Serf inertial measurement device based on optical cavity detection

Abstract

A SERF inertial measurement device based on optical cavity detection, by integrating an optical cavity in an alkali metal cell, the effective action distance of the detection laser and atoms in a small volume is improved, the strength of the system output signal is enhanced, the signal-to-noise ratio of the SERF inertial measurement device signal is improved, which is of great significance to the improvement of the sensitivity of the SERF inertial measurement device, characterized by comprising an alkali metal cell, a multi-pass reflection optical cavity structure is arranged in the alkali metal cell, the multi-pass reflection optical cavity structure comprises a first optical cavity mirror located on the incident side of the detection light and a second optical cavity mirror located on the emission side of the detection light, the detection light input interface of the first optical cavity mirror guides the detection light from outside the alkali metal cell to the reflection surface of the second optical cavity mirror, the detection light is reflected back and forth on the two reflection surfaces to form multi-pass reflection, and then exits from the detection light output interface of the second optical cavity mirror to outside the alkali metal cell.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of atomic spin inertial measurement, and in particular to a SERF inertial measurement device based on optical cavity detection, which improves the effective interaction distance of detection laser and atoms in a small volume by integrating an optical cavity in an alkali metal cell, enhances the output signal strength of the system, improves the signal-to-noise ratio of the SERF inertial measurement device signal, and is of great significance to the improvement of the sensitivity of the SERF inertial measurement device. BACKGROUND

[0002] The atomic spin inertial measurement device based on the Spin-Exchange-Relaxation-Free (SERF) effect amplifies the signal through the interaction between alkali metal atoms and inert gas atoms, realizes SERF inertial measurement, is one of the development directions of the next generation of ultra-high precision inertial measurement technology, and faces new physics research beyond the standard model, and the sensitivity determines the limit drift of the inertial device and the detection limit of the system.

[0003] The sensitivity of the SERF inertial measurement device is determined by the signal-to-noise ratio of the detection signal. As an optical detection system, improving the distance of light and atom interaction to improve the detection signal strength is one of the key technologies to improve the signal-to-noise ratio of the system. Without changing other parameters of the system, increasing the optical path of the detection light in the alkali metal cell can effectively improve the strength of the output optical signal of the system and increase the detection sensitivity of the SERF inertial measurement device.

[0004] At present, there is a method to improve the optical path of the detection light by placing a mirror outside the alkali metal cell. However, since the mirror is placed outside the alkali metal cell, the detection light will pass out of the cell multiple times during reflection, which will result in that the actual effective interaction distance of the detection light with the atoms cannot be greatly improved during multiple reflections, and the birefringence phenomenon caused by the cell glass will affect the polarization of the detection light, reducing the accuracy of the detection signal of the system. In addition, the current way to realize multiple reflection of detection light in the SERF inertial measurement device is to add two plane mirrors in the detection light path. This way cannot realize multiple reflections in a small volume of the alkali metal cell, and the ability to improve the sensitivity of the SERF inertial measurement device is limited. SUMMARY

[0005] The problem solved by the present application is to realize multiple reflections of detection light in a small volume by integrating an optical cavity in the alkali metal cell, improve the effective interaction distance of the detection light with the atoms in the alkali metal cell, improve the signal-to-noise ratio of the SERF inertial measurement device signal, and build a SERF inertial measurement device based on optical cavity detection.

[0006] The technical solution of the present application is as follows:

[0007] A SERF inertial measurement device based on optical cavity detection, comprising an alkali metal cell, characterized in that a multi-pass reflection optical cavity structure is arranged in the alkali metal cell, the multi-pass reflection optical cavity structure comprises a first optical cavity mirror located on the incident side of detection light and a second optical cavity mirror located on the exit side of detection light, the detection light input interface of the first optical cavity mirror guides the detection light from outside the alkali metal cell to the reflection surface of the second optical cavity mirror, and the detection light is reflected back and forth on the two reflection surfaces to form multi-pass reflection and then exits from the detection light output interface of the second optical cavity mirror to outside the alkali metal cell.

[0008] The optical cavity mirror is a spherical mirror, a cylindrical mirror or a plane mirror, the side of the optical cavity mirror has a positioning plane, and the detection light input interface and the detection light output interface are light transmission holes.

[0009] The multi-pass reflection optical cavity structure comprises a silicon wafer bottom surface combined with the bottom surface of the alkali metal cell by an anodic bonding method, and the first optical cavity mirror and the second optical cavity mirror are both fixed on the silicon wafer bottom surface by the anodic bonding method.

