Self-calibrating atomic wavemeter

Abstract

A self-calibration atomic wavemeter, including a saturated absorption spectrum optical path based on saturated absorption spectrum to lock the probe laser frequency on cesium atomic energy level transition line; a double-peak spectrum optical path scans the coupling laser frequency after the probe laser frequency is locked by the saturated absorption spectrum, when the probe laser and the coupling laser jointly act on the alkali metal atom and resonantly excite, the electromagnetic induced transparency effect is generated; and when the probe laser is detuned, the probe laser and the coupling laser jointly act on the alkali metal atom to produce non-resonant excitation, and the double-peak EIT spectrum with Doppler frequency shift is generated, based on the linear relationship between the double-peak spectrum interval and the probe laser detuning amount, the wavelength measurement of the current probe laser can be completed, in addition, the double-peak spectrum interval and the atomic energy level transition frequency are compared, and the difference between the two is taken as an error signal feedback to the control end of the probe laser, and the frequency of the probe laser is tuned to the reference frequency benchmark, so that the calibration of the wavemeter can be realized.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of atomic wavemeter, and more particularly relates to a self-calibration atomic wavemeter. BACKGROUND

[0002] Accurate and reliable laser wavelength is a key technology in the field of precision measurement such as atomic clock, atomic gravimeter, atomic magnetometer, etc. Accurate frequency reference is the "ruler" in the field of precision measurement, and has important application prospects in the fields of navigation, verification of basic physical theory and measurement of basic physical constants. The traditional wavemeter relies on high-quality optical elements or precise moving parts, which limits its accuracy and resolution. In addition, the frequency drift of the built-in standard light source and the phase jitter are caused by environmental factors such as mechanical stress and vibration and temperature fluctuation, which requires regular calibration and correction of the reference light source, which affects the accuracy of the measurement results.

[0003] In recent years, based on the absorption spectrum of atoms or molecules such as saturation absorption spectrum (SAS), the transition spectrum of atoms or molecules is used as a frequency ruler, and the specific velocity group atoms are detected by using the pump light and the probe laser in opposite directions, which effectively suppresses the Doppler broadening effect and can obtain the atomic transition spectrum signal close to the natural line width. With its sub-Doppler line width characteristics, inherent frequency traceability and high resolution, it is widely used in optical frequency standard and laser cooling scenes. Although SAS technology has shown significant advantages in laser frequency locking and frequency stabilization, its practical application is still limited by factors such as long-term stability affected by the environment, lack of self-calibration mechanism leading to cumulative frequency offset, etc. SUMMARY

[0004] In order to solve the problem that the accuracy is limited by the frequency drift of the reference light source of the current wavemeter, the present application provides a self-calibration atomic wavemeter. The wavemeter designed by the present application can realize continuous measurement of laser frequency on the basis of real-time self-calibration.

[0005] In order to achieve the above-mentioned purpose, the embodiments of the present application adopt the following technical solutions:

[0006] A self-calibration atomic wavemeter, comprising a probe laser, a coupling laser, a saturation absorption spectrum optical path and a double-peak spectrum optical path;

[0007] The probe laser is used to generate probe laser;

[0008] The saturation absorption spectrum optical path is used to lock the frequency of the probe laser output by the probe laser on the alkali metal atomic energy level transition line based on the saturation absorption spectrum, and the atomic energy level transition frequency is used as the reference frequency standard of the wavemeter;

[0009] The coupling laser is used to generate coupling laser;

[0010] The bimodal spectrum light path is used for scanning the coupling laser frequency after the detection laser frequency output by the detection laser is locked by the saturated absorption spectrum, and when the detection laser and the coupling laser jointly act on the alkali metal atom and resonantly excite, the electromagnetic induced transparency effect is generated; when the detection laser is detuned, the detection laser and the coupling laser jointly act on the alkali metal atom to generate non-resonant excitation, and the bimodal EIT spectrum with Doppler frequency shift is generated, and the bimodal spectrum interval is extracted based on the bimodal EIT spectrum; since the bimodal spectrum interval is linearly related to the detection laser detuning amount, the wavelength measurement of the current detection laser can be completed according to the extracted bimodal spectrum interval; the bimodal spectrum interval is compared with the atomic energy level transition frequency, and the difference between the two is taken as an error signal and fed back to the control end of the detection laser, so that the frequency of the detection laser is tuned to the reference frequency benchmark, thereby realizing the calibration of the wavemeter.

