Neodymium-doped silica glass with fluorescence spectrum blue-shifted to 870 nm band and its preparation method

Abstract

The present invention relates to the technical field of silica glass optical fibers, and particularly to a neodymium-doped silica glass with a blue-shifted fluorescence spectrum to the 870 nm band and a preparation method thereof. The present invention proposes an innovative method to achieve the blue shift of Nd-doped silica glass and optical fibers from the conventional 900 nm to the 870 nm band. By co-doping with phosphorus elements, the local microstructure of Nd ions in the silica glass is precisely regulated, and its coordination environment is optimized, thereby enhancing the coordination field, promoting changes in the energy level distribution of Nd ions, successfully shifting the fluorescence peak of the neodymium-doped silica glass from 900 nm to 870 nm, effectively breaking through the limitations of applications in the 900 nm band, providing strong technical support for the applications of the 870 nm band in the fields of biological imaging, near-infrared light sources for quantum communication, and precision measurement, and further expanding the application prospects of Nd-doped silica glass in the fields of high-power lasers and advanced photonics.

Description

Technical Field

[0001] The present invention relates to the technical field of silica glass optical fibers, and particularly to a neodymium-doped silica glass with a blue-shifted fluorescence spectrum to the 870 nm band and a preparation method thereof. Background Art

[0002] Due to its unique energy level structure and rich absorption bands, neodymium (Nd)-doped materials exhibit superior optical properties such as low pump threshold and high emission cross-section, and have become the core active ions in high-power laser devices and industrial applications in the 1 μm band. In recent years, the application of Nd-doped materials in the 900 nm band has gradually attracted attention. This band is not only suitable as an efficient pump source for Yb-doped materials, but also located within the atmospheric transmission window, reducing the absorption loss of light in the air. Therefore, it shows significant potential in fields such as atmospheric detection, differential absorption radar, and quantum communication. In addition, in the field of bioimaging, 900 nm band lasers can excite a variety of fluorescent proteins, with a certain tissue penetration depth and enhanced imaging effect. However, Nd-doped materials in the 900 nm band still have deficiencies in terms of tissue penetration depth, imaging resolution, and signal transmission stability in bioimaging and optical fiber communication.

[0003] With the increasing demand for high resolution in bioimaging and the strict requirements for low attenuation rate in optical fiber communication, the application potential of the 870 nm band has gradually emerged. Compared with the 900 nm band, the 870 nm band is closer to the ideal range of the bio-optical window, which can significantly improve the tissue penetration depth and imaging resolution, and at the same time significantly reduce the signal attenuation rate in optical fiber transmission. Therefore, it is regarded as an ideal choice in fields such as bioimaging, quantum communication, and atmospheric detection. However, currently, achieving laser emission in the 870 nm band in Nd-doped fiber lasers still faces technical bottlenecks, especially limitations in pump efficiency and laser output stability. Summary of the Invention

[0004] Aiming at the problem that currently achieving laser emission in the 870 nm band in Nd-doped fiber lasers faces technical bottlenecks, especially limitations in pump efficiency and laser output stability, the present invention provides a neodymium-doped silica glass with a blue-shifted fluorescence spectrum to the 870 nm band and a preparation method thereof.

[0005] A preparation method of a neodymium-doped silica glass with a blue-shifted fluorescence spectrum to the 870 nm band, the components of the neodymium-doped silica glass include P2O5, Nd2O3, and SiO2, and the preparation method includes the following steps:

[0006] Step 1. Weigh the precursor raw materials of each component according to the selected molar percentages. The precursor raw material of P2O5 is phosphoric acid, the precursor raw material of Nd2O3 is neodymium chloride hexahydrate, the precursor raw material of 90wt% to 95wt% of SiO2 is porous silica powder, and the precursor raw material of 5wt% to 10wt% of SiO2 is derived from silanolate;

[0007] Step 2. Prepare a mixed solution according to the volume ratio of silanolate: water: organic solvent = 1:2~10:4~20. Then, add neodymium chloride hexahydrate and phosphoric acid to the mixed solution in sequence. Next, add a silanolate hydrolysis catalyst to adjust the pH value of the solution to the first pH value, and stir thoroughly at room temperature for 1 to 20 hours to obtain a Nd 3+ - and P 5+ -co-doped silica transparent sol, and then let it stand for 1 to 5 days;

[0008] Step 3. Add the porous silica powder to the vigorously stirred silica transparent sol in batches according to a fixed addition amount. After the addition is completed, continue to stir for 2 to 48 hours to form a suspension;

[0009] Step 4. Granulate the suspension to obtain a preliminary powder, and heat the preliminary powder to 1000 °C in an oxygen atmosphere in a tube furnace and hold it at 1000 °C for 5 to 20 hours to remove residual carbon and hydroxyl groups, forming Nd-doped high-phosphorus silica powder;

[0010] Step 5. Use a ball milling device to ball mill the silica powder and control the particle size below 100 μm;

[0011] Step 6. Place the ball-milled silica powder in a graphite crucible and melt it in a high-temperature furnace at 1500 to 1730 °C under a vacuum of 10 -1 to 10 -3 torr for 1 to 8 hours, and cool it with the furnace to form a bubble-free transparent glass, and the bubble-free transparent glass is the neodymium-doped quartz glass.

