Anti-resonance optical fiber structure applied to middle and far infrared bands and preparation method

Abstract

The invention discloses an anti-resonance optical fiber structure applied to middle and far infrared bands and a preparation method, the anti-resonance optical fiber structure comprises an outer cladding sleeve, and the outer cladding sleeve is the outermost layer of the anti-resonance optical fiber structure; a fiber core area, wherein the fiber core area is concentrically nested in the outer cladding sleeve; the anti-resonance element is arranged between the fiber core area and the outer cladding sleeve and comprises a semicircular pipe and a supporting arm assembly, the arc-shaped section of the semicircular pipe is arranged close to the fiber core area, and the other side of the semicircular pipe is attached to the inner wall of the outer cladding sleeve through the supporting arm assembly. According to the anti-resonance optical fiber structure, through structural optimization, low-loss, large-mode-area and low-loss laser transmission can be achieved within the wavelength range of 8-12 microns, and the preparation method provides an effective solution thought for preparing the hollow-core anti-resonance optical fiber of an unconventional tubular structure at low cost.

Description

Technical Field

[0001] The present invention relates to the field of optical fiber technology, and in particular to an anti-resonance optical fiber structure and a preparation method for use in mid- and far-infrared bands. Background Art

[0002] The mid-to-far infrared band of 8-12μm is in one of the windows of the atmosphere. Lasers working in this band are widely used in civil fields such as environmental monitoring, material processing, and biomedicine, as well as military fields such as laser weapons and optoelectronic confrontation due to their excellent atmospheric transmission characteristics. With the rapid development of laser technology, mid-to-far infrared laser sources have made great progress in output power, wavelength range, pulse energy, etc., and are gradually developing in the direction of miniaturization, flexibility, and flexible transmission.

[0003] Mid-infrared and far-infrared transmission optical fibers can improve the reliability, compactness and flexibility of optical systems. Limited by the optical transmittance characteristics of glass materials, the current mid-infrared and far-infrared transmission optical fiber materials are mainly chalcogenide glass. At present, step-index chalcogenide mid-infrared and far-infrared transmission optical fibers are difficult to meet the needs of high-power mid-infrared and far-infrared laser transmission due to intrinsic factors such as low damage threshold and high nonlinearity of chalcogenide glass, as well as high loss and high preparation cost. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention provides an antiresonant optical fiber structure and a preparation method for use in the mid- and far-infrared bands. The antiresonant optical fiber structure can achieve low-loss, large mode field area and low-loss laser transmission in the wavelength range of 8 to 12 μm through structural optimization. The preparation method provides an effective solution for the low-cost preparation of hollow-core antiresonant optical fibers with unconventional tubular structures.

[0005] An anti-resonance optical fiber structure for use in mid- and far-infrared bands, comprising:

[0006] An outer cladding sleeve, wherein the outer cladding sleeve is the outermost layer of the anti-resonance optical fiber structure;

[0007] A fiber core region, wherein the fiber core region is concentrically nested in the outer cladding sleeve;

[0008] An anti-resonance element is arranged between the core region and the outer cladding sleeve, and comprises a semicircular tube and a support arm assembly. The arc section of the semicircular tube is arranged close to the core region, and the other side of the semicircular tube is attached to the inner wall of the outer cladding sleeve through the support arm assembly.

[0009] As a preferred embodiment of the above technical solution, the support arm assembly includes a transverse support arm and a longitudinal support arm, the longitudinal support arms are provided in two groups in parallel, the two groups of longitudinal support arms are respectively connected to a free end of the semicircular tube, the transverse support arm is vertically arranged between the two groups of longitudinal support arms, and the cross-section of the anti-resonance element composed of the semicircular tube, the transverse support arm and the longitudinal support arm is window-shaped.

[0010] As a preferred embodiment of the above technical solution, the anti-resonance elements are arranged in an annular array with equal intervals around the core region, and adjacent anti-resonance elements do not contact each other.

[0011] As a preferred embodiment of the above technical solution, the semicircular tube is arranged tangent to the fiber core area.

[0012] As a preferred embodiment of the above technical solution, the refractive index of the core region is lower than the refractive index of the outer cladding sleeve and the anti-resonance element, and the core region is evacuated or uses any one of gas and liquid as the transmission medium.

[0013] As a preferred embodiment of the above technical solution, the outer cladding sleeve and the anti-resonance element are made of any one material of multi-system chalcogenide glasses such as S-based, Se-based and Te-based.

