All-fiber optical pumping small cesium clock optical path system

Abstract

The utility model discloses an all-fiber optical pumping small cesium clock optical path system, and belongs to the technical field of atomic frequency standards. Comprising an optical fiber laser, an optical fiber beam splitter, an optical fiber voltage-controlled attenuator, an optical fiber acousto-optic modulator, a first optical fiber beam expanding collimator, a second optical fiber beam expanding collimator and a cesium-beam tube, the optical fiber laser is connected with an input optical fiber interface of the optical fiber beam splitter through an optical fiber; a first output optical fiber interface of the optical fiber beam splitter is connected with an inlet of the optical fiber voltage-controlled attenuator through an optical fiber; an outlet of the optical fiber voltage-controlled attenuator is connected with the first optical fiber beam expanding collimator through an optical fiber; a second output optical fiber interface of the optical fiber beam splitter is connected with an inlet of the optical fiber acousto-optic modulator through an optical fiber; an outlet of the optical fiber acousto-optic modulator is connected with the second optical fiber beam expanding collimator through an optical fiber; according to the utility model, manual adjustment intervention is reduced, and the reliability of optical path production is improved.

Description

Technical Field

[0001] This utility model relates to the field of atomic frequency standard technology, specifically to an all-fiber optical pump small cesium clock optical path system. Background Technology

[0002] Cesium atomic clocks are among the most widely used atomic clocks in timekeeping systems, satellite positioning and navigation systems, high-speed communication systems, and military defense. Optically pumped miniature cesium clocks incorporate laser technology based on traditional magnetically separated miniature cesium clocks, resulting in advantages such as higher performance and longer expected lifespan. Currently, most optical path systems for optically pumped miniature cesium clocks are still based on spatial optical paths. However, with the widespread use of optically pumped miniature cesium clocks in various practical applications, the following problems have been identified:

[0003] 1) When the ambient temperature changes significantly, the installation and fixing position of the spatial optical path device deviates due to factors such as thermal expansion and contraction and mechanical stress release, which causes the control parameters of the optical path to change.

[0004] 2) For the same reason mentioned above, the light-matter interaction effect occurring in the light-pumped cesium clock is affected, causing a change in the atomic clock frequency;

[0005] 3) During the optical path assembly process, the spatial optical path requires fine manual adjustment; during the transportation of the atomic clock, the deformation of the spatial optical path system after severe vibration cannot be recovered, affecting the reliability of the optical pumped cesium clock product during production and sales.

[0006] Therefore, the optical path for optically pumping the small cesium clock needs to be improved to solve the above problems. Utility Model Content

[0007] The purpose of this invention is to provide an all-fiber optical pump cesium clock optical path system.

[0008] To solve the above-mentioned technical problems, this utility model provides an all-fiber optical pump small cesium clock optical path system, including a fiber laser, a fiber beam splitter, a fiber voltage-controlled attenuator, a fiber acousto-optic modulator, a first fiber beam expander collimator, a second fiber beam expander collimator, and a cesium bundle tube;

[0009] The fiber optic beam splitter is provided with an input fiber optic interface, a first output fiber optic interface, and a second output fiber optic interface.

[0010] The cesium bundle tube is provided with a pumping optical window and a detection optical window;

[0011] The fiber laser is connected to the input fiber interface of the fiber beam splitter via an optical fiber.

[0012] The first output fiber optic interface of the fiber optic beam splitter is connected to the laser inlet of the fiber optic acousto-optic modulator via an optical fiber.

[0013] The laser output of the fiber optic acousto-optic modulator is connected to the first fiber optic beam expander and collimator via an optical fiber.

[0014] The first fiber expander collimator is installed on the pump window of the cesium bundle tube;

[0015] The second output fiber optic interface of the fiber optic beam splitter is connected to the laser inlet of the fiber optic voltage-controlled attenuator via an optical fiber.

[0016] The laser output of the fiber optic voltage-controlled attenuator is connected to the second fiber optic beam expander and collimator via an optical fiber.

[0017] The second fiber beam expander collimator is mounted on the detection optical window.

[0018] Preferably, the first fiber expander collimator is fixed to the pump window of the cesium bundle tube by a collimator fixing and adjusting bracket;

[0019] The second fiber beam expander collimator is fixed to the detection window of the cesium beam tube by a collimator fixing and adjusting bracket.

