阅读说明：本技术 一种抑制锁频零点漂移的偏振光谱稳频系统 (Polarization spectrum frequency stabilization system for inhibiting frequency locking zero drift ) 是由 裴栋梁 路想想 王杰英 孔德龙 刘简 裴闯 于 2019-11-19 设计创作，主要内容包括：本发明涉及一种抑制锁频零点漂移的偏振光谱稳频系统,包括激光器1、第一λ/2波片2、第一PBS3、第二λ/2波片5、第二PBS6、第一45°反射镜7、λ/4波片9、第二45°反射镜11、原子气室8、第一50:50非偏振分束镜10、液晶延长器12、第三PBS20、第二50:50非偏振分束镜21、第三50:50非偏振分束镜14、第一差分光电探测器19、第二差分光电探测器15、第一PID23和第二PID13。本发明是在偏振光谱稳频的基础上,通过光学方法将光谱的零点漂移量提取出来,再通过反馈回路反馈调节液晶延迟器,使光谱信号中心始终为锁定零点,解决了偏振光谱稳频长期零点漂移较大的问题。(The invention relates to a polarization spectrum frequency stabilization system for inhibiting frequency locking zero drift, which comprises a laser 1, a first lambda/2 wave plate 2, a first PBS3, a second lambda/2 wave plate 5, a second PBS6, a first 45-degree reflector 7, a lambda/4 wave plate 9, a second 45-degree reflector 11, an atom gas chamber 8, a first 50:50 non-polarization beam splitter 10, a liquid crystal extender 12, a third PBS20, a second 50:50 non-polarization beam splitter 21, a third 50:50 non-polarization beam splitter 14, a first differential photoelectric detector 19, a second differential photoelectric detector 15, a first PID23 and a second PID 13. On the basis of polarization spectrum frequency stabilization, the invention extracts the zero drift amount of the spectrum by an optical method, and then adjusts the liquid crystal retarder by feedback of the feedback loop, so that the center of the spectrum signal is always the locking zero point, and the problem of larger zero drift of the polarization spectrum frequency stabilization for a long time is solved.)

1. A polarization spectrum frequency stabilization system for suppressing frequency locking zero drift is characterized in that: the device comprises a light source, a first lambda/2 wave plate, a first PBS (polarization beam splitter), a second lambda/2 wave plate, a second PBS, a first 45-degree reflector, a lambda/4 wave plate, a second 45-degree reflector, an atomic gas chamber, a first 50:50 non-polarization beam splitter, a liquid crystal extender, a third PBS, a second 50:50 non-polarization beam splitter, a third 50:50 non-polarization beam splitter, a first differential photoelectric detector, a second differential photoelectric detector, a first PID (proportion integration differentiation) and a second PID (proportion integration differentiation);

laser generated by a light source is split by a first lambda/2 wave plate and a first PBS, one laser is used for polarization spectrum frequency stabilization, and the other laser is to-be-used laser; the laser with polarization and frequency stabilization is split by a second lambda/2 wave plate and a second PBS (polarizing beam splitter), the reflected S-polarized detection light directly passes through an atomic gas chamber, and the transmitted P-polarized pump light is reflected by a first 45-degree reflector, a lambda/4 wave plate and a second 45-degree reflector and then is coincided with the detection light in the atomic gas chamber through a first 50:50 non-polarized beam splitter; after the detection light and the pumping light are combined through a first 50:50 non-polarizing beam splitter, the detection light beam splitting detection part uses a liquid crystal retarder to be matched with a third PBS to split the detection light into two linearly polarized light beams with vertical polarization directions; the transmitted P polarized light is divided into two beams of P polarized light with the same power and polarization by a second 50:50 non-polarized beam splitter, one beam of P polarized light enters one probe of the first differential photoelectric detector, and the other beam of P polarized light enters one probe of the second differential photoelectric detector; the reflected S polarized light is also divided into two beams of S polarized light with the same power and polarization through a third 50:50 non-polarizing beam splitter, and the two beams of S polarized light respectively enter the other two probes of the two differential photoelectric detectors; the first differential photoelectric detector outputs a polarization spectrum signal, and the light source is controlled through the first PID feedback; the second differential photoelectric detector signal outputs a direct current signal after internal filtering, and the direct current signal controls the voltage of the liquid crystal delayer through the second PID feedback.

