阅读说明：本技术 应用于冷原子喷泉钟的小型化主激光光路装置及调整方法 (Miniature main laser light path device applied to cold atom fountain clock and adjusting method ) 是由 陈伟亮 李天初 房芳 戴少阳 刘昆 于 2021-08-19 设计创作，主要内容包括：本发明提供一种应用于冷原子喷泉钟的小型化主激光光路装置,包括光纤耦合器、HP旋转组合模块与猫眼双次通过声光调制模块,用于冷原子喷泉钟的稳频主激光经保偏光纤传输后由光纤耦合器准直输出到自由空间,经HP旋转组合模块进行分光,分为探测光、向上和向下冷却光,探测光、向上和向下冷却光分别进入三个猫眼双次通过声光调制模块做激光的频率和幅度控制后,通过1/4波片和1/2波片组合后再入射到对应的光纤耦合器耦合进入保偏光纤,进而分别用作冷原子喷泉钟所需的探测光、向上和向下冷却光。本发明具有约束光路走向,降低光高,提升冷原子喷泉钟光路稳定性的优点。本发明还提供一种应用于冷原子喷泉钟的小型化主激光光路装置的调整方法。(The invention provides a miniaturized main laser light path device applied to a cold atom fountain clock, which comprises an optical fiber coupler, an HP rotary combination module and a cat eye double-pass acousto-optic modulation module, wherein frequency-stabilized main laser used for the cold atom fountain clock is transmitted through polarization-maintaining optical fibers, then is collimated and output to a free space through the optical fiber coupler, is subjected to light splitting through the HP rotary combination module and is divided into detection light, upward cooling light and downward cooling light, the detection light, the upward cooling light and the downward cooling light respectively enter three cat eye double-pass acousto-optic modulation modules to be subjected to frequency and amplitude control of the laser, are combined through 1/4 wave plates and 1/2 wave plates and then enter corresponding optical fiber couplers to be coupled into polarization-maintaining optical fibers, and further are respectively used as the detection light, the upward cooling light and the downward cooling light required by the cold atom fountain clock. The invention has the advantages of restricting the trend of the light path, reducing the light height and improving the stability of the light path of the cold atom fountain clock. The invention also provides an adjusting method of the miniaturized main laser light path device applied to the cold atom fountain clock.)

1. A miniaturized main laser optical path device applied to a cold atom fountain clock is characterized by comprising an optical fiber coupler, an HP rotary combined module and a cat eye double-pass acousto-optic modulation module,

the frequency-stabilized main laser used for the cold atom fountain clock is transmitted by polarization maintaining optical fibers, then is output to a free space in a collimating way through an optical fiber coupler, is split by an HP rotating combined module and is divided into detection light, upward cooling light and downward cooling light, the detection light, the upward cooling light and the downward cooling light respectively enter three cat eyes, are subjected to frequency and amplitude control of laser through an acousto-optic modulation module for two times, are combined through 1/4 wave plates and 1/2 wave plates and then enter the corresponding optical fiber coupler to be coupled and enter the polarization maintaining optical fibers, and then are respectively used as the detection light, the upward cooling light and the downward cooling light required by the cold atom fountain clock.

2. The miniaturized main laser optical path device applied to a cold atom fountain clock of claim 1, wherein the fiber coupler comprises a first fiber coupler, a second fiber coupler, a third fiber coupler and a fourth fiber coupler, the HP rotation combination module comprises a first HP rotation combination module, a second HP rotation combination module, a third HP rotation combination module and a fourth HP rotation combination module,

the frequency-stabilized main laser used for the cold atom fountain clock is transmitted by a polarization maintaining optical fiber and then is output in a collimating way by the first optical fiber coupler, and then is subjected to light splitting by the first HP rotary combined module, the second HP rotary combined module, the third HP rotary combined module and the fourth HP rotary combined module in sequence, the first HP rotary combined module is used for fixing the polarization state of the emergent laser of the optical fiber, so that the light splitting ratio of the second HP rotary combined module, the third HP rotary combined module and the fourth HP rotary combined module cannot change along with the polarization jitter of the incident optical fiber, and a reflected light beam split by the second HP rotary combined module is used as detection light; the reflected light beam split by the third HP rotation combining module is used as an upward cooling light, and the reflected light beam split by the fourth HP rotation combining module is used as a downward cooling light;

the detection light, the upward cooling light and the downward cooling light respectively enter three cat eyes to pass through the acousto-optic modulation module for two times to control the frequency and the amplitude of laser, are combined through 1/4 wave plates and 1/2 wave plates and then respectively enter corresponding second optical fiber couplers, third optical fiber couplers and fourth optical fiber couplers to be coupled and enter polarization-maintaining optical fibers.