[0020] Preferably, the collimator fixing and adjusting bracket includes an optical frame and a fixing bracket;

[0021] The optical frame has a frame mounting hole at its center, which faces the pump window or the detection window. The first fiber optic expander or the second fiber optic expander is fixedly installed in the frame mounting hole.

[0022] The number of fixed brackets is two;

[0023] The fixed bracket includes a connected base plate and a vertical plate;

[0024] The base plate has a long strip-shaped bracket fixing hole, and the cesium bundle tube has a fixing screw hole. The bolt passes through the bracket fixing hole and extends into the fixing screw hole, thereby fixing the base plate to the cesium bundle tube.

[0025] The vertical plates of the two fixed brackets are respectively fixedly connected to both sides of the optical frame.

[0026] Preferably, the power ratio of the first output fiber optic interface and the second output fiber optic interface of the fiber optic beam splitter is 1:1.

[0027] Preferably, the fiber optic voltage-controlled attenuator includes a voltage-controlled attenuation fiber input, a voltage-controlled attenuation fiber output, and a voltage-controlled input.

[0028] Preferably, the center frequency of the fiber optic acousto-optic modulator is 251MHz, and the fiber optic acousto-optic modulator includes an acousto-optic modulation fiber input, an acousto-optic modulation fiber output, and a radio frequency power input.

[0029] Preferably, the diameter of the spatial laser beam output by the first fiber expander collimator and the second fiber expander collimator is 8 mm.

[0030] Preferably, the fiber laser is an 852nm fiber laser.

[0031] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0032] 1. This utility model uses a single 852nm fiber laser as the core of the optical path. After the beam is split, one of the beams uses an optical fiber-based acousto-optic modulator as a frequency shifting unit, and the other beam passes through an optical fiber voltage-controlled attenuator, thereby obtaining two laser beams for pumping and detection.

[0033] 2. The entire optical path system of this utility model uses optical fiber as the laser link; compared with the spatial optical path, it eliminates the precision adjustment process of the optical path, improves the production efficiency of the optical pump cesium clock optical path; reduces manual adjustment intervention, and improves the reliability of optical path production;

[0034] 3. In this invention, the fiber laser enters the cesium beam tube after passing through the fiber beam expander and collimator. The collimator fixing and adjusting bracket can adjust the position of the output spatial laser of the fiber beam expander and collimator to achieve the best matching between the laser and the cesium atomic beam. Attached Figure Description

[0035] The specific embodiments of this utility model will be further described in detail below with reference to the accompanying drawings.

[0036] Figure 1 This is a schematic diagram illustrating the application of an all-fiber optical pumping cesium clock optical path system according to this utility model;

[0037] Figure 2 This is a schematic diagram of the collimator fixing and adjusting bracket;

[0038] In the picture:

[0039] 1-Fiber laser; 2-Fiber beam splitter; 3-Fiber voltage-controlled attenuator; 4-Fiber acousto-optic modulator; 5-First fiber beam expander and collimator; 6-Second fiber beam expander and collimator; 7-Cesium bundle tube; 71-Pump window; 72-Detection window; 8-Collimator fixing and adjusting bracket; 81-Optical frame; 82-Fixing bracket; 811-Frame clasp; 821-Base plate; 822-Vertical plate; 823-Bracket fixing hole. Detailed Implementation

[0040] Many specific details are set forth in the following description to provide a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0041] The terminology used in one or more embodiments of this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the one or more embodiments of this specification. The singular forms “a,” “described,” and “the” as used in one or more embodiments of this specification and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in one or more embodiments of this specification refers to and includes any or all possible combinations of one or more associated listed items.

[0042] It should be understood that although the terms first, second, etc., may be used to describe various information in one or more embodiments of this specification, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, first may also be referred to as second without departing from the scope of one or more embodiments of this specification, and similarly, second may also be referred to as first. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to a determination."

[0043] The present invention will now be described in further detail with reference to the accompanying drawings:

[0044] This invention proposes an all-fiber optical pump cesium clock optical path system to improve the reliability of the optical pump cesium clock optical path system and reduce the environmental sensitivity of the optical path, thereby improving the performance indicators of the optical pump cesium clock. Specifically, it includes:

[0045] 1. Using a single 852nm fiber laser 1 as the core of the optical path, after the beam is split, one of the beams uses a fiber acousto-optic modulator 4 (AOM) as the frequency shifting unit, and the other beam passes through a fiber voltage-controlled attenuator, thereby obtaining two laser beams for pumping and detection.

