Single raman optical modulation atomic interferometer laser system and method

Abstract

The application discloses a single-Raman light modulation atomic interference laser system, comprising a fast modulation driving module and a narrow-line-width laser connected with the fast modulation driving module, wherein the narrow-line-width laser is connected with an electro-optic modulator and a modulation transfer lock module through a fiber beam splitter, and the electro-optic modulator is connected with an output optical fiber; and the application further discloses an interference method thereof, wherein the frequency of the narrow-line-width laser is locked through the modulation transfer lock, the frequency is unlocked by turning off the modulation transfer lock, and the frequency is relocked by turning on the modulation transfer lock again; the high-speed modulation process is only carried out when the first Raman pulse is turned on, equivalent Doppler frequency shift in the low-speed state of atoms is realized, and the interference test in the low-speed state of atoms is ensured, which can effectively support the miniaturization and engineering requirements of quantum precision measurement application.

Description

Technical Field

[0001] This invention belongs to the field of quantum precision measurement technology, specifically relating to a single Raman light modulated atomic interference laser system and its method. Background Technology

[0002] Gravity measurement is of great significance to fundamental and cutting-edge scientific research in resource exploration, space science, oceanography, geodesy, geophysics, and geodynamics. For example, by measuring the distribution of the gravity field, the distribution of underground materials can be deduced, enabling efficient exploration of oil and gas resources deep within the Earth, achieving a "penetration" and "illumination" of the Earth's depths; high-precision measurement of Earth's gravity parameters establishes a basic gravity network, providing accurate gravity parameters for rocket launches, manned spaceflight, and lunar exploration projects, effectively serving space science; and by monitoring anomalous changes in the Earth's gravity field, timely warnings can be issued for earthquakes, tsunamis, volcanic eruptions, and other events.

[0003] To address the need for absolute gravity measurement, a new type of gravimeter has emerged in recent years—the cold atom gravimeter. This type of gravimeter employs a novel atomic interferometry technique, obtaining gravity information by observing the phase of interference fringes as atoms freely fall in a gravitational field. Because the atomic gravimeter uses cold atoms in an ultra-high vacuum system as its research object, the atomic energy level structure is extremely stable, thus offering advantages such as high precision, good stabilization, and high repeatability. Furthermore, it avoids the mechanical wear and reduced lifespan associated with free-fall absolute gravimeters.

[0004] Improving the data output rate of absolute gravity measurements is one of the important means to improve the spatial resolution of dynamic absolute gravity measurements; reducing the size of the equipment to facilitate transportation is the key to solving the miniaturization and engineering problems of quantum precision measurement equipment using cold atom clusters as the verification medium. Employing single Raman light-modulated atomic interferometry can effectively improve the data output rate of high-data-output dynamic absolute gravity measurement equipment using cold atom clusters as the verification medium, and reduce the size of the gravity sensor. Summary of the Invention

[0005] To address the issue of insufficient data output rate in high-data-output-rate dynamic absolute gravity measurement devices using cold atom clusters as the testing medium, one objective of this invention is to provide a single Raman-modulated atomic interference laser system. This system effectively reduces the free flight time of the atom clusters from the confinement stage to the interference stage, thereby improving the data output rate of high-data-output-rate dynamic absolute gravity measurement devices using cold atom clusters as the testing medium and reducing the size of the gravity sensor.

[0006] To achieve the above objectives, the technical solution adopted by the present invention to solve its technical problem is: a single Raman optical modulation atomic interference laser system, comprising a fast modulation driving module and a narrow linewidth laser connected to the fast modulation driving module, wherein the narrow linewidth laser is connected to an electro-optic modulator and a modulation transfer frequency locking module respectively through an optical fiber beam splitter, and the electro-optic modulator is connected to an output optical fiber.

[0007] The second objective of this invention is to provide an interference method for a single Raman-modulated atomic interference laser system, wherein the timing sequence of the interference segment includes the following steps: S1, the modulation transfer frequency locking module is activated. The laser output from the narrow linewidth laser is used as the input reference of the modulation transfer frequency locking module through the fiber beam splitter. The modulation transfer frequency locking module controls the seed frequency of the narrow linewidth laser through the seed laser modulation input to achieve atomic trapping, cooling and state selection, and obtain cold atom clusters. S2, disable the modulation transfer frequency lock module to unlock the frequency, switch the seed laser modulation input signal from the modulation transfer frequency lock module to the fast modulation drive module, adjust the output voltage of the fast modulation drive, and pull the seed laser frequency of the narrow linewidth laser to cause it to shift. S3 uses a fast modulation drive to rapidly modulate the output voltage only when the first Raman pulse is activated, achieving high-speed frequency change of the narrow-linewidth laser seed laser. The fast modulation drive module gradually reduces the bias voltage to the output voltage of the modulation transfer frequency-locking module at frequency unlock time. The modulation transfer frequency-locking module is then restarted, and the seed laser modulation input is switched back to the modulation transfer frequency-locking module, restoring the seed laser frequency to a relockable state. S4, after the high-speed modulation ends, the second and third Raman pulses are turned on in sequence as the interference segment; S5, finally proceeding to the final state detection step.