[0011] Further, the alkali metal atom can be a cesium atom or a rubidium atom.

[0012] Further, the detection laser outputs the detection laser with a wavelength of 852 nm.

[0013] Further, the coupling laser outputs the coupling laser with a wavelength of 509 nm.

[0014] The detection laser, the coupling laser, the saturated absorption spectrum light path and the bimodal spectrum light path form a complete self-calibration atomic wavemeter, and the atomic energy level transition frequency of the alkali metal atom is taken as the reference frequency benchmark to realize the measurement and calibration of the laser wavelength.

[0015] As preferred, the detection laser and the coupling laser are both external cavity semiconductor lasers.

[0016] Compared with the prior art, the present application has at least the following beneficial effects:

[0017] The present application designs an atomic transition frequency benchmark method based on saturated absorption spectrum and electromagnetic induced transparency spectrum, which overcomes the problems of the cumulative drift of the frequency of the reference light source built in the traditional wavemeter, the phase jitter and the influence of temperature, and realizes self-calibration. At the same time, according to the quantitative quantitative relationship between the atomic Doppler effect and the bimodal spectrum interval, the continuous measurement of the laser wavelength is realized, the precision can reach MHz, and the maximum measurable range is related to the maximum velocity distribution of the atom. The present application provides a real-time self-calibration, robust and high-precision wavelength measurement solution suitable for various high-precision measurement applications. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to make the technical solutions in the present application or the prior art clearer, the accompanying drawings needed in the embodiments or the prior art description will be briefly introduced. Obviously, the accompanying drawings described below are only some of the embodiments of the present application, and all other embodiments obtained by a person of ordinary skill in the art without any creative effort based on these drawings are within the protection scope of the present application.

[0019] Figure 1 Structure diagram of a self-calibration atomic wavemeter in an embodiment;

[0020] Figure 2 Structure diagram of cesium atom hyperfine energy level in an embodiment;

[0021] Figure 3 Saturated absorption spectrum of cesium atom and spectral diagrams in different cases, wherein Figure 3 (a) is a saturated absorption spectral diagram of cesium atom, Figure 3 (b) is a double-peak spectral diagram showing left detuning, Figure 3 (c) is an EIT spectral diagram produced when resonance excitation occurs, Figure 3 (d) is a double-peak spectral diagram showing right detuning.

[0022] Explanation of reference signs:

[0023] 1, probe laser, 2, first half-wave plate, 3, first polarization beam splitter prism, 4, first mirror, 5, beam-splitting collimating device, 6, first dichroic mirror, 7, second mirror, 8, first atomic gas cell, 9, second dichroic mirror, 10, focusing lens, 11, photodetector, 12, first beam splitter, 13, coupling laser, 14, third mirror, 15, balanced photodetector, 16, second polarization beam splitter prism, 17, second half-wave plate, 18, second beam splitter, 19, fourth mirror, 20, second atomic gas cell, 21, fifth mirror, 22, third beam splitter. DETAILED DESCRIPTION

[0024] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without any creative effort are within the protection scope of the present application.

[0025] In an embodiment, a self-calibration atomic wavemeter is provided, comprising a probe laser, a coupling laser, a saturated absorption spectrum light path and a double-peak spectrum light path.

[0026] The probe laser is used to generate probe laser.

[0027] The saturated absorption spectrum light path is used for locking the detection laser frequency output by the detection laser on the alkali metal atomic energy level transition line based on saturated absorption spectrum, and taking the atomic energy level transition frequency as the reference frequency benchmark of the wavemeter.