[0046] 2. The entire optical path system uses optical fibers as the laser link;

[0047] 3. The fiber laser enters the cesium beam tube 7 after passing through the fiber beam expander and collimator.

[0048] The technical solution of this utility model is as follows:

[0049] An all-fiber optical pump cesium clock optical path system includes an 852nm fiber laser 1, a fiber beam splitter 2, a fiber voltage-controlled attenuator 3, a fiber acousto-optic modulator 4, two fiber beam expanders and collimators and their fixing and adjustment brackets.

[0050] The 852nm fiber laser 1 uses a fiber-optic distributed feedback (DFB) semiconductor laser tube. Under the control of the driving circuit, it can directly output a beam of 852nm wavelength laser through the fiber and connect it to the input end of the fiber beam splitter 2.

[0051] The fiber optic beam splitter 2 includes one input fiber optic interface and two output fiber optic interfaces, which output the input laser in a power ratio of 1:1 from the two fibers respectively.

[0052] Furthermore, the two outputs of the fiber beam splitter 2 are used for laser pumping and laser detection, respectively. One output for laser pumping is connected to the input of the fiber voltage-controlled attenuator 3, and the other output for laser detection is connected to the input of the fiber acousto-optic modulator 4.

[0053] The fiber voltage-controlled attenuator 3 includes a voltage-controlled attenuation fiber input, a voltage-controlled attenuation fiber output, and a voltage-controlled input. The laser power of the fiber output is controlled by the voltage level of the voltage-controlled input. The output fiber is connected to the beam expander and collimator of the pump laser.

[0054] The fiber acousto-optic modulator 4 is a +1 stage frequency-shifting AOM with a center frequency of 251MHz, which can increase the input laser frequency by 251MHz and output it. It includes acousto-optic modulation fiber input, acousto-optic modulation fiber output, and radio frequency power input. The frequency and efficiency of the frequency shift are controlled by the frequency and power of the radio frequency input, respectively.

[0055] Furthermore, the output of the fiber optic acousto-optic modulator 4 is connected to the beam expander and collimator of the detection laser;

[0056] The fiber beam expander and collimator converts the input fiber laser into a spatial laser, and realizes the beam expansion and collimation of the laser. The output spatial laser spot diameter is about 8mm.

[0057] Furthermore, two fiber optic beam expanders and collimators are fixed at the pump laser window and detection laser window positions of the optically pumped cesium clock cesium beam tube 7, respectively. The designed fixed adjustment bracket can fine-tune the position and output angle of the collimator to adjust the interaction effect between the pump laser and the detection laser and the cesium atom beam. The collimator fixed adjustment bracket 8 consists of an optical frame 81 and two fixed brackets 82, such as... Figure 2As shown. The first fiber beam expander collimator 5 and the second fiber beam expander collimator 6 are mounted perpendicularly to the plane of the paper in the lens frame mounting hole 811. The optical lens frame 81 is connected to the fixing bracket 82 and fixed to the cesium beam tube 7. The fixing hole 823 of the bracket is slightly larger than the diameter of the bolt. After loosening the bolt, the position of the fixing bracket 82 can be adjusted, thereby adjusting the position of the optical lens frame 81. After adjustment, the bolt is tightened to achieve fine-tuning of the position. The collimator fixing and adjusting bracket 8 can adjust the position of the spatial laser output by the fiber beam expander collimator to achieve the best matching between the laser and the cesium atomic beam.

[0058] The aforementioned all-fiber optical pump cesium clock optical path system, except for the fiber optic expander collimator, is fixed on an independent optical plate. The devices are interconnected through optical fibers, with fiber optic fusion splicing as the main method and flange connection as a secondary method. The excess fiber length is fixed on the plate with silicone to prevent it from scattering.

[0059] This utility model has the following advantages:

[0060] (1) All optical fiber devices are used, which eliminates the precision adjustment process of the optical path compared to the spatial optical path, thus improving the production efficiency of the optical pump cesium clock optical path; it also reduces manual adjustment intervention and improves the reliability of the optical path production.

[0061] (2) Compared with spatial optical paths, fiber optic paths have higher vibration resistance, which reduces the risk of optical path problems during the handling and transportation of optical pumped cesium clocks and improves the reliability of atomic clocks during the sales and use process.