3. The miniaturized main laser optical path device applied to a cold atom fountain clock is characterized in that the cat eye double-pass acousto-optic modulation module comprises a vertical acousto-optic modulator, a lens, an 1/4 wave plate and a reflector which are sequentially arranged, the 1/4 wave plate is used for adjusting the polarization direction of a light beam, a collimated light beam generates a deflection light beam after frequency shift of the vertical acousto-optic modulator, a zero-order light beam and a + 1-order light beam are focused by the lens after the focal distance of the lens is transmitted, the focal point is located on the mirror surface of the reflector, the reflected light returns as the original path, and the + 1-order light beam which passes through the lens and the vertical acousto-optic modulator for the second time coincides with an incident light beam.

4. The miniaturized primary laser optical path device applied to a cold atom fountain clock of claim 3, wherein the vertical acousto-optic modulator comprises a vertical adapter and an acousto-optic modulator, the vertical adapter is fixedly connected with the acousto-optic modulator, the vertical adapter is fixed on an optical plane through a rotating shaft, and the vertical adapter rotates around the rotating shaft.

5. The miniaturized primary laser optical path device applied to a cold atom fountain clock of claim 3, wherein the lens is a lens with a focal length of an integral multiple of 25 mm.

6. The miniaturized main laser optical path device applied to a cold atom fountain clock as claimed in claim 1, wherein the HP rotary combination module comprises an adapter, a rotary frame for mounting 1/2 wave plate, a mounting table for mounting PBS, and a rotary frame for connecting PBS mounting table,

the HP rotation combination module is used for providing a polarization beam splitting function of a collimated light beam and a pitch and horizontal deflection adjusting function of the PBS reflection direction;

the rotating frame for mounting the 1/2 wave plate and the rotating frame for mounting the switching PBS mounting table are fixed on the adapter through screws and used for adjusting the processing height of the adapter, so that the center height of the light-passing hole of the rotating frame for mounting the 1/2 wave plate and the rotating frame for mounting the switching PBS mounting table after mounting is kept consistent with the light height of the light path device through adjusting the processing height of the adapter.

7. The miniaturized primary laser optical path device applied to a cold atom fountain clock according to claim 1, wherein the optical path device is horizontally and vertically arranged according to a connection line of centers of standard optical flat fixing holes, and the optical path device is arranged in the shortest distance according to the optical path function.

8. The miniaturized primary laser optical path device applied to a cold atom fountain clock according to claim 1, wherein the optical fiber coupler is a five-axis optical fiber coupler.

9. The method for adjusting the miniaturized main laser beam path device applied to the cold atom fountain clock as claimed in claim 1, comprising the steps of:

the method comprises the following steps: collimation and light height adjustment of primary laser light

Connecting a polarization maintaining optical fiber for outputting main laser to an optical fiber coupler to output a collimated light beam, adjusting the position of a collimating lens of the optical fiber coupler, and optimizing the collimation degree of the light beam;

adjusting an XY direction knob of the optical fiber coupler to enable light beams to be parallel to the optical flat plate on the optical path light height plane, and distributing along the central connecting line of the optical flat plate fixing hole according to the optical path light height requirement;

step two: HP rotary modular regulation

The collimated light beams are subjected to light splitting sequentially through the four HP rotary combination modules, and most of the output light of the optical fiber is adjusted into transmission output by the first HP rotary combination module and used for fixing the polarization state of the laser light emitted by the optical fiber; the reflected light beam split by the second HP rotation combining module is used as detection light; the reflected light beam split by the third HP rotation combining module is used as an upward cooling light, and the reflected light beam split by the fourth HP rotation combining module is used as a downward cooling light;

the reflected light beams of all the HP rotary combination modules are horizontally and vertically distributed along the central connecting line of the fixed holes of the optical flat plate on the fixed light height according to the light path distribution requirement;

step three: vertical acousto-optic modulator modulation

The vertical acousto-optic modulator comprises an acousto-optic modulator and a vertical adapter, the acousto-optic modulator is fixedly connected with the vertical adapter, and the center position of a transducer of the acousto-optic modulator is positioned through a positioning hole in the vertical adapter and is fixed on the optical height required by the layout of an optical path;

collimated light beams enter the vertical acousto-optic modulator from the horizontal direction, and the efficiency of the acousto-optic modulator is optimized by rotating the acousto-optic modulator in the vertical direction and rotating the vertical adapter in the horizontal direction;

step four: adjustment of cat eye through acousto-optic modulation module twice

The detection light, the upward cooling light and the downward cooling light which are separated by the HP rotation combination module pass through the acousto-optic modulation module twice respectively through the corresponding cat eye to realize the frequency and amplitude control of the laser;

step five: free space to polarization maintaining fiber coupling conditioning

After the cat eye passes through the acousto-optic modulation module twice, free space beams of detection light, upward cooling light and downward cooling light transmitted by the corresponding HP rotation combination module need to be coupled into the corresponding three polarization-maintaining optical fibers for transmission;

the coupling of each polarization maintaining fiber comprises a fiber coupler, an 1/2 wave plate and a 1/4 wave plate, the focal length, the pitch, the inclination and the XY directions of a lens of the fiber coupler are adjusted, and the fiber coupling efficiency from a free space to the polarization maintaining fiber is realized.

