A method of atomic interferometry for gravity measurement with optical cavity assistance and apparatus therefor

Abstract

The application relates to the technical field of atomic interference, and provides an atomic interference gravity measurement method with optical cavity assistance and a device thereof, so as to solve the problem that existing atomic interferometers face laser power consumption limitation no matter whether the atomic interferometers are commercialized or the precision of the atomic interferometers is continuously improved. The method comprises the following steps: constructing an optical cavity, wherein the optical cavity comprises a first cavity mirror for coupling Raman light, a second cavity mirror for focusing Raman light and a third cavity mirror for reflecting Raman light which are sequentially spaced, a first waist spot exists between the first cavity mirror and the second cavity mirror, a second waist spot exists at a position after the second cavity mirror focuses, the second waist spot is used for detecting a cavity field mode of the optical cavity through transmission light of the third cavity mirror, and the first cavity mirror, the second cavity mirror and the third cavity mirror are coaxial and constitute a standing wave loop of the optical cavity; and a vacuum cavity is arranged between the first cavity mirror and the second cavity mirror, and cold atom groups are prepared at the first waist spot where the vacuum cavity is located.

Description

Technical Field

[0001] This application relates to the field of atomic interferometry, and more specifically, to an atomic interferometry gravity measurement method and apparatus with optical cavity assistance. Background Technology

[0002] In the field of atomic interferometry, particularly atomic gravimeters, as laboratory technology matures, experimental devices are inevitably moving towards commercialization and practical application. While maintaining their advantages of high precision and sensitivity, issues such as power consumption and robustness remain critical problems to be addressed. Simultaneously, with the emergence of high-momentum beam-splitting atomic interferometry schemes, achieving higher precision atomic interferometry requires laser power approaching or exceeding the watt level. This increased power consumption places stringent demands on laser performance and quality, further limiting the improvement of atomic interferometer accuracy. In short, both commercialization and continued precision improvements are constrained by the laser power consumption limitations of atomic interferometers.

[0003] Therefore, existing technologies still need to be improved. Summary of the Invention

[0004] The purpose of this application is to provide an atomic interferometric gravity measurement method and apparatus with optical cavity assistance, so as to solve the problem of laser power consumption limitation faced by existing atomic interferometers, whether in commercialization or in the continued improvement of accuracy.

[0005] To achieve the above objectives, the technical solution adopted in the first aspect of the embodiments of this application is as follows:

[0006] An atomic interferometric gravity measurement method with optical cavity assistance, comprising:

[0007] An optical cavity is constructed, wherein the optical cavity includes a first cavity mirror for coupling Raman light, a second cavity mirror for focusing Raman light, and a third cavity mirror for reflecting Raman light, which are spaced apart in sequence. There is a first waist spot between the first cavity mirror and the second cavity mirror, and there is a second waist spot at the position after focusing by the second cavity mirror. The second waist spot is used to detect the cavity field mode of the optical cavity through the transmitted light of the third cavity mirror. The first cavity mirror, the second cavity mirror, and the third cavity mirror are coaxial and form a standing wave loop of the optical cavity.

[0008] A vacuum chamber is placed between the first cavity mirror and the second cavity mirror, and cold atomic clusters are prepared in the vacuum chamber at the first waist spot;

[0009] A pulse sequence of Raman light is passed through the optical cavity, and interference operations such as beam splitting, reflection, and beam combining are performed on the cold atom cluster. The cavity length of the optical cavity satisfies the condition that both frequency components of the Raman light resonate with the cavity field mode of the optical cavity simultaneously.

[0010] The number distribution of atoms in cold atom clusters after interferometry is measured to obtain the interference phase information of the cold atom clusters;

[0011] The interference phase information is processed to obtain the atomic interference gravity measurement results.

[0012] According to the above-described atomic interferometric gravity measurement method with optical cavity assistance, after the step of placing a vacuum cavity between the first cavity mirror and the second cavity mirror, and after preparing a cold atom cluster at the first waist spot in the vacuum cavity, and before the step of using a Raman light pulse sequence to pass through the optical cavity and performing beam splitting, reflection, and beam combining interference operations on the cold atom cluster, the atomic interferometric gravity measurement method further includes:

[0013] Acquire cavity-locked light that is combined with the Raman light and resonates with the cavity field mode of the optical cavity, wherein the cavity-locked light adopts a frequency component of the Raman light or another beam of light far from the atomic resonance transition;

[0014] The cavity-locking light is introduced into the optical cavity, and the cavity-locking light signal transmitted through the third cavity mirror is measured.

