Chromium-doped near-infrared glass ceramic optical fiber and preparation method thereof

Abstract

The invention discloses a chromium-doped near-infrared glass ceramic optical fiber and a preparation method thereof. The glass ceramic optical fiber comprises a fiber core and a cladding, the fiber core is made of chromium ion doped glass materials, the cladding is made of quartz glass materials with the softening temperature higher than the melting temperature of the fiber core, and MgAl2O4 nanocrystals are contained in the fiber core. And the molar composition of the fiber core is represented by a chemical formula as follows: 15 to 25 mol percent of Al2O3, 15 to 25 mol percent of MgO, 69.95 to 49 mol percent of SiO2 and 0.05 to 1 mol percent of Cr2O3. The luminous intensity of the microcrystalline glass optical fiber subjected to heat treatment is improved in order of magnitude, and good light guide performance can still be kept. The spectrum of the near-infrared glass ceramic optical fiber is greatly enhanced and the half-peak width of the spectrum is greatly regulated and controlled only through simple Cr < 3 + > ion concentration regulation and control, and the near-infrared glass ceramic optical fiber has the potential to be widely applied to near-infrared optical fiber lasers or optical fiber array light source devices.

Description

Technical Field

[0001] The invention relates to the technical field of near-infrared optical fibers, and in particular to a chromium-doped near-infrared microcrystalline glass optical fiber and a preparation method thereof. Background Art

[0002] Real-time dynamic optical imaging has attracted extensive attention in the fields of photonics, life sciences, biomedical engineering applications, and basic optoelectronic materials science and devices due to its unique high sensitivity and instant observation capabilities with high spatiotemporal resolution. In particular, near-infrared (NIR) window imaging has advanced dynamic monitoring capabilities in biological imaging due to low levels of photon scattering and tissue autofluorescence. However, NIR imaging contrast agents are mainly excited by expensive high-power lasers or X-rays. The limited absorption of lasers inevitably leads to signal attenuation, and high-power lasers or X-rays may also cause potential biological damage and uneven illumination. Worse still, the line emission of lasers can only activate a single or limited number of fluorescent contrast agents, resulting in multi-channel imaging, and multiple lasers must be used, which increases the complexity and instability of the imaging system and the difficulty of surgical operations. In contrast, the safe broadband NIR continuous spectrum in the range of 650 to 1100 nm covers the optimal excitation wavelengths of most fluorescent imaging agents, can simultaneously excite multiple fluorescent agents for multi-channel signal acquisition, simplify dynamic multi-channel fluorescence imaging, and provide a new approach and platform for immunological research. However, current in vivo fluorescence imaging surgeries require invasive surgery to widely expose the underlying tissue due to significant photon attenuation in biological tissues. Invasive interventions often lead to unreliable results due to changes in the microenvironment. In addition, large incisions inevitably increase the risk of infection and slow patient recovery. In contrast, the advent of endoscopy has effectively addressed these challenges. Integrating micro-instruments and tools onto endoscopes enables multifunctionality, thereby transforming complex surgeries into minimally invasive surgeries. Therefore, the fusion of fluorescence imaging and endoscopy has attracted great interest from researchers and technology companies.

[0003] Typically, micro-light source systems are key components of endoscopic imaging, which are achieved by coupling illumination or excitation light into fiber bundles through complex lens systems. However, since commercially available light sources, such as light-emitting diodes (LEDs) and xenon lamps, often exhibit low directivity and poor collimation, fiber coupling is difficult, making the integration of multiplexed fluorescence imaging with endoscopes a major challenge. The inherent limitations of the light-to-fiber coupling strategy necessitate the exploration of fiber array light sources. Nanocrystal glass composites (NGCs) are promising photon converters that combine the excellent fiber drawing ability of the glass matrix with the excellent near-infrared luminescence properties of nanocrystals. After NGCs are drawn into optical fibers, they can be directly fused with low-loss commercial quartz optical fibers and seamlessly integrated into fiber bundles to become array light sources for endoscopes. The conversion of the coupling connection system from light-to-fiber to fiber-to-fiber can achieve high optical coupling efficiency, simplify the light source system, and improve stability. Therefore, there is an urgent need to develop efficient, broadband near-infrared photon conversion microcrystalline glass fibers for multiplexed fluorescence endoscopy. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a chromium-doped near-infrared microcrystalline glass optical fiber and a preparation method thereof. The microcrystalline glass optical fiber prepared by the present invention not only has excellent luminescence performance and high chemical stability, but also has a wide near-infrared emission characteristic.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] A chromium-doped near-infrared microcrystalline glass optical fiber comprises a core and a cladding, wherein the core is a glass material doped with chromium ions, the cladding is a quartz glass material having a softening temperature higher than the melting temperature of the core, and the core contains MgAl 2 O 4 Nanocrystal; the molar composition of the fiber core is expressed by the chemical formula: Al 2 O 3 : 15~25mol%, MgO: 15~25mol%, SiO 2 :69.95~49mol%Cr 2 O 3 :0.05~1mol%.