2. The frequency stabilization system for the polarization spectrum for suppressing the frequency locking zero drift according to claim 1, wherein: the device also comprises a third 45-degree reflector, a fourth 45-degree reflector, a fifth 45-degree reflector and a sixth 45-degree reflector; one beam of P polarized light enters one probe of the first differential photoelectric detector after being reflected by the third 45-degree reflecting mirror, and the other beam of P polarized light enters one probe of the second differential photoelectric detector after being continuously reflected by the fourth 45-degree reflecting mirror, the fifth 45-degree reflecting mirror and the sixth 45-degree reflecting mirror.

3. The frequency stabilization system for the polarization spectrum for suppressing the frequency locking zero drift according to claim 1, wherein: the light source adopts a tunable single-mode laser with the transition frequency close to that of atoms.

Technical Field

The invention belongs to the field of atomic physics, relates to a polarization spectrum frequency stabilization technology, and particularly relates to a polarization spectrum frequency stabilization system for inhibiting frequency locking zero drift.

Background

In the related research of atomic physics and quantum optics, a laser frequency stabilization technology is a necessary means for narrowing the laser line width and realizing laser frequency stabilization. The laser frequency stabilization can be realized by utilizing an atomic transition line, and the commonly used laser frequency stabilization method comprises saturated absorption spectrum frequency stabilization, polarization spectrum frequency stabilization, bicolor spectrum frequency stabilization, modulation transfer spectrum frequency stabilization, PDH (Pound-Drever-Hall) frequency stabilization and the like. The polarization spectrum frequency stabilization is widely applied to experiments due to the narrow frequency locking line width, simple operation, few required optical components and experimental instruments and high cost performance.

Polarization spectrum frequency stabilization (PS) is a non-modulation frequency locking method for realizing laser light by using different absorption of atoms on light with different polarizations and different propagation speeds of light with different polarizations in an atomic gas chamber, and a schematic diagram of the device is shown in fig. 1. The optical path part is realized by optical components such as a lambda/2 wave plate, a lambda/4 wave plate, a Polarization beam splitter cube (PBS), a 45-degree reflector, an atomic gas chamber and the like. The laser emergent laser is divided into a small part as frequency stabilization laser after being split by the lambda/2 wave plate 2 and the PBS, the frequency stabilization laser is divided into two beams of linearly polarized light through the lambda/2 wave plate 2 and the PBS, the reflected probe light with S polarization and the transmitted pump light with P polarization are reflected and changed into circularly polarized light after passing through the lambda/4 wave plate 6, the probe light and the circularly polarized pump light reversely pass through an atomic gas chamber to coincide, and the polarization of the pump light can be changed through the lambda/4 wave plate, so that a transmission peak signal of the probe light is maximum. The detection light passes through the atomic gas chamber and then is split after passing through the lambda/2 wave plate and the PBS to obtain absorption spectrum signals of the atoms to the laser with different polarizations. On the circuit, the spectrum signal is converted into an electrical signal by a Differential Power Detector (DPD) and Differential amplification is implemented to obtain a polarization spectrum signal, the output signal of the DPD is amplified and filtered, and then an error signal is fed back to a pzt (piezoelectric ceramic) voltage modulation and current modulation port of the laser 1 by a PID10 (probability integration differentiation), so as to control the laser frequency to be locked on an atomic transition line.

The polarization spectrum frequency locking has lower noise after locking because the laser is not modulated; in the aspect of an experimental light path, the laser is directly fed back through the frequency discrimination signal of differential detection, so that the use of experimental instruments is reduced to a certain extent, and the cost is saved. However, since the frequency discrimination signals are generated by different absorption of atoms to different polarized light, when frequency locking is performed, the locking frequency point changes along with the change of optical power and polarization, and a large error is introduced to long-term measurement of an experiment.