[0015] The locked cavity optical signal is input to a modem for demodulation to obtain an error signal for locking the optical cavity length;

[0016] The error signal is amplified by a linear high-voltage amplifier, and the amplified error signal is loaded onto the piezoelectric ceramic disposed on the first cavity mirror. The piezoelectric ceramic drives the displacement of the first cavity mirror, thereby locking the cavity lengths of the first and third cavity mirrors.

[0017] In the step of obtaining the cavity-locked light that is combined with the Raman light and resonates with the cavity field mode of the optical cavity according to the above-described atomic interferometric gravity measurement method with optical cavity assistance, the cavity-locked light is combined with the Raman light through a polarizing beam splitter, and the frequency components of the cavity-locked light resonate with the cavity field mode of the optical cavity through modulation by an acousto-optic modulator.

[0018] According to the atomic interferometric gravity measurement method with optical cavity assistance described above, in the step of constructing the optical cavity, the first cavity mirror is a partially reflecting plane mirror, the second cavity mirror is an anti-reflection plano-convex lens, and the third cavity mirror is a high-reflection plano-convex lens or a high-reflection plane mirror.

[0019] The first cavity mirror has an anti-reflection coating on the side away from the optical cavity and a partial reflection coating on the side close to the optical cavity. The second cavity mirror has anti-reflection coatings on both sides. The third cavity mirror has an anti-reflection coating on the side away from the optical cavity and a high-reflection coating on the side close to the optical cavity.

[0020] According to the atomic interferometric gravity measurement method with optical cavity assistance described above, in the step of constructing the optical cavity, the cavity field direction of the optical cavity is parallel to the gravity direction.

[0021] According to the above-described atomic interferometric gravity measurement method with optical cavity assistance, the steps of using a Raman light pulse sequence to pass through the optical cavity and perform beam splitting, reflection, and beam combining interference operations on the cold atom cluster specifically include:

[0022] The laser generated by the first laser is expanded to obtain a beam-expanded beam that matches the first waist spot.

[0023] The expanded beam is polarized to obtain Raman light that matches the appropriate atomic transition energy levels;

[0024] A pulse sequence of Raman light is used to pass through the optical cavity and to perform interference operations such as beam splitting, reflection, and beam combining on the cold atom cluster.

[0025] The technical solution adopted in the second aspect of the embodiments of this application is:

[0026] An optical cavity-assisted atomic interferometric gravity measurement system is provided for implementing the optical cavity-assisted atomic interferometric gravity measurement method described above. The atomic interferometric gravity measurement system includes:

[0027] The first laser is used to generate Raman light;

[0028] An optical cavity is disposed on one side of the first laser. The optical cavity includes a first cavity mirror for coupling Raman light, a second cavity mirror for focusing Raman light, and a third cavity mirror for reflecting Raman light, which are spaced apart in sequence. There is a first waist spot between the first cavity mirror and the second cavity mirror, and a second waist spot is present at the position after focusing by the second cavity mirror. The second waist spot is used to detect the cavity field mode of the optical cavity through the transmitted light of the third cavity mirror. The first cavity mirror, the second cavity mirror, and the third cavity mirror are coaxial and form a standing wave circuit of the optical cavity. The cavity length of the optical cavity satisfies that the two frequency components of the Raman light resonate with the cavity field mode of the optical cavity simultaneously.

[0029] A vacuum chamber is disposed between the first cavity mirror and the second cavity mirror, and cold atomic clusters are prepared in the vacuum chamber at the first waist spot;

[0030] A detection device is disposed on one side of the vacuum cavity;

[0031] A timing control and data processing device, which is electrically connected to the first laser and the detection device.

[0032] According to the above-described atomic interferometric gravity measurement system with optical cavity assistance, the atomic interferometric gravity measurement system further includes:

[0033] A second laser is disposed on one side of the vacuum cavity;

[0034] A modem is disposed on one side of the second laser;

[0035] An acousto-optic modulator is disposed on one side of the modem;

[0036] A polarizing beam splitter is disposed on one side of the acousto-optic modulator;

[0037] A cavity-locking photodetector is disposed on the side of the third cavity mirror opposite to the optical cavity and is electrically connected to the modem;

[0038] A linear high-voltage amplifier is disposed on one side of the lock-cavity photodetector and electrically connected to the modem;

[0039] A piezoelectric ceramic is disposed on the first cavity mirror and electrically connected to the linear high-voltage amplifier.

[0040] According to the above-described atomic interferometric gravity measurement system with optical cavity assistance, the atomic interferometric gravity measurement system further includes:

[0041] A beam expander is disposed on one side of the polarizing beam splitter prism;

[0042] A reflector is disposed on one side of the beam expander;

[0043] A quarter-glass slide is disposed between the reflector and the first cavity mirror.