10. The adjusting method of the miniaturized main laser optical path device applied to the cold atom fountain clock is characterized in that 1/2 wave plates and PBS are arranged on the HP rotary combination module, the HP rotary combination module comprises an adapter, a rotary frame for mounting 1/2 wave plates, a mounting table for mounting the PBS and a rotary frame for mounting the PBS, and the rotary frame for mounting the 1/2 wave plates and the rotary frame for mounting the PBS are fixed on the adapter through screws;

the light beam passes through 1/2 wave plate and PBS in turn, and the rotating frame provided with 1/2 wave plate is rotated to realize the splitting ratio of PBS in the transmission and reflection directions;

the rotary frame of the switching PBS mounting table is rotated to realize the adjustment of the pitching direction of the PBS reflected light beam, and the switching base is rotated to realize the adjustment of the horizontal direction of the PBS reflected light beam.

Technical Field

The invention belongs to the technical field of laser light paths, and particularly relates to a miniaturized main laser light path device applied to a cold atom fountain clock and an adjusting method.

Background

The cold atom fountain clock is a frequency standard device for realizing atomic transition frequency recurrence, atoms in a vacuum room temperature state are cooled to 1-3 mu K and approach to absolute zero degree through a laser cooling trapping atom technology, cold atoms are thrown upwards through a mobile optical viscose method and react with microwaves in an atom free falling process, and then the quantum state of the atoms is detected through laser, so that the fed-in microwave frequency is locked at the atomic transition frequency. The main laser is used for atom control and detection in a cold atom fountain clock. And main laser output by the main laser is locked on a corresponding transition frequency between an atomic ground state energy level and an atomic excitation energy level through an atomic gas chamber saturated absorption spectrum. The main laser light path is used for light splitting, frequency modulation and polarization control of main laser, and laser frequency, amplitude, polarization and time sequence control requirements required by fountain clock laser cooling are met.

The traditional cold atom fountain clock main laser light path adopts a general optical element and an adjusting frame, the trend of the light path is not restricted, and an acousto-optic modulator is horizontally arranged, so that the occupied area is larger, the general light path area is larger than 1.2m by 0.9m, the light path length is longer, the light height is higher, and the instability of the system is increased.

Disclosure of Invention

Some embodiments of the invention provide a miniaturized main laser light path device applied to a cold atom fountain clock, and solve the technical problems that the traditional cold atom fountain clock adopts a general optical element and an adjusting frame as a main laser light path, the trend of the light path is not restricted, an acousto-optic modulator is horizontally arranged, the occupied area is large, the light path of the light path is long, the light height is high, and the instability of the system is increased.

The invention provides a miniaturized main laser light path device applied to a cold atom fountain clock, which comprises an optical fiber coupler, an HP rotary combined module and a cat eye double-pass acousto-optic modulation module,

the frequency-stabilized main laser used for the cold atom fountain clock is transmitted by polarization maintaining optical fibers, then is output to a free space in a collimating way through an optical fiber coupler, is split by an HP rotating combined module and is divided into detection light, upward cooling light and downward cooling light, the detection light, the upward cooling light and the downward cooling light respectively enter three cat eyes, are subjected to frequency and amplitude control of laser through an acousto-optic modulation module for two times, are combined through 1/4 wave plates and 1/2 wave plates and then enter the corresponding optical fiber coupler to be coupled and enter the polarization maintaining optical fibers, and then are respectively used as the detection light, the upward cooling light and the downward cooling light required by the cold atom fountain clock.