Because the long-term stability of the polarization spectrum frequency stabilization is poor, in experiments, methods such as modulation transfer spectrum and PDH frequency locking are mostly adopted for long-term measurement to stabilize the frequency of the laser, but the two methods are complex in light path and expensive in required components.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides the polarization spectrum frequency stabilization system which has fewer required components, lower cost and simple operation and can inhibit the frequency locking zero drift and solve the problem of poorer long-term stability of the polarization spectrum frequency stabilization.

The above object of the present invention is achieved by the following technical solutions:

a polarization spectrum frequency stabilization system for suppressing frequency locking zero drift is characterized in that: the device comprises a light source, a first lambda/2 wave plate, a first PBS (polarization beam splitter), a second lambda/2 wave plate, a second PBS, a first 45-degree reflector, a lambda/4 wave plate, a second 45-degree reflector, an atomic gas chamber, a first 50:50 non-polarization beam splitter, a liquid crystal extender, a third PBS, a second 50:50 non-polarization beam splitter, a third 50:50 non-polarization beam splitter, a first differential photoelectric detector, a second differential photoelectric detector, a first PID (proportion integration differentiation) and a second PID (proportion integration differentiation);

laser generated by a light source is split by a first lambda/2 wave plate and a first PBS, one laser is used for polarization spectrum frequency stabilization, and the other laser is to-be-used laser; the laser with polarization and frequency stabilization is split by a second lambda/2 wave plate and a second PBS (polarizing beam splitter), the reflected S-polarized detection light directly passes through an atomic gas chamber, and the transmitted P-polarized pump light is reflected by a first 45-degree reflector, a lambda/4 wave plate and a second 45-degree reflector and then is coincided with the detection light in the atomic gas chamber through a first 50:50 non-polarized beam splitter; after the detection light and the pumping light are combined through a first 50:50 non-polarizing beam splitter, the detection light beam splitting detection part uses a liquid crystal retarder to be matched with a third PBS to split the detection light into two linearly polarized light beams with vertical polarization directions; the transmitted P polarized light is divided into two beams of P polarized light with the same power and polarization by a second 50:50 non-polarized beam splitter, one beam of P polarized light enters one probe of the first differential photoelectric detector, and the other beam of P polarized light enters one probe of the second differential photoelectric detector; the reflected S polarized light is also divided into two beams of S polarized light with the same power and polarization through a third 50:50 non-polarizing beam splitter, and the two beams of S polarized light respectively enter the other two probes of the two differential photoelectric detectors; the first differential photoelectric detector outputs a polarization spectrum signal, and the light source is controlled through the first PID feedback; the second differential photoelectric detector signal outputs a direct current signal after internal filtering, and the direct current signal controls the voltage of the liquid crystal delayer through the second PID feedback.

Moreover, the device also comprises a third 45-degree reflecting mirror, a fourth 45-degree reflecting mirror, a fifth 45-degree reflecting mirror and a sixth 45-degree reflecting mirror; one beam of P polarized light enters one probe of the first differential photoelectric detector after being reflected by the third 45-degree reflecting mirror, and the other beam of P polarized light enters one probe of the second differential photoelectric detector after being continuously reflected by the fourth 45-degree reflecting mirror, the fifth 45-degree reflecting mirror and the sixth 45-degree reflecting mirror.

Moreover, the light source adopts a tunable single-mode laser with the frequency close to the transition frequency of atoms.

The invention has the advantages and positive effects that:

1. the invention extracts the zero drift amount by flexibly applying corresponding optical components on the basis of the traditional polarization spectrum frequency stabilization, and eliminates the zero drift amount by feedback by adopting a PID feedback technology.

2. The invention uses the combination of the liquid crystal retarder and the PBS in polarization light splitting, can accurately control the light splitting ratio through the stabilized voltage supply and reduce zero drift caused by wave plate change.

