Optical pumped cesium clock based on three action region structure
By adding a laser frequency stabilization interaction region to the optically pumped cesium clock and optimizing the laser frequency stabilization method, the problem of low signal-to-noise ratio in the traditional two-zone structure was solved, and the short-term frequency stability and signal-to-noise ratio were improved, thus enhancing the overall performance of the atomic clock.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- KUN SHAN LA MU QI GUANG DIAN KE JI YOU XIAN GONG SI
- Filing Date
- 2025-08-20
- Publication Date
- 2026-06-26
AI Technical Summary
Traditional two-zone optically pumped cesium clocks suffer from low laser frequency stabilization signal-to-noise ratio, which limits the improvement of the Ramsey signal-to-noise ratio and consequently affects the improvement of short-term frequency stability.
By adding a laser frequency stabilization interaction region before the optical pump interaction region, a three-region structure is formed, which optimizes the laser frequency stabilization method. The laser frequency noise is reduced by the laser frequency stabilization interaction region, and the signal-to-noise ratio of the Ramsey spectral line is improved.
It significantly improves the short-term frequency stability of optically pumped cesium clocks, enhances the signal-to-noise ratio, and improves the overall performance and reliability of atomic clocks.
Smart Images
Figure CN224417183U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of atomic clock technology, specifically to a small optical pump cesium clock based on a three-operation-region cesium bundle tube and its related technologies and applications. Background Technology
[0002] Atomic clocks, as high-precision timekeeping instruments, are widely used in many fields such as navigation, communication, and scientific research. Among them, small cesium clocks have attracted attention due to their high precision and stability.
[0003] Small cesium clocks can be divided into two modes: magnetically separated and optically pumped. Compared to magnetic separation technology, optical pumping technology significantly improves the utilization rate of cesium atoms. At the same time, optical pumping technology can more precisely control the atomic state, thereby improving the short-term frequency stability of small cesium clocks.
[0004] However, the available beam spectrum signal for laser frequency stabilization using optically pumped cesium clocks based on traditional two-zone structure cesium bundle tubes is relatively small, resulting in a low laser frequency stabilization signal-to-noise ratio. This limits further improvement of the Ramsey signal-to-noise ratio and is not conducive to further improvement of the short-term frequency stability of optically pumped cesium clocks. Utility Model Content
[0005] The purpose of this invention is to provide a small optical pump cesium clock based on a three-region cesium bundle tube. By adding a laser frequency stabilization interaction region before the optical pump interaction region, a three-region structure is formed, which improves the laser frequency stabilization method, reduces laser frequency noise, thereby improving the signal-to-noise ratio of the Ramsey spectral line and ultimately enhancing the short-term frequency stability of the small optical pump cesium clock.
[0006] To solve the above-mentioned technical problems, this utility model provides a small cesium clock with optical pump based on a three-operation-region structure, including a three-operation-region cesium bundle tube and a three-operation-region optical path;
[0007] The three-functional-region cesium beam tube includes, in sequence, a cesium furnace, a laser frequency stabilization interaction region, an optical pump interaction region, a microwave cavity, and an optical detection interaction region;
[0008] The three-function optical path includes a laser, an isolator, a first half-wave plate, a first polarizing beam splitter, a second half-wave plate, and a second polarizing beam splitter.
[0009] The laser generated by the laser is split into two paths after passing through an isolator, a first half-wave plate, and a first polarizing beam splitter in sequence.
[0010] One laser beam from the first polarizing beam splitter is input into the light detection interaction region after passing through the first beam expander, and the other laser beam is split into two after passing through the second half-wave plate and the second polarizing beam splitter.
[0011] One laser beam from the second polarizing beam splitter is input into the optical pump interaction region after passing through an acousto-optic modulator and a second beam expander, while the other laser beam is input into the laser frequency stabilization interaction region after passing through a third beam expander.
[0012] Preferably, the atomic beam intensity of the laser frequency stabilization interaction region is greater than that of the optical pump interaction region and the optical detection interaction region.
