Multi-frequency laser light source system based on 12-pass acousto-optic frequency shifting technology

Abstract

The invention discloses a multi-frequency laser light source system based on 12-pass acousto-optic frequency shifting technology, and relates to the field of acousto-optic frequency shifting of lasers. The system mainly comprises: from left to right, the first polarization beam splitter prism, the Faraday rotator, the half-wave plate, the second polarization beam splitter prism, the first convex lens, the outer right-angle reflector with a central hole, the second convex lens, the acousto-optic modulator, the third convex lens, and the third polarization beam splitter prism are arranged and connected in sequence to form a main line; the single-mode polarization-maintaining optical fiber, the laser collimator and the first polarization beam splitter prism are connected in sequence; the first reflector and the second polarization beam splitter prism are connected; the fourth polarization beam splitter prism is placed on the lower left side of the first convex lens; and the radio frequency driving source and the acousto-optic modulator are connected. The invention realizes a huge leap in the comprehensive performance of acousto-optic modulation technology in frequency shift range, diffraction efficiency and damage threshold, laser utilization rate, etc. at a very low cost, has great application prospects, and will be conducive to promoting the development of cold atom physics experimental technology.

Description

Technical Field

[0001] The present invention relates to the field of laser acousto-optic frequency shifting, and in particular to a multi-frequency laser light source system based on 12-pass acousto-optic frequency shifting technology; specifically, the present invention relates to a 12-pass acousto-optic frequency shifting laser light source system which is used for laser cooling of atoms and can generate 0-12 times acousto-optic frequency shifting lasers, and each laser can be separated independently. Background Art

[0002] Laser cooling of atoms is a hot area in current atomic physics research. In the process of preparing cold atoms, lasers with multiple frequencies are often required. Taking alkali metal atoms as an example (such as lithium, sodium, potassium, rubidium, cesium and other atoms), the cooling and trapping of atoms requires the preparation of cooling and back-pumping lasers, and the frequency difference between these two lasers is often in the order of GHz (such as 804MHz for lithium-7 atoms, 1.772GHz for sodium-23 atoms, 1.286GHz for potassium-40 atoms, 3.036GHz for rubidium-85 atoms, 6.835GHz for rubidium-87 atoms, and 9.192GHz for cesium atoms). In recent years, with the development of atomic precision measurement, people have put forward higher and higher requirements for the long-term stability and reliability of the relatively mature atomic precision measurement systems, such as atomic clocks and atomic interferometers. Reference (Measurement of Local Gravity via a Cold Atom Interferometer, L. Zhou et al., Chin. Phys. Lett. Vol. 28, p. 013701, 2011). Take the test of the equivalence principle at 10 -8 Level by aDual-Species Double-Diffraction Raman Atom Interferometer, L. Zhou et al., Phys. Rev. Lett. 115, 013004 (2015)), the experiment needs to prepare 85 Rb and 87Rb two different component atoms, which requires 4 seed lasers of different frequencies, and amplification separately, in order to obtain the corresponding required laser. Traditionally, people often use four laser frequency locking schemes to achieve cooling and back pumping lasers respectively, and amplify them. Then, if any of these lasers is frequency unlocked, it means that the entire experimental system will be suspended. Therefore, the more frequency-locked seed lasers are used, the greater the risk factor. In addition, since laser frequency locking is easily affected by the environment and produces frequency drift, the more seed lasers there are, the greater the impact of various random drifts on the stability of the system. Therefore, in order to reduce such effects, it is often necessary to use better lasers and better laser frequency locking systems to improve environmental stability, which means that the system cost and technical difficulty will increase significantly; or, the solution of fiber phase modulator is adopted, but this must pay for the problems of low laser utilization efficiency, impure spectrum, and easy competition between sidebands; or the use of high-frequency acousto-optic modulators, which will face problems such as extremely low diffraction efficiency, low damage threshold, and high price. Therefore, the development of a method with precise frequency control, pure spectrum, high laser utilization efficiency, and economy is of great significance to the precision measurement of current atomic systems. Summary of the invention

[0003] The purpose of the present invention is to solve the problems in the current cold atom research field, such as poor stability, poor scalability, and high cost of independent lasers; low diffraction efficiency and damage threshold, high cost, etc. when using high modulation frequency acousto-optic modulators; low laser utilization efficiency, impure spectrum, and easy competition between sidebands when using electro-optic modulators. Provide a multi-frequency laser light source system based on 12-pass acousto-optic frequency shifting technology, which can realize the separate utilization of 13 frequency lasers in 0-12 passes with only one acousto-optic modulator, and the maximum frequency range can reach 5GHz, thereby realizing a method with precise laser frequency control, pure spectrum, high laser utilization efficiency, and economic feasibility.

