A mid-infrared composite glass optical fiber and a method for manufacturing the same

Abstract

The application discloses a kind of middle wave infrared composite glass optical fiber and preparation method thereof, and the composite glass optical fiber is composed of fluoride glass core, fluoride glass inner cladding, chalcogenide glass outer cladding, polymer coating layer and infrared end cap.The difference between the thermal expansion coefficient of fluoride glass used for core, fluoride glass used for inner cladding and chalcogenide glass used for outer cladding is less than or equal to 4×10 ‑6 The temperature interval of any two of them has overlap. First, the fluoride glass rod of core is prepared by using melt quenching technology, then the inner cladding fluoride glass sleeve and outer cladding chalcogenide glass sleeve are prepared by using spin tube technology, then the optical fiber is drawn by using rod-in-tube method, and finally the infrared end cap is fused with the optical fiber. The composite glass optical fiber can effectively avoid the fluoride glass core and inner cladding from being eroded by water vapor in the air, thereby significantly improving the 3-5 μm laser power that can be transmitted by the optical fiber and greatly prolonging the service life thereof; the preparation method has low requirement on drawing equipment and low cost.

Description

Technical Field

[0001] This invention belongs to the field of infrared optical fiber materials, and relates to a mid-wave infrared composite glass optical fiber that operates in the 3-5μm band and its preparation method. Background Technology

[0002] The 3–5 μm mid-wave infrared band lies within the low-loss window of the atmosphere and is the primary detection band for infrared search and tracking. It also encompasses the fingerprint absorption spectra of a large number of molecules. Therefore, 3–5 μm mid-wave infrared laser technology has significant application value in fields such as optoelectronic countermeasures, atmospheric remote sensing, and medical health. Mid-wave infrared glass fiber has advantages such as small size, light weight, and high transmission efficiency, enabling flexible laser transmission and facilitating the compact design of devices and equipment. It is considered an ideal 3–5 μm laser transmission medium.

[0003] Currently, mid-wave infrared glass fibers mainly include tellurate glass fibers, fluoride glass fibers, and chalcogenide glass fibers (including sulfide, selenide, and telluride glass fibers). Their infrared cutoff wavelengths are ~4μm, ~5μm, and ~6.5μm (sulfide glass fibers), respectively, and their damage thresholds under continuous laser irradiation are ~100MW / cm². 2 ~40MW / cm 2 ~10-20MW / cm 2 (Chalcogenide glass fiber). Although tellurate glass fiber has high resistance to laser damage, its high phonon energy limits its application to wavelengths below 4 μm. Furthermore, the OH impurities in tellurate glass are extremely difficult to eliminate, making it difficult to achieve losses below 1 dB / m in the 3–4 μm band. Therefore, tellurate glass fiber is not suitable for transmitting high-power 3–5 μm lasers; its application in the mid-infrared band is mainly to utilize its high nonlinearity to generate lasers with wavelengths below 4 μm. In contrast, fluoride glass fiber and chalcogenide glass fiber have lower transmission losses in the 3–5 μm band, showing good potential for mid-infrared high-power laser transmission applications. LVF's InF3-based fluoride fiber has a loss of <0.1 dB / m in the 3–4.8 μm band, and according to reports, the highest mid-infrared continuous laser power transmitted by a ~10 μm core diameter single-mode InF3-based glass fiber is ~30 W. Among chalcogenide glass fibers, chalcogenide glass fibers have the highest resistance to laser damage. The typical loss of As-S chalcogenide glass fibers produced by IRflex in the United States is <0.1dB / m in the 3-5μm band (except for the SH impurity absorption band near 4.1μm). According to reports, the highest mid-wave infrared continuous laser power transmitted by a single-mode As-S glass fiber with a core diameter of ~10μm is ~10W.

