A cruciform tube based alkali metal cell, method of manufacture and filling, and angular rate sensor

Abstract

The application discloses an alkali metal gas chamber based on a T-shaped tube or a cross tube, which takes the T-shaped tube or the cross tube as a carrier, is formed by filling the alkali metal atoms and inert gas into the T-shaped tube or the cross tube, and is provided with a fiber collimator in each port of the T-shaped tube or the cross tube, so that the incidence and emission of the light beam in the T-shaped tube or the cross tube and alignment are realized. While miniaturization of the gas chamber is realized, high air tightness, high surface shape precision and good gas chamber inner wall state can be ensured, and the release and filling of the alkali metal atoms and the inert gas in a vacuum environment are relatively easy. The application discloses a preparation and filling method of the alkali metal gas chamber and an angular rate sensor comprising the alkali metal gas chamber.

Description

Technical Field

[0001] This invention relates to angular rate sensing technology, and more particularly to an alkali metal gas chamber, a preparation and filling method, and an angular rate sensor. Background Technology

[0002] Navigation is a key technology providing position, velocity, and attitude information for maritime, land, air, and space applications. Inertial navigation, in particular, requires no external information and enables fully autonomous navigation of vehicles or equipment. It boasts advantages such as all-weather, all-day operation, strong anti-interference capabilities, good stealth, complete navigation information, and high data update rates, making it the most important means of acquiring motion information. The gyroscope, as the core sensitive component of the inertial navigation system, determines the overall performance of the system.

[0003] The development of quantum control technology has driven the development of atomic gyroscopes that achieve inertial measurement based on atomic spin. Traditional atomic spin gyroscopes suffer from problems such as large alkali metal gas chamber volume and complex fabrication. Furthermore, the pump and probe optical paths are spatially separated, and the use of spatial optical paths to achieve atomic polarization and gyroscopic effect detection within the gas chamber directly leads to the problems of system instability and low efficiency. Summary of the Invention

[0004] To address the shortcomings of the prior art, this invention provides an alkali metal gas chamber based on a T-shaped tube or a cross-shaped tube, which has advantages such as small size and simple preparation.

[0005] The present invention provides a method for preparing and filling the above-mentioned alkali metal gas chamber and an angular rate sensor based on the above-mentioned alkali metal gas chamber.

[0006] The technical problem to be solved by the present invention is achieved through the following technical solution:

[0007] An alkali metal gas chamber based on a T-tube includes a T-tube, a first fiber optic collimator, and a second fiber optic collimator. The T-tube comprises a first cylindrical tube and a conical tube, with the narrow end of the conical tube connected to the middle of the first cylindrical tube. The first and second fiber optic collimators are respectively sealed within the two side ends of the first cylindrical tube and are aligned with each other. The wide end of the conical tube is sealed, and the T-tube is filled with at least alkali metal atoms and an inert gas.

[0008] An alkali metal gas chamber based on a cross tube includes a cross tube and a first fiber collimator, a second fiber collimator, and a third fiber collimator. The cross tube comprises a first cylindrical tube, a second cylindrical tube, and a conical tube. One side port of the second cylindrical tube is connected to the middle of the first cylindrical tube, and the second cylindrical tube is perpendicular to the first cylindrical tube. The narrow port of the conical tube is connected to the middle of the first cylindrical tube. The first and second fiber collimators are respectively sealed in the two side ports of the first cylindrical tube, and the third fiber collimator is sealed in the other side port of the second cylindrical tube. The first and second fiber collimators are aligned with each other. The wide port of the conical tube is sealed. The cross tube is filled with at least alkali metal atoms and an inert gas.

[0009] Furthermore, the T-shaped tube or cross tube is also filled with at least one of a buffer gas and a quenching gas.

[0010] A method for preparing and filling an alkali metal gas chamber includes the following steps:

[0011] Step 100: Provide a T-shaped tube, the T-shaped tube comprising a first cylindrical tube and a conical tube, the narrow end of the conical tube being connected to the middle of the first cylindrical tube;

[0012] Step 200: Provide a first fiber collimator and a second fiber collimator, and seal the first fiber collimator and the second fiber collimator in the two side ports of the first cylindrical tube and align them with each other.

[0013] Step 300: At least alkali metal atoms and inert gas are filled into the T-shaped tube through the conical tube;

[0014] Step 400: Seal the wide end of the conical tube.

[0015] A method for preparing and filling an alkali metal gas chamber includes the following steps:

[0016] Step 100: Provide a cross tube, the cross tube including a first cylindrical tube, a second cylindrical tube and a conical tube, one side port of the second cylindrical tube is connected to the middle of the first cylindrical tube, and the second cylindrical tube is perpendicular to the first cylindrical tube, and the narrow port of the conical tube is connected to the middle of the first cylindrical tube.

[0017] Step 200: Provide a first fiber collimator, a second fiber collimator and a third fiber collimator, and seal the first fiber collimator and the second fiber collimator in the two side ports of the first cylindrical tube respectively and align them with each other, and seal the third fiber collimator in the other side port of the second cylindrical tube.

[0018] Step 300: At least alkali metal atoms and inert gas are filled into the T-shaped tube or cross tube through the conical tube;

[0019] Step 400: Seal the wide end of the conical tube.

[0020] Furthermore, in step 300, the step of filling the T-tube or cross-shaped tube with at least alkali metal atoms and inert gas through the conical tube is as follows:

[0021] Step 310: Place the T-shaped tube or cross tube into the sealed chamber;

[0022] Step 320: Evacuate the sealed chamber to create a vacuum environment;

[0023] Step 330: Inert gas is introduced into the sealed chamber, so that the inert gas fills the T-shaped tube or cross tube through the conical tube;

[0024] Step 340: Place the alkali metal element inside the conical tube;

[0025] Step 350: Heat the alkali metal element to vaporize and release alkali metal atoms, allowing the alkali metal atoms to fill the T-shaped tube or cross tube through the conical tube.

[0026] Furthermore, in step 330, at least one of a buffer gas and a quenching gas is introduced into the sealed chamber, so that at least one of the buffer gas and the quenching gas fills the T-shaped tube or the cross tube through the conical tube.

[0027] An angular rate sensor includes a pump source, a first 45° tilted fiber grating, a birefringent chirped helical fiber grating, a probe source, a second 45° tilted fiber grating, an optical fiber coupler, an alkali metal gas chamber, an optical fiber filter, a polarization analyzer, and a magnetic field generator. The pump source is connected to the first incident end of the optical fiber coupler via the first 45° tilted fiber grating and the birefringent chirped helical fiber grating in sequence. The probe source is connected to the second incident end of the optical fiber coupler via the second 45° tilted fiber grating. The first optical fiber collimator of the alkali metal gas chamber is connected to the exit end of the optical fiber coupler. The polarization analyzer is connected to the second optical fiber collimator of the alkali metal gas chamber via the optical fiber filter. The polarization direction of the first 45° tilted fiber grating is parallel to the major axis or minor axis of the birefringent chirped helical fiber grating. The magnetic field generator is disposed outside the alkali metal gas chamber.