[0028] The coupling laser is used for generating coupling laser.

[0029] The double-peak spectrum light path is used for scanning the coupling laser frequency after the detection laser frequency output by the detection laser is locked by the saturated absorption spectrum, and when the detection laser and the coupling laser jointly act on the alkali metal atom and are resonantly excited, the electromagnetic induced transparency effect is generated; when the detection laser is detuned, the detection laser and the coupling laser jointly act on the alkali metal atom to generate non-resonant excitation, and the double-peak EIT spectrum with Doppler frequency shift is generated, the double-peak spectrum interval is extracted based on the double-peak EIT spectrum, since the double-peak spectrum interval is linearly related to the detection laser detuning amount, the wavelength measurement of the current detection laser can be completed according to the extracted double-peak spectrum interval; the double-peak spectrum interval is compared with the atomic energy level transition frequency, and the difference between the two is taken as an error signal and fed back to the control end of the detection laser, so that the frequency of the detection laser is tuned to the reference frequency benchmark, thereby realizing the calibration of the wavemeter.

[0030] Further, the alkali metal atom type is not limited, and can be cesium atom or rubidium atom.

[0031] Further, the saturated absorption spectrum light path takes the alkali metal atomic energy level transition frequency as the reference benchmark, excites the alkali metal atom by using strong pump light and weak probe light, generates the saturated absorption spectrum, locks the detection laser frequency output by the detection laser on the alkali metal atomic energy level transition line based on the saturated absorption spectrum, takes the atomic energy level transition frequency as the reference frequency benchmark of the wavemeter, and realizes laser frequency locking.

[0032] The double-peak spectrum light path is scanned when the frequency of the coupling laser is scanned after the frequency of the probe laser output by the probe laser is locked by the saturated absorption spectrum, and the electromagnetic induced transparency effect is generated when the probe laser and the coupling laser jointly act on the alkali metal atom and resonantly excite. When the probe laser is detuned, the probe laser and the coupling laser jointly act on the alkali metal atom to form non-resonant excitation, and the double-peak electromagnetic induced transparency spectrum (double-peak EIT spectrum) is formed through the Doppler frequency shift effect. The wavelength of the probe laser is measured by using the double-peak spectrum interval, and specifically, the double-peak spectrum interval is linearly related to the detuning amount of the probe laser. The wavelength of the current probe laser can be measured according to the extracted double-peak spectrum interval. In addition, the double-peak spectrum interval is compared with the atomic energy level transition frequency, and the difference between the two is used as an error signal to be fed back to the control end of the probe laser, so that the frequency of the probe laser is tuned to the reference frequency benchmark, thereby realizing the calibration of the wavemeter. In this way, the alkali metal atom transition frequency is used as the reference frequency benchmark, and the double-peak spectrum interval represents the laser wavelength, thereby overcoming the frequency drift of the reference light source built in the traditional wavemeter and realizing the continuous measurement of the wavelength of the probe laser based on the self-calibration of the atomic transition frequency.

[0033] Reference Figure 1 An embodiment provides a self-calibration atomic wavemeter based on saturated absorption spectrum and electromagnetic induced transparency spectrum, which comprises a probe laser 1, a first half-wave plate 2, a first polarization beam splitter prism 3, a first mirror 4, a beam splitting collimating device 5, a first dichroic mirror 6, a second mirror 7, a first atomic 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 mirror 14, a balanced photodetector 15, a second polarization beam splitter prism 16, a second half-wave plate 17, a second beam splitter 18, a fourth mirror 19, a second atomic cell 20, a fifth mirror 21, and a third beam splitter 22. The first atomic cell 8 is filled with the same alkali metal atom as the second atomic cell 20, and the alkali metal atom used in this embodiment is cesium atom.

[0034] The probe laser output by the probe laser 1 reaches the first polarization beam splitter prism 3 through the first half-wave plate 2, and the first polarization beam splitter prism 3 divides the laser into two beams of probe laser according to the polarization component, that is, the first probe laser and the second probe laser. The first probe laser is incident to the saturated absorption spectrum light path, and the second probe laser is incident to the double-peak spectrum light path.

