阅读说明：本技术 一种多通道激光边带稳频系统 (Multichannel laser sideband frequency stabilization system ) 是由 李加冲 周飞 章嘉伟 冯芒 于 2020-11-05 设计创作，主要内容包括：本发明公开了一种多通道激光边带稳频系统,包括真空室,内部为超稳腔；电光调制器,用于接收移频信号来调制激光频率,使得边带频率与超稳腔谐振；还用于接收PDH调制信号,对激光进行相位调制；基于PID的数字电路模块控制器,用于接收调制转移的色散信号,以根据信号信息与设定值的偏差来调整激光器的驱动信号,来抑制激光器的频率波动。通过对电光调制器施加移频信号调制激光频率,使得边带频率与光学腔谐振。然后对电光调制器施加PDH调制信号,对激光进行相位调制。通过光电探测器得到的误差信号反馈回激光器的伺服系统,来抑制激光器的频率波动,使其锁定在光学腔上,从而实现压窄激光线宽、激光频率可调谐且频率能长时稳定。(The invention discloses a multichannel laser sideband frequency stabilization system, which comprises a vacuum chamber, wherein an ultrastable cavity is arranged in the vacuum chamber; the electro-optical modulator is used for receiving the frequency shift signal to modulate the laser frequency so that the sideband frequency and the ultra-stable cavity resonate; the laser modulator is also used for receiving a PDH modulation signal and carrying out phase modulation on laser; and the PID-based digital circuit module controller is used for receiving the dispersion signal subjected to modulation transfer so as to adjust a driving signal of the laser according to the deviation of the signal information and a set value, so that the frequency fluctuation of the laser is suppressed. The laser frequency is modulated by applying a frequency shift signal to the electro-optic modulator such that the sideband frequencies are resonant with the optical cavity. A PDH modulation signal is then applied to the electro-optic modulator to phase modulate the laser light. The error signal obtained by the photoelectric detector is fed back to a servo system of the laser to inhibit the frequency fluctuation of the laser and lock the laser on the optical cavity, so that the narrow laser line width, the tunable laser frequency and the long-term stability of the frequency can be realized.)

1. A multi-channel laser sideband frequency stabilization system comprising:

a vacuum chamber, the interior of which is an ultrastable cavity;

the electro-optical modulator is used for receiving the frequency shift signal to modulate the laser frequency so that the sideband frequency and the ultra-stable cavity resonate; the laser modulator is also used for receiving a PDH modulation signal and carrying out phase modulation on laser;

and the PID-based digital circuit module controller is used for receiving the dispersion signal subjected to modulation transfer, and adjusting a driving signal of the laser according to the deviation of the signal information and a set value so as to inhibit the frequency fluctuation of the laser and enable the laser to be locked on the ultrastable cavity.

2. The multi-channel laser sideband frequency stabilization system of claim 1, further comprising:

a first RF signal source for applying a frequency shift signal omega to the electro-optical modulator_mFrequency omega to the electro-optical modulator_mThe frequency shift phase modulation of (1) generates a set of sidebands omega + -omega_mBy adjusting the frequency-shift modulation signal omega_mAmplitude of vibration so that ω ± Ω_mThe energy of (2) is maximized; omega is the laser frequency matched with the ultrastable cavity.

3. A multichannel laser sideband frequency stabilization system according to claim 1 or 2 further comprising a second radio frequency signal source for applying a PDH modulated signal δ to the electro-optic modulator_m，δ_mIs the modulation frequency.

4. The multi-channel laser sideband frequency stabilization system of claim 3, wherein the modulation shifted dispersive signal is modulated by a modulation shifted dispersive signal component comprising:

the third lambda/4 wave plate, the second polarization splitting prism, the first photoelectric detector, the frequency mixer and the phase shifter; linearly polarized light of laser with frequency jitter information transmitted from the vacuum chamber and passing through the third lambda/4 wave plate and the second polarization beam splitter prism passes through the first photoelectric detector and the mixer at delta_mAnd (4) demodulating, namely adjusting the phase of the phase shifter to obtain a dispersion signal of modulation transfer.

5. The multi-channel laser sideband frequency stabilization system of claim 1, further comprising:

and the low-pass bandwidth type filter is used for transmitting the dispersion signal subjected to modulation transfer to the PID-based digital circuit module controller.