[0028] An angular rate sensor includes a pump source, a first 45° tilted fiber grating, a birefringent chirped spiral fiber grating, a probe source, a second 45° tilted fiber grating, the aforementioned alkali metal gas cell, a polarization analyzer, and a magnetic field generator. The pump source is connected sequentially to a third fiber collimator of the alkali metal gas cell via the first 45° tilted fiber grating and the birefringent chirped spiral fiber grating. The probe source is connected to a first fiber collimator of the alkali metal gas cell via the second 45° tilted fiber grating. The polarization analyzer is connected to a second fiber collimator of the alkali metal gas cell. The polarization direction of the first 45° tilted fiber grating is parallel to the major or minor axis of the birefringent chirped spiral fiber grating. The magnetic field generator is disposed outside the alkali metal gas cell.

[0029] Furthermore, the angular rate sensor also includes a non-magnetic heating box and a magnetic shielding box. The non-magnetic heating box is located outside the alkali metal gas chamber, and the magnetic shielding box is located outside the magnetic field generator.

[0030] The present invention has the following beneficial effects: The alkali metal gas chamber of the present invention uses the T-shaped tube or cross tube as a carrier, and is formed by filling the T-shaped tube or cross tube with alkali metal atoms and inert gas. Fiber collimators are respectively set in each port of the T-shaped tube or cross tube for the entry, exit and alignment of the light beam in the T-shaped tube or cross tube. While realizing the miniaturization of the gas chamber, it can ensure high airtightness, high surface accuracy and good inner wall condition of the gas chamber, and make it easier to release and fill the alkali metal atoms and inert gas in a vacuum environment. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the alkali metal gas chamber based on a T-shaped tube provided by the present invention.

[0032] Figure 2 A flowchart illustrating the steps of the method for preparing and filling an alkali metal gas chamber provided by the present invention.

[0033] Figure 3 This is a flowchart of step 300 in the method for preparing and filling an alkali metal gas chamber provided by the present invention.

[0034] Figure 4 This is a schematic diagram of the structure of the apparatus for preparing and filling the alkali metal gas chamber provided by the present invention.

[0035] Figure 5 This is a schematic diagram of the angular rate sensor provided by the present invention.

[0036] Figure 6 A schematic diagram of the alkali metal gas chamber based on a cross tube provided by the present invention.

[0037] Figure 7 A flowchart illustrating the steps of another method for preparing and filling an alkali metal gas chamber provided by the present invention.

[0038] Figure 8 This is a flowchart of step 300 in another method for preparing and filling an alkali metal gas chamber provided by the present invention.

[0039] Figure 9 This is a schematic diagram of another preparation and filling device for the alkali metal gas chamber provided by the present invention.

[0040] Figure 10 This is a schematic diagram of another angular rate sensor provided by the present invention. Detailed Implementation

[0041] The present invention will now be described in detail with reference to the accompanying drawings and embodiments, examples of which are shown in the drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0042] In the description of this invention, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0043] Furthermore, the terms "first," "second," and "third" 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 indicated. Thus, a feature defined as "first," "second," or "third" may explicitly or implicitly include one or more of that feature. In the description of this invention, "multiple" means two or more, unless otherwise explicitly specified.

[0044] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," "fixing," and "setting," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0045] Example 1

[0046] like Figure 1 As shown, an alkali metal gas chamber based on a T-tube includes a T-tube 710a, a first optical fiber collimator 720, and a second optical fiber collimator 730. The T-tube 710a includes a first cylindrical tube 711 and a conical tube 712. The narrow port of the conical tube 712 is connected to the middle of the first cylindrical tube 711. The first optical fiber collimator 720 and the second optical fiber collimator 730 are respectively sealed in the two side ports of the first cylindrical tube 711, and the first optical fiber collimator 720 and the second optical fiber collimator 730 are aligned with each other. The wide port of the conical tube 712 is sealed. The T-tube 710a is filled with at least alkali metal atoms and an inert gas.

[0047] The alkali metal gas chamber of the present invention uses the T-shaped tube 710a as a carrier and is formed by filling the T-shaped tube 710a with alkali metal atoms and inert gas. The first fiber collimator 720 and the second fiber collimator 730 are respectively arranged in the opposite two ports of the first cylindrical tube 711 of the T-shaped tube 710a for the entry and exit and alignment of the light beam in the T-shaped tube 710a. While realizing the miniaturization of the gas chamber, it can ensure high airtightness, high surface accuracy and good inner wall condition of the gas chamber, and make it easier to release and fill the alkali metal atoms and inert gas in a vacuum environment.

[0048] In this embodiment, the conical tube 712 is perpendicular to the first cylindrical tube 711, and the narrow port of the conical tube 712 is connected to the center of the first cylindrical tube 711; the wide port of the conical tube 712 is used as the filling port for the alkali metal atoms and inert gas, and after the filling of the alkali metal atoms and inert gas is completed, it is sealed by melting to achieve a sealing setting.

[0049] Preferably, the first fiber collimator 720 and the second fiber collimator 730 are respectively bonded and fixed to the opposite two ends of the first cylindrical tube 711 by vacuum sealant, and the opposite two ends of the first cylindrical tube 711 are sealed to increase the airtightness of the T-shaped tube 710a.

[0050] In use, the first fiber collimator 720 is used for the incident pump light and probe light, and the second fiber collimator 730 is used for the outgoing pump light and probe light. The first fiber collimator 720 and the second fiber collimator 730 are aligned with each other. The pump light is circularly polarized, and the probe light is linearly polarized. The pump light excites the alkali metal atoms in the T-tube 710a to undergo electronic spin polarization. The alkali metal atoms induce nuclear spin polarization of the inert gas through a spin-exchange collision mechanism. Under a static magnetic field, the nuclear spin-polarized inert gas undergoes Larmor precession around the static magnetic field, and the precession frequency is related to the static magnetic field. When the angular rate sensor rotates around the static magnetic field along with the carrier, the precession frequency of the nuclear spin of the inert gas will drift. The amount of drift is the angular rate of the angular rate sensor. The drift of the precession frequency will cause the polarization plane of the probe light to rotate, thereby causing a change in the polarization state of the probe light. By analyzing the change in the polarization state of the probe light, the angular rate of the angular rate sensor can be calculated.

[0051] Preferably, the T-shaped tube 710a is further filled with at least one of a buffer gas (an inert gas without nuclear spin) and a quenching gas (a diatomic molecule).

[0052] The buffer gas is used to collide with the alkali metal atoms to reduce the collisions between the alkali metal atoms and the wall of the T-shaped tube 710a, thereby reducing the depolarization rate of the alkali metal atoms and reducing the photon energy required for polarization of the alkali metal atoms, thus increasing the polarizability of the alkali metal atoms. The quenching gas is used to absorb the spontaneously emitted resonant photons when the alkali metal atoms recover from the excited state to the ground state, so as to avoid the resonant photons causing other alkali metal atoms to jump back from the ground state to the excited state and cause depolarization, thereby reducing the depolarization rate of the alkali metal atoms.

