Accurate frequency and wavelength detection method and system for atomic and molecular saturation absorption spectrum

Abstract

The present invention discloses a precise atomic and molecular saturation absorption spectrum frequency wavelength detection method and system, comprising a highly stable laser source, a first polarization beam splitter prism, a first plane reflector, a beat frequency interference module, an optical phase-locked loop and an acousto-optic modulator, wherein the output end of the detection laser is connected to the input end of the first polarization beam splitter prism, the first optical path refraction end of the first polarization beam splitter prism is connected to the input end of the beat frequency interference module, the output end of the beat frequency interference module is connected to the input end of the optical phase-locked loop, the output end of the frequency reference source is connected to the input end of the optical phase-locked loop, the output end of the optical phase-locked loop is connected to the control input end of an AOM driver, and the control output end of the AOM driver is connected to the input end of the acousto-optic modulator. The present invention realizes controllable tuning of the detection laser frequency by setting an acousto-optic modulator, effectively avoids the change of the acousto-optic modulation diffraction angle, and realizes fast and controllable locking of the detection laser frequency.

Description

Technical Field

[0001] The present invention relates to the technical field of precision spectrum detection, and in particular to a precise atomic and molecular saturation absorption spectrum frequency and wavelength detection method and system. Background Art

[0002] Atomic and molecular saturated absorption spectra have the characteristics of high stability and high accuracy, and are widely used in the field of precision measurement physics. The traditional method of detecting atomic and molecular saturated absorption spectra mainly relies on laser locking technology, which builds a saturated absorption spectrum detection system, scans the frequency / wavelength of the laser to detect the saturated absorption spectrum of atoms and molecules, and finally uses the servo locking control technology of laser frequency / wavelength to lock the frequency of the laser to the atomic and molecular saturated absorption spectrum, and then measures the frequency of the locked laser to achieve the calibration of the absolute frequency / wavelength of the atomic and molecular saturated absorption spectrum.

[0003] The traditional method is to scan the laser frequency relatively. During the scanning process, the absolute frequency / wavelength of the laser cannot be accurately known. This method leads to a servo locking control technology that is heavily dependent on the laser frequency / wavelength. If the locking parameter optimization is not matched, the absolute frequency / wavelength calibration of the atomic and molecular saturation absorption spectrum will be seriously deviated. Therefore, a precise atomic and molecular saturation absorption spectrum frequency and wavelength detection method and system are needed. Summary of the invention

[0004] In view of the existing technical defects, the purpose of the present invention is to provide an accurate atomic and molecular saturated absorption spectrum frequency and wavelength detection method and system, which uses an acousto-optic modulator to bias-lock the frequency of the laser to a high-frequency stable laser wavelength reference source, thereby realizing accurate adjustment of the laser absolute frequency, and the adjustment of the laser absolute frequency has extremely high accuracy. By using the laser to construct an atomic and molecular saturated absorption spectrum detection system, it is possible to achieve accurate scanning of the atomic and molecular spectrum absolute frequency, thereby realizing real-time absolute calibration of the atomic and molecular saturated absorption spectrum frequency, and the absolute frequency / wavelength calibration of the atomic and molecular saturated absorption spectrum can be achieved without relying on a laser frequency servo locking control system.

[0005] The present invention comprises a high-stable laser source, a first polarization beam splitter prism, a first plane reflector, an optical phase-locked loop and an acousto-optic modulator, wherein the output end of the detection laser is connected to the input end of the first polarization beam splitter prism, the first optical path refraction end of the first polarization beam splitter prism is connected to the input end of the beat frequency interference module, the output end of the beat frequency interference module is connected to the input end of the optical phase-locked loop, the output end of the frequency reference source is connected to the input end of the optical phase-locked loop, the output end of the optical phase-locked loop is connected to the control input end of an AOM driver, and the control output end of the AOM driver is connected to the input end of the acousto-optic modulator.