[0010] The alkali metal cell is located in a non-magnetic heating module, the non-magnetic heating module is located in a three-axis compensation coil, the three-axis compensation coil is located in a zinc-manganese ferrite, and the zinc-manganese ferrite is located in a permalloy magnetic shielding barrel.

[0011] The detection light incident side of the alkali metal cell is connected with a detection laser through a third mirror, a second mirror, a second 1 / 4 wave plate, a photoelastic modulator, a detection polarizer, a second light diaphragm, a third lens, a second lens and a fourth G-T prism in sequence, and the detection light exit side of the alkali metal cell is connected with an upper computer through a fourth mirror, a fifth mirror, a fourth lens, a detection polarizer, a second photodetector and a lock-in amplification module in sequence.

[0012] The signal received by the upper computer is:

[0013]

[0014] Wherein, S is the output signal of the system, K1 is the amplification multiple of the system to the optical rotation signal, θ is the optical rotation angle, n is the atomic number density in the cell, c is the speed of light, r e is the electron radius, f D1 is a constant representing the strength of the oscillator, l is the effective interaction length of the detection light and the atom, v is the frequency of the detection laser, v0 is the center frequency of the absorbed laser, Γ is the pressure broadening of the D1 line of the alkali metal atom, is the longitudinal polarizability of the electron, is the transverse relaxation rate of the electron, γ e is the electron gyromagnetic ratio, and Lz gamma is the gyromagnetic ratio of the nucleus, Omega n gamma is the gyromagnetic ratio of the nucleus, Omega y is the system input angular velocity.

[0015] The pumping light incident side of the alkali metal cell is connected with a pumping laser through a first mirror, a first 1 / 4 wave plate, a first diaphragm, a third Gartai prism, a second 1 / 2 wave plate, a second Gartai prism, a liquid crystal phase retarder, a first Gartai prism, a first 1 / 2 wave plate and a first lens in sequence, and the liquid crystal phase retarder is connected with the third Gartai prism through an optical power stabilizing module and a first photodetector in sequence.

[0016] The technical effect of the application is as follows: the SERF inertial measurement device based on optical cavity detection of the application improves the effective action distance of the detection laser and the atom in a small volume by integrating the optical cavity in the alkali metal cell, enhances the strength of the system output signal, and improves the signal-to-noise ratio of the SERF inertial measurement device signal, which is of great significance to the improvement of the sensitivity of the SERF inertial measurement device.

[0017] Compared with the prior art, the application has the following advantages:

[0018] (1) The multi-pass reflection optical cavity is integrated in the alkali metal cell, so that the propagation path of the detection light is inside the cell, reducing the influence of the detection light on the polarization of the detection light when passing through the cell back and forth, and on the other hand, improving the actual effective action distance of the detection light and the atom.

[0019] (2) Through the parameter design of the integrated optical cavity in the alkali metal cell, a large number of reflection times can be achieved in the small volume of the cell, improving the sensitivity limit that the system can reach, and being of great significance to the integration and miniaturization of the device. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 is a structural schematic diagram of the SERF inertial measurement device based on optical cavity detection of the application.

[0021] Figure 2 is Figure 1 is a structural schematic diagram of the alkali metal cell with an optical cavity in the application.

[0022] Figure 3 is Figure 1 is a structural schematic diagram of the optical cavity mirror in the alkali metal cell in the application.

[0023] The reference signs are explained as follows: A1-pumping laser; A2-first lens; A3-first 1 / 2 wave plate; A4-first Glan-Taylor prism; A5-liquid crystal phase retarder; A6-second Glan-Taylor prism; A7-second 1 / 2 wave plate; A8-third Glan-Taylor prism; A9-first diaphragm; A10-first 1 / 4 wave plate; A11-first mirror; A12-first photodetector; A13-optical power stabilization module; B1-detection laser; B2-fourth Glan-Taylor prism; B3-second lens; B4-third lens; B5-second diaphragm; B6-detection polarizer; B7-photoelastic modulator; B8-second 1 / 4 wave plate; B9-second mirror; B10-third mirror; B11-first cavity mirror; B12-second cavity mirror; B13-alkali metal cell; B14-fourth mirror; B15-fifth mirror; B16-fourth lens; B17-detection analyzer; B18-second photodetector; B19-phase-locked amplification module; B20-upper computer; B21-silicon wafer bottom surface; B22-cell glass; B23-light transmission hole; B24-positioning plane; B25-high-reflection dielectric film; C1-magnetic-free heating module; C2-three-axis compensation coil; C3-vacuum cavity; C4-zinc-manganese ferrite; C5-pomalloy magnetic shielding barrel. DETAILED DESCRIPTION

[0024] The application will be described in the following with reference to the drawings Figures 1-3 and examples.