[0062] (3) Compared with spatial optical paths, fiber optical paths are less sensitive to mechanical deformation and stress release, which reduces the sensitivity of the optical pump cesium clock optical system to changes in ambient temperature and improves the long-term stability of the optical path, thereby improving the long-term frequency stability index of the optical pump cesium clock.

[0063] To better illustrate the technical effects of this utility model, the present utility model provides the following specific embodiments to explain the above technical process:

[0064] Example 1: An all-fiber optical pump small cesium clock optical path system, such as... Figure 1As shown, the upper part is the entire optical system, including a fiber laser 1, a beam splitter, a fiber voltage-controlled attenuator 3, a fiber acousto-optic modulator 4, a first fiber beam expander collimator 5, a second fiber beam expander collimator 6, two collimator fixing and adjustment brackets 8, and several optical fibers. The lower part is a simplified schematic diagram of the cesium beam tube 7 of the optically pumped cesium clock. For the optically pumped cesium clock to operate normally, two laser beams, one for pumping and one for detecting, need to be incident on two light-atom interaction regions of the cesium beam tube 7, respectively, where pumping and detection interactions between the laser and the cesium atom beams occur in the two regions. The first and second fiber beam expanders collimators 6 are fixed to the cesium beam tube 7 via the collimator fixing and adjustment brackets 8, and other optical system components are fixed to the optical system.

[0065] The fiber laser 1 is a DFB laser with a wavelength of 852nm, corresponding to the D2 line of cesium atom transition. After the laser is generated in the laser, it is output along the optical fiber and connected to the input end of the optical fiber beam splitter 2. The beam splitter has a 1:1 power distribution ratio, and the two outputs are connected to the optical fiber voltage-controlled attenuator 3 and the optical fiber acousto-optic modulator 4 through optical fibers, respectively.

[0066] One of the laser beams passes through the fiber optic acousto-optic modulator 4 and is transmitted through an optical fiber to the first fiber optic beam expander collimator 5. The first fiber optic beam expander collimator 5 is fixed at the pump window 71 of the cesium beam tube 7 by the collimator fixing and adjusting bracket 8. The pump laser beam, which is expanded to form a spatially collimated laser beam, enters the cesium beam tube 7 and undergoes optical pump interaction in the light-atom interaction region. The fiber optic voltage-controlled attenuator 3 has a voltage input port, and adjusting the voltage input here can adjust the power of the pump laser accordingly.

[0067] Another laser beam passes through the fiber voltage-controlled attenuator 3 and is transmitted through the fiber to the second fiber beam expander collimator 6. The second fiber beam expander collimator 6 is fixed at the detection window 72 of the cesium beam tube 7 by the collimator fixing and adjusting bracket 8. The detection laser beam, which is expanded to form a spatially collimated laser beam, enters the cesium beam tube 7 and undergoes photodetection interaction in the light-atom interaction region. The fiber acousto-optic modulator 4 has a radio frequency signal (RF) input port. Adjusting the power of the RF signal at this port can adjust the power of the detection laser beam accordingly.

[0068] The fiber laser 1 achieves laser frequency stabilization by using the beam fluorescence spectrum of the optically pumped cesium clock (authorized utility model patent: ZL201910644955.3, a laser frequency stabilization method and optical system for improving the performance of an optically pumped cesium beam atomic clock). Since the frequency of the RF input signal is fixed at 251MHz, the detection laser is the 4-5 transition line of the cesium atom D2 line, and the pump laser is the 44 transition line of the cesium atom D2 line.

[0069] The power of the pump laser and the detection laser is stabilized and servo-controlled by the fiber optic voltage-controlled attenuator 3 and the fiber optic acousto-optic modulator 4, respectively. The specific method is consistent with the laser power control method of the space optical path system.

[0070] The collimator fixing and adjusting bracket 8 consists of an optical frame 81 and two fixing brackets 82, such as Figure 2 As shown. The first fiber beam expander collimator 5 and the second fiber beam expander collimator 6 are mounted perpendicularly to the plane of the paper in the lens frame mounting hole 811. The optical lens frame 81 is connected to the fixing bracket 82 and fixed to the cesium beam tube 7. The fixing hole 823 of the bracket is slightly larger than the diameter of the bolt. After loosening the bolt, the position of the fixing bracket 82 can be adjusted, thereby adjusting the position of the optical lens frame 81. After adjustment, the bolt is tightened to achieve fine-tuning of the position. The collimator fixing and adjusting bracket 8 can adjust the position of the spatial laser output by the fiber beam expander collimator to achieve the best matching between the laser and the cesium atomic beam.