6. The multi-channel laser sideband frequency stabilization system of claim 1, wherein an even number of window interfaces are uniformly distributed on the vacuum chamber along a circumference, and center points of all the window interfaces are located on the same distribution circumference;

half of the even number of window interfaces are used as laser entrance ports, and are provided with plane light-passing cavity mirrors which are suitable for the entrance and need to stabilize the corresponding wavelength of the laser with the frequency;

and the other half of the even number of window interfaces is used as a laser reflection port and is provided with a concave light-transmitting cavity mirror which has the frequency corresponding to the incident interface and is used for reflecting the frequency required to be stabilized.

7. The multi-channel laser sideband frequency stabilization system of claim 1 or 6, wherein a surface of the vacuum chamber is provided with a first CF40 interface, a second CF40 interface; the first CF40 interface is provided with a radio frequency feed-through connected with the ion pump; the second CF40 interface 3 is equipped with rf feed-throughs for connection to a temperature control module.

8. The multi-channel laser sideband frequency stabilization system of claim 4, further comprising a first component comprising a Faraday isolator, a first λ/2 wave plate, a first polarization splitting prism, a first beam splitter plate, a first λ/4 wave plate, a second λ/2 wave plate, a first lens, a single-mode polarization maintaining fiber, a second λ/4 wave plate, a Glan Taylor prism;

the laser passes through the Faraday isolator and the first lambda/2 wave plate, then selects horizontal polarized light, sequentially passes through the first polarization beam splitter prism, the first beam splitter plate, the first lambda/4 wave plate, the second lambda/2 wave plate, the lens, the single-mode polarization maintaining fiber, the second lambda/4 wave plate and the Glan Taylor prism, and then passes through the electro-optical modulator.

9. The multi-channel laser sideband frequency stabilization system of claim 8, further comprising a second assembly comprising a first pair of mirrors, a lens assembly, a second pair of mirrors, a third λ/2 plate, a second polarizing beam splitter prism, and a third λ/4 plate; laser emitted by the electro-optical modulator rotates the polarization state of the laser after phase modulation by 180 degrees through the first pair of reflectors, the lens group, the second pair of reflectors and the third lambda/2 wave plate and then generates circularly polarized light through the second polarization beam splitter prism and the third lambda/4 wave plate.

10. The multi-channel laser sideband frequency stabilization system of claim 9, further comprising a third pair of mirrors, wherein circularly polarized light generated by the second polarization beam splitter prism and the third λ/4 wave plate is vertically incident into the metastable cavity from a laser incident port of the vacuum chamber after passing through the third pair of mirrors; the third pair of mirrors is used for adjusting the mode of the laser to be matched with the mode of the super stable cavity.

Technical Field

The invention relates to the technical field of laser, in particular to a multichannel laser sideband frequency stabilizing system.

Background

In the 60 s of the 20th century, the invention of laser has created a new situation for spectroscopy research, the application field of laser is more and more extensive, and in many application fields of laser, the laser frequency stability is an extremely important index parameter. Therefore, the laser frequency stabilization technology becomes an important direction of basic scientific research, and plays an increasingly important role in modern scientific technology.

The 20th century quantum mechanics brings about a revolution of the technology, a cold atom molecule and ion system is an ideal system for researching quantum information and quantum precision measurement technology, and no matter the laser cooling of atom molecules and ions is realized, or the quantum state and quantum control are carried out, a plurality of beams of laser with high and stable frequency, extremely low noise and narrow line width are needed, so that the basic physical quantities such as time, displacement, angular speed and the like are measured more accurately compared with the traditional measurement technology.

Generally, the frequency of the laser is determined by the effective length of the laser resonator, so that the frequency of the laser is easily affected by the internal thermal effect of the laser cavity and the external environmental noise to cause jitter and drift, and therefore, various frequency stabilization technologies such as passive type and active type need to be performed to stabilize the laser output frequency by other methods. The standard PDH (Pound-Drever-Hall) frequency stabilization method is a frequency stabilization method capable of locking the line width of laser light to Hz magnitude through an optical resonant cavity, and is also a method commonly used in most laboratories at present for realizing ultra-narrow line width laser output. Compared with other locking methods, the slope of an error signal formed by the PDH method at a locking point is larger, so that a narrow expected laser line width can be achieved; and the range of frequency correction can be wide, and once the lock is locked, the lock is not easy to be unlocked. In the PDH method, the error signal is obtained by detecting the frequency modulated optical signal reflected from the cavity.

