Final state detection device for atom interferometer and detection method thereof

Abstract

The invention relates to a final state detection device for an atom interferometer and a detection method thereof. The device comprises a detection laser collimator, a first coupling lens, a resonant cavity, a second coupling lens, a photoelectric detector and a computing terminal, the resonant cavity comprises a first cavity mirror and a second cavity mirror which are located on the two sides of a vacuum cavity of the atom interferometer and are oppositely arranged. To-be-tested atomic groups in different test states are arranged in the vacuum cavity; in each test state, the detection laser collimator is used for outputting detection laser and enabling the detection laser to enter the vacuum cavity through the first coupling lens and the first cavity mirror, and the detection laser passes through an atomic group to be tested for many times and is coupled to the photoelectric detector through the second cavity mirror and the second coupling lens. Enabling a computing terminal to obtain the transmission light power of the detection laser in each test state through a photoelectric detector, so as to determine the atomic final state population information after the atomic interference; and the detection laser resonates with the transition spectral line of the atomic group to be detected. According to the invention, the measurement precision of the final-state atomic population information can be improved.

Description

Technical Field

[0001] The present application relates to the field of quantum precision measurement technology, and in particular to a final state detection device and a detection method thereof for an atom interferometer. Background Art

[0002] At present, the detection of the final state atomic population in the atom interferometer of the two-photon stimulated Raman transition technology mainly adopts the fluorescence detection method and the absorption detection method. A beam of detection laser with a frequency corresponding to the atomic energy level interacts with the atom to collect the fluorescence signal of the atom and obtain the population information. When collecting the fluorescence signal, the fluorescence of a part of the solid angle is generally collected through the lens and the photodetector. This collection method has low efficiency and weak signal intensity, and is easily affected by stray light. Although the absorption detection method has a strong ability to resist stray light and has a high signal collection efficiency, the absorption signal is still weak, resulting in low measurement accuracy of the atomic population information of the final state. Summary of the invention

[0003] Based on the above description, the present application provides a final state detection device and method for an atom interferometer, which can increase the size of the atomic absorption signal, thereby improving the measurement accuracy of the final state atomic population information.

[0004] According to a first aspect, the present application provides a final state detection device for an atom interferometer, the atom interferometer comprising a vacuum cavity, the final state detection device comprising a detection laser collimator, a first coupling lens, a resonant cavity, a second coupling lens, a photodetector and a computing terminal; the resonant cavity comprises a first cavity mirror and a second cavity mirror located on both sides of the vacuum cavity and arranged oppositely; there are atomic groups to be tested in different test states in the vacuum cavity; In each test state, the detection laser collimator is used to output the detection laser, and the detection laser enters the vacuum cavity through the first coupling lens and the first cavity mirror. Under the reflection of the second cavity mirror and the first cavity mirror, the detection laser passes through the atomic group to be tested for multiple times, and is coupled to the photodetector through the second cavity mirror and the second coupling lens, so that the computing terminal obtains the transmitted light power of the detection laser in each test state through the photodetector to determine the atomic final state population information after atomic interference; The detection laser resonates with the transition spectrum line of the atomic group to be detected.

[0005] In some embodiments, the first cavity mirror, the first coupling lens and the detection laser collimator are sequentially arranged at intervals on one side of the vacuum cavity, and the second cavity mirror, the second coupling lens and the photodetector are sequentially arranged at intervals on the other side of the vacuum cavity.

[0006] In some embodiments, the atomic group to be measured has three test states, namely, a completely non-resonant ground state, a partially resonant ground state, and a completely resonant ground state; after atomic interference, the atomic group to be measured changes from the completely non-resonant ground state to the partially resonant ground state.

[0007] In some embodiments, a back-pump collimator is further included. The back-pump collimator is disposed outside the vacuum chamber and is used to output pump light toward the atomic group to be measured after atomic interference and laser detection to back-pump the atomic group to be measured to the full resonance ground state.

[0008] In some embodiments, the first cavity mirror is configured as a total reflection spherical mirror, and the second cavity mirror is configured as a low-transmittance reflection spherical mirror.

[0009] In some embodiments, the radius of curvature of the first cavity mirror is smaller than the radius of curvature of the second cavity mirror; and / or The first cavity mirror and the second cavity mirror form a double-concave confocal cavity.

[0010] In some embodiments, the detection laser output by the detection laser collimator passes through the first coupling lens and then deviates from the optical axis of the resonant cavity and is incident on the first cavity mirror in a direction parallel to the optical axis of the resonant cavity.