[0007] The fiber core is composed of a matrix silicate glass material doped with chromium ions.

[0008] Preferably, the molar composition of the core is expressed as follows: Al 2 O 3 : 15~25mol%, MgO: 15~25mol%, SiO 2 :69.6~49.5mol%Cr 2 O3 :0.4~0.5mol%.

[0009] The near-infrared spectrum of the microcrystalline glass optical fiber is greatly broadened as the chromium ion doping concentration increases; the half-peak width of the emission spectrum first increases and then decreases as the chromium ion doping concentration increases, and the half-peak width of the emission spectrum increases with the increase of the chromium ion doping concentration. 2 O 3 It has a larger emission spectrum half-peak width.

[0010] The method for preparing the chromium-doped near-infrared microcrystalline glass optical fiber comprises the following steps:

[0011] (1) Preparation of core precursor glass rod

[0012] The raw materials are prepared according to the chemical formula of the fiber core, a fiber core precursor glass round rod is prepared by a melt quenching method, and an annealing treatment is performed after the fiber core precursor glass round rod is formed;

[0013] (2) Preparation of optical fiber preform

[0014] (2.1) The core precursor glass round rod is processed to obtain a core precursor glass thin rod, and the surface of the core precursor glass thin rod is polished and cleaned. The outer diameter and length of the core precursor glass thin rod are D2 and L2 respectively;

[0015] (2.2) Insert the cleaned core precursor glass rod into the axial hole of the quartz cladding rod to obtain an optical fiber preform rod; the length of the quartz cladding rod is L1, the inner diameter is D1, D2<D1, L2<L1;

[0016] (3) Fiber drawing

[0017] The optical fiber preform rod is kept warm in a furnace and then drawn into an optical fiber to obtain a precursor optical fiber. The keeping temperature is the softening temperature of the quartz cladding rod ±10°C.

[0018] (4) Fiber heat treatment

[0019] The precursor optical fiber is subjected to a crystallization heat treatment to obtain a chromium-doped near-infrared microcrystalline glass optical fiber.

[0020] Preferably, in step (1), the melting temperature of the melt quenching method is 1650-1800° C., the melting time is 1-3 hours, and the quenching method is to pour the molten glass into a graphite mold at room temperature.

[0021] Preferably, in step (1), the annealing treatment is annealing at 750-800° C. for 6-8 h, and cooling to 30-50° C. at 5-8° C. / h.

[0022] Preferably, in step (2), D1 is 0.1 to 0.3 mm larger than D2.

[0023] Preferably, in step (2), D2 is 6 to 8 mm.

[0024] Preferably, in step (2), the outer diameter of the quartz cladding rod is 20 to 30 mm.

[0025] Preferably, in step (2), an annular groove is machined on the outer wall of the cladding glass round rod, and the annular groove is far away from the open end of the cladding glass round rod.

[0026] Preferably, in step (3), the insulation time is 20 to 60 minutes.

[0027] Preferably, in step (3), the optical fiber drawing is carried out in an inert gas atmosphere or in air.

[0028] Preferably, in step (4), the temperature of the crystallization heat treatment is 950-1050° C. and the time is 2-10 h.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] 1. The core of the near-infrared microcrystalline glass optical fiber of the present invention contains MgAl 2 O 4 Nanocrystals have good light transmission performance and can improve near-infrared luminescence by an order of magnitude, making them suitable for near-infrared fiber lasers and fiber array light source devices;

[0031] 2. The near-infrared microcrystalline glass optical fiber of the present invention can achieve narrow-band to broadband near-infrared emission by regulating the Cr ion concentration, solving the problem of Cr 3+ The doped microcrystalline glass optical fiber material has poor luminescence performance and narrow luminescence bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the optical fiber drawing state of the present invention.

