A magnetometer gas chamber based on a fiber microcavity, a preparation and filling method and a full-fiber magnetometer

Abstract

The application discloses a magnetometer gas chamber based on an optical fiber microcavity, which comprises a single-mode optical fiber with an optical microcavity between an incident end face and an emission end face of the single-mode optical fiber, and at least filled with an alkali metal gas in the optical microcavity. The magnetometer gas chamber has the advantages of small volume, high integration and mass production, and can realize a full optical fiber structure of an atomic magnetometer. The application discloses a preparation and filling method of the magnetometer gas chamber and a full optical fiber magnetometer based on the magnetometer gas chamber.

Description

TECHNICAL FIELD

[0001] The present application relates to magnetic field sensing technology, in particular to a magnetometer gas chamber based on optical fiber microcavity, a preparation and filling method and an all-fiber magnetometer. BACKGROUND

[0002] As a kind of instrument specially used to measure the size of magnetic field, magnetometer has wide application in many fields such as military defense, geological exploration, deep space exploration, biomedicine, etc. Atomic magnetometer utilizes the interaction between light field and atom to polarize atom, and realizes the measurement of measured magnetic field by detecting atom spin precession signal.

[0003] In existing research, alkali metal gas chamber of atomic magnetometer is mostly closed transparent glass chamber manufactured by glass precision fusion process and glass-silicon-glass three-layer bonded chip-level gas chamber, which has problems of large volume, poor integration and difficult mass production. SUMMARY

[0004] In order to solve the above problems of the prior art, the present application provides a magnetometer gas chamber based on optical fiber microcavity, which has the advantages of small volume, high integration and mass production, and can realize all-fiber structure of atomic magnetometer.

[0005] The present application provides a preparation and filling method of the above-mentioned magnetometer gas chamber and an all-fiber magnetometer based on the above-mentioned magnetometer gas chamber.

[0006] The technical problem to be solved by the present application is solved by the following technical scheme:

[0007] A magnetometer gas chamber based on optical fiber microcavity, comprising:

[0008] A single-mode optical fiber with an optical microcavity, the optical microcavity being located between the incident end face and the exit end face of the single-mode optical fiber;

[0009] The optical microcavity is filled with at least alkali metal gas.

[0010] Further, the optical microcavity includes a first tapered portion and a second tapered portion, the first tapered portion and the second tapered portion are connected at the bottom surface and are symmetrical to each other.

[0011] Further, the optical microcavity is further filled with at least one of buffer gas and quenching gas.

[0012] A preparation and filling method of a magnetometer gas chamber, comprising the following steps:

[0013] Step 100: flattening one side end face of a single-mode optical fiber and one side end face of another single-mode optical fiber respectively;

[0014] Step 200: etching an optical micro-hole on each of the polished end faces of the two single-mode optical fibers;

[0015] Step 300: filling alkali metal gas into the optical micro-holes of the two single-mode optical fibers, and then heating and fusing the optical micro-holes of the two single-mode optical fibers to connect and close them to form the optical micro-cavity.

[0016] Further, the optical micro-hole is a tapered micro-hole, and the hole diameter gradually decreases from the fiber end face to the fiber interior.

[0017] Further, in step 200, the step of etching an optical micro-hole on each of the polished end faces of the two single-mode optical fibers is as follows:

[0018] Step 210: inserting the single-mode optical fiber into the ceramic ferrule, wherein the polished end face extends out of the ceramic ferrule;

[0019] Step 220: fixing the single-mode optical fiber and the ceramic ferrule to each other;

[0020] Step 230: grabbing the ceramic ferrule and grinding the polished end face of the single-mode optical fiber to grind the polished end face of the single-mode optical fiber to be flush with the end face of the ceramic ferrule;

[0021] Step 240: removing the ceramic ferrule from the single-mode optical fiber;

[0022] Step 250: immersing the ground end face of the single-mode optical fiber into a hydrofluoric acid solution, so that the hydrofluoric acid solution etches the optical micro-hole on the ground end face of the single-mode optical fiber;

[0023] Step 260: repeating steps 210-250 to make the same optical micro-hole on the polished end face of the other single-mode optical fiber.