[0053] The alkali metal atom may be, but is not limited to, cesium (Cs) or rubidium (Rb) atoms, and the inert gas may be, but is not limited to, xenon, neon, or helium. 3 The buffer gas may be, but is not limited to, helium (He), etc. 4 The quenching gas may be, but is not limited to, nitrogen, etc. (e.g., He).

[0054] Example 2

[0055] like Figure 2 As shown, a method for preparing and filling an alkali metal gas chamber is provided for preparing and filling the alkali metal gas chamber described in Example 1; the preparation and filling method includes the following steps:

[0056] Step 100: Provide a T-shaped tube 710a, the T-shaped tube 710a including a first cylindrical tube 711 and a conical tube 712, the narrow end of the conical tube 712 being connected to the middle of the first cylindrical tube 711.

[0057] In step 100, the T-shaped tube 710a is composed of the first cylindrical tube 711 and the conical tube 712. First, the first cylindrical tube 711 is placed and fixed on a three-dimensional displacement platform. Then, a CO2 laser output is used to align with the outer wall of the first cylindrical tube 711. Next, the three-dimensional displacement platform moves the first cylindrical tube 711 relative to the CO2 laser according to a preset motion trajectory, so that the CO2 laser ablates a circular hole on the outer wall of the first cylindrical tube 711 that is slightly larger than the narrow end of the conical tube 712. Then, the narrow end of the conical tube 712 is aligned with the circular hole ablated by the first cylindrical tube 711. Finally, a precision discharge system is used to discharge at the contact point between the conical tube 712 and the first cylindrical tube 711, so that the two are fused together to form the T-shaped tube 710a.

[0058] In this embodiment, the conical tube 712 is perpendicular to the first cylindrical tube 711.

[0059] Step 200: Provide a first fiber optic collimator 720 and a second fiber optic collimator 730, and seal the first fiber optic collimator 720 and the second fiber optic collimator 730 in the two side ports of the first cylindrical tube 711 and align them with each other.

[0060] In step 200, vacuum sealant is first applied to the outer surfaces of the first fiber optic collimator 720 and the second fiber optic collimator 730. Then, the first fiber optic collimator 720 and the second fiber optic collimator 730 are respectively inserted into the two side ports of the first cylindrical tube 711, so that the vacuum sealant on the outer surfaces of the first fiber optic collimator 720 and the second fiber optic collimator 730 adheres to the inner wall of the first cylindrical tube 711. Next, the vacuum sealant is applied again to the annular end faces of the two side ports of the first cylindrical tube 711, simultaneously adhering the vacuum sealant on the annular end faces of the first cylindrical tube 711 to the outer surfaces of the first fiber optic collimator 720 and the second fiber optic collimator 730, thus achieving adhesion between the first fiber optic collimator 720 and the second fiber optic collimator 730 and the first cylindrical tube 711. The process involves pre-fixing the first fiber optic collimator 720; then connecting its pigtail to a red laser pointer to direct a red laser beam into the first fiber optic collimator 720; observing the pigtail of the second fiber optic collimator 730 and adjusting its relative position to allow the red laser beam to exit from the pigtail of the second fiber optic collimator 730, thus completing the alignment of the first and second fiber optic collimators 720 and 730; finally, curing the vacuum sealant between the first and second fiber optic collimators 720 and the first cylindrical tube 711 to seal and fix them to the first cylindrical tube 711. The curing method of the vacuum sealant can be, but is not limited to, natural curing, light curing, or heat curing.

[0061] Step 300: At least alkali metal atoms and inert gas are filled into the T-shaped tube 710a through the conical tube 712.

[0062] In step 300, a preparation and filling device is used to fill the T-shaped tube 710a with the alkali metal gas and inert gas through the conical tube 712. For example... Figure 4 As shown, the preparation and filling device includes a sealed chamber 13, a three-dimensional displacement platform 14, a heating laser 15, an alkali metal element 16, a vacuum pump 17, a first gas cylinder 18 filled with inert gas, and a host computer 21. The three-dimensional displacement platform 14, the heating laser 15, and the alkali metal element 16 are all disposed inside the sealed chamber 13, while the vacuum pump 17, the first gas cylinder 18, and the host computer 21 are all disposed outside the sealed chamber 13. The vacuum pump 17 and the first gas cylinder 18 are connected to the sealed chamber 13 through pipelines, and the host computer 21 is connected to control the three-dimensional displacement platform 14 and the heating laser 15.

[0063] Preferably, the preparation and filling device further includes at least one of a second gas cylinder 19 filled with buffer gas and a third gas cylinder 20 filled with quenching gas, wherein the second gas cylinder 19 and the third gas cylinder 20 are both located outside the sealed chamber 13 and are connected to the sealed chamber 13 through pipelines.

[0064] In this embodiment, the laser heater is a CO2 laser.

[0065] Specifically, such as Figure 3 As shown, in step 300, the step of filling the T-shaped tube 710a with at least alkali metal atoms and inert gas through the conical tube 712 is as follows:

[0066] Step 310: Place the T-shaped tube 710a into the sealed chamber 13.

[0067] In step 310, the sealed chamber 13 is a vacuum glove box, which facilitates the placement of the T-shaped tube 710a by technicians outside the vacuum glove box.

[0068] Step 320: Evacuate the sealed chamber 13 to create a vacuum environment.

[0069] In step 330, the vacuum pump 17 is started to evacuate the sealed chamber 13 until the required vacuum level is reached, and then the evacuation is stopped.

[0070] Step 330: Inert gas is introduced into the sealed chamber 13, so that the inert gas fills the T-shaped tube 710a through the conical tube 712.

[0071] In step 330, the first gas cylinder 18 is opened, allowing the inert gas in the first gas cylinder 18 to fill the sealed chamber 13. Since the T-shaped tube 710a is connected to the sealed chamber 13 through the conical tube 712, the inert gas in the sealed chamber 13 will naturally fill the T-shaped tube 710a through the conical tube 712.

[0072] Preferably, in step 330, at least one of a buffer gas and a quenching gas is introduced into the sealed chamber 13, so that at least one of the buffer gas and the quenching gas fills the T-shaped tube 710a through the conical tube 712.

[0073] In step 330, the second gas cylinder 19 and / or the third gas cylinder 20 are opened, so that the buffer gas in the second gas cylinder 19 and / or the quenching gas filled in the third gas cylinder 20 fill the sealed chamber 13. Since the T-shaped tube 710a is connected to the sealed chamber 13 through the conical tube 712, the buffer gas and / or quenching gas in the sealed chamber 13 will naturally fill the T-shaped tube 710a through the conical tube 712.

[0074] In step 330, the outflow rates of the inert gas, buffer gas, and quenching gas can be controlled by a flow valve, thereby adjusting the mixing ratio between the inert gas, buffer gas, and quenching gas.

[0075] Step 340: Place the alkali metal element 16 into the conical tube 712.

[0076] In step 340, the vacuum chamber can be a vacuum glove box, so that after the technician has filled the inert gas, buffer gas and quenching gas, he can place the alkali metal element 16 in the vacuum chamber into the conical tube 712 of the T-shaped tube 710a.