However, in practical situations, the difference between the laser frequency required by the experiment and the resonant frequency of the optical cavity is large, and the laser frequency needs to be adjusted to the resonant frequency through various complicated frequency shifting devices.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provides a multichannel laser sideband frequency stabilization system, which is used for modulating the frequency of laser and locking the laser on a multichannel optical super-stable cavity, so that a device with narrow laser line width and pressure, variable frequency locking points and tunable laser frequency after locking is realized, and the multichannel laser sideband frequency stabilization system is suitable for the fields of precise spectrum, precise measurement, quantum information and the like.

In order to achieve the purpose, the technical scheme of the invention is as follows:

compared with the prior art, the invention has the beneficial effects that:

a multi-channel laser sideband frequency stabilization system comprising:

a vacuum chamber, the interior of which is an ultrastable cavity;

the electro-optical modulator is used for receiving the frequency shift signal to modulate the laser frequency so that the sideband frequency and the ultra-stable cavity resonate; the laser modulator is also used for receiving a PDH modulation signal and carrying out phase modulation on laser;

and the PID-based digital circuit module controller is used for receiving the dispersion signal subjected to modulation transfer, and adjusting a driving signal of the laser according to the deviation of the signal information and a set value so as to inhibit the frequency fluctuation of the laser and enable the laser to be locked on the ultrastable cavity.

In this manner, the laser frequency is modulated by applying a frequency shift signal to the electro-optic modulator such that the sideband frequencies resonate with the optical cavity. A PDH modulation signal is then applied to the electro-optic modulator to phase modulate the laser light. The error signal obtained by the photoelectric detector is fed back to a servo system of the laser to inhibit the frequency fluctuation of the laser and lock the laser on the optical cavity, so that the narrow laser line width, the tunable laser frequency and the long-term stability of the frequency can be realized. The influence of residual amplitude modulation on frequency stabilization is reduced by adjusting the amplitude and relative phase change of the laser sideband, and the tuning of the locking center frequency is realized by modulating the sideband frequency, and the tuning range can reach GHz level

Further, the multichannel laser sideband frequency stabilization system further comprises:

a first RF signal source for applying a frequency shift signal omega to the electro-optical modulator_mFrequency omega to the electro-optical modulator_mThe frequency shift phase modulation of (1) generates a set of sidebands omega + -omega_mBy adjusting the frequency-shift modulation signal omega_mAmplitude of vibration so that ω ± Ω_mThe energy of (2) is maximized; omega is the laser frequency matched with the ultrastable cavity. Thus, the frequency shift of the laser frequency ω (i.e. carrier frequency) for the ultrastable cavity matching to the frequency f for the desired locking can be realized.

Furthermore, the multichannel laser sideband frequency stabilization system also comprises a second radio frequency signal source which is used for applying a PDH modulation signal delta to the electro-optical modulator_m，δ_mIs the modulation frequency.

Further, the modulation shifted dispersive signal is modulated by a modulation shifted dispersive signal component, the modulation shifted dispersive signal component comprising:

the third lambda/4 wave plate, the second polarization splitting prism, the first photoelectric detector, the frequency mixer and the phase shifter; linearly polarized light of laser with frequency jitter information transmitted from the vacuum chamber and passing through the third lambda/4 wave plate and the second polarization beam splitter prism passes through the first photoelectric detector and the mixer at delta_mDemodulation is performed to obtain a modulation-shifted dispersion signal by adjusting the phase of the phase shifter, and the dispersion signal is used as a frequency discrimination signal (PDH signal).

Further, the multichannel laser sideband frequency stabilization system further comprises:

and the low-pass bandwidth type filter is used for transmitting the dispersion signal subjected to modulation transfer to the PID-based digital circuit module controller.