[0006] Furthermore, the beat frequency interference module includes a high-stable reference source, a second polarization beam splitter prism, a third polarization beam splitter prism and a first photoelectric receiver, the output end of the high-stable reference source is connected to the light path incident end of the second polarization beam splitter prism, the first light path refraction end of the second polarization beam splitter prism is connected to the frequency detection module, the second light path refraction end of the second polarization beam splitter prism and the second light path refraction end of the first polarization beam splitter prism are respectively connected to the light path incident end of the third polarization beam splitter prism, the output end of the third polarization beam splitter prism is connected to the input end of the first photoelectric receiver, and the output end of the first photoelectric receiver is connected to the input end of the optical phase-locked loop.

[0007] Furthermore, the frequency detection module includes a second photoelectric receiver, a partial reflector, an atomic and molecular absorption chamber and a high reflector, the first light path refraction end of the second polarization beam splitter prism is connected to the light path incident end of the partial reflector, the first light path reflection end of the partial reflector is connected to the input end of the second photoelectric receiver, the second light path reflection end of the partial reflector is connected to the input end of the atomic and molecular absorption chamber, and the output end of the atomic and molecular absorption chamber is connected to the light path incident end of the high reflector.

[0008] Furthermore, half wave plates are arranged at the incident ends of the light paths of the first polarization beam splitter prism, the second polarization beam splitter prism and the third polarization beam splitter prism.

[0009] Furthermore, the highly stable laser source may be a frequency-stabilized laser or a femtosecond optical frequency comb.

[0010] Furthermore, the detection laser is a single-frequency narrow-linewidth tunable laser.

[0011] In another aspect, a precise atomic and molecular saturation absorption spectrum frequency and wavelength detection method, for performing the precise atomic and molecular saturation absorption spectrum frequency and wavelength detection method, comprises inputting the beat frequency electrical signal of the first photoelectric receiver into an optical phase-locked loop;

[0012] The optical phase-locked loop forms a feedback control signal by comparing the standard microwave frequency signal input by the frequency reference source with the generated beat frequency electrical signal to change the driving frequency of the acousto-optic modulator, and changes the frequency of the beat frequency beam with the high-stability laser source in real time, so that the frequency difference between the two is consistent with the frequency reference source.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] (1) The present invention utilizes the optical phase-locked loop to accurately and controllably change the characteristics of the laser frequency, and scans the absolute frequency of the detection beam with high precision, thereby achieving absolute frequency calibration of the atomic and molecular saturation absorption spectrum signal frequency.

[0015] (2) The present invention can achieve Hz-level optical frequency change, and thus achieve Hz-level spectrum signal calibration. Compared with the traditional method, it avoids the use of frequency servo locking control system and is more universal and universal.

[0016] (3) The present invention realizes precise and controllable tuning of the detection laser frequency by setting an acousto-optic modulator, effectively avoiding the change of the diffraction angle of the acousto-optic modulation, and can overcome the shortcomings of the traditional laser such as small frequency tuning range and low frequency response, and realize fast and controllable locking of the detection laser frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic diagram of the process of an accurate atomic and molecular saturation absorption spectrum frequency and wavelength detection method and system proposed by the present invention; DETAILED DESCRIPTION

[0018] The present invention is described in detail below in conjunction with the embodiments and accompanying drawings. However, it should be understood that the embodiments and drawings are only used to exemplify the present invention and do not constitute any limitation on the protection scope of the present invention.

[0019] like Figure 1 As shown, the present invention includes a high-stable laser source, a first polarization beam splitter prism, a first plane reflector, an optical phase-locked loop and an acousto-optic modulator, the output end of the detection laser is connected to the input end of the first polarization beam splitter prism, the first light path refraction end of the first polarization beam splitter prism is connected to the input end of the beat frequency interference module, the output end of the beat frequency interference module is connected to the input end of the optical phase-locked loop, the output end of the frequency reference source is connected to the input end of the optical phase-locked loop, the output end of the optical phase-locked loop is connected to the control end of the AOM driver, and the output end of the AOM driver is connected to the input end of the acousto-optic modulator.