[0013] Preferably, the laser frequency stabilization interaction region adopts a 4-5 cyclic transition line;
[0014] The beam spectrum of the laser frequency stabilization interaction region is larger than that of the optical detection interaction region;
[0015] The signal-to-noise ratio of the laser frequency-stabilized interaction region is higher than that of the optical detection interaction region.
[0016] Preferably, the laser generated by the laser is locked to the |F=4>-|F'=5> transition line.
[0017] Preferably, the laser frequency of the acousto-optic modulator is at the |F=4>-|F'=4> transition line.
[0018] Preferably, the laser generated by the laser is an 825nm laser.
[0019] Preferably, the laser power of the optical detection interaction region and the optical pump interaction region is 2mW to 3mW, and the optical power of the frequency stabilization interaction region is set to 1mW to 3mW.
[0020] Preferably, the first beam expander, the second beam expander, and the third beam expander are all lens groups composed of concave lenses and convex lenses.
[0021] Compared with the prior art, the beneficial effects of this utility model are as follows:
[0022] 1. Improve short-term frequency stability: By increasing the frequency stabilization zone and optimizing the laser frequency stabilization method, the laser frequency noise is effectively reduced, thereby improving the signal-to-noise ratio of the Ramsey spectral line and significantly improving short-term frequency stability, which is superior to traditional two-zone beam tubes.
[0023] 2. Enhanced signal-to-noise ratio: The frequency stabilization region is close to the cesium furnace, resulting in a stronger cesium atomic beam and a higher beam spectrum signal-to-noise ratio, which is beneficial for improving the laser frequency stabilization effect and the overall performance of the atomic clock;
[0024] 3. Structural optimization: The three-zone bundle tube design is more reasonable, and the division of labor among the functional areas is clear, which improves the stability and reliability of the atomic clock;
[0025] 4. Wide range of potential applications: This technology can be applied to fields such as high-precision time and frequency measurement, satellite navigation, and communication systems, and has significant scientific research and application value. Attached Figure Description
[0026] The specific embodiments of this utility model will be further described in detail below with reference to the accompanying drawings.
[0027] Figure 1 This utility model relates to the design of a three-function cesium atom beam tube and the optical path structure design.
[0028] Figure 2 This is a schematic diagram of the energy levels of cesium atoms and the frequencies of the detection laser and pump laser;
[0029] Figure 3 This is a schematic diagram of a three-operation-region circuit module;
[0030] In the picture:
[0031] 1-Cesium furnace; 2-Laser frequency stabilization interaction region; 3-Optical pump interaction region; 4-Microwave cavity; 5-Optical detection interaction region; 6-Laser; 7-Isolator; 8-First half-wave plate; 9-First polarizing beam splitter; 10-Second half-wave plate; 11-Second polarizing beam splitter; 12-First beam expander; 13-Acousto-optic modulator; 14-Second beam expander; 15-Third beam expander. Detailed Implementation
[0032] 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.
[0033] 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.
[0034] 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."
[0035] The present invention will now be described in further detail with reference to the accompanying drawings:
[0036] This utility model provides an optical pump cesium clock based on a three-operation-region structure, including a three-operation-region cesium bundle tube, a three-operation-region optical path, and a three-operation-region circuit;
[0037] This utility model includes a three-function cesium bundle tube, which is used to realize the basic physical process of optical pumping of a small cesium clock. It mainly includes a cesium furnace 1 for generating cesium atomic flow, a laser frequency stabilization interaction region 2, an optical pumping interaction region 3, and an optical detection interaction region 5.
[0038] Furthermore, the cesium furnace 1, the optical pumping interaction region 3, and the optical detection interaction region 5 are the same as the cesium bundle tube of a conventional optical pumping cesium clock;
[0039] Furthermore, the laser frequency stabilization interaction region 2 is close to the cesium furnace 1, and its atomic beam intensity is greater than that of the optical pump interaction region 3 and the optical detection interaction region 5. Moreover, the 4-5 cyclic transition line used has a larger beam spectrum and a higher signal-to-noise ratio than the detection region. Using the frequency stabilization region for laser frequency stabilization can reduce laser noise and obtain a lower frequency stability.