[0012] Preferably, the molar percentages of the components of the neodymium-doped quartz glass are: P2O5: 1mol% to 15mol%, Nd2O3: 0.05mol% to 0.8mol%, and the remaining component is SiO2.

[0013] Preferably, the median particle size of the porous silica powder is in the micro-nano scale.

[0014] Preferably, the silanolate is Si(OC2H5)4 or Si(OCH3)4. When the silanolate is Si(OC2H5)4, the organic solvent is C2H5OH; when the silanolate is Si(OCH3)4, the organic solvent is CH3OH.

[0015] Preferably, the hydrolysis catalyst of the silicate is hydrochloric acid or ammonia water. When the silicate catalyst is hydrochloric acid, the first pH value is 1 to 3; when the silicate catalyst is ammonia water, the first pH value is 8 to 10.

[0016] Preferably, in step 3, the fixed addition amount is 1 to 5 g each time.

[0017] Preferably, in step 4, the suspension is granulated by rotary evaporation.

[0018] On the other hand, a neodymium-doped silica glass with a fluorescence spectrum blue-shifted to the 870 nm band according to the present invention is prepared by the preparation method of the neodymium-doped silica glass with a fluorescence spectrum blue-shifted to the 870 nm band.

[0019] On the third aspect of the present invention, a neodymium-doped silica fiber core rod is made of the above-mentioned neodymium-doped silica glass with a fluorescence spectrum blue-shifted to the 870 nm band.

[0020] Preferably, the neodymium-doped silica glass is cold-worked and polished to obtain a fiber core rod. The surface roughness of the fiber core rod is less than 10 nm. After the fiber core rod is acid-treated in hydrofluoric acid with a mass concentration of 5 to 20% for 5 to 15 minutes, it is taken out and dried to obtain a neodymium-doped silica fiber core rod.

[0021] Compared with the prior art, the neodymium-doped silica glass with a fluorescence spectrum blue-shifted to the 870 nm band and its preparation method according to the present invention precisely regulate the local microstructure of Nd ions in the silica glass by co-doping with phosphorus elements, optimize its coordination environment, thereby enhancing the coordination field, promoting the change of the energy level distribution of Nd ions, successfully blue-shifting the fluorescence peak of the neodymium-doped silica glass from 900 nm to 870 nm, effectively breaking through the limitation of the application in the 900 nm band, providing strong technical support for the application of the 870 nm band in the fields of biological imaging, near-infrared light sources for quantum communication, and precision measurement, and further expanding the application prospects of Nd-doped silica glass in high-power lasers and advanced photonics fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0023] Figure 1 It is a process schematic diagram of the preparation method of the neodymium-doped silica glass with a fluorescence spectrum blue-shifted to the 870 nm band according to the present invention.

[0024] Figure 2It is the 2D-HYSCORE spectrogram of the neodymium-doped silica glass in Example 1.

[0025] Figure 3 It is the EPMA surface scan diagram of the P element in the neodymium-doped silica glass in Example 2.

[0026] Figure 4 It is a schematic diagram of the normalized absorption spectrum of the neodymium-doped silica glass in Comparative Example 1 and Example 2 at room temperature, with the absorption peak at 580 nm as the reference for Nd ions.

[0027] Figure 5 It is a schematic diagram of the normalized fluorescence spectrum (Ex = 808 nm) of the neodymium-doped silica glass in Comparative Example 1 and Example 2 at room temperature, with the fluorescence secondary peak near 900 nm as the reference for Nd ions. Detailed implementation mode

[0028] To further understand the purpose, structure, characteristics, and functions of the present invention, the following is a detailed description in conjunction with the embodiments.

[0029] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention.

[0030] Please refer to Figure 1 , a preparation method of a neodymium-doped silica glass with a fluorescence spectrum blue-shifted to the 870 nm band. The components of the neodymium-doped silica glass include P2O5, Nd2O3, and SiO2. The preparation method includes the following steps:

[0031] Step 1. Weigh the precursor raw materials of each component according to the selected molar percentages. The precursor raw material of P2O5 is phosphoric acid, the precursor raw material of Nd2O3 is neodymium chloride hexahydrate, the precursor raw material of 90 wt% to 95 wt% of SiO2 is porous silica powder, and the precursor raw material of 5 wt% to 10 wt% of SiO2 is derived from silanolate.

