Self-calibrating atomic wavemeter

Abstract

The invention relates to a self-calibration atomic wavelength meter. The self-calibration atomic wavelength meter comprises a saturated absorption spectrum light path for locking a detection laser frequency on a cesium atom energy level transition line based on a saturated absorption spectrum; the double-peak spectrum light path scans the frequency of a coupled laser after the frequency of the detection laser is locked by a saturated absorption spectrum, and when the detection laser and the coupled laser jointly act on alkali metal atoms and are subjected to resonance excitation, an electromagnetic induced transparency effect is generated; when the detection laser is detuned, the detection laser and the combined laser jointly act on the alkali metal atoms to generate non-resonance excitation, a double-peak EIT spectrum with Doppler frequency shift is generated, and the wavelength measurement of the current detection laser can be completed based on the linear relation between the double-peak spectrum interval and the detuning amount of the detection laser. In addition, the double-peak spectrum interval is compared with the atomic energy level transition frequency, the difference between the double-peak spectrum interval and the atomic energy level transition frequency serves as an error signal to be fed back to the control end of the detection laser, the frequency of the detection laser is tuned to the reference frequency standard, and calibration of the wavemeter can be achieved.

Description

Technical Field

[0001] This invention belongs to the field of atomic wavelength meter technology, and more specifically, relates to a self-calibrating atomic wavelength meter. Background Technology

[0002] Accurate and reliable laser wavelengths are key technologies in precision metrology fields such as atomic clocks, atomic gravimeters, and atomic magnetometers. Accurate frequency references serve as the "ruler" in precision metrology, with significant application prospects in navigation, verification of fundamental physics theories, and the measurement of basic physical constants. Traditional wavelength meters rely on high-quality optical components or precision moving parts, which limits their accuracy and resolution. Furthermore, environmental factors such as mechanical stress, vibration, and temperature fluctuations can cause frequency drift and phase jitter in the built-in standard light source, requiring periodic calibration and correction of the reference light source, thus affecting the accuracy of the measurement results.

[0003] In recent years, saturation absorption spectroscopy (SAS), based on atomic or molecular absorption lines, has used atomic or molecular transition lines as frequency scales. It utilizes opposing pump and probe lasers to detect atoms in specific velocity groups, effectively suppressing Doppler broadening and obtaining atomic transition spectral signals with near-natural linewidths. Due to its sub-Doppler linewidth characteristics, inherent frequency traceability, and high resolution, SAS has been widely applied in optical frequency standards and laser cooling. Although SAS technology has shown significant advantages in laser frequency locking and stabilization, its practical application is still limited by factors such as environmental constraints on long-term stability and the lack of a self-calibration mechanism leading to cumulative frequency shifts. Summary of the Invention

[0004] To address the accuracy limitations caused by reference light source frequency drift in current wavelength meters, this invention proposes a self-calibrating atomic wavelength meter. The wavelength meter designed in this invention can perform continuous measurement of laser frequencies based on real-time self-calibration.

[0005] To achieve the above objectives, the embodiments of the present invention adopt the following technical solutions: A self-calibrating atomic wavelength meter includes a probe laser, a coupling laser, a saturated absorption spectral optical path, and a bimodal spectral optical path; The probe laser is used to generate the probe laser; The saturated absorption spectrum optical path is used to lock the frequency of the probe laser output by the probe laser to the transition line of the alkali metal atomic energy level based on the saturated absorption spectrum, and to use the transition frequency between atomic energy levels as the reference frequency of the wavelength meter. Coupled lasers are used to generate coupled lasers; The dual-peak spectral optical path is used to scan the frequency of the coupled laser after the frequency of the probe laser output from the probe laser is locked by the saturated absorption spectrum. When the probe laser and the coupled laser act together on the alkali metal atoms and resonate, an electromagnetically induced transparency effect will be generated. When the probe laser becomes detuned, the probe laser and the coupled laser act together on the alkali metal atoms to generate non-resonant excitation, producing a dual-peak EIT spectrum with Doppler frequency shift. The dual-peak spectral interval is extracted based on the dual-peak EIT spectrum. Since the dual-peak spectral interval is linearly related to the detuning amount of the probe laser, the wavelength of the current probe laser can be measured based on the extracted dual-peak spectral interval. The dual-peak spectral interval is compared with the transition frequency between atomic energy levels, and the difference between the two is used as an error signal to feed back to the control terminal of the probe laser, tuning the frequency of the probe laser to the reference frequency, thereby achieving the calibration of the wavelength meter.

