CN113113843B - Coupled dual-wavelength laser frequency stabilization optical circuit system and method based on polarization spectroscopy - Google Patents

Abstract

The present application relates to a coupled dual-wavelength laser frequency stabilization optical circuit system and method based on polarization spectroscopy. The first half-wave plate is arranged on the optical path of the first laser. The first polarization beam splitting prism is arranged on the optical path of the first laser light after passing through the first half-wave plate, and is used for dividing the first laser light into probe light and pump light. The chopper is arranged on the optical path of the pump light. The quarter wave plate is arranged on the optical path of the pump light after the chopper. The dichroic mirror is arranged on the optical path of the pump light after the quarter-wave plate and on the optical path of the second laser, and is used to combine the pump light and the second laser to form a combined beam . The hollow cathode lamp is arranged on the optical path of the combined beam and on the optical path of the detection light. The intersection of the combined beam and the probe light is at the center of the hollow cathode lamp. The second half-wave plate is arranged on the optical path of the probe light after passing through the hollow cathode lamp. The photodetector is arranged on the optical path of the detection light after passing through the second half-wave plate.

Description

Coupled dual-wavelength laser frequency stabilization optical circuit system and method based on polarization spectroscopy

technical field

The present application relates to the field of laser technology, in particular to a coupled dual-wavelength laser frequency stabilization optical path system and method based on polarization spectroscopy.

Background technique

The stability of laser frequency is crucial in many fields such as atomic physics, quantum computing, and precision measurement. Among them, laser cooling and state preparation in ion trapping experiments require light of a specific frequency, and the laser frequency stability is required to be high, and a frequency stabilization system needs to be established to obtain the corresponding laser. For the jitter and drift of the laser frequency due to environmental factors such as temperature, pressure, vibration, etc., a stable absolute frequency can generally be used as a reference, such as the transition lines of atoms or molecules. Or use a calibrated relative frequency as a reference, such as an optical cavity or an interferometer in a wavelength meter. The saturable absorption spectrum stabilization technique locks the laser to a specific transition line of an atom or molecule. The frequency error signal is obtained through modulation and demodulation, and the laser is fed back and locked by the signal. The frequency stabilization of the wavelength meter is to compare the self-set frequency with the measured data, obtain the error signal, and lock the laser.

The saturable absorption spectrum frequency stabilization performance depends on the signal-to-noise ratio of the saturable absorption spectrum signal. The size of the signal is related to the transition rate of molecules or atoms, the number of molecules or atoms involved in the interaction, and so on. In general, the faster the transition rate of a molecule or atom and the more particles participating in the interaction, the stronger the signal will be. However, due to collisions between particles, collision broadening and frequency shift will result, which will broaden the signal spectrum. Moreover, the saturable absorption spectrum frequency stabilization method requires frequency modulation of the laser, which will bring additional frequency noise, reduce the signal-to-noise ratio of the signal, and have a greater impact on the laser at the ultraviolet wavelength. For the lower energy level of the ion metastable level transition line, the number of ions at that energy level is very small because it is generated by spontaneous emission from other energy levels. Therefore, the spectral line signal of this energy level transition is very weak. Using standard spectral techniques, it is impossible to directly obtain the absorption spectrum signal and lock the laser of the corresponding wavelength. The traditional technology adopts the FP cavity frequency stabilization system. However, the anti-interference ability of the FP cavity frequency stabilization system is poor, and the selected frequency standard is easily affected by the laser power jitter, resulting in poor frequency stabilization performance.

SUMMARY OF THE INVENTION

Based on this, it is necessary to provide a coupled dual-wavelength laser frequency stabilization optical circuit system and method based on polarization spectroscopy to address the above problems.