Furthermore, even window interfaces are uniformly distributed on the vacuum chamber along the circumference, and the central points of all the window interfaces are positioned on the same distribution circumference;

half of the even number of window interfaces are used as laser entrance ports, and are provided with plane light-passing cavity mirrors which are suitable for the entrance and need to stabilize the corresponding wavelength of the laser with the frequency;

and the other half of the even number of window interfaces is used as a laser reflection port and is provided with a concave light-transmitting cavity mirror which has the frequency corresponding to the incident interface and is used for reflecting the frequency required to be stabilized.

Further, the surface of the vacuum chamber is provided with a first CF40 interface and a second CF40 interface; the first CF40 interface is provided with a radio frequency feed-through connected with the ion pump; the second CF40 interface 3 is fitted with a dc feed-through for connection to a temperature control module.

Furthermore, the multichannel laser sideband frequency stabilization system also comprises a first component, wherein the first component comprises a Faraday isolator, a first lambda/2 wave plate, a first polarization splitting prism, a first beam splitter, a first lambda/4 wave plate, a second lambda/2 wave plate, a first lens, a single-mode polarization maintaining optical fiber, a third lambda/4 wave plate and a Glan Taylor prism;

the laser passes through a Faraday isolator, a first lambda/2 wave plate and a first polarization beam splitter prism, selects horizontal polarized light, sequentially passes through a first beam splitter plate, a first lambda/4 wave plate, a second lambda/2 wave plate, a lens, a single-mode polarization maintaining optical fiber, a second lambda/4 wave plate and a Glan Taylor prism and then passes through the electro-optical modulator.

The Faraday isolator is used for preventing the laser reflected back from returning to the laser and protecting the laser; a polarization splitting prism; the transmitted is horizontal polarization and the reflected is vertical polarization; the first lambda/2 wave plate and the first polarization splitting prism are combined to roughly adjust the polarization direction of the laser to be linearly polarized; the first light splitting flat sheet is used for meeting the power requirements of other optical paths; the first lambda/4 wave plate and the second lambda/2 wave plate accurately control the laser polarization to become stable linear polarization; the lens is used for adjusting the size of laser facula so as to improve the maximum coupling efficiency of the entering optical fiber; the single-mode polarization maintaining fiber is far away from the laser placing position, and needs to be pulled by the fiber; the laser is emitted from the other end of the optical fiber, passes through the combination of the first lambda/4 wave plate and the Glan Taylor prism and is used for finely adjusting the polarization of the laser entering the EOM so as to meet the strict incident polarization requirement of the EOM.

Further, the multichannel laser sideband frequency stabilization system also comprises a second component, wherein the second component comprises a first pair of reflectors, a lens group, a second pair of reflectors, a third lambda/2 wave plate, a second polarization beam splitter prism and a third lambda/4 wave plate; laser emitted by the electro-optical modulator rotates the polarization state of the laser after phase modulation by 180 degrees through the first pair of reflectors, the lens group, the second pair of reflectors and the third lambda/2 wave plate and then generates circularly polarized light through the second polarization beam splitter prism and the third lambda/4 wave plate.

The laser resonates with the optical F-P cavity, the beam waist radius of the laser needs to be matched with that of the F-P cavity, so that the initial interference of the laser through the optical fiber is taken as a starting point, the position of the beam waist of the optical F-P cavity is taken as an end point, the distance is long, and due to the limited space, the mode of using the optical path L-shaped mode is used, and the mode is the effect of a first pair of reflectors; the lens group has the function of changing the beam waist radius of the laser to be matched with the F-P cavity; the third lambda/2 wave plate is used for controlling the power of the laser F-P cavity to be the same every day; the second polarization beam splitter prism and the second lambda/4 wave plate are used for adjusting the polarization, so that the power reflected by the F-P cavity is minimum through the second polarization beam splitter prism; the second pair of mirrors is used to tune the laser to resonate with the cavity, eliminating the remaining high order modes.

Furthermore, the multichannel laser sideband frequency stabilization system also comprises a third pair of reflectors, wherein circularly polarized light generated by the second polarization beam splitter prism and the third lambda/4 wave plate passes through the third pair of reflectors and then is vertically incident into the ultrastable cavity from a laser incident port of the vacuum chamber; the third pair of mirrors is used for adjusting the mode of the laser to be matched with the mode of the super stable cavity.