[0004] The object of the present invention is achieved in that:

[0005] The system includes a single-mode polarization-maintaining optical fiber, a laser collimator 2, the first, second, third, and fourth polarization splitting prisms, a Faraday rotator, a half-wave plate, the first, second, and third convex lenses, an acousto-optic modulator 7, a radio frequency driving source, a quarter-wave plate, an external right-angle reflector, an external right-angle reflector with a central hole, and the first and second reflectors;

[0006] Its location and connectivity are:

[0007] From left to right, the first polarization beam splitter prism, the Faraday rotator, the half wave plate, the second polarization beam splitter prism, the first convex lens, the outer right-angle reflector with a central hole, the second convex lens, the acousto-optic modulator, the third convex lens, and the third polarization beam splitter prism are arranged and connected in sequence to form a main line;

[0008] The single-mode polarization-maintaining optical fiber, the laser collimator and the first polarization beam splitter prism are connected in sequence;

[0009] The second reflector is connected to the second polarization beam splitting prism;

[0010] The fourth polarization beam splitter prism is placed on the lower left side of the first convex lens;

[0011] The radio frequency driving source is connected to the acousto-optic modulator;

[0012] A quarter wave plate, an outer right-angle reflector and a first reflector are arranged on the upper right side of the third convex lens, which are connected in sequence;

[0013] The focal lengths of the 1st, 2nd and 3rd convex lenses are f1, f2 and f3 respectively; the 1st convex lens is located on the right side of the 2nd polarization splitter prism, and is f1+f2 away from the 2nd convex lens; the 3rd convex lens is located on the right side of the 2nd convex lens, and is f2+f3 away from the 3rd convex lens; the acousto-optic modulator 7 is located at the focal length on the right side of the 2nd convex lens, and is also located at the focal length on the left side of the 3rd convex lens; the external right-angle reflector is located slightly left of the focal length on the right side of the 3rd convex lens.

[0014] The present invention has the following advantages and positive effects:

[0015] ① Compared with the independent laser solution, the present invention has the advantages of simple technology, strong scalability and low cost; compared with the electro-optic modulator solution, the present invention has the advantages of high sideband isolation, high efficiency and safety after laser amplification; compared with the existing high-frequency acousto-optic modulator, the present invention has the advantages of high frequency modulation frequency range (center frequency 350MHz*12=4.2GHz, tuning range 3.4-5.0GHz, compared with the high-frequency acousto-optic modulator (LNF-3500-1000) frequency shift 3.5GHz, frequency shift efficiency (12 range>10%, compared with the acousto-optic modulator (LNF-3500-1000) The present invention has great improvements in the following aspects: the damage threshold (>300mW incident, compared with 30mW incident of the acousto-optic modulator (LNF-3500-1000)), the final output power (>30mW output, compared with 1.5mW output of the acousto-optic modulator (LNF-3500-1000)) and the cost; at the same time, the present invention can simultaneously obtain 13 levels of diffraction laser of 0-12 stages, which greatly simplifies the optoelectronic structure when obtaining multi-level lasers; it realizes a huge leap in the comprehensive performance of GHz-level acousto-optic modulation technology, which will effectively improve the application of acousto-optic modulation technology in the demand for GHz-level laser modulation.

[0016] ② In terms of technical design, the Faraday rotator + three-lens system + triangular prism + wave plate polarization beam splitting system designed by the present invention increases the current multi-pass acousto-optic frequency shifting technology from the original 6 passes to 12 passes, and the laser frequency shifting range is greatly increased compared with the past; and multiple diffractions are achieved with extremely high efficiency (12 pass efficiency>10%); in addition, the present invention is based on conventional low-cost acousto-optic modulators to achieve GHz-level large-range frequency shifting technology, which is conducive to the promotion and application of this technology;

[0017] ③ In terms of application, the present invention can achieve a frequency shift of positive or negative one level, so that the maximum frequency shift of more than ±5.0 GHz can be achieved with the seed laser as the core, which basically covers the current demand for GHz-level frequency shifting technology in the field of cold atom physics research. Since conventional devices can be used to achieve acousto-optic frequency shifting technology with very powerful comprehensive performance, the application of this technology in the field of cold atom research will be greatly improved.

[0018] In conclusion, the present invention achieves a huge leap in the comprehensive performance of acousto-optic modulation technology in terms of frequency shift range, diffraction efficiency and damage threshold, laser utilization, etc. at a very low cost. It has great application prospects and will be beneficial to promoting the development of cold atom physics experimental technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a top view of the working principle of this system;

[0020] Figure 2 yes Figure 1 Right half front view.

[0021] in:

[0022] 1—Single-mode polarization-maintaining fiber;

[0023] 2—Laser collimator;

[0024] 3-1, 3-2, 3-3, 3-4—1st, 2nd, 3rd, 4th polarization beam splitter prism

[0025] 4—Faraday rotator;

[0026] 5—half wave plate;

[0027] 6-1, 6-2, 6-3—1st, 2nd, 3rd convex lenses;

[0028] 7—Acousto-optic modulator;

[0029] 8—RF driving source;

[0030] 9—quarter wave plate;

[0031] 10-1—external right-angle reflector, 10-2—external right-angle reflector with center hole;

[0032] 11-1, 11-2—1st and 2nd reflecting mirrors. DETAILED DESCRIPTION

[0033] The following is a detailed description of the system with reference to the accompanying drawings and embodiments:

[0034] 1. Overall

[0035] like Figure 1 , Figure 2 The system includes a single-mode polarization-maintaining optical fiber 1, a laser collimator 2, the first, second, third, and fourth polarization splitting prisms 3-1, 3-2, 3-3, and 3-4, a Faraday rotator 4, a half-wave plate 5, the first, second, and third convex lenses 6-1, 6-2, and 6-3, an acousto-optic modulator 7, a radio frequency driving source 8, a quarter-wave plate 9, an external right-angle reflector 10-1, an external right-angle reflector with a central hole 10-2, and the first and second reflectors 11-1 and 11-2;

[0036] Its location and connectivity are:

