Reflection-type hollow-core optical fiber atomic gas chamber and preparation method thereof

Abstract

The invention discloses a reflection type hollow-core optical fiber atomic gas chamber which comprises a single-mode optical fiber, a hollow-core optical fiber, a lens optical fiber, an optical fiber grating and a quartz capillary tube. Wherein the single-mode optical fiber is connected with the hollow-core optical fiber; the lens fiber is connected with the fiber bragg grating; the hollow-core optical fiber, the lens optical fiber and the optical fiber grating are all located in the quartz capillary tube; the quartz capillary tube is filled with alkali metal atoms and buffer gas. According to the invention, difficulties in assembly of a reflective hollow-core optical fiber gas chamber and filling of alkali metal atoms are overcome, and the application requirements of the field of high-spatial-resolution weak magnetic measurement on miniaturized and array-integrated atomic gas chamber probes are met.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber optics and quantum sensing, and in particular relates to a reflective hollow-core optical fiber atomic gas chamber and a preparation method thereof. Background Art

[0002] Hollow-core optical fiber has the advantages of low transmission loss and controllable dispersion. Its unique hollow core structure can also be filled with atoms and gas media. Using the hollow core of the hollow-core optical fiber atomic gas chamber as a filling chamber for the gas medium can effectively enhance the interaction between light and the medium. It has broad application prospects in the fields of gas chromatography, fiber-optic gas sensing, and precision optical sensing. The transmission-type hollow-core optical fiber atomic gas chamber is not convenient for connecting the pipeline filled with working gas on its optical transmission link, which will increase the volume of the sample, and the working area is located in the middle of the sample, which is not conducive to the preparation and application of miniaturized, array-integrated atomic gas chamber probes. Summary of the invention

[0003] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, to provide a reflective hollow-core optical fiber atomic gas chamber and a preparation method thereof, to reduce the sample assembly volume, to overcome the difficulties in assembling the reflective hollow-core optical fiber gas chamber and filling it with alkali metal atoms, and to meet the application requirements of the field of high spatial resolution weak magnetic measurement for miniaturized, array-integrated atomic gas chamber probes.

[0004] The object of the present invention is achieved through the following technical scheme: a reflective hollow-core fiber atomic gas chamber, comprising: a single-mode fiber, a hollow-core fiber, a lens fiber, a fiber grating and a quartz capillary; wherein the single-mode fiber is connected to the hollow-core fiber; the lens fiber is connected to the fiber grating; the hollow-core fiber, the lens fiber and the fiber grating are all located in the quartz capillary; the quartz capillary is filled with alkali metal atoms and buffer gas.

[0005] In the above-mentioned reflective hollow-core fiber atomic gas chamber, the core of the single-mode fiber is 8 to 10 μm, and the single-mode fiber only propagates one mode; the inner layer of the hollow-core fiber is hollow, the air core diameter of the hollow-core fiber is 5 to 100 μm, and the hollow-core fiber is used to accommodate alkali metal atoms; the incident end of the lens fiber is a conical or spherical lens, which has the function of focusing the light beam; the reflectivity of the fiber grating is greater than 70%.

[0006] In the above-mentioned reflective hollow-core optical fiber atomic gas chamber, the inner diameter of the quartz capillary is 5 to 10 μm.

[0007] In the above-mentioned reflective hollow-core optical fiber atomic gas chamber, alkali metal atoms serve as the working medium in the hollow-core optical fiber, and the buffer gas is used to increase the atomic spin relaxation time of the hollow-core optical fiber.

[0008] In the above-mentioned reflective hollow-core optical fiber atomic gas chamber, the single-mode optical fiber, the hollow-core optical fiber, the lens optical fiber and the optical fiber grating are all made of silica.

[0009] In the above-mentioned reflective hollow-core fiber atomic gas chamber, the signal light is introduced into the hollow-core fiber from the single-mode fiber, and diverges in the form of a Gaussian beam at the end face of the hollow-core fiber. After spatial transmission, it is focused and converged at the incident end face of the lens fiber and enters the interior of the lens fiber. Finally, the light path is reflected at the fiber grating and re-enters the space and the hollow-core fiber.