[0020] In the experiment, a highly stable laser source provides an absolute frequency / wavelength reference for the laser, and its wavelength stability and accuracy can reach above the E-12 level. The highly stable laser source can be a frequency-stabilized laser or a femtosecond optical frequency comb. The detection laser is a single-frequency narrow-linewidth tunable laser. After passing through a half-wave plate, the laser is incident on the polarization beam splitter prism PBS1. The transmitted light beam of PBS1 is diffracted after passing through the acousto-optic modulation AOM. The diffracted light passes through the collimating lens Lens and the quarter-wave plate and is incident on the plane reflector Mi rror1, where the zero-order diffraction light is blocked by the shading plate. After being completely reflected by Miorror1, the first-order diffraction light passes through the quarter-wave plate and the collimating lens Lens again and is incident on PBS1, and is reflected by PBS1 to PBS2. At this time, the light beam incident on PBS2 passes through the AOM twice, and its frequency shift frequency is twice the frequency of the AOM driver.

[0021] In this embodiment, the beat frequency interference module includes a highly stable reference source, a second polarization beam splitter prism, a third polarization beam splitter prism and a first photoelectric receiver, the output end of the highly stable reference source is connected to the optical path incident end of the second polarization beam splitter prism, the first optical path refraction end of the second polarization beam splitter prism is connected to the frequency detection module, the second optical path refraction end of the second polarization beam splitter prism and the second optical path refraction end of the first polarization beam splitter prism are respectively connected to the optical path incident end of the third polarization beam splitter prism, the output end of the third polarization beam splitter prism is connected to the input end of the first photoelectric receiver, and the output end of the first photoelectric receiver is connected to the input end of the optical phase-locked loop.

[0022] The incident light beam of the high-stable reference source passes through the half wave plate and then enters the second polarization beam splitter prism PBS2. Its transmitted light overlaps with the emission light beam of the first polarization beam splitter prism PBS1 in space, and then passes through the half wave plate and the polarization beam splitter prism PBS3 together to form a beat frequency interferometer. The beat frequency interference signal is received by the photoelectric receiver PD1 and generates a beat frequency electrical signal.

[0023] The beat frequency electrical signal of the photoelectric receiver PD1 is input into the optical phase-locked loop control system. The optical phase-locked loop control system forms a feedback control signal by comparing the standard microwave frequency signal input by the frequency reference source with the generated beat frequency electrical signal, thereby changing the driving frequency of the AOM modulator, and then changing the frequency of the beat frequency beam with the high-stability laser source in real time, so that the frequency difference between the two is consistent with the frequency reference source, thereby realizing precise control of the detection laser beam frequency.

[0024] By changing the output frequency setting of the frequency reference source, the frequency of the detection laser incident on the second polarization beam splitter prism PBS2 can be accurately changed. And the change of the absolute frequency of the detection light is completely controlled by the frequency reference source, which can achieve Hz-level output frequency changes, thereby enabling the frequency of the detection laser to achieve Hz-level scanning.

[0025] In this embodiment, the frequency detection module includes a second photoelectric receiver, a partial reflector, an atomic and molecular absorption chamber and a high reflector. The first light path refraction end of the second polarization splitter prism is connected to the light path incident end of the partial reflector, the first light path reflection end of the partial reflector is connected to the input end of the second photoelectric receiver, the second light path reflection end of the partial reflector is connected to the input end of the atomic and molecular absorption chamber, and the output end of the atomic and molecular absorption chamber is connected to the light path incident end of the high reflector.

[0026] By using the transmission light of the detection laser incident on the second polarization beam splitter prism PBS2, an atomic and molecular saturation absorption spectrum detection device can be constructed. The transmission light of the detection laser incident on the second polarization beam splitter prism PBS2 is reflected by the partial reflector Mirror2, and then incident on the atomic and molecular absorption chamber ce 11, and then returned by the high-reflection mirror Mirror3 to form the detection of atomic and molecular saturation absorption. The light beam that passes through the atomic and molecular absorption chamber ce 11 twice passes through the partial reflector Mirror2 again, and is received by the photodetector PD2, converted into an electrical signal of the atomic and molecular saturation absorption spectrum, and the absolute frequency detection of the saturation absorption spectrum is realized.