[0037] From left to right, the first polarization beam splitter prism 3-1, the Faraday rotator 4, the half wave plate 5, the second polarization beam splitter prism 3-2, the first convex lens 6-1, the central hole outer right-angle reflector 10-2, the second convex lens 6-2, the acousto-optic modulator 7, the third convex lens 6-3, and the third polarization beam splitter prism 3-3 are arranged and connected in sequence to form a main line;

[0038] The single-mode polarization-maintaining optical fiber 1, the laser collimator 2 and the first polarization beam splitting prism 3-1 are connected in sequence;

[0039] The second reflector 11-2 is connected to the second polarization splitting prism 3-2;

[0040] The fourth polarization splitting prism 3-4 is placed on the lower left side of the first convex lens 6-1;

[0041] The radio frequency driving source 8 is connected to the acousto-optic modulator 7;

[0042] On the upper right side of the third convex lens 6-3, a quarter wave plate 9, an outer right-angle reflector 10-1 and a first reflector 11-1 are arranged in sequence;

[0043] The focal lengths of the first, second and third convex lenses 6-1, 6-2 and 6-3 are f1, f2 and f3 respectively; the first convex lens 6-1 is located on the right side of the second polarization splitter prism 3-2, and is f1+f2 away from the second convex lens 6-2; the third convex lens 6-3 is located on the right side of the second convex lens 6-2, and is f2+f3 away from the third convex lens 6-3; the acousto-optic modulator 7 is located at the right focal length of the second convex lens 6-2, and is also located at the left focal length of the third convex lens 6-3; the external right-angle reflector 10-1 is located slightly left of the right focal length of the third convex lens 6-3.

[0044] 2. Functional components

[0045] The functional components described below are all commonly used standard parts.

[0046] 01. Single-mode polarization-maintaining fiber 1

[0047] The single-mode polarization-maintaining optical fiber 1 is an optical fiber that transmits linearly polarized laser light.

[0048] 02. Laser collimator 2

[0049] The laser collimator 2 is a device that can couple laser light into an optical fiber or collimate the laser light emitted from the optical fiber into a parallel beam with a certain beam waist, and is composed of a flange for fixing the optical fiber and a focusing lens.

[0050] 03. 1st, 2nd, 3rd, 4th polarization beam splitting prisms 3-1, 3-2, 3-3, 3-4

[0051] It is a cube polarization spectrometer that can change the polarization of laser to reflect (S polarization) or transmit (P polarization) the laser.

[0052] 04. Faraday rotator 4

[0053] The Faraday rotator 4 is a device that changes the polarization of laser light through the magneto-optical rotation effect of light.

[0054] 05. Half wave plate 5

[0055] The half wave plate 5 is a device for adjusting the polarization direction of the laser line.

[0056] 06. 1st, 2nd, 3rd convex lenses 6-1, 6-2, 6-3

[0057] It is a lens that can converge lasers. The focal lengths are f1, f2, and f3 respectively. Different position combinations can be used to control the spot size and divergence of the laser.

[0058] 07. Acousto-optic modulator 7

[0059] The acousto-optic modulator 7 is a device used to modulate the frequency and amplitude of the laser, which can separate the ±1st order diffracted light from the zeroth order light by twice the Bragg angle and modulate most of the laser power to the diffraction order.

[0060] 08. RF drive source 8

[0061] The RF driving source 8 is a RF sinusoidal wave signal that can output a certain power and can perform frequency modulation (including frequency modulation, i.e., FM, and keyed frequency shift modulation, i.e., FSK) and amplitude modulation (AM) on the signal, which drives the acousto-optic modulator 7 to control the laser.

[0062] 09. Quarter wave plate 9

[0063] The quarter wave plate 9 is a device for adjusting the polarization of laser light. By passing through a quarter wave plate twice which forms a certain angle with the linear polarization, an outgoing polarized light opposite to the polarization of the incident laser light can be obtained.

[0064] 10. External right angle reflector 10-1, External right angle reflector with center hole 10-2

[0065] The outer right-angle reflector 10-1 and the outer right-angle reflector 10-2 with a central hole are both composed of two triangular prisms whose reflecting surfaces are at right angles to each other. After the incident laser passes through, it is reflected twice and can be emitted in a direction parallel to the incident direction and separated by a certain distance in space.

[0066] Compared with the inner and outer right-angle reflectors, the outer right-angle reflector 10 - 1 can better ensure the linear polarization of the laser and has smaller laser loss;

[0067] The center of the outer right-angle reflector 10-2 with a hole is provided with a light-through hole, which allows light to pass freely.

[0068] 11. 1st and 2nd reflecting mirrors 11-1 and 11-2

[0069] The first and second reflecting mirrors 11 - 1 and 11 - 2 are plane mirrors that reflect laser light.