[0014] As a preferred embodiment of the above technical solution, the inner diameter of the outer cladding sleeve is in the range of 420 to 600 μm, and the outer diameter is in the range of 520 to 770 μm.

[0015] As a preferred embodiment of the above technical solution, the diameter of the core region ranges from 180 to 250 μm, and the ratio of the inner diameter of the semicircular tube to the diameter of the core region ranges from 0.6 to 0.9.

[0016] As a preferred embodiment of the above technical solution, the length of the longitudinal support arm ranges from 50 to 80 μm, the number of the transverse support arms is 1 to 3, and the thickness of the semicircular tube, transverse support arm and longitudinal support arm is within the third resonance region or the fourth resonance region.

[0017] A method for preparing an antiresonant optical fiber structure for use in mid- and far-infrared bands as described above, the preparation process being:

[0018] Step 1: Design and prepare the extrusion die. The extrusion die is designed and processed in proportion to the simulated optical fiber structure, and the structured die is processed by CNC machine tools or metal 3D printing.

[0019] Step 2, preparing an optical fiber preform based on an integrated extrusion method or a segmented extrusion method,

[0020] The optical fiber preform is extruded into an integral shape by using an integrated extrusion method. The high-temperature softened glass material is squeezed through the designed integrated mold outlet by controlling the extrusion rod to directly prepare a complete structure preform.

[0021] The segmented extrusion method is adopted to extrude each discrete component separately and then stack them into preform rods.

[0022] Step 3, precision annealing the preform rod prepared by extrusion in step 2 to release the stress inside the preform rod generated during the extrusion process;

[0023] Step 4, placing the preform obtained in step 3 on a drawing tower for drawing, adjusting the drawing parameters to change the wall thickness, size, spacing, etc. of the anti-resonance element to obtain an optical fiber of the desired size, and forming a polymer coating on the outer surface of the optical fiber.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] The sulfide hollow-core antiresonant optical fiber designed by the present invention for use in the mid- and far-infrared bands has low transmission loss. In terms of optical fiber structure design, the stability of the antiresonant element can be effectively increased by adding longitudinal support arms and transverse support arms, and the limiting loss and high-order mode suppression ratio can be further reduced by increasing the number of transverse support arms. After the above structural optimization, the limiting loss is simulated at 10.6μm to be 0.00562dB / m. In terms of optical fiber preparation, the extrusion method can prepare optical fiber preforms with complex structures in a single step, and further draw optical fibers of the required size in a drawing tower, providing an effective solution for the low-cost preparation of hollow-core antiresonant optical fibers with unconventional tubular structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the cross-sectional structure of the anti-resonance optical fiber structure disclosed in the present invention.

[0027] Figure 2 This is a schematic diagram of the results of the limiting loss changing with the anti-resonance wall thickness obtained by simulation calculation using the finite element analysis method disclosed in the present invention.

[0028] Figure 3 It is a schematic diagram of calculation results of limiting loss, absorption loss and total loss of the optimized designed window-type chalcogenide hollow-core antiresonant optical fiber disclosed in the present invention within the wavelength range of 9.5 to 11.5 μm;

[0029] Figure 4 It is a schematic diagram of the calculation results of the comparison of the limiting loss of the optimized window-type chalcogenide hollow-core antiresonant optical fiber disclosed in the present invention with that of the single tube ring and single arch optical fiber structures in the range of 8 to 12 μm;

[0030] Figure 5This is a schematic diagram of changing the length and position of the longitudinal support arm and the transverse support arm disclosed in the present invention;

[0031] Figure 6 It is a schematic diagram of the calculation results of the limiting loss disclosed in the present invention as the position hc of the lateral support arm changes;

[0032] Figure 7 After optimizing the number of lateral support arms disclosed in the present invention, the LP at 10.6 μm 21 Schematic diagram of the mode field distribution of the mode;

[0033] Figure 8 It is a schematic diagram of the preparation process of a chalcogenide hollow-core antiresonant optical fiber in the mid- and far-infrared bands based on an extrusion-stretching method disclosed in the present invention;

[0034] The reference numerals are as follows: 1 - outer cladding sleeve, 2 - core region, 3 - anti-resonance element, 4 - semicircular tube, 5 - transverse support arm, 6 - longitudinal support arm. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0037] like Figure 1 An anti-resonance optical fiber structure for use in mid- and far-infrared bands is shown, comprising:

[0038] An outer cladding sleeve 1, wherein the outer cladding sleeve 1 is the outermost layer of the anti-resonance optical fiber structure;

[0039] A fiber core region 2, wherein the fiber core region 2 is concentrically nested in the outer cladding sleeve 1;

[0040] The anti-resonance element 3 is arranged between the core region 2 and the outer cladding sleeve 1, and includes a semicircular tube 4 and a support arm assembly. The arc section of the semicircular tube 4 is arranged close to the core region 2, and the other side of the semicircular tube 4 is attached to the inner wall of the outer cladding sleeve 1 through the support arm assembly.