[0024] Further, in step 300, the step of filling alkali metal gas into the optical micro-holes of the two single-mode optical fibers, and then heating and fusing the optical micro-holes of the two single-mode optical fibers to connect and close them to form the optical micro-cavity is as follows:

[0025] Step 310: placing the two single-mode optical fibers and the alkali metal element in a sealed chamber, wherein the optical micro-holes of the two single-mode optical fibers are oppositely arranged;

[0026] Step 320: vacuumizing the sealed chamber to form a vacuum environment in the sealed chamber;

[0027] Step 330: heating the alkali metal element in the sealed chamber to vaporize the alkali metal element to overflow the alkali metal gas;

[0028] Step 340: After the optical micro-holes of the two single-mode optical fibers are filled with the alkali metal gas, the relative positions of the two single-mode optical fibers are adjusted to align and abut the optical micro-holes of the two single-mode optical fibers to form an unsealed optical micro-cavity.

[0029] Step 350: The abutment of the two single-mode optical fibers is heated to fuse the optical micro-holes of the two single-mode optical fibers together at the abutment.

[0030] Further, in step 330, at least one of the buffer gas and the quenching gas is also filled into the optical micro-holes of the two single-mode optical fibers.

[0031] A full-fiber magnetometer comprises a pump light source, a first 45° tilted fiber grating, a birefringent chirped fiber grating, a probe light source, a second 45° tilted fiber grating, a fiber coupler, the above-mentioned magnetometer cell, a fiber filter, a light intensity analyzer and a magnetic field generator, the pump light source is connected to a first incident end of the fiber coupler through the first 45° tilted fiber grating and the birefringent chirped fiber grating in sequence, the probe light source is connected to a second incident end of the fiber coupler through the second 45° tilted fiber grating, an outgoing end of the fiber coupler is connected to an incident end face of the magnetometer cell, and the light intensity analyzer is connected to an outgoing end face of the magnetometer cell through the fiber filter; a polarization direction of the first 45° tilted grating is parallel to a long axis or a short axis of the birefringent chirped fiber grating, and the magnetic field generator is arranged outside the magnetometer cell.

[0032] Further, the full-fiber magnetometer further comprises a non-magnetic heating box, and the non-magnetic heating box is arranged outside the magnetometer cell.

[0033] The magnetometer cell provided by the application takes the optical micro-cavity inside the single-mode optical fiber as a carrier, and can ensure high airtightness, high surface shape precision and good inner wall state of the cell, and is easy to realize release and filling of the alkali metal gas in a vacuum environment, and realize full-fiber structure of an atomic magnetometer, thereby promoting development of the atomic magnetometer in the direction of small size, long service life, high performance, miniaturization and integration. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 A structure schematic diagram of the magnetometer cell provided by the application.

[0035] Figure 2 A step block diagram of a preparation and filling method of the magnetometer cell provided by the application.

[0036] Figure 3The step block diagram of step 200 in the preparation and filling method of the magnetometer gas chamber provided by the present application.

[0037] Figure 4 The step block diagram of step 300 in the preparation and filling method of the magnetometer gas chamber provided by the present application.

[0038] Figure 5 The structural diagram of the optical micro-hole in the preparation and filling method of the magnetometer gas chamber provided by the present application.

[0039] Figure 6 The grinding schematic diagram of the single-mode optical fiber in the preparation and filling method of the magnetometer gas chamber provided by the present application.

[0040] Figure 7 The structural principle schematic diagram of the preparation and filling system of the magnetometer gas chamber provided by the present application.

[0041] Figure 8 The structural principle schematic diagram of the all-fiber magnetometer provided by the present application.

[0042] Figure 9 The structural schematic diagram of the pump light path in the all-fiber magnetometer provided by the present application. DETAILED DESCRIPTION

[0043] The present application will be described in detail below with reference to the accompanying drawings and embodiments, and the examples of the embodiments are shown in the drawings, wherein the same or similar notations represent the same or similar elements or elements having the same or similar functions throughout. The embodiments described below by referring to the drawings are exemplary and are intended to explain the present application, and cannot be understood as a limitation of the present application.

[0044] In the description of the present application, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation of the present application.