Preferably, the fiber coupler includes a first fiber coupler, a second fiber coupler, a third fiber coupler, and a fourth fiber coupler, the HP rotation combining module includes a first HP rotation combining module, a second HP rotation combining module, a third HP rotation combining module, and a fourth HP rotation combining module,

the frequency-stabilized main laser used for the cold atom fountain clock is transmitted by a polarization maintaining optical fiber and then is output in a collimating way by the first optical fiber coupler, and then is subjected to light splitting by the first HP rotary combined module, the second HP rotary combined module, the third HP rotary combined module and the fourth HP rotary combined module in sequence, the first HP rotary combined module is used for fixing the polarization state of the emergent laser of the optical fiber, so that the light splitting ratio of the second HP rotary combined module, the third HP rotary combined module and the fourth HP rotary combined module cannot change along with the polarization jitter of the incident optical fiber, and a reflected light beam split by the second HP rotary combined module is used as detection light; the reflected light beam split by the third HP rotation combining module is used as an upward cooling light, and the reflected light beam split by the fourth HP rotation combining module is used as a downward cooling light;

the detection light, the upward cooling light and the downward cooling light respectively enter three cat eyes to pass through the acousto-optic modulation module for two times to control the frequency and the amplitude of laser, are combined through 1/4 wave plates and 1/2 wave plates and then respectively enter corresponding second optical fiber couplers, third optical fiber couplers and fourth optical fiber couplers to be coupled and enter polarization-maintaining optical fibers.

Preferably, the cat eye double-pass acousto-optic modulation module comprises a vertical acousto-optic modulator, a lens, an 1/4 wave plate and a reflector which are sequentially arranged, wherein the 1/4 wave plate is used for adjusting the polarization direction of light beams, collimated light beams generate deflected light beams after frequency shift of the collimated light beams by the vertical acousto-optic modulator, zero-order light beams and + 1-order light beams after transmission of the focal distance of the lens are focused by the lens, the focal point of the zero-order light beams and the + 1-order light beams after transmission of the focal distance of the lens are located on the mirror surface of the reflector, reflected light returns according to the original path, and the + 1-order light beams after passing through the lens and the vertical acousto-optic modulator for the second time coincide with the incident light beams.

Preferably, the vertical acousto-optic modulator comprises a vertical adapter and an acousto-optic modulator, the vertical adapter is fixedly connected with the acousto-optic modulator, the vertical adapter is fixed on an optical plane through a rotating shaft, and the vertical adapter rotates around the rotating shaft.

Preferably, the lens is a lens with a focal length of an integer multiple of 25 mm.

Preferably, the HP rotary combination module comprises an adapter, a rotary frame for mounting the 1/2 wave plate, a mounting table for mounting the PBS, and a rotary frame for connecting the PBS mounting table,

the HP rotation combination module is used for providing a polarization beam splitting function of a collimated light beam and a pitch and horizontal deflection adjusting function of the PBS reflection direction;

the rotating frame for mounting the 1/2 wave plate and the rotating frame for mounting the switching PBS mounting table are fixed on the adapter through screws and used for adjusting the processing height of the adapter, so that the center height of the light-passing hole of the rotating frame for mounting the 1/2 wave plate and the rotating frame for mounting the switching PBS mounting table after mounting is kept consistent with the light height of the light path device through adjusting the processing height of the adapter.

Preferably, the optical path device is arranged horizontally and vertically according to a connecting line of centers of the standard optical flat fixing holes, and the optical path device is arranged in the shortest distance according to the optical path function.

Preferably, the optical fiber coupler is a five-axis optical fiber coupler.

The invention also provides an adjusting method of the miniaturized main laser light path device applied to the cold atom fountain clock, which comprises the following steps:

the method comprises the following steps: collimation and light height adjustment of primary laser light

Connecting a polarization maintaining optical fiber for outputting main laser to an optical fiber coupler to output a collimated light beam, adjusting the position of a collimating lens of the optical fiber coupler, and optimizing the collimation degree of the light beam;

adjusting an XY direction knob of the optical fiber coupler to enable light beams to be parallel to the optical flat plate on the optical path light height plane, and distributing along the central connecting line of the optical flat plate fixing hole according to the optical path light height requirement;

step two: HP rotary modular regulation

The collimated light beams are subjected to light splitting sequentially through the four HP rotary combination modules, and most of the output light of the optical fiber is adjusted into transmission output by the first HP rotary combination module and used for fixing the polarization state of the laser light emitted by the optical fiber; the reflected light beam split by the second HP rotation combining module is used as detection light; the reflected light beam split by the third HP rotation combining module is used as an upward cooling light, and the reflected light beam split by the fourth HP rotation combining module is used as a downward cooling light;

the reflected light beams of all the HP rotary combination modules are horizontally and vertically distributed along the central connecting line of the fixed holes of the optical flat plate on the fixed light height according to the light path distribution requirement;

step three: vertical acousto-optic modulator modulation

The vertical acousto-optic modulator comprises an acousto-optic modulator and a vertical adapter, the acousto-optic modulator is fixedly connected with the vertical adapter, and the center position of a transducer of the acousto-optic modulator is positioned through a positioning hole in the vertical adapter and is fixed on the optical height required by the layout of an optical path;