[0010] A preparation method for a reflective hollow-core fiber atomic gas chamber comprises: fusing and butting a single-mode fiber with a hollow-core fiber to form a single-mode fiber-hollow-core fiber assembly; fusing and butting a lens fiber with a fiber grating to form a lens fiber-fiber grating assembly; placing the hollow-core fiber in the single-mode fiber-hollow-core fiber assembly into one end of a quartz capillary; fixing and sealing the hollow-core fiber and one end of the quartz capillary; placing the lens fiber-fiber grating assembly into the other end of the quartz capillary, adjusting the lens fiber-fiber grating assembly and fixing it with the quartz capillary by spot welding; wherein the lens fiber is opposite to the hollow-core fiber, and the lens fiber-fiber grating assembly is coaxial with the single-mode fiber-hollow-core fiber assembly; connecting the quartz capillary to a vacuum filling system, and performing leak detection, vacuuming, and filling with alkali metal atoms and buffer gas through the vacuum filling system; and fusing and sealing the other end of the quartz capillary to obtain a reflective hollow-core fiber atomic gas chamber.

[0011] In the above preparation method, the fusion-joining of the single-mode optical fiber and the hollow-core optical fiber includes: tapering the hollow-core optical fiber or reverse tapering the single-mode optical fiber to match the mode field sizes of the two, and laser welding after the end faces are neatly cut.

[0012] In the above preparation method, fixing and sealing the hollow-core optical fiber and one end of the quartz capillary includes: inserting the fused single-mode optical fiber-hollow-core optical fiber assembly into the quartz capillary, placing one end of the hollow-core optical fiber inside the quartz capillary, and using a fiber fusion splicer to laser bond and fusion to fix and seal the quartz capillary and the hollow-core optical fiber.

[0013] In the above preparation method, the lens fiber-fiber grating assembly is placed into the other end of the quartz capillary, and the lens fiber-fiber grating assembly is adjusted and fixed with the quartz capillary by spot welding, which includes: placing the lens fiber connected to the fiber grating on a six-dimensional adjustment frame; inserting one end of the single-mode fiber into one end of a bare fiber adapter; connecting the other end of the bare fiber adapter to the second port of the fiber circulator, connecting the first port of the fiber circulator to the laser, and connecting the third port of the fiber circulator to the optical power meter; the laser emits a beam of light, rotating the knob of the six-dimensional adjustment frame to adjust the position of the lens fiber-fiber grating assembly, and synchronously monitoring the reading of the optical power meter; when the reading of the optical power meter reaches the maximum value, fixing the lens fiber-fiber grating assembly in the quartz capillary by spot welding.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] (1) The present invention uses a fiber grating to reflect the signal light from the incident end, and the signal light enters the hollow-core fiber segment twice; compared with the transmission-type hollow-core fiber air chamber that requires the use of two hollow-core fibers, the assembly scheme of the reflection-type hollow-core fiber air chamber reduces the sample preparation cost and improves the assembly efficiency;

[0016] (2) The working gas filling direction of the present invention is parallel to the direction of the hollow-core optical fiber, which is more conducive to the filling of the working gas and the diffusion in the sample;

[0017] (3) The present invention directly fills the quartz capillary tube containing the single-mode fiber-hollow core fiber assembly and the lens fiber-fiber Bragg grating assembly without generating other branches. The volume is determined by the outer diameter and length of the quartz capillary tube, which is conducive to the miniaturization of the sample.