[0033] Figure 2 The X-ray diffraction patterns of the precursor optical fiber and the near-infrared microcrystalline glass optical fiber obtained in Example 2 are shown.

[0034] Figure 3 These are the emission spectra of the precursor optical fiber obtained in Example 2 and the near-infrared microcrystalline glass optical fiber obtained in Examples 1-3.

[0035] Figure 4 This is the transmission loss diagram of the near-infrared microcrystalline glass optical fiber obtained in Example 2. DETAILED DESCRIPTION

[0036] In order to better understand the present invention, the present invention is further described below in conjunction with embodiments, but the scope of protection claimed in the present invention is not limited thereto.

[0037] The custom-made quartz cladding rod used in the examples is JGS1, and its softening temperature is 2000°C.

[0038] Example 1

[0039] The chromium-doped near-infrared microcrystalline glass optical fiber of Example 1 comprises a core and a cladding, wherein the core is Cr 3+ Ion-doped glass material, cladding is a custom-made quartz cladding rod, the core contains MgAl 2 O 4 Nanocrystal, wherein the molar composition of the core glass material is expressed by the chemical formula: Al 2 O 3 :15mol%, MgO: 15mol%, SiO 2 : 69.7 mol%, Cr 2 O 3 : 0.3 mol%.

[0040] The method for preparing the chromium-doped near-infrared glass-ceramic optical fiber of Example 1 comprises the following steps:

[0041] (1) Preparation of core precursor glass rod

[0042] The core precursor glass rod of this embodiment is composed of: Al 2 O 3 : 15mol%, MgO: 15mol%, SiO 2 :69.7mol%、Cr 2 O 3 :0.3mol% The raw material is analytically pure SiO 2 、MgO、Al 2 O 3 and Cr 2 O 3 100 g of the raw materials were weighed according to the above molar percentages, ground in a mortar for 20 min, then transferred into a dense corundum crucible, heated to 1650°C at a heating rate of 10°C / min and melted for 1 hour; the resulting molten glass was poured onto a graphite mold for rapid molding, the graphite mold was kept at room temperature, annealed at 750°C for 6 h, and cooled to 50°C at a rate of 5°C / h to obtain a core precursor glass round rod.

[0043] (2) Preparation of optical fiber preform

[0044] The core precursor glass round rod is subjected to external cylindrical processing on a machine tool, and cold processed into a core precursor glass thin rod with a diameter of 6 mm and a length of 60 mm. The surface of the core precursor glass thin rod is then polished and cleaned, and both end surfaces of the core precursor glass thin rod are ground flat to reduce void bubbles. The core precursor glass thin rod and the customized quartz cladding rod are cleaned with hydrochloric acid and anhydrous alcohol. The quartz cladding rod has a specification of 6.1 mm inner diameter, 20 mm outer diameter, and a rod length of 150 mm. The cleaned core precursor glass thin rod is inserted into the axial hole of the quartz cladding rod to obtain an optical fiber preform rod.

[0045] (3) Fiber drawing

[0046] Place the optical fiber preform rod vertically in the furnace of the drawing tower; then, continuously introduce inert gas into the furnace, and heat the furnace. When the temperature inside the furnace reaches about 2000℃, keep it warm for 20 minutes until the core glass is in a molten state, adjust the drawing speed to 7-8m / min and the fiber preform rod feeding speed to 0.2-0.3mm / min, and then start drawing the optical fiber (the schematic diagram of the optical fiber drawing state is shown in Figure 1 As shown), the precursor optical fiber (diameter 125 μm) is finally drawn;

[0047] (4) Fiber heat treatment

[0048] The precursor optical fiber is loaded into a clean quartz tube, and then the quartz tube is placed in an annealing furnace and kept at 1000°C for 4 hours to perform crystallization heat treatment on the precursor optical fiber to obtain a near-infrared microcrystalline glass optical fiber containing nanocrystals.

[0049] Figure 3 This is the emission spectrum of the near-infrared microcrystalline glass optical fiber obtained in Example 1. From the emission spectrum, it can be seen that the luminescence intensity of the optical fiber after the crystallization heat treatment is significantly increased. Compared with the precursor optical fiber, its luminescence intensity is enhanced by an order of magnitude, and the emission peak half-width is 151nm.