collimated light beams enter the vertical acousto-optic modulator from the horizontal direction, and the efficiency of the acousto-optic modulator is optimized by rotating the acousto-optic modulator in the vertical direction and rotating the vertical adapter in the horizontal direction;

step four: adjustment of cat eye through acousto-optic modulation module twice

The detection light, the upward cooling light and the downward cooling light which are separated by the HP rotation combination module pass through the acousto-optic modulation module twice respectively through the corresponding cat eye to realize the frequency and amplitude control of the laser;

step five: free space to polarization maintaining fiber coupling conditioning

After the cat eye passes through the acousto-optic modulation module twice, free space beams of detection light, upward cooling light and downward cooling light transmitted by the corresponding HP rotation combination module need to be coupled into the corresponding three polarization-maintaining optical fibers for transmission;

the coupling of each polarization maintaining fiber comprises a fiber coupler, an 1/2 wave plate and a 1/4 wave plate, the focal length, the pitch, the inclination and the XY directions of a lens of the fiber coupler are adjusted, and the fiber coupling efficiency from a free space to the polarization maintaining fiber is realized.

Preferably, the HP rotating combination module is provided with 1/2 wave plates and PBS, and the HP rotating combination module comprises a transfer seat, a rotating frame for mounting 1/2 wave plates, a mounting table for mounting PBS, and a rotating frame for transferring PBS mounting table, wherein the rotating frame for mounting 1/2 wave plates and the rotating frame for transferring PBS mounting table are fixed on the transfer seat through screws;

the light beam passes through 1/2 wave plate and PBS in turn, and the rotating frame provided with 1/2 wave plate is rotated to realize the splitting ratio of PBS in the transmission and reflection directions;

the rotary frame of the switching PBS mounting table is rotated to realize the adjustment of the pitching direction of the PBS reflected light beam, and the switching base is rotated to realize the adjustment of the horizontal direction of the PBS reflected light beam.

Compared with the prior art, the miniaturized main laser light path device applied to the cold atom fountain clock has the following beneficial effects:

the HP rotary combined module, the vertically-arranged acousto-optic modulator and the cat eye are combined through the acousto-optic modulation module twice to realize the direction of a light path, the light height is reduced, and the stability of the light path of the cold atom fountain clock is improved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic illustration of a primary laser light path of an embodiment of the miniaturized primary laser light path apparatus of the present invention as applied to a cold atom fountain clock;

FIG. 2 is a schematic diagram of an HP rotation combination module of an embodiment of a miniaturized main laser optical path apparatus for a cold atom fountain clock according to the present invention;

FIG. 3 is a schematic diagram of a vertically disposed acousto-optic modulator of an embodiment of the miniaturized main laser optical path apparatus of the present invention applied to a cold atom fountain clock;

fig. 4 is a schematic diagram of a cat eye double-pass acousto-optic modulation module applied to a miniaturized main laser light path device of a cold atom fountain clock.

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. It is to be understood that the described embodiments are merely a few embodiments of the invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without any inventive step, are within the scope of the present invention.

The invention provides a miniaturized main laser light path device applied to a cold atom fountain clock, which comprises an optical fiber coupler, an HP rotary combined module and a cat eye double-pass acousto-optic modulation module. The frequency-stabilized main laser used for the cold atom fountain clock is transmitted by polarization maintaining optical fibers, then is output to a free space in a collimating way through an optical fiber coupler, is split by an HP rotating combined module and is divided into detection light, upward cooling light and downward cooling light, the detection light, the upward cooling light and the downward cooling light respectively enter three cat eyes, are subjected to frequency and amplitude control of laser through an acousto-optic modulation module for two times, are combined through 1/4 wave plates and 1/2 wave plates and then enter the corresponding optical fiber coupler to be coupled and enter the polarization maintaining optical fibers, and then are respectively used as the detection light, the upward cooling light and the downward cooling light required by the cold atom fountain clock.