[0045] In addition, the terms "first", "second", "third" are only for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined with "first", "second", "third" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0046] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connecting", "connecting", "fixing", "arranging" and the like should be understood in a broad sense, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0047] Embodiment one

[0048] As Figure 1 shown, a magnetometer gas chamber based on a fiber microcavity includes:

[0049] A single-mode optical fiber 110 has an optical microcavity 120 between the incident end face and the exit end face of the single-mode optical fiber 110.

[0050] The optical microcavity 120 is at least filled with an alkali metal gas 130.

[0051] The magnetometer gas chamber of the present application takes the optical microcavity 120 inside the single-mode optical fiber 110 as a carrier, and through filling the optical microcavity 120 with the alkali metal gas 130, it can ensure high airtightness, high surface shape accuracy and good gas chamber inner wall state, and it is relatively easy to realize the release and filling of the alkali metal gas 130 in a vacuum environment, and realize the all-fiber structure of the atomic magnetometer, thereby promoting the development of the atomic magnetometer in the direction of small volume, long life, high performance, miniaturization and integration.

[0052] In use, the pump light and the probe light are coupled into the single-mode optical fiber 110 from the incident end face, the pump light is circularly polarized light, and the probe light is linearly polarized light. The pump light excites the alkali metal gas 130 in the optical microcavity 120 to produce atomic polarization. Under an external magnetic field, the atomic polarization alkali metal gas 130 will spin precess around the external magnetic field, and the spin precession frequency is positively correlated with the size of the external magnetic field. When the probe light passes through the atomic polarization alkali metal gas 130, it will be modulated by the alkali metal gas 130, and the polarization plane will rotate, and the rotation of the polarization plane will cause the light component of the probe light in the transmission direction to change, thereby causing the light intensity of the probe light to change. Therefore, by measuring the light intensity change of the probe light, the spin precession frequency of the alkali metal gas 130 can be calculated, and finally the magnetic field size of the external magnetic field can be calculated.

[0053] The single-mode optical fiber 110 includes an optical fiber and a cladding 112, the cladding 112 surrounding the outer peripheral sidewall of the fiber core 111; the optical microcavity 120 has a length direction and a width direction, the length direction being parallel to the axial direction of the single-mode optical fiber 110, and the width direction being parallel to the radial direction of the single-mode optical fiber 110; the central axis of the optical microcavity 120 coincides with the central axis of the fiber core 111 of the single-mode optical fiber 110, and in the width direction, the optical microcavity 120 extends from the fiber core 111 to the cladding 112, and the maximum diameter of the optical microcavity 120 is smaller than the outer diameter of the cladding 112.

[0054] In this embodiment, the optical microcavity 120 includes a first conical portion 121 and a second conical portion 122, the bottom surfaces of the first conical portion 121 and the second conical portion 122 are connected and symmetrical to each other.

[0055] Preferably, the optical microcavity 120 is further filled with at least one of buffer gas 140 (an inert gas that does not generate nuclear spin) and quenching gas 150 (a diatomic molecule).

[0056] The buffer gas 140 is used to collide with the alkali metal gas 130 to reduce the collision between the alkali metal gas 130 and the cavity wall of the optical microcavity 120, thereby reducing the depolarization rate of the alkali metal gas 130 and the photon energy required for polarization of the alkali metal gas 130, and increasing the polarizability of the alkali metal gas 130. The quenching gas 150 is used to absorb the resonant photons spontaneously emitted when the alkali metal gas 130 recovers from the excited state to the ground state, so as to avoid the resonant photons causing other alkali metal gases 130 to re-jump from the ground state to the excited state and cause depolarization, thereby reducing the depolarization rate of the alkali metal gas 130.

[0057] The alkali metal gas 130 may be, but is not limited to, cesium metal gas (Cs) or rubidium metal gas (Rb), etc., and the buffer gas 140 may be, but is not limited to, helium (…). 4 The quenching gas 150 may be, but is not limited to, nitrogen.

[0058] Example 2

[0059] like Figure 1 As shown, a method for preparing and filling a magnetometer chamber is provided, used to prepare and fill the magnetometer chamber described in Example 1; the preparation and filling method includes the following steps:

[0060] Step 100: Cut one end face of one single-mode fiber 110 and the other end face of another single-mode fiber 110 flat.