[0011] In some embodiments, the incident position of the detection laser on the first cavity mirror and the second cavity mirror is determined according to the following theoretical calculation formula:

[0012]

[0013] in, represents the vertical distance between the incident point of the detection laser on the first cavity mirror and the optical axis of the resonant cavity, represents the vertical distance between the incident point of the detection laser on the second cavity mirror for the first time and the optical axis of the resonant cavity, It represents the vertical distance between the incident point of the detection laser on the first cavity mirror after being reflected from the second cavity mirror and the optical axis of the resonant cavity, It represents the vertical distance between the incident point of the detection laser on the second cavity mirror after being reflected from the first cavity mirror and the optical axis of the resonant cavity, represents the focal length of the first cavity mirror, represents the focal length of the second cavity mirror, and The sum is equal to the cavity length of the resonant cavity, and The sum is equal to the detection width of the resonant cavity, The difference is equal to the beam width of the detection laser.

[0014] According to a second aspect, the present application provides a detection method for a final state detection device for an atom interferometer according to any one of the aforementioned embodiments, comprising: Installing and adjusting the position of the final state detection device outside the vacuum chamber of the atom interferometer; The atomic groups to be measured are prepared in a completely non-resonant ground state and arrive in the vacuum chamber, and the final state detection device is turned on to determine the first transmitted light power; After the atomic interference, the final state detection device is turned on to determine the second transmitted light power; After atomic interference and laser detection, the ground state of the atomic group to be detected is converted to a fully resonant ground state, and the final state detection device is turned on to determine the third transmitted light power; The atomic final state population information after atomic interference is calculated according to the first transmitted light power, the second transmitted light power and the third transmitted light power.

[0015] In some embodiments, the calculation formula of the atomic final state population information is as follows:

[0016] in, It indicates the number of particles in the non-resonant ground state in the atomic group to be measured after atomic interference. It indicates the number of particles in the resonant ground state in the atomic group to be measured after atomic interference. represents the first transmitted light power, represents the second transmitted light power, represents the third transmitted light power.

[0017] Compared with the prior art, the technical solution of this application has the following beneficial technical effects: In the above-mentioned final state detection device and detection method for the atom interferometer, the influence of stray light on the final state detection can be overcome by laser absorption detection. At the same time, an optical resonant cavity is introduced, which is equivalent to bending the light so that it can interact with the atomic group to be measured multiple times, thereby increasing the intensity of the absorption signal of the atomic group to be measured to the detection laser, facilitating the accurate detection of the transmitted light power of the detection laser, and by detecting the atomic group to be measured in different test states by the detection laser, the atomic final state population information after atomic interference can be accurately determined, thereby improving its measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of the principle of a final state detection device for an atom interferometer provided in an embodiment of the present application; Figure 2 is a schematic diagram of a resonant cavity in an embodiment of the present application; Figure 3A flow chart of a detection method for a final state detection device of an atom interferometer provided in an embodiment of the present application.

[0019] Description of reference numerals: Detection laser collimator 10; A first coupling lens 20; Resonant cavity 30, first cavity mirror 31, second cavity mirror 32; A second coupling lens 40; Photodetector 50; A computing terminal 60; Back pump collimator 70; Vacuum chamber Q; Detection laser s1; Pump light s2. DETAILED DESCRIPTION

[0020] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0022] Figure 1 FIG. 1 shows a schematic diagram of a final state detection device for an atom interferometer provided in an embodiment of the present application. The atom interferometer includes a vacuum cavity Q, Figure 1 The detection laser s1 in represents the total laser covering the atomic cluster to be measured, and the pump light s2 represents the total pump light covering the atomic cluster to be measured.

[0023] See also Figure 1, a final state detection device for an atom interferometer provided in one embodiment of the present application includes: a detection laser collimator 10, a first coupling lens 20, a resonant cavity 30, a second coupling lens 40, a photodetector 50 and a computing terminal 60. The resonant cavity 30 includes a first cavity mirror 31 and a second cavity mirror 32 located on both sides of the vacuum cavity Q and arranged opposite to each other. There are atomic groups to be tested in different test states in the vacuum cavity Q. In each test state, the detection laser collimator 10 is used to output a detection laser s1, and the detection laser s1 enters the vacuum cavity Q through the first coupling lens 20 and the first cavity mirror 31. Under the reflection of the second cavity mirror 32 and the first cavity mirror 31, the detection laser s1 passes through the atomic group to be tested for many times, and is coupled to the photodetector 50 through the second cavity mirror 32 and the second coupling lens 40, so that the computing terminal 60 obtains the transmitted light power of the detection laser s1 under each test state through the photodetector 50 to determine the atomic final state population information after atomic interference. The detection laser s1 resonates with the transition spectrum line of the atomic group to be tested.