[0050] Example 2

[0051] The chromium-doped near-infrared microcrystalline glass optical fiber of Example 2 comprises a core and a cladding, wherein the core is Cr 3+ Ion-doped glass material, cladding is a custom-made quartz cladding rod, the core contains MgAl 2 O 4 Nanocrystal, wherein the molar composition of the core glass material is expressed by the chemical formula: Al 2 O 3 :15mol%, MgO: 15mol%, SiO 2 : 69.6mol%Cr 2 O 3 : 0.4 mol%.

[0052] The method for preparing the chromium-doped near-infrared microcrystalline glass optical fiber of Example 2 comprises the following steps:

[0053] (1) Preparation of core precursor glass rod

[0054] The core precursor glass rod of this embodiment is composed of: Al 2 O 3 : 15mol%, MgO: 15mol%, SiO 2 :69.6mol%、Cr 2 O 3 : 0.4 mol%, the raw material is analytically pure SiO 2 、MgO、Al 2 O 3 and Cr 2 O 3 100 g of the raw materials were weighed according to the above molar percentages, ground in a mortar for 20 min, then transferred into a dense corundum crucible, heated to 1650°C at a rate of 10°C / min and melted for 1 hour; the resulting molten glass was poured onto a graphite mold for rapid molding, the graphite mold was kept at room temperature, annealed at 750°C for 6 h, and cooled to 50°C at a rate of 5°C / h to obtain a core precursor glass round rod.

[0055] (2) Preparation of optical fiber preform

[0056] The core precursor glass round rod is subjected to external cylindrical processing on a machine tool, and cold processed into a core precursor glass thin rod with a diameter of 6 mm and a length of 60 mm. The surface of the core precursor glass thin rod is then polished and cleaned, and both end surfaces of the core precursor glass thin rod are ground flat to reduce void bubbles. The core precursor glass thin rod and the customized quartz cladding rod are cleaned with hydrochloric acid and anhydrous alcohol. The quartz cladding rod has a specification of 6.1 mm inner diameter, 20 mm outer diameter, and a rod length of 150 mm. The cleaned core precursor glass thin rod is inserted into the axial hole of the quartz cladding rod to obtain an optical fiber preform rod.

[0057] (3) Fiber drawing

[0058] Place the optical fiber preform rod vertically in the furnace of the drawing tower; then, continuously introduce inert gas into the furnace, and heat the furnace. When the temperature inside the furnace reaches about 2000℃, keep it warm for 20 minutes until the core glass is in a molten state, adjust the drawing speed to 7-8m / min and the fiber preform rod feeding speed to 0.2-0.3mm / min, and then start drawing the optical fiber (the schematic diagram of the optical fiber drawing state is shown in Figure 1 As shown), the precursor optical fiber (diameter 125 μm) is finally drawn;

[0059] (4) Fiber heat treatment

[0060] The precursor optical fiber is loaded into a clean quartz tube, and then the quartz tube is placed in an annealing furnace and kept at 1000°C for 4 hours to perform crystallization heat treatment on the precursor optical fiber to obtain a near-infrared microcrystalline glass optical fiber containing nanocrystals.

[0061] Figure 2 The X-ray diffraction patterns of the precursor fiber and near-infrared microcrystalline glass fiber obtained in Example 2 show that the precursor fiber shows a large mantou peak, proving that there is no crystalline phase in its core. For the near-infrared microcrystalline glass fiber, the crystal phase of the reference PDF card is MgAl 2 O 4 , indicating that the optical fiber contains MgAl 2 O 4 Crystal phase.

[0062] Figure 3 The emission spectra of the precursor fiber and the near-infrared microcrystalline glass fiber obtained in Example 2. From the emission spectra, it can be seen that the luminescence intensity of the fiber after the crystallization heat treatment is significantly increased, and its luminescence intensity is enhanced by an order of magnitude compared with the precursor fiber. In addition, the emission spectrum of this fiber is further broadened compared with the near-infrared microcrystalline glass fiber obtained in Example 1, and the emission peak half-width is 270nm.

[0063] Figure 4 The transmission loss diagram of the near-infrared microcrystalline glass fiber obtained for Example 2 is 0.2128 dB cm -1 , indicating that the optical fiber has very good light transmission characteristics.