[0032] Step 2. Prepare a mixed solution according to the volume ratio of silanolate: water: organic solvent = 1:2 to 10:4 to 20. Then, add neodymium chloride hexahydrate and phosphoric acid to the mixed solution in sequence, and then add a silanolate hydrolysis catalyst to adjust the pH value of the solution to the first pH value. Stir well at room temperature for 1 to 20 hours to obtain a transparent sol solution of Nd 3+ , P 5+ co-doped silica, and then let it stand for 1 to 5 days.

[0033] Step 3. Add the porous silica powder in batches with a fixed addition amount into the vigorously stirred silica transparent sol, and continue stirring for 2 to 48 hours after the addition is completed to form a suspension;

[0034] Step 4. Granulate the suspension to obtain a preliminary powder, and then heat the preliminary powder to 1000 °C in an oxygen atmosphere in a tubular furnace and keep it at 1000 °C for 5 to 20 hours to remove residual carbon and hydroxyl groups, forming Nd-doped high-phosphorus silica powder;

[0035] Step 5. Ball-mill the silica powder using a ball-milling device and control the particle size to be below 100 μm;

[0036] Step 6. Place the ball-milled silica powder in a graphite crucible, and carry out melting at a high temperature of 1500 to 1730 °C in a high-temperature furnace under a vacuum of 10 -1 to 10 -3 torr for 1 to 8 hours, and cool it with the furnace to form a bubble-free transparent glass, and the bubble-free transparent glass is the Nd-doped quartz glass.

[0037] Preferably, the molar percentages of the components of the Nd-doped quartz glass are: P2O5: 1 mol% to 15 mol%, Nd2O3: 0.05 mol% to 0.8 mol%, and the remaining component is SiO2.

[0038] Preferably, the silicate is Si(OC2H5)4 or Si(OCH3)4. When the silicate is Si(OC2H5)4, the organic solvent is C2H5OH; when the silicate is Si(OCH3)4, the organic solvent is CH3OH.

[0039] Preferably, the hydrolysis catalyst of the silicate is hydrochloric acid or ammonia water. When the hydrolysis catalyst of the silicate is hydrochloric acid, the first pH value is 1 to 3; when the hydrolysis catalyst of the silicate is ammonia water, the first pH value is 8 to 10.

[0040] Preferably, in Step 3, the fixed addition amount is 1 to 5 g each time.

[0041] Preferably, in Step 4, the suspension is granulated by the rotary evaporation method.

[0042] On the other hand, a Nd-doped quartz glass with a fluorescence spectrum blue-shifted to the 870 nm band of the present invention is prepared by the preparation method of the Nd-doped quartz glass with a fluorescence spectrum blue-shifted to the 870 nm band.

[0043] On the third aspect of the present invention, a Nd-doped quartz fiber core rod is prepared from the Nd-doped quartz glass with a fluorescence spectrum blue-shifted to the 870 nm band.

[0044] Preferably, the neodymium-doped silica glass is cold-worked and polished to obtain an optical fiber core rod with a surface roughness of less than 10 nm. The optical fiber core rod is acid-treated in hydrofluoric acid with a mass concentration of 5 to 20% for 5 to 15 minutes, then taken out and dried to obtain a neodymium-doped silica optical fiber core rod.

[0045] In actual use, porous silica refers to amorphous silica powder with a certain porosity, and the median particle size is in the micro-nano scale. The powder includes but is not limited to that prepared by chemical vapor deposition.

[0046] Table 1: Specific compositions of neodymium-doped silica glass in 6 examples and 1 control example

[0047]

[0048] Example 1: The composition of the neodymium-doped silica glass in this example is: 0.05 mol% Nd2O3, 5 mol% P2O5, 94.95 mol% SiO2. Its preparation method includes the following steps:

[0049] Step 1. Weigh the precursor raw materials of each component according to the selected molar percentages. The precursor raw material of P2O5 is phosphoric acid, the precursor raw material of Nd2O3 is neodymium chloride hexahydrate, the precursor raw material of 90 wt% SiO2 is porous silica powder, and the precursor raw material of 10 wt% SiO2 comes from silanolate.

