Atomic interferometer initial state preparation laser system and method
A laser system for preparing initial states using an atomic interferometer with composite optical pumping is developed. By utilizing an optical phase-locked loop module to achieve frequency phase locking of cooling light and return pump light, and combining optical pumping technology to prepare atoms in other states, the system solves the problem of low atom utilization in existing technologies and improves the detection signal-to-noise ratio and preparation efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-15
- Publication Date
- 2026-04-10
AI Technical Summary
In existing methods for preparing initial states for atomic interferometers, low atomic utilization leads to limited detection signal-to-noise ratio, and state preparation efficiency and purity cannot be simultaneously satisfied. Furthermore, existing schemes increase the dead time of gravity measurement and have high requirements for microwave/Raman π pulse efficiency.
A laser system for initial state preparation using an atomic interferometer with composite optical pumping is proposed. The reference laser is locked at the 85Rb cooling transition peak. The beat frequency phase-locked loop module is combined with the optical phase-locked loop module to achieve phase-locked looping of cooling light, pump back light and reference light. Atoms in other states are efficiently prepared to the state through optical pumping technology. The optical phase-locked loop module is used to realize laser frequency jump and optical frequency time-division multiplexing.
It improves interference fringe contrast and measurement sensitivity, enhances the detection signal-to-noise ratio, and achieves high-purity and high-efficiency initial state preparation without increasing MOT time.
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Figure CN121840339A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of atomic interferometer technology, specifically to a laser system for preparing the initial state of an atomic interferometer, and a method for preparing the laser. Background Technology
[0002] To determine the quantization axis during interference, a bias magnetic field needs to be applied along the propagation direction of the Raman light. Atoms at different magnetic sublevels experience different first-order Zeeman shifts in the magnetic field, leading to varying detuning of the two-photon transitions of atoms at each sublevel relative to the Raman light. Consequently, when interacting with the Raman light, atoms at different sublevels experience different effective Rabi frequencies, resulting in a deterioration in the contrast of the interference fringes.
[0003] To overcome the above problems experimentally, atoms need to be prepared before interference. State. Compared to Atoms in a certain state The atoms in the state are not sensitive to the first-order Zeeman effect. This avoids the influence of the first-order Zeeman effect on the contrast of the interference fringes, as well as the influence of magnetic field system errors and noise on the measurement.
[0004] Currently, the commonly used methods for state preparation are microwave or Raman optical state selection. Both methods only select states in the state selected by the light source. The atoms in the selected state are processed. A beam with a frequency of [missing information] is generated using microwave or Raman laser. The resonant π pulse acts on the atom to prepare the initial state. The difference between the two is that microwave state selection uses an external microwave horn antenna for state preparation, with the antenna placed close to the detection area of the vacuum cavity, and its input signal is output from the microwave source. Raman state selection is achieved through Raman laser.
[0005] The initial state preparation process of the two schemes can be divided into the following steps in terms of time sequence.
[0006] The first step is to apply a bias magnetic field to the selected state region to cause the atomic energy levels to split; the second step is to open a channel that can... The third step involves applying a first microwave / Raman π pulse to completely remove all atoms from the upper atom. Atoms in the state transfer In terms of state; the fourth step is to open a channel that can... The fifth step involves applying a second microwave / Raman π pulse to completely remove the atoms from the upper atom. The atom in the state transitions back to Step 6: Open a window that can... The seventh step involves blowing away all atoms with a single microwave / Raman π pulse. The atoms on it eventually yield Magnetically insensitive pure state atoms.
[0007] The advantages of microwave state selection are its insensitivity to atomic velocities and its ability to avoid the effects of spontaneous emission after transitioning to an excited state, resulting in high state selection efficiency. The advantages of Raman state selection are that it simultaneously selects for atomic velocity / temperature, leading to a narrower atomic velocity distribution and better fringe contrast during the interference process and Raman light interaction.
[0008] However, both approaches also have certain drawbacks. On the one hand, because the atoms at the initial moment... The magnetic quantum energy levels are evenly distributed, which means that the first microwave / Raman state selection will discard 4 / 5 of the atoms, significantly reducing the signal-to-noise ratio of the detector. On the other hand, in order to avoid the influence of background hot atoms and the non-resonant Raman light being scattered by atoms and interacting with atoms again on the interference stage, both schemes mostly use a three-pulse sequence state preparation, which increases the dead time of gravity measurement to a certain extent, while also placing high demands on the efficiency of microwave / Raman π pulses. Summary of the Invention
[0009] One objective of this invention is to provide a laser system for preparing the initial state of an atomic interferometer based on composite optical pumping, used for the initial state preparation of a cold atom interferometer, in order to improve the contrast of interference fringes and the measurement sensitivity.