[0018] (4) The working area of ​​the reflective hollow-core optical fiber gas chamber of the present invention is located at the end of the sample, which is more conducive to being used as a probe in measurement fields such as optical fiber gas sensing and precision optical sensing. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0020] Figure 1 It is a schematic diagram of the assembly scheme of the reflective hollow-core optical fiber air chamber of the present invention;

[0021] Figure 2 is a flow chart of the assembly method of the present invention;

[0022] Figure 3It is a schematic diagram of the high-precision adjustment process of the lens fiber-fiber Bragg grating position;

[0023] Figure 4 This is a schematic diagram of the assembled reflective hollow-core optical fiber air chamber sample. DETAILED DESCRIPTION

[0024] Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided in order to enable a more thorough understanding of the present disclosure and to be able to fully convey the scope of the present disclosure to those skilled in the art. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features described in the embodiments can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0025] Figure 1 It is a schematic diagram of the assembly scheme of the reflective hollow-core optical fiber air chamber of the present invention; Figure 4 Figure 1 is a schematic diagram of the assembled reflective hollow-core optical fiber air chamber sample. Figure 1 and Figure 4 As shown, the reflective hollow-core fiber atomic gas chamber includes: a single-mode fiber 1, a hollow-core fiber 2, a lens fiber 3, a fiber grating 4 and a quartz capillary 5; wherein the single-mode fiber 1 is connected to the hollow-core fiber 2; the lens fiber 3 is connected to the fiber grating 4; the hollow-core fiber 2, the lens fiber 3 and the fiber grating 4 are all located in the quartz capillary 5; the quartz capillary 5 is filled with alkali metal atoms 6 and buffer gas.

[0026] Single-mode optical fiber 1, the core of the single-mode optical fiber is 8 to 10 μm, only one mode is transmitted, and it is used to input and output signal light; hollow-core optical fiber 2, the inner layer of the hollow-core optical fiber is hollow, and the air core diameter is 5 to 100 μm, which is used to accommodate alkali metal atoms. The unique structure of the hollow-core optical fiber enables the propagation of signal light in the hollow core area of ​​the optical fiber, and the signal light in the hollow-core optical fiber maintains single-mode transmission; lens optical fiber 3, a conical or spherical lens is polished on the end face of the single-mode optical fiber, which has the function of converging the light beam and is used to converge the spatial light emitted from the end face of the hollow-core optical fiber; fiber grating 4, a grating structure with different refractive indices is periodically etched on the single-mode optical fiber, which is used to reflect signal light, and the reflectivity is greater than 70%.

[0027] The inner diameter of the quartz capillary is equivalent to the outer diameter of the hollow core optical fiber after the coating layer is stripped, and the inner diameter of the quartz capillary is 5 to 10 μm.

[0028] Alkali metal atoms are used as the working medium in the hollow-core optical fiber, and the buffer gas is used to increase the atomic spin relaxation time of the hollow-core optical fiber.

[0029] Single-mode optical fiber, hollow-core optical fiber, lensed optical fiber, and fiber Bragg grating are all made of silica and include a core layer and a cladding.

[0030] The signal light is introduced into the hollow-core optical fiber 2 from the single-mode optical fiber 1, and diverges in the form of a Gaussian beam at the end face of the hollow-core optical fiber 2. After spatial transmission, it is focused and converged at the incident end face of the lens optical fiber 3, enters the interior of the lens optical fiber 3, and finally the optical path is reflected at the fiber grating 4, re-enters the space and the hollow-core optical fiber 2.

[0031] like Figure 2 As shown, this embodiment also provides a method for preparing a reflective hollow core optical fiber atomic gas chamber, the method comprising:

[0032] The single-mode optical fiber 1 and the hollow-core optical fiber 2 are fused and connected to form a single-mode optical fiber-hollow-core optical fiber assembly;

[0033] The lens fiber 3 and the fiber grating 4 are fused and connected to form a lens fiber-fiber grating assembly;

[0034] Place the hollow-core optical fiber 2 in the single-mode optical fiber-hollow-core optical fiber assembly into one end of the quartz capillary 5; fix and seal the hollow-core optical fiber 2 and one end of the quartz capillary 5. The single-mode optical fiber-hollow-core optical fiber assembly is placed into one end of the quartz capillary 5, with one end of the hollow-core optical fiber 2 on the inside, and the hollow-core optical fiber segment is laser bonded to the quartz capillary to complete the fixation and sealing;