[0008] Furthermore, the high-speed modulation process in step S3 includes three processes: high-speed modulation preparation, high-speed modulation of the laser frequency, and recovery of the laser frequency.

[0009] Furthermore, in steps S4 and S5 of the subsequent interference process, modulation transfer frequency locking remains enabled to ensure that the frequency of the narrow linewidth laser does not change.

[0010] Furthermore, the commonly used Raman pulse output power adjustment schemes include using an optical switch to turn the device on / off, or using an adjustable acousto-optic modulator.

[0011] The beneficial effects of this invention are as follows: This invention enables quasi-zero-velocity atomic interference, effectively reducing the free-flight time of atomic clusters from the confinement to the interference stage, and improving the data output rate of high-data-output-rate dynamic absolute gravity measurement devices using cold atomic clusters as the verification medium. Due to the reduced free-flight time, the size of high-data-output-rate dynamic absolute gravity measurement devices using cold atomic clusters as the verification medium can be effectively reduced. Simultaneously, high-speed modulation is used only when the first Raman beam is activated, effectively reducing the requirements for high-speed modulation drive and the technical implementation difficulty, which can strongly support the miniaturization and engineering needs of quantum precision measurement applications. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of the structure of the single Raman-modulated atomic interference laser system of the present invention; Figure 2 This is a schematic diagram of the interference method of the present invention; Figure 3 This is a schematic diagram of the timing of the interference segment in the single Raman optical modulation atomic interference technique of the present invention.

[0013] The labels in the attached figures are as follows: 1—fast modulation drive module, 2—narrow linewidth laser, 3—fiber beam splitter, 4—electro-optic modulator, 5—output fiber, 6—modulation transfer frequency locking module, 7—seed laser modulation input. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the invention, not the entire structure.

[0015] refer to Figure 1 As shown, this invention discloses a single Raman-modulated atomic interference laser system for low-speed atomic interference, comprising a fast modulation drive module 1 and a narrow-linewidth laser 2 connected to the fast modulation drive module 1. The fast modulation drive module 1 is used for high-speed modulation preparation, high-speed modulation, and frequency recovery of the narrow-linewidth laser 2. The narrow-linewidth laser 2 is connected to an electro-optic modulator 4 and a modulation transfer frequency-locking module 6 via an optical fiber beam splitter 3. Both the modulation transfer frequency-locking module 6 and the fast modulation drive module 1 serve as inputs to the narrow-linewidth laser 2. The modulation transfer frequency-locking module 6 is used for frequency locking of the narrow-linewidth laser 2. The electro-optic modulator 4 is connected to an output optical fiber 5. After high-speed modulation, the frequency of the narrow-linewidth laser 2 is first recovered by the fast modulation drive module 1, and then the modulation transfer frequency-locking module 6 is activated to lock the frequency of the narrow-linewidth laser 2.

[0016] refer to Figure 2 As shown, this invention discloses an interference method for a single Raman-modulated atomic interference laser system. The Raman-modulated atomic interference process includes three stages: atomic trapping, cooling and state selection, and frequency unlocking. Details are as follows.

[0017] S1, the modulation transfer frequency lock module 6 is activated, and the fast modulation drive module 1 feeds back the seed laser modulation input to the modulation transfer frequency lock module 6 to realize atomic trapping, cooling and state selection, and obtain cold atomic clusters.

[0018] S2, disable the modulation transfer frequency lock module 6 to unlock the frequency, switch the input modulation transfer frequency lock module 6 to the input narrow linewidth laser 2, adjust the output voltage of the fast modulation drive 1, and pull the seed laser frequency of the narrow linewidth laser 2 to cause it to deflect.

[0019] S3, using the fast modulation drive 1 to high-speed modulate the output voltage only when the first Raman pulse is turned on, the high-speed change of the seed laser frequency of the narrow linewidth laser 2 is achieved. The modulation transfer frequency locking module 6 is restarted to restore the laser frequency. The seed laser modulation input 7 is switched to the modulation transfer frequency locking module 6 again. The pull-bias voltage is gradually reduced to the output voltage of the modulation transfer frequency locking module 6 when the frequency is unlocked by the fast modulation drive 1, so that the seed laser frequency of the narrow linewidth laser 2 is restored to a relockable state. The high-speed adjustment of the pull-bias voltage by the fast modulation drive 1 is used to achieve the high-speed change of the seed laser frequency of the narrow linewidth laser 2 to achieve the relocking of the laser frequency.