[0010] The technical solution adopted by this invention to solve its technical problem is: a laser system for preparing the initial state of an atomic interferometer, comprising a reference laser and a modulation-transfer frequency stabilization module, an optical phase-locked loop module one, and an optical phase-locked loop module two, respectively connected to the reference laser. It also includes a pump-back laser and a cooling laser connected to the optical phase-locked loop module one and the optical phase-locked loop module two, respectively. The cooling laser is further connected to an acousto-optic modulator one and an acousto-optic modulator two. A laser beam is input to the reference laser (to the modulation-transfer frequency stabilization module), and the frequency of the reference laser is locked at a specific value using modulation-transfer frequency locking technology. 85 On the transition line from F=3 to F'=4 of Rb atoms, a pump laser and a reference laser are each input to an optical phase-locked loop module one. Using beat frequency phase-locked loop technology, the frequency of the pump laser is locked to the frequency of the reference laser, with a frequency difference of +5363.071MHz. A cooling laser and a reference laser are each input to an optical phase-locked loop module two. Using beat frequency phase-locked loop technology, the frequency of the cooling laser is locked to the frequency of the reference laser, with a frequency difference of -1366.486MHz. One laser beam output from the cooling laser is frequency-shifted by +160MHz through an acousto-optic modulator one to generate cooling light, and the other laser beam output is frequency-shifted by -86MHz through an acousto-optic modulator two to generate optical pump light.
[0011] The second objective of this invention is to provide a method for preparing laser light in the initial state of an atomic interferometer based on composite optical pumping, comprising the following steps:
[0012] S1, turn on the return pump light, and move the atoms from... All prepared to superior;
[0013] S2, a bias magnetic field is applied to the selected state region to cause the atomic energy levels to split;
[0014] S3, the probe light after frequency hopping is activated to the magneton energy level Atoms in the state are pumped, pumping most atoms to F=1, m f =0 state;
[0015] S4, using microwave π pulses to induce atomic transitions to F=2,m f =0 and clear the atoms in the remaining F=1 state;
[0016] S5, finally, velocity selection and removal of excess F=2 state atoms were performed using Raman pulses; the final atoms were prepared in F=1, m f =0, and speed / temperature selection was performed in the vertical direction.
[0017] Furthermore, a reference laser is used alone to lock onto... 85 At the Rb cooling transition peak, a high signal-to-noise ratio frequency discrimination signal is generated. At the same time, two optical phase-locked loops, optical phase-locked loop module one and optical phase-locked loop module two, can be used to realize beat frequency phase-locking of cooling light, pump back light and reference light respectively, so that the laser frequency jump is flexible.
[0018] Furthermore, by using a beam of linearly polarized light to pump atoms in the F=1 state to F'=0, on the one hand, due to the dipole forbidden zone, atoms in the F=1, mf=0 state cannot be pumped to F'=0, mf=0, ensuring that the number of atoms in the F=1, mf=0 state remains unchanged; on the other hand, only atoms in the F=1, mf=±1 state will be pumped to F'=0, mf=0, ±1. Subsequently, atoms in the F'=0, mf=0, ±1 state will randomly fall back to F=1, mf=0, ±1 state through spontaneous emission. By using a beam of linearly polarized light, we can re-prepare atoms in the F=1, mf=±1 state that were blown out in the original scheme to F=1, mf=0 state, thereby significantly increasing the number of atoms participating in the interference.
[0019] The beneficial effects of this invention are:
[0020] This invention uses a reference laser locked to the 85Rb cooling transition peak, which can generate a high signal-to-noise ratio frequency discrimination signal and achieve better frequency locking effect. It uses two optical phase-locked loops to realize the beat frequency phase locking of the cooling light, the pump back light and the reference light respectively, which makes the laser frequency jump change more flexible and the laser-atomic interaction scheme more complete.
[0021] This invention employs a coincident light pumping method that can convert other... Atoms in the state are efficiently prepared to [a state] using a single pump light beam. In terms of state, the detection signal-to-noise ratio is significantly improved without increasing the MOT time.