The present application provides a coupled dual-wavelength laser frequency stabilization optical circuit system based on polarization spectroscopy. The coupled dual-wavelength laser frequency stabilization optical circuit system based on polarization spectroscopy includes a first laser, a first half-wave plate, a first polarization beam splitter prism, a chopper, a quarter-wave plate, a second laser, a dichroic Chromatic mirror, hollow cathode lamp, second half-wave plate and photodetector. The first laser is used to emit first laser light. The first half-wave plate is disposed on the optical path of the first laser. The first polarization beam splitting prism is disposed on the optical path of the first laser light after passing through the first half-wave plate, and is used for dividing the first laser light into probe light and pump light. The chopper is arranged on the optical path of the pump light. The quarter wave plate is arranged on the optical path of the pump light after the chopper. The second laser is used for emitting a second laser light. The dichroic mirror is arranged on the optical path of the pump light after passing through the quarter-wave plate, and is arranged on the optical path of the second laser, and is used for combining the pump light with the pump light. The second laser beams are combined to form combined beams. The hollow cathode lamp is arranged on the optical path of the combined beam and on the optical path of the detection light. The intersection point of the combined beam and the probe light is at the center of the hollow cathode lamp. The second half-wave plate is arranged on the optical path of the probe light after passing through the hollow cathode lamp. The photodetector is arranged on the optical path of the detection light after passing through the second half-wave plate.

In one embodiment, the coupled dual-wavelength laser frequency stabilization optical circuit system based on polarization spectroscopy further includes a lock-in amplifier and a first PI control circuit. The signal input end of the lock-in amplifier is connected with the photodetector.

The signal input end of the first PI control circuit is connected to the first signal output end of the lock-in amplifier. The signal output end of the first PI control circuit is connected to the signal control end of the first laser.

In one embodiment, the coupled dual-wavelength laser frequency stabilization optical circuit system based on polarization spectroscopy further includes a second PI control circuit. The signal input end of the second PI control circuit is connected to the second signal output end of the lock-in amplifier, and the signal output end of the second PI control circuit is connected to the signal control end of the second laser.

In one embodiment, the coupled dual-wavelength laser frequency stabilization optical path system based on polarization spectroscopy further includes a second polarization beam splitting prism. The second polarization beam splitting prism is disposed on the optical path of the probe light after passing through the second half-wave plate, and is used for dividing the probe light into a first polarization probe light and a second polarization probe light.

In one embodiment, the photodetectors include a first balanced photodetector and a second balanced photodetector. The first balanced photodetector is arranged on the optical path of the first polarized detection light. The second balanced photodetector is arranged on the optical path of the second polarized detection light.

In one embodiment, the coupled dual-wavelength laser frequency stabilization optical path system based on polarization spectroscopy further includes a glass window. The glass window is arranged on the optical path of the first laser light, and is used for separating part of the laser light from the first laser light for wavelength detection.

In one embodiment, the coupled dual-wavelength laser frequency stabilization optical circuit system based on polarization spectroscopy further includes a first isolator. The first isolator is disposed on the optical path of the first laser. And the first isolator is arranged between the first laser and the glass window.

In one embodiment, the coupled dual-wavelength laser frequency stabilization optical path system based on polarization spectroscopy further includes a third polarization beam splitter prism. The third polarized beam splitter prism is arranged on the optical path of the second laser light, and is used for separating part of the laser light from the second laser light for wavelength detection.

In one embodiment, the coupled dual-wavelength laser frequency stabilization optical circuit system based on polarization spectroscopy further includes a second isolator. The second isolator is disposed on the optical path of the second laser. And the second isolator is arranged between the second laser and the third polarization beam splitter prism.

In one embodiment, the present application provides a frequency stabilization method for a coupled dual-wavelength laser frequency stabilization optical circuit system based on polarization spectroscopy, using the polarization spectroscopy-based coupled dual-wavelength laser in any of the foregoing embodiments Frequency stabilization optical path system for frequency stabilization.

In the above-mentioned system and method for frequency stabilization of coupled dual-wavelength laser light based on polarization spectroscopy, the first polarization beam splitting prism divides the first laser light into probe light and pump light. The power of the probe light is relatively weak and is linearly polarized light. The power of the pump light is relatively strong. The pump light becomes circularly polarized light after amplitude modulation after passing through the chopper and the quarter-wave plate in sequence. The pump light and the second laser light after passing through the quarter-wave plate are combined at the dichroic mirror to form the combined light.