[0070] 3. Optical path

[0071] Its optical path is:

[0072] ① The laser passes through the single-mode polarization-maintaining fiber 1, and is collimated by the laser collimator 2 to emit parallel light b and perpendicularly to the first polarization beam splitter prism 3-1. At this time, the laser polarization is the reflected polarization of the polarization beam splitter prism, that is, S polarization, and the reflected light c is perpendicular to the incident light and emitted to the right;

[0073] ② The reflected light is directed to the left light hole of the Faraday rotator 4 and emitted from the right light hole. The laser polarization is rotated 45 degrees at this time, directed to and passed through the half wave plate 5, and adjusted to the polarization transmitted by the polarization splitter prism, that is, P polarization, through the half wave plate 5, and directed to the second polarization splitter prism 3-2;

[0074] ③ The laser passes through the second polarization beam splitter prism 3-2 and shoots towards the telescope group composed of the first convex lens 6-1 and the second convex lens 6-2, and exits as parallel light. At the same time, it passes through the central small hole of the central hole outer right-angle reflector 10-2 located between the first convex lens 6-1 and the second convex lens 6-2, and shoots towards the acousto-optic modulator 7, where +1 or -1 order diffraction occurs. The diffraction angle of the +1 or -1 order diffraction light is 1 times the Bragg diffraction angle. At this time, the diffraction light is polarized in the P polarization direction, and it shoots towards and passes through the third convex lens 6-3. At this time, the laser is focused light. At the same time, the non-diffracted light, that is, the 0-order light, does not change its propagation direction, shoots towards and passes through the third convex lens 6-3, and shoots towards the third polarization beam splitter prism 3-3. The 0-order light is polarized in the P polarization direction and is marked as P0_middle, and it passes through and exits from the middle layer of the third polarization beam splitter prism 3-3.

[0075] ④ After the +1 or -1 order diffraction light passes through the third convex lens 6-3, it shoots towards the outer right-angle reflector 10-1. After being reflected twice, the reflected light is offset by a certain distance from the incident light in the vertical direction and returns along a direction parallel to the incident light. The reflected light passes through the third convex lens 6-3 again. Since the outer right-angle reflector 10-1 is located at a distance of one focal length from the third convex lens 6-3, the light beam passing through the third convex lens 6-3 again becomes parallel light again, but the propagation direction is converged to the left focal point of the third convex lens 6-3, that is, the central position of the acousto-optic modulator 7, and +1 or -1 order diffraction occurs for the second time. The diffraction light shoots towards and passes through the second convex lens 6-2, and is polarized in the P polarization direction. The non-diffracted light, that is, the first +1 or -1 order diffraction light, does not change its propagation direction, shoots towards and passes through the second convex lens 6-2, the first convex lens 6-1, and the fourth polarization beam splitter prism 3-4. At this time, the first +1 or -1 order diffraction light is polarized in the P polarization direction and is marked as P1_bottom, and it passes through the fourth polarization beam splitter prism 3-4 and exits from the lower layer of the fourth polarization beam splitter prism 3-4.

[0076] ⑤ After the second +1 or -1 order diffracted laser passes through the second convex lens 6-2, it shoots towards the central hole outer right-angle reflector 10-2. After being reflected twice, the reflected light is offset by a certain distance from the incident light and returns along a direction parallel to the incident light. It passes through the second convex lens 6-2 again. At this time, the laser is polarized in the P polarization direction, and the transmitted light shoots towards the acousto-optic modulator 7, where +1 or -1 order diffraction occurs for the third time. The non-diffracted light, that is, the second +1 or -1 order diffraction light, does not change its propagation direction, shoots towards and passes through the third convex lens 6-3. At this time, the laser is polarized in the P polarization direction and is marked as P2_bottom, and it shoots towards and passes through the third polarization beam splitter prism 3-3 and exits from the lower layer of the third polarization beam splitter prism 3-3.

[0077] ⑥ The 3rd +1st or -1st order diffracted light passes through the 3rd convex lens 6-3 and the quarter wave plate 9, is reflected by the first external reflector 11-1, returns and passes through the quarter wave plate 9, the 3rd convex lens 6-3, and the acousto-optic modulator 7, and the 4th +1st or -1st order diffraction occurs. After that, the laser light coincides with the previously diffracted laser light, but its polarization is S polarization; the propagation direction of the non-diffracted light, i.e. the 3rd +1st or -1st order diffracted light, remains unchanged, and is emitted toward and passes through the 2nd convex lens 6-2. At this time, its polarization is S polarization, and is emitted toward the 4th polarization beam splitter prism 3-4, and is reflected from its upper layer, marked as S3_up;

[0078] ⑦ After the fourth diffraction, the diffracted light passes through the second convex lens 6-2 and is directed to the right-angle reflector 10-2 with a central hole. After being reflected twice, the reflected light is staggered with the incident light by a certain distance and returns in a direction parallel to the incident light, and passes through the second convex lens 6-2 again. At this time, the laser polarization is S polarization, and the transmitted light is directed to the acousto-optic modulator 7. The fifth +1 or -1 diffraction occurs, and the propagation direction of the non-diffracted light, that is, the fourth +1 or -1 diffraction light, remains unchanged, and is directed to and passes through the third convex lens 6-3. At this time, the laser polarization is S polarization, and is directed to and passes through the third polarization splitter prism 3-3, and is emitted from the upper layer of the third polarization splitter prism 3-3, marked as S4_up;

[0079] ⑧ The +1st or -1st diffracted light of the 5th time passes through the 3rd convex lens 6-3 and is emitted to the outer right-angle reflector 10-1. After being reflected twice, the reflected light is staggered with the incident light by a certain distance and returns in a direction parallel to the incident light and passes through the 3rd convex lens 6-3 again. At this time, the laser polarization is S polarization, and the transmitted light is emitted to the acousto-optic modulator 7. The +1st or -1st diffraction occurs for the 6th time. The propagation direction of the non-diffracted light, i.e. the 5th +1st or -1st diffracted light, remains unchanged and is emitted to and passes through the 2nd convex lens 6-2. At this time, the laser polarization is S polarization, and is emitted to and passes through the 4th polarization beam splitter prism 3-4, and is emitted from the middle layer of the 3rd polarization beam splitter prism 3-3, which is marked as S5_middle;