[0022] This invention solves the problems of low atom utilization leading to limited detection signal-to-noise ratio and the inability to simultaneously satisfy state preparation efficiency and purity in existing initial state preparation methods. While selecting atoms in different states, a laser frequency jump is achieved through an optical phase-locked loop, enabling time-division multiplexing of the probe light in the laser system to transfer other... Atoms in the state are pumped to This approach achieves high-purity and high-efficiency initial state preparation while improving the detection signal-to-noise ratio. Attached Figure Description
[0023] Figure 1 This is a schematic diagram of the laser fabrication system of the present invention;
[0024] Figure 2 This is a schematic diagram of the laser frequencies used in the laser fabrication system of the present invention;
[0025] Figure 3 This is a flowchart of the initial state preparation method for the atomic interferometer of the present invention.
[0026] The labels in the attached figures are as follows: 110—Pump-back laser, 120—Reference laser, 130—Cooling laser, 121—Modulation transfer frequency stabilization module, 122—Optical phase-locked loop module one, 123—Optical phase-locked loop module two, 131—Acousto-optic modulator one, 132—Acousto-optic modulator two. Detailed Implementation
[0027] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.
[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
[0029] like Figure 1 As shown, this embodiment provides a laser system for preparing the initial state of an atomic interferometer based on composite optical pumping, including a pump-back laser 110, a reference laser 120, a cooled laser 130, a modulation-transfer frequency stabilization module 121, an optical phase-locked loop module one 122, an optical phase-locked loop module two 123, an acousto-optic modulator one 131, and an acousto-optic modulator two 132.
[0030] The technical solution of this embodiment is based on 87 The frequencies of the laser beams used in the initial state preparation of Rb atoms are as follows: Figure 2 As shown.
[0031] In the technical solution of this embodiment, a laser beam is input from the reference laser 120 to the modulation-transfer-frequency stabilization module 121, and the frequency of the reference laser is locked at a specific frequency using modulation-transfer-frequency locking technology. 85 The transition line from F=3 to F'=4 for Rb atoms.
[0032] A laser beam is input to the pump-back laser 110 and the reference laser 120 respectively. The frequency of the pump-back laser is locked to the frequency of the reference laser using beat frequency locking technology. The frequency difference between the pump-back laser and the reference laser is +5363.071MHz.
[0033] A laser beam is input to the cooling laser 130 and the reference laser 120 respectively, and the frequency of the cooling laser is locked to the frequency of the reference laser using beat frequency phase-locked loop module 123. The frequency difference between the cooling laser and the reference laser is -1366.486MHz.
[0034] One laser beam output from the cooling laser 130 is frequency-shifted by the acousto-optic modulator 131 by +160MHz to generate cooling light, and the other laser beam output is frequency-shifted by the acousto-optic modulator 2132 by -86MHz to generate optical pump light.
[0035] In this embodiment, the laser system employs three lasers: a pump-back laser 110, a reference laser 120, and a cooling laser 130. The reference laser 120 is locked to... 85 At the cooling transition peak of Rb, this transition signal is very strong, which can generate a high signal-to-noise ratio frequency discrimination signal and achieve better locking effect. At the same time, by employing two optical phase-locked loop modules, the laser frequency jump change is flexible, and the return pump light 2 and the optical pump light can work simultaneously during the initial state preparation stage.
[0036] This plan aims to include other... Atoms in the state are pumped to In this approach, an optical pumping stage is added to the commonly used scheme. Since the magnetic field in the state preparation region is mainly vertical, a beam of light is applied along the vertical direction... 87 Rb atoms D2 line 1 to Linearly polarized light undergoing transition resonance can be viewed as a superposition of left-handed and right-handed circularly polarized light. Since the laser direction is parallel to the magnetic field direction, atoms primarily undergo [transition resonance]. and The probability of a π transition is much lower than the previous two, and atomic absorption... and After the photon reaches the excited state, it spontaneously emits back Because the selection rule prevents further absorption of photons, these states are retained and form a dark state, thus enabling the pumping of other states to the desired interference state. state.
[0037] In the initial state laser preparation process, the probe light, whose polarization and propagation direction perfectly meet the pumping requirements of the magnetic sub-levels, is idle. By changing the frequency of the probe light through frequency hopping, it can be used as the pump light for the magnetic sub-levels, thereby pumping most atoms into a magnetically insensitive state. The specific implementation steps are as follows.