The hollow cathode lamp is arranged on the optical path of the combined beam and on the optical path of the detection light. The hollow cathode lamp emits a sharp light source, which satisfies the conditions of atomic absorption spectrometry. The intersection point of the combined beam and the probe light is at the center of the hollow cathode lamp. Stronger pump light causes dichroism in the medium of the hollow cathode lamp. That is, the absorption coefficients of the medium to the left-handed and right-handed circularly polarized components of the probe light are different. If the strong pump light is left-handed circularly polarized light, the energy level will saturate the absorption of left-handed circularly polarized light, but the spontaneous emission of the high energy level will return to these three sub-levels evenly, which will cause the difference in the number of ions in the sub-levels. , so that the two circularly polarized components of the linearly polarized probe light are absorbed differently. If the stronger pump light is right-handed circularly polarized light, the principle is the same as that of left-handed circularly polarized light.

The stronger pump light saturates the corresponding energy level transitions of the ions in the hollow cathode lamp. Because the weaker probe light is linearly polarized light, it can be divided into two components: left-handed circularly polarized light and right-handed circularly polarized light. Due to the existence of the strong pump light, the ions in the hollow cathode lamp have differences in the absorption of the left-handed and right-handed circularly polarized light components. The second half-wave plate is arranged on the optical path of the probe light after passing through the hollow cathode lamp. The photodetector is arranged on the optical path of the detection light after passing through the second half-wave plate. The detection light after passing through the hollow cathode lamp is detected and decomposed by the photodetector after passing through the second half-wave plate. The phase and amplitude of the two light components of the left-handed and right-handed circularly polarized lights in the detection light detected by the photodetector are different, and a frequency discrimination signal for locking the laser can be obtained.

Therefore, the coupled dual-wavelength laser frequency stabilization optical circuit system based on polarization spectroscopy is based on the principle of polarization spectroscopy, and can simultaneously lock lasers of two wavelengths at different energy levels of the same ion. After the second laser beam corresponding to the transition wavelength of the metastable energy level and the strong pump light are combined, the metastable energy level and the upper energy level (the high energy level of the metastable state corresponding to the first laser beam) are passed through. There is a coupling relationship between the two wavelengths of laser light and different frequencies are modulated respectively, and the corresponding error frequency discrimination signal can be demodulated separately for laser frequency stabilization.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application or in the traditional technology, the following briefly introduces the accompanying drawings that are used in the description of the embodiments or the traditional technology. Obviously, the drawings in the following description are only the For some embodiments of the application, for those of ordinary skill in the art, other drawings can also be obtained according to these drawings without any creative effort.

FIG. 1 is a schematic diagram of the overall structure of a coupled dual-wavelength laser frequency stabilization optical circuit system based on polarization spectroscopy in one embodiment of the present application.

FIG. 2 is a schematic diagram of the overall structure of a coupled dual-wavelength laser frequency stabilization optical circuit system based on polarization spectroscopy in another embodiment provided by the present application.

Description of reference numbers:

Coupled dual-wavelength laser frequency stabilization optical circuit system 100 based on polarization spectroscopy, first laser 110, first half-wave plate 140, first polarization beam splitting prism 150, chopper 170, quarter-wave plate 180, second Laser 210, dichroic mirror 30, hollow cathode lamp 40, second half-wave plate 60, photodetector 90, lock-in amplifier 520, first PI control circuit 510, second PI control circuit 530, second polarization beam splitter Prism 70 , first balanced photodetector 910 , second balanced photodetector 920 , glass window 130 , first isolator 120 , third polarizing beam splitter prism 230 , second isolator 220 , first fiber coupling head 320 , a first optical fiber 330 , a second optical fiber coupling head 420 , and a second optical fiber 430 .