[0004] Chalcogenide glass fibers have been widely used in the 3–5 μm band, excluding the 4.1 μm absorption band. Researchers have attempted various purification methods to eliminate SH impurities in the glass over the past few decades, achieving good results. However, the absorption loss near 4.1 μm due to residual SH impurities is still >1 dB / m. It is expected that completely eliminating SH impurities in optical fibers will be difficult in the short term. Compared to chalcogenide glass fibers, fluoride glass fibers have a higher laser damage threshold and achieve lower transmission loss in the 3–5 μm band, making them considered the most promising high-power mid-wave infrared laser transmission material. However, fluoride glass fibers have poor water resistance. Taking commonly used ZnF4-based and InF3-based fluoride glass fibers as examples, they are easily corroded by moisture in the air during prolonged use, especially when transmitting high-power lasers. Their end faces easily react with moisture in the air to form hydrogen bonds, which then rapidly diffuse into the fiber interior, causing damage within minutes. Currently, the main obstacle hindering the development and large-scale application of fluoride glass fibers is their poor water resistance. Summary of the Invention

[0005] To address the problems of poor water resistance and short service life of existing fluoride glass optical fibers, this invention provides a mid-wave infrared composite glass optical fiber and its preparation method by introducing chalcogenide glass with excellent moisture resistance as the outer cladding of the fluoride glass optical fiber and fusing infrared end caps with excellent moisture resistance to both ends of the optical fiber, thereby isolating the fluoride glass optical fiber material from air.

[0006] A mid-wave infrared composite glass fiber comprises, from the inside out, a core, an inner cladding, and an outer cladding; the core and the inner cladding are fluoride glass, and the outer cladding is chalcogenide glass.

[0007] Preferably, the difference in the coefficients of thermal expansion between any two of the fluoride glass used for the fiber core, the fluoride glass used for the inner cladding, and the chalcogenide glass used for the outer cladding is ≤4×10⁻⁶. -6 / K, the drawing temperature ranges of any two overlap.

[0008] Preferably, the refractive index n1 of the fiber core is greater than the refractive index n2 of the inner cladding.

[0009] Preferably, a polymer coating layer is also wrapped around the outer layer.

[0010] Preferably, the polymer coating is made of polyetherimide or polyethersulfone resin.

[0011] Preferably, infrared end caps are fused to both ends of the optical fiber.

[0012] Preferably, the fluoride glass is a ZrF4-based glass or an InF3-based glass.

[0013] Preferably, the composition of the chalcogenide glass includes one or two elements selected from germanium, arsenic, and antimony, and one or two elements selected from sulfur, selenium, and tellurium.

[0014] Preferably, the polymer coating material is polyetherimide or polyethersulfone resin.

[0015] The above-mentioned method for preparing mid-wave infrared composite glass optical fiber includes the following steps:

[0016] Step 1: Fluoride glass for optical fiber cores is synthesized in a platinum crucible under inert gas protection using a melt-quench technique, and then cold-processed into a core fluoride glass rod.

[0017] Step 2: Melt fluoride glass for the inner cladding of optical fibers in a platinum crucible protected by an inert gas, and obtain the inner cladding fluoride glass sleeve using a high-temperature spin tube technique.

[0018] Step 3: Chalcogenide glass for optical fiber cladding is synthesized in a vacuum quartz tube using a melt-quenching technique, and a chalcogenide glass sleeve for cladding is obtained using a high-temperature spin tube technique.

[0019] Step 4: Insert the fiber core fluoride glass rod into the inner cladding fluoride glass sleeve, then insert it into the outer cladding chalcogenide glass sleeve, and finally wrap the outer surface with a thin film polymer coating material to assemble the optical fiber preform.

[0020] Step 5: Draw the optical fiber preform into an optical fiber under inert gas protection;

[0021] Step 6: Cut a certain length of optical fiber and use an organic solvent to remove the polymer coating material at both ends of the optical fiber;

[0022] Step 7: Use a fiber optic fusion splicer to fusion splice both ends of the fiber to fibrous infrared end cap material (when the end cap material is glass), and then use a fiber optic cleaver to cut the infrared end cap material so that the end cap length at both ends of the fiber is <1mm; or use a fiber optic fusion splicer to fusion splice both ends of the fiber to infrared end cap material with a thickness of <1mm (when the end cap material is crystal), thus obtaining the required mid-wave infrared composite glass fiber.

[0023] The diameter of the fiber core fluoride glass rod matches the inner diameter of the inner cladding fluoride glass sleeve, and the outer diameter of the inner cladding fluoride glass sleeve matches the inner diameter of the outer cladding chalcogenide glass sleeve.

[0024] Preferably, the inert gas is nitrogen, argon, or helium.

