An atomic beam clock based on fluorescence differential detection
The fluorescence differential detection technology eliminates stray light noise in the atomic beam clock, improves the signal-to-noise ratio, solves the frequency stability problem caused by high light noise under direct detection, and achieves higher atomic beam clock performance.
Patent Information
- Application Number
- CN202211478969.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2022-11-24
- Publication Date
- 2024-12-10
- Estimated Expiration
- 2042-11-24
AI Technical Summary
The direct detection method often encounters high light noise in atomic beam clocks, resulting in low signal-to-noise ratio of the clock signal, limiting the frequency stability performance of the atomic beam clock.
Using fluorescence differential detection technology, the differential operation module performs differential operation of the signals collected by the detection light and reference light, eliminates stray light noise, extracts pure clock transition fluorescence signals, and uses servo modules and voltage-controlled crystal oscillators to realize the atomic clock. Closed loop lock.
It effectively reduces stray light noise, improves the signal-to-noise ratio of clock transition signals, and improves the frequency stability performance of atomic beam clock.
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Figure CN115685722B_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of atomic clocks, and in particular relates to an atomic beam clock based on fluorescence differential detection. Background Art
[0002] Atomic beam clocks have excellent frequency accuracy and frequency stability performance, and are currently one of the most important and most widely used timekeeping atomic clocks. As the latest research achievement of atomic beam clocks, atomic beam clocks based on optical technology have the advantages of simple process and high theoretical indicators, and have attracted widespread attention from peers at home and abroad. One of the most important factors limiting the performance improvement of such atomic clocks comes from optical noise; in the past, people often used direct detection to extract clock signals, which resulted in large optical noise and low clock signal-to-noise ratio. Summary of the invention
[0003] The purpose of the present invention is to provide an atomic beam clock based on fluorescence differential detection to solve the problems of large optical noise and low signal-to-noise ratio of clock signals often encountered in direct detection methods.
[0004] To achieve the above object, the present invention provides the following solutions:
[0005] An atomic beam clock based on fluorescence differential detection, comprising: a beam source generating device, a Ramsey cavity for providing a microwave field required for the atomic beam clock transition, a differential detection device for detecting the clock transition signal, a laser, a spectroscope, a servo module, a voltage-controlled crystal oscillator and a microwave signal source;
[0006] The differential detection device comprises a first light collecting device, a second light collecting device and a differential operation module; the differential operation module is used to perform a differential operation on a first signal collected by the first light collecting device and a second signal collected by the second light collecting device;
[0007] The laser generates a beam of detection light and a beam of reference light through the beam splitter;
[0008] The beam source generating device, the Ramsey cavity and the first light collecting device are arranged in a vacuum chamber; the beam source generating device generates an atomic beam, and after an atomic state purification process, the atomic beam in a single clock state enters the Ramsey cavity and is excited by a resonant microwave field to undergo a clock transition in the Ramsey cavity;
[0009] The detection light passes through the first light collecting device to induce the atoms that have completed the clock transition to emit fluorescence; the first light collecting device is used to collect the clock transition fluorescence signal and the first stray light signal generated during the light detection process, and the clock transition fluorescence signal and the first stray light signal are used as the first signal and input into the differential operation module; the reference light passes through the second light collecting device in the same way as the detection light passes through the first light collecting device, and the reference light does not interact with the atoms; the second light collecting device is used to collect the second stray light signal generated by the reference light, and the second stray light signal is used as the second signal and input into the differential operation module; the differential operation module is used to perform differential operation on the first signal and the second signal, and output a clock transition fluorescence signal that eliminates the stray light background; the clock transition fluorescence signal is fed into the servo module, and is processed by the voltage-controlled crystal oscillator and the microwave signal source, so that the microwave field frequency output by the microwave signal source is stabilized at the clock transition frequency of the atom, thereby completing the closed-loop locking of the atomic clock.
[0010] Optionally, the atomic state purification process is achieved by a magnetic selection method and an optical pumping method.
[0011] Optionally, the atomic state purification process is achieved by a magnetic selection method or an optical pumping method.
[0012] Optionally, the power of the detection light is the same as the power of the reference light, and the spot of the detection light is the same as the spot of the reference light.
[0013] Optionally, the first light collecting device is the same as the second light collecting device.
[0014] Optionally, the second light collecting device is arranged in the vacuum chamber, or outside the vacuum chamber.
[0015] When the second light collecting device is located in the vacuum chamber, the frequency of the reference light is a non-atomic resonance frequency;
[0016] When the second light collecting device is located outside the vacuum chamber, the frequency of the reference light is an atomic resonance frequency, or the frequency of the reference light is a non-atomic resonance frequency.