[0041] In this embodiment, the support arm assembly includes a transverse support arm 5 and a longitudinal support arm 6. The longitudinal support arms 6 are provided in two groups in parallel. The two groups of longitudinal support arms 6 are respectively connected to a free end of the semicircular tube 4. The transverse support arm 5 is vertically arranged between the two groups of longitudinal support arms 6. The cross-section of the anti-resonance element 3 composed of the semicircular tube 4, the transverse support arm 5 and the longitudinal support arm 6 is window-shaped.

[0042] In this embodiment, the anti-resonance elements 3 are arranged in a circular array with equal spacing around the core region 2 , and adjacent anti-resonance elements 3 are not in contact with each other.

[0043] In this embodiment, the semicircular tube 4 is arranged tangent to the fiber core region 2 .

[0044] In this embodiment, the refractive index of the core region 2 is lower than the refractive indexes of the outer cladding tube 1 and the anti-resonance element 3 , and the core region 2 is evacuated or uses any one of gas and liquid as the transmission medium.

[0045] In this embodiment, the outer cladding tube 1 and the anti-resonance element 3 are made of any one of the multi-system chalcogenide glasses such as S-based, Se-based and Te-based.

[0046] In this embodiment, the inner diameter of the outer cladding sleeve 1 ranges from 420 to 600 μm, and the outer diameter ranges from 520 to 770 μm.

[0047] In this embodiment, the diameter of the core region 2 is in the range of 180 to 250 μm, and the ratio of the inner diameter of the semicircular tube 4 to the diameter of the core region 2 is in the range of 0.6 to 0.9.

[0048] In this embodiment, the length of the longitudinal support arm 6 is in the range of 50 to 80 μm, the number of the transverse support arms 5 is 1 to 3, and the thickness of the semicircular tube 4, the transverse support arm 5, and the longitudinal support arm 6 are in the third resonance region or the fourth resonance region, wherein, when in the third resonance region, the thickness range is 5.3 to 6.3 μm; when in the fourth resonance region, the thickness range is 7.4 to 8.6 μm.

[0049] A method for preparing an antiresonant optical fiber structure for use in mid- and far-infrared bands as described above, the preparation process being:

[0050] Step 1: Design and prepare the extrusion die. The extrusion die is designed and processed in proportion to the simulated optical fiber structure, and the structured die is processed by CNC machine tools or metal 3D printing.

[0051] Step 2, preparing an optical fiber preform based on an integrated extrusion method or a segmented extrusion method,

[0052] The optical fiber preform is extruded into an integral shape by using an integrated extrusion method. The high-temperature softened glass material is squeezed through the designed integrated mold outlet by controlling the extrusion rod to directly prepare a complete structure preform.

[0053] The segmented extrusion method is adopted to extrude each discrete component separately and then stack them into preform rods.

[0054] Step 3, precision annealing the preform rod prepared by extrusion in step 2 to release the stress inside the preform rod generated during the extrusion process;

[0055] Step 4, placing the preform obtained in step 3 on a drawing tower for drawing, adjusting the drawing parameters to change the wall thickness, size, spacing, etc. of the anti-resonance element to obtain an optical fiber of the desired size, and forming a polymer coating on the outer surface of the optical fiber.

[0056] The number of anti-resonance elements 3 is preferably 5-8. This embodiment is described with 6 anti-resonance elements. In this embodiment, the simulation optimization design of the outer cladding sleeve 1 and the anti-resonance element 3 adopts Ge 28 Sb 12 Se 60 Chalcogenide glass, the transmission medium of the core region 2 is air.

[0057] The wall thickness is selected according to the anti-resonance reflection optical waveguide model. The anti-resonance wall thickness calculation formula is as follows:

[0058]

[0059] Wherein, t represents the wall thickness of the anti-resonance element 3, λ represents the designed operating wavelength, and n 2 and n 1 are the refractive index of the chalcogenide glass material and the refractive index of the core region 2 respectively, and m is an integer.