[0044] The beneficial effects of the atomic interferometric gravity measurement method and system with optical cavity assistance provided in this application are at least as follows:

[0045] Because this application constructs an optical cavity, the Raman light can benefit from the cavity enhancement effect of the optical cavity when performing beam splitting, reflection, and beam combining interference operations on cold atomic clusters in a vacuum cavity. This effectively reduces the laser power requirement for the Raman light, which is beneficial for achieving high momentum transfer beam splitting atomic interference. At the same time, the cavity length of the optical cavity in this application is specially set to ensure that the two frequency components of the Raman light resonate with the cavity field mode of the optical cavity simultaneously. This not only ensures that the Raman light can exist within the optical cavity, but also effectively filters out unnecessary components in the Raman light, reducing the systematic error of atomic interference phase measurement and improving measurement accuracy. Furthermore, since the three cavity mirrors (first cavity mirror, second cavity mirror, and third cavity mirror) in the optical cavity of this application are coaxial, the parallelism of the first cavity mirror and the third cavity mirror can be ensured. After the Raman light passes through the optical cavity of this application, it can be effectively aligned with the Raman light propagating in opposite directions, thereby achieving self-alignment. Attached Figure Description

[0046] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0047] Figure 1 A flowchart of an atomic interferometric gravity measurement method with optical cavity assistance provided for an embodiment of this application.

[0048] Figure 2 This is a schematic diagram of the optical cavity in an atomic interferometric gravity measurement device with optical cavity assistance, provided as an embodiment of this application.

[0049] Figure 3 This is a schematic diagram of an atomic interferometric gravity measurement device with optical cavity assistance, provided as an embodiment of this application.

[0050] The following are the labeling elements in the figure:

[0051] 11. Raman beam; 21. First cavity mirror; 22. Second cavity mirror; 23. Third cavity mirror; 3. Vacuum cavity; 31. Cold atom cluster; 4. Detection device; 5. Second laser; 51. Cavity-locked beam; 6. Acousto-optic demodulator; 7. Polarizing beam splitter prism; 8. Beam expander; 9. Reflector; 10. Quarter glass slide. Detailed Implementation

[0052] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0053] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it may be directly or indirectly located on that other component. When a component is referred to as "connected to" another component, it may be directly or indirectly connected to that other component. The terms "upper," "lower," "left," "right," "front," "rear," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate orientations or positions based on the accompanying drawings, and are for ease of description only, and should not be construed as limiting the technical solution. The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features. "A plurality" means two or more, unless otherwise explicitly defined.

[0054] In the field of atomic interferometry, particularly atomic gravimeters, as laboratory technology matures, experimental devices are inevitably moving towards commercialization and practical application. While maintaining their advantages of high precision and sensitivity, issues such as power consumption and robustness remain critical problems to be addressed. Simultaneously, with the emergence of high-momentum beam-splitting atomic interferometry schemes, achieving higher precision atomic interferometry requires laser power approaching or exceeding the watt level. This increased power consumption places stringent demands on laser performance and quality, further limiting the improvement of atomic interferometer accuracy. In short, both commercialization and continued precision improvements are constrained by the laser power consumption limitations of atomic interferometers.

[0055] Therefore, the first aspect of this application provides an atomic interferometric gravity measurement method with optical cavity assistance. This method includes constructing an optical cavity, wherein the optical cavity includes a first cavity mirror for coupling Raman light, a second cavity mirror for focusing Raman light, and a third cavity mirror for reflecting Raman light, spaced apart sequentially. A first waist spot exists between the first and second cavity mirrors, and a second waist spot exists at the position after focusing by the second cavity mirror. The second waist spot, through the transmitted light from the third cavity mirror, is used to detect the cavity field mode of the optical cavity. The first, second, and third cavity mirrors are coaxial. A standing wave circuit is formed in the optical cavity; a vacuum cavity is placed between the first cavity mirror and the second cavity mirror, and cold atom clusters are prepared in the vacuum cavity at the first waist spot; a pulse sequence of Raman light is passed through the optical cavity, and the cold atom clusters are subjected to interference operations of beam splitting, reflection, and beam combining, wherein the cavity length of the optical cavity satisfies that the two frequency components of the Raman light resonate with the cavity field mode of the optical cavity simultaneously; the atomic number distribution of the cold atom clusters after the interference operation is measured to obtain the interference phase information of the cold atom clusters; the interference phase information is processed to obtain the atomic interference gravity measurement results.

