Chloride photothermal sensitive glass, its preparation method and application

Abstract

The application relates to a chloride photothermal sensitive birefringent glass, a preparation method and application thereof. ‑ F in traditional fluoride photothermal sensitive birefringent glass is replaced by Cl ‑ And through optimization of component types and molar ratios, the prepared chloride photothermal sensitive birefringent glass can form nanocrystals Ag-AgCl / AgBr@NaCl with a core-shell structure after ultraviolet irradiation and heat treatment, can significantly improve the refractive index modulation capacity of the photothermal sensitive birefringent glass, realize positive refractive index modulation of Delta n>1000 ppm, and can effectively improve the laser damage threshold and reduce optical loss, and has a good application prospect in preparation of high-quality Bragg grating devices for high-energy high-power laser systems.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of diffractive optics, in particular to a chloride photo-thermo-refractive glass, a preparation method and application thereof. BACKGROUND

[0002] High-energy and high-power laser technology is an important symbol to measure the level of national high-end manufacturing and national defense science and technology, and it plays an irreplaceable role in strategic fields such as laser nuclear fusion energy development, super-strong and ultra-short pulse laser device, and directed energy weapon system. The volume Bragg grating based on photo-thermo-refractive (PTR) glass material has both angular spectrum and spectral selection capabilities, which can effectively improve the performance of high-energy and high-power laser systems, and has become the core optical element in the field of high-energy and high-power laser global regulation.

[0003] In order to realize stable global regulation of high-energy and high-power laser, high effective refractive index modulation, low optical loss and strong laser damage resistance are the core indicators of high-quality volume Bragg grating, and the above characteristics are directly affected by the quality fraction and size distribution of nano-crystallization formed in the PTR glass. The distribution of small size and high density of photo-thermal induced crystallization and effective inhibition of spontaneous crystallization are the key to obtain ideal grating structure of high-quality volume Bragg grating. The traditional fluoride PTR glass has serious spontaneous crystallization and phase separation, which leads to low effective refractive index modulation and serious scattering loss of grating device; and the unstable and easy to agglomerate and coarsen of the microcrystalline structure of the traditional fluoride PTR glass makes it difficult to realize the precise control of the cross-scale from nanometer to sub-micron required by the ideal grating structure, which becomes the bottleneck of its application in high-energy and high-power laser system.

[0004] Therefore, there is an urgent need for a photo-thermo-refractive glass that can overcome the problems of low refractive index modulation and serious scattering loss of existing fluoride PTR glass, and has higher laser damage resistance to meet the requirements of the next generation of high-energy and high-power laser system for high-performance volume Bragg grating and other components. SUMMARY

[0005] In order to solve the problems of low effective refractive index modulation, serious scattering loss and difficulty in realizing the cross-scale precision control from nanometer to micrometer of the existing fluoride photo-thermo-refractive glass, the present application provides a chloride photo-thermo-refractive glass and a preparation method and application thereof, which introduces Cl - instead of F in the traditional fluoride photo-thermo-refractive glass -And by optimizing the component types and molar proportions, the prepared chloride photothermal sensitive glass can form nanocrystals Ag-AgCl / AgBr@NaCl with core-shell structure after ultraviolet irradiation and heat treatment, can significantly improve the refractive index modulation capacity of the photothermal sensitive glass, realize positive refractive index modulation of Δn>1000 ppm, and can effectively improve the laser damage threshold and reduce optical loss, and has good application prospect in preparing high-quality Bragg grating devices for high-energy high-power laser systems.

[0006] Specifically, the following technical solutions are provided:

[0007] The first aspect of the present application provides a chloride photothermal sensitive glass, which comprises the following raw material components in terms of molar percentage: SiO2 59-75 mol.%, Al2O3 3-10 mol.%, Na2O 10-20 mol.%, NaCl 1-5 mol.%, ZnO 3-10 mol.%, Ag2O 0.005-0.01 mol.%, CeO2 0.005-0.02 mol.%, KX 0.25-1.5 mol.%, wherein X is Br and / or Cl.

[0008] The present application uses SiO2 as the main body oxide of the glass matrix, forms an irregular glass network structure in the form of silicon oxygen tetrahedron [SiO4], and controls the content of SiO2 in the glass in the range of 59-75 mol.% to avoid high glass melting temperature caused by high content, and to avoid easy phase separation and crystallization caused by low content. A proper amount of Al2O3 is introduced, Al2O3 as an intermediate oxide, can present multiple coordination states in the glass network structure, when the charge balance cation (such as Na + ) is sufficient, Al 3+ exists in the form of tetrahedral coordination [AlO4], acts as a network former, and has a similar effect to Si 4+ , to strengthen the network; when the charge balance cation (such as Na + ) is insufficient, Al 3+Alumina exists in the form of octahedral coordinated [AlO6], not participating in the construction of the network structure, but rather as a network modifier, which can disrupt the uniformity and continuity of the network structure. Therefore, the content of alumina in glass should not be too high or too low. When controlled within the range of 3-10 mol.%, it can enhance the network while avoiding increasing the tendency for exfoliation and crystallization, thereby improving the thermal stability, chemical stability, and mechanical strength of the glass. Simultaneously, introducing an appropriate amount (3-10 mol.%) of intermediate ZnO, existing in the glass as [ZnO4] and [ZnO6], can improve the chemical stability of the glass, reduce the glass expansion coefficient, and eliminate streaks and bubbles. Furthermore, Na2O is introduced as a network modifier, not participating in the construction of the glass network structure, but providing free Na... + and O - , where Na + Able to and Cl - Combined with the formation of NaCl crystals during crystallization, O - Introducing Na2O can increase the O / Si ratio in the glass network structure, reduce glass viscosity and melting temperature, and is beneficial for glass clarification. However, the introduction of Na2O will increase the coefficient of thermal expansion of the glass. To avoid the excessive introduction of Na2O from having a significant impact on thermal stability, chemical stability and mechanical strength, the Na2O content needs to be controlled within 10-20 mol.%.