[0006] Furthermore, the alkali metal atom can be a cesium atom or a rubidium atom.

[0007] Furthermore, the probe laser outputs a probe laser with a wavelength of 852 nm.

[0008] Furthermore, the coupled laser outputs a coupled laser with a wavelength of 509 nm.

[0009] The probe laser, coupling laser, saturated absorption spectrum optical path, and dual-peak spectrum optical path constitute a complete self-calibrating atomic wavelength meter, which uses the transition frequency between atomic energy levels of alkali metal atoms as a reference frequency standard to realize the measurement and calibration of laser wavelength.

[0010] Preferably, both the probe laser and the coupling laser are external cavity semiconductor lasers.

[0011] Compared with the prior art, this application has at least the following beneficial effects: This invention designs an optical frequency standardization method based on saturated absorption spectroscopy and electromagnetically induced transparency spectroscopy, using atomic transition frequencies as a reference. This method overcomes the problems of frequency accumulation drift and phase jitter of the built-in reference light source in traditional wavelength meters, as well as the influence of temperature, achieving self-calibration. Simultaneously, it achieves continuous measurement of laser wavelengths based on the quantitative relationship between the atomic Doppler effect and the spectral spacing between the two peaks, with an accuracy reaching MHz and a maximum measurable range related to the maximum velocity distribution of atoms. This invention provides a robust and high-precision wavelength measurement solution with real-time self-calibration suitable for various high-precision measurement applications. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0013] Figure 1 This is a schematic diagram of the structure of a self-calibrating atomic wavelength meter in one embodiment; Figure 2 This is a diagram of the hyperfine level structure of cesium atoms in one embodiment; Figure 3 The images show the saturated absorption spectrum of cesium atoms and the spectra under different conditions. Figure 3 (a) is the saturated absorption spectrum of cesium atoms. Figure 3 (b) is a double-peaked spectrum showing left detuning. Figure 3 (c) is the EIT spectrum generated during resonance excitation. Figure 3 (d) is a double-peaked spectrum showing right detuning.

[0014] Explanation of reference numerals in the attached figures: 1. Detector laser; 2. First half-wave plate; 3. First polarizing beam splitter prism; 4. First reflecting mirror; 5. Beam collimating device; 6. First dichroic mirror; 7. Second reflecting mirror; 8. First atomic gas cell; 9. Second dichroic mirror; 10. Focusing lens; 11. Photodetector; 12. First beam splitter; 13. Coupled laser; 14. Third reflecting mirror; 15. Balanced photodetector; 16. Second polarizing beam splitter prism; 17. Second half-wave plate; 18. Second beam splitter; 19. Fourth reflecting mirror; 20. Second atomic gas cell; 21. Fifth reflecting mirror; 22. Third beam splitter. Detailed Implementation

[0015] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0016] In one embodiment, a self-calibrating atomic wavelength meter is provided, including a probe laser, a coupling laser, a saturated absorption spectral optical path, and a bimodal spectral optical path; The probe laser is used to generate the probe laser; The saturated absorption spectrum optical path is used to lock the frequency of the probe laser output by the probe laser to the transition line of the alkali metal atomic energy level based on the saturated absorption spectrum, and to use the transition frequency between atomic energy levels as the reference frequency of the wavelength meter. Coupled lasers are used to generate coupled lasers; The dual-peak spectral optical path is used to scan the frequency of the coupled laser after the frequency of the probe laser output from the probe laser is locked by the saturated absorption spectrum. When the probe laser and the coupled laser act together on the alkali metal atoms and resonate, an electromagnetically induced transparency effect will be generated. When the probe laser becomes detuned, the probe laser and the coupled laser act together on the alkali metal atoms to generate non-resonant excitation, producing a dual-peak EIT spectrum with Doppler frequency shift. The dual-peak spectral interval is extracted based on the dual-peak EIT spectrum. Since the dual-peak spectral interval is linearly related to the detuning amount of the probe laser, the wavelength of the current probe laser can be measured based on the extracted dual-peak spectral interval. The dual-peak spectral interval is compared with the transition frequency between atomic energy levels, and the difference between the two is used as an error signal to feed back to the control terminal of the probe laser, tuning the frequency of the probe laser to the reference frequency, thereby achieving the calibration of the wavelength meter.