[0050] Step 2. Prepare a mixed solution according to the volume ratio of silanolate: water: organic solvent = 1:6:12, where the silanolate is Si(OC2H5)4 and the organic solvent is C2H5OH. Add neodymium chloride hexahydrate and phosphoric acid to the above mixed solution in sequence, and stir well. Subsequently, add the silanolate hydrolysis catalyst HCl to adjust the pH value of the solution to the first pH value of 3, and stir well at room temperature for 10 hours to obtain a transparent sol solution of Nd 3+ - 5+ - co-doped silica, and then let it stand for 3 days;

[0051] Step 3. Add the porous silica powder in batches with a fixed addition amount of 3 g each time to the vigorously stirred transparent sol solution of silica, and continue to stir for 30 h after the addition to form a suspension;

[0052] Step 4. Granulate the suspension by rotary evaporation to obtain a preliminary powder containing a certain amount of moisture and organic matter. Subsequently, place the preliminary powder in a tube furnace, and slowly raise the temperature from 50°C to 1000°C at a heating rate of 1°C per minute in an oxygen atmosphere, and keep it at 1000°C for 10 hours to remove residual carbon and hydroxyl groups to form Nd-doped high-P silica powder;

[0053] Step 5. Use a ball milling equipment to ball mill the silica powder, controlling the particle size below 100 μm;

[0054] Step 6. Place the ball milled silica powder in a graphite crucible and melt it in a high-temperature furnace at 1730 °C for 4 hours under a vacuum of 10 -3 torr, and then cool it with the furnace to form a bubble-free transparent glass;

[0055] Step 7. Cold process and polish the bubble-free transparent glass into a neodymium-doped quartz sheet glass with a thickness of 2 mm for optical and spectral performance test and evaluation.

[0056] Test method: Grind the 2-mm-thick neodymium-doped quartz sheet glass into micron-sized glass powder. Take 50 mg of the powder sample and perform four-pulse two-dimensional hyperfine sublevel correlation spectroscopy (2D-HYSCORE) test using an E580 pulsed electron paramagnetic resonance (EPR) detector from Bruker, Switzerland at a temperature of 4 K.

[0057] Under a magnetic field of 350 mT, it can be seen from Figure 2 that the resonance peak at 6.0 corresponds to the Larmor frequency of the magnetic nucleus 31 P (NA = 100%, I = 1 / 2), indicating that most Nd ions exist in the local microstructure of the P element.

[0058] Example 2: The composition of the neodymium-doped quartz glass in this example is: 0.1 mol% Nd2O3, 8 mol% P2O5, 91.9 mol% SiO2, and its preparation method includes the following steps:

[0059] Step 1. Weigh the precursor raw materials of each component according to the selected molar percentages. The precursor raw material of P2O5 is phosphoric acid, the precursor raw material of Nd2O3 is neodymium chloride hexahydrate, the precursor raw material of 95 wt% SiO2 is porous silica powder, and the precursor raw material of 5 wt% SiO2 comes from silanolate;

[0060] Step 2. Prepare a mixed solution according to the volume ratio of silanolate: water: organic solvent = 1:5:15, where the silanolate is Si(OC2H5)4 and the organic solvent is C2H5OH. Add neodymium chloride hexahydrate and phosphoric acid to the above mixed solution in sequence, and stir well. Subsequently, add the silanolate hydrolysis catalyst HCl to adjust the pH value of the solution to the first pH value of 3, and stir well at room temperature for 10 hours to obtain a transparent sol solution of Nd 3+ 、P 5+ co-doped silica, and then let it stand for 3 days;

[0061] Step 3. Add the porous silica powder in batches multiple times with a fixed addition amount of 5 g each time to the vigorously stirred silica transparent sol solution. After the addition is completed, continue stirring for 40 h to form a suspension;

[0062] Step 4. Granulate the suspension by rotary evaporation to obtain a preliminary powder containing a certain amount of moisture and organic matter. Subsequently, place the preliminary powder in a tube furnace. Under an oxygen atmosphere, slowly heat it from 50 °C to 1000 °C at a heating rate of 1 °C per minute, and keep it at 1000 °C for 8 hours to remove residual carbon and hydroxyl groups, forming Nd-doped high-P silica powder;

[0063] Step 5. Ball-mill the silica powder using a ball-milling device to control the particle size below 100 μm;

[0064] Step 6. Place the ball-milled silica powder in a graphite crucible and melt it in a high-temperature furnace at 1700 °C under a vacuum of 10 -3 torr for 4 hours, and cool it with the furnace to form a bubble-free transparent glass;

[0065] Step 7. Process the bubble-free transparent glass through cold working and polishing into 2-mm flakes or core rods for optical fibers. The flake glass is used for optical and spectral performance testing and evaluation. The core rod is optically polished with a surface roughness less than 10 nm, placed in HF acid with a mass concentration of 15% for acid treatment for 10 min, taken out and dried, and used as the core rod of Nd-doped high-P quartz optical fiber.