Compared with the prior art, the invention has the following beneficial effects:

the laser frequency is modulated by applying a frequency shift signal to the electro-optic modulator such that the sideband frequencies are resonant with the optical cavity. A PDH modulation signal is then applied to the electro-optic modulator to phase modulate the laser light. The error signal obtained by the photoelectric detector is fed back to a servo system of the laser to inhibit the frequency fluctuation of the laser and lock the laser on the optical cavity, so that the narrow laser line width, the tunable laser frequency and the long-term stability of the frequency can be realized. The influence of residual amplitude modulation on frequency stabilization is reduced by adjusting the amplitude and the relative phase change of the laser sideband, and the tuning of the locking center frequency is realized by modulating the sideband frequency, and the tuning range can reach the GHz level; a small range adjustment of the locking frequency (0-200MHz) is achieved and is stable over long periods.

Drawings

FIG. 1 is a schematic view of the entire appearance of a vacuum chamber;

FIG. 2 is a top view of FIG. 1;

in FIGS. 1-2: 1-vacuum chamber; 2-first CF40 interface; 3-first CF40 interface; 4-a plane cavity mirror; 5-concave cavity mirror.

FIG. 3 is a schematic diagram of a 854nm laser PDH optical path and corresponding frequency locking electronic components. Wherein: IOS (isolator) optical isolator; HWP (half Wave plate) lambda/2 Wave plate; PBS (polarization Splitting prism); BS (Beam splitter); l (len) a lens; PMF (Single-mode Polarization-mail Fiber), Single-mode Polarization-maintaining Fiber; GTP (Grant-Taylor Prism), a Glan Taylor Prism; QWP (quarter Wave plate) lambda/4 Wave plate; EOM (electro-optical modulator) an electro-optical modulator; HR (high Reflector) a highly reflective mirror; PD (Photo-Detector) a broadband photodetector; PS (phase Shifter) phase shifter; mixer is a Mixer; LPF (Low-Pass Filter) Low Pass Filter; SG (signal generator) a radio frequency signal source; F-P Cavity (Fabry-Perot Cavity) ultrastable Cavity (Fabry-Perot optical resonator);

FIG. 4 is a graph of Carrier (Carrier) versus frequency shifted sideband versus modulation amplitude for a 854nm laser at the same frequency shifted modulation frequency;

FIG. 5 is a graph of carrier, frequency shifted sideband and PDH modulated signal for a 854nm laser at the same PDH modulation frequency;

FIG. 6 is a schematic diagram of a 854nm laser without any RF phase modulation;

FIG. 7 is a schematic diagram of the relationship between the 854nm laser frequency discrimination signal and the phase;

FIG. 8 is a schematic diagram of reflected light, transmitted light, and error signals before and after 854nm laser lock;

wherein a, b, c correspond to the reflected, transmitted, error signals prior to lock-in; graph A, B, C corresponds to the reflected, transmitted, error signal after locking.

Detailed Description

The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.

Example 1:

as shown in fig. 1-3, the multi-channel laser sideband frequency stabilization system based on the PDH method comprises a vacuum chamber 1, a series of optical paths as shown in fig. 3 arranged outside the vacuum chamber 1, and corresponding frequency-locking electronics.

First window sheet interfaces A, second window sheet interfaces B, third window sheet interfaces C, fourth window sheet interfaces D, fifth window sheet interfaces E, sixth window sheet interfaces F, seventh window sheet interfaces G and eighth window sheet interfaces H (respectively marked as A, B, C, D, E, F, G, H and distributed along the circumference in the anticlockwise direction in the figure 2) are uniformly distributed on the vacuum chamber 1 along the circumference, the central points of the first to eighth window sheet interfaces are positioned on the same distribution circumference, and the top surface of the vacuum chamber 1 is provided with a first CF40 interface 2 and a second CF40 interface 3.

The first window interface A, the second window interface B, the third window interface C and the fourth window interface D are all provided with a plane cavity mirror 4 for injecting laser with required locking frequency into the vacuum chamber.

And the fifth window interface E, the sixth window interface F, the seventh window interface G and the eighth window interface H are respectively provided with a concave cavity mirror 5 which emits laser with the frequency corresponding to that of the second window interface B, the first window interface A, the fourth window interface D and the third window interface C.