[0060] In this embodiment, the finite element method is used for design modeling analysis to calculate the change of the limiting loss of the optical fiber at a wavelength of 10.6 μm with the anti-resonance wall thickness, such as Figure 2 As shown, the calculation result is consistent with the anti-resonance wall thickness calculation formula, and the wall thickness t in the range of 5.5μm and 7.7μm is selected as the optimal wall thickness.

[0061] The design advantages of the present invention are described below in conjunction with the accompanying drawings:

[0062] 1. Figure 1 The present invention discloses an anti-resonance optical fiber structure design for use in mid- and far-infrared bands; Figure 3As shown in the figure, the calculation results of the limiting loss, absorption loss and total loss in the wavelength range of 9.5 to 11.5 μm are shown. The limiting loss is 0.00562 dB / m at a wavelength of 10.6 μm. The absorption loss of the optical fiber is calculated by the modal overlap. The limiting loss plus the absorption loss can be defined as the total transmission loss of the optical fiber, that is, the theoretical transmission loss is only 0.0075 dB / m at 10.6 μm. This shows that the chalcogenide hollow-core antiresonant optical fiber designed by the present invention has a lower transmission loss in the mid- and far-infrared bands.

[0063] 2. Figure 4 The figure is a schematic diagram of the calculation results of the optimized window-type chalcogenide hollow-core antiresonant optical fiber disclosed in the invention, which is compared with the limiting loss of the single tube ring and single arched optical fiber structure in the range of 8 to 12 μm. It can be seen that the addition of the lateral support arm 5 has greatly improved the loss. Compared with the ordinary single-layer tube ring structure, the window-type antiresonant hollow-core optical fiber greatly reduces the limiting loss of the optical fiber by about an order of magnitude.

[0064] 3. Figure 5 According to the schematic diagram of changing the length and position of the longitudinal support arm 6 and the transverse support arm 5 disclosed in the invention, the length h of the longitudinal support arm 6 and the position hc of the transverse support arm 5 in the anti-resonance element 3 can be adjusted so that the effective refractive index of the tube mode is equal to that of the first high-order mode of the fiber core, the modes are matched, and the high-order modes leak into the anti-resonance element 3, thereby regulating the ability of the optical fiber to suppress high-order modes.

[0065] 4. Figure 6 It is a schematic diagram of the calculation results of the limiting loss disclosed in the present invention as the position hc of the lateral support arm 5 changes. As the position of the lateral support arm 5 moves away from the core region 2, that is, as the area of ​​the arched region in the window structure close to the core region 2 increases, the fundamental mode limiting loss at a wavelength of 10.6μm remains almost unchanged, the coupling between the core mode and the cladding mode reaches a maximum when hc is 40μm-50μm, the loss of the first high-order mode reaches a maximum, and the high-order mode suppression ratio (HOMER) reaches a maximum (>1000), indicating that this effectively realizes low-loss single-mode transmission.

[0066] 5. Figure 7 It is a schematic diagram of the mode field distribution of the LP21 mode at a wavelength of 10.6 μm after optimizing the number of transverse support arms 5 disclosed in the present invention, indicating that the high-order modes are well confined in the core area; it can be seen that the anti-resonance element 3 area can be further divided by increasing the number of transverse support arms 5, and the fundamental mode limitation loss can be reduced by adding anti-resonance layers while avoiding the coupling of high-order modes; this structural design provides an effective solution for the design of chalcogenide hollow-core anti-resonance optical fiber structures in the mid- and far-infrared bands for multi-mode transmission.

[0067] 6. Figure 8The present invention discloses a preparation process of a chalcogenide hollow-core antiresonant optical fiber in the mid- and far-infrared bands based on an extrusion and stretching method. A mold containing a chalcogenide glass blank is fixed on an extrusion tower, the mold is heated to fully soften the glass in the mold, and then a suitable extrusion force is applied to the chalcogenide glass, the glass is extruded through the mold, and an external force is applied to the extruded preform rod to obtain an optical fiber preform rod of a designed structure in a single step; the extruded preform rod is annealed to remove the stress generated during the extrusion process; finally, the preform rod is placed on a drawing tower for drawing, and the drawing parameters such as the fiber drawing tower temperature, the rod feeding and pulling speed, the gas pressure of the fiber core and the cladding, etc. are adjusted to change the wall thickness, size, spacing, etc. of the antiresonant element 3 to obtain an optical fiber of a desired size, and a polymer coating is formed on the outer surface of the optical fiber.