[0061] In step 100, the length of the two single-mode optical fibers 110 is not particularly limited. The end face of the two single-mode optical fibers 110 is cut flat on one side using an optical fiber cleaver so that the end faces can be seamlessly connected. The other end face of the two single-mode optical fibers 110 serves as the incident end face and the exit end face of the magnetometer gas chamber, respectively.

[0062] Step 200: Etch patterns such as... on the flattened end faces of the two single-mode optical fibers 110. Figure 5 An optical micro-aperture 120' is shown.

[0063] In step 200, the optical micro-aperture 120' is a tapered micro-aperture, the diameter of which gradually decreases from the end of the optical fiber to the inside of the optical fiber, and the two optical micro-apertures 120' serve as the first tapered portion 121 and the second tapered portion 122 of the optical microcavity 120, respectively.

[0064] Specifically, such as Figure 3 As shown, in step 200, the step of etching an optical micro-hole 120' on the flattened end faces of the two single-mode optical fibers 110 is as follows:

[0065] Step 210: As Figure 6 As shown, the single-mode optical fiber 110 is inserted into the ceramic ferrule 160, wherein the flattened end face extends out of the ceramic ferrule 160.

[0066] In step 210, since the single-mode fiber 110 is soft and easily bent, it is difficult to grasp and grind the end face. Therefore, it is necessary to first fix the ceramic ferrule 160 on the single-mode fiber 110 so that the single-mode fiber 110 can be grasped by grasping the hard ceramic fiber core 111. The length of the flattened end face of the single-mode fiber 110 extending out of the ceramic ferrule 160 should not be too large to ensure that the flattened end face of the single-mode fiber 110 will not shift under the action of friction during grinding.

[0067] The length of the ceramic ferrule 160 is not specific and should be easy to grip. Its inner diameter is similar to or slightly larger than the outer diameter of the single-mode fiber 110 to facilitate the insertion of the single-mode fiber 110 into the ceramic ferrule 160 while avoiding excessive friction between the two.

[0068] Step 220: Fix the single-mode optical fiber 110 and the ceramic ferrule 160 together.

[0069] In step 220, the single-mode optical fiber 110 and the ceramic ferrule 160 are preferably bonded and fixed with thermal adhesive or photosensitive adhesive, so that when the ceramic ferrule 160 is subsequently peeled off, the bonding force between the single-mode optical fiber 110 and the ceramic ferrule 160 can be reduced by changing the ambient temperature or irradiating with light of a specific wavelength.

[0070] Step 230: Grasp the ceramic ferrule 160 and grind the polished end face of the single-mode optical fiber 110 to make the polished end face of the single-mode optical fiber 110 flush with the end face of the ceramic ferrule 160.

[0071] In this step 230, the ceramic ferrule 160 can be grasped manually and the polished end face of the single-mode optical fiber 110 can be manually ground on sandpaper 170, or the ceramic ferrule 160 can be grasped by a mechanical hand or clamp and the polished end face of the single-mode optical fiber 110 can be automatically ground on an optical fiber grinder.

[0072] Step 240: Remove the ceramic ferrule 160 from the single-mode optical fiber 110.

[0073] In this step 240, the single-mode optical fiber 110 and the ceramic ferrule 160 are fixedly bonded by using a heat-sensitive glue or a light-sensitive glue, and when the ceramic ferrule 160 is peeled off, the bonding force between the single-mode optical fiber 110 and the ceramic ferrule 160 is reduced by changing the ambient temperature or irradiating a specific wavelength of light.

[0074] Step 250: Dip the polished end face of the single-mode optical fiber 110 into a hydrofluoric acid solution, so that the hydrofluoric acid solution etches the optical micro-hole 120' on the polished end face of the single-mode optical fiber 110.