[0017] Furthermore, the type of alkali metal atom is not limited and can be cesium or rubidium atom.

[0018] Furthermore, the saturated absorption spectrum optical path uses the transition frequency of alkali metal atomic energy levels as a reference standard. It uses strong pump light and weak probe light to excite alkali metal atoms and generate a saturated absorption spectrum. Based on the saturated absorption spectrum, the frequency of the probe laser output by the probe laser is locked on the transition line of alkali metal atomic energy levels. The transition frequency between atomic energy levels is used as the reference frequency standard of the wavelength meter to achieve laser frequency locking.

[0019] The dual-peak spectral optical path works by locking the frequency of the probe laser output from the probe laser to the saturated absorption spectrum, then scanning the frequency of the coupling laser. When the probe laser and the coupling laser act together on alkali metal atoms and resonate, an electromagnetically induced transparency (EIT) effect is generated. When the probe laser becomes detuned, the probe laser and the coupling laser act together on the alkali metal atoms to induce non-resonant excitation, forming a dual-peak EIT spectrum (dual-peak EIT spectrum) through the Doppler frequency shift effect. The wavelength of the probe laser is measured using the spectral spacing between the two peaks. Specifically, the spectral spacing is linearly related to the detuning amount of the probe laser. Based on the extracted spectral spacing, the wavelength of the current probe laser can be measured. Furthermore, the spectral spacing is compared with the transition frequencies between atomic energy levels, and the difference is used as an error signal fed back to the control terminal of the probe laser. This allows the probe laser frequency to be tuned to a reference frequency, thereby calibrating the wavelength meter. Thus, this invention uses the transition frequency of alkali metal atoms as a reference frequency standard and the spacing of the double-peak spectrum to characterize the laser wavelength, overcoming the problems of frequency drift of the built-in reference light source in traditional wavelength meters, and realizing continuous measurement of the probe laser wavelength based on self-calibration of atomic transition frequency.

[0020] Reference Figure 1 One embodiment provides a self-calibrating atomic wavelength meter, which is a self-calibrating atomic wavelength meter based on saturated absorption spectroscopy and electromagnetically induced transparency spectroscopy. It includes: a probe laser 1, a first half-wave plate 2, a first polarizing beam splitter prism 3, a first reflecting mirror 4, a beam collimating device 5, a first dichroic mirror 6, a second reflecting mirror 7, a first atomic gas cell 8, a second dichroic mirror 9, a focusing lens 10, a photodetector 11, a first beam splitter 12, a coupling laser 13, a third reflecting mirror 14, a balanced photodetector 15, a second polarizing beam splitter prism 16, a second half-wave plate 17, a second beam splitter 18, a fourth reflecting mirror 19, a second atomic gas cell 20, a fifth reflecting mirror 21, and a third beam splitter 22. The first atomic gas cell 8 is filled with the same alkali metal atoms as the second atomic gas cell 20; in this embodiment, the alkali metal atoms used are cesium atoms.

[0021] The probe laser output by the probe laser 1 passes through the first half-wave plate 2 and reaches the first polarization beam splitter prism 3. The first polarization beam splitter prism 3 splits the laser into two probe lasers according to the polarization component: the first probe laser and the second probe laser. The first probe laser is incident on the saturated absorption spectrum optical path, and the second probe laser is incident on the double-peak spectrum optical path.