[0064] Example 3

[0065] The chromium-doped near-infrared microcrystalline glass optical fiber of Example 3 comprises a core and a cladding, wherein the core is Cr 3+ Ion-doped glass material, cladding is a custom-made quartz cladding rod, the core contains MgAl 2 O 4 Nanocrystal, wherein the molar composition of the core glass material is expressed by the chemical formula: Al 2 O 3 :15mol%, MgO: 15mol%, SiO 2 : 69.5mol%Cr 2 O 3 : 0.5 mol%.

[0066] The method for preparing the chromium-doped near-infrared microcrystalline glass optical fiber of Example 3 comprises the following steps:

[0067] (1) Preparation of core precursor glass rod

[0068] The core precursor glass rod of this embodiment is composed of: Al2 O 3 : 15mol%, MgO: 15mol%, SiO 2 :69.5mol%、Cr 2 O 3 :0.5mol% The raw material is analytically pure SiO 2 、MgO、Al 2 O 3 and Cr 2 O 3 100 g of the raw materials were weighed according to the above molar percentages, ground in a mortar for 20 min, then transferred into a dense corundum crucible, heated to 1650°C at a rate of 10°C / min and melted for 1 hour; the resulting molten glass was poured onto a graphite mold for rapid molding, the graphite mold was kept at room temperature, annealed at 750°C for 6 h, and cooled to 50°C at a rate of 5°C / h to obtain a core precursor glass round rod.

[0069] (2) Preparation of optical fiber preform

[0070] The core precursor glass round rod is subjected to external cylindrical processing on a machine tool, and cold processed into a core precursor glass thin rod with a diameter of 6 mm and a length of 60 mm. The surface of the core precursor glass thin rod is then polished and cleaned, and both end surfaces of the core precursor glass thin rod are ground flat to reduce void bubbles. The core precursor glass thin rod and the customized quartz cladding rod are cleaned with hydrochloric acid and anhydrous alcohol. The quartz cladding rod has a specification of 6.1 mm inner diameter, 20 mm outer diameter, and a rod length of 150 mm. The cleaned core precursor glass thin rod is inserted into the axial hole of the quartz cladding rod to obtain an optical fiber preform rod.

[0071] (3) Fiber drawing

[0072] Place the optical fiber preform rod vertically in the furnace of the drawing tower; then, continuously introduce inert gas into the furnace, and heat the furnace. When the temperature inside the furnace reaches about 2000℃, keep it warm for 20 minutes until the core glass is in a molten state, adjust the drawing speed to 7-8m / min and the fiber preform rod feeding speed to 0.2-0.3mm / min, and then start drawing the optical fiber (the schematic diagram of the optical fiber drawing state is shown in Figure 1 As shown), the precursor optical fiber (diameter 125 μm) is finally drawn;

[0073] (4) Fiber heat treatment

[0074] The precursor optical fiber is loaded into a clean quartz tube, and then the quartz tube is placed in an annealing furnace and kept at 1000°C for 4 hours to perform crystallization heat treatment on the precursor optical fiber to obtain a near-infrared microcrystalline glass optical fiber containing nanocrystals.

[0075] Figure 3This is the emission spectrum of the near-infrared microcrystalline glass fiber obtained in Example 3. From the emission spectrum, it can be seen that the luminescence intensity of the fiber after the crystallization heat treatment is significantly increased, and its luminescence intensity is enhanced by an order of magnitude compared with the precursor fiber. In addition, the emission spectrum of this fiber is further broadened compared with the near-infrared microcrystalline glass fiber obtained in Example 1, and the emission peak half-peak width is 250nm.

[0076] Example 4

[0077] The chromium-doped near-infrared microcrystalline glass optical fiber of Example 4 comprises a core and a cladding, wherein the core is Cr 3+ Ion-doped glass material, cladding is a custom-made quartz cladding rod, the core contains MgAl 2 O 4 Nanocrystal, wherein the molar composition of the core glass material is expressed by the chemical formula: Al 2 O 3 :15mol%, MgO: 15mol%, SiO 2 : 69 mol%, Cr 2 O 3 : 1 mol%.