Detailed ways

In order to make the above objects, features and advantages of the present application more clearly understood, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

The terms "first" and "second" are only used for descriptive purposes, and should not be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature delimited with "first", "second" may expressly or implicitly include at least one of that feature. In the description of the present application, "plurality" means at least two, such as two, three, etc., unless expressly and specifically defined otherwise.

Referring to FIG. 1 , the present application provides a coupled dual-wavelength laser frequency stabilization optical circuit system 100 based on polarization spectroscopy. The coupled dual-wavelength laser frequency stabilization optical circuit system 100 based on polarization spectroscopy includes a first laser 110, a first half-wave plate 140, a first polarization beam splitting prism 150, a chopper 170, a quarter-wave plate 180, The second laser 210 , the dichroic mirror 30 , the hollow cathode lamp 40 , the second half-wave plate 60 and the photodetector 90 . The first laser 110 is used for emitting first laser light. The second laser 210 is used for emitting second laser light. The wavelength of the first laser light and the wavelength of the second laser light are different.

The first half-wave plate 140 is disposed on the optical path of the first laser. It can be understood that, after the first laser is emitted through the first laser 110 , it is irradiated to the first half-wave plate 140 , and continues to be transmitted after passing through the first half-wave plate 140 . The first polarization beam splitting prism 150 is disposed on the optical path of the first laser light after passing through the first half-wave plate 140 , and is used for dividing the first laser light into probe light and pump light.

The chopper 170 is disposed on the optical path of the pump light. The chopper 170 is an optical chopper, and it can be understood that the pump light is incident on the chopper 170 , and then undergoes amplitude modulation after passing through the chopper 170 . The quarter wave plate 180 is disposed on the optical path of the pump light after the chopper 170 . It can be understood that the pump light after passing through the chopper 170 is incident on the quarter-wave plate 180 and continues to transmit after passing through the quarter-wave plate 180 .

The dichroic mirror 30 is arranged on the optical path of the pump light after passing through the quarter wave plate 180, and is arranged on the optical path of the second laser, for converting the pump light and the second laser beam is combined to form combined beam light. The first polarization beam splitter prism 150 divides the first laser light into probe light and pump light. The power of the probe light is relatively weak and is linearly polarized light. The power of the pump light is relatively strong. The pump light becomes circularly polarized light after amplitude modulation after passing through the chopper 170 and the quarter-wave plate 180 in sequence. The pump light and the second laser light after passing through the quarter-wave plate 180 are combined at the dichroic mirror 30 to form the combined light.

The hollow cathode lamp 40 is disposed on the optical path of the combined beam and on the optical path of the detection light. The hollow cathode lamp 40 emits a sharp light source, which satisfies the conditions of atomic absorption spectrometry. The intersection of the combined beam and the probe light is at the center of the hollow cathode lamp 40 . It can be understood that the combined beam and the detection light intersect and overlap at the center of the hollow cathode lamp 40 . Stronger pump light causes dichroism in the medium of the hollow cathode lamp 40 . That is, the absorption coefficients of the medium to the left-handed and right-handed circularly polarized components of the probe light are different. If the strong pump light is left-handed circularly polarized light, the absorption of the left-handed circularly polarized light will be saturated at this energy level, but the spontaneous emission of the high energy level will return to these three sub-levels evenly, which will cause the difference in the number of ions in the sub-levels. , so that the two circularly polarized components of the linearly polarized probe light are absorbed differently. If the stronger pump light is right-handed circularly polarized light, the principle is the same as that of left-handed circularly polarized light.

The stronger pump light saturates the corresponding energy level transitions of the ions in the hollow cathode lamp 40 . Because the weaker probe light is linearly polarized light, it can be divided into two components: left-handed circularly polarized light and right-handed circularly polarized light. Due to the existence of the strong pump light, the ions in the hollow cathode lamp 40 have differences in the absorption of the left-handed and right-handed circularly polarized light components. The second half-wave plate 60 is disposed on the optical path of the probe light after passing through the hollow cathode lamp 40 . The photodetector 90 is disposed on the optical path of the detection light after passing through the second half-wave plate 60 . The detection light after passing through the hollow cathode lamp 40 is detected and decomposed by the photodetector 90 after passing through the second half-wave plate 60 . The phase and amplitude of the two light components of the left-handed and right-handed circularly polarized light detected by the photodetector 90 are different, and a frequency discrimination signal for locking the laser can be obtained.