[0017] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: the present invention provides an atomic beam clock based on fluorescence differential detection, and uses optical differential detection technology to extract clock transition signals of the atomic beam clock. Differential detection can effectively reduce stray light noise and improve the signal-to-noise ratio of the clock transition signal, which is beneficial to improving the frequency stability performance of the beam-type atomic clock. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0019] Figure 1 This is a schematic diagram of the principle structure of the atomic beam clock based on fluorescence differential detection provided by the present invention;
[0020] Figure 2 This is a structural diagram of a specific embodiment of the first atomic beam clock based on fluorescence differential detection provided by the present invention;
[0021] Figure 3 This is a structural diagram of a specific embodiment of the second atomic beam clock based on fluorescence differential detection provided by the present invention. DETAILED DESCRIPTION
[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0023] The purpose of the present invention is to provide an atomic beam clock based on fluorescence differential detection, which can effectively reduce stray light noise and improve the signal-to-noise ratio of clock transition signals.
[0024] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.
[0025] Figure 1 The schematic diagram of the atomic beam clock based on fluorescence differential detection provided by the present invention is as follows: Figure 1 An atomic beam clock based on fluorescence differential detection comprises: a beam source generating device 1, a Ramsey cavity 3 for providing a microwave field required for the transition of an atomic beam clock, a differential detection device for detecting the clock transition signal, a laser 4, a spectroscope 5, a servo module 9, a voltage-controlled crystal oscillator 10 and a microwave signal source 11.
[0026] The differential detection device includes a first light collecting device 6 , a second light collecting device 7 and a differential operation module 8 ; the differential operation module 8 is used to perform a differential operation on a first signal collected by the first light collecting device 6 and a second signal collected by the second light collecting device 7 .
[0027] The laser 4 generates a probe light 50 and a reference light 51 through the spectroscope. The power of the probe light 50 is the same as that of the reference light 51 , and the spot size of the probe light 50 is the same as that of the reference light 51 .
[0028] The beam source generating device 1, the Ramsey cavity 3 and the first light collecting device 6 are arranged in a vacuum chamber 13; the beam source generating device 1 generates an atomic beam 12, and after an atomic state purification process 2, the single clock-state atomic beam 12 enters the Ramsey cavity 3 and is excited by a resonant microwave field to undergo clock transition in the Ramsey cavity 3.
[0029] The detection light 50 induces the atoms that have completed the clock transition to emit fluorescence; the first light collecting device 6 is used to collect the clock transition fluorescence signal and the first stray light signal generated during the light detection process, and the clock transition fluorescence signal and the first stray light signal are used as the first signal and input into the differential operation module 8; the reference light 51 does not interact with the atoms; the second light collecting device 7 is used to collect the second stray light signal generated by the reference light 51, and its function is equivalent to a noise collector, and the second stray light signal is used as the second signal and input into the differential operation module 8; the differential operation module 8 is used to perform differential operation on the first signal and the second signal, and output the clock transition fluorescence signal that eliminates the stray light background; the clock transition fluorescence signal is fed into the servo module 9, and is processed by the voltage-controlled crystal oscillator 10 and the microwave signal source 11, so that the microwave field frequency output by the microwave signal source 11 is stabilized at the clock transition frequency of the atom, completing the closed-loop locking of the atomic clock. The atomic beam 12 is a highly collimated atomic beam.
[0030] In practical applications, the bell-state purification process 2 is generally implemented using a magnet state selection method and / or an optical pumping method; the atomic beam that has completed the bell-state purification enters the Ramsey cavity 3, where it is excited by the resonant microwave field to undergo a bell transition; the condition for the occurrence of the resonance is that the microwave field frequency is the same as the bell transition frequency.
[0031] When the atomic beam clock based on fluorescence differential detection works, the laser emitted by the laser 4 generates two laser beams of equal power and equal spot size after passing through the spectroscope 5: the first laser beam and the second laser beam, wherein the first laser beam is used as the detection light 50 to induce the atoms that have completed the clock transition to emit fluorescence, and the fluorescence is collected by the first light collecting device 6 together with the stray light generated in the light detection process, and then used as an input signal of the differential operation module 8; the second laser beam is used as the reference light 51, which passes through the same physical environment as the detection light 50, but does not interact with the atoms, and the generated stray light is collected by another identical second light collecting device 7 as another input signal of the differential operation module 8. Obviously, the stray light generated by the detection light 50 and the reference light 51 of the differential detection device have the same characteristics, and will cancel each other after the differential operation, and finally output the pure clock transition fluorescence signal induced by the detection light.
[0032] In practical applications, the second light collecting device 7 is placed inside the vacuum chamber 13 or in the atmospheric environment; the clock transition signal for eliminating stray light output by the differential operation module 8 is input into the servo module 9; the servo module 9 performs frequency demodulation on the clock signal to obtain a correction voltage, and the correction voltage adjusts the control voltage of the voltage-controlled crystal oscillator 10 so that the output frequency of the microwave signal source 11 is always stable at the clock transition frequency of the atoms, realizing closed-loop locking of the atomic beam clock, and finally outputting a standard frequency signal with high stability.