[0025] Preferably, the organic solvent is dimethylacetamide or dichloromethane.

[0026] The concept of this invention is as follows:

[0027] Chalcogenide glasses possess excellent chemical stability, allowing them to be stored in air for many years without significant performance degradation, and even function underwater. The drawing temperature and coefficient of thermal expansion of chalcogenide glasses are similar to those of fluoride glasses. It can be anticipated that by selecting appropriate glass compositions, fluoride and chalcogenide glasses can be drawn together at the same temperature, while avoiding stress caused by mismatched coefficients of thermal expansion. Applying chalcogenide glass as an outer cladding to the surface of fluoride glass optical fibers can effectively protect them from moisture corrosion. Furthermore, to prevent moisture corrosion of the exposed fluoride core and inner cladding at both ends of the fiber, end-face protection can be achieved by fusion splicing infrared end caps with excellent moisture resistance and a high laser damage threshold. The infrared end cap is only <1mm long. Even if it suffers losses of tens of dB / m in the long-wavelength portion of the 3-5μm band, it will not have a significant adverse effect on the overall transmission performance of the optical fiber. Therefore, the end cap material can be an infrared material with a slightly smaller cutoff wavelength, a high laser damage threshold, and good water resistance, such as TeO2-based glass, AlF3-based glass, Al2O3 single crystal, and yttrium aluminum garnet single crystal.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] (1) The use of chalcogenide glass outer cladding and infrared end cap with excellent moisture resistance to isolate the fluoride glass fiber core and inner cladding used for laser transmission from the air can effectively prevent the fluoride glass fiber core and inner cladding inside the optical fiber from being corroded by water vapor in the air, thereby significantly improving the laser power that the optical fiber can transmit and greatly extending the service life of the optical fiber, which is expected to greatly promote the development and large-scale application of fluoride optical fiber.

[0030] (2) The infrared end cap used has a high laser damage threshold and also plays a role in expanding the laser beam and reducing the laser density, which can significantly improve the laser power that the fiber end face can withstand.

[0031] (3) Using high-temperature polyetherimide or polyethersulfone resin with high mechanical properties (usage temperature up to 200℃) instead of traditional UV-cured epoxy acrylate (usage temperature <100℃) as the coating layer of optical fiber can significantly improve the temperature resistance of optical fiber.

[0032] (4) The preparation method of the present invention has low requirements for wire drawing equipment and low cost. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the infrared composite glass fiber of the present invention.

[0034] In the figure, 1 is the fluoride glass fiber core, 2 is the fluoride glass inner cladding, 3 is the chalcogenide glass outer cladding, 4 is the polymer coating layer, and 5 is the infrared end cap. Detailed Implementation

[0035] The following embodiments further illustrate the content of the present invention, but should not be construed as limiting the present invention. Any modifications and substitutions made to the methods, steps, or conditions of the present invention without departing from the spirit and essence of the invention are within the scope of the present invention.

[0036] Unless otherwise specified, the technical means used in the embodiments are conventional means well known to those skilled in the art.

[0037] Example 1

[0038] like Figure 1 As shown, in this embodiment, the infrared composite glass fiber consists of a fluoride glass core 1, a fluoride glass inner cladding 2, a chalcogenide glass outer cladding 3, a polymer coating layer 4, and an infrared end cap 5. The fluoride glass used for the core has a chemical composition of 53ZrF4-20BaF2-4LaF3-3AlF3-20NaF (molar ratio), a refractive index of 1.471 at a wavelength of 4μm, and a coefficient of thermal expansion of 18.0 × 10⁻⁶. -6 / K (20~100℃), drawing temperature range is 286~296℃; the chemical composition of the fluoride glass used for the inner cladding is 53ZrF4-20BaF2-2LaF3-3AlF3-22NaF (molar ratio), the refractive index at 4μm wavelength is 1.462, and the coefficient of thermal expansion is 18.4×10 -6 / K (20~100℃), drawing temperature range is 284~294℃; the chemical composition of the chalcogenide glass used for the outer cladding is As 40 S 60 (Molar ratio), coefficient of thermal expansion is 22.0 × 10⁻⁶ -6 / K (20~100℃), the drawing temperature range is 290~310℃; the polymer coating material is polyetherimide, and the infrared end cap material is TeO2-based glass.