[0009] In addition, an appropriate amount of CeO2 is added as a photosensitizer for PTR glass to introduce the photosensitizing factor Ce. 3+ CeO2 absorbs photon energy in the ultraviolet region and releases free electrons through oxidation. However, the introduction of a large amount of CeO2 will significantly increase the absorption of the glass in the ultraviolet region, causing the ultraviolet absorption edge to shift towards the visible light band. Therefore, the introduction of CeO2 should not be excessive, and the CeO2 content should be controlled within the range of 0.005-0.01 mol.%. Simultaneously, an appropriate amount of Ag2O is added as a photosensitizer and thermal nucleating agent. On the one hand, Ag element in the matrix glass... + It exists in the form of Ce, capable of capturing Ce 3+ The released free electrons endow PTR glass with photosensitive properties; simultaneously, during subsequent nucleation heat treatment, Ag-NPs can be formed as the nucleation basis for nanocrystals, inducing uniform crystallization. However, excessive Ag2O addition will lead to over-crystallization and coarsening of crystal particles during ultraviolet irradiation and heat treatment, resulting in problems such as decreased glass transparency and increased light loss. Therefore, the Ag2O content needs to be controlled within a suitable range, such as 0.005-0.01 mol%.

[0010] More importantly, this invention replaces sodium fluoride in traditional fluoride photothermal refractive glass with an appropriate amount of NaCl, providing free Na to the glass matrix. +and Cl - Na + and Cl - During the crystallization heat treatment step, silver nuclei precipitate, combined with the X provided by the raw material composition KX. - A large number of small-sized, high-density nanocrystals with a core-shell structure, Ag-AgX@NaCl (X is Br and / or Cl), are formed, which are compared with traditional fluoride PTR glass. n NaF Compared to (=1.32), due to the refractive indices of bromides and chlorides of Na and Ag ( n NaCl =1.54, n AgBr =2.23, n AgCl =2.05) are all higher than the matrix glass ( n matrix =1.49), enabling chloride photothermal refractive glass containing these nanocrystals to achieve positive refractive index modulation in the irradiated region. The introduced NaCl exists as the main crystalline phase component precipitated in the PTR glass, but Cl... - X - Excessive NaCl and KX content will increase the tendency for glass phase separation and crystallization, affecting the chemical stability and optical properties of photothermal refractive glass. Therefore, the content of NaCl and KX needs to be controlled within an appropriate range, such as 1-5 mol.% NaCl and 0.25-1 mol.% KX.

[0011] The chloride photothermal refractive glass provided by this invention significantly improves the refractive index modulation capability of the photothermal refractive glass under the synergistic effect of the above-mentioned raw material components, and can achieve positive refractive index modulation of Δn>1000 ppm, and can effectively improve the laser damage resistance threshold and reduce optical loss.

[0012] Furthermore, when KX is KBr, the provided Br - It can also be used as a reducing agent for different forms of Ag in glass, and is beneficial to the photosensitizer Ce. 3+ The formation of.

[0013] Furthermore, the chloride photothermal refractive glass also contains the following raw material components in molar percentage: SnO2 0.005-0.01 mol.% and Sb2O3 0.01-0.05 mol.%. The primary functions of SnO2 and Sb2O3 are as thermal reducing agents and pre-sensitizers, with Ce introduced into the batch as CeO2. 4+ During the melting process, SnO2 and Sb2O3 are needed to reduce it to Ce. 3+ Furthermore, SnO2 and Sb2O3 can also thermally reduce a portion of Ag. + Sb5+ In the PTR glass photosensitive process, a part of free electrons are captured to form negatively charged Sb complex, and the nucleation process [Sb 5+ ] - carrying loose electrons will be captured by the remaining Ag + , thereby increasing the concentration of neutral Ag 0 atoms and molecular clusters. SnO2 and Sb2O3 are both low in content in the PTR glass, and too high content will cause the glass to be colored and increase the risk of non-functional crystal precipitation, and the mutual reaction of SnO2 and Sb2O3 during the melting process, resulting in the presence of Sn 2+ / Sn 4+ and Sb 3+ / Sb 5+ in the PTR glass, but only Sn 2+ and Sb 3+ have reducing power, and too much Sb2O3 will also cause the reaction between SnO2 and Sb2O3 to increase, and more Sb 3+ is oxidized to Sb 5+ , thereby losing reducing power. Therefore, preferably, the content of SnO2 is controlled within the range of 0.005-0.01 mol.%, and the content of Sb2O3 is controlled within the range of 0.01-0.05 mol.%.

[0014] Further, the melting temperature of the chloride photothermal sensitive glass is in the range of 1400-1500 ℃, more preferably 1425-1460 ℃.

[0015] Further, the laser damage threshold of the glass is >20 J / cm 2 @1064 nm@8 ns, and the spontaneous crystallization activation energy is >250 KJ / mol; more preferably, the laser damage threshold of the glass is >25 J / cm 2 @1064 nm@8 ns, and the spontaneous crystallization activation energy is >280 KJ / mol.

[0016] Further, after the chloride photothermal sensitive glass is irradiated by ultraviolet light and heat treated, nanocrystals with core-shell structure are generated inside the glass, forming a chloride photothermal sensitive glass with refractive index modulation; the nanocrystals include Ag core, first cladding layer and second cladding layer arranged from inside to outside, the first cladding layer contains AgCl and AgX, and the second cladding layer contains NaCl.

[0017] Further, the ultraviolet irradiation is specifically: using a 325 nm He-Cd laser to expose the chloride photothermal sensitive deformable glass; in the step of the exposure treatment, the irradiation power is preferably 5-50 mW, and the irradiation time is preferably 1000-3000 s. By the ultraviolet irradiation treatment, Ag + is reduced to Ag 0 clusters.

