quantum precision measurement, for the measurement of aspects such as the hyperfine energy level structure of alkali metal atoms. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings.

[0031] Figure 1 It is a schematic structural diagram of a device for calibrating the error of a wavelength meter using an F-P resonator and a saturation absorption module provided by an embodiment of the present invention;

[0032] Figure 2 This is the frequency calibration result diagram provided by the embodiment of the present invention. In the figure, Fg is the atomic ground state, Fe is the excited state of the atomic energy level, and → represents the energy transition between energy levels; Detailed implementation manners

[0033] To better understand the technical solution, the method of the present invention will be described in detail below with reference to the accompanying drawings.

[0034] Refer to Figure 1 As shown, a method for calibrating the error of a wavemeter by using an F-P resonator and a saturated absorption module provided by the present invention includes:

[0035] S1. Use a laser to perform a large-range frequency sweep near the energy transition frequency of alkali metal atoms; the frequency range is determined according to the type of alkali metal atoms selected, generally on the order of dozens of GHz; in one embodiment, the alkali metal atoms are two isotopes of rubidium element. For example, the D1 line at 795 nm of Rb atoms is used for the energy transition frequency of the alkali metal.

[0036] S2. Use an optical polarization device to divide the laser output beam into three beams. The first beam is input to the wavemeter to record frequency information, the second beam is input to the saturated absorption module to measure the light absorption intensity during the energy transition of alkali metal atoms, and the third beam is input to the F-P resonator to measure the precise laser frequency change; the internal optical path of the saturated absorption module is in the opposite propagation direction to eliminate the Doppler broadening effect of alkali metal atoms. Among them, in one embodiment, the optical polarization device is implemented by a BS optical polarization device (Beam Splitter).

[0037] S3. The second beam of light entering the saturated absorption module, after passing through the alkali metal atomic cell, outputs a curve graph of the cell transmittance versus the wavemeter frequency through a photodetector as waveform one; the saturated absorption module is used to eliminate the Doppler broadening effect of atoms, so as to ensure that the test result is the accurate hyperfine transition frequency of alkali metal atoms and is not affected by non-natural broadening. The saturated absorption module contains a vacuum cell filled with alkali metal atoms. For example, in one embodiment, the alkali metal atoms are natural abundance Rb ( 85 Rb accounts for about 71.5%, 87 Rb accounts for about 28.5%) to obtain more hyperfine energy levels as references (8 lines instead of 4 lines under a single atom), and the vacuum cell is made of a glass material with good light transmittance.

[0038] S4. The third beam of light uses an F-P resonator to scan and output the frequency peak shift diagram. Calculate the frequency shift amount of the moving frequency peak through the sweep time, and then obtain the relationship between frequency and time. In an embodiment, the F-P resonator is a scanning Fabry-Perot interferometer, mainly used for laser linewidth testing. The smaller the free spectral range, the higher the measurement accuracy of this method. For example, the free spectral range of the F-P resonator is 1.5 GHz or less.

[0039] S5. Take the gas cell transmittance data output by the saturation absorption module as the dependent variable (vertical axis), and take the frequency information measured by the F-P cavity as the independent variable (horizontal axis) to obtain Waveform 2. The horizontal axis and vertical axis of Waveform 2 use the sweep time as the common independent variable.

[0040] S6. Perform standard alignment and data processing on Waveform 1 and Waveform 2. At this time, the deviation between the two is the frequency calibration deviation of the wavemeter. Among them, Waveform 2 is the reference curve, and Waveform 1 is the test curve of the wavemeter to be calibrated.

[0041] The frequency calibration result diagram of this embodiment is as Figure 2 shown. The horizontal axis is the laser sweep frequency, and the frequency range is near the D1 line of Rb; the vertical axis is the light absorption intensity, characterized by a percentage. The F-P cavity reference image is marked with a total of 8 hyperfine energy level transition lines, among which 87 Rb and 85 Rb each have 4, all transitioning from the ground state g to the excited state e. The deviation between the wavemeter and the F-P cavity markings in the figure is the schematic error, but it does not represent the true size of the error. This method uses an F-P resonator to achieve ultra-precise calibration of the frequency measurement error, and the measurement accuracy is improved by more than 2 to 5 times.

[0042] On the other hand, the present invention also provides a device for calibrating the error of a wavemeter, including:

[0043] An optical polarization device for dividing the laser output beam into three beams. The first beam is input to the wavemeter to record frequency information, the second beam is input to the saturation absorption module to measure the light absorption intensity during the energy level transition of alkali metal atoms, and the third beam is input to the F-P resonator for precise measurement of laser frequency changes;

[0044] An F-P resonator for precise measurement of laser frequency changes and outputting a frequency peak shift diagram;

[0045] A saturation absorption module for measuring the light absorption intensity during the energy level transition of alkali metal atoms. The saturation absorption module includes an alkali metal atom gas cell and a photodetector. After the second beam of light passes through the alkali metal atom gas cell, the photodetector outputs a curve graph of the gas cell transmittance changing with the wavemeter frequency;

[0046] An error calculation module for calculating the frequency calibration deviation of the wavemeter.