[0056] Because this application constructs an optical cavity, the Raman light can benefit from the cavity enhancement effect when performing beam splitting, reflection, and beam combining interference operations on cold atomic clusters within a vacuum cavity. This effectively reduces the laser power requirement for the Raman light, which is beneficial for achieving high momentum transfer beam splitting atomic interference. For example, with the optical cavity constructed in this application, the Raman light power can be set to 2 milliwatts to achieve beam splitting, reflection, and beam combining interference operations on atomic clusters. In contrast, the Raman light power required to be set to 40 milliwatts without an optical cavity can achieve high-quality, low-power atomic interference gravity measurement.

[0057] Specifically, the reflectivity of the first cavity mirror is The reflectivity of the third cavity mirror is After neglecting the losses of the second cavity mirror in the optical cavity and other losses such as the vacuum window of the vacuum cavity, the enhancement factor of the optical cavity can be expressed as: It can increase the power of Raman light within the optical cavity by a factor of G;

[0058] Meanwhile, the cavity length of the optical cavity in this application is specially set to ensure that the two frequency components of the Raman light resonate with the cavity field mode of the optical cavity at the same time. This not only ensures that the Raman light can exist in the optical cavity, but also effectively filters out unnecessary components in the Raman light, reduces the systematic error of atomic interference phase measurement, and improves measurement accuracy. Furthermore, since the three cavity mirrors (first cavity mirror, second cavity mirror, and third cavity mirror) in the optical cavity of this application are coaxial, the parallelism of the first cavity mirror and the third cavity mirror can be ensured. After the Raman light passes through the optical cavity of this application, it can be effectively aligned with the Raman light propagating in opposite directions, thereby achieving self-alignment.

[0059] See Figure 1 In one embodiment, the atomic interferometric gravity measurement method with optical cavity assistance specifically includes:

[0060] S10. Construct an optical cavity, wherein the optical cavity includes a first cavity mirror for coupling Raman light, a second cavity mirror for focusing Raman light, and a third cavity mirror for reflecting Raman light, which are spaced apart in sequence. There is a first waist spot between the first cavity mirror and the second cavity mirror, and there is a second waist spot at the position after focusing by the second cavity mirror. The second waist spot is used to detect the cavity field mode of the optical cavity through the transmitted light of the third cavity mirror. The first cavity mirror, the second cavity mirror, and the third cavity mirror are coaxial and constitute the standing wave loop of the optical cavity.

[0061] Specifically, the first cavity mirror can be a partially reflective plane mirror, the second cavity mirror can be an anti-reflection plano-convex lens, and the third cavity mirror can be a high-reflection plano-convex lens or a high-reflection plane mirror. The side of the first cavity mirror facing away from the optical cavity is coated with an anti-reflection film, and the side of the first cavity mirror close to the optical cavity is coated with a partially reflective film. Both sides of the second cavity mirror are coated with anti-reflection films, and the side of the third cavity mirror facing away from the optical cavity is coated with an anti-reflection film, while the side close to the optical cavity is coated with a high-reflection film.

[0062] Wherein, the cavity membrane between the first cavity mirror and the second cavity mirror is a quasi-parallel light field, the first waist spot is larger than the second waist spot, the vacuum cavity and the cold atom cluster are located near the first waist spot, and the second waist spot exists outside the optical cavity, that is, on the side of the third cavity mirror away from the optical cavity.

[0063] Optional, see below Figure 2 and Figure 3 In one embodiment, the cavity field direction of the optical cavity is parallel to the direction of gravity g. Through the above setting, this embodiment ensures that the direction of free fall of the cold atomic clusters participating in atomic interference is consistent with the direction of the standing wave field under the action of gravity, thereby achieving a longer interval time of Raman pulse atomic interference and obtaining accurate and sensitive gravity (acceleration) measurement.

[0064] S20. A vacuum chamber is placed between the first cavity mirror and the second cavity mirror, and cold atomic clusters are prepared in the vacuum chamber at the first waist spot.

[0065] Specifically, the vacuum cavity can be cut from titanium alloy and a vacuum window for Raman light to pass through is installed along the cavity field direction of the optical cavity. The inner and outer surfaces of the vacuum window are coated with antireflection films. Ultra-high vacuum is drawn into the vacuum cavity and the vacuum degree is maintained by an ion pump. A rarefied atomic gas for atomic interference is present in the vacuum cavity. The rarefied atomic gas is cooled and trapped by the magneto-optical trap and used to prepare cold atomic clusters for atomic interference. The cold atomic clusters are completely covered by the first waist spot.

[0066] S30. A pulse sequence of Raman light is passed through the optical cavity to perform interference operations such as beam splitting, reflection, and beam combining on the cold atom cluster, wherein the cavity length of the optical cavity satisfies the condition that both frequency components of the Raman light resonate with the cavity field mode of the optical cavity simultaneously.