[0018] Further, the heat treatment is specifically: first, increasing the temperature to T g + (30-50) ℃ at a rate of 5-10 ℃ / min, keeping for 1-2 hours to form a nucleus, to form Ag 0 @ AgX structure silver nanoparticles, then cooling to T g -20 ℃ at a rate of 2-5 ℃ / min, condensing for 10-20 minutes to form more tiny silver nanoparticles as a crystal nucleus basis, and then increasing the temperature to T g + (50-100) ℃ at a rate of 5-10 ℃ / min, keeping for 1-2 hours to induce NaCl microcrystal growth, to form the nanocrystal with core-shell structure; the T g is the glass transition temperature of the chloride photothermal sensitive deformable glass; preferably, the T g is 460-480 ℃, more preferably 465-480 ℃.

[0019] Further, the refractive index of the chloride photothermal sensitive deformable glass with refractive index modulation is between 1.501-1.503, the maximum refractive index modulation Δn is greater than 1000, and in some preferred embodiments, the maximum refractive index modulation Δn can reach 1500 ppm or more.

[0020] Further, the light absorption coefficient of the chloride photothermal sensitive deformable glass with refractive index modulation in the 532 nm wave band ranges from 0.01 to 0.03 cm -1 , more preferably 0.01-0.025 cm -1 , showing extremely low absorption loss.

[0021] Further, the light absorption coefficient of the chloride photothermal sensitive deformable glass with refractive index modulation in the 1064 nm wave band ranges from 0.005 to 0.02 cm -1 , more preferably 0.005-0.01 cm -1 , showing extremely low absorption loss.

[0022] The second aspect of the present application provides a preparation method of the chloride photothermal sensitive deformable glass of the first aspect, comprising the following steps:

[0023] (1) Each raw material component is weighed according to the raw material formula of the chloride photothermal sensitive devitrification glass, and mixed, and then screened and ground to obtain a uniform mixed powder;

[0024] (2) The mixed powder is heated and melted into a glass liquid at 1420-1500 ℃ under the protection of N2 / O2 mixed gas, the liquid level height of the glass liquid in the container is controlled to be 180-210 mm, then the temperature is raised to 1500-1520 ℃ for the first stirring treatment, and after the viscosity of the glass liquid reaches 1.9-2.1 Log Pa·S, the temperature is lowered to 1480-1500 ℃ for the second stirring treatment, to obtain a glass liquid to be shaped;

[0025] (3) The glass liquid to be shaped is poured into a preheated mold, cooled to a glass transition temperature T g in air, then transferred to a heating device and kept at a temperature T g for 2-4 h, and then slowly cooled to 15-35 ℃ at a rate of 0.5-1 ℃ / min, and the glass after cooling is polished to obtain the chloride photothermal sensitive devitrification glass.

[0026] Further, in step (1), the mixed raw materials are screened to improve the purity and uniformity of the ingredients, and ground to ensure that the finally prepared glass has stable composition and uniform structure; in some preferred embodiments, the mesh size of the screening is 200 mesh.

[0027] Further, in step (2), the raw materials are melted into a glass liquid at a relatively low temperature (1420-1500 ℃) to avoid excessive temperature loss or deterioration of the components, and the liquid level height is controlled to be 180-210 mm, which is too high will cause the glass liquid to overflow the crucible and cause safety hazards, and too low will cause bubbles to be unable to be fully removed; then the temperature is gradually raised (1500-1520 ℃) to reduce the viscosity of the glass liquid, and then fully stirred and homogenized and clarified, the stirring parameters are 20-30 Hz, and the stirring time is 5-8 h to remove the bubbles and stripes in the glass liquid. After reaching the suitable viscosity range for shaping, the temperature is lowered again (1480-1500 ℃) for further stirring, homogenization and shaping, the stirring parameters are 20-30 Hz, and the stirring time is 2-3 h.

[0028] Further, in step (3), before pouring the glass liquid to be shaped, a layer of lubricant is applied to the inner surface of the mold, and then preheated, the preheating temperature is 500-600 ℃; after pouring the glass liquid to be shaped into the preheated mold, the glass melt is fully filled in the space of the mold by gravity, vibration or pressure, etc., to ensure that the shape and size of the shaped glass meet the requirements.

[0029] Further, in step (3), the polishing treatment is specifically: after the glass is completely cooled and solidified, the finished product is taken out of the mold, and then the finished product is subjected to trimming, deburring and other treatments to make the surface smooth and flat, and the polishing process is divided into four processes of rough grinding, fine grinding, precision grinding and polishing. The polished sample with the required size and shape is prepared from the cooled glass.

[0030] The third aspect of the present application provides a use of the chloride photothermal sensitive birefringent glass of the first aspect or the chloride photothermal sensitive birefringent glass prepared by the preparation method of the second aspect in preparing a body Bragg grating device.

[0031] The fourth aspect of the present application provides a glass preform made of the chloride photothermal sensitive birefringent glass of the first aspect or the chloride photothermal sensitive birefringent glass prepared by the preparation method of the second aspect.

[0032] The fifth aspect of the present application provides an optical element made of the chloride photothermal sensitive birefringent glass of the first aspect or the chloride photothermal sensitive birefringent glass prepared by the preparation method of the second aspect.

[0033] The sixth aspect of the present application provides a laser comprising the optical element of the fifth aspect.

[0034] Compared with the prior art, the present application has the beneficial effects that:

[0035] The present application provides a chloride photothermal sensitive birefringent glass, by introducing Cl - instead of F in the traditional fluoride photothermal sensitive birefringent glass - , and by optimizing the types and molar ratios of components, the prepared chloride photothermal sensitive birefringent glass can form nanocrystals Ag-AgX@NaCl with core-shell structure after ultraviolet irradiation and heat treatment, which can significantly improve the refractive index modulation ability of the photothermal sensitive birefringent glass, realize a strong refractive index gradient of Δn>1000 ppm (positive modulation), and is expected to break through the effective refractive index modulation limit of the traditional fluoride system.