3. The polarization spectrum frequency stabilization light path for eliminating the zero drift is simple, uses fewer components, is convenient to operate, and is suitable for the frequency stabilization of the laser near the atomic transition frequency.

Drawings

FIG. 1 is a schematic diagram of a conventional polarization spectrum frequency stabilization device;

FIG. 2 is a schematic diagram of a polarization spectrum frequency stabilization system for suppressing frequency-locking zero drift according to the present invention.

Detailed Description

The present invention will be described in further detail with reference to the following embodiments, which are illustrative only and not limiting, and the scope of the present invention is not limited thereby.

Fig. 1 is a polarization spectrum frequency stabilization system commonly used in experiments, and a light source and a frequency stabilization part can be clearly seen. The light path part of the frequency stabilization system is shown in a block diagram in the figure, and the circuit part mainly carries out PID feedback on the output signal of the photoelectric detector and is mainly realized by a PID control module. The laser generates laser light which is split by the lambda/2 wave plate and the PBS, one laser light is used for stabilizing the frequency of the polarization spectrum, and the other laser light is to-be-used laser light; the laser with polarization and frequency stabilization is split by another lambda/2 wave plate and another PBS (polarization splitting prism), the reflected S-polarization detection light directly passes through the atomic gas chamber, the pump light which transmits P-polarization passes through two 45-degree reflectors and a lambda/4 wave plate and then passes through a 50:50 non-polarization beam splitter to coincide with the detection light in the atomic gas chamber, the detection light passes through another lambda/2 wave plate and then another PBS for light splitting after passing through the beam splitter, the transmission P-polarization light directly enters one probe of the differential photoelectric detector, the reflection S-polarization light enters another probe of the differential photoelectric detector after being reflected by another 45-degree reflector, and the reflection S-polarization light is converted into an electric signal which is processed by a PID (proportion integration differentiation) and then fed back to control the laser for frequency stabilization.

The following detailed description of the polarization spectrum frequency stabilization system for suppressing zero shift of frequency lock according to the present invention with reference to fig. 2 is given below, and the following implementation is only illustrative and not restrictive, and the protection range of the polarization spectrum frequency stabilization system for suppressing zero shift of frequency lock according to the present invention cannot be limited thereby

The core function of the polarization spectrum frequency stabilization system for inhibiting zero drift is further detailed.

A polarized spectrum frequency stabilization system for suppressing frequency locking zero drift comprises a light source 1, a first lambda/2 wave plate 2, a first PBS3, a second lambda/2 wave plate 5, a second PBS6, a first 45-degree reflector 7, a lambda/4 wave plate 9, a second 45-degree reflector 11, an atomic gas cell 8, a first 50:50 non-polarized beam splitter 10, a liquid crystal extender 12, a third PBS20, a second 50:50 non-polarized beam splitter 21, a third 50:50 non-polarized beam splitter 14, a first differential photoelectric detector 19, a second differential photoelectric detector 15, a first PID23 and a second PID 13.

Laser generated by a light source is split by a first lambda/2 wave plate and a first PBS, one laser is used for polarization spectrum frequency stabilization, and the other laser is to-be-used laser 4; the laser with polarization and frequency stabilization is split by a second lambda/2 wave plate and a second PBS (polarizing beam splitter), the reflected S-polarized detection light directly passes through an atomic gas chamber, and the pump light which transmits P-polarized is reflected by a first 45-degree reflector, a lambda/4 wave plate and a second 45-degree reflector and then is superposed with the detection light in the atomic gas chamber through a first 50:50 non-polarized beam splitter; after the detection light and the pumping light are combined through a first 50:50 non-polarizing beam splitter, the detection light beam splitting detection part uses a liquid crystal retarder to be matched with a third PBS to split the detection light into two linearly polarized light beams with vertical polarization directions; the transmitted P polarized light is divided into two beams of P polarized light with the same power and polarization by a second 50:50 non-polarized beam splitter, one beam of P polarized light enters one probe of the first differential photoelectric detector, and the other beam of P polarized light enters one probe of the second differential photoelectric detector; the reflected S polarized light is also divided into two beams of S polarized light with the same power and polarization through a third 50:50 non-polarizing beam splitter, and the two beams of S polarized light respectively enter the other two probes of the two differential photoelectric detectors; the first differential photoelectric detector outputs a polarization spectrum signal, and the light source is controlled through the first PID feedback; the second differential photoelectric detector signal outputs a direct current signal after internal filtering, and the direct current signal controls the voltage of the liquid crystal delayer through the second PID feedback. The liquid crystal retarder can control the phase of the delayed laser through voltage, and the voltage of the liquid crystal retarder can be changed to match with the PBS to change the beam splitting ratio of the detection light, so that the zero point of the polarization spectrum frequency discrimination signal is changed, and a foundation is provided for eliminating zero point drift in polarization spectrum frequency stabilization in principle.