[0067] Specifically, the wavelength of the optical cavity is the distance between the first cavity mirror and the third cavity mirror. The Raman light consists of two frequency components, which can be composed of phase-stabilized laser beams from two first lasers or frequency-shifted laser beams from one first laser. The Raman light couples the atomic ground state energy level in a pulse sequence manner to realize the interference operation of beam splitting, reflection, and beam combining of atomic matter waves. The first laser emits three Raman pulses in a specific time sequence, referred to as the first Raman pulse, the second Raman pulse, and the third Raman pulse for ease of description. The first Raman pulse is used to perform beam-splitting interference on the cold atom cluster, the second Raman pulse is used to perform reflection interference on the cold atom cluster, and the third Raman pulse is used to perform beam-combining interference on the cold atom cluster. The time interval between the first and second Raman pulses is the same as the time interval between the second and third Raman pulses. After the third Raman pulse performs beam-combining interference on the cold atom cluster, the atomic number distribution of the cold atom cluster is measured.

[0068] Optionally, in one embodiment, the steps of using a pulse sequence of Raman light to pass through the optical cavity and perform interference operations such as beam splitting, reflection, and beam combining on the cold atom cluster specifically include:

[0069] S301. The laser generated by the first laser is expanded to obtain a beam-expanded light whose spot matches the first waist spot.

[0070] S302. The expanded beam is polarized to obtain Raman light that matches the appropriate atomic transition energy levels;

[0071] S303. A pulse sequence of Raman light is passed through the optical cavity to perform interference operations such as beam splitting, reflection, and beam combining on the cold atom cluster.

[0072] Specifically, before the Raman light enters the optical cavity, the laser generated by the first laser is first expanded by a beam expander so that the laser spot matches the first waist spot to obtain expanded light. In order to select and match suitable atomic transition energy levels, the polarization of the expanded light can be adjusted to circular polarization by a quarter glass plate and / or a half glass plate to obtain Raman light.

[0073] S40. Measure the atomic number distribution of the cold atom cluster after the interference operation to obtain the interference phase information of the cold atom cluster.

[0074] Specifically, the atomic number distribution of cold atom clusters after interference can be measured using a detection device. This detection device can be a fluorescence detection device or an imaging detection device. Once the atomic number distribution of the cold atom clusters after interference is measured, the interference phase information of the cold atom clusters can be obtained.

[0075] S50. The interference phase information is processed to obtain the atomic interference gravity measurement result.

[0076] Specifically, the timing control and data processing device can process the interference phase information and finally output the atomic interference gravity measurement results. In addition, the timing control and data processing device is also used to generate analog and digital signals to control the normal operation of other modules.

[0077] Optionally, in one embodiment, after the step of placing a vacuum cavity between the first cavity mirror and the second cavity mirror, and after preparing cold atom clusters at the first waist spot in the vacuum cavity, and before the step of using a Raman light pulse sequence to pass through the optical cavity and perform beam splitting, reflection, and beam combining interference operations on the cold atom clusters, the atomic interferometric gravity measurement method further includes:

[0078] Acquire cavity-locked light that is combined with the Raman beam and resonates with the cavity field mode of the optical cavity;

[0079] The cavity-locking light is introduced into the optical cavity, and the cavity-locking light signal transmitted through the third cavity mirror is measured.

[0080] The locked cavity optical signal is input to a modem for demodulation to obtain an error signal for locking the optical cavity length;

[0081] The error signal is amplified by a linear high-voltage amplifier, and the amplified error signal is loaded onto the piezoelectric ceramic disposed on the first cavity mirror. The piezoelectric ceramic drives the displacement of the first cavity mirror, thereby locking the cavity lengths of the first and third cavity mirrors.

[0082] Specifically, the cavity-locking light uses a frequency component of Raman light or another beam of light far from the atomic resonance transition. It is generated by a second laser. In order to reduce the interaction with atoms and reduce the influence of the cavity-locking light on atoms, the cavity-locking light uses a large detuned optical field with a wavelength far from the atomic resonance transition line. Its optical power is much smaller than that of Raman light, and its interaction with atoms is negligible. The cavity-locking light can be turned on only for a short time before the Raman light is applied to the cold atom cluster to lock the optical cavity resonance. At other times, the cavity-locking light is turned off, and the displacement of the piezoelectric ceramic on the first cavity mirror is kept constant, thereby keeping the distance between the first cavity mirror and the third cavity mirror constant.