[0036] In the photothermal-induced crystallization process, the present application adopts a multi-step heat treatment method to optimize the crystallization, crystal size and distribution of the chloride photothermal sensitive birefringent glass, form smaller and more fine microcrystalline structures, and effectively avoid the formation of large-size crystals and agglomeration caused by continuous heat treatment.

[0037] The chloride photothermal sensitive deformation glass provided by the application has the uniform and stable characteristics of microcrystal morphology, and the Ag-AgX@NaCl core-shell structure crystal phase formed by the induced crystallization of ultraviolet irradiation and heat treatment presents a highly single dispersed spherical structure (size < 30 nm), and the size uniformity has a magnitude advantage compared with the traditional fluoride PTR glass system.

[0038] The chloride photothermal sensitive deformation glass provided by the application has the high-density crystal nucleus characteristics, and the nucleation center density is significantly improved through the doping of Cl - The traditional F - is replaced, and the doping concentration of Ag + in the glass matrix is effectively improved, so that the nucleation center density is significantly improved, the spontaneous crystallization is inhibited, and the uniformity and consistency of the microcrystal distribution are cooperatively optimized.

[0039] The transmission type volume Bragg grating prepared from the chloride photothermal sensitive deformation glass provided by the application has a high diffraction efficiency, the peak diffraction efficiency is not less than 94% at a 532 nm incident wavelength, the peak diffraction efficiency is not less than 93% at a 1053 nm incident wavelength, and the absorption and scattering loss is small. Therefore, the chloride photothermal sensitive deformation glass provided by the application has a good application prospect in the preparation of high-quality volume Bragg grating devices for high-energy and high-power laser systems. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 The melting process parameter diagram of the photothermal sensitive deformation glass for the examples and comparative examples is shown in the figure;

[0041] Figure 2 The mechanism diagram of the photothermal induced crystallization treatment of the chloride photothermal sensitive deformation glass is shown in the figure;

[0042] Figure 3 The XRD spectrum and TEM morphology diagram of the chloride photothermal sensitive deformation glass prepared in Example 1 after the photothermal induced crystallization are shown in the figure;

[0043] Figure 4 The change curve of the refractive index of the chloride photothermal sensitive deformation glass prepared in Example 1 after the photothermal induced crystallization treatment with the extension of the holding time of the second heat treatment is shown in the figure;

[0044] Figure 5 The SEM micro-morphology diagram of the nanocrystals precipitated from the chloride photothermal sensitive deformation glass prepared in Comparative Example 1 after the photothermal induced crystallization treatment is shown in the figure; wherein, (a) is the SEM diagram of the second heat treatment holding time of 10 min, (b) is the SEM diagram of the second heat treatment holding time of 30 min, (c) is the SEM diagram of the second heat treatment holding time of 60 min, and (d) is the SEM diagram of the second heat treatment holding time of 120 min;

[0045] Figure 6 SEM micrographs of the nanocrystals precipitated from the chloride photothermal sensitive glass prepared in Comparative Example 2 after photothermal induced crystallization treatment; wherein, (a) is the SEM micrograph of the second step heat treatment with 10 min holding time, (b) is the SEM micrograph of the second step heat treatment with 30 min holding time, (c) is the SEM micrograph of the second step heat treatment with 60 min holding time, (d) is the SEM micrograph of the second step heat treatment with 120 min holding time;

[0046] Figure 7 SEM micrographs of the nanocrystals precipitated from the fluoride photothermal sensitive glass prepared in Comparative Example 3 after photothermal induced crystallization treatment; wherein, (a) is the SEM micrograph of the second step heat treatment with 10 min holding time, (b) is the SEM micrograph of the second step heat treatment with 30 min holding time, (c) is the SEM micrograph of the second step heat treatment with 60 min holding time, (d) is the SEM micrograph of the second step heat treatment with 120 min holding time;

[0047] Figure 8 SEM micrographs of the nanocrystals precipitated from the chloride photothermal sensitive glass prepared in Comparative Example 4 after photothermal induced crystallization treatment without cooling step; wherein, (a) is the SEM micrograph of the second step heat treatment with 10 min holding time, (b) is the SEM micrograph of the second step heat treatment with 30 min holding time, (c) is the SEM micrograph of the second step heat treatment with 60 min holding time, (d) is the SEM micrograph of the second step heat treatment with 120 min holding time;

[0048] Figure 9 Diffractive properties of the transmission volume Bragg grating prepared from the chloride photothermal sensitive glass prepared in Example 1 after photothermal induced crystallization treatment; wherein, (a) is the angle selection property of the transmission volume Bragg grating and the near field distribution of the incident light and the diffracted light under the condition of 532 nm incident wavelength, (b) is the angle selection property of the transmission volume Bragg grating and the near field distribution of the incident light and the diffracted light under the condition of 1053 nm incident wavelength;

[0049] Figure 10 SEM micrographs of the nanocrystals of the transmission volume Bragg grating prepared from the chloride photothermal sensitive glass prepared in Example 1 after photothermal induced crystallization treatment. DETAILED DESCRIPTION

[0050] The present application will be further described below in conjunction with the drawings and specific embodiments, so that those skilled in the art can better understand the present application and implement it.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for describing particular embodiments only and is not intended to be limiting of the application. As used in the description of the application the terms "including", "containing", "having" and the like are not intended to exclude other additives, components, integers or steps. Throughout this international patent application, the word "comprise" or "comprising" or "include" or "including" means "including but not limited to".