[0033] Based on the principle structure of the aforementioned fluorescence differential detection atomic beam clock, two specific implementation methods are specifically presented: Example 1 and Example 2.
[0034] The common features of the first embodiment and the second embodiment are as follows: in the vacuum chamber 13, the beam source generating device 1 is a cesium atomic furnace, which can generate a highly collimated cesium atomic beam 12; the atomic state purification process 2 is completed by optical pumping; the Ramse of the microwave field required for the atomic beam clock transition is provided; y Cavity 3 is a spatially separated dual-oscillation field microwave cavity; laser 4 provides pumping light 41 required for atomic state purification process 2, detection light 50 for detecting clock transition signals, and reference light 51 as a noise source. The frequency of the detection light 50 is stabilized at the cyclic transition line of cesium atoms D2: F=4→F′=5; the frequency of the pumping light 41 is stabilized at D2: F=4→F′=4, and the pumping light 41 is obtained by frequency shifting 251MHz by the first acousto-optic modulator 201 from the laser emitted by laser 4; the pumping light enters the vacuum chamber 13 through the first light window 15, interacts with the cesium atomic beam 12, and completes the state purification process. After the purification process is completed, the cesium atoms are distributed to the ground state energy level F=3. The atoms at the ground state energy level F=3 are in Ramse y After the microwave magnetic field in cavity 3 is excited by the microwave frequency of the clock transition frequency, F=3, m F =0→F=4,mF = 0 minutes transition; the detection light 50 enters the vacuum chamber 13 through the second light window 14, and F = 4, m F =0 energy level of cesium atoms to complete the clock transition detection; where F is the ground state energy level; F' is the excited state energy level; m F is the magnetic energy level.
[0035] Embodiment 1
[0036] Figure 2 The first embodiment of the atomic beam clock based on fluorescence differential detection provided by the present invention is shown in FIG. Figure 2 As shown, the first light collecting device 6 and the second light collecting device 7 are both in the vacuum chamber 13, and the two light collecting devices are exactly the same, wherein the first light collecting device 6 collects the clock transition fluorescence signal induced by the detection light 50 and the first stray light introduced by factors such as light window scattering and light beam divergence; the reference light 51 becomes a noise source with the same power as the detection light 50 after frequency shifting by the second acousto-optic modulator 17, and overlaps with the atomic beam, but does not resonate with each other, so that the second light collecting device 7 only collects the second stray light signal; the relative position where the detection light 50 and the atomic beam 12 overlap in the first light collecting device 6 is the same as the relative position where the reference light 51 and the atomic beam 12 overlap in the second light collecting device 7, so as to ensure that the stray light collected by the first light collecting device 6 is the same as the stray light collected by the second light collecting device 7.
[0037] Embodiment 2
[0038] Figure 3 The structure diagram of the second specific embodiment of the atomic beam clock based on fluorescence differential detection provided by the present invention is as follows: Figure 3 As shown, the first light collecting device 6 is in the vacuum chamber 13, and the second light collecting device 7 is in the atmospheric environment. The two light collecting devices are exactly the same, wherein the first light collecting device 6 collects the clock transition fluorescence signal induced by the detection light 50 and the stray light introduced by factors such as light window scattering and light beam divergence; the reference light 51 has the same frequency and power as the detection light 50, and the stray light generated by the reference light 51 as a noise source is collected by the second light collecting device 7; the third light window 16 is fine-tuned to better simulate the optical noise caused by the second light window 14.
[0039] Figure 2 and Figure 3The first light collecting device 6 and the second light collecting device 7 also include a first light detector 601 and a second light detector 701 with the same physical characteristics. The light signals collected by the first light detector 601 and the second light detector 701 are converted into electrical signals for convenient processing. The two electrical signals are differentiated by the differential operation module 8 to output a clock transition signal that eliminates stray light. The clock transition signal is input to the servo module 9. The servo module 9 performs frequency discrimination processing on the clock signal to obtain a correction voltage. The correction voltage adjusts the control voltage of the voltage-controlled crystal oscillator 10 so that the output frequency of the microwave signal source 11 is always stable at the atomic clock transition frequency, realizing the closed-loop locking of the atomic beam clock, and finally outputting a standard frequency signal with high stability.
[0040] The present invention also provides a method for realizing an atomic beam clock based on fluorescence differential detection, comprising the following steps:
[0041] Step 1: The beam source generating device 1 generates a highly collimated atomic beam, which is processed by state purification means such as a magnetic state selection method and / or an optical pumping method to eliminate the atomic population in any one of the two clock states and generate a single clock state atom.