[0080] ⑨ The 6th +1st or -1st diffraction light is polarized as S polarization, passes through the second convex lens 6-2, passes through the small hole in the middle of the right-angle reflector 10-2 with a central hole, and then passes through the first convex lens 6-1, and is emitted to the second polarization splitter prism 3-2. After being reflected by the second polarization splitter prism 3-2, it is emitted to the second reflector 11-2 and returns along the original path, with S polarization perpendicular to the incident polarization, and repeats steps ③ to ⑧ to obtain the 7th, 8th, 9th, 10th, 11th, and 12th +1st or -1st diffraction light. At the same time, the 6th, 7th, 8th, 9th, 10th, and 11th +1st diffraction light is emitted. The +1st or -1st order diffracted light is respectively reflected from the middle layer of the 3rd polarization beam splitter prism 3-3, reflected from the lower layer of the 4th polarization beam splitter prism 3-4, reflected from the lower layer of the 3rd polarization beam splitter prism 3-3, transmitted from the upper layer of the 4th polarization beam splitter prism 3-4, transmitted from the upper layer of the 3rd polarization beam splitter prism 3-3, and transmitted from the middle layer of the 4th polarization beam splitter prism 3-4, and the 6th, 7th, 8th, 9th, 10th, and 11th +1st or -1st order diffracted light are marked as S6_middle, S7_lower, S8_lower, P9_upper, P10_upper, and P11_middle, respectively;

[0081] ⑩ The +1st or -1st order diffraction light occurs for the twelfth time, and its polarization is P polarization. It passes through the second convex lens 6-2, passes through the small hole in the middle of the right-angle reflector 10-2 with a central hole, and then passes through the first convex lens 6-1, and is emitted to and passes through the second polarization beam splitter prism 3-2, the half wave plate 5, and the Faraday rotator 4, and is emitted to and passes through the first polarization beam splitter prism 3-1, marked as P12, thereby realizing the spatial separation of the 0-12 range diffraction laser.

[0082] 4. Working Principle

[0083] The working principle of the present invention is described in detail below.

[0084] The working principle of the present invention is that the laser goes back and forth in the acousto-optic modulator and diffracts. For reference, the literature (Double-pass acousto-optic modulator system, Donley, EA, etc., Review of Scientific Instruments, Vol. 6, p. 063112, 2005) can be used. The present invention utilizes the insensitivity to the vertical laser deflection angle during the acousto-optic modulation process, designs a three-lens system combined with a right-angle prism, and realizes the three-fold diffraction of the acousto-optic modulation system; through the combination of a wave plate and a polarization beam splitter, the number of diffractions is doubled to reach 6 times; finally, through a Faraday rotator, the number of diffractions is doubled again to reach 12 times. This is the method with the most diffraction times in the current multi-pass acousto-optic frequency shifting scheme, and it is also the method with the best frequency shifting range (up to 5GHz). Combined with the corresponding optical technology, its efficiency is still as high as more than 10% when the frequency shift is 4.2GHz, and the output laser power can reach more than 30mW.

