阅读说明：本技术 一种基于调制转移谱的稳频装置 (Frequency stabilizer based on modulation transfer spectrum ) 是由 周超 付小虎 张磊 于 2021-08-31 设计创作，主要内容包括：本发明涉及激光稳频技术领域,尤其涉及一种基于调制转移谱的稳频装置,包括第一分束单元,用以接收待稳频激光信号,并根据所述待稳频激光信号形成第一分光信号和第二分光信号,所述第一分光信号用于形成探测光信号；铌酸锂波导型电光相位调制器,用以接收所述第二分光信号,根据所述第二分光信号形成调制光信号；第二分束单元,用以接收一准直调制光信号,用以根据所述准直调制光信号形成第一准直调制分光信号和第二准直调制分光信号；原子吸收池,用以分别接收所述探测光信号和所述第一准直调制分光信号,根据所述第一准直调制分光信号对所述探测光做调制转移以形成一稳频激光基础信号输出。(The invention relates to the technical field of laser frequency stabilization, in particular to a frequency stabilization device based on a modulation transfer spectrum, which comprises a first beam splitting unit, a second beam splitting unit and a third beam splitting unit, wherein the first beam splitting unit is used for receiving a laser signal to be frequency stabilized and forming a first light splitting signal and a second light splitting signal according to the laser signal to be frequency stabilized, and the first light splitting signal is used for forming a detection light signal; the lithium niobate waveguide type electro-optic phase modulator is used for receiving the second split optical signal and forming a modulated optical signal according to the second split optical signal; the second beam splitting unit is used for receiving a collimated modulated optical signal and forming a first collimated modulated optical splitting signal and a second collimated modulated optical splitting signal according to the collimated modulated optical signal; and the atomic absorption cell is used for respectively receiving the detection light signal and the first collimation modulation splitting signal and carrying out modulation transfer on the detection light according to the first collimation modulation splitting signal so as to form frequency stabilization laser basic signal output.)

1. A frequency stabilization apparatus based on modulation transfer spectrum, comprising:

the device comprises a first beam splitting unit, a second beam splitting unit and a control unit, wherein the first beam splitting unit is used for receiving a laser signal to be frequency stabilized and forming a first light splitting signal and a second light splitting signal according to the laser signal to be frequency stabilized, and the first light splitting signal is used for forming a detection light signal;

the lithium niobate waveguide type electro-optic phase modulator is used for receiving the second split optical signal and forming a modulated optical signal according to the second split optical signal;

the second beam splitting unit is matched with the first beam splitting unit and used for receiving a collimated modulation optical signal and forming a first collimated modulation optical splitting signal and a second collimated modulation optical splitting signal according to the collimated modulation optical signal;

and the atomic absorption cell is used for respectively receiving the detection light signal and the first collimation modulation splitting signal and carrying out modulation transfer on the detection light according to the first collimation modulation splitting signal so as to form frequency stabilization laser basic signal output.

2. The frequency stabilization apparatus based on modulation transfer spectrum according to claim 1, further comprising:

the first collimating unit is used for receiving the first optical splitting signal and collimating the first optical splitting signal to form a detection optical signal.

3. The frequency stabilization apparatus based on modulation transfer spectrum according to claim 1, further comprising:

and the second collimation unit is used for receiving the modulated optical signal and forming a collimated modulated optical signal according to the modulated optical signal.

4. The modulation transfer spectrum-based frequency stabilization device of claim 1, wherein the power of the first split optical signal is smaller than the power of the second split optical signal.

5. The frequency stabilizer based on modulation transfer spectrum according to claim 1, wherein the first beam splitting unit is one of a polarization beam splitter, a beam splitter, or,

the first beam splitting unit is an optical fiber beam splitter.

6. The frequency stabilization apparatus based on modulation transfer spectrum according to claim 1, further comprising,

a first polarization maintaining unit arranged between the electro-optical modulator and the first beam splitting unit;

and the second polarization maintaining unit is arranged between the electro-optical modulator and the second beam splitting unit.

7. The frequency stabilization device based on modulation transfer spectrum of claim 1, further comprising a photodetector for receiving the frequency-stabilized laser basic signal reflected by the second beam splitting unit and outputting the frequency-stabilized laser basic signal.