[0025] Figure 1 is a structural schematic diagram of a SERF inertial measurement device based on optical cavity detection according to the application. Figure 2 is Figure 1 a structural schematic diagram of an alkali metal cell with an optical cavity in the application. Figure 3 is Figure 1 a structural schematic diagram of the optical cavity mirror structure in the alkali metal cell in the application. Referring to Figures 1 to 3 , a SERF inertial measurement device based on optical cavity detection includes an alkali metal cell B13, a multi-pass reflection optical cavity structure is arranged in the alkali metal cell B13, the multi-pass reflection optical cavity structure includes a first cavity mirror B11 on the incident side of detection light and a second cavity mirror B12 on the emission side of detection light, the detection light input interface of the first cavity mirror B11 guides the detection light from outside the alkali metal cell B13 to the reflection surface of the second cavity mirror B12, the detection light is reflected back and forth on the two reflection surfaces to form multi-pass reflection, and then is emitted from the detection light output interface of the second cavity mirror B12 to outside the alkali metal cell B13.

[0026] The optical cavity mirror is a spherical mirror, a cylindrical mirror or a plane mirror, a side of the optical cavity mirror has a positioning plane B24, the detection light input interface and the detection light output interface are both light transmission holes B23, and the optical cavity mirror is reflected by a high-reflection dielectric film B25. The multi-pass reflection optical cavity structure comprises a silicon wafer bottom surface B21 combined with a bottom surface of an alkali metal cell B13 in an anode bonding mode, and the first optical cavity mirror B11 and the second optical cavity mirror B12 are both fixed on the silicon wafer bottom surface B21 in the anode bonding mode.

[0027] The alkali metal cell B13 is located in a non-magnetic heating module C1, the non-magnetic heating module C1 is located in a three-axis compensation coil C2, the three-axis compensation coil C2 is located in a zinc-manganese ferrite C4, and the zinc-manganese ferrite C4 is located in a permalloy magnetic shielding barrel C5. The detection light incident side of the alkali metal cell B13 is connected to a detection laser B1 in sequence through a third mirror B10, a second mirror B9, a second 1 / 4 wave plate B8, a photoelastic modulator B7, a detection polarizer B6, a second diaphragm B5, a third lens B4, a second lens B3 and a fourth Gartai prism B2, and the detection light exit side of the alkali metal cell B13 is connected to an upper computer B20 in sequence through a fourth mirror B14, a fifth mirror B15, a fourth lens B16, a detection polarizer B17, a second photodetector B18 and a lock-in amplification module B19.

[0028] The signal received by the upper computer B20 is:

[0029]

[0030] Wherein, S is the output signal of the system, K1 is the amplification multiple of the system to the optical rotation signal, θ is the optical rotation angle, n is the atomic number density in the cell, c is the speed of light, r e is the electronic radius, f D1 is a constant representing the strength of the oscillator, l is the effective action length of the detection light and the atom, v is the detection laser frequency, v0 is the center frequency of the absorbed laser, Γ is the pressure broadening of the alkali metal atom D1 line, is the longitudinal polarizability of the electron, is the transverse relaxation rate of the electron, γ e is the electron gyromagnetic ratio, L z is the optical frequency shift, γ n is the gyromagnetic ratio of the nucleus, Ω y is the input angular velocity of the system.

[0031] The pumping light incident side of the alkali metal cell B13 is connected with the pumping laser A1 through the first mirror A11, the first 1 / 4 wave plate A10, the first diaphragm A9, the third Glan-Taylor prism A8, the second 1 / 2 wave plate A7, the second Glan-Taylor prism A6, the liquid crystal phase retarder A5, the first Glan-Taylor prism A4, the first 1 / 2 wave plate A3 and the first lens A2 in sequence, and the liquid crystal phase retarder A5 is connected with the third Glan-Taylor prism A8 through the optical power stabilization module A13 and the first photodetector A12 in sequence.

[0032] Reference Figure 1 , Figure 2 , Figure 3 As shown in the figure, a SERF inertial measurement device based on optical cavity detection includes an alkali metal cell B13, the alkali metal cell B13 has a multi-pass reflection optical cavity, a detection light incident side and a detection light exit side, the detection light incident side is connected with the third mirror B10, the detection light exit side is connected with the fourth mirror B14, and the multi-pass optical cavity reflects the received incident detection light multiple times inside the alkali metal cell B13 and then exits and reaches the fourth mirror B14 through the detection light exit side.