[0035] Place the lens fiber-FBG assembly into the other end of the quartz capillary 5, adjust the lens fiber-FBG assembly and fix it with the quartz capillary 5 by spot welding; wherein, the lens fiber-FBG assembly is placed into the other end of the quartz capillary 5, the lens fiber 3 is on the inner side, the lens fiber-FBG assembly is coaxial and close to the single-mode fiber-hollow core fiber assembly, and is adjusted with high precision and fixed by spot welding;

[0036] The quartz capillary 5 is connected to the vacuum filling system, and leak detection, vacuuming, and filling with alkali metal atoms and buffer gas are performed through the vacuum filling system;

[0037] The other end of the quartz capillary 5 is sealed to obtain a reflective hollow-core optical fiber atomic gas chamber; wherein, the outer side of the optical fiber grating spot welding point in the quartz capillary 5 is sealed and the assembly is removed as a whole; a reflective hollow-core optical fiber atomic gas chamber sample is obtained.

[0038] The fusion-joining of the single-mode optical fiber 1 and the hollow-core optical fiber 2 includes: tapering the hollow-core optical fiber 2 or reverse tapering the single-mode optical fiber 1 to match the mode field sizes of the two, and laser welding after the end faces are neatly cut.

[0039] Fixing and sealing the hollow-core optical fiber 2 and one end of the quartz capillary 5 include: neatly cutting the end faces of the hollow-core optical fiber 2 and the end faces of the quartz capillary 5, inserting the fused single-mode optical fiber-hollow-core optical fiber assembly into the quartz capillary, placing one end of the hollow-core optical fiber inside the quartz capillary, and using a fiber fusion splicer to perform laser bonding and fusion splicing to achieve the fixation and sealing of the quartz capillary 5 and the hollow-core optical fiber 2.

[0040] like Figure 3 As shown, the lens fiber-fiber Bragg grating assembly is placed into the other end of the quartz capillary 5, and the lens fiber-fiber Bragg grating assembly is adjusted and fixed with the quartz capillary 5 by spot welding, including:

[0041] The lens optical fiber 3 connected to the optical fiber grating 4 is placed on the six-dimensional adjustment frame 10;

[0042] Insert one end of the single-mode optical fiber 1 into one end of the bare fiber adapter;

[0043] Connect the other end of the bare fiber adapter to the second port 8 of the optical fiber circulator, connect the first port 7 of the optical fiber circulator to the laser, and connect the third port 9 of the optical fiber circulator to the optical power meter;

[0044] The laser emits a beam of light, and the knob 10 of the six-dimensional adjustment frame is turned to adjust the position of the lens fiber-fiber Bragg grating assembly, and the reading of the optical power meter is monitored synchronously;

[0045] When the optical power meter shows the maximum value, the lens fiber-fiber Bragg grating assembly is fixed in the quartz capillary by spot welding.

[0046] The specific steps of the hollow core optical fiber air chamber assembly method are as follows.

[0047] A special optical fiber fusion splicer is used to tape and fuse the single-mode optical fiber and the hollow-core optical fiber. The hollow-core optical fiber 2 is tapered or the single-mode optical fiber 1 is reversely tapered to match the mode field sizes of the two. After the end faces are neatly cut, laser fusion is performed to achieve fusion connection between the single-mode optical fiber 1 and the hollow-core optical fiber 2 to form a single-mode optical fiber-hollow-core optical fiber combination.

[0048] The lens fiber 3 and the fiber grating 4 are fused and butt-jointed to form a lens fiber-fiber grating assembly.

[0049] The end faces of the hollow-core optical fiber 2 and the quartz capillary 5 are cut neatly, and the fused single-mode optical fiber-hollow-core optical fiber assembly is inserted into the quartz capillary 5. One end of the hollow-core optical fiber 2 is placed inside the quartz capillary 5, and the quartz capillary 5 and the hollow-core optical fiber 2 are fixed and sealed by laser bonding and fusion using an optical fiber fusion splicer.