8. The frequency stabilization apparatus based on modulation transfer spectrum according to claim 7, further comprising:

the processing unit is used for receiving the frequency stabilized laser basic signal and forming a frequency discrimination curve of a modulation transfer spectrum according to the frequency stabilized laser basic signal;

and the frequency locking unit is used for carrying out frequency locking treatment on the frequency stabilized laser basic signal according to the frequency discrimination curve so as to form a frequency stabilized laser signal.

9. The frequency stabilization device based on modulation transfer spectrum according to claim 1, wherein: the range of the ratio of the power of the probe optical signal to the power of the first collimated modulated split optical signal is 1: 1 to 1: 2.5.

Technical Field

The invention relates to the technical field of laser frequency stabilization, in particular to a frequency stabilization device based on a modulation transfer spectrum.

Background

In modern physical experiments such as cold atom physical experiments and quantum information experiments, laser with stable frequency is the most basic experimental tool. In these experiments, the frequency stability of the laser will directly affect the accuracy of the experiment, and a frequency stabilization technique with high accuracy and good stability is indispensable for ensuring the frequency stability of the laser. Among the existing various laser frequency stabilization techniques, modulation transfer spectrum frequency stabilization has unique advantages. The modulation transfer spectrum is a spectrum generated by utilizing the interaction of atoms and laser, the spectral line of the spectrum is a dispersion-like linear curve without Doppler background, the central zero point corresponds to the resonance transition peak of the atoms, the zero point does not change with the fluctuation of the power of the laser theoretically, and the spectral line has a larger slope near the zero point, so that the laser frequency stabilization by using the modulation transfer spectrum has the advantages of high frequency stabilization precision, good stability and the like.

The modulation transfer spectrum needs to modulate the probe light, and the existing modulation transfer spectrum frequency stabilization technology usually adopts a resonance circuit to drive an electro-optical crystal to perform phase modulation on the laser. The half-wave voltage of a common electro-optical crystal is as high as hundreds of even thousands of volts, and the amplitude of the modulation voltage needs to be high enough to realize larger modulation depth, and a voltage amplifier is often needed for driving. If the crystal is driven by the resonance device, although the half-wave voltage of the working mode is low, a resonance LC circuit needs to be built outside the crystal, the electro-optical modulator can only work at the resonance frequency, and if the modulation frequency is required to be changed, the electronic components need to be replaced to change the resonance frequency in the LC resonance circuit, so that the operation is inconvenient. The resonant electro-optic modulator is limited by the driving method, is large in size, and can only be modulated by adopting a spatial light incidence method. On one hand, the spatial light path needs various optical elements and matched mechanical parts for construction and adjustment, and is not suitable for integration and miniaturization; on the other hand, the modulation process is influenced by the polarization direction and the incident angle of incident light, so that the problem of residual amplitude modulation is caused, the spectral line zero point is changed, the frequency of the laser after frequency stabilization is changed, the incident angle of the space light is difficult to control well, and the frequency stabilization effect of the laser is influenced. In summary, the modulation transfer spectrum frequency stabilization system constructed by the existing electro-optic modulator driven by the resonance device is limited by a spatial light path and a driving mode, is inconvenient to operate, is difficult to miniaturize and integrate, and can influence the frequency stabilization result.

Disclosure of Invention

In view of the deficiencies of the prior art, the present application provides a frequency stabilizer based on modulation transfer spectrum, and particularly,

a frequency stabilizer based on modulation transfer spectrum comprises

The first beam splitting unit is used for receiving a laser signal to be frequency stabilized and forming a first light splitting signal and a second light splitting signal according to the laser signal to be frequency stabilized, wherein the first light splitting signal is used for forming a detection light signal,

the lithium niobate waveguide type electro-optic phase modulator is used for receiving the second split optical signal and forming a modulated optical signal according to the second split optical signal;

the second beam splitting unit is used for receiving a collimated modulated optical signal and forming a first collimated modulated optical splitting signal and a second collimated modulated optical splitting signal according to the collimated modulated optical signal;

and the atomic absorption cell is used for respectively receiving the detection light signal and the first collimation modulation splitting signal and carrying out modulation transfer on the detection light according to the first collimation modulation splitting signal so as to form frequency stabilization laser basic signal output.