[0022] The saturated absorption spectrum optical path includes a third beam splitter 22, a fourth reflector 19, a second beam splitter 18, a second atomic gas cell 20, a fifth reflector 21, a second half-wave plate 17, a second polarizing beam splitter prism 16, a third reflector 14, and a balanced photodetector 15.

[0023] The first probe laser reflected from the first polarizing beam splitter prism 3 is incident on the third beam splitter 22 and split into two beams. The beam with most of its power is used as the pump light, and the beam with less power is used as the probe light. The pump light is transmitted through the third beam splitter 22 to the fourth reflecting mirror 19, and then reflected by the fourth reflecting mirror 19 to the second beam splitter 18, and then reflected by the second beam splitter 18 to the second atomic gas cell 20. The probe light is reflected by the third beam splitter 22 to the fifth reflecting mirror 21, and then reflected by the fifth reflecting mirror 21 to the second atomic gas cell 20. In this way, the two laser beams incident on the second atomic gas cell 20 propagate collinearly and in opposite directions, generating saturation absorption to eliminate the Doppler effect during their opposing transmission within the second atomic gas cell 20. The detector light, with its weaker power, passes through the second atomic gas cell 20, carrying information about the saturated absorption spectrum. It is then transmitted through the second beam splitter 18 and sequentially split into two beams of equal power and perpendicular polarization by the second half-wave plate 17 and the second polarization beam splitter 16. One beam is transmitted through the second polarization beam splitter 16 and reflected by the third mirror 14 before being injected into the balanced photodetector 15. The other beam is directly reflected by the second polarization beam splitter 16 and injected into the balanced photodetector 15. The balanced photodetector 15 cancels the DC bias of the photocurrent and obtains the saturated absorption spectrum of cesium atoms. Based on the saturated absorption spectrum, the laser controller controls the frequency of the detector laser 1, locking the frequency of the detector laser output by the detector laser 1 to the energy level transition line of cesium atoms.

[0024] The dual-peak spectral optical path includes a first reflecting mirror 4, a beam-splitting collimating device 5, a first dichroic mirror 6, a second reflecting mirror 7, a first atomic gas cell 8, a second dichroic mirror 9, a focusing lens 10, a photodetector 11, and a first beam splitter 12.

[0025] The second probe laser transmitted from the first polarizing beam splitter prism 3 is reflected by the first reflecting mirror 4 to the beam splitting collimating device 5, and split into two parallel and collimated probe beams, namely probe beam I and probe beam II. The coupled laser output from the coupled laser 13 is split into two beams by the first beam splitter 12: coupled laser I and coupled laser II. The coupled laser I is reflected twice by the second reflector 7 and the first dichroic mirror 6 and propagates collinearly and in the same direction with the probe light I into the first atomic gas cell 8; at the same time, the coupled laser II is reflected by the second dichroic mirror 9 and propagates collinearly and in the opposite direction with the probe light II into the first atomic gas cell 8.

[0026] After the frequency of the probe laser output by the probe laser 1 is locked by the saturated absorption spectrum, the frequency of the coupled laser is changed by scanning and controlling the piezoelectric ceramic voltage of the coupled laser 13. When the probe laser and the coupled laser act together on the alkali metal atoms in the first atomic gas cell 8 and resonate and excite, an electromagnetically induced transparency effect will be generated, that is, the frequencies of the probe laser and the coupled laser are not detuned. However, due to the influence of environmental factors such as mechanical stress, vibration, and temperature fluctuations, when the probe laser becomes detuned, the probe laser and the coupled laser act together on the alkali metal atoms and cause non-resonant excitation, which will generate a double-peak EIT spectrum with Doppler frequency shift. The probe light carrying the double-peak EIT spectrum information passes through the first atomic gas cell 8 and is focused by the second dichroic mirror 9 and the focusing lens 10 into the photodetector 11. The photodetector 11 converts the light intensity change into an electrical signal, that is, the double-peak EIT spectrum curve. By modulating and demodulating the double-peak EIT spectrum curve, the double-peak spectral interval is obtained. Since the double-peak spectral interval is linearly related to the detuning amount of the probe laser, the wavelength of the current probe laser can be measured based on the extracted double-peak spectral interval. The spectral interval between the two peaks is compared with the transition frequency between atomic energy levels. The difference between the two is used as an error signal and fed back to the control terminal of the probe laser. The frequency of the probe laser is then tuned to the reference frequency, thereby achieving the calibration of the wavelength meter.