[0050] The lens fiber-FBG assembly is placed into the other end of the quartz capillary 5, with the lens fiber 3 on the inside. The lens fiber-FBG assembly is coaxial and close to the single-mode fiber-hollow core fiber assembly, and the single-mode fiber connected to the FBG 4 is placed on the six-dimensional adjustment frame 10. One end of the single-mode fiber 1 in the single-mode fiber-hollow core fiber assembly is inserted into the bare fiber adapter. Port 1 7 of the fiber circulator is connected to the laser, port 2 8 is connected to the bare fiber adapter with the single-mode fiber inserted, and port 3 9 is connected to the optical power meter. The laser emits a beam of light, and the knob of the six-dimensional adjustment frame 10 is turned to adjust the position of the lens fiber-FBG assembly, and the optical power meter reading is monitored synchronously. When the optical power meter reading reaches the maximum value, the lens fiber-FBG assembly is fixed in the quartz capillary 5 by spot welding.

[0051] The quartz capillary 5 is connected to the vacuum filling system for leak detection, vacuuming, and filling with alkali metal atoms 6 and buffer gas;

[0052] The outer side of the spot welding position of the optical fiber Bragg grating 4 in the quartz capillary 5 is sealed and the assembly is removed as a whole;

[0053] The reflective hollow-core optical fiber atomic gas chamber sample was obtained.

[0054] This embodiment uses a fiber grating to reflect the signal light from the incident end, and the signal light enters the hollow-core fiber segment twice; compared with the transmission-type hollow-core fiber chamber that requires the use of two segments of hollow-core fiber, the reflective hollow-core fiber chamber assembly scheme reduces the sample preparation cost and improves assembly efficiency; the working gas filling direction of this embodiment is parallel to the hollow-core fiber direction, which is more conducive to the filling of the working gas and the diffusion in the sample; this embodiment is directly filled through a quartz capillary equipped with a single-mode fiber-hollow-core fiber assembly and a lens fiber-fiber grating assembly, without generating other branches, and the volume is determined by the outer diameter and length of the quartz capillary, which is conducive to the miniaturization of the sample; the working area of ​​the reflective hollow-core fiber chamber of this embodiment is located at the end of the sample, which is more conducive to use as a probe in measurement fields such as fiber gas sensing and precision optical sensing.

[0055] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A reflective hollow-core optical fiber atomic gas chamber, characterized in that include: A single-mode optical fiber (1), a hollow-core optical fiber (2), a lens optical fiber (3), an optical fiber grating (4) and a quartz capillary (5); wherein: The single-mode optical fiber (1) is connected to the hollow-core optical fiber (2); The lens optical fiber (3) and the optical fiber grating (4) are connected; The hollow core optical fiber (2), the lens optical fiber (3) and the optical fiber grating (4) are all located in the quartz capillary (5); The quartz capillary (5) is filled with alkali metal atoms (6) and buffer gas.

2. The reflective hollow-core optical fiber atomic gas chamber according to claim 1, characterized in that: The core of the single-mode optical fiber (1) is 8 to 10 μm, and the single-mode optical fiber (1) propagates only one mode; The inner layer of the hollow core optical fiber (2) is hollow, the air core diameter of the hollow core optical fiber (2) is 5 to 100 μm, and the hollow core optical fiber (2) is used to accommodate alkali metal atoms; The incident end of the lens optical fiber (3) is a conical or spherical lens, which has the function of converging the light beam; The reflectivity of the optical fiber grating (4) is greater than 70%.

3. The reflective hollow-core optical fiber atomic gas chamber according to claim 1, characterized in that: The inner diameter of the quartz capillary (5) is 5 to 10 μm.

4. The reflective hollow-core optical fiber atomic gas chamber according to claim 1, characterized in that: Alkali metal atoms are used as the working medium in the hollow-core optical fiber, and the buffer gas is used to increase the atomic spin relaxation time of the hollow-core optical fiber.