Preferably, the frequency stabilization device based on modulation transfer spectrum further includes a first collimating unit, configured to receive the first optical splitting signal, and perform collimation processing on the first optical splitting signal to form a probe optical signal.

Preferably, the frequency stabilization device based on modulation transfer spectrum further includes a second collimating unit, configured to receive the modulated optical signal, and form a collimated modulated optical signal according to the modulated optical signal.

Preferably, in the frequency stabilizing apparatus based on modulation transfer spectrum, a power of the first split optical signal is smaller than a power of the second split optical signal.

Preferably, in the frequency stabilizer based on modulation transfer spectrum, the first beam splitting unit is one of a polarization beam splitter prism, a beam splitter prism and a beam splitter, or the first beam splitting unit is an optical fiber beam splitter.

Preferably, the frequency stabilizing device based on modulation transfer spectrum further comprises,

a first polarization maintaining unit arranged between the electro-optical modulator and the first beam splitting unit;

and the second polarization maintaining unit is arranged between the electro-optical modulator and the second beam splitting unit.

Preferably, the frequency stabilization device based on modulation transfer spectrum further includes a photodetector for receiving the frequency-stabilized laser basic signal reflected by the second beam splitting unit and outputting the frequency-stabilized laser basic signal.

Preferably, the frequency stabilizing apparatus based on modulation transfer spectrum further includes:

the processing unit is used for receiving the frequency stabilized laser basic signal and forming a frequency discrimination curve of a modulation transfer spectrum according to the frequency stabilized laser basic signal;

and the frequency locking unit is used for carrying out frequency locking treatment on the frequency stabilized laser basic signal according to the frequency discrimination curve so as to form a frequency stabilized laser signal.

Preferably, in the frequency stabilization apparatus based on modulation transfer spectrum, a ratio of the power of the probe optical signal to the power of the first collimated modulated split optical signal ranges from 1: 1 to 1: 2.5.

compared with the prior art, the beneficial effects of this application are:

according to the invention, the traditional resonance drive type electro-optic modulator is replaced by the optical fiber type lithium niobate waveguide type electro-optic phase modulator, and the modulation transfer spectrum module which can be used for long-term stable frequency stabilization of laser is built, and the module has the advantages of integration and miniaturization, is convenient to operate and is easy to adjust. The module can provide a good frequency stabilization scheme for modern physical experiments such as cold atom physics and quantum information.

Drawings

Fig. 1 is a schematic structural diagram of a frequency stabilizer based on modulation transfer spectrum according to an embodiment of the present invention;

fig. 2 is a schematic structural diagram of a frequency stabilizer based on modulation transfer spectrum according to an embodiment of the present invention;

fig. 3 is a schematic structural diagram of a frequency stabilizer based on modulation transfer spectrum according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

As shown in fig. 1, the present application provides a frequency stabilization apparatus based on modulation transfer spectrum, which includes:

the first beam splitting unit 11 is configured to receive a laser signal to be frequency stabilized, and form a first optical splitting signal and a second optical splitting signal according to the laser signal to be frequency stabilized; further, the power of the first split optical signal is less than the power of the second split optical signal.

Further, the first beam splitting unit is one of a polarization beam splitter prism, a beam splitter prism and a beam splitter, or the first beam splitting unit is an optical fiber beam splitter. When the laser signal to be frequency stabilized is spatial light, the first beam splitting unit is one of a polarization beam splitter prism, a beam splitter prism and a beam splitter. When the laser signal to be frequency stabilized is an optical fiber incident light signal, the first beam splitting unit is an optical fiber beam splitter.

A first collimating unit 13, configured to receive the first optical splitting signal, and collimate the first optical splitting signal to form a probe optical signal; the first split optical signal is intended to be incident collinearly into an atomic absorption cell.

A lithium niobate waveguide type electro-optic phase modulator 12, configured to receive the second split optical signal and form a modulated optical signal according to the second split optical signal; the modulation light signal is nearly pure phase modulation light, the half-wave voltage of the lithium niobate waveguide type electro-optic phase modulator is only less than 5V, the working range is DC-300MHz, the driving is easy, the adjustable range is large, the integral volume of the device is small, and the form of optical fiber connection is adopted, so that the integration and miniaturization of an optical path are facilitated; secondly, the angle of incident light is well controlled by adopting an optical fiber connection mode, and the device per se is also subjected to polarization control, so that the influence caused by laser polarization fluctuation is avoided, and the residual amplitude modulation component in the modulated pump light can be well controlled.