[0038] S1, turn on the return pump light, and move the atoms from... All prepared to superior;
[0039] S2, a bias magnetic field is applied to the selected state region to cause the atomic energy levels to split;
[0040] S3, the probe light after frequency hopping is activated to the magneton energy level Atoms in the state are pumped, pumping most atoms to F=1, m f =0 state;
[0041] S4, using microwave π pulses to induce atomic transitions to F=2,m f =0 and clear the atoms in the remaining F=1 state;
[0042] S5, finally, velocity selection and removal of excess F=2 state atoms were performed using Raman pulses; the final atoms were prepared in F=1, m f =0, and speed / temperature selection was performed in the vertical direction.
[0043] Meanwhile, the laser system in this invention uses a separate reference laser 120 locked to... 85At the Rb cooling transition peak, a high signal-to-noise ratio frequency discrimination signal is generated. At the same time, two optical phase-locked loops, optical phase-locked loop module 122 and optical phase-locked loop module 223, can be used to realize beat frequency phase-locking of cooling light, pump back light and reference light respectively, so that the laser frequency jump is flexible.
[0044] like Figure 3 As shown, the method for preparing the initial state of the atomic interferometer in this embodiment is as follows.
[0045] Atoms in the F=1 state are pumped to F'=0 using a beam of linearly polarized light.
[0046] On the one hand, due to the dipole forbidden state, F=1, mf=0 cannot be pumped to F'=0, mf=0, thus ensuring that the number of atoms in the F=1, mf=0 state remains unchanged.
[0047] On the other hand, only atoms at F=1, mf=±1 will be pumped to F'=0, mf=0, ±1. Subsequently, atoms at F'=0, mf=0, ±1 will randomly fall back to F=1, mf=0, ±1 through spontaneous emission.
[0048] By using a beam of linearly polarized light, atoms that were blown out in the original scheme and were in the F=1, mf=±1 state can be re-prepared into F=1, mf=0 state, thereby significantly increasing the number of atoms participating in the interference.
[0049] Those skilled in the art will readily understand that the above description is merely a preferred use case of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A laser system for preparing the initial state of an atomic interferometer, characterized in that: The system includes a reference laser (120) and a modulation-transfer frequency stabilization module (121), an optical phase-locked loop module one (122), and an optical phase-locked loop module two (123) connected to the reference laser (120). It also includes a pump-back laser (110) and a cooling laser (130) connected to the optical phase-locked loop module one (122) and the optical phase-locked loop module two (123), respectively. The cooling laser (130) is also connected to an acousto-optic modulator one (131) and an acousto-optic modulator two (132). A laser beam is input to the modulation-transfer frequency stabilization module (121) from the reference laser (120), and the frequency is... Locked on the transition line of the atom, a laser beam is input to the return pump laser (110) and the reference laser (120) respectively to the optical phase-locked loop module one (122), and the frequency of the return pump laser is locked to the frequency of the reference laser. A laser beam is input to the cooling laser (130) and the reference laser (120) respectively to the optical phase-locked loop module two (123), and the frequency of the cooling laser is locked to the frequency of the reference laser. One laser beam output by the cooling laser (130) is frequency-shifted by the acousto-optic modulator one (131) to generate cooling light, and the other laser beam output is frequency-shifted by the acousto-optic modulator two (132) to generate optical pump light.
2. A method for preparing laser light using the system as described in claim 1, characterized in that, Includes the following steps: S1, turn on the return pump light, and move the atoms from... All prepared to superior; S2, a bias magnetic field is applied to the selected state region to cause the atomic energy levels to split; S3, the probe light after frequency hopping is activated to the magneton energy level Atoms in the state are pumped, pumping most atoms to F=1, m f =0 state; S4, using microwave π pulses to induce atomic transitions to F=2,m f =0 and clear the atoms in the remaining F=1 state; S5, finally, velocity selection is performed using Raman pulses to remove excess F=2 state atoms; The final atoms were prepared at F=1, m f =0, and speed / temperature selection was performed in the vertical direction.
3. The method for preparing laser light in the initial state of an atomic interferometer according to claim 2, characterized in that, The reference laser (120) is locked in 85 At the Rb cooling transition peak, while generating a high signal-to-noise ratio frequency discrimination signal, optical phase-locked loop module one (122) and optical phase-locked loop module two (123) respectively realize beat frequency phase-locking of cooling light, return pump light and reference light.
4. A method for preparing laser light in the initial state of an atomic interferometer according to claim 2 or 3, characterized in that, Atoms in the F=1 state are pumped to F'=0 by a beam of linearly polarized light, thus re-preparing the blown-out atoms in the F=1, mf=±1 state to F=1, mf=0, thereby increasing the number of atoms participating in the interference.