The first CF40 interface 2 is connected to the ion pump through the rf feedthrough for stabilizing the vacuum degree in the vacuum chamber 1, and the second CF40 interface 3 is connected to the temperature control module through the rf feedthrough for stabilizing the temperature in the vacuum chamber 1, so that the F-hold cavity length tends to be stable, for example, the distance between the center point of the first window interface a and the center point of the sixth window interface F tends to be a constant value.

The vacuum chamber 1 was maintained at a vacuum degree of 8.0X 10 in the vacuum chamber 1 by an ion pump^-6Pa or so.

The vacuum chamber 1 is in a regular quadrilateral hexahedral structure, eight window sheet interfaces (A-H) are respectively arranged on four surfaces of the vacuum chamber 1 which are uniformly distributed along the same circumference, and the circle center of the distributed circumference is superposed with the center of the vacuum chamber 1.

The first window interface A and the sixth window interface F are provided with a cavity mirror with the coating frequency of 866nm and the reflectivity of 99.95 percent, a straight line where a connecting line of a central point of the first window interface A and a central point of the sixth window interface F is located is an X axis, and the positive direction of the X axis is from the central point of the first window interface A to the central point of the sixth window interface F, namely the incident light direction.

The second window piece interface B and the sixth window piece interface E are provided with cavity mirrors with the coating frequency of 854nm and the reflectivity of 99.95%, the straight line of the connecting line of the central point of the second window piece interface B and the central point of the fifth window piece interface E is parallel to the X axis, and the central point of the second window piece interface B to the central point of the fifth window piece interface E is the incident light direction.

The third window piece interface C and the eighth window piece interface H are provided with a cavity mirror with film coating frequency of 397nm and reflectivity of 99.95%, a straight line where a connecting line of a central point of the third window piece interface C and a central point of the eighth window piece interface H is located is a Y axis, the direction from the central point of the third window piece interface C to the central point of the eighth window piece interface H is a positive direction of the Y axis, namely an incident light direction, and the Y axis is perpendicular to the X axis.

The fourth window interface D and the seventh window interface G are provided with a cavity mirror with the coating frequency of 397nm and the reflectivity of 99.95%, and the connecting line of the central point of the fourth window interface D and the central point of the seventh window interface G is parallel to the Y axis, namely the incident light direction and is vertical to the connecting line of the central point of the second window interface B and the central point of the fifth window interface E.

A series of optical paths as in fig. 3 outside the vacuum chamber 1, and corresponding frequency-locked electronics: the device is an organic combination of elements such as a reflector HR, a lambda/2 wave plate HWP, a Glan Taylor prism GTP, an electro-optical modulator EOM, a lambda/4 wave plate QWP, a polarization beam splitter PBS, a photoelectric detector PD, a camera CCD, a radio frequency source SG, a Mixer Mixer, a low pass filter LPF, a digital circuit module controller Servo based on PID and the like.

Example 2

By using the multi-channel laser sideband frequency stabilization system based on the PDH method described in embodiment 1, the method for locking 854nm laser is as follows:

step 1, laser with the wavelength of 854nm passes through a Faraday isolator, a lambda/2 wave plate HWP1 and a polarization beam splitter PBS1 to select horizontal polarized light, and sequentially passes through a beam splitter plate BS1, a lambda/4 wave plate QWP1, a lambda/2 wave plate HWP2, a lens L1, a single-mode polarization maintaining fiber PMF, a lambda/4 wave plate QWP2 and a Glan Taylor prism GTP;

step 2, laser passes through an optical fiber coupling continuous electro-optical modulator EOM (Ixblue company in France), because the difference between the required locking laser frequency f and the laser frequency omega matched with the ultrastable cavity is more than 100MHz, in the scheme, the laser frequency omega matched with the ultrastable cavity is selected to be 350.86565THz, the required locking frequency f is 350.86298THz, and the difference between the two is omega_mω -f 670 MHz. Firstly, the laser frequency omega (carrier frequency) matched with the ultra-stable cavity is shifted to the frequency f required to be locked, namely, a frequency shift modulation signal omega is applied to the EOM by a radio frequency signal source SG1_m(frequency shift modulation frequency range 0-GHz), and the frequency of the optical fiber type electro-optical modulator is omega_mThe frequency shift phase modulation of (1) generates a set of sidebands omega + -omega_mBy adjusting the frequency-shift modulation signal omega_mAmplitude of the vibration wave, which can be made to be omega + -omega_mIs maximized as shown in fig. 4.