In this embodiment, the coupled dual-wavelength laser frequency stabilization optical circuit system 100 based on polarization spectroscopy is based on the principle of polarization spectroscopy, and can simultaneously lock lasers of two wavelengths at different energy levels of the same ion. After the second laser beam corresponding to the transition wavelength of the metastable energy level and the strong pump light are combined, the metastable energy level and the upper energy level (the high energy level of the metastable state corresponding to the first laser beam) are passed through. There is a coupling relationship between the two wavelengths of laser light and different frequencies are modulated respectively, and the corresponding error frequency discrimination signal can be demodulated separately for laser frequency stabilization.

In one embodiment, the coupled dual-wavelength laser frequency stabilization optical path system 100 based on polarization spectroscopy further includes a second polarization beam splitting prism 70 . The second polarization beam splitter prism 70 is disposed on the optical path of the probe light after passing through the second half-wave plate 60, and is used to divide the probe light into a first polarization probe light and a second polarization probe light .

In this embodiment, the probe light after passing through the hollow cathode lamp 40 passes through the second half-wave plate 60 and the second polarizing beam splitter prism 70 respectively, so that the probe light can be decomposed, respectively. The first polarized probe light and the second polarized probe light are formed. The first polarized probe light and the second polarized probe light are two light components of two circularly polarized lights of left-hand rotation and right-hand rotation, respectively, so that a frequency discrimination signal for locking the laser can be obtained.

In one embodiment, the photodetector 90 includes a first balanced photodetector 910 and a second balanced photodetector 920 . The first balanced photodetector 910 is disposed on the optical path of the first polarized detection light. The second balanced photodetector 920 is disposed on the optical path of the second polarized detection light.

In this embodiment, the first polarized detection light and the second polarized detection light formed after being split by the second polarized beam splitting prism 70 are respectively transmitted by the first balanced photodetector 910 and the second polarized detection light. Two balanced photodetectors 920 detect. The difference between the signals detected by the first balanced photodetector 910 and the second balanced photodetector 920 can be obtained to obtain the difference between the two components.

In one embodiment, the photodetector 90 may also be a differential detector. The first polarized probe light and the second polarized probe light formed after being split by the second polarization beam splitting prism 70 are respectively detected by the differential detector, and subjected to difference by the differential detector to obtain: The difference between the two components has a line type of a dispersion-like signal, which can be directly used for laser frequency stabilization.

Referring to FIG. 2 , in an embodiment, the coupled dual-wavelength laser frequency stabilization optical circuit system 100 based on polarization spectroscopy further includes a lock-in amplifier 520 and a first PI control circuit 510 . The signal input end of the lock-in amplifier 520 is connected to the photodetector 90 .

The signal input end of the first PI control circuit 510 is connected to the first signal output end of the lock-in amplifier 520 . The signal output terminal of the first PI control circuit 510 is connected to the signal control terminal of the first laser 110 .

In this embodiment, the first laser light emitted by the first laser 110 is subjected to amplitude modulation after passing through the chopper 170 . The second laser light emitted by the second laser 210 is subjected to high-frequency current modulation. The first laser signal after amplitude modulation and the second laser signal after high-frequency current modulation are respectively connected to the lock-in amplifier 520 with the corresponding reference signal, and are demodulated by phase-sensitive detection (reference signal and modulation signal). After signal multiplication) and low-pass filtering, the frequency discrimination error signals of the first laser 110 and the second laser 210 are obtained respectively.