[0027] Preferably, in the above embodiment, the probe laser 1 outputs a probe laser with a wavelength of 852 nm, and the coupling laser 13 outputs a coupling laser with a wavelength of 509 nm. The dual-peak spectral optical path uses the excitation method of the 852 nm probe laser and the 509 nm coupling laser to generate a dual-peak electromagnetic induced transparency (EIT) spectrum.

[0028] Preferably, both the probe laser 1 and the coupling laser 13 are external cavity semiconductor lasers. The power supply of the external cavity semiconductor laser integrates a temperature module, a current module, an external cavity module (piezoelectric ceramic transducer, PZT), and a frequency stabilization module, wherein the temperature, current, and PZT can all tune the laser frequency.

[0029] The dual-peak spectral optical path uses the offset caused by frequency jitter when the probe laser frequency is locked at the hyperfine energy level transition as an error signal, and feeds it back to the control terminal of the probe laser frequency to achieve offset calibration.

[0030] An atom consists of a nucleus and electrons. The principal quantum number N describes the number of shells in which the valence electrons reside, the orbital quantum number L describes the electron's motion around the nucleus, and the spin quantum number S describes the electron's spin. The energy level splitting caused by the interaction between the electron's orbital and spin (LS coupling) is called the fine structure of the atomic energy levels. The total angular momentum of the electron, resulting from the combination of orbital and spin angular momentum, is described by the total angular momentum quantum number J, where J = L + S, L + S⁻¹, ..., |LS|. For the Cs atom (cesium atom), its ground state is 6. 2 S 1 / 2 The lowest excited state is 6. 2 P 1 / 2 and 6 2 P 3 / 2 Dual state, such as Figure 2 As shown.

[0031] Atomic nuclei also possess spin and magnetic moments, with the nuclear spin described by the quantum number I. The interaction between J and I (JI coupling) causes further splitting of energy levels, known as hyperfine structure, with quantum numbers F: F = I + J, I + J⁻¹, …, |IJ|. The element Cs in nature… 133 Cs has a ground state of J = 1 / 2. 133 Cs has I=7 / 2, therefore it has two ground states, F=3 and F=4. Figure 2 for 133 A schematic diagram of the hyperfine structure and transitions of the Cs atom in its ground and excited states. This hyperfine level is used as the reference frequency for an atomic wavelength meter.

[0032] Reference Figure 3 The graph shows the saturated absorption spectrum of cesium atoms and the spectra under different conditions. Figure 3 (a) is the saturated absorption spectrum of cesium atoms, consisting of three intrinsic spectral lines F=4→F'=3,4,5 (according to the transition selection rule ΔF=0,±1) and three cross spectral lines F=4→F'=(3,4),(3,5),(4,5). First, when the probe wavelength is locked at the hyperfine level F'=5, i.e., resonant excitation, the EIT spectrum is generated as follows: Figure 3 As shown in (c). Furthermore, when the laser frequency is locked to other hyperfine energy levels that are not resonant (i.e., not F'=5), a double-peaked EIT spectrum with Doppler shift will be generated due to frequency detuning. The frequency difference between these spectra is compared with the transition frequencies between atomic energy levels, and the difference is used as an error signal fed back to the control terminal of the probe laser. By tuning the probe laser frequency to the reference frequency, the wavelength meter can be self-calibrated. Secondly, when the wavelength is on a non-fine energy level line, the double-peaked spectrum will exhibit... Figure 3 (b) or Figure 3 (d) Corresponds to left detuning and right detuning.