As shown in fig. 1, the optical fiber coupler includes a first optical fiber coupler, a second optical fiber coupler, a third optical fiber coupler, and a fourth optical fiber coupler, the HP rotation combination module includes a first HP rotation combination module, a second HP rotation combination module, a third HP rotation combination module, and a fourth HP rotation combination module, the frequency stabilization main laser for the cold atom fountain clock is transmitted by a polarization maintaining optical fiber and then collimated by the first optical fiber coupler, and then split light sequentially by the first HP rotation combination module, the second HP rotation combination module, the third HP rotation combination module, and the fourth HP rotation combination module, the first HP rotation combination module is used for fixing the polarization state of the fiber outgoing laser, so that the splitting ratio of the second HP rotation combination module, the third HP rotation combination module, and the fourth HP rotation combination module does not change with the polarization jitter of the incident optical fiber, the reflected light beam split by the second HP rotation combining module is used as detection light; the reflected light beam split by the third HP rotation combining module is used as an upward cooling light, and the reflected light beam split by the fourth HP rotation combining module is used as a downward cooling light; the detection light, the upward cooling light and the downward cooling light respectively enter three cat eyes to pass through the acousto-optic modulation module for two times to control the frequency and the amplitude of laser, are combined through 1/4 wave plates and 1/2 wave plates and then respectively enter corresponding second optical fiber couplers, third optical fiber couplers and fourth optical fiber couplers to be coupled and enter polarization-maintaining optical fibers.

As shown in fig. 1 and 4, the cat eye double-pass acousto-optic modulation module includes a vertical acousto-optic modulator 401, a lens 402, a 1/4 wave plate 403 and a reflector 404, which are sequentially arranged, the 1/4 wave plate 403 is used to adjust the polarization direction of a light beam, a collimated light beam is frequency-shifted by the vertical acousto-optic modulator 401 to generate a deflected light beam, a zero-order light beam and a + 1-order light beam are focused by the lens 402 after transmitting the focal distance of the lens, the focal point is located on the mirror surface of the reflector 404, the reflected light returns as the original path, and the + 1-order light beam passing through the lens 402 and the vertical acousto-optic modulator 401 twice coincides with an incident light beam.

As shown in fig. 3, a vertical acousto-optic modulator 401 includes a vertical adapter 301 and an acousto-optic modulator 302, the vertical adapter 301 is fixedly connected with the acousto-optic modulator 302, the vertical adapter 301 is fixed on an optical plane through a rotating shaft, and the vertical adapter rotates around the rotating shaft. The vertical acousto-optic modulator is used for providing the mounting and adjusting functions of the acousto-optic modulator, and the center height of the light through hole of the mounted acousto-optic modulator is kept consistent with the light height of the light path device by adjusting the processing height of the vertically-arranged adapter. The HP rotating combination module and the vertical acousto-optic modulator 401 can achieve the above functions and shorten the optical path, wherein the center height of the light through hole of each component is kept consistent with the optical height of the optical path device by adjusting the processing height of the mounting adapter 201.

As shown in fig. 2, the HP rotation combination module includes an adapter 201, a rotation frame 202 for mounting 1/2 wave plate, a mounting table 203 for mounting PBS, and a rotation frame 204 for switching PBS mounting table, and is used for providing the polarization beam splitting function of collimated light beam and the adjusting function of the pitch and horizontal deflection of the PBS reflection direction. The rotating frame 202 for mounting the 1/2 wave plate and the rotating frame 204 for mounting the switching PBS is fixed on the adapter 201 through M4 screws, and is used for adjusting the processing height of the adapter 201, so that the center heights of the light-passing holes of the rotating frame 202 for mounting the 1/2 wave plate and the rotating frame 204 for mounting the switching PBS after mounting are kept consistent with the light height of the light path device by adjusting the processing height of the adapter. The PBS mounting table 203 is located between the 1/2 wave plate mounting rotary frame 202 and the PBS transfer mounting rotary frame 204, and the 1/2 wave plate mounting rotary frame 202 and the PBS transfer mounting rotary frame 204 are fixed to the adapter 201, and the PBS mounting table 203 is fixed.

Preferably, the optical path device is arranged horizontally and vertically according to a connecting line of centers of the standard optical flat fixing holes, and the optical path device is arranged in the shortest distance according to the optical path function.

In particular, the present invention provides a miniaturized primary laser beam path device for use in cold atom fountain clocks, wherein the miniaturized primary laser beam path device of the present invention is implemented on a standard 25mm pitch optical flat plate of 600mm x 225 mm. The whole light path is transversely, flatly and vertically distributed along the central connecting line of the fixing holes on the optical flat plate, and the light height is 27 mm. Because the light path layout is preset, the requirements on the adjusting range and the precision of the optical adjusting frame are reduced, a spring adjusting mechanism in the general optical adjusting frame is cancelled, and the requirements on the light path adjustment can be met only by rotating related devices. In FIG. 1, 101 to 104 are five-axis fiber couplers, 105 to 111 are HP rotating combined modules, 112 to 114 are vertically arranged acousto-optic modulators, 115 to 117 are lenses, 118 to 120 are 1/4 wave plates, 121 to-123 are reflectors, and 124 to 126 are 1/2 wave plate +1/4 wave plate combinations.