[0024] It should be noted that the atom interferometer includes a vacuum cavity Q, which provides a high vacuum environment to prevent atomic interference from being disturbed. In this embodiment, the vacuum cavity Q can adopt a glass vacuum cavity, and the detection laser s1 can pass through the glass to enter the vacuum cavity Q; or a metal vacuum cavity is adopted, and the metal vacuum cavity is provided with a transparent glass window, and the detection laser s1 can pass through the transparent glass window to enter the vacuum cavity Q. By installing a final state detection device outside the vacuum cavity Q, the atomic group to be measured is located in the optical axis direction of the resonant cavity, which is used to determine the atomic final state distribution information. The detection laser collimator 10 is used to output the collimated detection laser s1. The first coupling lens 20, the first cavity mirror 31, the second cavity mirror 32, the second coupling lens 40 and the photodetector 50 are located on the optical path of the detection laser s1. The photodetector 50 is used to detect the transmitted laser signal.

[0025] The detection laser s1 resonates with the transition spectrum of the atomic group to be measured, that is, the wavelength of the detection laser s1 is the same as the wavelength of the transition spectrum of the atomic group to be measured. In this way, the atomic group to be measured can resonate with the detection laser s1 in the resonant ground state, absorb photons, and achieve energy level transition; the atomic group to be measured does not resonate with the detection laser s1 in the non-resonant ground state and cannot achieve energy level transition. In this embodiment, the atomic group to be measured can be atoms such as Rb, Cs, Na or Ca.

[0026] Specifically, in each test state, the ground state of the atomic cluster to be measured is different. The detection laser collimator 10 is used to output the detection laser s1. The detection laser s1 enters the vacuum cavity Q through the first coupling lens 20 and the first cavity mirror 31. Under the reflection of the second cavity mirror 32 and the first cavity mirror 31, the detection laser s1 passes through the atomic cluster to be measured many times. According to the ground state of the atomic cluster to be measured, the detection laser s1 resonates or does not resonate with the atomic cluster to be measured. Part or all of the detection laser s1 is transmitted through the second cavity mirror 32 and coupled to the receiving end of the photodetector 50 through the second coupling lens 40. The photodetector 50 converts the detected transmitted light signal into an electrical signal and transmits it to the computing terminal 60 (for example, a computer device), so that the computing terminal 60 obtains the transmitted light power of the detection laser s1 under each test state, thereby facilitating the determination of the atomic final state population information after atomic interference.

[0027] In this embodiment, the influence of stray light on final state detection can be overcome by means of laser absorption detection. At the same time, an optical resonant cavity 30 is introduced, which is equivalent to bending light so that it can interact with the atomic group to be measured multiple times, thereby improving the absorption rate of the atomic group to be measured to the detection laser s1 and the intensity of the absorption signal, facilitating accurate detection of the transmitted light power of the detection laser s1, and by repeatedly detecting the atomic group to be measured in different test states with the detection laser s1, the atomic final state population information can be accurately determined, thereby improving its measurement accuracy.

[0028] In some embodiments, the first cavity mirror 31, the first coupling lens 20 and the detection laser collimator 10 are sequentially arranged on one side of the vacuum cavity Q, and the second cavity mirror 32, the second coupling lens 40 and the photodetector 50 are sequentially arranged on the other side of the vacuum cavity Q.

[0029] Specifically, the first cavity mirror 31, the first coupling lens 20 and the detection laser collimator 10 are gradually spaced apart on one side of the vacuum cavity Q, and the second cavity mirror 32, the second coupling lens 40 and the photodetector 50 are gradually spaced apart on the other side of the vacuum cavity Q. In this way, the detection laser collimator 10 can complete the laser detection of the atomic group to be measured.

[0030] In some embodiments, the atomic group to be measured has three test states, namely, a completely non-resonant ground state, a partially resonant ground state, and a completely resonant ground state; after atomic interference, the atomic group to be measured changes from the completely non-resonant ground state to the partially resonant ground state.