[0033] In the second atomic gas cell 20 of the saturated absorption spectrum optical path, a strong pump light and a weak probe light are used to excite cesium atoms in the second atomic gas cell 20 through opposing transmission. This is based on Doppler broadening and... Figure 1 middle Direction, speed The cesium atom senses the frequency of the probe light as... ,in The wavelength of the laser. It's a wave arrow. It detects the frequency of light. It is the frequency of the probe light that the atom senses. When At that time, the probe light will be absorbed, and there will be That is, detecting the speed of light Cesium group absorption, defining the detuning frequency ,in It is the frequency of atomic energy level transitions; correspondingly, the pump light will be affected by the velocity... The cesium atom group absorbs the light. Two beams of light interact with cesium atoms of different velocity groups. The probe light is very weak, and the proportion of absorption is proportional to the cesium atom group. The number of cesium atoms in the velocity group results in an inverted Maxwell velocity distribution in the absorption spectrum. ).when hour, Both the probe light and the pump light are absorbed by the cesium atom swarm with a velocity of 0. Because the pump light is relatively strong, most of the cesium atoms with a velocity of 0 are consumed, reaching absorption saturation. The intensity of the transmitted light from the probe light increases sharply, exhibiting a sharp spectral line and forming a saturation absorption peak. Based on the above analysis, considering a multi-level system, in the three-level model, the cesium atom has two energy level transition frequencies, namely... , , It is the transition frequency of the first transition path of the cesium atom. It is the transition frequency of the second transition path of the cesium atom. and Therefore, when hour, This will also produce a saturation absorption peak, called a cross-spectral line. For example (according to the transition selection rule ΔF=0,±1), in addition to the 3 intrinsic spectral lines, 3 cross-spectral lines will be generated, namely: The intrinsic spectral lines and cross-spectral lines superimpose to form a complete saturated absorption spectrum, which is used as a reference for laser frequency locking to generate the EIT spectral signal.

[0034] Dual-channel excited bimodal electromagnetically induced transparency (EIT) spectroscopy is generated by locking the probe light frequency to the saturated absorption spectrum using two overlapping lasers, followed by scanning the coupled lasers. When the probe laser frequency is locked at... At that time, due to resonance excitation, a peak curve is obtained. In this case, the frequencies of both the probe laser and the coupling laser are not detuned, so the main effect is electromagnetic induced transparency (EIT). However, due to environmental factors such as mechanical stress, vibration, and temperature fluctuations, the probe laser frequency will experience a cumulative frequency shift, resulting in frequency detuning. In co-current transmission, the Doppler effect caused by frequency shift will produce a double-peak EIT spectrum, and the interval between the two peaks is proportional to the detuning of the probe laser frequency.

[0035] This theory can be analyzed using the following model. Considering the co-propagation and counter-propagation of the probe laser and the coupling laser, assuming the +z direction is defined as the direction of probe laser propagation to the PD, and the velocity of the cesium atom is... For probe light I and coupled laser I propagate in opposite directions, under the condition of probe light frequency detuning, the corrected laser detuning is as follows: and ,in This is the corrected probe light detuning. This represents the probe light detuning amount before correction. For the velocity of cesium atoms, To detect the wavelength of light, This represents the corrected coupling light detuning. This represents the detuning of the coupled light before correction. is the wavelength of the coupling light. For resonant excitation, You can get Similarly, probe beam II and coupled laser beam II propagate together. When probe light I and probe light II propagate in the same direction, the probe laser frequency becomes detuned. Therefore, the difference between the two peaks (i.e., the bimodal spectral interval) That is, the peak difference is directly proportional to the frequency detuning of the probe laser, and its factor is... This shows that tiny frequency shifts can be easily captured by EIT spectroscopy, an ultra-precise method for measuring laser frequency (i.e., wavelength) based on cesium atoms.

[0036] Furthermore, the velocity distribution of cesium atoms follows the Maxwell-Boltzmann distribution. In the formula k B Boltzmann's constant, m The mass of a cesium atom T The thermodynamic temperature is 300 K. The maximum velocity corresponds to the 3σ of the Maxwell distribution. ,in Represents the root mean square of the velocity. When the probe laser excites the maximum velocity group, at the velocity... When peak transmission occurs, the probe optical detuning is: From the above analysis, the laser frequency value can be obtained at this point. In other words, theoretically, the maximum continuously measurable range of frequency is related to the maximum excitable velocity group of cesium atoms. Finally, on the one hand, based on the conversion relationship between frequency and wavelength, i.e., using the wavelength of the cesium atom transition path as a reference, the detection laser wavelength is determined by analyzing the offset relationship. On the other hand, as an internal reference standard for the wavelengthmeter, the information on the laser frequency deviating from the cesium atom transition frequency is fed back as an error signal to the control terminal of the laser's internal calibration circuit, thereby achieving self-calibration of the wavelengthmeter.