The frequency-stabilized main laser is transmitted to a miniaturized main laser light path device through a polarization maintaining optical fiber, is output in a collimated mode through a five-axis optical fiber coupler 101, and sequentially passes through a first HP rotation combined module 105, a second HP rotation combined module 106, a third HP rotation combined module 107 and a fourth HP rotation combined module 108. The first HP rotation combination module 105 is used for fixing the polarization direction of input light, and it is ensured that the splitting ratio of the second HP rotation combination module 106, the third HP rotation combination module 107 and the fourth HP rotation combination module 108 does not change with the polarization jitter of the incident optical fiber. The second HP rotation combination module 106, the third HP rotation combination module 107 and the fourth HP rotation combination module 108 sequentially reflect detection light, upward cooling light and downward cooling light required by the cold atom fountain clock.

After the probe light beam reflected by the second HP rotation combination module 106 passes through the HP rotation combination module 109, the 1/2 wave plate on the probe light beam is adjusted to enable the incident light beam to be totally reflected, then the incident light beam sequentially passes through the vertically arranged acousto-optic modulator 112, the lens 115 and the 1/4 wave plate 118 and is focused on the reflecting mirror 121 to be reflected, the reflected light beam returns to the HP rotation combination module 109 according to the original path, and then the 1/4 wave plate 118 is adjusted to enable the light beam which passes through the acousto-optic modulator twice to be totally transmitted. The transmitted light is coupled into the polarization maintaining optical fiber by the five-axis optical fiber coupler 102 or the second optical fiber coupler 102 after passing through the 1/2 wave plate and 1/4 wave plate combination 124, and is transmitted to a fountain clock physical system to be used as detection light.

The upward cooling light beam reflected by the third HP rotating and combining module 107 passes through the HP rotating and combining module 110, the 1/2 wave plate on the HP rotating and combining module is adjusted to enable the incident light beam to be totally reflected, then the incident light beam sequentially passes through the vertically arranged acousto-optic modulation 113, the lens 116 and the 1/4 wave plate 119 and is focused on the reflecting mirror 122 to be reflected, the reflected light beam returns to the HP rotating and combining module 110 according to the original path, and then the 1/4 wave plate 119 is adjusted to enable the light beam which passes through the acousto-optic modulator twice to be totally transmitted. The transmitted light is coupled into the polarization-maintaining optical fiber by the five-axis optical fiber coupler 103 or the third optical fiber coupler 103 after passing through the 1/2 wave plate +1/4 wave plate combination 125, and is transmitted to a fountain clock physical system to be used as upward cooling light.

After the downward cooling light beam reflected by the fourth HP rotating and combining module 108 passes through the HP rotating and combining module 111, the 1/2 wave plate on the HP rotating and combining module is adjusted to enable the incident light beam to be totally reflected, then the incident light beam sequentially passes through the vertically arranged acousto-optic modulation 114, the lens 117 and the 1/4 wave plate 120 and is focused on the reflector 123 to be reflected, the reflected light beam returns to the HP rotating and combining module 111 according to the original path, and then the 1/4 wave plate 120 is adjusted to enable the light beam which passes through the acousto-optic modulator twice to be totally transmitted. The transmitted light is 1/2 wave plate +1/4 wave plate combination 126, then is coupled into the polarization-maintaining optical fiber by the five-axis optical fiber coupler 104 or the fourth optical fiber coupler, and is transmitted to the fountain clock physical system to be used as downward cooling light.

The invention also provides an adjusting method of the miniaturized main laser light path device applied to the cold atom fountain clock, which comprises the following steps:

the method comprises the following steps: collimation and light height adjustment of primary laser light

Connecting a polarization maintaining optical fiber for outputting main laser to a first optical fiber coupler 101 to output a collimated light beam, adjusting the position of a collimating lens of the optical fiber coupler, and optimizing the collimation degree of the light beam;

adjusting XY direction knobs of the optical fiber couplers to ensure that light beams are parallel to the optical flat plate on the optical path light height plane and are distributed along the central connecting line of the optical flat plate fixing hole according to the optical path light height requirement;

step two: HP rotary modular regulation

The HP spin pack includes an adapter 201, a spin stand 202 to which 1/2 waveplates are mounted, a PBS mount 203 and a spin stand 204 to which PBS mount is attached. The light beam passes through 1/2 wave plate and PBS in turn, and the rotating frame 202 with 1/2 wave plate mounted thereon is rotated to achieve the splitting ratio in the transmission and reflection directions of the PBS. The rotary frame 204 of the switching PBS mounting table is rotated to realize the adjustment of the pitching direction of the PBS reflected light beam, and the rotary switching seat 201 realizes the adjustment of the horizontal direction of the PBS reflected light beam. Depending on the characteristics of the PBS, the direction of the transmitted beam is substantially unaffected when the direction of the reflected beam is adjusted over a range. Because the light path layout is determined before the light path is adjusted, the adjusting range of the adjusting mechanism of the whole light path does not need to be too large, and the feasibility and the reliability of adjusting the direction of the PBS reflected light beam by using the HP rotation combination module are ensured.