[0031] It should be noted that only when the wavelength of the transition spectrum of the atomic group to be measured is equal to the wavelength of the detection laser s1, will the atomic group to be measured resonate with the detection laser s1 and absorb. For example, the atomic group to be measured uses 87Rb atoms. After atomic interference, the energy state of some atoms of 87Rb atoms is in F=1, and the energy state of the remaining atoms transitions to F=2. The wavelength of the detection laser s1 is selected to be 780.24nm, which corresponds to the wavelength of the transition spectrum of the 87Rb atoms from F=2 to F'=3. When the detection laser s1 with a wavelength of 780.24nm detects the 87Rb atoms after atomic interference, the atoms in F=2 resonate with the detection laser s1, and the atoms absorb photons to achieve transition from F=2 to F'=3. The energy state F'=3 is an unstable excited state, and the atoms will spontaneously fall back to the energy state of F=2 (F=3 does not exist in the ground state of 87Rb atoms). In this embodiment, in order to accurately test the atomic final state population information after atomic interference, it is necessary to perform background detection in advance, that is, prepare the atomic group to be measured in a completely non-resonant ground state and perform absorption signal detection to determine the transmitted light power of the detection laser under this test state; then perform atomic interference normally, and the energy state of the atomic group to be measured after atomic interference is a partially resonant ground state, and perform absorption signal detection through the final state device to determine the transmitted light power of the detection laser under this test state; furthermore, after atomic interference and laser detection, it is necessary to perform normalized detection, that is, transform the energy state of the atomic group to be measured to a completely resonant ground state, and perform absorption signal detection through the final state device to determine the transmitted light power of the detection laser under this test state. Through the detection results of these three stages, the transition probability of the atom in the atomic interference process can be solved, that is, the atomic final state population information can be obtained.

[0032] In some embodiments, the final state detection device of the embodiment of the present application also includes a back-pump collimator 70, which is arranged outside the vacuum cavity Q and is used to output collimated pump light s2 toward the atomic group to be measured after atomic interference and laser detection, so as to back-pump the atomic group to be measured to the full resonant ground state.

[0033] Specifically, the back-pump collimator 70 is installed outside the vacuum cavity Q, and is used to output the pump light s2. The pump light s2 passes through the vacuum cavity Q to pump all the atomic groups to be measured to the resonant ground state, that is, the entire resonant ground state. For example, after atomic interference and laser detection, the energy state of some atoms in the 87Rb atomic group is in F=1, and the energy state of some atoms is in F=2. In order to enable the absorption detection to determine the total number of all atoms, a beam of pump light s2 that resonates with the transition line from F=1 to F'=2 is used to excite all the atoms in the F=1 state to the F'=2 state. Since the energy state F'=2 is an unstable excited state, the atoms will spontaneously fall back to the energy state of F=1 or F=2, and the atoms that return to the F=1 state will be excited again by the pump light s2, thereby reciprocating so that all atoms are in the F=2 energy state that resonates with the detection laser s1, and the atomic groups to be measured in the entire resonant ground state are obtained. In this way, by setting the back pump collimator 70, after the atomic interference and laser detection, the test state of the atomic group to be measured is converted, which helps to determine the atomic final state population information after the atomic interference.

[0034] In some embodiments, the first cavity mirror 31 is configured as a total reflection spherical mirror, and the second cavity mirror 32 is configured as a low-transmittance reflection spherical mirror.

[0035] Specifically, by constructing the first cavity mirror 31 as a total reflection spherical mirror, that is, the first cavity mirror 31 is coated with a total reflection film on one side of the surface facing the resonant cavity 30. By constructing the second cavity mirror 32 as a low-transmittance reflection spherical mirror, that is, the second cavity mirror 32 is coated with a reflection film on one side of the surface facing the resonant cavity 30 and has a low transmittance, so that the resonant cavity 30 has a higher quality factor, a greater absorption signal amplification factor can be obtained. In this way, by constructing the first cavity mirror 31 as a total reflection spherical mirror and the second cavity mirror 32 as a low-transmittance reflection spherical mirror, most of the detection laser s1 can be reflected multiple times between the first cavity mirror 31 and the second cavity mirror 32, which can improve the absorption rate of the atomic group to be measured to the detection laser s1 and the intensity of the absorption signal, and a small part of the detection laser s1 is transmitted from the second cavity mirror 32, which is convenient for determining the transmission light power of the detection laser s1, which is beneficial to improving the measurement accuracy of the atomic final state population information.