[0077] Of course, a robotic arm can also be installed inside the vacuum glove box to automatically place the alkali metal element 16.

[0078] The alkali metal element 16 is spherical. The inner diameter of the conical tube 712 at its narrow end should be larger than the diameter of the alkali metal element 16 to prevent the alkali metal element 16 from falling into the first cylindrical tube 711. At the same time, the inner diameter of the conical tube 712 at its wide end should not be too small to ensure that the alkali metal element 16 can be placed in stably.

[0079] Step 350: The alkali metal element 16 is heated to vaporize and release alkali metal atoms, which then fill the T-shaped tube 710a through the conical tube 712.

[0080] In step 350, the host computer 21 first controls the three-dimensional displacement platform 14 to move the T-shaped tube 710a to align the alkali metal element 16 on the T-shaped tube 710a with the laser heater. Then, the host computer controls the laser heater to emit a high-power laser beam to the alkali metal element 16 to heat the alkali metal element 16 to its vaporization temperature. When the alkali metal element 16 vaporizes, it releases alkali metal atoms to the surroundings. The alkali metal atoms released downwards enter and fill the T-shaped tube 710a through the conical tube 712.

[0081] In step 350, the atomic density of the alkali metal 16 in the T-tube 710a can be adjusted by controlling the heating time of the laser heater on the alkali metal 16.

[0082] Step 400: Seal the wide end of the conical tube 712.

[0083] In step 400, after the alkali metal atoms are filled, the host computer 21 controls the three-dimensional displacement platform 14 to move the T-shaped tube 710a to align the outer wall of the conical tube 712 below the alkali metal element 16 with the laser heater. Then, the laser heater is controlled to emit a high-power laser beam to the conical tube 712 to heat it, causing it to melt at the heating point. The tube is then slowly stretched or rotated, and the diameter of the conical tube 712 at the melting point gradually decreases during the slow stretching or rotation process, thereby causing the conical tube 712 to break at the melting point and form a seal. Alternatively, clamps can be used to clamp and seal the conical tube 712 at the melting point before breaking it.

[0084] Example 3

[0085] like Figure 5 As shown, an angular rate sensor includes a pump source 1, a first 45° tilted fiber grating 2, a birefringent chirped helical fiber grating 3, a probe source 4, a second 45° tilted fiber grating 5, an optical fiber coupler 6, an alkali metal gas cell 7 as described in Embodiment 1, an optical fiber filter 8, a polarization analyzer 9, and a magnetic field generator 10. The pump source 1 is connected to the first incident end of the optical fiber coupler 6 sequentially through the first 45° tilted fiber grating 2 and the birefringent chirped helical fiber grating 3. The probe source 4 is connected to the second incident end of the optical fiber coupler 6 through the second 45° tilted fiber grating 5. The first optical fiber collimator 720 of the alkali metal gas cell 7 is connected to the output end of the optical fiber coupler 6. The polarization analyzer 9 is connected to the second optical fiber collimator 730 of the alkali metal gas cell 7 through the optical fiber filter 8. The polarization direction of the first 45° tilted fiber grating is parallel to the major axis or minor axis of the birefringent chirped helical fiber grating 3. The magnetic field generator 10 is disposed outside the alkali metal gas cell 7.

[0086] The angular rate sensor of the present invention uses the first 45° tilted fiber grating 2 and the birefringent chirped spiral fiber grating 3 as the pump optical path at the front end, and the second 45° tilted fiber grating 5 as the probe optical path. The pump light and probe light are mixed and coupled into the alkali metal gas chamber 7 through the fiber coupler 6. At the rear end, the fiber filter 8 is used as the output optical path to filter the pump light emitted from the alkali metal gas chamber 7, and only the probe light emitted from the alkali metal gas chamber 7 is provided to the polarization analyzer 9 for demodulation. The pump optical path, probe optical path and output optical path are all integrated on the optical fiber, which greatly improves the integration of the angular rate sensor and realizes the miniaturization of the angular rate sensor. Moreover, the optical fiber has the advantages of strong anti-electromagnetic interference capability, acid and alkali corrosion resistance, electrical insulation, high measurement accuracy, high reliability and long service life, and has a great competitive advantage in harsh environments such as strong electromagnetic interference.

[0087] The pump light source 1 emits pump light, which is converted into circularly polarized light after passing through the first 45° tilted fiber grating 2 and the birefringent chirped spiral fiber grating 3, and then incident into the alkali metal gas chamber 7, causing electronic spin polarization of the alkali metal atoms and nuclear spin polarization of the inert gas; the probe light source 4 emits probe light, which is converted into linearly polarized light after passing through the second 45° tilted fiber grating 5, and then incident into the alkali metal gas chamber 7, where its polarization state is modulated by the nuclear spin polarized inert gas; the fiber coupler 6 The fiber optic filter 8 is used to couple the pump light and probe light into the alkali metal gas chamber 7 after mixing them; the fiber optic filter 8 is used to filter out the pump light from the mixed light emitted from the alkali metal gas chamber 7, and retain only the probe light from the mixed light; the polarization analyzer 9 is used to collect and process the probe light emitted from the alkali metal gas chamber 7 to obtain the polarization state of the probe light and calculate the angular rate of the angular rate sensor; the magnetic field generator 10 is used to provide static magnetic fields in the X-axis, Y-axis and Z-axis directions for the alkali metal gas chamber 7, so that the nuclear spin polarized inert gas undergoes Larmor precession around the static magnetic field.

[0088] The pump light has the same frequency as the intrinsic frequency of the alkali metal atoms, allowing it to resonate with the atoms and induce electron spin polarization. The probe light has a frequency as far away as possible from the intrinsic frequency of the alkali metal atoms to avoid affecting their electron spin polarization.

[0089] The first 45° tilted fiber grating 2 has its grating writing plane set at a 45° angle to its fiber axis, which allows almost all of the p-polarized light in the pump light to leak out of the fiber, while retaining almost all of the s-polarized light in the pump light for transmission within the fiber, thereby converting the pump light into linearly polarized light. The birefringent chirped spiral fiber grating 3, based on the birefringence effect, has a chirped spiral structure that can cause different degrees of phase delay in the linearly polarized light. When the polarization direction of the first 45° tilted fiber grating 2 is parallel to the major or minor axis of the birefringent chirped spiral fiber grating 3, the birefringent chirped spiral fiber grating 3 can cause different degrees of phase delay in the linearly polarized light output by the first 45° tilted fiber grating 2. The linearly polarized light with different phase delays is mixed to finally form circularly polarized light.

[0090] Whether the polarization direction of the first 45° tilted fiber grating 2 is parallel to the major axis or the minor axis of the birefringent chirped spiral fiber grating 3, it can convert the linearly polarized light into circularly polarized light. There is no substantial difference in performance or function in converting the linearly polarized light into the circularly polarized light.

[0091] The second 45° tilted fiber grating 5 has its grating writing plane set at a 45° angle to its fiber axis. Like the first 45° tilted fiber grating 2, it can almost completely leak the p-polarized light in the probe light outside the fiber, while almost completely retaining the s-polarized light in the probe light for transmission in the fiber, thereby converting the probe light into linearly polarized light.