[0039] The preparation method is as follows:

[0040] 53ZrF4-20BaF2-4LaF3-3AlF3-20NaF fluoride glass for optical fiber cores was synthesized in a platinum crucible under 5N nitrogen protection using a melt-quench technique, and then cold-worked into a core fluoride glass rod with a diameter of 9.9 mm. 53ZrF4-20BaF2-2LaF3-3AlF3-22NaF fluoride glass for optical fiber inner cladding was melted in a platinum crucible under 5N nitrogen protection, and an inner cladding fluoride glass sleeve with inner and outer diameters of 10 mm and 12.5 mm, respectively, was obtained using a high-temperature spin-tube technique. As for optical fiber outer cladding, it was synthesized in a vacuum quartz tube using a melt-quench technique. 40 S 60Chalcogenide glass was used to obtain an outer cladding chalcogenide glass sleeve with inner and outer diameters of 12.6 mm and 15 mm, respectively, using high-temperature spin tube technology. A fiber core fluoride glass rod was inserted into the inner cladding fluoride glass sleeve, and then inserted into the outer cladding chalcogenide glass sleeve. Finally, a polyetherimide film was wrapped on the outer surface to a diameter of 18.5 mm, thus assembling an optical fiber preform. The optical fiber preform was drawn into an optical fiber with a diameter of 360 μm under 5N pure nitrogen protection and at 290℃. An 8-meter length of optical fiber was cut, and the polyetherimide coating material at both ends of the optical fiber was removed using the organic solvent dimethylacetamide. The two ends of the optical fiber were fused to two unclad TeO2-based glass optical fibers (self-made) with a diameter of 300 μm and a length of 100 mm using an optical fiber fusion splicer. The TeO2-based glass optical fiber was cut using an optical fiber cleaver so that the length of the TeO2-based glass infrared end caps at both ends of the final mid-wave infrared composite glass optical fiber was approximately 0.4 mm.

[0041] The test results of this embodiment are as follows: core diameter ~200μm, inner cladding diameter ~250μm, outer cladding diameter ~300μm, and coating diameter ~360μm. Using a 3-5μm optical parametric amplifier with a pulse width of 10ns and a repetition frequency of 20kHz, the fiber can transmit a maximum average power of ~27.8W, and there is no significant attenuation after 24 hours of operation. In comparison, fibers with the same core diameter, sulfur-free glass cladding, and infrared endcaps can only transmit a maximum average power of ~15.1W, and damage occurs after approximately 20 minutes of operation due to corrosion from moisture in the air.

[0042] Example 2

[0043] In this embodiment, the fluoride glass used for the core of the infrared composite glass fiber has a chemical composition of 53ZrF4-20BaF2-4LaF3-3AlF3-20NaF (molar ratio), a refractive index of 1.471 at a wavelength of 4μm, and a coefficient of thermal expansion of 18.0×10⁻⁶. -6 / K (20~100℃), drawing temperature range is 286~296℃; the chemical composition of the fluoride glass used for the inner cladding is 33ZrF4-20HfF4-20BaF2-4LaF3-3AlF3-20NaF (molar ratio), the refractive index at 4μm wavelength is 1.459, and the coefficient of thermal expansion is 17.8×10 -6 / K (20~100℃), drawing temperature range is 280~290℃; the chemical composition of the chalcogenide glass used for the outer cladding is Ge 10 As 30 Se 40 Te 20 (Molar ratio), coefficient of thermal expansion is 18.4 × 10⁻⁶ -6 / K (20~100℃), drawing temperature range is 280~300℃; coating material is polyethersulfone resin, infrared end cap material is AlF3-based glass.