[0078] The method for preparing the chromium-doped near-infrared glass-ceramic optical fiber of Example 4 comprises the following steps:

[0079] (1) Preparation of core precursor glass rod

[0080] The core precursor glass rod of this embodiment is composed of: Al 2 O 3 : 15mol%, MgO: 15mol%, SiO 2 :69mol%、Cr 2 O 3 : 1mol% The raw material is analytically pure SiO 2 、MgO、Al 2 O 3 and Cr 2 O 3 100 g of the raw materials were weighed according to the above molar percentages, ground in a mortar for 20 min, then transferred into a dense corundum crucible, heated to 1650°C at a rate of 10°C / min and melted for 1 hour; the resulting molten glass was poured onto a graphite mold for rapid molding, the graphite mold was kept at room temperature, annealed at 750°C for 6 h, and cooled to 50°C at a rate of 5°C / h to obtain a core precursor glass round rod.

[0081] (2) Preparation of optical fiber preform

[0082] The core precursor glass round rod is subjected to external cylindrical processing on a machine tool, and cold processed into a core precursor glass thin rod with a diameter of 6 mm and a length of 60 mm. The surface of the core precursor glass thin rod is then polished and cleaned, and both end surfaces of the core precursor glass thin rod are ground flat to reduce void bubbles. The core precursor glass thin rod and the customized quartz cladding rod are cleaned with hydrochloric acid and anhydrous alcohol. The quartz cladding rod has a specification of 6.2 mm inner diameter, 20 mm outer diameter, and a rod length of 150 mm. The cleaned core precursor glass thin rod is inserted into the axial hole of the quartz cladding rod to obtain an optical fiber preform rod.

[0083] (3) Fiber drawing

[0084] Place the optical fiber preform rod vertically in the furnace of the drawing tower; then, continuously introduce inert gas into the furnace, and heat the furnace. When the temperature inside the furnace reaches about 2000℃, keep it warm for 20 minutes until the core glass is in a molten state, adjust the drawing speed to 7-8m / min and the fiber preform rod feeding speed to 0.2-0.3mm / min, and then start drawing the optical fiber (the schematic diagram of the optical fiber drawing state is shown in Figure 1 As shown), the precursor optical fiber (diameter 125 μm) is finally drawn;

[0085] (4) Fiber heat treatment

[0086] The precursor optical fiber is placed in a clean quartz tube, and then the quartz tube is placed in an annealing furnace and kept at 1050°C for 2 hours to perform crystallization heat treatment on the precursor optical fiber to obtain a near-infrared microcrystalline glass optical fiber containing nanocrystals.

[0087] Example 5

[0088] The chromium-doped near-infrared microcrystalline glass optical fiber of Example 5 comprises a core and a cladding, wherein the core is Cr 3+ Ion-doped glass material, cladding is a custom-made quartz cladding rod, the core contains MgAl 2 O 4 Nanocrystal, wherein the molar composition of the core glass material is expressed by the chemical formula: Al 2 O 3 :25mol%, MgO: 25mol%, SiO 2 :49.95mol%Cr 2 O 3 : 0.05 mol%.

[0089] The method for preparing the chromium-doped near-infrared microcrystalline glass optical fiber of Example 5 comprises the following steps:

[0090] (1) Preparation of core precursor glass rod

[0091] The core precursor glass rod of this embodiment is composed of: Al2 O 3 : 25mol%, MgO: 25mol%, SiO 2 :49.95mol%、Cr 2 O 3 :0.05mol% The raw material is analytically pure SiO 2 、MgO、Al 2 O 3 and Cr 2 O 3 100 g of the raw materials were weighed according to the above molar percentages, ground in a mortar for 20 min, then transferred into a dense corundum crucible, heated to 1650°C at a rate of 10°C / min and melted for 1 hour; the resulting molten glass was poured onto a graphite mold for rapid molding, the graphite mold was kept at room temperature, annealed at 750°C for 6 h, and cooled to 50°C at a rate of 5°C / h to obtain a core precursor glass round rod.

[0092] (2) Preparation of optical fiber preform

[0093] The core precursor glass round rod is subjected to external cylindrical processing on a machine tool, and cold processed into a core precursor glass thin rod with a diameter of 6 mm and a length of 60 mm. The surface of the core precursor glass thin rod is then polished and cleaned, and both end surfaces of the core precursor glass thin rod are ground flat to reduce void bubbles. The core precursor glass thin rod and the customized quartz cladding rod are cleaned with hydrochloric acid and anhydrous alcohol. The quartz cladding rod has a specification of 6.3 mm inner diameter, 20 mm outer diameter, and a rod length of 150 mm. The cleaned core precursor glass thin rod is inserted into the axial hole of the quartz cladding rod to obtain an optical fiber preform rod.