[0071] The above description is merely a specific embodiment of this utility model, but the protection scope of this utility model is not limited thereto. Any changes or substitutions within the technical scope disclosed in this utility model should be included within the protection scope of this utility model. Therefore, the protection scope of this utility model should be determined by the protection scope of the claims.

Claims

1. An all-fiber optically pumped cesium clock light path system, characterized by: It includes a fiber laser (1), a fiber beam splitter (2), a fiber voltage-controlled attenuator (3), a fiber acousto-optic modulator (4), a first fiber beam expander collimator (5), a second fiber beam expander collimator (6), and a cesium bundle tube (7); The fiber optic beam splitter (2) is provided with an input fiber optic interface, a first output fiber optic interface, and a second output fiber optic interface; The cesium bundle tube (7) is provided with a pumping optical window (71) and a detection optical window (72); The fiber laser (1) is connected to the input fiber interface of the fiber beam splitter (2) via an optical fiber; The first output fiber optic interface of the fiber optic beam splitter (2) is connected to the laser inlet of the fiber optic acousto-optic modulator (4) via an optical fiber. The laser output of the fiber optic acousto-optic modulator (4) is connected to the first fiber optic beam expander collimator (5) via an optical fiber. The first fiber beam expander collimator (5) is installed on the pump window (71) of the cesium bundle tube (7); The second output fiber optic interface of the fiber optic beam splitter (2) is connected to the laser inlet of the fiber optic voltage-controlled attenuator (3) via an optical fiber; The laser outlet of the fiber optic voltage-controlled attenuator (3) is connected to the second fiber optic beam expander collimator (6) via an optical fiber. The second fiber beam expander collimator (6) is installed on the detection window (72).

2. The all-fiber optical pump cesium clock optical path system according to claim 1, characterized in that: The first fiber beam expander collimator (5) is fixed on the pump window (71) of the cesium bundle tube (7) by a collimator fixing adjustment bracket (8); The second fiber beam expander collimator (6) is fixed on the detection window (72) of the cesium bundle tube (7) by the collimator fixing adjustment bracket (8).

3. The all-fiber optical pump cesium clock optical path system according to claim 2, characterized in that: The collimator fixing and adjusting bracket (8) includes an optical frame (81) and a fixing bracket (82); The optical frame (81) has a frame mounting hole (811) at its center, which is directly opposite the pumping window (71) or the detection window (72). The first fiber optic expander collimator (5) or the second fiber optic expander collimator (6) is fixedly installed in the frame mounting hole (811). The number of the fixed brackets (82) is two; The fixed bracket (82) includes a connected base plate (821) and a vertical plate (822); The base plate (821) has a long strip-shaped bracket fixing hole (823), and the cesium bundle tube (7) has a fixing screw hole. The bolt passes through the bracket fixing hole (823) and extends into the fixing screw hole, thereby fixing the base plate (821) to the cesium bundle tube (7). The vertical plates (822) of the two fixed brackets (82) are fixedly connected to the two sides of the optical frame (81).

4. The all-fiber optical pump cesium clock optical path system according to claim 1, characterized in that: The power ratio of the first output fiber optic interface and the second output fiber optic interface of the fiber optic beam splitter (2) is 1:

1.

5. The all-fiber optical pump cesium clock optical path system according to claim 1, characterized in that: The fiber voltage-controlled attenuator (3) includes a voltage-controlled attenuation fiber input, a voltage-controlled attenuation fiber output, and a voltage-controlled input.

6. The all-fiber optical pump cesium clock optical path system according to claim 1, characterized in that: The center frequency of the fiber optic acousto-optic modulator (4) is 251MHz. The fiber optic acousto-optic modulator (4) includes an acousto-optic modulation fiber input, an acousto-optic modulation fiber output, and a radio frequency power input.

7. The all-fiber optical pump cesium clock optical path system according to claim 1, characterized in that: The diameter of the spatial laser beam output by the first fiber beam expander collimator (5) and the second fiber beam expander collimator (6) is 8 mm.

8. The all-fiber optical pump cesium clock optical path system according to claim 1, characterized in that: The fiber laser (1) is an 852nm fiber laser.

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