[0068] The above method obtains a chalcogenide hollow-core antiresonant optical fiber in the mid- and far-infrared bands, which has low loss and excellent laser transmission performance. The preparation technology has greater flexibility and can be used for flexible transmission of high-power mid- and far-infrared lasers.

[0069] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An anti-resonant optical fiber structure for use in mid- and far-infrared bands, characterized in that: include An outer cladding sleeve, wherein the outer cladding sleeve is the outermost layer of the anti-resonance optical fiber structure; A fiber core region, wherein the fiber core region is concentrically nested in the outer cladding sleeve; An anti-resonance element is arranged between the core region and the outer cladding sleeve, and comprises a semicircular tube and a support arm assembly. The arc section of the semicircular tube is arranged close to the core region, and the other side of the semicircular tube is attached to the inner wall of the outer cladding sleeve through the support arm assembly.

2. The anti-resonance optical fiber structure for use in the mid- and far-infrared bands according to claim 1, characterized in that: The support arm assembly includes a transverse support arm and a longitudinal support arm. The longitudinal support arms are arranged in two groups in parallel. The two groups of longitudinal support arms are respectively connected to a free end of the semicircular tube. The transverse support arm is vertically arranged between the two groups of longitudinal support arms. The cross-section of the anti-resonance element composed of the semicircular tube, the transverse support arm and the longitudinal support arm is window-shaped.

3. The anti-resonance optical fiber structure for use in the mid- and far-infrared bands according to claim 1, characterized in that: The anti-resonance elements are arranged in an annular array with equal spacing around the core region, and adjacent anti-resonance elements are not in contact with each other.

4. The anti-resonance optical fiber structure for use in the mid- and far-infrared bands according to claim 1, characterized in that: The semicircular tube is arranged tangent to the fiber core region.

5. The anti-resonance optical fiber structure for use in the mid- and far-infrared bands according to claim 1, characterized in that: The refractive index of the core region is lower than the refractive indexes of the outer cladding tube and the anti-resonance element, and the core region is evacuated or uses any one of gas and liquid as a transmission medium.

6. The anti-resonance optical fiber structure for use in mid- and far-infrared bands according to claim 1, characterized in that: The outer cladding tube and the anti-resonance element are made of any one material of multi-system chalcogenide glasses such as S-based, Se-based and Te-based.

7. The anti-resonance optical fiber structure for use in mid- and far-infrared bands according to claim 1, characterized in that: The inner diameter of the outer cladding sleeve is in the range of 420 to 600 μm, and the outer diameter is in the range of 520 to 770 μm.

8. The anti-resonance optical fiber structure for use in the mid- and far-infrared bands according to claim 1, characterized in that: The diameter of the core region is in the range of 180 to 250 μm, and the ratio of the inner diameter of the semicircular tube to the diameter of the core region is in the range of 0.6 to 0.

9.

9. The anti-resonance optical fiber structure for use in the mid- and far-infrared bands according to claim 1, characterized in that: The length of the longitudinal support arm ranges from 50 to 80 μm, the number of the transverse support arms is 1 to 3, and the thickness of the semicircular tube, the transverse support arm, and the longitudinal support arm is within the third resonance region or the fourth resonance region.

10. A method for preparing an antiresonant optical fiber structure for use in mid- and far-infrared bands as described in any of 1 to 9, characterized in that: The preparation process is: Step 1: Design and prepare the extrusion die. The extrusion die is designed and processed in proportion to the simulated optical fiber structure, and the structured die is processed by CNC machine tools or metal 3D printing. Step 2, preparing an optical fiber preform based on an integrated extrusion method or a segmented extrusion method, The optical fiber preform is extruded into an integral shape by using an integrated extrusion method. The high-temperature softened glass material is squeezed through the designed integrated mold outlet by controlling the extrusion rod to directly prepare a complete structure preform. The segmented extrusion method is adopted to extrude each discrete component separately and then stack them into preform rods. Step 3, precision annealing the preform rod prepared by extrusion in step 2 to release the stress inside the preform rod generated during the extrusion process; Step 4, placing the preform obtained in step 3 on a drawing tower for drawing, adjusting the drawing parameters to change the wall thickness, size, spacing, etc. of the anti-resonance element to obtain an optical fiber of the desired size, and forming a polymer coating on the outer surface of the optical fiber.

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