[0040] This utility model includes a three-function optical path, which is used to generate the laser required for three-function optical pumping of a small cesium clock. It only requires a single 825nm laser beam generated by laser 6. Its optical path structure is simple, and the system has low complexity and high integration.
[0041] Furthermore, the laser generated by the DFB laser 6 is locked to the |F=4>-|F'=5> transition line, and first passes through an isolator 7 to prevent the laser from the subsequent stage from returning into the laser 6 and interfering with its operation;
[0042] Furthermore, the laser used for laser frequency stabilization in the three-action region optical path (laser frequency stabilization interaction region 2) originates from the second polarization beam splitter 11 in the optical pump region;
[0043] Furthermore, the laser used for frequency stabilization of the three-action region optical path laser needs to be expanded by a lens group (third beam expander 15) composed of concave and convex lenses to expand the region where cesium atoms and laser interact, ensuring that the cesium atom beam can fully transition.
[0044] Furthermore, the optical power used for laser frequency stabilization in the three-function region is 1mW to 3mW;
[0045] Furthermore, by increasing the light intensity, the 4-3 and 4-4 transition lines are brought to saturation; by reducing the amplification factor of the external photodetector, the signal strength of the 4-5 transition line is prevented from being too high, causing its peak value to exceed the detection threshold and resulting in a cancellation.
[0046] Furthermore, this utility model also includes a three-operation-region circuit, which includes a photodetector circuit module, a PID control circuit module, and a phase detection circuit module, etc. Figure 3 As shown;
[0047] The photodetector module collects fluorescence signals from the laser frequency stabilization interaction region 2, the optical pump interaction region 3, and the optical detection interaction region 5 and converts them into electrical signals.
[0048] After the electrical signal is processed by a bandpass filter and an amplifier, it is input into the phase detection circuit module. At the same time, two in-phase signals with the same frequency generated by the temperature-controlled crystal oscillator signal source are a reference signal and a modulation signal, respectively. The reference signal is processed by direct digital frequency synthesis technology and then input into the phase detection circuit module.
[0049] After the electrical signal and the reference signal are processed by the phase detection circuit module, the error signal is obtained.
[0050] After the error signal is controlled by the PID control circuit module, it is input into the adder. At the same time, another signal generated by the constant temperature crystal oscillator signal source is processed and used as a modulation signal, which is also input into the adder.
[0051] Finally, the adder output is used as a feedback signal to adjust laser 6.
[0052] Furthermore, the debugging of the photodetector circuit module mainly involves adjusting the error signal, PI feedback, and modulation signal.
[0053] Furthermore, the PID control circuit module is a commonly used feedback control algorithm; PID control consists of three parts: proportional part, integral part, and derivative part.
[0054] Furthermore, the phase detector circuit can obtain the differential signal of the atomic beam spectrum required for frequency stabilization;
[0055] The photodetector circuit module, PID control circuit module, phase detection circuit module, isothermal crystal oscillator signal source and adder used in this utility model are all existing modules, and the specific structure and working principle of the modules are not described in detail.
[0056] The technical solution adopted in this utility model includes:
[0057] 1. The rightmost end of the beam tube of the three-action region structured light-pumped cesium clock is the cesium furnace 1, which is used to generate a cesium atomic beam. The atomic beam flies from right to left, passing through three regions in sequence: the laser frequency stabilization interaction region 2, the light pump interaction region 3, and the light detection interaction region 5.
[0058] 2. The purpose of adding the laser frequency stabilization interaction region 2 is to improve the existing laser frequency stabilization method and reduce laser frequency noise;
[0059] 3. To address the changes in the cesium atom beam tube structure, the three-zone beam tube optical path first generates laser light from laser 6 (DFB), which then passes through isolator 7, first half-wave plate 8, and first polarizing beam splitter 9 (PBS) before being split into two paths. One path is used for the photodetector interaction region 5; the other path passes through second half-wave plate 10 and second polarizing beam splitter 11 (PBS) and is split into two paths again, one for the photopump interaction region 3 and the other for the three-zone structure laser frequency stabilization interaction region 2.