[0035] The saturated absorption spectrum light path comprises the third beam splitter 22, the fourth mirror 19, the second beam splitter 18, the second atomic cell 20, the fifth mirror 21, the second half-wave plate 17, the second polarization beam splitter prism 16, the third mirror 14, and the balanced photodetector 15.

[0036] The first probe laser reflected from the first polarization beam splitter prism 3 is incident on the third beam splitter 22, and is split into two beams by the third beam splitter 22, wherein the laser with most of the optical power is split as pump light, and the laser with a small part of the optical power is split as probe light; the pump light is transmitted through the third beam splitter 22 to the fourth mirror 19, is reflected by the fourth mirror 19 to the second beam splitter 18, and is reflected by the second beam splitter 18 to the second atomic cell 20; the probe light is reflected by the third beam splitter 22 to the fifth mirror 21, and is reflected by the fifth mirror 21 to the second atomic cell 20; in this way, the two lasers incident on the second atomic cell 20 are co-linear and counter-propagating, and a Doppler-effect-eliminated saturated absorption spectrum is generated in the second atomic cell 20 by the counter-propagation; after passing through the second atomic cell 20, the probe light with weak power carries the saturated absorption spectrum information, and is transmitted through the second beam splitter 18, and then passes through the second half-wave plate 17 and the second polarization beam splitter prism 16 to be split into two beams of equal power and vertical polarization; one of the two beams is transmitted by the second polarization beam splitter prism 16, is reflected by the third mirror 14, and is injected into the balanced photodetector 15; the other beam is directly reflected by the second polarization beam splitter prism 16 and is injected into the balanced photodetector 15; the balanced photodetector 15 cancels the direct current bias of the photocurrent, and obtains the saturated absorption spectrum of the cesium atom; based on the saturated absorption spectrum, the laser controller controls the frequency of the probe laser 1, and locks the frequency of the probe laser output by the probe laser 1 on the cesium atom energy level transition line.

[0037] The double-peak spectral light path comprises a first mirror 4, a beam splitting collimating device 5, a first dichroic mirror 6, a second mirror 7, a first atomic cell 8, a second dichroic mirror 9, a focusing lens 10, a photodetector 11, and a first beam splitter 12.

[0038] The second probe laser transmitted through the first polarization beam splitter prism 3 is reflected by the first mirror 4 to the beam splitting collimating device 5, and is split into two parallel and collimated probe lights, namely probe light I and probe light II;

[0039] The coupling laser output by the coupling laser 13 is equally divided into two beams, namely coupling laser I and coupling laser II, by the first beam splitter 12.

[0040] The coupling laser I is reflected by the second mirror 7 and the first dichroic mirror 6 twice, and enters the first atomic cell 8 in a co-linear and same-direction transmission together with the probe light I; at the same time, the coupling laser II is reflected by the second dichroic mirror 9, and counter-propagates in a co-linear transmission together with the probe light II in the first atomic cell 8.

[0041] The detection laser frequency outputted by the detection laser 1 is locked by the saturated absorption spectrum, and the piezoelectric ceramic voltage of the coupling laser 13 is controlled to change the coupling laser frequency. When the detection laser and the coupling laser jointly act on the alkali metal atoms in the first atomic cell 8 and are resonantly excited, the electromagnetic induced transparency effect is generated, i.e. the frequencies of the detection laser and the coupling laser are not detuned. However, due to the influence of environmental factors such as mechanical stress, vibration, temperature fluctuation, etc., when the detection laser is detuned, the detection laser and the coupling laser jointly act on the alkali metal atoms to generate non-resonant excitation, and the double-peak EIT spectrum with Doppler frequency shift is generated. The detection light carrying the double-peak EIT spectrum information passes through the first atomic cell 8, the second dichroic mirror 9 and the focusing lens 10, and enters the photodetector 11. The photodetector 11 converts the light intensity change into an electrical signal, i.e. 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 detection laser, the wavelength of the current detection laser can be measured according to the extracted double-peak spectral interval. The difference between the double-peak spectral interval and the atomic energy level transition frequency is compared, and the difference is used as an error signal to feedback to the control end of the detection laser, so as to tune the frequency of the detection laser to the reference frequency benchmark, thereby realizing the calibration of the wavemeter.