[0052] Example 1: This example relates to the preparation of a chloride photothermal sensitive devitrification glass and its photothermal induced devitrification treatment, the specific operation is as follows:

[0053] The preparation of the chloride photothermal sensitive devitrification glass is specifically as follows:

[0054] (1) According to the raw material formula: SiO2 69.95 mol.%, Al2O3 5 mol.%, Na2O 13.5 mol.%, NaCl 5 mol.%, ZnO 5 mol.%, Ag2O 0.01 mol.%, CeO2 0.02 mol.%, KBr 0.75 mol.%, KCl 0.75 mol.%, SnO2 0.01 mol.%, Sb2O3 0.01 mol.%, each raw material is weighed and mixed, the mixed raw materials are screened using a 200 mesh sieve, then poured into a mortar for mixing and grinding to obtain a uniform mixed powder.

[0055] (2) Put the mixed powder into a 1 L platinum crucible for heating and melting treatment, the specific heating program and charging process are as shown in Figure 1 : from 50 ℃ to 800 ℃ (60 min), keep for 30 min, then from 800 ℃ to 1420-1460 ℃ (30 min), add half of the mixed powder, then keep for 30 min and add the remaining mixed powder, heat to 1480-1500 ℃ (within 10 min), keep for 60 min, then continue to stir at a stirring speed of 30 r / min for 60 min at the temperature, heat to 1510-1520 ℃ (within 10 min), keep for 30 min, then cool to 1480-1500 ℃ (within 10 min) to discharge, to obtain a glass liquid to be formed.

[0056] (3) First, prepare a metal mold of suitable shape and size, apply a layer of lubricant to the inner surface of the mold to facilitate subsequent removal of the formed glass product. The mold needs to be preheated in a muffle furnace before pouring, the temperature is 500-600 ℃. The above glass liquid to be formed is taken out from the electric furnace and slowly and uniformly poured into the prepared mold, naturally cooled to the glass transition temperature T g (470 ℃) in air, then put into a muffle furnace, heat to the glass transition temperature Tg Annealing 2 h, finally cooling to room temperature with a rate of 0.1 ℃ / min, taking out from the mold, cutting and polishing to get the chloride photothermal sensitive glass.

[0057] The photothermal induced crystallization process is as follows:

[0058] (1) UV irradiation treatment: using 325 nm He-Cd laser to expose the cut and polished chloride PTR glass sample, irradiation power: 50 mW, irradiation time: 1800 s.

[0059] (2) "two-step" heat treatment: first, heating to 500 ℃ at a rate of 10 ℃ / min for 2 hours to nucleate, then cooling to 450 ℃ at a rate of 5 ℃ / min for 20 minutes to condense; and then the second step, heating to 550 ℃ at a rate of 10 ℃ / min for 0.5-3 hours to crystallize.

[0060] As shown in Figure 2 , the chloride photothermal sensitive glass can form nanocrystals with Ag-AgCl / AgBr@NaCl core-shell structure as the crystalline phase after photothermal induced crystallization treatment, and the specific XRD pattern and TEM microstructure are shown in Figure 3 , the NaCl nanocrystals precipitated by photothermal induction are spherical structure, with an average size of less than 30 nm, and can form a large number of nucleation centers in the glass matrix. The small size and high density of nanocrystals make the chloride photothermal sensitive glass after photothermal induced crystallization treatment can maintain high refractive index modulation, while significantly reducing optical loss.

[0061] Figure 4 The refractive index of the chloride photothermal sensitive glass after photothermal induced crystallization treatment changes with the extension of the second step heat treatment holding time, as shown in the figure, the refractive index of the chloride PTR glass increases from 1.501 to 1.503, and the maximum refractive modulation is more than 1500 ppm. Combined with the XRD pattern in Figure 3 , it can be seen that the increase of the glass refractive index is due to the precipitation of Ag-AgCl / AgBr@NaCl nanocrystal phase composed of mixed sodium and silver chloride in the ultraviolet irradiation area. Compared with the traditional fluoride PTR glass ( n NaF =1.32), the refractive index of Na and Ag bromide and chloride ( n NaCl =1.54, n AgBr =2.23, n AgCl =2.05) are all higher than the matrix glass ( n matrix=1.49), the positive refractive index modulation of the chloride PTR glass in the irradiation region can be achieved, and the decline of the modulation efficiency caused by the inconsistency of the refractive index of the core and shell is avoided.

[0062] Example 2: This example relates to the preparation of a chloride photothermal sensitive refractive glass and the photothermal induced crystallization treatment thereof, and the difference from Example 1 is only that the raw material formula of the chloride photothermal sensitive refractive glass is specific: SiO2 59.95 mol.%, Al2O3 5 mol.%, Na2O 20 mol.%, NaCl 5 mol.%, ZnO 8.5 mol.%, Ag2O 0.01 mol.%, CeO2 0.02 mol.%, KBr 0.75 mol.%, KCl 0.75 mol.%, SnO2 0.01 mol.%, Sb2O3 0.01 mol.%. The remaining operations are consistent, and the chloride photothermal sensitive refractive glass after the photothermal induced crystallization treatment is prepared.

[0063] The chloride photothermal sensitive refractive glass after the photothermal induced crystallization treatment can form nanocrystals with Ag-AgCl / AgBr@NaCl core-shell structure as the crystalline phase, the average size is within 30 nm, and the maximum refractive modulation of the prepared chloride photothermal sensitive refractive glass is 1500 ppm.

[0064] Example 3: This example relates to the preparation of a chloride photothermal sensitive refractive glass and the photothermal induced crystallization treatment thereof, and the difference from Example 1 is only that the raw material formula of the chloride photothermal sensitive refractive glass is specific: SiO2 64.95 mol.%, Al2O3 5 mol.%, Na2O 15 mol.%, NaCl 5 mol.%, ZnO 8.5 mol.%, Ag2O 0.01 mol.%, CeO2 0.02 mol.%, KBr 0.75 mol.%, KCl 0.75 mol.%, SnO2 0.01 mol.%, Sb2O3 0.01 mol.%. The remaining operations are consistent, and the chloride photothermal sensitive refractive glass after the photothermal induced crystallization treatment is prepared.