[0092] The first 45° tilted fiber grating 2, the second 45° tilted fiber grating 5, and the birefringent chirped spiral fiber grating 3 can be made of single-mode fiber. In order to maintain the polarization state of the probe light and the pump light during transmission, the first 45° tilted fiber grating 2, the second 45° tilted fiber grating 5, and the birefringent chirped spiral fiber grating 3 can also be made of polarization-maintaining fiber.

[0093] Considering the difficulty in fabricating 45° tilted fiber gratings using polarization-maintaining fiber, and the fact that the birefringent chirped spiral fiber grating 3 requires a large birefringence and polarization-maintaining capability, in this embodiment, the first 45° tilted fiber grating 2 and the second 45° tilted fiber grating 5 are fabricated using single-mode fiber, and the birefringent chirped spiral fiber grating 3 is fabricated using polarization-maintaining fiber.

[0094] Optimally, the birefringent chirped spiral fiber grating 3 is fabricated using elliptical core fiber, so that the birefringent chirped spiral fiber grating 3 forms an elliptical core chirped spiral fiber grating. The elliptical core fiber is a special polarization-maintaining fiber, whose core cross-section is elliptical, rather than the traditional circular. The elliptical core structure can endow the elliptical core fiber with greater birefringence and polarization maintenance capabilities.

[0095] The grating period of the birefringent chirped spiral fiber grating 3 gradually decreases along the light transmission direction, and the minimum grating period of the birefringent chirped spiral fiber grating 3 is not less than the grating period of the first 45° tilted fiber grating 2, so as to achieve a good circular polarization conversion effect.

[0096] The angular rate sensor also includes a non-magnetic heating box 11 and a magnetic shielding box 12. The non-magnetic heating box 11 is disposed outside the alkali metal gas chamber 7 to increase the number density of alkali metal atoms and improve the detection accuracy of angular rate. The magnetic shielding box 12 is disposed outside the magnetic field generator 10 to isolate external magnetic fields and reduce the disturbance of spin polarization by external magnetic fields.

[0097] Example 4

[0098] like Figure 6 As shown, an alkali metal gas chamber based on a cross tube includes a cross tube 710b, a first fiber collimator 720, a second fiber collimator 730, and a third fiber collimator 740. The cross tube 710b includes a first cylindrical tube 711, a second cylindrical tube 713, and a conical tube 712. One side port of the second cylindrical tube 713 is connected to the middle of the first cylindrical tube 711, and the second cylindrical tube 713 is perpendicular to the first cylindrical tube 711. The narrow port of the conical tube 712 is connected to... The first cylindrical tube 711 is located in the middle; the first optical fiber collimator 720 and the second optical fiber collimator 730 are respectively sealed in the two side ports of the first cylindrical tube 711, and the third optical fiber collimator 740 is sealed in the other side port of the second cylindrical tube 713, with the first optical fiber collimator 720 and the second optical fiber collimator 730 aligned with each other; the wide port of the conical tube 712 is sealed, and the cross tube 710b is filled with at least alkali metal atoms and inert gas.

[0099] The alkali metal gas chamber 7 of the present invention uses the cross tube 710b as a carrier and is formed by filling the cross tube 710b with alkali metal atoms and inert gas. A first fiber collimator 720 and a second fiber collimator 730 are respectively arranged in the opposite two ports of the first cylindrical tube 711 of the cross tube 710b for detecting the incident and alignment of light in the cross tube 710b. A third fiber collimator 740 is arranged in one port of the second cylindrical tube 713 of the cross tube 710b for pumping light incident and alignment in the cross tube 710b. While realizing the miniaturization of the gas chamber, it can ensure high airtightness, high surface accuracy, and good inner wall condition of the gas chamber, and it is relatively easy to realize the release and filling of alkali metal atoms and inert gas in a vacuum environment.

[0100] In this embodiment, the conical tube 712 is perpendicular to the first cylindrical tube 711, and one side port of the second cylindrical tube 713 is connected to the center position of the first cylindrical tube 711. The narrow port of the conical tube 712 is also connected to the center position of the first cylindrical tube 711. The central axes of the second cylindrical tube 713 and the conical tube 712 coincide. The wide port of the conical tube 712 is used as the filling port for the alkali metal atoms and inert gas, and after the filling of the alkali metal atoms and inert gas is completed, it is sealed by melting to achieve a sealing setting.

[0101] Preferably, the first fiber collimator 720 and the second fiber collimator 730 are respectively bonded and fixed to the opposite two ports of the first cylindrical tube 711 by vacuum sealant, and the opposite two ports of the first cylindrical tube 711 are sealed respectively. The third fiber collimator 740 is also bonded and fixed to the other port of the second cylindrical tube 713 by vacuum sealant, and the other port of the second cylindrical tube 713 is sealed, so as to increase the airtightness of the cross tube 710b.

[0102] In use, the first fiber collimator 720 is used to detect the incident light, the second fiber collimator 730 is used to detect the outgoing light, the first fiber collimator 720 and the second fiber collimator 730 are aligned with each other, and the third fiber collimator 740 is used for the incident pump light. The pump light is circularly polarized, and the probe light is linearly polarized. The pump light excites the alkali metal atoms in the cross tube 710b to undergo electronic spin polarization. The alkali metal atoms induce nuclear spin polarization of the inert gas through a spin-exchange collision mechanism. Under a static magnetic field, the nuclear spin-polarized inert gas undergoes Larmor precession around the static magnetic field, and the precession frequency is related to the static magnetic field. When the angular rate sensor rotates around the static magnetic field along with the carrier, the precession frequency of the nuclear spin of the inert gas will drift. The amount of drift is the angular rate of the angular rate sensor. The drift of the precession frequency will cause the polarization plane of the probe light to rotate, thereby causing a change in the polarization state of the probe light. By analyzing the change in the polarization state of the probe light, the angular rate of the angular rate sensor can be calculated.

[0103] Preferably, the cross tube 710b is further filled with at least one of a buffer gas (an inert gas without nuclear spin) and a quenching gas (a diatomic molecule).

[0104] The buffer gas is used to collide with the alkali metal atoms to reduce the collision between the alkali metal atoms and the tube wall of the cross tube 710b, thereby reducing the depolarization rate of the alkali metal atoms and reducing the photon energy required for polarization of the alkali metal atoms, thus increasing the polarizability of the alkali metal atoms. The quenching gas is used to absorb the resonant photons spontaneously emitted when the alkali metal atoms recover from the excited state to the ground state, so as to avoid the resonant photons causing other alkali metal atoms to jump back from the ground state to the excited state and cause depolarization, thereby reducing the depolarization rate of the alkali metal atoms.

[0105] The alkali metal atom may be, but is not limited to, cesium (Cs) or rubidium (Rb) atoms, and the inert gas may be, but is not limited to, xenon, neon, or helium. 3 The buffer gas may be, but is not limited to, helium (He), etc. 4 The quenching gas may be, but is not limited to, nitrogen, etc. (e.g., He).