[0036] In some embodiments, the radius of curvature of the first cavity mirror 31 is smaller than the radius of curvature of the second cavity mirror 32 .

[0037] Specifically, the focal length of the spherical mirror is equal to half of its radius of curvature. In the present embodiment, by setting the radius of curvature of the first cavity mirror 31 to be slightly smaller than the radius of curvature of the second cavity mirror 32, it is possible to ensure that the light beam of the detection laser s1 shrinks from the eccentric area of ​​the resonant cavity 30 toward the optical axis direction (i.e., the center) of the resonant cavity 30 as the number of reflections increases, so that the light can be stably reflected multiple times in the resonant cavity 30 and the attenuation of the absorption signal caused by saturated absorption is reduced.

[0038] Furthermore, the first cavity mirror 31 and the second cavity mirror 32 form a double concave confocal cavity. Specifically, the first cavity mirror 31 and the second cavity mirror 32 are set to form a double concave confocal cavity, that is, the first cavity mirror 31 and the second cavity mirror 32 are both concave mirrors and share a focus, and the sum of the focal length of the first cavity mirror 31 and the focal length of the second cavity mirror 32 is equal to the cavity length of the resonant cavity 30 (that is, the length of the resonant cavity 30 along the optical axis direction), and the first cavity mirror 31 can be fully reflected, and the second cavity mirror 32 can be low-transmittance reflection. In this way, the double concave confocal cavity can control the problem of light beam divergence during laser transmission, and at the same time ensure the parallelism of the outgoing light beam.

[0039] In some embodiments, the detection laser output by the detection laser collimator 10 passes through the first coupling lens 20 and then deviates from the optical axis of the resonant cavity 30 and is incident on the first cavity mirror 31 in a direction parallel to the optical axis of the resonant cavity 30 .

[0040] Specifically, the detection laser s1 collimated by the detection laser 10 and the first coupling lens 20 is parallel to the optical axis direction of the resonant cavity, and is incident on the first cavity mirror at a position deviated from the optical axis of the resonant cavity 30 by a certain distance, which can be regarded as eccentric incidence. In this way, under the reflection of the first cavity mirror 31 and the second cavity mirror 32, the light beam of the detection laser s1 can be gathered from the eccentric position of the resonant cavity 30 toward the center, so that the light is stably reflected multiple times in the resonant cavity 30 and passes through the atomic group to be measured.

[0041] like Figure 2 As shown, in some embodiments, the incident position of the detection laser s1 on the first cavity mirror 31 and the second cavity mirror 32 is determined according to the following theoretical calculation formula: (1) (2) in, represents the vertical distance between the incident point of the detection laser s1 on the first cavity mirror 31 and the optical axis of the resonant cavity 30 for the first time, represents the vertical distance between the incident point of the detection laser s1 on the second cavity mirror 32 for the first time and the optical axis of the resonant cavity 30, represents the vertical distance between the incident point of the detection laser s1 on the first cavity mirror 31 after being reflected from the second cavity mirror 32 and the optical axis of the resonant cavity 30, represents the vertical distance between the incident point of the detection laser s1 on the second cavity mirror 32 after being reflected from the first cavity mirror 31 and the optical axis of the resonant cavity 30, represents the focal length of the first cavity mirror 31, represents the focal length of the second cavity mirror 32, and The sum is equal to the cavity length of the resonant cavity 30, and The sum is equal to the detection width of the resonant cavity 30, The difference is equal to the beam width of the detection laser s1.

[0042] Substitute equation (1) into equation (2) and convert it to get: .

[0043] In a specific embodiment, the cavity length of the resonant cavity 30 is required to be about 100 mm, the detection width is about 10 mm, and the single beam width of the detection laser s1 is about 1 mm. + ≈100mm, + ≈10mm, - ≈1mm. In this embodiment, it can be set =6mm, =5mm, by ,have to =(5 / 6) 1 / 2 , in order to facilitate calculation and manufacturing, the value is taken nearby, which can be determined =6mm, =45mm, =50mm, then = =6mm×45 / 50=5.4mm, =4.95mm. In this way, the incident position of the detection laser s1 on the first cavity mirror 31 and the second cavity mirror 32 can be designed. For the convenience of explanation, Figure 2 The resonant cavity 30 shown is taken as an example of a two-dimensional case, and a similar design can be performed in a three-dimensional case so that the detection area covers the entire atomic group to be detected.