[0085] In the present invention, the acousto-optic modulator 7 can diffract the laser with high efficiency under the action of the radio frequency driving source 8. The acousto-optic modulator 7 adopts a 350MHz acousto-optic modulator, and its first-order light single diffraction efficiency is >80%. The laser passes through the single-mode polarization-maintaining optical fiber 1, and is collimated by the laser collimator 2 to emit parallel light and perpendicularly to the first polarization beam splitter prism 3-1. At this time, the laser polarization is the polarization beam splitter prism reflection polarization (S polarization), and the reflected light is perpendicular to the incident light and emitted to the right; the reflected light is emitted to the left light hole of the Faraday rotator 4, and emitted from the right light hole. At this time, the laser polarization is rotated 45 degrees, and is emitted to and through the half-wave plate 5, and is adjusted to the polarization beam splitter prism transmission polarization (P polarization) through the half-wave plate 5, and is emitted to the second polarization beam splitter prism 3-2; the laser is emitted through the second polarization beam splitter prism 3-2 The telescope group is composed of the first convex lens 6-1 and the second convex lens 6-2, and emits parallel light, and at the same time passes through the central small hole of the central hole outer right-angle reflector 10-2 between the first convex lens 6-1 and the second convex lens 6-2, and is emitted to the acousto-optic modulator 7, and +1 or -1 order diffraction occurs. The diffraction angle of the +1 or -1 order diffraction light is 1 times the Bragg diffraction angle. At this time, the diffracted light is polarized as P polarization, and is emitted to and passes through the third convex lens 6-3. At this time, the laser is a focused light; at the same time, the propagation direction of the non-diffracted light, that is, the 0th order light, remains unchanged, and is emitted to and passes through the third convex lens 6-3, and is emitted to the third Polarization beam splitter 3-3, 0th order light polarization is P polarization, marked as P0_, which is emitted from the middle layer of the third polarization beam splitter prism 3-3; +1st order or -1st order diffracted light passes through the third convex lens 6-3, and then is emitted to the outer right-angle reflector 10-1. After being reflected twice, the reflected light is offset from the incident light in the vertical direction by a certain distance, and returns in a direction parallel to the incident light. The reflected light passes through the third convex lens 6-3 again. Since the outer right-angle reflector 10-1 is located at one focal length of the third convex lens 6-3, the light beam that passes through the third convex lens 6-3 again becomes parallel light, but the propagation The direction is converged to the left focus of the third convex lens 6-3, that is, the center position of the acousto-optic modulator 7, and the +1st or -1st order diffraction occurs for the second time. The diffracted light is emitted toward and passes through the second convex lens 6-2, and the polarization is P polarization. The propagation direction of the non-diffracted light (the first +1st or -1st order diffracted light) remains unchanged, and it is emitted toward and passes through the second convex lens 6-2, the first convex lens 6-1, and the fourth polarization splitter prism 3-4. At this time, the first +1st or -1st order diffracted light is polarized into P polarization, marked as P1_lower, and is emitted from the lower layer of the fourth polarization splitter prism (3-4) through the fourth polarization splitter prism 3-4;The second +1st or -1st order diffraction laser passes through the second convex lens 6-2 and then is emitted to the right-angle reflector 10-2 with a central hole. After being reflected twice, the reflected light is offset from the incident light by a certain distance and returns in a direction parallel to the incident light, and passes through the second convex lens 6-2 again. At this time, the laser polarization is P polarization, and the transmitted light is emitted to the acousto-optic modulator 7. The third +1st or -1st order diffraction occurs, and the propagation direction of the non-diffracted light, that is, the second +1st or -1st order diffraction light, remains unchanged, and is emitted to and passes through the third convex lens 6-3. At this time, the laser polarization is P polarization, marked as P2_, and is emitted to and passes through the third polarization splitter prism 3-3, and is emitted from the third polarization splitter prism The 3rd +1st or -1st diffracted light passes through the 3rd convex lens 6-3 and the quarter wave plate 9, is reflected by the first external reflector 11-1, returns and passes through the quarter wave plate 9, the 3rd convex lens 6-3, and the acousto-optic modulator 7, and the 4th +1st or -1st diffraction occurs. After that, the laser coincides with the previously diffracted laser, but its polarization is S polarization; the non-diffracted light, that is, the 3rd +1st or -1st diffracted light, has a constant propagation direction, is emitted toward and passes through the second convex lens 6-2, at which time its polarization is S polarization, is emitted toward the 4th polarization beam splitter prism 3-4, and is reflected from its upper layer, marked S3_up; the diffracted light after the 4th diffraction passes through After passing through the second convex lens 6-2, it is directed to the right-angle reflector 10-2 with a central hole. After being reflected twice, the reflected light is staggered with the incident light by a certain distance and returns in a direction parallel to the incident light, passing through the second convex lens 6-2 again. At this time, the laser polarization is S polarization, and the transmitted light is directed to the acousto-optic modulator 7. The +1st or -1st order diffraction occurs for the 5th time. The propagation direction of the non-diffracted light, that is, the 4th +1st or -1st order diffraction light, remains unchanged, and it is directed to and passes through the third convex lens 6-3. At this time, the laser polarization is S polarization, directed to and passes through the third polarization splitter prism 3-3, and is emitted from the upper layer of the third polarization splitter prism 3-3, marked as S4_up; the +1st order diffraction occurs for the 5th time. The 1st or -1st order diffracted light passes through the third convex lens 6-3 and is emitted to the outer right-angle reflector 10-1. After being reflected twice, the reflected light is staggered with the incident light by a certain distance and returns in a direction parallel to the incident light and passes through the third convex lens 6-3 again. At this time, the laser polarization is S polarization, and the transmitted light is emitted to the acousto-optic modulator 7. The +1st or -1st order diffraction occurs for the 6th time. The propagation direction of the non-diffracted light, i.e., the 5th +1st or -1st order diffracted light, remains unchanged and is emitted to and passes through the second convex lens 6-2. At this time, the laser polarization is S polarization and is emitted to and passes through the fourth polarization beam splitter prism 3-4 and is emitted from the middle layer of the third polarization beam splitter prism 3-3, which is marked as S5_middle.The 6th +1st or -1st diffraction light occurs, and its polarization is S polarization. It passes through the second convex lens 6-2, passes through the middle small hole of the central hole outer right-angle reflector 10-2, and then passes through the first convex lens 6-1, and is emitted to the second polarization splitter prism 3-2. After being reflected by it, it is emitted to the second reflector 11-2, and returns along the original path, with S polarization perpendicular to the incident polarization, repeating the previous steps ③ to ⑧ to obtain the 7th, 8th, 9th, 10th, 11th, and 12th +1st or -1st diffraction light. At the same time, the 6th, 7th, 8th, 9th, 10th, and 11th +1st or -1st diffraction light are reflected from the middle layer of the 3rd polarization splitter prism 3-3, the lower layer of the 4th polarization splitter prism 3-4, and the lower layer of the 4th polarization splitter prism 3-5, respectively. 4 is transmitted from the upper layer, the third polarization beam splitter prism 3-3 is transmitted from the upper layer, the fourth polarization beam splitter prism 3-4 is transmitted from the middle layer, the 6th, 7th, 8th, 9th, 10th, 11th +1st (or -1st) diffracted light is marked as S6_middle, S7_lower, S8_lower, P9_upper, P10_upper, P11_middle respectively; the 12th +1st or -1st diffracted light is polarized as P polarization, passes through the second convex lens 6-2, passes through the middle small hole of the central hole outer right-angle reflector 10-2, and then passes through the first convex lens 6-1, and is emitted to and passes through the second polarization beam splitter prism 3-2, the half wave plate 5, and the Faraday rotator 4, and is emitted to and passes through the first polarization beam splitter prism 3-1, marked as P12, so as to realize the spatial separation of the 0-12 diffracted laser.;

[0086] In summary, the present invention overcomes the shortcomings of the current cold atom research field of multiple laser solutions, electro-optic modulator solutions, high-frequency acousto-optic modulator solutions, etc., and realizes a multi-pass acousto-optic frequency shifting solution with high diffraction efficiency, large frequency shift range, high operating threshold, high comprehensive utilization efficiency and low cost, achieving a huge leap in the application of acousto-optic modulation technology.