[0065] The chloride photothermal sensitive refractive glass after the photothermal induced crystallization treatment can form nanocrystals with Ag-AgCl / AgBr@NaCl core-shell structure as the crystalline phase, the average size is within 30 nm, and the maximum refractive modulation of the prepared chloride photothermal sensitive refractive glass is 1500 ppm.

[0066] Example 4: This example relates to a preparation of a chloride photothermal sensitive devitrification glass and a photothermal induced devitrification treatment thereof, which is only different from example 1 in that the raw material formula of the chloride photothermal sensitive devitrification glass is specifically: SiO2 67.95 mol.%, Al2O3 4 mol.%, Na2O 15 mol.%, NaCl 3 mol.%, ZnO 8.5 mol.%, Ag2O 0.01 mol.%, CeO2 0.02 mol.%, KBr 0.75 mol.%, KCl 0.75 mol.%, SnO2 0.01 mol.%, Sb2O3 0.01 mol.%. The remaining operations are consistent, and a chloride photothermal sensitive devitrification glass after a photothermal induced devitrification treatment is prepared.

[0067] The chloride photothermal sensitive devitrification glass after the photothermal induced devitrification treatment can form nanocrystals with Ag-AgCl / AgBr@NaCl core-shell structure as a devitrification phase, the average size is within 30 nm, and the maximum refractive modulation of the prepared chloride photothermal sensitive devitrification glass is 1500 ppm.

[0068] Example 5: This example relates to a preparation of a chloride photothermal sensitive devitrification glass and a photothermal induced devitrification treatment thereof, which is only different from example 1 in that the raw material formula of the chloride photothermal sensitive devitrification glass is specifically: SiO2 69.95 mol.%, Al2O3 5.5 mol.%, Na2O 15 mol.%, NaCl 5 mol.%, ZnO 3 mol.%, Ag2O 0.01 mol.%, CeO2 0.02 mol.%, KBr 0.75 mol.%, KCl 0.75 mol.%, SnO2 0.01 mol.%, Sb2O3 0.01 mol.%. The remaining operations are consistent, and a chloride photothermal sensitive devitrification glass after a photothermal induced devitrification treatment is prepared.

[0069] The chloride photothermal sensitive devitrification glass after the photothermal induced devitrification treatment can form nanocrystals with Ag-AgCl / AgBr@NaCl core-shell structure as a devitrification phase, the average size is within 30 nm, and the maximum refractive modulation of the prepared chloride photothermal sensitive devitrification glass is 1600 ppm.

[0070] Example 6: This example relates to a preparation of a chloride photothermal sensitive devitrification glass and a photothermal induced devitrification treatment thereof, which is only different from example 1 in that the raw material formula of the chloride photothermal sensitive devitrification glass is specifically: SiO2 59.95 mol.%, Al2O3 8.5 mol.%, Na2O 15 mol.%, NaCl 5 mol.%, ZnO 10 mol.%, Ag2O 0.01 mol.%, CeO2 0.02 mol.%, KBr 0.75 mol.%, KCl 0.75 mol.%, SnO2 0.01 mol.%, Sb2O3 0.01 mol.%. The remaining operations are consistent, and a chloride photothermal sensitive devitrification glass after a photothermal induced devitrification treatment is prepared.

[0071] The chloride photothermal sensitive devitrification glass after the photothermal induced devitrification treatment can form nanocrystals with Ag-AgCl / AgBr@NaCl core-shell structure as the devitrification phase, the average size is within 30 nm, and the maximum refractive modulation of the prepared chloride photothermal sensitive devitrification glass is 1600 ppm.

[0072] Comparative Example 1: This comparative example relates to a preparation of a chloride photothermal sensitive devitrification glass and a photothermal induced devitrification treatment thereof, which is only different from example 1 in that the content of SiO2 in the raw material formula of the chloride photothermal sensitive devitrification glass is too much, and the content of Na2O is too little, specifically: SiO2 79.94 mol.%, Al2O3 7.5 mol.%, Na2O 7.5 mol.%, ZnO 2.5 mol.%, Ag2O 0.02 mol.%, CeO2 0.02 mol.%, KBr 1.25 mol.%, KCl 1.25 mol.%, SnO2 0.01 mol.%, Sb2O3 0.01 mol.%. The remaining operations are consistent, and a chloride photothermal sensitive devitrification glass after a photothermal induced devitrification treatment is prepared.

[0073] The nanocrystal morphology of the chloride photothermal sensitive devitrification glass prepared in the comparative example after the photothermal induced devitrification treatment is as shown in Figure 5As shown in FIG. 6, the surface of the PTR glass is very smooth with only a few nanocrystals with a diameter of about 100 nm under the condition of isothermal crystallization heat treatment time less than 30 minutes at 550 °C, indicating that the supersaturation of the PTR glass matrix is low under the above isothermal heat treatment condition, and the crystallization heat treatment time is not enough to support the full growth of the nanocrystals. Under the condition of long-time isothermal crystallization heat treatment (> 60 minutes), the size of the nanocrystals increases significantly, but the grain density decreases significantly. The change of the size and density of the nanocrystals is due to the decrease of the homogeneous nucleation rate caused by the increase of the SiO2 content and the decrease of the Na2O content, the increase of the thermodynamic driving force of the crystal growth around the single nucleation point, the increase of the interaction between the grains, and the intensification of the grain aggregation growth. The distribution of the above low-density and large-size nanocrystals is not suitable for the preparation of high-quality volume Bragg gratings.

[0074] The maximum refractive modulation of the chloride photothermal sensitive glass prepared in the present comparative example is 300 ppm.