A second collimating unit 14, configured to receive the modulated optical signal and form a collimated modulated optical signal according to the modulated optical signal;

a second beam splitting unit 16, which is matched with the first beam splitting unit, and configured to receive the collimated modulated optical signal, and form a first collimated modulated optical splitting signal and a second collimated modulated optical splitting signal according to the collimated modulated optical signal; the light splitting ratio ensures that the first collimation modulation light splitting power received by the atomic absorption cell is 1-2 times of the detection light power so as to obtain the optimal modulation transfer spectrum signal, wherein the second collimation modulation light splitting signal is reflected and abandoned, and the first collimation modulation light splitting signal is incident into the atomic absorption cell. The second beam splitting unit is used for attenuating the collimated and modulated optical signal to form a first collimated and modulated beam splitting signal on one hand, and is used for reflecting the frequency stabilized laser basic signal on the other hand, so that the frequency stabilized laser basic signal is transmitted to the photoelectric detection unit.

And the atomic absorption cell 15 is configured to receive the probe light and the first collimated modulation splitting signal, and perform modulation transfer on the probe light according to the first collimated modulation splitting signal to form a frequency stabilized laser basic signal output.

And the photoelectric detection unit 17 is used for receiving and outputting the frequency-stabilized laser basic signal reflected by the second beam splitting unit.

The working principle of the frequency stabilizer based on the modulation transfer spectrum is as follows: the power of the laser to be frequency stabilized is 1-10 mW, and the incident laser to be frequency stabilized is divided into a first splitting signal and a second splitting signal with different powers after passing through the first splitting unit, wherein the power of the first splitting signal is small, for example, the first splitting signal can be used as a detection light basic signal, and the power of the second splitting signal is strong, for example, the second splitting signal can be used as a pumping light basic signal. The first light splitting signal passes through a first collimating unit, the first collimating unit forms a detection light signal according to the first light splitting signal, and the detection light signal is a collimated laser signal. The detection light signal enters the atomic absorption cell. And the second light splitting signal enters an electro-optical modulation unit, the electro-optical modulation unit performs phase modulation on the second light splitting signal to form a modulated optical signal, the modulated optical signal forms a collimated modulated optical signal through a second collimation unit, and the collimated modulated optical signal and the detection optical signal are oppositely incident into an atomic absorption cell. The modulation transfer process is carried out between the collimation modulation optical signal and the detection optical signal, a certain sideband is generated in the detection optical signal to form the frequency stabilization laser basic signal in the modulation transfer process, the principle of the detection optical signal sideband generation is the four-wave mixing effect of different optical signals in an atomic absorption pool, the frequency of the sideband and the detection optical frequency difference are equal to the modulation signal frequency, the amplitude is simultaneously influenced by the modulation signal amplitude and the atomic medium in the atomic absorption pool, and therefore the frequency stabilization laser basic signal can carry modulation information and atomic spectral line information.

Further, the device also comprises a first polarization maintaining unit arranged between the electro-optical modulator and the first beam splitting unit; the first polarization maintaining unit is used for performing polarization maintaining processing on the second split optical signal so that the second split optical signal can stably enter the electro-optical modulator.

And the second polarization maintaining unit is arranged between the electro-optical modulator and the second beam splitting unit. The second polarization maintaining unit is used for performing polarization maintaining processing on the modulated optical signal so that the modulated optical signal can stably enter the second beam splitting unit.

The first polarization maintaining unit and the second polarization maintaining unit are formed by polarization maintaining optical fibers.

Further, the above frequency stabilizer based on modulation transfer spectrum further includes:

the processing unit is used for receiving the frequency stabilized laser basic signal and forming a frequency discrimination curve of a modulation transfer spectrum according to the frequency stabilized laser basic signal;

and the frequency locking unit is used for carrying out frequency locking treatment on the frequency stabilized laser basic signal according to the frequency discrimination curve so as to form a frequency stabilized laser signal.

Specifically, when the laser to be frequency-stabilized is input into the first beam splitting unit, the frequency of the laser to be frequency-stabilized is scanned, and the fundamental signal of the frequency-stabilized laser obtained by the photodetector is correspondingly amplified, demodulated, filtered and the like to obtain a frequency discrimination curve of the modulation transfer spectrum, and the frequency of the laser can be locked on a zero point of the frequency discrimination curve by using the frequency locking module through the frequency discrimination curve.