[0094] (3) Fiber drawing

[0095] Place the optical fiber preform rod vertically in the furnace of the drawing tower; then, continuously introduce inert gas into the furnace, and heat the furnace. When the temperature inside the furnace reaches about 2000℃, keep it warm for 20 minutes until the core glass is in a molten state, adjust the drawing speed to 7-8m / min and the fiber preform rod feeding speed to 0.2-0.3mm / min, and then start drawing the optical fiber (the schematic diagram of the optical fiber drawing state is shown in Figure 1 As shown), the precursor optical fiber (diameter 125 μm) is finally drawn;

[0096] (4) Fiber heat treatment

[0097] The precursor optical fiber is placed in a clean quartz tube, and then the quartz tube is placed in an annealing furnace and kept at 950°C for 10 hours to perform crystallization heat treatment on the precursor optical fiber to obtain a near-infrared microcrystalline glass optical fiber containing nanocrystals.

Claims

1. A chromium-doped near-infrared glass-ceramic optical fiber, characterized in that: The invention comprises a core and a cladding, wherein the core is a glass material doped with chromium ions, the cladding is a quartz glass material with a softening temperature higher than the melting temperature of the core, and the core contains MgAl2O4 nanocrystals; the molar composition of the core is expressed by a chemical formula as follows: Al2O3: 15-25mol%, MgO: 15-25mol%, SiO2: 69.95-49mol%, and Cr2O3: 0.05-1mol%.

2. The chromium-doped near-infrared glass-ceramic optical fiber according to claim 1, characterized in that: The molar composition of the fiber core is expressed as follows according to the chemical formula: Al2O3: 15-25 mol%, MgO: 15-25 mol%, SiO2: 69.6-49.5 mol%, Cr2O3: 0.4-0.5 mol%.

3. The method for preparing the chromium-doped near-infrared glass-ceramic optical fiber according to any one of claims 1 to 2, characterized in that: The following steps are involved: (1) Preparation of core precursor glass rod The raw materials are prepared according to the chemical formula of the fiber core, a fiber core precursor glass round rod is prepared by a melt quenching method, and an annealing treatment is performed after the fiber core precursor glass round rod is formed; (2) Preparation of optical fiber preform (2.1) The core precursor glass round rod is processed to obtain a core precursor glass thin rod, and the surface of the core precursor glass thin rod is polished and cleaned. The outer diameter and length of the core precursor glass thin rod are D2 and L2 respectively; (2.2) Insert the cleaned core precursor glass rod into the axial hole of the quartz cladding rod to obtain an optical fiber preform rod; the length of the quartz cladding rod is L1, the inner diameter is D1, D2<D1, L2<L1; (3) Fiber drawing The optical fiber preform rod is kept warm in a furnace and then drawn into an optical fiber to obtain a precursor optical fiber. The keeping temperature is the softening temperature of the quartz cladding rod ±10°C. (4) Fiber heat treatment The precursor optical fiber is subjected to a crystallization heat treatment to obtain a chromium-doped near-infrared microcrystalline glass optical fiber.

4. The preparation method according to claim 3, characterized in that: In step (1), the melting temperature of the melt quenching method is 1650-1800° C., the melting time is 1-3 hours, and the quenching method is to pour the glass melt into a graphite mold at room temperature.

5. The preparation method according to claim 3, characterized in that: In step (1), the annealing treatment is performed at 750-800° C. for 6-8 hours, and then the temperature is reduced to 30-50° C. at a rate of 5-8° C. / h.

6. The preparation method according to claim 3, characterized in that: In step (2), D1 is 0.1 to 0.3 mm larger than D2.

7. The preparation method according to claim 3, characterized in that: In step (2), D2 is 6 to 8 mm.

8. The preparation method according to claim 3, characterized in that: In step (2), the outer diameter of the quartz cladding rod is 20 to 30 mm; In step (2), an annular groove is machined on the outer wall of the cladding glass round rod, and the annular groove is far away from the open end of the cladding glass round rod.

9. The preparation method according to claim 3, characterized in that: In step (3), the insulation time is 20 to 60 minutes.

10. The preparation method according to claim 3, characterized in that: In step (4), the temperature of the crystallization heat treatment is 950-1050° C. and the time is 2-10 hours.

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