[0044] See also Figure 3 Based on the same inventive concept, an embodiment of the present application provides a detection method for a final state detection device for an atom interferometer according to any of the aforementioned embodiments, comprising the following steps: S10. Install and adjust the position of the final state detection device outside the vacuum cavity Q of the atom interferometer; S20, preparing the atomic groups to be measured in all non-resonant ground states and allowing them to reach the vacuum chamber Q, and starting a final state detection device to determine a first transmitted light power; S30, after the atomic interference, turning on the final state detection device to determine the second transmitted light power; S40, after the atomic interference and laser detection, converting the ground state of the atomic group to be measured to the full resonance ground state, and turning on the final state detection device to determine the third transmitted light power; S50, calculating atomic final state population information after atomic interference according to the first transmitted light power, the second transmitted light power and the third transmitted light power.

[0045] Specifically, outside the vacuum cavity Q of the atom interferometer, the position of the final state detection device is installed and adjusted so that the atomic group to be measured can be located in the optical axis direction of the resonant cavity 30. In order to accurately test the atomic final state population information after atomic interference, it is necessary to perform background detection in advance, prepare the atomic group to be measured in all non-resonant ground states and arrive in the vacuum cavity Q, and detect the absorption signal of the atomic group to be measured through the final state detection device to determine the first transmitted light power. At this stage, the detection laser does not resonate with the atomic group to be measured, so the transmitted light signal is the strongest and the first transmitted light power is the largest. After the atom interferometer completes the atomic interference normally, the final state detection device is turned on, and the absorption signal of the atomic group to be measured is detected through the final state detection device. At this stage, some atoms resonate with the detection laser and generate absorption signals. The strength of the absorption signal is linearly related to the number of particles that resonate. The second transmitted light power is tested to reflect the absorption of the laser by some resonant ground state atoms. Finally, normalized detection is required. After atomic interference and laser detection, the ground state of the atomic group to be tested is converted to the fully resonant ground state, and the final state detection device is turned on to determine the third transmitted light power. At this stage, all atoms can resonate with the detection laser, and the absorption signal generated is the strongest. The third transmitted light power is tested to reflect the laser absorption of all resonant ground state atoms. Finally, the ratio of the number of ground state particles that resonate after atomic interference to the number of all ground state particles is calculated through the first transmitted light power, the second transmitted light power, and the third transmitted light power, that is, the atomic final state population information.

[0046] During each laser detection, the light is parallel to the optical axis direction of the resonant cavity 30 and deviates from the optical axis direction of the resonant cavity 30 to enter the first cavity mirror 31, and reaches the second cavity mirror 32 along the direction parallel to the optical axis of the resonant cavity 30. The light reflected by the second cavity mirror 32 will pass through the focus, and the light passing through the focus will be incident on the first cavity mirror 31, and reflected by the first cavity mirror 31, and the reflected light will reach the second cavity mirror 32 along the direction parallel to the optical axis. Therefore, all the light incident on the second cavity mirror 32 and transmitted from the second cavity mirror 32 will be parallel, so that the light can stably propagate multiple times in the resonant cavity 30, and focus from the eccentric area of ​​the resonant cavity 30 to the optical axis area, so that each time the light is emitted from the first cavity mirror 31 to the second cavity mirror 32 along the optical axis, it is absorbed by an atom once, and then after a part of the laser is transmitted by the second cavity mirror 32, the other part of the laser is reflected by the first cavity mirror 31 and absorbed by the atom again. All transmitted light is emitted in parallel with the optical axis direction of the resonant cavity 30 , is collected by the second coupling lens 40 and enters the photodetector 50 , and the corresponding transmitted light power is determined by the calculation terminal 60 .

[0047] In a specific embodiment, the atomic group to be measured is 87Rb atoms. After interference by the atomic interferometer, its energy state is at F=1 or F=2. The particle numbers are recorded as N1 and N2 respectively. The ratio of N2 to all particle numbers is the atomic transition probability, that is, the atomic final state population information. The wavelength of the detection laser s1 used is selected to be 780.24nm, corresponding to the transition spectrum line of the 87Rb atom from F=2 to F'=3. The detection laser s1 is absorbed when passing through the 87Rb atom, and the absorption rate is related to the action distance and the particle number density. According to Einstein's radiation absorption theory, the absorption rate , when the light intensity is weak, , I represents the intensity of the detection laser s1, represents the ground state particle number density of resonance, h is Planck's constant, ν represents the frequency of the detection laser s1, c represents the speed of light, B12 is the Einstein coefficient, It is only related to the atomic transition spectral lines and is linearly related to the number density of the resonant ground state particles.