Because the pump light basically does not contain amplitude modulation components, the obtained zero point of the frequency discrimination curve corresponds to the resonance absorption peak of atoms well, and the modulation transfer spectrum is insensitive to the fluctuation of laser power, so that the zero point position of the frequency discrimination curve is stable, and the laser signal with better frequency precision and stability can be obtained by utilizing the module to carry out frequency stabilization.

As shown in fig. 2, in an example of spatial light modulation transfer spectrum frequency stabilization, in this example, a laser a1 to be frequency-stabilized that is spatially incident is divided into a first split optical signal and a second split optical signal that are vertically polarized by a polarization splitting prism 20, the first split optical signal generates collimated probe light a2 through a first collimating unit 23, the second split optical signal is coupled by an optical fiber coupler 29 and then enters an optical fiber electro-optical modulator 22 to form a modulated optical signal, and the modulated optical signal forms a first collimated modulated split optical signal a3 through a second collimating unit 24 and enters an atomic absorption cell 25 after entering a second splitting unit.

As shown in fig. 3, an example of frequency stabilization of modulation-transferred spectrum of fiber incident light is shown, in this example, laser light a1 to be frequency stabilized incident through a fiber is split into two laser beams by a fiber beam splitter 30, and a first collimating unit 31, a second collimating unit 34, an atomic absorption cell 35, a second beam splitting unit 36 and a photodetector 37 are integrally fixed in a stainless steel housing 40.

The optical fiber electro-optic modulator is small in size, and the space occupied by a modulation optical path is greatly reduced by adopting an optical fiber connection mode, so that the integration is facilitated. Taking the spatial light frequency stabilization and fiber incident light frequency stabilization module shown in fig. 2 and 3 as an example, in the example shown in fig. 3, a laser to be frequency stabilized enters through a fiber, a fiber beam splitter is used for splitting the laser beam, a first collimation unit, a second collimation unit, an atomic absorption cell, a second beam splitting unit and a photoelectric detector are fixed in a stainless steel shell to serve as a small fiber optical path module, and all the components are connected by polarization-maintaining fibers, so that the integration and miniaturization of the whole module can be ensured. The integrated module only needs to reserve three interfaces under the condition that all parts are fixed, one optical interface is used for inputting the laser to be frequency stabilized, and the two circuit interfaces are respectively used for inputting a modulation signal and outputting a detection signal, so that the operation is convenient and the stability is good.

By selecting devices with different wavelengths and atomic absorption pools of different types, the frequency stabilizing device based on the modulation transfer spectrum can provide corresponding modulation transfer spectrum lines for lasers with different wavelengths. For example, different alkali metal atom absorption cells or iodine molecule absorption cells and devices with corresponding wavelengths are used, so that the frequency stabilization of laser with wavelengths corresponding to 532nm, 671nm, 780nm, 852nm and other resonance transition spectral lines can be realized.

A small optical fiber lithium niobate waveguide type electro-optic modulator is adopted, and a modulation transfer optical path part is integrated or modularized, so that the integral integration level is high; the optical fiber lithium niobate waveguide type electro-optic modulator is accessed by an optical fiber and has good polarization characteristic, thereby improving the stability of the laser in the modulation process and the modulation transfer process, ensuring the stability of the modulation transfer spectrum line and being suitable for the long-term stable frequency stabilization of the laser; a frequency stabilization device based on modulation transfer spectrum only needs one optical path interface and two circuit interfaces after being integrated, is convenient to operate when used for frequency stabilization, has low half-wave voltage and large working bandwidth of an electro-optical modulator, and can work under different modulation signals according to requirements; by replacing optical devices with different wavelengths, the structure of the invention is suitable for all lasers which can adopt modulation transfer spectrum frequency stabilization.

In summary, the invention provides a conveniently used, miniaturized and integrated modulation transfer spectrum module using a low-voltage and high-bandwidth optical fiber lithium niobate waveguide electro-optic modulator. The module can be suitable for the frequency stability of various different frequency lasers, and the precision and the stability of frequency stabilization can both be guaranteed.

It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus.

Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.