The demodulation principle of the lock-in amplifier 520 is that the modulated signal obtained by the photodetector 90 is multiplied by the reference signal of the same frequency, and the product and difference transformation of the trigonometric function is carried out to obtain a high frequency AC part, DC part and noise. And filter out the high frequency signal and noise through the low-pass filter, and then obtain the required DC signal part.

The first PI control circuit 510 refers to a proportional-integral control circuit. The first PI control circuit 510 operates the frequency discrimination error signal converted by the lock-in amplifier 520 to obtain a first control signal. The first control signal acts on the first laser 110 . By adjusting the proportional and integral parameters by the first PI control circuit 510, the fastness of the frequency locking can be optimized, so that the laser frequency deviation from the locking value can be quickly recovered to the locking value, and the steady-state error of the locking can also be reduced, so that all the The above-described coupled dual-wavelength laser frequency stabilization optical circuit system 100 based on polarization spectroscopy is more stable.

In one embodiment, the second laser emitted by the second laser 210 is modulated by a high frequency current of 100KHz.

In one embodiment, the coupled dual-wavelength laser frequency stabilization optical circuit system 100 based on polarization spectroscopy further includes a second PI control circuit 530 . The signal input end of the second PI control circuit 530 is connected to the second signal output end of the lock-in amplifier 520 , and the signal output end of the second PI control circuit 530 is connected to the signal control end of the second laser 210 connect.

In this embodiment, the second PI control circuit 530 refers to a proportional-integral control circuit. The second PI control circuit 530 operates the frequency discrimination error signal converted by the lock-in amplifier 520 to obtain a second control signal. The second control signal acts on the second laser 210 . The second PI control circuit 530 adjusts the proportional and integral parameters, which can optimize the fastness of the frequency locking, so that the laser frequency deviating from the locking value can quickly recover to the locking value, and can also reduce the steady-state error of the locking, thereby making the The coupled dual-wavelength laser frequency stabilization optical circuit system 100 based on polarization spectroscopy is more stable.

In one embodiment, the coupled dual-wavelength laser frequency stabilization optical circuit system 100 based on polarization spectroscopy further includes a glass window 130 . The glass window 130 is disposed on the optical path of the first laser light, and is used to separate a part of the laser light from the first laser light for wavelength detection.

In this embodiment, part of the laser light is split from the first laser light through the glass window 130, incident on the first fiber coupling head 320, and coupled into the wavelength meter through the first fiber 330 for observing the first laser light. wavelength of a laser.

In one embodiment, the coupled dual-wavelength laser frequency stabilization optical circuit system 100 based on polarization spectroscopy further includes a first isolator 120 . The first isolator 120 is disposed on the optical path of the first laser. And the first isolator 120 is disposed between the first laser 110 and the glass window 130 .

In this embodiment, the first isolator 120 is used to prevent the backward transmission light in the optical path of the first laser from adversely affecting the first laser 110 and the entire optical path system. Furthermore, the first isolator 120 can largely reduce the adverse effect of the backward transmitted light on the stability of the spectral output power of the first laser 110, so that the coupled dual-wavelength polarization spectroscopy-based The laser frequency stabilization optical path system 100 is more stable.

In one embodiment, the coupled dual-wavelength laser frequency stabilization optical circuit system 100 based on polarization spectroscopy further includes a third polarization beam splitting prism 230 . The third polarizing beam splitting prism 230 is disposed on the optical path of the second laser light, and is used for separating part of the laser light from the second laser light for wavelength detection.

In this embodiment, part of the laser light split from the second laser light by the third polarization beam splitter prism 230 is incident on the second fiber coupling head 420, and is coupled into the wavelength meter through the second fiber 430, which is used for The wavelength of the second laser light is detected.

In one embodiment, the coupled dual-wavelength laser frequency stabilization optical circuit system 100 based on polarization spectroscopy further includes a second isolator 220 . The second isolator 220 is disposed on the optical path of the second laser. And the second isolator 220 is disposed between the second laser 210 and the third polarizing beam splitting prism 230 .