[0033] The multi-pass reflection optical cavity is bonded inside the alkali metal cell, and the inside contains the first optical cavity mirror B11 and the second optical cavity mirror B12, which can be spherical mirrors, cylindrical mirrors or plane mirrors, and the detection light exits after being reflected multiple times between the first optical cavity mirror B11 and the second optical cavity mirror B12.

[0034] The third mirror B10 is connected with the detection laser B1 through the second mirror B9, the second 1 / 4 wave plate B8, the photoelastic modulator B7, the detection polarizer B6, the second diaphragm B5, the third lens B4, the second lens B3 and the fourth Glan-Taylor prism B2 in sequence, the fourth mirror B14 is connected with the input end of the phase-locked amplification module B19 through the fifth mirror B15, the fourth lens B16, the detection analyzer B17 and the second photodetector B18 in sequence, and the output end of the phase-locked amplification module B19 is connected with the upper computer B20. The heating magnetic shielding system of the alkali metal cell B13 includes the non-magnetic heating module C1, the three-axis compensation coil C2, the vacuum cavity C3, the zinc-manganese ferrite C4 and the permalloy magnetic shielding barrel C5 in sequence.

[0035] The signal received by the upper computer is:

[0036]

[0037] Wherein, S is the output signal of the system, K1 is the amplification multiple of the system to the optical rotation signal, n is the atomic number density in the cell, c is the speed of light, r e is the electron radius, fD1 where l is the effective interaction length between the probe light and the atoms, v is the frequency of the probe laser, v0 is the center frequency of the absorption laser, and Γ is the pressure broadening of the D1 line of the alkali metal atom, where a is the longitudinal polarizability of the electron, where γ is the transverse relaxation rate of the electron, e where g is the gyromagnetic ratio of the electron, z where γ is the light frequency shift, n where g is the gyromagnetic ratio of the nucleus, y where Ω is the input angular velocity of the system. The signal S is proportional to l, so increasing the optical path can significantly increase the signal strength.

[0038] The signal-to-noise ratio of the system is:

[0039]

[0040] where S is the signal of the system, signal where S is the signal of the system, noise where S is the signal of the system. Therefore, under the condition that the system noise is constant, increasing the signal strength can improve the signal-to-noise ratio.

[0041] The detection laser is incident on the alkali metal cell B13, and after multiple reflections between the first optical cavity mirror B11 and the second optical cavity mirror B12 in the alkali metal cell, it is incident on the fourth mirror B14 and the subsequent optical path, thereby achieving multiple reflections in a small volume of the alkali metal cell. By adjusting the type of optical cavity mirror, the number of optical cavity mirrors, the distance between the first optical cavity mirror B11 and the second optical cavity mirror B12, the relative position between the first optical cavity mirror B11 and the second optical cavity mirror B12, the position and angle of the detection light incident on the alkali metal cell B13, the number of reflections in the small volume of the alkali metal cell can be achieved, and the strength of the output signal of the system can be significantly improved.

[0042] The first optical cavity mirror B11 and the second optical cavity mirror B12 are first strictly fixed on the silicon wafer B21 of the alkali metal cell by anode bonding, specifically, the first optical cavity mirror B11 and the second optical cavity mirror B12 are installed on the silicon wafer B21 by a special mold that can determine the relative position of the two, under high temperature, high voltage and certain pressure, irreversible bonding reaction occurs at the connection between the mirror glass and the silicon wafer, forming a firm silicon-oxygen bond, firmly fixing the mirror on the silicon wafer B21, and the silicon wafer B21 is then fixed together with the cell glass B22 by anode bonding, thereby integrating the optical cavity inside the alkali metal cell B13.

[0043] The first optical cavity mirror B11 and the second optical cavity mirror B12 are both cylinders with a positioning plane B24 and a light hole B23, the positioning plane B24 is used to determine the relative rotation angle of the two optical cavity mirrors during bonding, the detection light enters from the light hole B23 of the first optical cavity mirror B11, and exits from the light hole B23 of the second optical cavity mirror B12 after multiple reflections, the number of reflections of the detection light in the optical cavity is determined by the type, relative rotation angle, distance, focal length, detection light incident position and detection light incident angle of the two optical cavity mirrors, the position of the positioning plane B24 is determined by the relative rotation angle of the two optical cavity mirrors, and the position of the light hole B23 is determined by the detection light incident position.