[0037] In summary, the self-calibrating atomic wavelength meter based on saturated absorption spectroscopy and electromagnetically induced transparency spectroscopy provided in this application has the following advantages: (1) By using the energy level transition frequency of cesium atoms as the reference frequency standard, and using the double-peak EIT spectral spacing generated by the Doppler effect of dual-channel excitation to characterize the laser frequency, laser wavelength measurement based on the cesium atom level was realized.

[0038] (2) By feeding back the information that the laser frequency deviates from the transition frequency between hyperfine energy levels of cesium atoms as an error signal to the control terminal of the probe laser, the frequency of the probe laser is tuned to the reference frequency reference, thereby realizing the self-calibration of the wavelength meter.

[0039] The above are merely preferred embodiments of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should be considered within the scope of protection of the present invention.

Claims

1. A self-calibrating atomic wavelength meter, characterized in that, Includes a probe laser (1), a coupling laser (13), a saturated absorption spectrum optical path, and a bimodal spectrum optical path; The probe laser (1) is used to generate the probe laser; The saturated absorption spectrum optical path is used to lock the frequency of the probe laser output by the probe laser (1) on the transition line of the alkali metal atomic energy level based on the saturated absorption spectrum, and to use the transition frequency between atomic energy levels as the reference frequency of the wavelength meter. A coupling laser (13) is used to generate a coupling laser; The dual-peak spectral optical path is used to scan the frequency of the coupling laser (13) after the frequency of the probe laser output by the probe laser (1) is locked by the saturated absorption spectrum. When the probe laser and the coupling laser act together on the alkali metal atom and resonate, an electromagnetically induced transparency effect will be generated. When the probe laser is detuned, the probe laser and the coupling laser act together on the alkali metal atom and non-resonant excitation will be generated, resulting in a dual-peak EIT spectrum with Doppler frequency shift. The dual-peak spectral interval is extracted based on the dual-peak EIT spectrum. Since the dual-peak spectral interval is linearly related to the detuning amount of the probe laser, the wavelength measurement of the current probe laser can be completed based on the extracted dual-peak spectral interval. The dual-peak spectral interval is compared with the transition frequency between atomic energy levels, and the difference between the two is fed back to the control terminal of the probe laser (1) as an error signal. The frequency of the probe laser (1) is tuned to the reference frequency reference, thereby realizing the calibration of the wavelength meter.

2. The self-calibrating atomic wavelength meter according to claim 1, characterized in that, The probe laser (1) outputs a probe laser with a wavelength of 852nm, and the coupling laser (13) outputs a coupling laser with a wavelength of 509nm.

3. The self-calibrating atomic wavelength meter according to claim 1, characterized in that, Both the probe laser (1) and the coupling laser (13) are external cavity semiconductor lasers.

4. The self-calibrating atomic wavelength meter according to claim 1, 2, or 3, characterized in that, The probe laser output by the probe laser (1) passes through the first half-wave plate (2) and reaches the first polarization beam splitter (3). The first polarization beam splitter (3) splits the laser into two probe lasers according to the polarization component: the first probe laser and the second probe laser. The first probe laser is incident on the saturated absorption spectrum optical path, and the second probe laser is incident on the double-peak spectrum optical path.