Claims

1. A multi-frequency laser light source system based on 12-pass acousto-optic frequency shifting technology, characterized in that: It comprises a single-mode polarization-maintaining optical fiber (1), a laser collimator (2), first, second, third and fourth polarization splitting prisms (3-1, 3-2, 3-3 and 3-4), a Faraday rotator (4), a half-wave plate (5), first, second and third convex lenses (6-1, 6-2 and 6-3), an acousto-optic modulator (7), a radio frequency driving source (8), a quarter-wave plate (9), an outer right-angle reflector (10-1), an outer right-angle reflector with a central hole (10-2), and first and second reflectors (11-1 and 11-2). Its location and connectivity are: From left to right, the first polarization beam splitter prism (3-1), the Faraday rotator (4), the half wave plate (5), the second polarization beam splitter prism (3-2), the first convex lens (6-1), the central hole outer right-angle reflector (10-2), the second convex lens (6-2), the acousto-optic modulator (7), the third convex lens (6-3), and the third polarization beam splitter prism (3-3) are arranged and connected in sequence to form a main line; The single-mode polarization-maintaining optical fiber (1), the laser collimator (2) and the first polarization beam splitting prism (3-1) are connected in sequence; The second reflector (11-2) is connected to the second polarization splitting prism (3-2); The fourth polarization beam splitting prism (3-4) is placed on the lower left side of the first convex lens (6-1); The radio frequency driving source (8) is connected to the acousto-optic modulator (7); On the upper right side of the third convex lens (6-3), a quarter wave plate 9, an outer right-angle reflector 10-1 and a first reflector 11-1 are arranged in sequence; The focal lengths of the first, second and third convex lenses (6-1, 6-2, 6-3) are f1, f2 and f3 respectively; The first convex lens (6-1) is located on the right side of the second polarization splitter prism (3-2) and is at a distance f1+f2 from the second convex lens (6-2); the third convex lens (6-3) is located on the right side of the second convex lens (6-2) and is at a distance f2+f3 from the third convex lens (6-3); the acousto-optic modulator (7) is located at the right focal length of the second convex lens (6-2) and is also located at the left focal length of the third convex lens (6-3); the outer right-angle reflector (10-1) is located slightly left of the right focal length of the third convex lens (6-3).