[0083] The locked cavity light is frequency-shifted and adjusted by an acousto-optic modulator to ensure that its frequency components resonate with the cavity field mode of the optical cavity. It is then combined with the Raman light by a polarization beam splitter. The locked cavity light follows the same path as the Raman light, thus enabling cavity length locking to ensure that the frequency components of the Raman light resonate with the cavity field mode of the optical cavity. After the locked cavity light enters the optical cavity, a locked cavity light detector outside the third cavity mirror measures the signal transmitted through it. The measured signal is then used by a modem to generate an error signal for cavity length locking. This error signal is fed back to the piezoelectric ceramic on the first cavity mirror, which drives the first cavity mirror to shift, thus locking the cavity lengths of the first and third cavity mirrors.

[0084] In addition, to reduce the phase interference of vibration noise on Raman pulse interferometry, ensure the stability and contrast of atomic interference fringes, and achieve sensitive atomic interference gravity measurement, the third cavity mirror can be placed on a vibration-damping platform to reduce vibration on the third cavity mirror, thereby better maintaining the distance between the first and third cavity mirrors. Of course, cavity-locking light can also be used in conjunction with this.

[0085] The second aspect of this application provides an atomic interferometric gravity measurement device with optical cavity assistance, see reference. Figure 2 and Figure 3 This system is used to implement the optical cavity-assisted atomic interferometry gravity measurement method described above. The atomic interferometry gravity measurement system includes a first laser (not shown in the figure), an optical cavity, a vacuum cavity 3, a detection device 4, and a timing control and data processing device (not shown in the figure). The first laser generates Raman light 11. The optical cavity is located on one side of the first laser and includes a first cavity mirror 21 for coupling Raman light 11, a second cavity mirror 22 for focusing Raman light 11, and a third cavity mirror 23 for reflecting Raman light 11, spaced apart sequentially. A first waist spot exists between the first cavity mirror 21 and the second cavity mirror 22. After being focused by the second cavity mirror 22... A second waist spot exists at the location, and the second waist spot is used to detect the cavity field mode of the optical cavity through the transmitted light of the third cavity mirror 23. The first cavity mirror 21, the second cavity mirror 22 and the third cavity mirror 23 are coaxial and form a standing wave circuit of the optical cavity. The cavity length of the optical cavity satisfies that the two frequency components of the Raman light 11 resonate with the cavity field mode of the optical cavity at the same time. A vacuum cavity 3 is disposed between the first cavity mirror 21 and the second cavity mirror 22, and cold atom clusters 31 are prepared in the vacuum cavity 3 at the location of the first waist spot. A detection device 4 is disposed on one side of the vacuum cavity 3. A timing control and data processing device is electrically connected to the first laser and the detection device 4.

[0086] Optionally, in one embodiment, the first cavity mirror 21 can be a partially reflective plane mirror, the second cavity mirror 22 can be an anti-reflection plano-convex lens, and the third cavity mirror 23 can be a high-reflection plano-convex lens or a high-reflection plane mirror. The first cavity mirror 21 has an anti-reflection coating on the side facing away from the optical cavity and a partially reflective coating on the side facing away from the optical cavity. The second cavity mirror 22 has anti-reflection coatings on both sides, and the third cavity mirror 23 has an anti-reflection coating on the side facing away from the optical cavity and a high-reflection coating on the side facing away from the optical cavity.

[0087] Optional, see below Figure 2 and Figure 3 In one embodiment, the cavity membrane between the first cavity mirror 21 and the second cavity mirror 22 is a quasi-parallel optical field, and the cavity field direction of the optical cavity is parallel to the direction of gravity g.

[0088] Optionally, in one embodiment, the vacuum cavity 3 can be configured as a titanium alloy vacuum cavity 3, and the vacuum cavity 3 is equipped with a vacuum window for Raman light 11 to pass through along the cavity field direction of the optical cavity, and the inner and outer surfaces of the vacuum window are coated with an anti-reflection film.

[0089] Optional, see below Figure 3 In one embodiment, the atomic interferometric gravity measurement system further includes a second laser 5, a modem (not shown), an acousto-optic demodulator 6, a polarizing beam splitter 7, a cavity-locked optical detector 51 (not shown), a linear high-voltage amplifier (not shown), and a piezoelectric ceramic (not shown). The second laser 5 is disposed on one side of the vacuum cavity 3, the modem is disposed on one side of the second laser 5, the modem is disposed on one side of the modem, the polarizing beam splitter 7 is disposed on one side of the acousto-optic modulator, the cavity-locked optical detector 51 is disposed on the side of the third cavity mirror 23 opposite to the optical cavity and is electrically connected to the modem, the linear high-voltage amplifier is disposed on one side of the cavity-locked optical detector 51 and is electrically connected to the modem, and the piezoelectric ceramic is disposed on the first cavity mirror 21 and is electrically connected to the linear high-voltage amplifier.