In the above structure, the device further includes a third 45 ° reflector 17, a fourth 45 ° reflector 22, a fifth 45 ° reflector 18, and a sixth 45 ° reflector 16; one beam of P polarized light enters one probe of the first differential photoelectric detector after being reflected by the third 45-degree reflecting mirror, and the other beam of P polarized light enters one probe of the second differential photoelectric detector after being continuously reflected by the fourth 45-degree reflecting mirror, the fifth 45-degree reflecting mirror and the sixth 45-degree reflecting mirror.

In the above structure, the light source is a tunable single-mode laser having a frequency close to the atomic transition frequency.

The polarization spectrum frequency stabilization system for inhibiting the zero drift of the frequency lock is greatly improved at a receiving part of an optical signal, the liquid crystal delayer is introduced, a PID control module is additionally arranged on the basis of the original PID control module, one PID feedback control laser is arranged, the voltage of the liquid crystal delayer is controlled by the other PID feedback, the generation of a more stable differential optical signal can be realized by accurately controlling the driving voltage of the liquid crystal delayer, and the liquid crystal delayer controlled by the same voltage also provides a basis for a feedback mechanism of the zero drift signal. The method specifically comprises the following steps:

1. a zero drift feedback system is added on the basis of traditional polarization spectrum frequency stabilization, the detection light after two BS beams are respectively selected to be differentially amplified through a differential photoelectric detector, the drift amount of the detection light is extracted, the drift amount and the offset participating in the polarization spectrum are changed synchronously, and the control voltage of a liquid crystal delayer is changed through PID feedback by utilizing the drift amount, so that the frequency discrimination signal center of the polarization spectrum is locked at zero.

2. The liquid crystal retarder is used in the polarization spectrum to be matched with the PBS to split the detection light, the detection light is split into two beams of linearly polarized light with vertical polarization directions, the polarization shift amount of the detection light is reduced while the frequency stabilization requirement of the polarization spectrum is met, and meanwhile, the voltage control liquid crystal retarder lays a foundation for compensating zero drift.

3. The two beams of detection light are respectively split by using the BS in front of the detector, and then the two beams of detection light with different polarizations are differentially amplified, so that the zero drift amount of polarization spectrum frequency stabilization is extracted in real time.

4. And directly controlling the control voltage of the liquid crystal retarder through PID feedback by using the extracted drift amount, and locking the frequency discrimination signal center of the polarization spectrum at a zero point.

In conclusion, the polarization spectrum frequency stabilization system for inhibiting the frequency locking zero drift is firstly proposed in China, so that the long-term drift of the polarization spectrum frequency stabilization can be effectively inhibited, and the long-term stability of the frequency stabilization is improved. The scheme has the advantages of compact light path structure, simple operation and higher practicability. After the method is adopted, the frequency stabilization laser line width is narrow in cold atom interference related experiments, the long-term stability is high, and long-term continuous measurement can be realized.

Although the embodiments of the present invention and the accompanying drawings are disclosed for illustrative purposes, those skilled in the art will appreciate that: various substitutions, changes and modifications are possible without departing from the spirit and scope of the invention and the appended claims, and therefore the scope of the invention is not limited to the disclosure of the embodiments and the accompanying drawings.