[0075] In this step 250, the concentration of the hydrofluoric acid is 40%, and after the end face of the single-mode optical fiber 110 is ground, the stress structure is destroyed and can be more easily etched by the hydrofluoric acid solution, while the outside of the single-mode optical fiber 110 can resist the etching of the hydrofluoric acid solution because the stress structure is not destroyed. At this time, the etching degree of the hydrofluoric acid solution on the polished end face of the single-mode optical fiber 110 can be adjusted by controlling the soaking time of the single-mode optical fiber 110 in the hydrofluoric acid solution, and then the hole depth and the maximum aperture of the optical micro-hole 120' can be controlled.

[0076] Step 260: Repeat steps 210-250 to make the same optical micro-hole 120' on the polished end face of another single-mode optical fiber 110.

[0077] Step 300: Fill the alkali metal gas 130 into the optical micro-holes 120' of the two single-mode optical fibers 110, and then heat and fuse the optical micro-holes 120' of the two single-mode optical fibers 110 to make them connected and closed to form the optical micro-cavity 120.

[0078] In this step 300, the two single-mode optical fibers 110 are aligned, inflated and sealed by using a self-built preparation and filling system. As shown in Figure 7 The preparation and filling system includes a sealed chamber 1, a carbon dioxide laser 2, a first displacement platform 3, a second displacement platform 4, an ultraviolet laser 5, an alkali metal element 6, a vacuum pump 7 and a host computer 8. The carbon dioxide laser 2, the first displacement platform 3, the second displacement platform 4, the ultraviolet laser 5 and the alkali metal element 6 are arranged in the sealed chamber 1, and the vacuum pump 7 and the host computer 8 are arranged outside the sealed chamber 1. The vacuum pump 7 is connected to the sealed chamber 1, and the host computer 8 is connected to control the carbon dioxide laser 2, the first displacement platform 3, the second displacement platform 4 and the ultraviolet laser 5.

[0079] The vacuum pump 7 is used to vacuum the sealed chamber 1 to provide a vacuum environment. The carbon dioxide laser 2 is used to emit high-power ultraviolet laser to the alkali metal element 6 to heat and vaporize the alkali metal element 6 to form the alkali metal gas 130. The first displacement platform 3 and the second displacement platform 4 are used to drive the two single-mode optical fibers 110 to displace respectively. The carbon dioxide laser 2 is used to fuse the two single-mode optical fibers 110.

[0080] Preferably, the preparation and filling system further includes at least one of a first gas cylinder 9 filled with a buffer gas 140 and a second gas cylinder 10 filled with a quenching gas 150. The first gas cylinder 9 and the second gas cylinder 10 are located outside the sealed chamber 1 and are connected to the sealed chamber 1. The first gas cylinder 9 is used to introduce the buffer gas 140 into the sealed chamber 1, and the second gas cylinder 10 is used to introduce the quenching gas 150 into the sealed chamber 1.

[0081] In this embodiment, the first displacement platform 3 and the second displacement platform 4 are both three-axis displacement platforms.

[0082] Specifically, as shown in Figure 4 In this step 300, after the alkali metal gas 130 is filled into the optical micro-holes 120' of the two single-mode optical fibers 110, the optical micro-holes 120' of the two single-mode optical fibers 110 are heated and fused to be connected and sealed to form the optical micro-cavity 120. The steps are as follows:

[0083] Step 310: Place the two single-mode optical fibers 110 and the alkali metal element 6 in the sealed chamber 1, wherein the optical micro-holes 120' of the two single-mode optical fibers 110 are oppositely arranged.

[0084] In this step 310, two single-mode optical fibers 110 are respectively placed on the first displacement platform 3 and the second displacement platform 4 of the closed chamber 1, which are oppositely arranged in the closed chamber 1 to make the optical micro-holes 120' of the two single-mode optical fibers 110 opposite. The alkali metal element 6 is placed in the irradiation range of the ultraviolet laser 5, as close as possible to the emission side of the ultraviolet laser 5.

[0085] Step 320: The closed chamber 1 is vacuumized to form a vacuum environment.

[0086] In this step 320, the vacuum pump 7 is started to vacuumize the closed chamber 1, and the pumping is stopped after the closed chamber 1 reaches the required vacuum degree.

[0087] Step 330: The alkali metal element 6 in the closed chamber 1 is heated to vaporize the alkali metal gas 130.