[0075] Comparative Example 2: The present comparative example relates to the preparation of a chloride photothermal sensitive glass and the photothermal induced crystallization treatment thereof, which is only different from Example 1 in that the SiO2 content in the raw material formula of the chloride photothermal sensitive glass is too low and the Na2O content is too high, specifically: SiO2 57.45 mol.%, Al2O3 10.99 mol.%, Na2O 25 mol.%, ZnO 5 mol.%, Ag2O 0.02 mol.%, CeO2 0.02 mol.%, KBr 1.25 mol.%, KCl 1.25 mol.%, SnO2 0.01 mol.%, Sb2O3 0.01 mol.%. The remaining operations are consistent, and the chloride photothermal sensitive glass after the photothermal induced crystallization treatment is prepared.

[0076] The morphology of the nanocrystals precipitated after the photothermal induced crystallization treatment of the chloride photothermal sensitive glass prepared in the present comparative example is shown in FIG. 7. Figure 6 As shown in FIG. 7, the area of the crystallization phase increases significantly and the area of the remaining glass matrix gradually decreases under the condition of prolonging the crystallization heat treatment time at 550 °C, indicating that the relative crystallinity of the PTR glass increases. In addition, a region without crystallization can be observed around the large-diameter nanocrystals, and many smaller crystals are distributed around the region, forming a microstructure called "courtyard". The formation of the "courtyard" structure is due to the consumption of free Na + and Cl - ions to form a diffusion zone, and the significant increase in the viscosity of the glass in this region hinders the outward diffusion of Na +Ion diffusion inhibits crystal growth. Furthermore, the "garden" structure formed by high grain density is also unsuitable for the fabrication of high-quality bulk Bragg gratings.

[0077] The maximum refractive modulation of the chloride photothermal refractive glass prepared in this comparative example was 600 ppm.

[0078] Comparative Example 3: This comparative example relates to the preparation of a fluoride photothermal refractive glass and its photothermal induced crystallization treatment. The only difference from Example 1 is that the raw material formulation of the photothermal refractive glass uses an equimolar amount of NaF instead of NaCl. All other operations are the same, and a fluoride photothermal refractive glass after photothermal induced crystallization treatment is obtained.

[0079] The morphology of the nanocrystals precipitated after photothermal-induced crystallization treatment of the fluoride photothermal refractive glass prepared in this comparative example is as follows: Figure 7 As shown, the precipitation of the NaF crystalline phase in PTR glass exhibits a clear structural evolution. Initially, the NaF crystalline phase is needle-like and distributed within the glass matrix. Over time and with the continuation of the growth process, these needle-like crystals gradually transform into more complex dendritic structures. Under prolonged growth conditions, the dendrites gradually increase in size, eventually forming dendritic structures with an average size exceeding 1 μm, significantly increasing the glass's scattering surface. The precipitation of these large crystals not only leads to a decrease in the glass's optical properties and increases the scattering effect but also induces significant opacity, which has extremely adverse effects on the glass's transparency and final application.

[0080] The maximum refractive modulation of the fluoride photothermal refractive glass prepared in this comparative example was 1000 ppm.

[0081] Comparative Example 4: This comparative example relates to the preparation of a chloride photothermal refractive glass and its photothermal induced crystallization treatment. The only difference from Example 1 is that the photothermal induced crystallization heat treatment process does not include a cooling step. All other operations are the same, and a chloride photothermal refractive glass after photothermal induced crystallization treatment is obtained.

[0082] The morphology of the nanocrystals precipitated after photothermal-induced crystallization treatment of the chloride photothermal refractive glass prepared in this comparative example is as follows: Figure 8As shown, without the cooling treatment step, the final size of the precipitated crystals is significantly increased compared to the embodiment. During the multi-step heat treatment process, the crystal size can quickly reach a saturation state, showing the characteristics of small crystal size distribution. During the subsequent heat treatment process, the size of the crystals does not change significantly, indicating that the multi-step heat treatment can effectively control the growth of the crystals. In contrast, samples using continuous heat treatment will exhibit significant crystal growth and agglomeration. The results show that the use of multi-step heat treatment (including cooling steps) can significantly enhance the induced crystallization behavior and is the key to the formation of smaller and finer microcrystalline structures.

[0083] The maximum refractive modulation of the fluoride photothermal sensitive glass prepared in the comparative example is 700 ppm.

[0084] Application and performance test: (1) Application of chloride PTR glass in the preparation of transmission volume Bragg grating

[0085] Taking the chloride PTR glass prepared in Example 1 as an example, the chloride PTR glass after photothermal induced crystallization treatment is used to prepare a transmission volume Bragg grating with a high diffraction efficiency of 2 μm. The diffraction characteristics are as shown in Figure 9 The peak diffraction efficiency is 94.4% at an incident wavelength of 532 nm (the diffraction efficiency of the chloride PTR glass prepared in Comparative Example 4 is 85.2%), and the peak diffraction efficiency is 93.2% at an incident wavelength of 1053 nm (the diffraction efficiency of the chloride PTR glass prepared in Comparative Example 4 is 83.4%). In the case of incident wavelengths of 532 nm and 1053 nm, the near-field distribution of the diffracted light of the high-diffraction-efficiency transmission volume Bragg grating under the condition of collimated Gaussian light with a spot diameter of 10 mm and satisfying the Bragg condition. After being diffracted by the high-diffraction-efficiency transmission volume Bragg grating, most of the incident light energy is diffracted. At incident wavelengths of 532 nm and 1053 nm, the intensity of the diffracted light of the transmission volume Bragg grating is very close to the intensity of the incident light, indicating that the prepared high-diffraction-efficiency transmission volume Bragg grating has small absorption loss in the visible and near-infrared wavelength bands. In addition, the transmission volume Bragg grating has small scattering loss caused by large-size nanocrystals, and the diffracted light does not have obvious scattering rings, and the near-field distribution can basically remain consistent with the incident light.