[0044] The preparation method is as follows:

[0045] 53ZrF4-20BaF2-4LaF3-3AlF3-20NaF fluoride glass for optical fiber cores was synthesized in a platinum crucible protected by 5N pure argon using a melt-quench technique, and then cold-worked into a 6mm diameter core fluoride glass rod. 33ZrF4-20HfF4-20BaF2-4LaF3-3AlF3-20NaF fluoride glass for optical fiber inner cladding was melted in a platinum crucible protected by 5N pure argon, and a high-temperature spin tube technique was used to obtain an inner cladding fluoride glass sleeve with inner and outer diameters of 6.1mm and 12mm, respectively. GeO2 for optical fiber outer cladding was synthesized in a vacuum quartz tube using a melt-quench technique. 10 As 30 Se 40 Te 20 Chalcogenide glass was used to obtain an outer cladding chalcogenide glass sleeve with inner and outer diameters of 12.2 mm and 15 mm, respectively, using high-temperature spin tube technology. A fiber core fluoride glass rod was inserted into the inner cladding fluoride glass sleeve, and then inserted into the outer cladding chalcogenide glass sleeve. Finally, a polyethersulfone resin film was wrapped on the outer surface to a diameter of 18.5 mm, thus assembling an optical fiber preform. The optical fiber preform was drawn into an optical fiber with a diameter of 300 μm under 5N pure argon protection and at 288℃. A 10-meter length of optical fiber was cut, and the polyethersulfone resin coating material at both ends of the optical fiber was removed using the organic solvent dichloromethane. The two ends of the optical fiber were fused to two unclad AlF3-based glass optical fibers (self-made) with a diameter of 250 μm and a length of 80 mm using an optical fiber fusion splicer. The AlF3-based glass optical fiber was cut using an optical fiber cleaver so that the length of the AlF3-based glass infrared end caps at both ends of the final mid-wave infrared composite glass optical fiber was approximately 0.3 mm.

[0046] The test results of this embodiment are as follows: core diameter ~100μm, inner cladding diameter ~200μm, outer cladding diameter ~250μm, and coating diameter ~300μm. Using a 3-5μm optical parametric amplifier with a pulse width of 10ns and a repetition frequency of 20kHz, the fiber can transmit a maximum average power of ~12.2W, and there is no significant attenuation after 24 hours of operation. In comparison, fibers with the same core diameter, sulfur-free glass cladding, and infrared endcaps can only transmit a maximum average power of ~5.7W, and damage occurs after approximately 30 minutes of operation due to corrosion from moisture in the air.

[0047] Example 3

[0048] In this embodiment, the chemical composition of the fluoride glass used for the core of the infrared composite glass fiber is 30InF3-20BaF2-20SrF2-20ZnF2-10GaF3 (molar ratio), with a refractive index of 1.472 at a wavelength of 4μm and a coefficient of thermal expansion of 17.8×10⁻⁶. -6 / K (20~100℃), drawing temperature range is 340~350℃; the chemical composition of the fluoride glass used for the inner cladding is 30InF3-20BaF2-20SrF2-15ZnF2-10GaF3-5NaF (molar ratio), the refractive index at 4μm wavelength is 1.460, and the coefficient of thermal expansion is 18.0×10 -6 / K (20~100℃), drawing temperature range is 336~346℃; the chemical composition of the chalcogenide glass used for the outer cladding is Ge 12 As 24 Se 64 (Molar ratio), coefficient of thermal expansion is 18.2 × 10⁻⁶ -6 / K (20~100℃), the wire drawing temperature range is 330~350℃; the coating material is polyethersulfone resin, and the infrared end cap material is Al2O3 single crystal.

[0049] The preparation method is as follows:

[0050] 30InF3-20BaF2-20SrF2-20ZnF2-10GaF3 fluoride glass for optical fiber cores was synthesized in a platinum crucible protected by 5N pure argon using a melt-quench technique, and then cold-worked into a core fluoride glass rod with a diameter of 13.2 mm. 30InF3-20BaF2-20SrF2-15ZnF2-10GaF3-5NaF fluoride glass for optical fiber inner cladding was melted in a platinum crucible protected by 5N pure argon, and an inner cladding fluoride glass sleeve with inner and outer diameters of 13.3 mm and 16 mm, respectively, was obtained using a high-temperature spin tube technique. GeF3 for optical fiber outer cladding was synthesized in a vacuum quartz tube using a melt-quench technique. 12 As 24 Se 64Chalcogenide glass was used to obtain an outer cladding chalcogenide glass sleeve with inner and outer diameters of 16.2 mm and 19 mm, respectively, using high-temperature spin tube technology. A fiber core fluoride glass rod was inserted into the inner cladding fluoride glass sleeve, and then inserted into the outer cladding chalcogenide glass sleeve. Finally, a polyethersulfone resin film was wrapped on the outer surface to a diameter of 24.4 mm, thus assembling an optical fiber preform. The optical fiber preform was drawn into an optical fiber with a diameter of 440 μm under 5N pure helium protection and at 342℃. A 6-meter length of optical fiber was cut, and the polyethersulfone resin coating material at both ends of the optical fiber was removed using the organic solvent dichloromethane. The two ends of the optical fiber were then fused to two double-sided polished Al2O3 single crystals (purchased) with a diameter of 360 μm and a thickness of 0.4 mm using an optical fiber fusion splicer.