In this embodiment, the second isolator 220 is used to prevent the backward propagation light in the optical path of the second laser from adversely affecting the second laser 210 and the entire optical path system. Furthermore, the second isolator 220 can largely reduce the adverse effect of the backward transmitted light on the stability of the spectral output power of the second laser 210, so that the coupled dual-wavelength polarization spectroscopy-based The laser frequency stabilization optical path system 100 is more stable.

In one embodiment, the transition wavelengths corresponding to the ² S _1/2 - ² P _1/2 energy level and the ² D _3/2 - ³ D[3/2] _1/2 energy level of the ytterbium ion are 369.5 nm and 935.18, respectively nm. where ² D _3/2 is the metastable energy level produced by spontaneous emission of ² P _1/2 . ³ D[3/2] _1/2 is a metastable high energy level that will decay back to the ² S _1/2 energy level. The 369 nm laser passes through the glass window 130, and a part of the first laser is coupled into a wavelength meter for observing the laser wavelength of the first laser. Most of the first laser light passes through the first polarization beam splitter prism 150 and is divided into probe light with weak power and pump light with strong power, and the probe light is linearly polarized light. The pump light becomes circularly polarized light through the quarter wave plate 180, and is combined with another 935nm infrared laser at the dichroic mirror 30, and the combined beam and probe light after the combination are in the Hollow cathode lamps 40 have central cathode barrels intersecting at a slight angle.

The photodetector 90 receives detection light. The 369 nm laser is amplitude modulated by the chopper 170 . High frequency current modulation for 935nm laser. There is a coupling relationship between the 935nm laser and the 369nm laser on the energy level. The light received by the photodetector 90 contains the information of the 369 nm and 935 nm laser light. Through demodulation by the lock-in amplifier 520, the frequency discrimination error signals of the two lasers can be obtained. Through the first PI control circuit 510 and the second PI control circuit 530, the first control signal and the second control signal are applied to the piezoelectric ceramic PZT of the 369nm external cavity semiconductor laser and the 935nm DFB laser. on the current.

The zero-crossing point can be adjusted by the second half-wave plate 60 to change the locked center frequency. Wherein, by adjusting the second half-wave plate 60, the polarization direction of the probe light is changed. The probe light is split into horizontal and vertical components through the second polarizing beam splitting prism 70 . The polarization direction of the probe light changes, so that the intensity of the two components changes, and the difference between the two components also changes. Therefore, by adjusting the second half-wave plate 60, the zero-crossing point is moved, and the locked frequency value is also changed.

Through the coupled dual-wavelength laser frequency stabilization optical circuit system 100 based on polarization spectroscopy, the 369 nm laser is first locked, and the 935 nm error signal is obtained on this basis, and then the 935 nm laser is locked to realize the simultaneous frequency stabilization of the two lasers. Wherein, after passing through the lock-in amplifier 520 , a 369 nm polarized spectral signal is obtained and input to the first PI control circuit 510 . The scanning of the laser frequency of the 935nm laser is turned off, and the first PI control circuit 510 is turned on to make it work to obtain a first control signal, which is fed back to the PZT or current of the 935nm laser. By adjusting the P and I parameters of the first PI control circuit 510, the locking effect is optimized.

After locking the 369nm laser, scan the 935nm laser frequency. At the same time, 100KHz high-frequency current modulation is applied to the 935nm laser, the spectral signal and the reference signal are simultaneously input to the lock-in amplifier 520, and the error signal can be obtained after demodulation and filtering. After the error signal of the 935nm laser is obtained, the locking process is consistent with that of the 369nm laser.

In one embodiment, the present application provides a frequency stabilization method for a coupled dual-wavelength laser frequency stabilization optical circuit system based on polarization spectroscopy, using the polarization spectroscopy-based coupled dual-wavelength laser in any of the foregoing embodiments The frequency stabilization optical circuit system 100 performs frequency stabilization.

The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity, all possible combinations of the technical features in the above-described embodiments are not described. However, as long as there is no contradiction between the combinations of these technical features, All should be regarded as the scope described in this specification.