5. The reflective hollow core optical fiber atomic gas chamber according to claim 1, characterized in that: The single-mode optical fiber (1), the hollow-core optical fiber (2), the lens optical fiber (3) and the optical fiber grating (4) are all made of silica.

6. The reflective hollow core optical fiber atomic gas chamber according to claim 1, characterized in that: The signal light is introduced into the hollow core optical fiber (2) from the single mode optical fiber (1), and is diverged in the form of a Gaussian beam at the end face of the hollow core optical fiber (2). After being transmitted through space, the signal light is focused and bundled at the incident end face of the lens optical fiber (3), and enters the interior of the lens optical fiber (3). Finally, the light path is reflected at the fiber grating (4), and re-enters the space and the hollow core optical fiber (2).

7. A method for preparing a reflective hollow-core optical fiber atomic gas cell according to any one of claims 1 to 6, characterized in that include: The single-mode optical fiber (1) and the hollow-core optical fiber (2) are fused and connected to form a single-mode optical fiber-hollow-core optical fiber assembly; The lens optical fiber (3) and the optical fiber grating (4) are fused and connected to form a lens optical fiber-optical fiber grating assembly; The hollow core optical fiber (2) in the single-mode optical fiber-hollow core optical fiber assembly is placed into one end of a quartz capillary (5); the hollow core optical fiber (2) and one end of the quartz capillary (5) are fixed and sealed; The lens fiber-fiber Bragg grating assembly is placed into the other end of the quartz capillary (5), and the lens fiber-fiber Bragg grating assembly is adjusted and fixed to the quartz capillary (5) by spot welding; wherein the lens fiber (3) is opposite to the hollow core fiber (2), and the lens fiber-fiber Bragg grating assembly is coaxial with the single-mode fiber-hollow core fiber assembly; Connecting the quartz capillary (5) to a vacuum filling system, and performing leak detection, vacuuming, and filling with alkali metal atoms and buffer gas through the vacuum filling system; The other end of the quartz capillary (5) is sealed by fusion to obtain a reflective hollow-core optical fiber atomic gas chamber.

8. The preparation method according to claim 7, characterized in that: The method of fusion-jointing a single-mode optical fiber (1) and a hollow-core optical fiber (2) comprises: The hollow core optical fiber (2) is tapered or the single mode optical fiber (1) is reversely tapered to match the mode field sizes of the two, and laser welding is performed after the end faces are neatly cut.

9. The preparation method according to claim 7, characterized in that: Fixing and sealing the hollow core optical fiber (2) and one end of the quartz capillary (5) comprises: The fused single-mode optical fiber-hollow-core optical fiber assembly is inserted into a quartz capillary, one end of the hollow-core optical fiber is placed inside the quartz capillary, and the quartz capillary (5) and the hollow-core optical fiber (2) are fixed and sealed by laser bonding and fusion using an optical fiber fusion splicer.

10. The preparation method according to claim 7, characterized in that: Placing the lens fiber-optic fiber grating assembly into the other end of the quartz capillary (5), adjusting the lens fiber-optic fiber grating assembly and fixing it with the quartz capillary (5) by spot welding, including: Placing the lens optical fiber (3) connected to the optical fiber grating (4) on a six-dimensional adjustment frame (10); Insert one end of the single-mode optical fiber (1) into one end of the bare fiber adapter; Connect the other end of the bare fiber adapter to the second port (8) of the optical fiber circulator, connect the first port (7) of the optical fiber circulator to the laser, and connect the third port (9) of the optical fiber circulator to the optical power meter; The laser emits a beam of light, and the knob of the six-dimensional adjustment frame (10) is turned to adjust the position of the lens optical fiber-optical fiber grating assembly, and the reading of the optical power meter is monitored synchronously; When the optical power meter shows a maximum value, the lens fiber-fiber Bragg grating assembly is fixed in the quartz capillary by spot welding.

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