[0051] The test results of this embodiment are as follows: core diameter ~250μm, inner cladding diameter ~302μm, outer cladding diameter ~358μm, and coating diameter ~440μm. Using a 3-5μm optical parametric amplifier with a pulse width of 10ns and a repetition frequency of 20kHz, the fiber can transmit a maximum average power of ~36.4W, and there is no significant attenuation after 24 hours of operation. In comparison, a fiber with the same core diameter, a sulfur-free glass cladding, and an infrared end cap can only transmit a maximum average power of ~19.7W, and damage occurs after approximately 10 minutes of operation due to corrosion from moisture in the air.

[0052] Example 4

[0053] In this embodiment, the fluoride glass used for the core of the infrared composite glass fiber has a chemical composition of 30InF3-20BaF2-20SrF2-20ZnF2-10YF3 (molar ratio), a refractive index of 1.465 at a wavelength of 4μm, and a coefficient of thermal expansion of 18.0×10⁻⁶. -6 / K (20~100℃), drawing temperature range is 335~345℃; the chemical composition of the fluoride glass used for the inner cladding is 30InF3-20BaF2-20SrF2-18ZnF2-10YF3-2NaF (molar ratio), the refractive index at 4μm wavelength is 1.455, and the coefficient of thermal expansion is 18.3×10 -6 / K (20~100℃), drawing temperature range is 330~340℃; the chemical composition of the chalcogenide glass used for the outer cladding is Ge 20 Sb 10 S 70 (Molar ratio), coefficient of thermal expansion is 18.9 × 10⁻⁶ -6 / K (20~100℃), the wire drawing temperature range is 330~350℃; the coating material is polyetherimide, and the infrared end cap material is yttrium aluminum garnet single crystal.

[0054] The preparation method is as follows:

[0055] 30InF3-20BaF2-20SrF2-20ZnF2-10YF3 fluoride glass for optical fiber cores was synthesized in a platinum crucible under 5N nitrogen protection using a melt-quench technique, and then cold-worked into core fluoride glass rods with a diameter of 8 mm. 30InF3-20BaF2-20SrF2-18ZnF2-10YF3-2NaF fluoride glass for optical fiber inner cladding was melted in a platinum crucible under 5N nitrogen protection, and an inner cladding fluoride glass sleeve with inner and outer diameters of 8.1 mm and 16 mm, respectively, was obtained using a high-temperature spin-tube technique. GeO2 for optical fiber outer cladding was synthesized in a vacuum quartz tube using a melt-quench technique. 20 Sb 10 S 70 Chalcogenide glass was used to obtain an outer cladding chalcogenide glass sleeve with inner and outer diameters of 16.2 mm and 19 mm, respectively, using high-temperature spin tube technology. A fiber core fluoride glass rod was inserted into the inner cladding fluoride glass sleeve, and then inserted into the outer cladding chalcogenide glass sleeve. Finally, a polyetherimide film was wrapped on the outer surface to a diameter of 22.4 mm, thus assembling an optical fiber preform. The optical fiber preform was drawn into an optical fiber with a diameter of 400 μm under 5N pure helium protection and at 338℃. A 3-meter length of optical fiber was cut, and the polyetherimide coating material at both ends of the optical fiber was removed using the organic solvent dimethylacetamide. The two ends of the optical fiber were then fused together with a double-sided polished yttrium aluminum garnet single crystal with a diameter of 350 μm and a thickness of 0.5 mm using an optical fiber fusion splicer.