The above-mentioned embodiments only represent several embodiments of the present application, and the descriptions thereof are relatively specific and detailed, but should not be construed as a limitation on the scope of the patent application. It should be pointed out that for those skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which all belong to the protection scope of the present application. Therefore, the scope of protection of the patent of the present application shall be subject to the appended claims.

Claims (9)

1. A coupled dual-wavelength laser frequency stabilization optical path system based on polarization spectroscopy, comprising:

a first laser (110) for emitting first laser light;

a first half-wave plate (140) disposed on an optical path of the first laser light;

the first polarization beam splitter prism (150) is arranged on the light path of the first laser light passing through the first half-wave plate (140) and is used for splitting the first laser light into probe light and pumping light;

a chopper (170) provided on an optical path of the pump light;

a quarter wave plate (180) disposed on an optical path of the pump light having passed through the chopper (170);

a second laser (210) for emitting second laser light;

the dichroic mirror (30) is arranged on the light path of the pumping light passing through the quarter-wave plate (180), is arranged on the light path of the second laser light, and is used for combining the pumping light and the second laser light to form combined light;

the hollow cathode lamp (40) is arranged on the light path of the combined beam and the light path of the detection light, and the intersection point of the combined beam and the detection light is positioned in the center of the hollow cathode lamp (40);

a second half-wave plate (60) disposed on a light path of the probe light after passing through the hollow cathode lamp (40);

and a photodetector (90) disposed on the optical path of the detection light after passing through the second half-wave plate (60).

2. The coupled dual wavelength laser frequency stabilization optics based on polarization spectroscopy of claim 1, further comprising:

a lock-in amplifier (520), a signal input of the lock-in amplifier (520) being connected to the photodetector (90);

a first PI control circuit (510), a signal input end of the first PI control circuit (510) is connected with a first signal output end of the lock-in amplifier (520), and a signal output end of the first PI control circuit (510) is connected with a signal control end of the first laser (110).

3. The coupled dual wavelength laser frequency stabilization optics based on polarization spectroscopy of claim 2, further comprising:

a second PI control circuit (530), a signal input end of the second PI control circuit (530) is connected with a second signal output end of the lock-in amplifier (520), and a signal output end of the second PI control circuit (530) is connected with a signal control end of the second laser (210).

4. The coupled dual-wavelength laser frequency stabilization optical path system based on polarization spectroscopy of claim 1, further comprising a second polarization beam splitting prism (70) disposed on the optical path of the probe light after passing through the second half-wave plate (60) for splitting the probe light into a first polarized probe light and a second polarized probe light.

5. The coupled dual wavelength laser frequency stabilization optical path system based on polarization spectroscopy as claimed in claim 4, wherein the photodetector (90) comprises:

a first balanced photodetector (910) disposed on an optical path of the first polarized probe light;

and a second balanced photodetector (920) disposed on an optical path of the second polarized probe light.

6. The coupled dual wavelength laser frequency stabilization optics based on polarization spectroscopy of claim 1, further comprising:

and the glass window sheet (130) is arranged on the optical path of the first laser and is used for separating partial laser from the first laser to detect the wavelength.

7. The coupled dual wavelength laser frequency stabilization optics system based on polarization spectroscopy of claim 6, further comprising:

a first isolator (120) disposed on an optical path of the first laser light, the first isolator (120) disposed between the first laser (110) and the glazing (130).

8. The coupled dual wavelength laser frequency stabilization optics based on polarization spectroscopy of claim 1, further comprising:

and the third polarization beam splitting prism (230) is arranged on the optical path of the second laser and is used for splitting partial laser from the second laser to detect the wavelength.

9. The coupled dual wavelength laser frequency stabilization optics based on polarization spectroscopy of claim 8, further comprising:

and the second isolator (220) is arranged on the optical path of the second laser, and the second isolator (220) is arranged between the second laser (210) and the third polarization beam splitting prism (230).

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