[0066] Figure 3 Fig. is the EPMA surface scan of the P element in the Nd-doped quartz glass in Example 2, and the scanning step size is 50 μm. It can be Figure 3 seen that the distribution of the P element in the Nd-doped quartz glass is extremely uniform.

[0067] Comparative Example 1: The composition of the Nd-doped quartz glass in this example is: 0.8 mol% Nd2O3, 5 mol% Al2O3, 94.2 mol% SiO2, and its preparation method includes the following steps:

[0068] Step 1. Weigh the precursor raw materials of each component oxide according to the selected molar percentage. The precursor raw material of Nd2O3 is neodymium chloride hexahydrate, the precursor raw material of Al2O3 is aluminum chloride hexahydrate, the precursor raw material of 95 wt% SiO2 is porous silica powder, and the precursor raw material of 5 wt% SiO2 comes from silanolate;

[0069] Step 2. Prepare a mixed solution according to the volume ratio of silicate: water: organic solvent = 1:10:20. Select Si(OC2H5)4 as the silicate and C2H5OH as the organic solvent. Add neodymium chloride hexahydrate and aluminum chloride hexahydrate to the above mixed solution in sequence and stir well. Subsequently, add the silicate hydrolysis catalyst HCl to adjust the pH value of the solution to the first pH value of 3, and stir well at room temperature for 10 hours to obtain Nd 3+ , Al 3+ co-doped silica transparent sol, and then let it stand for 3 days;

[0070] Step 3. Add the porous silica powder in batches with a fixed addition amount of 5 g each time to the vigorously stirred silica transparent sol, and continue to stir for 30 h after the addition to form a suspension;

[0071] Step 4. Granulate the suspension by rotary evaporation to obtain a preliminary powder containing a certain amount of moisture and organic matter. Subsequently, place the preliminary powder in a tubular furnace, and slowly heat it from 50 °C to 1000 °C at a heating rate of 1 °C per minute in an oxygen atmosphere, and keep it at 1000 °C for 8 hours to remove residual carbon and hydroxyl groups to form Nd-Al co-doped silica powder;

[0072] Step 5. Ball mill the silica powder using a ball milling device to control the particle size below 100 μm;

[0073] Step 6. Place the ball-milled silica powder in a graphite crucible and melt it in a high-temperature furnace at 1730 °C for 4 hours under a vacuum of 10 -3 torr, and cool it with the furnace to form bubble-free transparent glass;

[0074] Step 7. Process the bubble-free transparent glass through cold working and polishing into 2 mm flakes or core rods for optical fibers. The flake glass is used for optical and spectral performance testing and evaluation. The core rod is optically polished with a surface roughness less than 10 nm, placed in HF acid with a mass concentration of 15% for acid treatment for 10 min, taken out and dried, and used as the core rod of the Nd-Al co-doped quartz optical fiber.

[0075] Figure 4 Schematic diagram of the normalized absorption spectrum of the neodymium-doped quartz glass in Comparative Example 1 and Example 2 at room temperature with the absorption peak at 580 nm as the reference for Nd ions. The peak position of the Nd ion absorption spectrum in Example 2 did not show an obvious change compared with Comparative Example 1, especially at 808 nm.

[0076] Figure 5Schematic diagram of the normalized fluorescence spectrum (Ex = 808nm) of neodymium-doped silica glass at room temperature in Comparative Example 1 and Example 2, with the fluorescence secondary peak near 900nm as the reference. In Example 2, the fluorescence secondary peak near 900nm shifts 30nm towards the short-wavelength direction (blue shift) to 870nm compared to Comparative Example 1.

[0077] Example 3: The composition of the neodymium-doped silica glass in this example is: 0.05mol% Nd2O3, 1mol% P2O5, 98.95mol% SiO2, and its preparation method includes the following steps:

[0078] Step 1. Weigh the precursor raw materials of each component according to the selected molar percentages. The precursor raw material of P2O5 is phosphoric acid, the precursor raw material of Nd2O3 is neodymium chloride hexahydrate, the precursor raw material of 90wt% SiO2 is porous silica powder, and the precursor raw material of 10wt% SiO2 is sourced from silanolate.