[0042] Preferably, in the above embodiment, the detection laser 1 outputs detection laser with a wavelength of 852 nm, the coupling laser 13 outputs coupling laser with a wavelength of 509 nm, and the double-peak spectral light path generates double-peak electromagnetic induced transparency spectrum (EIT) by using 852 nm detection laser and 509 nm coupling laser excitation mode.

[0043] Preferably, the detection laser 1 and the coupling laser 13 are both external cavity semiconductor lasers. The power supply of the external cavity semiconductor laser integrates a temperature module, a current module, a piezoelectric ceramic transducer (PZT) and a frequency stabilization module, wherein the temperature, current and PZT can all tune the laser frequency.

[0044] When the detection laser frequency of the double-peak spectral light path is locked on the hyperfine energy level transition, the offset amount caused by frequency jitter is used as an error signal to feedback to the control end of the detection laser, so as to realize the offset calibration.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] In the second atomic cell 20 of the saturated absorption spectrum optical path, strong pump light and weak probe light are used to excite the cesium atoms in the second atomic cell 20, and according to the Doppler broadening and Figure 1 In the middle direction, the speed of cesium atoms, which feel the frequency of the probe light, is , wherein is the wavelength of the laser, is the wave vector, is the frequency of the probe light, is the frequency of the probe light felt by the atom. When , the probe light will be absorbed, and , that is, the probe light is absorbed by the cesium atom group with a speed , and the detuning frequency is defined, wherein is the atomic level transition frequency; correspondingly, the pump light is absorbed by the cesium atom group with a speed . The two beams of light interact with different speed groups of cesium atoms, and the probe light is very weak, and the proportion of absorption is proportional to the number of cesium atoms in the speed group , so the absorption spectrum presents an inverted Maxwell velocity distribution ( ). When , , the probe light and the pump light are both absorbed by the cesium atom group with a speed of 0. Because the pump light is relatively strong, most of the cesium atoms with a speed of 0 are consumed, and the absorption reaches saturation, the transmission intensity of the probe light rises sharply, and a sharp spectral line is presented, forming a saturated absorption peak ( ). On the basis of the above analysis, considering the multi-level system, in the three-level model, the cesium atom level transition frequency has two, which are , , is the transition frequency of the first transition path of the cesium atom, is the transition frequency of the second transition path of the cesium atom, and . Therefore, when , , a saturated absorption peak will also be generated, which is called a cross spectrum. Taking as an example (according to the transition selection rule ΔF=0,±1), in addition to the three intrinsic spectrum lines, three cross spectrum lines will be generated, which are: . The intrinsic spectrum line and the cross spectrum line superimpose to form a complete saturated absorption spectrum, which is used as a reference for laser frequency locking to generate an EIT spectrum signal.

[0049] The double-peak EIT spectrum excited by double channels is obtained by scanning the coupling laser when the frequency of the probe laser is locked by the overlapping of two lasers according to the saturated absorption spectrum. When the frequency of the probe laser is locked at , a peak curve is obtained due to resonance excitation. That is, the frequencies of the probe laser and the coupling laser are not detuned, so the main effect is EIT. However, due to the influence of environmental factors such as mechanical stress, vibration, and temperature fluctuation, the frequency of the probe laser will be accumulatedly shifted, and the frequency of the probe laser will be detuned . In the same direction transmission, the double-peak EIT spectrum is generated due to the Doppler effect caused by the frequency shift, and the interval of the double-peak spectrum is proportional to the detuning amount of the frequency of the probe laser.