[0060] 4. The pump light uses an acousto-optic modulator 13 (AOM) to shift the frequency of the laser by about 251MHz to reach the |F=4>-|F'=4> transition line.
[0061] 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:
[0062] Example 1: A small cesium clock based on a three-operation-region structure using optical pumping, such as... Figure 1 As shown, the upper part is the cesium bundle tube structure of the three-function-region small cesium clock, which includes, from right to left, a cesium furnace 1, a laser frequency stabilization interaction region 2, an optical pump interaction region 3, and an optical detection interaction region 5.
[0063] When the temperature of cesium furnace 1 rises to 100°C and stabilizes, it is ejected through a collimator under steam pressure and passes sequentially through the three-action region laser frequency stabilization interaction region 2, optical pump interaction region 3 and optical detection interaction region 5. At this time, cesium atoms in the beam are uniformly distributed on each energy level of the ground state.
[0064] Traditional two-interaction-region cesium beam tubes use the beam spectrum of the photodetector interaction region 5 to stabilize the frequency of the laser 6. When the laser frequency deviates from the peak of the fluorescence spectrum, a corresponding error signal is generated to correct the laser frequency back to the peak of the fluorescence spectrum, thereby locking the laser frequency at the reference atomic transition frequency. The beam spectrum stabilization signal of the two-interaction-region cesium beam tube is relatively small and is subject to microwave modulation interference.
[0065] This invention improves upon existing cesium beam tubes by adding a laser frequency stabilization interaction region 2 before the optical pump interaction region 3 to lock the laser 6, forming a three-interaction region structure. This improves the laser frequency stabilization method, reduces laser frequency noise, and thus increases the signal-to-noise ratio of the Ramsey spectral line.
[0066] A schematic diagram of the linear transition energy levels of optically pumped cesium atoms is shown below. Figure 2 As shown, the cesium atom beam undergoes laser frequency stabilization through the frequency-stabilizing interaction region, and the laser frequency is locked on the 4-5 transition line of cesium atoms.
[0067] Cesium atoms then pass through the optical pump interaction region 3. The pump light is incident perpendicularly and resonates with the cesium atoms. The pump laser is locked on the 4-4 transition line, and the atoms are pumped to the ground state F=3. At this time, the cesium atoms in the beam are uniformly distributed on each magnetic level of the ground state F=3.
[0068] Then, the cesium atom beam enters the microwave cavity 4, and the cesium atoms in the F=3, mF=0 state are excited to the F=4, mF=0 state with a certain probability.
[0069] Next, the cesium atom beam enters the photodetector interaction region 5. The number of atoms excited to the ground state F=4 after passing through the microwave cavity 4 is detected by the detection light. Since the detection laser is locked on the 4-5 transition line, after the detection light excites the atoms to the excited state F'=5, due to the selection rule, the atoms can only fall back to the ground state F=4. Each atom is continuously excited to the excited state, returns to the ground state through spontaneous emission, and is excited again. The large number of fluorescent photon signals emitted in this process are converted into electrical signals by the photodetector and circuit, which are used for the control of the atomic clock system.
[0070] The part of this utility model concerning the optical path design of a three-function cesium beam tube is as follows: Figure 1 As shown, the laser generated by laser 6 first passes through isolator 7. After adjustment, isolator 7 achieves an isolation ratio of over 90% between the outgoing and incoming light, effectively isolating the laser from the subsequent stage from returning into laser 6 and interfering with the operation of laser 6.
[0071] Then, the laser beam is split into two beams by the first half-wave plate 8. One beam is used for the optical detection interaction region 5, and the other beam is coarsely adjusted by the second half-wave plate 10 and the second polarization beam splitter 11 before being split into two beams. One beam is used for the optical pump interaction region 3, and the other beam is used for the laser frequency stabilization interaction region 2.