[0086] (2) Study on the crystal distribution in the volume Bragg grating prepared from the chloride PTR glass

[0087] The surface of the bulk Bragg grating prepared from the chloride PTR glass prepared in Example 1 was corroded by HF solution to obtain the internal micro-morphology thereof. After being corroded by 2% HF solution for 20 minutes, the internal grating period structure of the bulk Bragg grating was exposed. Due to the different acid corrosion rates of the glass matrix and the crystalline phase, the UV irradiation area containing more nanocrystals was less corroded by the acid, while the un-irradiated area containing less crystals was more corroded by the acid. It can be seen from Figure 2 that the nanocrystals in the grating period structure of the bulk Bragg grating prepared from the chloride PTR glass prepared in Example 1 have a density of 10 Figure 10 orders of magnitude, and the average size thereof can reach about 25 nm. 21

[0088] The above-described examples are only preferred examples for fully illustrating the present application, and the protection scope of the present application is not limited thereto. Any equivalent replacement or transformation made by the skilled in the art on the basis of the present application is within the protection scope of the present application. The protection scope of the present application is subject to the claims.​

Claims

1. A chloridized photothermal sensitive devitrifying glass having a refractive index modulation, characterized in that, The chloride photothermal sensitive birefringent glass generates nanocrystals with a core-shell structure in the glass after ultraviolet irradiation and heat treatment, forming a chloride photothermal sensitive birefringent glass with refractive index modulation; the nanocrystals comprise, from inside to outside, an Ag core, a first coating layer and a second coating layer, the first coating layer comprises AgX, and the second coating layer comprises NaCl; The chloride photothermal sensitive birefringent glass is composed of the following raw material components in terms of mole percentage: SiO2 59-75 mol.%, Al2O3 3-10 mol.%, Na2O 10-20 mol.%, NaCl 1-5 mol.%, ZnO 3-10 mol.%, Ag2O 0.005-0.01 mol.%, CeO2 0.005-0.02 mol.%, KX 0.25-1.5 mol.%, wherein X is Br and / or Cl; The heat treatment is specifically: first, heating to T g + (30-50) ℃ at a rate of 5-10 ℃ / min, holding for 1-2 hours to form nuclei, then cooling to T g -20 ℃ at a rate of 2-5 ℃ / min, condensing for 10-20 minutes to form a large number of tiny crystal nuclei, and then heating to T g + (50-100) ℃ at a rate of 5-10 ℃ / min, holding for 1-2 hours to crystallize; and T g is the glass transition temperature of the chloride photo-thermal sensitive devitrification glass. The chloride photothermal sensitive reversible glass with refractive index modulation has a light absorption coefficient in the range of 0.01-0.03 cm for 532 nm waveband -1 .

2. The chlorid e photothermal sensitive glass with refractive index modulation according to claim 1, characterized in that, The chloride photothermal sensitive birefringent glass is composed of the following raw material components in terms of mole percentage: SiO2 59-75 mol.%, Al2O3 3-10 mol.%, Na2O 10-20 mol.%, NaCl 1-5 mol.%, ZnO 3-10 mol.%, Ag2O 0.005-0.01 mol.%, CeO2 0.005-0.02 mol.%, KX 0.25-1.5 mol.%, SnO2 0.005-0.01 mol.% and Sb2O3 0.01-0.05 mol.%, wherein X is Br and / or Cl.

3. The photo-thermo-refractive chloride glass according to claim 1, wherein The melting temperature of the chloride photothermal sensitive birefringent glass ranges from 1400 to 1500 DEG C; The laser damage threshold of the chloride photothermal sensitive birefringent glass is >20 J / cm²@1064 nm@8 ns, and the spontaneous crystallization activation energy is >250 KJ / mol.

4. The photo-thermo-refractive chloride glass according to claim 1, wherein The ultraviolet irradiation specifically comprises: exposing the chloride photothermal sensitive birefringent glass to a 325 nm He-Cd laser; in the exposing process, the irradiation power is 5-50 mW, and the irradiation time is 1000-3000 s.

5. The photo-thermo-refractive chloride glass according to claim 1, wherein The T g is 460-480 °C.

6. The photo-thermo-refractive chloride glass according to claim 1, wherein The refractive index of the chloride photothermal sensitive reversible glass with refractive index modulation is between 1.501-1.503, the maximum refractive index modulation Δn is less than 0.0005 n greater than 1000 ppm; The chloride photothermal sensitive glass with refractive index modulation has a light absorption coefficient in the range of 0.005-0.02 cm -1 .

7. A method for producing a chloride photothermal sensitive glass with refractive index modulation according to any one of claims 1 to 6, characterized in that, The preparation of the chloride photothermal sensitive birefringent glass comprises the following steps: (1) weighing each raw material component according to the raw material formula of the chloride photothermal sensitive birefringent glass and mixing to obtain a uniform mixed powder after screening and grinding treatment; (2) under the protection of N2 / O2 mixed gas, the mixed powder is heated and melted into a glass liquid at 1420-1500 DEG C, the liquid level height of the glass liquid in the container is controlled to be 180-210 mm, then the temperature is raised to 1500-1520 DEG C for the first stirring treatment, after the viscosity of the glass liquid reaches 1.9-2.1 Log Pa·S, the temperature is lowered to 1480-1500 DEG C for the second stirring treatment, and a glass liquid to be formed is obtained; (3) pouring the to-be-formed glass liquid into the preheated mold, cooling to the glass transition temperature T g , and then transferring into a heating device for heat preservation at T g for 2-4 h, and then slowly cooling to 15-35 ℃ at a rate of 0.5-1 ℃ / min, polishing the cooled glass to obtain the chloride photo-thermal sensitive glass.

8. The method of claim 7, wherein the method further comprises the step of: In step (2), the first stirring treatment is performed at a stirring frequency of 20-30 Hz for 5-8 hours, and the second stirring treatment is performed at a stirring frequency of 20-30 Hz for 2-3 hours. ​ In step (3), the preheating temperature is 500-600 ℃.

9. Use of the chloride photothermally sensitive glass with refractive index modulation according to any one of claims 1-6 or prepared by the method according to claim 7 or 8 for the production of a volume Bragg grating device.

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