[0079] Step 2. Prepare a mixed solution according to the volume ratio of silanolate: water: organic solvent = 1:6:12, where the silanolate is Si(OC2H5)4 and the organic solvent is C2H5OH. Add neodymium chloride hexahydrate and phosphoric acid to the above mixed solution in sequence and stir well. Subsequently, add the silanolate hydrolysis catalyst HCl to adjust the pH value of the solution to the first pH value of 3, and stir well at room temperature for 10 hours to obtain a Nd 3+ 、P 5+ co-doped silica transparent sol solution, and then let it stand for 3 days;

[0080] Step 3. Add the porous silica powder in batches with a fixed addition amount of 3g each time to the vigorously stirred silica transparent sol solution, and continue to stir for 30h after the addition to form a suspension;

[0081] Step 4. Granulate the suspension by rotary evaporation to obtain a preliminary powder containing a certain amount of moisture and organic matter. Subsequently, place the preliminary powder in a tubular furnace, and slowly raise the temperature from 50°C to 1000°C at a rate of 1°C per minute in an oxygen atmosphere, and hold at 1000°C for 10 hours to remove residual carbon and hydroxyl groups to form Nd-doped high-P silica powder;

[0082] Step 5. Use a ball milling device to ball mill the silica powder, controlling the particle size below 100μm;

[0083] Step 6. Place the ball-milled silica powder in a graphite crucible and melt it in a high-temperature furnace at 1730°C for 4 hours under a vacuum of 10 -3 torr, and cool it with the furnace to form a bubble-free transparent glass;

[0084] Step 7. Cold process and polish the bubble-free transparent glass into a neodymium-doped quartz sheet glass with a thickness of 2 mm for optical and spectral performance test and evaluation.

[0085] Example 4: The composition of the neodymium-doped quartz glass in this example is: 0.8 mol% Nd2O3, 15 mol% P2O5, 84.2 mol% SiO2, and its preparation method includes the following steps:

[0086] Step 1. Weigh the precursor raw materials of each component according to the selected molar percentage. The precursor raw material of P2O5 is phosphoric acid, the precursor raw material of Nd2O3 is neodymium chloride hexahydrate, the precursor raw material of 92 wt% SiO2 is porous silica powder, and the precursor raw material of 8 wt% SiO2 is sourced from silanolate.

[0087] Step 2. Prepare a mixed solution according to the volume ratio of silanolate: water: organic solvent = 1:10:20, where Si(OCH3)4 is selected as the silanolate and CH3OH is selected as the organic solvent. Add neodymium chloride hexahydrate and phosphoric acid to the above mixed solution in sequence and stir well. Subsequently, add ammonia water, the hydrolysis catalyst of silanolate, to adjust the pH value of the solution to the first pH value of 8, and stir well at room temperature for 10 hours to obtain a transparent sol solution of Nd 3+ 、P 5+ co-doped silica, and then let it stand for 3 days;

[0088] Step 3. Add the porous silica powder to the vigorously stirred transparent silica sol solution in batches with a fixed addition amount of 5 g each time. After the addition, continue to stir for 30 h to form a suspension;

[0089] Step 4. Granulate the suspension by rotary evaporation to obtain a preliminary powder containing a certain amount of moisture and organic matter. Subsequently, place the preliminary powder in a tube furnace, and slowly heat it from 50 °C to 1000 °C at a heating rate of 1 °C per minute in an oxygen atmosphere, and keep it at 1000 °C for 8 hours to remove residual carbon and hydroxyl groups to form Nd-doped high-P silica powder;

[0090] Step 5. Use a ball milling device to ball mill the silica powder to control the particle size below 100 μm;

[0091] Step 6. Place the ball-milled silica powder in a graphite crucible and melt it in a high-temperature furnace at 1500 °C for 8 hours under a vacuum of 10 -3 torr, and cool it with the furnace to form a bubble-free transparent glass;

[0092] Step 7. Cold process and polish the bubble-free transparent glass into a neodymium-doped quartz sheet glass with a thickness of 2 mm for optical and spectral performance test and evaluation.

[0093] Example 5: The composition of the neodymium-doped fused silica in this example is: 0.4 mol% Nd2O3, 10 mol% P2O5, 89.6 mol% SiO2. Its preparation method includes the following steps:

[0094] Step 1. Weigh the precursor raw materials of each component according to the selected molar percentages. The precursor raw material of P2O5 is phosphoric acid, the precursor raw material of Nd2O3 is neodymium chloride hexahydrate, the precursor raw material of 92 wt% SiO2 is porous silica powder, and the precursor raw material of 8 wt% SiO2 is sourced from silanolate.

[0095] Step 2. Prepare a mixed solution according to the volume ratio of silanolate: water: organic solvent = 1:10:20. Here, Si(OCH3)4 is selected as the silanolate and CH3OH is selected as the organic solvent. Add neodymium chloride hexahydrate and phosphoric acid to the above mixed solution in sequence and stir well. Subsequently, add the silanolate hydrolysis catalyst HCl, adjust the pH value of the solution to the first pH value of 3, and stir well at room temperature for 10 hours to obtain a Nd 3+ - and P 5+ -codoped silica transparent sol solution, and then let it stand for 3 days.

[0096] Step 3. Add the porous silica powder to the vigorously stirred silica transparent sol solution in batches with a fixed addition amount of 5 g each time. After the addition is completed, continue to stir for 30 h to form a suspension.