[0042] Step 2: The single clock-state atom enters the Ramsey cavity 3, is excited by the microwave field in the Ramsey cavity 3, and undergoes clock transition, wherein the frequency of the microwave field is the same as the clock transition frequency.
[0043] Step 3: The extraction of the clock transition information is performed by differential light detection. One of the laser beams is used as the detection light 50, which passes through the light window and interacts with the atoms in the vacuum that have undergone clock transition, generating a laser-induced fluorescence signal. The fluorescence signal and the stray light signal generated by factors such as light window scattering and the divergence of the light beam itself during the light detection process are collected by a light collecting device. The signal collected by the light collecting device contains both clock transition information and stray light information. Another laser beam with equal power and spot size from the same laser 4 is used as the reference light 51, which does not interact with the atoms, but experiences the same environment as the detection light 50, generates the same stray light, and is collected by another identical light collecting device.
[0044] Step 4: Perform differential operation on the signals collected by the two light collection devices to eliminate light source fluctuations and light background noise, and obtain a pure clock transition fluorescence signal with a high signal-to-noise ratio, which is used for closed-loop locking of the atomic beam clock and ultimately outputs a standard frequency signal with high frequency stability.
[0045] Compared with the direct detection method of the traditional beam-type atomic clock, the present invention uses a differential detection method to reduce stray light noise, improve the signal-to-noise ratio of the clock transition signal, and is beneficial to improving the performance of the beam-type atomic clock.
[0046] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the various embodiments can be referenced to each other.
[0047] The principles and implementation methods of the present invention are described in this article using specific examples. The description of the above embodiments is only used to help understand the method and core idea of the present invention. At the same time, for those skilled in the art, according to the idea of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.
Claims
1. An atomic beam clock based on fluorescence differential detection, characterized in that: include: A beam source generating device, a Ramsey cavity for providing the microwave field required for the atomic beam clock transition, a differential detection device for detecting the clock transition signal, a laser, a spectroscope, a servo module, a voltage-controlled crystal oscillator and a microwave signal source; The differential detection device includes a first light collecting device, a second light collecting device and a differential operation module; The differential operation module is used to perform a differential operation on the first signal collected by the first light collecting device and the second signal collected by the second light collecting device; The laser generates a beam of detection light and a beam of reference light through the beam splitter; The beam source generating device, the Ramsey cavity and the first light collecting device are arranged in a vacuum chamber; the beam source generating device generates an atomic beam, and after an atomic state purification process, the atomic beam in a single clock state enters the Ramsey cavity and is excited by a resonant microwave field to undergo a clock transition in the Ramsey cavity; The detection light passes through the first light collecting device to induce the atoms that have completed the clock transition to emit fluorescence; the first light collecting device is used to collect the clock transition fluorescence signal and the first stray light signal generated during the light detection process, and the clock transition fluorescence signal and the first stray light signal are used as the first signal and input into the differential operation module; the reference light passes through the second light collecting device in the same way as the detection light passes through the first light collecting device, and the reference light does not interact with the atoms; the second light collecting device is used to collect the second stray light signal generated by the reference light, and the second stray light signal is used as the second signal and input into the differential operation module; the differential operation module is used to perform differential operation on the first signal and the second signal, and output a clock transition fluorescence signal that eliminates the stray light background; the clock transition fluorescence signal is fed into the servo module, and is processed by the voltage-controlled crystal oscillator and the microwave signal source, so that the microwave field frequency output by the microwave signal source is stabilized at the clock transition frequency of the atom, thereby completing the closed-loop locking of the atomic clock.
2. The atomic beam clock based on fluorescence differential detection according to claim 1, characterized in that: The atomic state purification process is achieved through a magnetic state selection method and an optical pumping method.
3. The atomic beam clock based on fluorescence differential detection according to claim 1, characterized in that: The atomic state purification process is achieved by a magnetic selection method or an optical pumping method.
4. The atomic beam clock based on fluorescence differential detection according to any one of claims 1 to 3, characterized in that: The power of the detection light is the same as the power of the reference light, and the spot of the detection light is the same as the spot of the reference light.
5. The atomic beam clock based on fluorescence differential detection according to any one of claims 1 to 3, characterized in that: The first light collecting device is identical to the second light collecting device.
6. The atomic beam clock based on fluorescence differential detection according to any one of claims 1 to 3, characterized in that: The second light collecting device is arranged in the vacuum chamber, or outside the vacuum chamber.
7. The atomic beam clock based on fluorescence differential detection according to claim 6, characterized in that: When the second light collecting device is located in the vacuum chamber, the frequency of the reference light is a non-atomic resonance frequency; When the second light collecting device is located outside the vacuum chamber, the frequency of the reference light is an atomic resonance frequency, or the frequency of the reference light is a non-atomic resonance frequency.