[0048] Since the light in the middle of the resonant cavity 30 is dense, saturation absorption may occur. ,in, is the saturation intensity, which is an inherent property of atoms. In this case, the saturation absorption rate decreases with the increase of light intensity, but it is similar to the small signal absorption rate. It is proportional to the particle number density, so the atomic final state internal state population information can be expressed by the absorption rate. During detection, when the intensity of the detection laser s1 is not changed and the detection intensity is small, the absorption rate can be approximately expressed as . is the incident light power (i.e. the power of the detection laser), is the transmitted light power, and d represents the effective distance between the detection laser s1 and the atom.

[0049] When the transmittance is Tr and the absorption rate of the atomic group to be measured to the detection laser is α, all the transmitted light satisfy: ,exist , when Tr=0.1%, only considering the small signal absorption, the resonant cavity 30 amplifies the absorption signal by 2000 times, increasing the intensity of the absorption signal of the atom to the detection laser. However, due to the saturation absorption effect, the actual signal amplification factor will decrease.

[0050] From the approximate expression of the absorptivity, we can know that the absorptivity can be defined according to the transmitted light power. Combined with the linear correlation between the absorptivity and the ground state particle number density (equivalent to the number of particles) of the resonance, we can explain that the ground state particle number density of the resonance is linearly related to the transmitted light power. Therefore, by testing the absorption detection of the detection laser by atoms in different ground states, the corresponding transmitted light power can be determined, so as to calculate the ratio of the number of ground state particles of the resonance to the total number of ground state particles (i.e., the population information).

[0051] In some embodiments, the calculation formula for the atomic final state population information is as follows:

[0052] in, It indicates the number of particles in the non-resonant ground state in the atomic group to be measured after atomic interference. It indicates the number of particles in the resonant ground state in the atomic group to be measured after atomic interference. represents the first transmitted light power, represents the second transmitted light power, represents the third transmitted light power.

[0053] To summarize, the detection laser collimator 10 outputs the detection laser s1, which enters the resonant cavity 30 through the first coupling lens 20, and the detection laser s1 resonates with the atomic group to be measured in a specific transition; the curvature radius of the first cavity mirror 31 is smaller than the curvature radius of the second cavity mirror 32, and the first cavity mirror 31 is a total reflection spherical mirror, so that the detection light shrinks from the eccentric area of ​​the cavity to the center; the second cavity mirror 32 is a low-transmittance reflection spherical mirror, so that the optical resonant cavity 30 has a higher quality factor and can obtain a larger absorption signal amplification factor; the second coupling lens 40 collects the transmitted light emitted by the second cavity mirror 32 to the photodetector 50 for detection.

[0054] When the detection laser s1 passes through the atomic group to be measured, the detection laser s1 resonates or does not resonate with the atomic group to be measured, depending on the ground state of the atomic group to be measured. A small part of the detection laser s1 is transmitted through the second cavity mirror 32 and collected by the second coupling lens 40 into the photodetector 50, and most of the detection laser s1 is reflected. The reflected detection laser s1 resonates or does not resonate when passing through the atomic group to be measured, and then reflects through the first cavity mirror 31, and repeats the above process at a position closer to the center of the resonant cavity 30 until almost all the detection laser s1 is absorbed and transmitted. The photodetector 50 collects all the transmitted light. In this way, the transmission light power of all the atomic groups to be measured in the ground state that does not resonate with the laser can be detected in advance, and after atomic interference, the transmission light power of part of the atomic groups to be measured in the ground state that resonates with the laser can be detected, and then normalized detection can be performed to detect the transmission light power of all the atomic groups to be measured in the ground state that resonates with the laser, so that the atomic transition probability after atomic interference can be solved, that is, the atomic final state population information can be obtained.