Since the laser frequency resonant with the metastability cavity is specific, the laser frequency is tuned to the locking frequency f ═ ω - Ω_mWhen the locking frequency f is resonant with the metastable cavity, it can be regarded as the carrier frequency ω ', ω' ═ f 350.86298THz, and then the PDH modulation signal δ is applied to the EOM by the rf signal source SG2_mSelecting delta in the scheme_m＝25MHz，δ_mModulation frequency (PDH modulation frequency 0-50MHz), as shown in FIG. 5;

step 3, rotating the polarization state of the laser after phase modulation by 180 degrees through a pair of reflectors HR1 and HR2, a lens group L2 and L3, a pair of reflectors HR3 and HR4 and a lambda/2 wave plate HWP3, and generating elliptically polarized light through a polarization beam splitter prism PBS2 and a lambda/4 wave plate QWP 3;

step 4, finally, vertically irradiating the laser beam into the hyperstable cavity from a first window sheet interface A of the plane cavity mirror 4 with the coating frequency of 866nm and the reflectivity of 99.95% through a pair of reflectors HR5 and HR6, wherein the pair of reflectors HR5 and HR6 are used for adjusting the mode of the laser beam to be matched with the mode of the hyperstable cavity, the coupling condition of the laser beam and the hyperstable cavity is shown in FIG. 6, and the coupling degree reaches more than 50%;

step 5, repeatedly reflecting the laser in the super-stable cavity F-PCavity for a plurality of times, when the laser frequency is not consistent with the laser frequency matched with the super-stable cavity, reflecting the laser by a sixth window F of the concave cavity mirror 5 with the coating frequency 866nm and the reflectivity of 99.95%, transmitting the laser by a first window interface A of the plane cavity mirror 4 with the coating frequency 866nm and the reflectivity of 99.95%, enabling the part of the laser with frequency jitter information to pass through the lambda/4 wave plate QWP3 and the linearly polarized light of the polarization beam splitter PBS2 again, pass through the photoelectric detector PD1 and the Mixer Mixer at delta and then pass through the delta and delta respectively_mDemodulation, in which the phase of the phase shifter PS is adjusted to obtain a dispersion signal of modulation transfer, which is used as a frequency discrimination signal PDH signal, see fig. 7, a photodetector PD2 is used to monitor the photoelectric signal transmitted through a sixth window F with a reflective concave cavity mirror 5, and a CCD is used to observe and detect the laser mode;

and 6, transmitting the obtained dispersion signal subjected to modulation transfer to a digital circuit module controller Servo based on PID (proportion integration differentiation) through a low-pass bandwidth filter LPF (low pass filter), and continuously adjusting a driving signal of a laser according to the deviation of feedback information and a set value so as to inhibit external interference and enable the laser frequency to tend to be stable at omega + omega or omega-omega_mThat is, the laser is stabilized at f ═ ω' ═ 350.86298THz, see fig. 8(C, C), and it is clear from the figure that the value of the error signal after locking is 70mV, which is small, indicating that the stability of the system after locking is very high, and the locking time is as long as 12 hours.

And 7, if the stabilized frequency needs to be finely adjusted, the frequency can be adjusted by adjusting the output frequency of the signal source (within the range of the resonance frequency of the EOM), so that the laser frequency can be stabilized for a long time.

Example 3

With the device for multichannel laser sideband frequency stabilization based on the PDH method described in embodiment 1, the method for locking 397nm laser is as follows:

step 1, laser with the wavelength of 397nm passes through a Faraday isolator IOS, a lambda/2 wave plate HWP1 and a polarization beam splitter PBS1, then horizontal polarized light is selected, and the laser sequentially passes through a beam splitter flat plate BS1, a lambda/4 wave plate QWP1, a lambda/2 wave plate HWP2, a lens L1, a single-mode polarization maintaining fiber PMF, a lambda/4 wave plate QWP2 and a Glan Taylor prism GTP;