[0106] Example 5

[0107] like Figure 7 As shown, a method for preparing and filling an alkali metal gas chamber is provided for preparing and filling the alkali metal gas chamber 7 described in Example 4; the preparation and filling method includes the following steps:

[0108] Step 100: Provide a cross tube 710b, the cross tube 710b including a first cylindrical tube 711, a second cylindrical tube 713 and a conical tube 712, one side port of the second cylindrical tube 713 is connected to the middle of the first cylindrical tube 711, and the second cylindrical tube 713 is perpendicular to the first cylindrical tube 711, and the narrow port of the conical tube 712 is connected to the middle of the first cylindrical tube 711.

[0109] In step 100, the cross tube 710b is composed of a first cylindrical tube 711, a second cylindrical tube 713, and a conical tube 712. First, the first cylindrical tube 711 is placed and fixed on a three-dimensional displacement platform. Then, a CO2 laser output is aligned with the outer wall of the first cylindrical tube 711. Next, the three-dimensional displacement platform moves the first cylindrical tube 711 relative to the CO2 laser according to a preset motion trajectory, so that the CO2 laser ablates a first circular hole on the outer wall of the first cylindrical tube 711 that is slightly larger than the narrow end of the conical tube 712. Then, the first cylindrical tube 711 is rotated 180°. Then, the three-dimensional displacement platform moves the first cylindrical tube 711 again according to the preset motion trajectory. The tube is displaced relative to the CO2 laser so that the CO2 laser ablates a second circular hole slightly larger than the port of the cylindrical tube on the outer wall of the first cylindrical tube 711. Then, the narrow port of the conical tube 712 is aligned with the first circular hole ablated by the first cylindrical tube 711. A precision discharge system is then used to discharge at the contact point between the conical tube 712 and the first cylindrical tube 711 to fuse them together. Then, one side port of the second cylindrical tube 713 is aligned with the second circular hole ablated by the second cylindrical tube 713. A precision discharge system is then used to discharge at the contact point between the second cylindrical tube 713 and the first cylindrical tube 711 to fuse them together, ultimately forming the cross tube 710b.

[0110] In this embodiment, the conical tube 712 is perpendicular to the first cylindrical tube 711, and the central axes of the second cylindrical tube 713 and the conical tube 712 coincide.

[0111] Step 200: Provide a first fiber optic collimator 720, a second fiber optic collimator 730 and a third collimator, and seal the first fiber optic collimator 720 and the second fiber optic collimator 730 in the two side ports of the first cylindrical tube 711 respectively and align them with each other, and seal the third fiber optic collimator 740 in the other side port of the second cylindrical tube 713.

[0112] In step 200, vacuum sealant is first applied to the outer surfaces of the first fiber optic collimator 720, the second fiber optic collimator 730, and the third fiber optic collimator 740. Then, the first fiber optic collimator 720 and the second fiber optic collimator 730 are respectively inserted into the two side ports of the first cylindrical tube 711, and the third fiber optic collimator 740 is inserted into the other side port of the second cylindrical tube 713, so that the vacuum sealant on the outer surfaces of the first fiber optic collimator 720, the second fiber optic collimator 730, and the third fiber optic collimator 740 is bonded to the inner walls of the first cylindrical tube 711 and the second cylindrical tube 713, respectively. Then, the vacuum sealant is applied to the annular end faces of both sides of the first cylindrical tube 711 and the annular end face of the other side of the second cylindrical tube 713. Simultaneously, the vacuum sealant on the annular end faces of both sides of the first cylindrical tube 711 and the other annular end face of the first cylindrical tube 711 is bonded to the outer sides of the first fiber collimator 720, the second fiber collimator 730, and the third fiber collimator 740, respectively, thus achieving pre-fixation of the first fiber collimator 720, the second fiber collimator 730, and the third fiber collimator 740 to the first cylindrical tube 711 and the second cylindrical tube 713, respectively. Then, the... The pigtail of the first fiber optic collimator 720 is connected to a red laser pointer so that the red laser pointer illuminates a red laser beam into the first fiber optic collimator 720. Then, the pigtail of the second fiber optic collimator 730 is observed, and the relative positions between the first fiber optic collimator 720 and the second fiber optic collimator 730 are adjusted so that the red laser beam exits from the pigtail of the second fiber optic collimator 730, thus completing the alignment between the first fiber optic collimator 720 and the second fiber optic collimator 730. Then, the pigtail of the third fiber optic collimator 740 is connected to another red laser pointer so that the other red laser pointer illuminates the third fiber optic collimator 740. Another red laser beam is incident inside the collimator 740. The position of the third fiber collimator 740 is adjusted so that the two laser beams intersect within the T-tube 710a, thus completing the alignment of the third fiber collimator 740. Finally, the vacuum sealant between the first fiber collimator 720, the second fiber collimator 730, and the third fiber collimator 740 and the first cylindrical tube 711 and the second cylindrical tube 713 is cured, thereby sealing and fixing the first fiber collimator 720, the second fiber collimator 730, and the third fiber collimator 740 to the first cylindrical tube 711 and the second cylindrical tube 713, respectively. The curing method of the vacuum sealant can be, but is not limited to, natural curing, light curing, and heat curing.

[0113] Step 300: At least alkali metal atoms and inert gas are filled into the cross tube 710b through the conical tube 712.

[0114] In step 300, a preparation and filling device is used to fill the alkali metal gas and inert gas into the cross tube 710b through the conical tube 712. For example... Figure 9 As shown, the preparation and filling device includes a sealed chamber 13, a three-dimensional displacement platform 14, a heating laser 15, an alkali metal element 16, a vacuum pump 17, a first gas cylinder 18 filled with inert gas, and a host computer 21. The three-dimensional displacement platform 14, the heating laser 15, and the alkali metal element 16 are all disposed inside the sealed chamber 13, while the vacuum pump 17, the first gas cylinder 18, and the host computer 21 are all disposed outside the sealed chamber 13. The vacuum pump 17 and the first gas cylinder 18 are connected to the sealed chamber 13 through pipelines, and the host computer 21 is connected to control the three-dimensional displacement platform 14 and the heating laser 15.

[0115] Preferably, the preparation and filling device further includes at least one of a second gas cylinder 19 filled with buffer gas and a third gas cylinder 20 filled with quenching gas, wherein the second gas cylinder 19 and the third gas cylinder 20 are both located outside the sealed chamber 13 and are connected to the sealed chamber 13 through pipelines.

[0116] In this embodiment, the laser heater is a CO2 laser.

[0117] Specifically, such as Figure 8 As shown, in step 300, the step of filling the cross tube 710b with at least alkali metal atoms and inert gas through the conical tube 712 is as follows:

[0118] Step 310: Place the cross tube 710b into the sealed chamber 13.

[0119] In step 310, the sealed chamber 13 is a vacuum glove box, which facilitates the placement of the cross tube 710b by technicians outside the vacuum glove box.

[0120] Step 320: Evacuate the sealed chamber 13 to create a vacuum environment.