[0044] The surfaces of the first optical cavity mirror B11 and the second optical cavity mirror B12 are coated with high-temperature-resistant high-reflection dielectric film B25, so as to ensure the reflection quality of the detection light, the first optical cavity mirror and the second optical cavity mirror can be spherical mirrors, cylindrical mirrors or plane mirrors, and the type of the optical cavity mirror determines the reflection mode and the upper limit of the number of reflections of the detection light in the optical cavity.

[0045] The contents not described in detail in the specification of the present application belong to the prior art known to those skilled in the art. It is indicated here that the above description is helpful for those skilled in the art to understand the present application, but does not limit the protection scope of the present application. Any implementation of equivalent replacement, modification, improvement and / or deletion of the above description without departing from the essential content of the present application falls within the protection scope of the present application.

Claims

1. A SERF inertial measurement unit based on optical cavity detection, comprising an alkali metal gas chamber, characterized in that, The alkali metal gas chamber is provided with a multi-path reflection optical cavity structure, which includes a first optical cavity reflector located on the incident side of the detection light and a second optical cavity reflector located on the exit side of the detection light. The detection light input interface of the first optical cavity reflector guides the detection light from outside the alkali metal gas chamber to the reflective surface of the second optical cavity reflector. The detection light is reflected back and forth on the two reflective surfaces to form multi-path reflection and then exits from the detection light output interface of the second optical cavity reflector to outside the alkali metal gas chamber.

2. The SERF inertial measurement device based on optical cavity detection according to claim 1, characterized in that, The optical cavity reflector is a spherical mirror, cylindrical mirror, or plane mirror. The side of the optical cavity reflector has a positioning plane. Both the detection light input interface and the detection light output interface are light-transmitting holes.

3. The SERF inertial measurement device based on optical cavity detection according to claim 1, characterized in that, The multi-path reflection optical cavity structure includes a silicon wafer bottom surface bonded to the bottom surface of the alkali metal gas chamber via anodizing. The first and second optical cavity reflectors are both fixed to the silicon wafer bottom surface via anodizing.

4. The SERF inertial measurement device based on optical cavity detection according to claim 1, characterized in that, The alkali metal gas chamber is located inside the non-magnetic heating module, the non-magnetic heating module is located inside the triaxial compensation coil, the triaxial compensation coil is located inside the zinc-manganese ferrite body, and the zinc-manganese ferrite body is located inside the permalloy magnetic shielding barrel.

5. The SERF inertial measurement device based on optical cavity detection according to claim 1, characterized in that, The detection light incident side of the alkali metal gas chamber is connected to the detection laser in sequence through a third reflecting mirror, a second reflecting mirror, a second 1 / 4 wave plate, a photoelastic modulator, a detection polarizer, a second aperture, a third lens, a second lens, and a fourth Glan-Taylor prism. The detection light emitting side of the alkali metal gas chamber is connected to the host computer in sequence through a fourth reflecting mirror, a fifth reflecting mirror, a fourth lens, a detection analyzer, a second photodetector, and a lock-in amplifier module.

6. The SERF inertial measurement device based on optical cavity detection according to claim 5, characterized in that, The signal received by the host computer is: Where S is the system's output signal, K1 is the system's amplification factor for the optical rotation signal, θ is the optical rotation angle, n is the atomic number density in the gas chamber, c is the speed of light, and r e f is the electron radius. D1 The constant characterizing the oscillator strength is: l is the effective interaction length between the detection light and atoms, v is the detection laser frequency, ν0 is the center frequency of the absorbed laser, and Γ is the pressure broadening of the D1 line of the alkali metal atom. The longitudinal polarizability of electrons. γ is the transverse relaxation rate of electrons. n L is the electron gyromagnetic ratio. z For optical frequency shift, γ n Ω is the gyromagnetic ratio of the nucleon. y Input angular velocity to the system.

7. The SERF inertial measurement device based on optical cavity detection according to claim 1, characterized in that, The pump light incident side of the alkali metal gas cell is connected to the pump laser in sequence through a first reflecting mirror, a first quarter wave plate, a first aperture, a third Glan Taylor prism, a second half wave plate, a second Glan Taylor prism, a liquid crystal phase delay unit, a first Glan Taylor prism, a first half wave plate, and a first lens. The liquid crystal phase delay unit is connected to the third Glan Taylor prism in sequence through an optical power stabilization module and a first photodetector.

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