[0072] The output frequency of the DFB laser 6 is locked to the 4-5 transition line of cesium atoms through the laser frequency stabilization interaction region 2. This frequency is also suitable for the photodetection interaction region 5. An AOM (Optical Optical Array) is used to shift the laser frequency by approximately 251 MHz, making the 4-4 transition line suitable for the photopump interaction region 3. After the laser beam undergoes angle adjustments by a series of large and small mirrors, it needs to be expanded by a lens group consisting of concave and convex lenses to increase the area where cesium atoms interact with the laser, ensuring sufficient transitions in the cesium atom beam. After beam expansion and control by an aperture, the actual spot size obtained before entering the optical window of the cesium beam tube is 0.8 cm. 2 Left and right; because the laser power passing through the optical window will decrease after multiple reflections and refractions, the laser power of the optical detection interaction region 5 and the optical pump interaction region 3 in this invention is set to 2mW to 3mW, while the optical power of the frequency stabilization interaction region is set to 1mW to 3mW.
[0073] The main feature of the above process is that the existing two-zone cesium beam tube is improved by adding a laser frequency stabilization zone before the optical pumping zone to lock the laser 6, forming a three-zone structure to improve the laser frequency stabilization method and thus improve short-term frequency stability.
[0074] Finally, it should be noted that the three-action region structure for improving the short-term frequency stability of optically pumped cesium clocks described in this utility model is not limited to cesium clocks. It can also be used in beam-type quantum precision measurement instruments such as rubidium beam atomic clocks and cold atom beam atomic clocks to effectively improve the short-term frequency stability.
[0075] 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. A small cesium clock based on a three-operation-region structure, characterized in that: Includes a three-function cesium beam tube and a three-function optical path; The three-function cesium beam tube includes a cesium furnace (1), a laser frequency stabilization interaction region (2), an optical pump interaction region (3), a microwave cavity (4), and an optical detection interaction region (5) arranged sequentially. The three-function optical path includes a laser (6), an isolator (7), a first half-wave plate (8), a first polarizing beam splitter (9), a second half-wave plate (10), and a second polarizing beam splitter (11); The laser generated by the laser (6) is split into two paths after passing through the isolator (7), the first half-wave plate (8) and the first polarizing beam splitter (9) in sequence; One laser beam from the first polarizing beam splitter (9) is input into the light detection interaction region (5) after passing through the first beam expander (12), and the other laser beam is split into two beams after passing through the second half-wave plate (10) and the second polarizing beam splitter (11). One laser beam from the second polarizing beam splitter (11) passes through the acousto-optic modulator (13) and the second beam expander (14) and is then input into the optical pump interaction region (3), while the other laser beam passes through the third beam expander (15) and is then input into the laser frequency stabilization interaction region (2).
2. The optically pumped cesium clock based on a three-operation-region structure according to claim 1, characterized in that: The atomic beam intensity of the laser frequency stabilization interaction region (2) is greater than that of the optical pump interaction region (3) and the optical detection interaction region (5).
3. The optically pumped cesium clock based on a three-operation-region structure according to claim 2, characterized in that: The laser frequency stabilization interaction region (2) adopts a 4-5 cyclic transition line; The beam spectrum of the laser frequency stabilization interaction region (2) is larger than that of the optical detection interaction region (5); The signal-to-noise ratio of the laser frequency stabilization interaction region (2) is higher than that of the optical detection interaction region (5).
4. The optically pumped cesium clock based on a three-operation-region structure according to claim 3, characterized in that: The laser generated by the laser (6) is locked to the transition line |F=4>-|F'=5>.
5. The optically pumped cesium clock based on a three-operation-region structure according to claim 4, characterized in that: The laser frequency of the acousto-optic modulator (13) is at the transition line |F=4>-|F'=4>.
6. The optically pumped cesium clock based on a three-operation-region structure according to claim 5, characterized in that: The laser (6) generates an 825nm laser.
7. The optically pumped cesium clock based on a three-operation-region structure according to claim 6, characterized in that: The laser power of the optical detection interaction region (5) and the optical pump interaction region (3) is 2mW to 3mW, and the optical power of the frequency stabilization interaction region is set to 1mW to 3mW.
8. The optically pumped cesium clock based on a three-operation-region structure according to claim 7, characterized in that: The first beam expander (12), the second beam expander (14) and the third beam expander (15) are all lens groups composed of concave lenses and convex lenses.