[0055] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A final state detection device for an atom interferometer, characterized in that: The atom interferometer comprises a vacuum cavity, the final state detection device comprises a detection laser collimator, a first coupling lens, a resonant cavity, a second coupling lens, a photodetector and a computing terminal; the resonant cavity comprises a first cavity mirror and a second cavity mirror located on both sides of the vacuum cavity and arranged oppositely; there are atomic groups to be tested in different test states in the vacuum cavity; In each test state, the detection laser collimator is used to output the detection laser, and the detection laser enters the vacuum cavity through the first coupling lens and the first cavity mirror. Under the reflection of the second cavity mirror and the first cavity mirror, the detection laser passes through the atomic group to be tested for multiple times, and is coupled to the photodetector through the second cavity mirror and the second coupling lens, so that the computing terminal obtains the transmitted light power of the detection laser in each test state through the photodetector to determine the atomic final state population information after atomic interference; The detection laser resonates with the transition spectrum line of the atomic group to be detected.

2. The final state detection device for an atom interferometer according to claim 1, characterized in that: The first cavity mirror, the first coupling lens and the detection laser collimator are sequentially arranged at intervals on one side of the vacuum cavity, and the second cavity mirror, the second coupling lens and the photodetector are sequentially arranged at intervals on the other side of the vacuum cavity.

3. The final state detection device for an atom interferometer according to claim 1, characterized in that: The atomic group to be tested has three test states, namely, a completely non-resonant ground state, a partially resonant ground state and a completely resonant ground state; after atomic interference, the atomic group to be tested changes from the completely non-resonant ground state to the partially resonant ground state.

4. The final state detection device for an atom interferometer according to claim 3, characterized in that: It also includes a back-pump collimator, which is arranged outside the vacuum chamber and is used to output pump light toward the atomic group to be measured after atomic interference and laser detection, so as to back-pump the atomic group to be measured to the full resonance ground state.

5. The final state detection device for an atom interferometer according to any one of claims 1 to 4, characterized in that: The first cavity mirror is configured as a total reflection spherical mirror, and the second cavity mirror is configured as a low-transmittance reflection spherical mirror.

6. The final state detection device for an atom interferometer according to claim 5, characterized in that: The radius of curvature of the first cavity mirror is smaller than the radius of curvature of the second cavity mirror; and / or The first cavity mirror and the second cavity mirror form a double-concave confocal cavity.

7. The final state detection device for an atom interferometer according to any one of claims 1 to 4, characterized in that: The detection laser output by the detection laser collimator passes through the first coupling lens and then deviates from the optical axis of the resonant cavity and is incident on the first cavity mirror in a direction parallel to the optical axis of the resonant cavity.

8. The final state detection device for an atom interferometer according to any one of claims 1 to 4, characterized in that: The incident position of the detection laser on the first cavity mirror and the second cavity mirror is determined according to the following theoretical calculation formula: in, represents the vertical distance between the incident point of the detection laser on the first cavity mirror and the optical axis of the resonant cavity, represents the vertical distance between the incident point of the detection laser on the second cavity mirror for the first time and the optical axis of the resonant cavity, It represents the vertical distance between the incident point of the detection laser on the first cavity mirror after being reflected from the second cavity mirror and the optical axis of the resonant cavity, It represents the vertical distance between the incident point of the detection laser on the second cavity mirror after being reflected from the first cavity mirror and the optical axis of the resonant cavity, represents the focal length of the first cavity mirror, represents the focal length of the second cavity mirror, and The sum is equal to the cavity length of the resonant cavity, and The sum is equal to the detection width of the resonant cavity, The difference is equal to the beam width of the detection laser.

9. A detection method for a final state detection device for an atom interferometer according to any one of claims 1 to 8, characterized in that: include: Installing and adjusting the position of the final state detection device outside the vacuum chamber of the atom interferometer; The atomic groups to be measured are prepared in a completely non-resonant ground state and arrive in the vacuum chamber, and the final state detection device is turned on to determine the first transmitted light power; After the atomic interference, the final state detection device is turned on to determine the second transmitted light power; After atomic interference and laser detection, the ground state of the atomic group to be detected is converted to a fully resonant ground state, and the final state detection device is turned on to determine the third transmitted light power; The atomic final state population information after atomic interference is calculated according to the first transmitted light power, the second transmitted light power and the third transmitted light power.

10. The detection method of the final state detection device for an atom interferometer according to claim 9, characterized in that: The calculation formula of the atomic final state population information is as follows: in, It indicates the number of particles in the non-resonant ground state in the atomic group to be measured after atomic interference. It indicates the number of particles in the resonant ground state in the atomic group to be measured after atomic interference. represents the first transmitted light power, represents the second transmitted light power, represents the third transmitted light power.

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