5. The self-calibrating atomic wavelength meter according to claim 4, characterized in that, The saturated absorption spectrum optical path includes a third beam splitter (22), a fourth reflector (19), a second beam splitter (18), a second atomic gas cell (20), a fifth reflector (21), a second half-wave plate (17), a second polarizing beam splitter prism (16), a third reflector (14), and a balanced photodetector (15). The second atomic gas cell (20) is filled with alkali metal atoms. The first probe laser is incident on the third beam splitter (22) and split into two paths. The laser with most of the optical power is used as the pump light, and the laser with a small portion of the optical power is used as the probe light. The pump light is transmitted through the third beam splitter (22) to the fourth mirror (19), and reflected by the fourth mirror (19) to the second beam splitter (18), and reflected by the second beam splitter (18) to the second atomic gas cell (20). The probe light is reflected by the third beam splitter (22) to the fifth mirror (21), and reflected by the fifth mirror (21) to the second atomic gas cell (20). In this way, the two laser beams incident on the second atomic gas cell (20) propagate collinearly in opposite directions and generate a saturated absorption spectrum that eliminates the Doppler effect in the second atomic gas cell (20). After the weaker probe light passes through the second atomic gas cell (20), it carries the saturation absorption spectrum information and is transmitted through the second beam splitter (18). It is then split into two beams of equal power and perpendicular polarization by the second half-wave plate (17) and the second polarization beam splitter (16). One beam is transmitted through the second polarization beam splitter (16) and reflected by the third mirror (14) and injected into the balanced photodetector (15). The other beam is directly reflected by the second polarization beam splitter (16) and injected into the balanced photodetector (15). The balanced photodetector (15) obtains the saturation absorption spectrum of the cesium atom pair with the probe light by comparing the intensity of the two beams. Based on the saturation absorption spectrum, the laser controller controls the frequency of the probe laser and locks the frequency of the probe laser output by the probe laser on the energy level transition line of the alkali metal atom.

6. The self-calibrating atomic wavelength meter according to claim 4, characterized in that, The dual-peak spectral optical path includes a first reflecting mirror (4), a beam-splitting collimating device (5), a first dichroic mirror (6), a second reflecting mirror (7), a first atomic gas cell (8), a second dichroic mirror (9), a focusing lens (10), a photodetector (11), and a first beam splitter (12). The first atomic gas cell (8) is filled with the same alkali metal atoms as the second atomic gas cell (20). The second detection laser is reflected by the first reflector (4) to the beam splitting collimator (5), and split into two parallel and collimated detection beams, namely detection beam I and detection beam II. The coupled laser output from the coupled laser (13) is split into two beams by the first beam splitter (12): coupled laser I and coupled laser II. The coupled laser I is reflected twice by the second reflector (7) and the first dichroic mirror (6) and propagates in the same direction and collinearly with the probe light I into the first atomic gas cell (8); at the same time, the coupled laser II is reflected by the second dichroic mirror (9) and propagates in the opposite direction and collinearly with the probe light II into the first atomic gas cell (8). After the frequency of the probe laser output by the probe laser (1) is locked by the saturated absorption spectrum, the frequency of the coupled laser is changed by scanning the piezoelectric ceramic voltage of the coupled laser (13). When the probe laser and the coupled laser act together on the alkali metal atoms in the first atomic gas cell (8) and resonate, an electromagnetically induced transparency effect will be generated. When the probe laser is detuned, i.e., non-resonantly excited, a double-peak EIT spectrum with Doppler frequency shift will be generated. The probe light carrying the double-peak EIT spectrum information passes through the first atomic gas cell (8) and is focused by the second dichroic mirror (9) and the focusing lens (10) into the first atomic gas cell. The photodetector (11) converts the light intensity change into an electrical signal, namely the double-peak EIT spectrum curve. By modulating and demodulating the double-peak EIT spectrum curve, the double-peak spectral interval is obtained. Since the double-peak spectral interval is linearly related to the detuning of the probe laser, the wavelength measurement of the current probe laser can be completed based on the extracted double-peak spectral interval. The double-peak spectral interval is compared with the transition frequency between atomic energy levels, and the difference between the two is fed back to the control terminal of the probe laser as an error signal. The frequency of the probe laser is tuned to the reference frequency reference, thereby realizing the calibration of the wavelength meter.

7. The self-calibrating atomic wavelength meter according to claim 6, characterized in that, The first atomic gas chamber (8) and the second atomic gas chamber (20) are filled with cesium atoms or rubidium atoms.

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