[0027] In the implementation example, the detection laser is a 532nm single-frequency linearly polarized laser with an output power of 2mW, and the reference laser source is an optical frequency comb, wherein the driving frequency of the acousto-optic modulator is 250MHz, and the output frequency of the frequency reference source is 50MHz. By using an optical phase-locked loop control system, the absolute frequency of the 532nm laser can be scanned in steps of 1Hz, and the absolute frequency / wavelength of dozens of saturated absorption spectra of the laser at 532nm can be accurately detected.

[0028] Inputting the beat frequency electrical signal of the photoelectric receiver PD1 into the optical phase-locked loop control system;

[0029] The optical phase-locked loop control system forms a feedback control signal to change the driving frequency of the acousto-optic modulator by comparing the standard microwave frequency signal input by the frequency reference source with the generated beat frequency electrical signal, and changes the frequency of the beat frequency beam with the high-stability laser source in real time, so that the frequency difference between the two is consistent with the frequency reference source.

[0030] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. Accurate atomic and molecular saturation absorption spectrum frequency and wavelength detection method, characterized in that: The invention comprises a high-stable laser source, a first polarization beam splitter prism, a first plane reflector, a beat frequency interference module, an optical phase-locked loop and an acousto-optic modulator, wherein the output end of the detection laser is connected to the input end of the first polarization beam splitter prism, the first optical path refraction end of the first polarization beam splitter prism is connected to the input end of the beat frequency interference module, the output end of the beat frequency interference module is connected to the input end of the optical phase-locked loop, the output end of the frequency reference source is connected to the input end of the optical phase-locked loop, the output end of the optical phase-locked loop is connected to the control input end of an AOM driver, and the control output end of the AOM driver is connected to the input end of the acousto-optic modulator; The beat frequency interference module includes a high-stable reference source, a second polarization beam splitter prism, a third polarization beam splitter prism and a first photoelectric receiver, the output end of the high-stable reference source is connected to the light path incident end of the second polarization beam splitter prism, the first light path refraction end of the second polarization beam splitter prism is connected to the frequency detection module, the second light path refraction end of the second polarization beam splitter prism and the second light path refraction end of the first polarization beam splitter prism are respectively connected to the light path incident end of the third polarization beam splitter prism, the output end of the third polarization beam splitter prism is connected to the input end of the first photoelectric receiver, and the output end of the first photoelectric receiver is connected to the input end of the optical phase-locked loop; The frequency detection module includes a second photoelectric receiver, a partial reflector, an atomic and molecular absorption chamber and a high reflector. The first light path refraction end of the second polarization beam splitter is connected to the light path incident end of the partial reflector, the first light path reflection end of the partial reflector is connected to the input end of the second photoelectric receiver, the second light path reflection end of the partial reflector is connected to the input end of the atomic and molecular absorption chamber, and the output end of the atomic and molecular absorption chamber is connected to the light path incident end of the high reflector.

2. The accurate atomic and molecular saturation absorption spectrum frequency and wavelength detection method according to claim 1 is characterized in that: Half wave plates are arranged at the incident ends of the light paths of the first polarization beam splitter prism, the second polarization beam splitter prism and the third polarization beam splitter prism.

3. The accurate atomic and molecular saturation absorption spectrum frequency and wavelength detection method according to claim 1 is characterized in that: The highly stable laser source is a frequency-stabilized laser or a femtosecond optical frequency comb.

4. The accurate atomic and molecular saturation absorption spectrum frequency and wavelength detection method according to claim 1 is characterized in that: The detection laser is a single-frequency narrow-linewidth tunable laser.

5. An accurate atomic and molecular saturation absorption spectrum frequency and wavelength detection method, used to implement the accurate atomic and molecular saturation absorption spectrum frequency and wavelength detection method as claimed in any one of claims 1 to 4, characterized in that: inputting the beat frequency electrical signal of the first photoelectric receiver into an optical phase-locked loop; The optical phase-locked loop forms a feedback control signal by comparing the standard microwave frequency signal input by the frequency reference source with the generated beat frequency electrical signal to change the driving frequency of the acousto-optic modulator, and changes the frequency of the beat frequency beam with the high-stability laser source in real time, so that the frequency difference between the two is consistent with the frequency reference source.

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