[0050] The theory can be analyzed by the following model. Considering the same direction transmission and the reverse direction transmission of the probe laser and the coupling laser, it is assumed that the +z direction is defined as the direction of the probe laser transmitted to the PD, and the velocity of the cesium atom is For the reverse direction transmission of the probe light I and the coupling laser I, the corrected laser detuning is and respectively when the frequency of the probe light is detuned, where is the corrected detuning amount of the probe light, is the uncorrected detuning amount of the probe light, is the velocity of the cesium atom, is the wavelength of the probe light, is the corrected detuning amount of the coupling light, is the uncorrected detuning amount of the coupling light, is the wavelength of the coupling light. For resonance excitation, , the following can be obtained . Similarly, the probe light II and the coupling laser beam II are co-transmitted, . When the probe light I and the probe light II are transmitted in the same direction, the frequency of the probe laser is detuned . Therefore, the difference between the two peaks (i.e. the interval of the double-peak spectrum) , that is, the difference between the peaks is proportional to the detuning of the frequency of the probe laser, and the factor is . This shows that a small frequency shift can be easily captured by the EIT spectrum, which is a super-precise method for measuring the frequency (i.e. wavelength) of the laser based on cesium atoms.

[0051] In addition, the velocity distribution of the cesium atom follows the Maxwell-Boltzmann distribution where k B is the Boltzmann constant, m is the mass of the cesium atom, T is the thermodynamic temperature (300 K). The maximum velocity corresponding to 3σ of the Maxwell distribution is ,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.

[0052] 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:

[0053] (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.

[0054] (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.

[0055] 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 a probe laser. The probe laser is split into two beams, a first probe laser and a 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. The saturated absorption spectrum optical path includes a third beam splitter (22), a fourth mirror (19), a second beam splitter (18), a second atomic gas cell (20), a fifth mirror (21), a second half-wave plate (17), a second polarizing beam splitter prism (16), a third mirror (14), and a balanced photodetector (15). The second atomic gas cell (20) is filled with alkali metal atoms. The first detection laser is incident on the third beam splitter (22) and split into two paths, one of which has a polarizing effect. A large portion of the laser's optical power is used as the pump light, while a smaller portion of the split laser's optical power is used as the probe light. The pump light is transmitted through the third beam splitter (22) to the fourth mirror (19), reflected by the fourth 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 mirror (21), and then reflected by the fifth mirror (21) to the second atomic gas cell (20). Thus, the two beams... The laser beams incident on the second atomic gas chamber (20) propagate in the opposite direction in a collinear manner, and generate a saturated absorption spectrum that eliminates the Doppler effect by transmitting in opposite directions within the second atomic gas chamber (20). The weaker probe light passes through the second atomic gas chamber (20), carries the saturated 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) cancels the DC bias of the photocurrent and obtains the saturated absorption spectrum of the cesium atom pair probe light. Based on the saturated absorption spectrum, the laser controller locks the frequency of the probe laser output by the probe laser on the transition line of the alkali metal atomic energy level and uses 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 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 probe laser is reflected by the first reflecting mirror (4) to the beam-splitting collimating device (5), splitting into two parallel and collimated probe beams, namely probe beam I and probe beam II. The coupled laser output from the laser (13) is split into two beams, coupled laser I and coupled laser II, by the first beam splitter (12). 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, 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). The frequency of the probe laser output from the probe laser (1) is locked by the saturated absorption spectrum and then scanned by the piezoelectric ceramic of the coupled laser (13). The pressure is used to change the frequency of the coupling laser. When the probe laser and the coupling 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 becomes detuned, the probe laser and the coupling 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) 1) Convert the light intensity change into an electrical signal, namely the double-peak EIT spectrum curve. Modulate and demodulate the double-peak EIT spectrum curve to obtain the double-peak spectral interval. 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. Compare the double-peak spectral interval with the transition frequency between atomic energy levels, and use the difference between the two as an error signal to feed back to the control terminal of the probe laser (1). Tune the frequency of the probe laser (1) to the reference frequency reference to achieve 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.

5. The self-calibrating atomic wavelength meter according to claim 4, 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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