2. The multi-frequency laser light source system according to claim 1, characterized in that Its optical path is: ① The laser passes through the single-mode polarization-maintaining optical fiber (1), is collimated by the laser collimator (2), and then emits parallel light b and is perpendicularly emitted to the first polarization beam splitter prism (3-1). At this time, the laser polarization is the reflected polarization of the polarization beam splitter prism, that is, S polarization, and the reflected light c is perpendicular to the incident light and emitted to the right; ② The reflected light is directed to the left light hole of the Faraday rotator (4) and is emitted from the right light hole. The laser polarization is rotated 45 degrees at this time, directed to and passes through the half wave plate (5), and is adjusted to the polarization transmitted by the polarization splitter prism, i.e., P polarization, through the half wave plate (5), and directed to the second polarization splitter prism (3-2); ③The laser passes through the second polarization beam splitter prism (3-2) and shoots towards the telescope group composed of the first convex lens (6-1) and the second convex lens (6-2), and exits as parallel light. At the same time, it passes through the central small hole of the external right-angle reflector with a central hole (10-2) located between the first convex lens (6-1) and the second convex lens (6-2), and shoots towards the acousto-optic modulator (7), where +1st order or -1st order diffraction occurs. The diffraction angle of the +1st order or -1st order diffracted light is 1 times the Bragg diffraction angle. At this time, the diffracted light is polarized in the P polarization direction, shoots towards and passes through the third convex lens (6-3), and at this time the laser is focused light; at the same time, the non-diffracted light, that is, the 0th order light, does not change its propagation direction, shoots towards and passes through the third convex lens (6-3), shoots towards the third polarization beam splitter prism (3-3). The 0th order light is polarized in the P polarization direction and is marked as P0_middle, and it passes through and exits from the middle layer of the third polarization beam splitter prism (3-3); ④After the +1st order or -1st order diffracted light passes through the third convex lens (6-3), it shoots towards the external right-angle reflector (10-1). After being reflected twice, the reflected light is offset by a certain distance from the incident light in the vertical direction and returns along a direction parallel to the incident light. The reflected light passes through the third convex lens (6-3) again. Since the external right-angle reflector (10-1) is located at a distance of one focal length from the third convex lens (6-3), the light beam passing through the third convex lens (6-3) again becomes parallel light, but the propagation direction is converged to the left focal point of the third convex lens (6-3), that is, the central position of the acousto-optic modulator (7), and +1st order or -1st order diffraction occurs for the second time. The diffracted light shoots towards and passes through the second convex lens (6-2), and is polarized in the P polarization direction. The non-diffracted light, that is, the +1st order or -1st order diffracted light from the first time, does not change its propagation direction, shoots towards and passes through the second convex lens (6-2), the first convex lens (6-1), and the fourth polarization beam splitter prism (3-4). At this time, the +1st order or -1st order diffracted light from the first time is polarized in the P polarization direction and is marked as P1_bottom, passes through the fourth polarization beam splitter prism (3-4) and exits from the lower layer of the fourth polarization beam splitter prism (3-4); ⑤After the second +1st order or -1st order diffracted laser passes through the second convex lens (6-2), it shoots towards the external right-angle reflector with a central hole (10-2). After being reflected twice, the reflected light is offset by a certain distance from the incident light and returns along a direction parallel to the incident light. It passes through the second convex lens (6-2) again. At this time, the laser is polarized in the P polarization direction, and the transmitted light shoots towards the acousto-optic modulator (7), where +1st order or -1st order diffraction occurs for the third time. The non-diffracted light, that is, the +1st order or -1st order diffracted light from the second time, does not change its propagation direction, shoots towards and passes through the third convex lens (6-3). At this time, the laser is polarized in the P polarization direction and is marked as P2_bottom, shoots towards and passes through the third polarization beam splitter prism (3-3), and exits from the lower layer of the third polarization beam splitter prism (3-3); ⑥ The 3rd +1st or -1st order diffracted light passes through the 3rd convex lens (6-3) and the quarter wave plate (9), is reflected by the first external reflector (11-1), returns and passes through the quarter wave plate (9), the 3rd convex lens (6-3), and the acousto-optic modulator (7), and undergoes the 4th +1st or -1st order diffraction. After that, the laser light coincides with the previously diffracted laser light, but its polarization is S polarization; the propagation direction of the non-diffracted light, i.e., the 3rd +1st or -1st order diffracted light, remains unchanged, and is emitted toward and passes through the 2nd convex lens (6-2). At this time, its polarization is S polarization, and is emitted toward the 4th polarization beam splitter prism (3-4), and is reflected from its upper layer, marked as S3_up; ⑦ After the fourth diffraction, the diffracted light passes through the second convex lens (6-2) and is directed to the right-angle reflector (10-2) with a central hole. After being reflected twice, the reflected light is offset from the incident light by a certain distance and returns in a direction parallel to the incident light, and passes through the second convex lens (6-2) again. At this time, the laser polarization is S polarization, and the transmitted light is directed to the acousto-optic modulator (7). The fifth +1 or -1 diffraction occurs, and the propagation direction of the non-diffracted light, that is, the fourth +1 or -1 diffraction light, remains unchanged, and is directed to and passes through the third convex lens (6-3). At this time, the laser polarization is S polarization, and is directed to and passes through the third polarization splitter prism (3-3), and is emitted from the upper layer of the third polarization splitter prism (3-3), marked as S4_up; ⑧ The +1st or -1st order diffraction light of the 5th time passes through the 3rd convex lens (6-3) and is emitted to the outer right-angle reflector (10-1). After being reflected twice, the reflected light is offset from the incident light by a certain distance and returns in a direction parallel to the incident light and passes through the 3rd convex lens (6-3) again. At this time, the laser polarization is S polarization, and the transmitted light is emitted to the acousto-optic modulator (7). The +1st or -1st order diffraction occurs for the 6th time. The propagation direction of the non-diffracted light, i.e. the 5th +1st or -1st order diffraction light, remains unchanged and is emitted to and passes through the 2nd convex lens (6-2). At this time, the laser polarization is S polarization, and is emitted to and passes through the 4th polarization beam splitter prism (3-4), and is emitted from the middle layer of the 3rd polarization beam splitter prism (3-3), which is marked as S5_middle; ⑨ The sixth +1st or -1st order diffraction light is polarized as S polarization, passes through the second convex lens (6-2), passes through the small hole in the middle of the right-angle reflector (10-2) with a central hole, and then passes through the first convex lens (6-1), and is emitted to the second polarization splitter prism (3-2). After being reflected by the second polarization splitter prism, it is emitted to the second reflector (11-2), and returns along the original path, with S polarization perpendicular to the incident polarization, and repeats steps ③ to ⑧ to obtain the 7th, 8th, 9th, 10th, 11th, and 12th +1st or -1st order diffraction light. At the same time, the 6th, 7th, 8th, 9th, 10th, and 11th +1st order diffraction light is generated. or -1st order diffracted light is respectively reflected from the middle layer of the third polarization beam splitter prism (3-3), reflected from the lower layer of the fourth polarization beam splitter prism (3-4), reflected from the lower layer of the third polarization beam splitter prism (3-3), transmitted from the upper layer of the fourth polarization beam splitter prism (3-4), transmitted from the upper layer of the third polarization beam splitter prism (3-3), and transmitted from the middle layer of the fourth polarization beam splitter prism (3-4); the 6th, 7th, 8th, 9th, 10th, and 11th +1st or -1st order diffracted light are respectively marked as S6_middle, S7_lower, S8_lower, P9_upper, P10_upper, and P11_middle; ⑩ The +1st or -1st order diffraction light occurs for the 12th time, and its polarization is P polarization. It passes through the second convex lens 6-2, passes through the small hole in the middle of the right-angle reflector (10-2) with a central hole, and then passes through the first convex lens (6-1), and is emitted to and passes through the second polarization beam splitter prism (3-2), the half wave plate (5), and the Faraday rotator (4), and is emitted to and passes through the first polarization beam splitter prism (3-1), marked as P12, thereby realizing the spatial separation of the 0-12 range diffraction laser.

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