[0020] The high-speed modulation process in this paper includes three steps: high-speed modulation preparation, high-speed modulation of the laser frequency, and laser frequency recovery. High-speed modulation preparation, high-speed modulation of the laser frequency, and laser frequency recovery are achieved through the fast modulation drive module 1. High-speed modulation preparation uses the fast modulation drive module 1 to modulate the bias voltage to bias the seed laser frequency of the narrow-linewidth laser 2. High-speed modulation of the laser frequency uses the fast modulation drive module 1 to rapidly adjust the bias voltage to achieve high-speed changes in the seed laser frequency of the narrow-linewidth laser 2. Laser frequency recovery uses the fast modulation drive module 1 to gradually reduce the bias voltage to the output voltage of the modulation transfer frequency lock 6 when the frequency is unlocked, thus restoring the seed laser frequency of the narrow-linewidth laser 2 to a relockable state.

[0021] The embodiments of the present invention provide a high-speed modulation process that is performed simultaneously with the activation of the first Raman pulse, aiming to achieve an equivalent Doppler frequency shift in the low-speed state of atoms, thereby ensuring that interferometric testing can be performed in the low-speed state of atoms.

[0022] S4, after the high-speed modulation ends, the second and third Raman pulses are turned on in sequence as the interference segment; during the subsequent interference process, the modulation transfer frequency lock 6 is continuously turned on to keep the frequency of the narrow linewidth laser 2 from changing.

[0023] S6, finally proceeding to the final state detection step.

[0024] refer to Figure 3 As shown in Figure 11, the Raman pulse power variation curve is shown in Figure 12, and the laser frequency variation curve is shown in Figure 13. The laser frequency variation process includes the modulation transfer frequency lock unlocking time 13, the high-speed modulation preparation time 14, the high-speed modulation laser frequency process 15, the laser frequency recovery process 16, and the modulation transfer frequency lock relocking time 17. Figure 18 shows three activated Raman pulses. The laser frequency variation and frequency locking are both achieved by adjusting the bias voltage of the two seed laser modulation ports of the narrow linewidth laser.

[0025] The Raman pulse power variation shown in Figure 11 is achieved by adjusting the Raman pulse output power. Commonly used Raman pulse output power adjustment schemes include using an optical switch to turn the device on / off, or adjusting the input power of the acousto-optic modulator to adjust the Raman pulse output power.

[0026] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The above descriptions are merely preferred embodiments of the invention, but the invention is not limited to the contents disclosed in these embodiments and the accompanying drawings. Many other equivalent embodiments may be included without departing from the spirit of the invention, and the scope of the invention is determined by the scope of the appended claims.

Claims

1. An interference method for a single Raman-modulated atomic interference laser system, characterized in that, The laser system includes a fast modulation drive module (1) and a narrow linewidth laser (2) connected to the fast modulation drive module (1). The narrow linewidth laser (2) is connected to an electro-optic modulator (4) and a modulation transfer frequency-locking module (6) via an optical fiber beam splitter (3). The electro-optic modulator (4) is connected to an output optical fiber (5). The system includes the following steps: S1, turn on the modulation transfer frequency lock module (6), the laser output of the narrow linewidth laser (2) is used as the input reference of the modulation transfer frequency lock module (6) through the fiber beam splitter (3), the modulation transfer frequency lock module (6) performs feedback control on the seed frequency of the narrow linewidth laser (2) through the seed laser modulation input, and realizes the laser frequency required for atomic trapping, cooling and state selection; S2, close the modulation transfer frequency lock module (6) to unlock the frequency, switch the seed laser modulation input signal from the modulation transfer frequency lock module (6) to the fast modulation drive module (1), adjust the output voltage of the fast modulation drive module (1), and pull the narrow linewidth laser (2) to make it deflect; S3, while the first Raman pulse is turned on, the fast modulation drive module (1) is used to high-speed modulate the output voltage to realize the high-speed change of the seed laser frequency of the narrow linewidth laser (2). The fast modulation drive module (1) gradually reduces the bias voltage to the output voltage of the modulation transfer frequency locking module (6) when the frequency is unlocked. The modulation transfer frequency locking module (6) is restarted, and the seed laser modulation input is switched to the modulation transfer frequency locking module (6) again to realize the seed laser frequency is restored to the state that can be re-locked. S4, after the high-speed modulation ends, the second and third Raman pulses are turned on in sequence to complete the interference segment; S5, enter the final state detection.

2. The interference method for a single Raman-modulated atomic interference laser system according to claim 1, characterized in that, The high-speed modulation process in step S3 includes high-speed modulation preparation, high-speed modulation of the laser frequency, and recovery of the laser frequency.

3. The interference method for a single Raman-modulated atomic interference laser system according to claim 2, characterized in that, In subsequent interference processes, the modulation transfer frequency locking module (6) remains on in steps S4 and S5, ensuring that the frequency of the narrow linewidth laser (2) does not change.

4. The interference method for a single Raman-modulated atomic interference laser system according to claim 3, characterized in that, The Raman pulse output power is adjusted by turning an optical switch on / off or by adjusting the input power of the acousto-optic modulator.

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