[0121] In step 330, the vacuum pump 17 is started to evacuate the sealed chamber 13 until the required vacuum level is reached, and then the evacuation is stopped.

[0122] Step 330: Inert gas is introduced into the sealed chamber 13, so that the inert gas fills the cross tube 710b through the conical tube 712.

[0123] In step 330, the first gas cylinder 18 is opened, allowing the inert gas in the first gas cylinder 18 to fill the sealed chamber 13. Since the cross tube 710b is connected to the sealed chamber 13 through the conical tube 712, the inert gas in the sealed chamber 13 will naturally fill the cross tube 710b through the conical tube 712.

[0124] Preferably, in step 330, at least one of a buffer gas and a quenching gas is introduced into the sealed chamber 13, so that at least one of the buffer gas and the quenching gas fills the cross tube 710b through the conical tube 712.

[0125] In step 330, the second gas cylinder 19 and / or the third gas cylinder 20 are opened, so that the buffer gas in the second gas cylinder 19 and / or the quenching gas filled in the third gas cylinder 20 fill the sealed chamber 13. Since the cross tube 710b is connected to the sealed chamber 13 through the conical tube 712, the buffer gas and / or quenching gas in the sealed chamber 13 will naturally fill the cross tube 710b through the conical tube 712.

[0126] In step 330, the outflow rates of the inert gas, buffer gas, and quenching gas can be controlled by a flow valve, thereby adjusting the mixing ratio between the inert gas, buffer gas, and quenching gas.

[0127] Step 340: Place the alkali metal element 16 into the conical tube 712.

[0128] In step 340, the vacuum chamber can be a vacuum glove box, so that after the technician has filled the inert gas, buffer gas and quenching gas, he can place the alkali metal element 16 in the vacuum chamber into the conical tube 712 of the cross tube 710b.

[0129] Of course, a robotic arm can also be installed inside the vacuum glove box to automatically place the alkali metal element 16.

[0130] The alkali metal element 16 is spherical. The inner diameter of the conical tube 712 at its narrow end should be larger than the diameter of the alkali metal element 16 to prevent the alkali metal element 16 from falling into the first cylindrical tube 711 or the second cylindrical tube 713. At the same time, the inner diameter of the conical tube 712 at its wide end should not be too small to ensure that the alkali metal element 16 can be placed in stably.

[0131] Step 350: The alkali metal element 16 is heated to vaporize and release alkali metal atoms, which then fill the cross tube 710b through the conical tube 712.

[0132] In step 350, the host computer 21 first controls the three-dimensional displacement platform 14 to move the cross tube 710b to align the alkali metal element 16 on the cross tube 710b with the laser heater. Then, the host computer controls the laser heater to emit a high-power laser beam to the alkali metal element 16 to heat the alkali metal element 16 to its vaporization temperature. When the alkali metal element 16 vaporizes, it releases alkali metal atoms to the surroundings. The alkali metal atoms released downwards enter and fill the cross tube 710b through the conical tube 712.

[0133] In step 350, the atomic density of the alkali metal 16 in the cross tube 710b can be adjusted by controlling the heating time of the laser heater on the alkali metal 16.

[0134] Step 400: Seal the wide end of the conical tube 712.

[0135] In step 400, after the alkali metal atoms are filled, the host computer 21 controls the three-dimensional displacement platform 14 to move the cross tube 710b to align the outer wall of the conical tube 712 below the alkali metal element 16 with the laser heater. Then, the laser heater is controlled to emit a high-power laser beam to the conical tube 712 to heat it, causing it to melt at the heating point. The tube is then slowly stretched or rotated, and the diameter of the conical tube 712 at the melting point gradually decreases during the slow stretching or rotation process, thereby causing the conical tube 712 to break at the melting point and form a seal. Alternatively, clamps can be used to clamp and seal the conical tube 712 at the melting point before breaking it.

[0136] Example 6

[0137] like Figure 10As shown, an angular rate sensor includes a pump source 1, a first 45° tilted fiber grating 2, a birefringent chirped spiral fiber grating 3, a probe source 4, a second 45° tilted fiber grating 5, an alkali metal gas cell 7 as described in Embodiment 4, a polarization analyzer 9, and a magnetic field generator 10. The pump source 1 is connected to the third fiber collimator 740 of the alkali metal gas cell 7 via the first 45° tilted fiber grating 2 and the birefringent chirped spiral fiber grating 3 in sequence. The probe source 4 is connected to the first fiber collimator 720 of the alkali metal gas cell 7 via the second 45° tilted fiber grating 5. The polarization analyzer 9 is connected to the second fiber collimator 730 of the alkali metal gas cell 7. The polarization direction of the first 45° tilted fiber grating is parallel to the major axis or minor axis of the birefringent chirped spiral fiber grating 3. The magnetic field generator 10 is disposed outside the alkali metal gas cell 7.

[0138] The angular rate sensor of the present invention uses the first 45° tilted fiber grating 2 and the birefringent chirped spiral fiber grating 3 as the pump optical path at the front end, and the second 45° tilted fiber grating 5 as the probe optical path. The pump light and the probe light are respectively incident into the alkali metal gas cell 7 from two orthogonal directions through the first fiber collimator 720 and the third fiber collimator 740. At the rear end, the polarization analyzer 9 receives and demodulates the probe light emitted from the second fiber collimator 730. The pump optical path, the probe optical path, and the output optical path are all integrated on the optical fiber, which greatly improves the integration of the angular rate sensor and realizes the miniaturization of the angular rate sensor. Moreover, the optical fiber has the advantages of strong anti-electromagnetic interference capability, acid and alkali corrosion resistance, electrical insulation, high measurement accuracy, high reliability, and long service life. It also has a great competitive advantage in harsh environments such as strong electromagnetic interference.

[0139] The pump light source 1 is used to emit pump light, which is converted into circularly polarized light after passing through the first 45° tilted fiber grating 2 and the birefringent chirped spiral fiber grating 3 in sequence, and then incident into the alkali metal gas chamber 7, causing electronic spin polarization of the alkali metal atoms and nuclear spin polarization of the inert gas; the probe light source 4 is used to emit probe light, which is converted into linearly polarized light after passing through the second 45° tilted fiber grating 5, and then incident into the alkali metal gas chamber 7, where the polarization state of the nuclear spin polarized inert gas is modulated; the polarization analyzer 9 is used to collect and process the probe light emitted from the alkali metal gas chamber 7 to obtain the polarization state of the probe light and calculate the angular rate of the angular rate sensor; the magnetic field generator 10 is used to provide static magnetic fields in the X, Y, and Z directions of the alkali metal gas chamber 7, so that the nuclear spin polarized inert gas undergoes Larmor precession around the static magnetic field.

[0140] The pump light has the same frequency as the intrinsic frequency of the alkali metal atoms, allowing it to resonate with the atoms and induce electron spin polarization. The probe light has a frequency as far away as possible from the intrinsic frequency of the alkali metal atoms to avoid affecting their electron spin polarization.