[0056] The test results of this embodiment are as follows: core diameter ~150μm, inner cladding diameter ~300μm, outer cladding diameter ~355μm, and coating diameter ~400μm. Using a 3-5μm optical parametric amplifier with a pulse width of 10ns and a repetition frequency of 20kHz, the fiber can transmit a maximum average power of ~21.5W, and there is no significant attenuation after 24 hours of operation. In comparison, fibers with the same core diameter, sulfur-free glass cladding, and infrared endcaps can only transmit a maximum average power of ~11.2W, and damage occurs after approximately 15 minutes of operation due to corrosion from moisture in the air.

Claims

1. A mid-wave infrared composite glass optical fiber, characterized in that, From the inside out, it includes a fiber core, an inner cladding, and an outer cladding; the fiber core and the inner cladding are fluoride glass, and the outer cladding is chalcogenide glass; the refractive index n1 of the fiber core is greater than the refractive index n2 of the inner cladding, and a polymer coating layer is wrapped around the outer cladding; infrared end caps are fused to both ends of the optical fiber.

2. The mid-wave infrared composite glass optical fiber according to claim 1, characterized in that, The difference in the coefficients of thermal expansion between any two of the fluoride glass used for the fiber core, the fluoride glass used for the inner cladding, and the chalcogenide glass used for the outer cladding is ≤4×10⁻⁶. -6 / K, the drawing temperature ranges of any two overlap.

3. The mid-wave infrared composite glass optical fiber according to claim 1, characterized in that, The polymer coating is made of polyetherimide or polyethersulfone resin.

4. The mid-wave infrared composite glass optical fiber according to claim 1, characterized in that, The infrared end cap is made of TeO2-based glass, AlF3-based glass, alumina single crystal, or yttrium aluminum garnet single crystal.

5. The mid-wave infrared composite glass optical fiber according to any one of claims 1-4, characterized in that, The fluoride glass is ZrF4-based glass or InF3-based glass; the chalcogenide glass comprises 1-2 elements from germanium, arsenic, and antimony, and 1-2 elements from sulfur, selenium, and tellurium.

6. A method for preparing a mid-wave infrared composite glass optical fiber, characterized in that, Includes the following steps: Step 1: Fluoride glass for optical fiber cores is synthesized in a platinum crucible under inert gas protection using a melt-quench technique, and then cold-processed into a core fluoride glass rod. Step 2: Melt fluoride glass for the inner cladding of optical fibers in a platinum crucible protected by an inert gas, and obtain the inner cladding fluoride glass sleeve using a high-temperature spin tube technique. Step 3: Chalcogenide glass for optical fiber cladding is synthesized in a vacuum quartz tube using a melt-quenching technique, and a chalcogenide glass sleeve for cladding is obtained using a high-temperature spin tube technique. Step 4: Insert the fiber core fluoride glass rod into the inner cladding fluoride glass sleeve, then insert it into the outer cladding chalcogenide glass sleeve, and finally wrap the outer surface with a thin film polymer coating material to assemble the optical fiber preform. Step 5: Draw the optical fiber preform into an optical fiber under inert gas protection; Step 6: Cut a certain length of optical fiber and use an organic solvent to remove the polymer coating material at both ends of the optical fiber; Step 7: When the end cap material is glass, fusion splice both ends of the optical fiber with the fibrous infrared end cap material, and then cut the infrared end cap material with an optical fiber cleaver so that the end cap length at both ends of the optical fiber is <1mm; or when the end cap material is crystal, use an optical fiber fusion splicer to fusion splice both ends of the optical fiber with an infrared end cap material with a thickness of <1mm to obtain the required mid-wave infrared composite glass optical fiber.

7. The method for preparing mid-wave infrared composite glass optical fiber according to claim 6, characterized in that, The diameter of the fiber core fluoride glass rod matches the inner diameter of the inner cladding fluoride glass sleeve, and the outer diameter of the inner cladding fluoride glass sleeve matches the inner diameter of the outer cladding chalcogenide glass sleeve.

8. The method for preparing mid-wave infrared composite glass optical fiber according to claim 6, characterized in that, The inert gas is nitrogen, argon, or helium.

9. The method for preparing mid-wave infrared composite glass optical fiber according to claim 6, characterized in that, The organic solvent is dimethylacetamide or dichloromethane.

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