[0088] In this step 330, the ultraviolet laser 5 is used to emit high-power ultraviolet laser to the alkali metal element 6 to heat the alkali metal element 6, so that the temperature of the alkali metal element 6 reaches its vaporization temperature, and then the alkali metal gas 130 is overflowed until the alkali metal gas 130 uniformly fills the entire closed chamber 1. Since the two single-mode optical fibers 110 are both in the closed chamber 1 in the un-fused state, the alkali metal gas 130 in the closed chamber 1 will naturally fill the two optical micro-holes 120'.

[0089] Preferably, at least one of the buffer gas 140 and the quenching gas 150 is filled in the optical micro-holes 120' of the two single-mode optical fibers 110 in this step 330. Specifically, while heating the alkali metal element 6, the first gas cylinder 9 and the second gas cylinder 10 are opened, so that the buffer gas 140 in the first gas cylinder 9 and the quenching gas 150 in the second gas cylinder 10 uniformly fill the entire closed chamber 1. Since the two single-mode optical fibers 110 are both in the closed chamber 1 in the un-fused state, the buffer gas 140 and the quenching gas 150 in the closed chamber 1 will naturally fill the two optical micro-holes 120'.

[0090] Preferably, the mixing ratio among the alkali metal gas 130, the buffer gas 140 and the quenching gas 150 can be controlled by adjusting the flow rate of the buffer gas 140 and the quenching gas 150 and the irradiation time of the alkali metal element 6.

[0091] Step 340: After the optical micro-holes 120' of the two single-mode optical fibers 110 are filled with the alkali metal gas 130, the relative positions of the two single-mode optical fibers 110 are adjusted to align and abut the optical micro-holes 120' of the two single-mode optical fibers 110 to form an unsealed optical micro-cavity 120.

[0092] In this step 340, the first displacement platform 3 and the second displacement platform 4 are used to drive the two single-mode optical fibers 110 to displace, so as to adjust the relative positions of the two optical micro-holes 120' and abut the two optical micro-holes 120' after alignment, and the two optical micro-holes 120' form an unsealed optical micro-cavity 120 after abutting.

[0093] Step 350: The abutting part of the two single-mode optical fibers 110 is heated to fuse the optical micro-holes 120' of the two single-mode optical fibers 110 at the abutting part.

[0094] In this step 350, the carbon dioxide laser 2 is used to emit high-power carbon dioxide laser to the abutting part of the two single-mode optical fibers 110, so as to melt and connect the two optical micro-holes 120' at the abutting part to seal the alkali metal gas 130, the buffer gas 140 and the quenching gas 150.

[0095] Embodiment three

[0096] As shown in Figure 8 and 9 , a full-fiber magnetometer includes a pump light source 12, a first 45° inclined fiber grating 13, a birefringent chirped spiral fiber grating 14, a probe light source 15, a second 45° inclined fiber grating 16, a fiber coupler 17, the magnetometer gas chamber 11 of embodiment one, a fiber filter 18 and a light intensity analyzer 19, the pump light source 12 is connected to the first incident end of the fiber coupler 17 through the first 45° inclined fiber grating 13 and the birefringent chirped spiral fiber grating 14 in sequence, the probe light source 15 is connected to the second incident end of the fiber coupler 17 through the second 45° inclined fiber grating 16, the outgoing end of the fiber coupler 17 is connected to the incident end face of the magnetometer gas chamber 11, and the light intensity analyzer 19 is connected to the outgoing end face of the magnetometer gas chamber 11 through the fiber filter 18; the polarization direction of the first 45° inclined grating is parallel to the long axis or short axis of the birefringent chirped spiral fiber grating 14.

[0097] The all-fiber magnetometer of the present application adopts the first 45° inclined fiber grating 13 and the birefringent chirped spiral fiber grating 14 as the pump light path, and adopts the second 45° inclined fiber grating 16 as the probe light path, integrates the pump light path, the alkali gas chamber and the probe light path of the atomic magnetometer on the fiber, forms an all-fiber structure, greatly improves the integration of the atomic magnetometer, realizes the miniaturization of the atomic magnetometer, and the fiber has the advantages of strong anti-electromagnetic interference ability, acid and alkali corrosion resistance, electrical insulation, high measurement precision, high reliability, long service life and the like, and has a greater competitive advantage in harsh environments such as strong electromagnetic interference.