Collimated light beams sequentially pass through the four HP rotary combination modules 105-108 for light splitting. The first HP rotation combination module 105 adjusts most of the output light of the optical fiber into transmission output, and is used for fixing the polarization state of the laser emitted by the optical fiber and reducing the influence of the polarization jitter of the optical fiber on the polarization splitting ratio of the subsequent HP rotation combination. The reflected beam split by the second HP rotation combination 106 module is used as detection light; the reflected light beam split by the third HP rotation combining module 107 is used as upward cooling light, and the reflected light beam split by the fourth HP rotation combining module 108 is used as downward cooling light. All reflected light beams of the HP rotation combination are required to be transversely and vertically arranged along the central connecting line of the fixed holes of the optical flat plate on the fixed light height according to the requirement of the light path arrangement.

Step three: vertical acousto-optic modulator modulation

The vertically-arranged acousto-optic modulator 401 comprises an acousto-optic modulator 302 and a vertically-arranged adapter 301, the acousto-optic modulator 302 is fixedly connected with the vertically-arranged adapter 301, and the center position of a transducer of the acousto-optic modulator 302 is positioned through a positioning hole in the vertically-arranged adapter 301 and is fixed on the light height required by the light path layout;

collimated light beams enter the vertical acousto-optic modulator 401 from the horizontal direction, and optimization of the efficiency of the acousto-optic modulator 302 can be achieved by rotating the acousto-optic modulator 302 in the vertical direction and rotating the vertical adapter 301 in the horizontal direction.

Step four: adjustment of cat eye through acousto-optic modulation module twice

The detection light, the upward cooling light and the downward cooling light which are separated by the HP rotation combination module pass through the acousto-optic modulation module twice respectively through the corresponding cat eye to realize the frequency and amplitude control of the laser;

taking a probe beam as an example, the probe light split by the second HP rotation combining module 106 passes through an HP rotation combining module 109, then the reflected light horizontally enters a vertical acousto-optic modulator 112, and the split +1 level light (with a certain deflection angle relative to the horizontal direction, and the angle determined by the acousto-optic modulator driving frequency) passes through a lens 115 and then is focused on the mirror surface of a reflector 121. The cat-eye design requires that the distance from the center of the transducer of the acousto-optic modulator 302 to the center of the lens 115 and the distance from the center of the lens 115 to the mirror surface of the mirror 121 are both equal to the focal length of the lens, and the optimal distance between the lens 115 and the mirror 121 needs to be adjusted. The +1 level light reflected by the mirror 121 returns to the acousto-optic modulator 302 twice, and then returns to the HP rotation combination module 109 in coincidence with the incident light beam, and the 1/4 wave plate 118 disposed between the lens 115 and the mirror 121 is adjusted to allow the probe light after passing through the acousto-optic modulator 302 twice to be transmitted after passing through the HP rotation combination module 109.

The adjusting method of the two-time passing of the cat eye of the upward cooling light and the downward cooling light by the acousto-optic modulation module is the same as the adjusting method of the two-time passing of the cat eye of the detection light by the acousto-optic modulation module, as shown in fig. 1.

Step five: free space to polarization maintaining fiber coupling conditioning

After the cat eye passes through the acousto-optic modulation module twice, the free space beams of the detection light, the upward cooling light and the downward cooling light transmitted by the corresponding HP rotation combination module need to be coupled into the three corresponding polarization-maintaining optical fibers for transmission.

The coupling of each polarization maintaining fiber comprises a five-axis fiber coupler, an 1/2 wave plate and a 1/4 wave plate, the focal length, the pitching, the inclination and the XY directions of lenses of the fiber coupler are adjusted, the fiber coupling efficiency from a free space to the polarization maintaining fiber is realized, and the polarization extinction ratio of output light of the polarization maintaining fiber can be optimized by adjusting the 1/2 wave plate and the 1/4 wave plate.

It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explaining the principles of the invention and are not to be construed as limiting the invention. Therefore, any modification, equivalent replacement, improvement and the like made without departing from the spirit and scope of the present invention should be included in the protection scope of the present invention. Further, it is intended that the appended claims cover all such variations and modifications as fall within the scope and boundaries of the appended claims or the equivalents of such scope and boundaries.