[0090] Optional, see below Figure 3 In one embodiment, the atomic interferometric gravity measurement system further includes a beam expander 8, a reflector 9, and a quarter glass slide 10. The beam expander 8 is disposed on one side of the polarizing beam splitter prism 7, the reflector 9 is disposed on one side of the beam expander 8, and the quarter glass slide 10 is disposed between the reflector 9 and the first cavity mirror 21.

[0091] The working principle of the optical cavity-assisted atomic interferometry gravity measurement device is as follows: Raman light 11 consists of two frequency components. It first passes through a polarizing beam splitter prism 7, then through a beam expander 8, then through a reflector 9, and finally through a quarter-glass plate 10 for polarization. The reflector 9 is used to couple Raman light 11 into the optical cavity for enhancement. Finally, the Raman light 11 performs beam splitting, reflection, and beam combining operations on the cold atom cluster 31. The atomic interferometry gravity measurement result is then obtained through a detection device 4 and a timing control and data processing device. In addition, to ensure the stability of the atomic interferometry of Raman light 11, this embodiment also generates cavity-locked light 51 through a second laser 5. The cavity-locked light 51 is combined with Raman light 11 through the polarizing beam splitter prism 7, so that the running path of the cavity-locked light 51 is consistent with that of Raman light 11, thereby locking the cavity length of the optical cavity (the distance between the first cavity mirror 21 and the third cavity mirror 23). To ensure that the cavity length of the optical cavity can simultaneously resonate with the cavity field mode of the optical cavity, the cavity-locked light 51 is first modulated by an acousto-optic modulator so that its frequency components resonate with the cavity field mode of the optical cavity, thus allowing it to enter the optical cavity. Then, it passes through a polarizing beam splitter 7 to combine with the Raman light 11. After passing through a beam expander 8, a reflector 9, and a quarter-glass slide 10 in sequence, it enters the optical cavity. When it reaches the third cavity mirror 23, the cavity-locked light 51 signal projected by the third cavity mirror 23 is measured by the cavity-locked light 51 detector and transmitted to the modem. The modem generates an error signal for locking the optical cavity length and feeds this error signal back to the piezoelectric ceramic set on the first cavity mirror 21, so that the piezoelectric ceramic drives the first cavity mirror 21 to move, thereby ensuring the stability of the distance (cavity length of the optical cavity) between the first cavity mirror 21 and the third cavity mirror 23.

[0092] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for measuring atomic interferometry gravity with optical cavity assistance, characterized in that, include: An optical cavity is constructed, wherein the optical cavity includes a first cavity mirror for coupling Raman light, a second cavity mirror for focusing Raman light, and a third cavity mirror for reflecting Raman light, which are spaced apart in sequence. There is a first waist spot between the first cavity mirror and the second cavity mirror, and there is a second waist spot at the position after focusing by the second cavity mirror. The second waist spot is used to detect the cavity field mode of the optical cavity through the transmitted light of the third cavity mirror. The first cavity mirror, the second cavity mirror, and the third cavity mirror are coaxial and form a standing wave loop of the optical cavity. A vacuum chamber is placed between the first cavity mirror and the second cavity mirror, and cold atomic clusters are prepared in the vacuum chamber at the first waist spot; A pulse sequence of Raman light is passed through the optical cavity, and interference operations such as beam splitting, reflection, and beam combining are performed on the cold atom cluster. The cavity length of the optical cavity satisfies the condition that both frequency components of the Raman light resonate with the cavity field mode of the optical cavity simultaneously. The number distribution of atoms in cold atom clusters after interferometry is measured to obtain the interference phase information of the cold atom clusters; The interference phase information is processed to obtain the atomic interference gravity measurement results.

2. The atomic interferometric gravity measurement method with optical cavity assistance according to claim 1, characterized in that, After the step of placing a vacuum cavity between the first cavity mirror and the second cavity mirror, and preparing cold atom clusters at the first waist spot in the vacuum cavity, and before the step of using a Raman light pulse sequence to pass through the optical cavity and performing beam splitting, reflection, and beam combining interference operations on the cold atom clusters, the atomic interferometric gravity measurement method further includes: Acquire cavity-locked light that is combined with the Raman light and resonates with the cavity field mode of the optical cavity, wherein the cavity-locked light adopts a frequency component of the Raman light or another beam of light far from the atomic resonance transition; The cavity-locking light is introduced into the optical cavity, and the cavity-locking light signal transmitted through the third cavity mirror is measured. The locked cavity optical signal is input to a modem for demodulation to obtain an error signal for locking the optical cavity length; The error signal is amplified by a linear high-voltage amplifier, and the amplified error signal is loaded onto the piezoelectric ceramic disposed on the first cavity mirror. The piezoelectric ceramic drives the displacement of the first cavity mirror, thereby locking the cavity lengths of the first and third cavity mirrors.