[0098] The pump light source 12 is used to emit pump light, which is converted into circularly polarized light after passing through the first 45° inclined fiber grating 13 and the birefringent chirped spiral fiber grating 14 in turn, to be incident into the magnetometer gas chamber 11 to cause atomic polarization of the alkali metal gas 130; the probe light source 15 is used to emit probe light, which is converted into linearly polarized light after passing through the second 45° inclined fiber grating 16, to be incident into the magnetometer gas chamber 11 to be modulated by the atomically polarized alkali metal gas 130; the fiber filter 18 is used to filter out the pump light emitted from the magnetometer gas chamber 11; and the light intensity analyzer 19 is used to collect and process the probe light emitted from the magnetometer gas chamber 11 to calculate the magnetic field size of the external magnetic field.

[0099] The optical frequency of the pump light is the same as the inherent frequency of the alkali metal gas 130, so that it can resonate with the alkali metal gas 130, and further cause atomic polarization of the alkali metal gas 130. The optical frequency of the probe light is as far away from the inherent frequency of the alkali metal gas 130 as possible, so as not to affect the atomic polarization of the alkali metal gas 130.

[0100] The fiber grating writing plane of the first 45° inclined fiber grating 13 is arranged at a 45° angle with the fiber axis, which can almost completely leak the p-polarized light in the pump light to the outside of the fiber, and almost completely retain the s-polarized light in the pump light for transmission in the fiber, and further convert the pump light into linearly polarized light; the birefringent chirped spiral fiber grating 14 is based on the birefringence effect, and the spiral structure with chirp change can cause different degrees of phase delay of the linearly polarized light, when the polarization direction of the first 45° inclined fiber grating 13 is parallel to the long axis or short axis of the birefringent chirped spiral fiber grating 14, the birefringent chirped spiral fiber grating 14 can cause different degrees of phase delay of the linearly polarized light output by the first 45° inclined fiber grating 13, and the linearly polarized light with different phase delays is mixed to finally form circularly polarized light.

[0101] The polarization direction of the first 45°-inclined fiber grating 13 is parallel to the long axis of the birefringent chirped spiral fiber grating 14 or parallel to the short axis of the birefringent chirped spiral fiber grating 14, and there is no substantial difference in performance and function in converting linearly polarized light into circularly polarized light.

[0102] The second 45°-inclined fiber grating 16 is arranged at an angle of 45° between the fiber grating writing plane and the fiber axis, and like the first 45°-inclined fiber grating 13, it can almost completely leak the p-polarized light in the probe light to the outside of the fiber and almost completely retain the s-polarized light in the probe light in the fiber for transmission, thereby converting the probe light into linearly polarized light.

[0103] Preferably, the birefringent chirped spiral fiber grating 14 is made of an elliptical core fiber so as to form an elliptical core chirped spiral fiber grating 14. The elliptical core fiber is a special polarization-maintaining fiber, and its core cross section is elliptical rather than the traditional circular shape. The elliptical core structure can give the elliptical core fiber a larger birefringence and polarization maintaining capability.

[0104] The fiber grating period of the birefringent chirped spiral fiber grating 14 gradually decreases along the light transmission direction, and the minimum fiber grating period of the birefringent chirped spiral fiber grating 14 is not less than the fiber grating period of the first 45°-inclined fiber grating 13, so as to achieve a good circular polarization conversion effect.

[0105] The all-fiber magnetometer further comprises a non-magnetic heating box 20 arranged outside the magnetometer chamber 11 for heating the magnetometer chamber 11 to increase the number density of the alkali metal gas 130 and improve the detection accuracy of the magnetic field.