[0097] Step 4. Granulate the suspension by rotary evaporation to obtain a preliminary powder containing a certain amount of moisture and organic matter. Subsequently, place the preliminary powder in a tube furnace, and under an oxygen atmosphere, slowly heat it from 50°C to 1000°C at a heating rate of 1°C per minute, and keep it at 1000°C for 8 hours to remove residual carbon and hydroxyl groups, forming Nd-doped high-P silica powder.

[0098] Step 5. Use a ball milling device to ball mill the silica powder, controlling the particle size below 100 μm.

[0099] Step 6. Place the ball-milled silica powder in a graphite crucible and melt it in a high-temperature furnace at 1500°C under a vacuum of 10 -3 torr for 8 hours, and then cool it with the furnace to form a bubble-free transparent glass.

[0100] Step 7. Cold process and polish the bubble-free transparent glass into a neodymium-doped fused silica sheet glass with a thickness of 2 mm for optical and spectral performance test and evaluation.

[0101] Example 6: The composition of the neodymium-doped fused silica in this example is: 0.6 mol% Nd2O3, 13 mol% P2O5, 86.4 mol% SiO2. Its preparation method includes the following steps:

[0102] Step 1. Weigh the precursor raw materials of each component according to the selected molar percentages. The precursor raw material of P2O5 is phosphoric acid, the precursor raw material of Nd2O3 is neodymium chloride hexahydrate, the precursor raw material of 90 wt% SiO2 is porous silica powder, and the precursor raw material of 10 wt% SiO2 is sourced from silanolate.

[0103] Step 2. Prepare a mixed solution according to the volume ratio of silanolate: water: organic solvent = 1:6:12, where the silanolate is Si(OC2H5)4 and the organic solvent is C2H5OH. Add neodymium chloride hexahydrate and phosphoric acid to the above mixed solution in sequence and stir well. Subsequently, add the silanolate hydrolysis catalyst ammonia water to adjust the pH value of the solution to the first pH value of 8, and stir well at room temperature for 10 hours to obtain a Nd 3+ , P 5+ co-doped silica transparent sol solution, and then let it stand for 3 days.

[0104] Step 3. Add the porous silica powder in batches with a fixed addition amount of 3 g each time to the vigorously stirred silica transparent sol solution. After the addition, continue to stir for 30 h to form a suspension.

[0105] Step 4. Granulate the suspension by rotary evaporation to obtain a preliminary powder containing a certain amount of moisture and organic matter. Subsequently, place the preliminary powder in a tubular furnace, and under an oxygen atmosphere, slowly heat it from 50°C to 1000°C at a heating rate of 1°C per minute, and keep it at 1000°C for 10 hours to remove residual carbon and hydroxyl groups to form Nd-doped high-P silica powder.

[0106] Step 5. Ball-mill the silica powder using a ball-milling device to control the particle size below 100 μm.

[0107] Step 6. Place the ball-milled silica powder in a graphite crucible and melt it in a high-temperature furnace at 1730°C under a vacuum of 10 -3 torr for 4 hours, and then cool it with the furnace to form a bubble-free transparent glass.

[0108] Step 7. Cold-work and polish the bubble-free transparent glass into a neodymium-doped fused silica sheet glass with a thickness of 2 mm for optical and spectral performance test and evaluation.

[0109] The sheet glass of Examples 3 to 6 was tested in the same way as in Examples 1 and 2, and basically the same test results as in Examples 1 and 2 were obtained, that is, most Nd ions exist in the local microstructure of P element, and the distribution of P element in the neodymium-doped silica glass is extremely uniform.

[0110] The neodymium-doped silica glass with its fluorescence spectrum blue-shifted to the 870 nm band and its preparation method according to the present invention precisely regulate the local microstructure of Nd ions in the silica glass by co-doping with P element, optimize its coordination environment, thereby enhancing the coordination field, causing the energy level distribution of Nd ions to change, successfully blue-shifting the fluorescence peak of the neodymium-doped silica glass from 900 nm to 870 nm, effectively breaking through the limitation of the application in the 900 nm band, providing strong technical support for the application of the 870 nm band in the fields of biological imaging, near-infrared light sources for quantum communication, and precision measurement, and further expanding the application prospects of Nd-doped silica glass in high-power lasers and the field of advanced photonics.

[0111] The present invention has been described by the above related embodiments. However, the above embodiments are only examples for implementing the present invention. In addition, the technical features involved in different embodiments of the present invention described above can be combined with each other as long as they do not conflict with each other. It must be pointed out that the disclosed embodiments do not limit the scope of the present invention. On the contrary, all changes and modifications made without departing from the spirit and scope of the present invention fall within the scope of patent protection of the present invention.