3. The atomic interferometric gravity measurement method with optical cavity assistance according to claim 2, characterized in that, In the step of obtaining cavity-locked light that is combined with the Raman light and resonates with the cavity field mode of the optical cavity, the cavity-locked light is combined with the Raman light through a polarizing beam splitter, and the frequency components of the cavity-locked light are made to resonate with the cavity field mode of the optical cavity through modulation by an acousto-optic modulator.

4. The atomic interferometric gravity measurement method with optical cavity assistance according to claim 1, characterized in that, In the step of constructing the optical cavity, the first cavity mirror is a partially reflective plane mirror, the second cavity mirror is an anti-reflection plano-convex lens, and the third cavity mirror is a high-reflection plano-convex lens or a high-reflection plane mirror. The first cavity mirror has an anti-reflection coating on the side away from the optical cavity and a partial reflection coating on the side close to the optical cavity. The second cavity mirror has anti-reflection coatings on both sides. The third cavity mirror has an anti-reflection coating on the side away from the optical cavity and a high-reflection coating on the side close to the optical cavity.

5. The atomic interferometric gravity measurement method with optical cavity assistance according to claim 1, characterized in that, In the step of constructing the optical cavity, the cavity field direction of the optical cavity is parallel to the direction of gravity.

6. The atomic interferometric gravity measurement method with optical cavity assistance according to claim 1, characterized in that, The steps of using a pulse sequence of Raman light to pass through the optical cavity and perform interference operations such as beam splitting, reflection, and beam combining on the cold atom cluster specifically include: The laser generated by the first laser is expanded to obtain a beam-expanded beam that matches the first waist spot. The expanded beam is polarized to obtain Raman light that matches the appropriate atomic transition energy levels; A pulse sequence of Raman light is used to pass through the optical cavity and to perform interference operations such as beam splitting, reflection, and beam combining on the cold atom cluster.

7. An atomic interferometric gravity measurement system with optical cavity assistance, characterized in that, It is used to implement the optical cavity-assisted atomic interferometric gravity measurement method as described in any one of claims 1-6, wherein the atomic interferometric gravity measurement system comprises: The first laser is used to generate Raman light; An optical cavity is disposed on one side of the first laser. The optical cavity includes a first cavity mirror for coupling Raman light, a second cavity mirror for focusing Raman light, and a third cavity mirror for reflecting Raman light, which are spaced apart in sequence. There is a first waist spot between the first cavity mirror and the second cavity mirror, and a second waist spot is present at the position after focusing by the second cavity mirror. The second waist spot is used to detect the cavity field mode of the optical cavity through the transmitted light of the third cavity mirror. The first cavity mirror, the second cavity mirror, and the third cavity mirror are coaxial and form a standing wave circuit of the optical cavity. The cavity length of the optical cavity satisfies that the two frequency components of the Raman light resonate with the cavity field mode of the optical cavity simultaneously. A vacuum chamber is disposed between the first cavity mirror and the second cavity mirror, and cold atomic clusters are prepared in the vacuum chamber at the first waist spot; A detection device is disposed on one side of the vacuum cavity; A timing control and data processing device, which is electrically connected to the first laser and the detection device.

8. The atomic interferometric gravity measurement system with optical cavity assistance according to claim 7, characterized in that, The atomic interferometric gravity measurement system also includes: A second laser is disposed on one side of the vacuum cavity; A modem is disposed on one side of the second laser; An acousto-optic modulator is disposed on one side of the modem; A polarizing beam splitter is disposed on one side of the acousto-optic modulator; A cavity-locking photodetector is disposed on the side of the third cavity mirror opposite to the optical cavity and is electrically connected to the modem; A linear high-voltage amplifier is disposed on one side of the lock-cavity photodetector and electrically connected to the modem; A piezoelectric ceramic is disposed on the first cavity mirror and electrically connected to the linear high-voltage amplifier.

9. The atomic interferometric gravity measurement system with optical cavity assistance according to claim 8, characterized in that, The atomic interferometric gravity measurement system also includes: A beam expander is disposed on one side of the polarizing beam splitter prism; A reflector is disposed on one side of the beam expander; A quarter-glass slide is disposed between the reflector and the first cavity mirror.

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