[0106] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the embodiments of the present application rather than limiting them, and although the embodiments of the present application have been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the embodiments of the present application can still be modified or replaced by equivalents, and these modifications or equivalent replacements should not make the modified technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. An all-fiber magnetometer, characterized by, The full-optical fiber magnetometer comprises a pump light source, a first 45° inclined fiber grating, a birefringent chirped fiber grating, a probe light source, a second 45° inclined fiber grating, a fiber coupler, a magnetometer gas chamber, a fiber filter, a light intensity analyzer and a magnetic field generator, the pump light source is connected to the first incident end of the fiber coupler through the first 45° inclined fiber grating and the birefringent chirped fiber grating in sequence, the probe light source is connected to the second incident end of the fiber coupler through the second 45° inclined fiber grating, the exit end of the fiber coupler is connected to the incident end face of the magnetometer gas chamber, and the light intensity analyzer is connected to the exit end face of the magnetometer gas chamber through the fiber filter; the polarization direction of the first 45° inclined grating is parallel to the long axis or the short axis of the birefringent chirped fiber grating, and the magnetic field generator is arranged outside the magnetometer gas chamber. The magnetometer gas chamber comprises: A single-mode optical fiber with an optical microcavity between the incident end face and the exit end face of the single-mode optical fiber; The optical microcavity is filled with at least an alkali metal gas; The optical microcavity comprises a first tapered portion and a second tapered portion, and the bottom surfaces of the first tapered portion and the second tapered portion are connected and symmetrical to each other.

2. The all-fiber magnetometer of claim 1, wherein, The optical microcavity is further filled with at least one of a buffer gas and a quenching gas.

3. The all-fiber magnetometer of claim 1, wherein, The full-optical fiber magnetometer further comprises a non-magnetic heating box arranged outside the magnetometer gas chamber.

4. The all-fiber magnetometer of claim 1, wherein, The preparation and filling method of the magnetometer gas chamber comprises the following steps: Step 100: flattening the end face of one single-mode optical fiber and the end face of another single-mode optical fiber; Step 200: etching an optical microhole on the flattened end face of each of the two single-mode optical fibers; Step 300: filling the optical microholes of the two single-mode optical fibers with an alkali metal gas, and then heating and welding the optical microholes of the two single-mode optical fibers to connect and seal to form the optical microcavity.

5. The all-fiber magnetometer of claim 4, wherein, The optical microhole is a tapered microhole with a gradually decreasing hole diameter from the fiber end face to the fiber interior.

6. The all-fiber magnetometer of claim 4, wherein, In step 200, the step of etching an optical microhole on the flattened end face of each of the two single-mode optical fibers is as follows: Step 210: inserting the single-mode optical fiber into a ceramic plug, wherein the flattened end face protrudes out of the ceramic plug; Step 220: fixing the single-mode optical fiber and the ceramic plug to each other; Step 230: grabbing the ceramic plug and grinding the flattened end face of the single-mode optical fiber to grind the flattened end face of the single-mode optical fiber to be flush with the end face of the ceramic plug; Step 240: removing the ceramic plug from the single-mode optical fiber; Step 250: immersing the ground end face of the single-mode optical fiber into a hydrofluoric acid solution to etch the optical microhole on the ground end face of the single-mode optical fiber by the hydrofluoric acid solution; Step 260: repeating steps 210-250 to make the same optical microhole on the flattened end face of the other single-mode optical fiber.

7. The all-fiber magnetometer of claim 4, wherein, In step 300, after filling the alkali metal gas into the optical micro-holes of the two single-mode optical fibers, the optical micro-holes of the two single-mode optical fibers are heated and fused to be connected and closed to form the optical micro-cavity. The steps are as follows: Step 310: placing the two single-mode optical fibers and the alkali metal element in a closed chamber, wherein the optical micro-holes of the two single-mode optical fibers are oppositely arranged; Step 320: vacuumizing the closed chamber to form a vacuum environment in the closed chamber; Step 330: heating the alkali metal element in the closed chamber to vaporize the alkali metal element and overflow the alkali metal gas; Step 340: after the optical micro-holes of the two single-mode optical fibers are filled with the alkali metal gas, adjusting the relative positions of the two single-mode optical fibers to align and abut the optical micro-holes of the two single-mode optical fibers to form an unclosed optical micro-cavity; Step 350: heating the abutment of the two single-mode optical fibers to fuse the optical micro-holes of the two single-mode optical fibers at the abutment.

8. The all-fiber magnetometer of claim 7, wherein, In step 330, at least one of the buffer gas and the quenching gas is also filled into the optical micro-holes of the two single-mode optical fibers.

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