[0141] The first 45° tilted fiber grating 2 has its grating writing plane set at a 45° angle to its fiber axis, which allows almost all of the p-polarized light in the pump light to leak out of the fiber, while retaining almost all of the s-polarized light in the pump light for transmission within the fiber, thereby converting the pump light into linearly polarized light. The birefringent chirped spiral fiber grating 3, based on the birefringence effect, has a chirped spiral structure that can cause different degrees of phase delay in the linearly polarized light. When the polarization direction of the first 45° tilted fiber grating 2 is parallel to the major or minor axis of the birefringent chirped spiral fiber grating 3, the birefringent chirped spiral fiber grating 3 can cause different degrees of phase delay in the linearly polarized light output by the first 45° tilted fiber grating 2. The linearly polarized light with different phase delays is mixed to finally form circularly polarized light.

[0142] Whether the polarization direction of the first 45° tilted fiber grating 2 is parallel to the major axis or the minor axis of the birefringent chirped spiral fiber grating 3, it can convert the linearly polarized light into circularly polarized light. There is no substantial difference in performance or function in converting the linearly polarized light into the circularly polarized light.

[0143] The second 45° tilted fiber grating 5 has its grating writing plane set at a 45° angle to its fiber axis. Like the first 45° tilted fiber grating 2, it can almost completely leak the p-polarized light in the probe light outside the fiber, while almost completely retaining the s-polarized light in the probe light for transmission in the fiber, thereby converting the probe light into linearly polarized light.

[0144] The first 45° tilted fiber grating 2, the second 45° tilted fiber grating 5, and the birefringent chirped spiral fiber grating 3 can be made of single-mode fiber. In order to maintain the polarization state of the probe light and the pump light during transmission, the first 45° tilted fiber grating 2, the second 45° tilted fiber grating 5, and the birefringent chirped spiral fiber grating 3 can also be made of polarization-maintaining fiber.

[0145] Considering the difficulty in fabricating 45° tilted fiber gratings using polarization-maintaining fiber, and the fact that the birefringent chirped spiral fiber grating 3 requires a large birefringence and polarization-maintaining capability, in this embodiment, the first 45° tilted fiber grating 2 and the second 45° tilted fiber grating 5 are fabricated using single-mode fiber, and the birefringent chirped spiral fiber grating 3 is fabricated using polarization-maintaining fiber.

[0146] Optimally, the birefringent chirped spiral fiber grating 3 is fabricated using elliptical core fiber, so that the birefringent chirped spiral fiber grating 3 forms an elliptical core chirped spiral fiber grating. The elliptical core fiber is a special polarization-maintaining fiber, whose core cross-section is elliptical, rather than the traditional circular. The elliptical core structure can endow the elliptical core fiber with greater birefringence and polarization maintenance capabilities.

[0147] The grating period of the birefringent chirped spiral fiber grating 3 gradually decreases along the light transmission direction, and the minimum grating period of the birefringent chirped spiral fiber grating 3 is not less than the grating period of the first 45° tilted fiber grating 2, so as to achieve a good circular polarization conversion effect.

[0148] The angular rate sensor also includes a non-magnetic heating box 11 and a magnetic shielding box 12. The non-magnetic heating box 11 is disposed outside the alkali metal gas chamber 7 to increase the number density of alkali metal atoms and improve the detection accuracy of angular rate. The magnetic shielding box 12 is disposed outside the magnetic field generator 10 to isolate external magnetic fields and reduce the disturbance of spin polarization by external magnetic fields.

[0149] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of the present invention and not to limit them. Although the embodiments of the present invention have been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the embodiments of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An alkali metal gas chamber based on a cross-shaped tube, characterized in that, The device includes a cross tube and a first, second, and third fiber optic collimator. The cross tube comprises a first cylindrical tube, a second cylindrical tube, and a conical tube. One side port of the second cylindrical tube is connected to the middle of the first cylindrical tube, and the second cylindrical tube is perpendicular to the first cylindrical tube. The narrow port of the conical tube is connected to the middle of the first cylindrical tube. The first and second fiber optic collimators are respectively sealed in the two side ports of the first cylindrical tube, and the third fiber optic collimator is sealed in the other side port of the second cylindrical tube. The first and second fiber optic collimators are aligned with each other. The wide port of the conical tube is sealed. The cross tube is filled with at least alkali metal atoms and an inert gas.

2. The alkali metal gas chamber according to claim 1, characterized in that, The cross tube is also filled with at least one of a buffer gas and a quenching gas.

3. A method for preparing and filling an alkali metal gas chamber, characterized in that, Includes the following steps: Step 100: Provide a cross tube, the cross tube including a first cylindrical tube, a second cylindrical tube and a conical tube, one side port of the second cylindrical tube is connected to the middle of the first cylindrical tube, and the second cylindrical tube is perpendicular to the first cylindrical tube, and the narrow port of the conical tube is connected to the middle of the first cylindrical tube. Step 200: Provide a first fiber collimator, a second fiber collimator and a third fiber collimator, and seal the first fiber collimator and the second fiber collimator in the two side ports of the first cylindrical tube respectively and align them with each other, and seal the third fiber collimator in the other side port of the second cylindrical tube. Step 300: At least alkali metal atoms and inert gas are filled into the cross tube through the conical tube; Step 400: Seal the wide end of the conical tube.

4. The preparation and filling method according to claim 3, characterized in that, In step 300, the step of filling the cross tube with at least alkali metal atoms and inert gas through the conical tube is as follows: Step 310: Place the cross tube into the sealed chamber; Step 320: Evacuate the sealed chamber to create a vacuum environment; Step 330: Inert gas is introduced into the sealed chamber, so that the inert gas fills the cross tube through the conical tube; Step 340: Place the alkali metal element inside the conical tube; Step 350: The alkali metal element is heated to vaporize and release alkali metal atoms, which then fill the cross tube through the conical tube.

5. The preparation and filling method according to claim 4, characterized in that, In step 330, at least one of a buffer gas and a quenching gas is introduced into the sealed chamber, so that at least one of the buffer gas and the quenching gas fills the cross tube through the conical tube.

6. An angular rate sensor, characterized in that, The device includes a pump source, a first 45° tilted fiber grating, a birefringent chirped spiral fiber grating, a probe source, a second 45° tilted fiber grating, the alkali metal gas cell as described in claim 1, a polarization analyzer, and a magnetic field generator. The pump source is connected to a third fiber collimator of the alkali metal gas cell via the first 45° tilted fiber grating and the birefringent chirped spiral fiber grating in sequence. The probe source is connected to a first fiber collimator of the alkali metal gas cell via the second 45° tilted fiber grating. The polarization analyzer is connected to a second fiber collimator of the alkali metal gas cell. The polarization direction of the first 45° tilted fiber grating is parallel to the major or minor axis of the birefringent chirped spiral fiber grating. The magnetic field generator is disposed outside the alkali metal gas cell.

7. The angular rate sensor according to claim 6, characterized in that, The angular rate sensor also includes a non-magnetic heating box and a magnetic shielding box. The non-magnetic heating box is located outside the alkali metal gas chamber, and the magnetic shielding box is located outside the magnetic field generator.

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