[0047] Furthermore, the method of the error calculation module is as follows:

[0048] (1) Output the curve of the cell transmittance varying with the wavelength meter frequency through the photodetector of the saturation absorption module as waveform one.

[0049] (2) Calculate the frequency peak frequency shift amount of the moving frequency through the F-P cavity sweep time calculation, and then obtain the relationship between the frequency and time.

[0050] (3) Take the cell transmittance data output by the saturation absorption module as the dependent variable, and take the frequency information measured by the F-P cavity as the independent variable to obtain waveform two.

[0051] (4) Perform standard alignment and data processing on waveform one and waveform two. At this time, the deviation between the two is the calibration deviation of the wavelength meter frequency.

[0052] The advantages of the present invention compared with the prior art are as follows:

[0053] (1) The present invention uses the hyperfine energy level transition frequency of alkali metal rubidium atoms as the reference benchmark, which significantly improves the measurement accuracy of the wavelength meter compared with the method of using interference fringes to determine the laser frequency.

[0054] (2) The calibration of the laser frequency by the method of the present invention improves the authenticity and reliability of the frequency shift data in the atomic cell pressure broadening test, which is beneficial to analyzing the gas component content.

[0055] (3) The present invention meets the accuracy measurement requirements of the wavelength meter for scientific research in quantum precision measurement.

[0056] The above is only the preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.

Claims

1. A method for calibrating the error of a wavelength meter using an F-P resonator and a saturable absorption module, characterized in that, It includes the following steps: S1. Use a laser to perform a wide-range frequency sweep near the energy level transition frequency of alkali metal atoms; S2. Use an optical polarization device to divide the laser beam output into three beams. The first beam is input to a wavemeter to record frequency information, the second beam is input to a saturated absorption module to measure the light absorption intensity during the energy level transition of alkali metal atoms, and the third beam is input to an F-P resonator to measure the precise change in laser frequency; S3. For the second beam entering the saturated absorption module, after passing through the alkali metal atom cell, a graph of the cell transmittance varying with the wavemeter frequency is output by a photodetector as Waveform 1; S4. The third beam is scanned by the F-P resonator to output a frequency peak shift map. The frequency shift amount of the moving frequency peak is calculated through the frequency sweep time, and then the relationship between frequency and time is obtained; S5. Take the cell transmittance data output by the saturated absorption module as the dependent variable and the frequency information measured by the F-P resonator as the independent variable to obtain Waveform 2; S6. Perform standard alignment and data processing on Waveform 1 and Waveform 2. At this time, the deviation between the two is the wavemeter frequency calibration deviation.

2. The method for calibrating the error of a wavelength meter using an F-P resonator and a saturable absorption module according to claim 1, characterized in that, In step S1, the alkali metal atoms are two isotopes of rubidium.

3. The method for calibrating the error of a wavelength meter using an F-P resonator and a saturable absorption module according to claim 2, characterized in that, Two isotopes of rubidium are 85 Rb and 87 Rb.

4. The method for calibrating the error of a wavelength meter using an F-P resonator and a saturable absorption module according to claim 1, characterized in that, In step S3, the internal optical path of the saturated absorption module is in the opposite propagation direction to eliminate the Doppler broadening effect of alkali metal atoms.

5. The method for calibrating the error of a wavelength meter using an F-P resonator and a saturable absorption module according to claim 1, characterized in that, In step S4, the free spectral range of the F-P resonator is 1.5 GHz and below.

6. The method for calibrating the error of a wavelength meter using an F-P resonator and a saturable absorption module according to claim 1, characterized in that, In step S5, the horizontal and vertical axes of Waveform 2 use the sweep time as the common independent variable.

7. An apparatus for calibrating the error of a wavelength meter, characterized in that, It includes: An optical polarization device for dividing the laser beam output into three beams. The first beam is input to a wavemeter to record frequency information, the second beam is input to a saturated absorption module to measure the light absorption intensity during the energy level transition of alkali metal atoms, and the third beam is input to an F-P resonator to measure the precise change in laser frequency; An F-P resonator for measuring the precise change in laser frequency and outputting a frequency peak shift map; A saturated absorption module for measuring the light absorption intensity during the energy level transition of alkali metal atoms. The saturated absorption module includes an alkali metal atom cell and a photodetector. After the second beam passes through the alkali metal atom cell, a graph of the cell transmittance varying with the wavemeter frequency is output by the photodetector; An error calculation module for calculating the wavemeter frequency calibration deviation. The method of the error calculation module is: (1) Output a graph of the cell transmittance varying with the wavemeter frequency by the photodetector of the saturated absorption module as Waveform 1; (2) Calculate the frequency shift amount of the moving frequency peak through the frequency sweep time of the F-P resonator, and then obtain the relationship between frequency and time; (3) Take the cell transmittance data output by the saturated absorption module as the dependent variable and the frequency information measured by the F-P cavity as the independent variable to obtain Waveform 2; (4) Perform standard alignment and data processing on Waveform 1 and Waveform 2. At this time, the deviation between the two is the wavemeter frequency calibration deviation.

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