Claims

1. A preparation method of neodymium-doped silica glass with fluorescence spectrum blue-shifted to the 870 nm band, characterized in that, The components of the neodymium-doped silica glass include P2O5, Nd2O3, and SiO2, and the preparation method includes the following steps: Step 1. Weigh the precursor raw materials of each component according to the selected molar percentages. The precursor raw material of P2O5 is phosphoric acid, the precursor raw material of Nd2O3 is neodymium chloride hexahydrate, the precursor raw material of 90wt% to 95wt% of SiO2 is porous silica powder, and the precursor raw material of 5wt% to 10wt% of SiO2 is sourced from silanolate. Step 2. Prepare a mixed solution according to the volume ratio of silicate: water: organic solvent = 1: 2-10: 4-20. Then, add neodymium chloride hexahydrate and phosphoric acid into the mixed solution in sequence. Next, add a silicate hydrolysis catalyst to adjust the pH value of the solution to the first pH value, and stir thoroughly at room temperature for 1 to 20 hours to obtain Nd 3+ , P 5+ co-doped silica transparent sol solution, and let it stand for 1 to 5 days; Step 3. Add the porous silica powder in batches with a fixed addition amount into the vigorously stirred silica transparent sol solution multiple times. After the addition is completed, continue to stir for 2 to 48 hours to form a suspension. Step 4. Granulate the suspension to obtain a preliminary powder, and then heat the preliminary powder to 1000°C in an oxygen atmosphere in a tubular furnace and hold it at 1000°C for 5 to 20 hours to remove residual carbon and hydroxyl groups, forming Nd-doped high-phosphorus silica powder. Step 5. Use a ball milling device to ball mill the silica powder and control the particle size to be below 100μm. Step 6. Place the ball-milled silica powder in a graphite crucible and melt it in a high-temperature furnace at 1500 to 1730 °C for 10 -1 to 10 -3 hours under a vacuum of 1 to 8 torr, and cool it in the furnace to form a bubble-free transparent glass, which is the neodymium-doped silica glass.

2. The preparation method of neodymium-doped silica glass with fluorescence spectrum blue-shifted to the 870 nm band as described in claim 1, characterized in that, The molar percentages of the components of the neodymium-doped silica glass are as follows: P2O5: 1mol% to 15mol%, Nd2O3: 0.05mol% to 0.8mol%, and the remaining component is SiO2.

3. The preparation method of neodymium-doped silica glass with a blue-shifted fluorescence spectrum to the 870 nm band as claimed in claim 1, characterized in that, The median particle size of the porous silica powder is in the micro-nano scale.

4. The preparation method of neodymium-doped silica glass with fluorescence spectrum blue-shifted to the 870 nm band according to claim 1, characterized in that, The silanolate is Si(OC2H5)4 or Si(OCH3)4. When the silanolate is Si(OC2H5)4, the organic solvent is C2H5OH; when the silanolate is Si(OCH3)4, the organic solvent is CH3OH.

5. The preparation method of neodymium-doped silica glass with fluorescence spectrum blue-shifted to 870 nm band, characterized in that, The hydrolysis catalyst of the silanolate is hydrochloric acid or ammonia water. When the hydrolysis catalyst of the silanolate is hydrochloric acid, the first pH value is 1 to 3; when the hydrolysis catalyst of the silanolate is ammonia water, the first pH value is 8 to 10.

6. The preparation method of neodymium-doped quartz glass with fluorescence spectrum blue-shifted to the 870 nm band according to claim 1, characterized in that, In Step 3, the fixed addition amount is 1 to 5g each time.

7. The preparation method of neodymium-doped fused silica glass with a fluorescence spectrum blue-shifted to the 870 nm band as claimed in claim 1, characterized in that, In Step 4, granulate the suspension by the rotary evaporation method.

8. A neodymium-doped silica glass with a fluorescence spectrum blue-shifted to the 870 nm band, characterized in that, Prepared by the preparation method of the neodymium-doped silica glass with the fluorescence spectrum blue-shifted to the 870nm band according to any one of Claims 1 to 7.

9. A neodymium-doped silica fiber preform, characterized in that, Prepared from the neodymium-doped silica glass with the fluorescence spectrum blue-shifted to the 870nm band according to Claim 8.

10. The neodymium-doped silica fiber preform according to claim 9, characterized in that, The neodymium-doped silica glass is cold-worked and polished to obtain an optical fiber core rod. The surface roughness of the optical fiber core rod is less than 10nm. After the optical fiber core rod is placed in hydrofluoric acid with a mass concentration of 5% to 20% for acid treatment for 5 to 15 minutes, it is taken out and dried to obtain a neodymium-doped silica optical fiber core rod.

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