step 2, limiting the electronic driver reasons of the wavelength and EOM, EOM below 500nm is all spatial type, in the scheme, a spatial resonance type electro-optical modulator EOM (Qubig company, Germany) is selected. The laser passes through a spatial resonance type electro-optical modulator EOM, the laser frequency omega matched with the ultrastable cavity is selected to be 755.223820THz, the required locking frequency f is 755.222800THz, and the difference value between the two is omega_mω -f 1.02 GHz. Then firstly, the laser frequency omega (carrier frequency) matched with the ultra-stable cavity is shifted to the required locking frequency f, namely, a frequency shift modulation signal omega is applied to the EOM by a radio frequency signal source SG1_m(frequency shift modulation frequency range 750-1.5 GHz) with frequency omega for optical fiber type electro-optical modulator_mThe frequency shift phase modulation of (1) generates a set of sidebands omega + -omega_mBy adjusting the frequency-shift modulation signal omega_mAmplitude of the vibration wave, which can be made to be omega + -omega_mThe energy of (2) is maximized.

Since the laser frequency resonant with the metastability cavity is specific, the laser frequency is tuned to the locking frequency f ═ ω - Ω_mWhen the locking frequency f is resonant with the metastable cavity, it can be regarded as the carrier frequency ω ', ω' ═ f 755.222800THz, and then the PDH modulation signal δ is applied to the EOM by the rf signal source SG2_mSelecting delta in the scheme_m＝13MHz，δ_mIs a modulation frequency (PDH modulation frequency 0-50 MHz);

step 3, rotating the polarization state of the laser after phase modulation by 180 degrees through a pair of reflectors HR1 and HR2, a lens group L2 and L3, a pair of reflectors HR3, HR4 and a lambda/2 wave plate HWP3, and generating elliptically polarized light through a polarization beam splitter prism PBS2 and a lambda/4 wave plate QWP 3;

step 4, finally, vertically irradiating the laser beam into the hyperstable cavity from a third window interface C of the plane cavity mirror 4 with the coating frequency 397nm and the reflectivity of 99.95% through a pair of reflectors HR5 and HR6, wherein the pair of reflectors HR5 and HR6 are used for adjusting the mode of the laser to be matched with the mode of the hyperstable cavity, and the coupling efficiency is enabled to reach the maximum value;

and 5, repeatedly reflecting the laser in the super-stable cavity F-PCavity, wherein when the laser frequency is not consistent with the laser frequency matched with the super-stable cavity, the laser is provided with the laserThe film coating frequency is 397nm and the reflectivity is 99.95 percent, the eighth window plate window H of the concave cavity mirror 5 is reflected and then is transmitted out through a third window plate interface C provided with the plane cavity mirror 4 with the reflectivity of 99.95 percent, the laser with the frequency jitter information passes through the lambda/4 wave plate QWP3 and the linearly polarized light of the polarization beam splitter PBS2 again, and the linearly polarized light passes through the photoelectric detector PD1 and the mixer at delta_mDemodulation, in which the phase of the phase shifter is adjusted to obtain a dispersion signal of modulation transfer, which is used as a frequency discrimination signal (PDH signal), a photodetector PD2 is used to monitor the photoelectric signal transmitted through the eighth window H equipped with the concave cavity mirror 5, and a CCD is used to observe and detect the laser mode;

and 6, transmitting the obtained dispersion signal subjected to modulation transfer to a digital circuit module controller based on PID (proportion integration differentiation) through a low-pass bandwidth type filter, and continuously adjusting a driving signal of the laser according to the deviation of feedback information and a set value so as to inhibit external interference and enable the laser frequency to tend to be stable at omega + omega or omega-omega_mThat is, the laser is stabilized at f ═ ω' ═ 755.222800THz, and the lock time is as long as 11 hours.

And 7, if the stabilized frequency needs to be finely adjusted, the frequency can be adjusted by adjusting the output frequency of a signal source (within the range of the resonance frequency of the EOM), so that the laser frequency can be stabilized for a long time

The above embodiments are only for illustrating the technical concept and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention accordingly, and not to limit the protection scope of the present invention accordingly. All equivalent changes or modifications made in accordance with the spirit of the present disclosure are intended to be covered by the scope of the present disclosure.