A phosphate laser glass planar waveguide bonding liquid and a preparation method of a corresponding waveguide

Abstract

This invention proposes a bonding solution for phosphate laser glass planar waveguides and a method for preparing the corresponding waveguides. The bonding solution is composed of an acid component, a salt component, and a solvent component in a specific ratio. The acid component consists of phosphoric acid and pyrophosphate in a specific ratio; the salt component consists of sodium tripolyphosphate and sodium hexametaphosphate in a specific ratio; and the solvent consists of water and ethanol in a specific ratio. The bonding solution and the method for preparing the corresponding waveguides provided by this invention can compensate for the differences in surface shape between the core layer and the cladding, as well as between the cladding and the outer cladding glass. It enables the bonding of doped rare-earth phosphate laser glass in the core layer and undoped phosphate glass in the cladding, as well as the bonding of undoped phosphate glass in the cladding and optical glass in the outer cladding, at low temperatures, significantly increasing the effective bonding area and bonding interface strength while reducing interface loss.

Description

Technical Field

[0001] This invention relates to the field of laser glass fabrication, and more particularly to a phosphate laser glass planar waveguide bonding solution and a method for preparing the corresponding waveguide. Background Technology

[0002] All-solid-state lasers are widely used in medical, military, and scientific research fields due to their compact structure, stable laser output performance, good beam quality, and high efficiency. In the early stages of all-solid-state laser development, the gain medium typically employed cylindrical rods and bulk structures. To improve electro-optical efficiency, research institutions, supported by the Durable Electronics and Lasers Initiative (RELI) project, have conducted research on various lasers, including planar waveguide lasers. Researchers have continuously explored the morphology of the gain medium, evolving from slabs to thin sheets, optical fibers, and planar waveguide structures. However, with the development of application demands, higher power requirements have emerged for lasers. For laser gain medium materials with poor heat dissipation and a large coefficient of thermal expansion, high-power pumping generates a large amount of waste heat, causing severe thermal effects such as thermal lensing, thermally induced birefringence, and thermal stress, thus limiting the output of high-power lasers. Therefore, planar waveguide structures with excellent heat dissipation have attracted considerable attention. Planar waveguide structures possess two large heat dissipation surfaces, and if the upper and lower layers are made of materials with high thermal conductivity, the heat dissipation efficiency of the gain medium and the entire system can be further improved. They also facilitate power scaling; the planar waveguide structure allows heat flow in one dimension, facilitating the manipulation of thermal lensing effects. Furthermore, by increasing the width and length of the waveguide layers, power scaling can be well designed and implemented. Compared to fiber structures, planar waveguides can limit nonlinear effects to a certain extent; the large mode area designed by the waveguide thickness and planar beamwidth can suppress nonlinear effects. They also have high compatibility with strip semiconductor lasers; the waveguide structure can effectively confine non-diffraction-limited beams. Only a simple optical focusing system is needed, and even without additional optical shaping or any optical components, to obtain a simple and compact laser device. They also have potential for photonic integration. The integration of planar waveguides with on-chip integration and other processes enables the integration of various devices such as Q-switches, gratings, and filters. This is of great significance in the research of novel optical devices and novel solid-state lasers.

[0003] Methods for fabricating planar waveguides can be divided into two categories: processes that change the refractive index of the planar waveguide material and composite material fabrication processes that connect materials with different refractive indices. There are several methods to change the refractive index of planar waveguide materials, including proton or ion implantation, ion exchange and laser writing. ([1] Wang Liangling. Preparation and characteristics of planar and strip optical waveguides by ion implantation and ion exchange [D]. Shandong University, 2008; [2] Tervonen A, Honkanen SK, West BR. Ion-exchanged glass waveguide technology: a review [J]. Optical Engineering, 2011, 50(7): 071107; [3] Chen Haiyan, Liu Yongzhi, Dai Jizhi, et al. Er3+-Yb3+ co-doped phosphate glass planar waveguide [J]. Applied Optics, 2003, 24(5): 39-41; [4] Zhao Shilong, Chen Baoyu, Hu Junjiang, et al. Effect of post-processing on ion-exchanged phosphate glass planar optical waveguide [J]. Applied Optics, 2005, 26(6): (32-34.) The resulting waveguide is relatively thin, with a small refractive index difference, i.e., a small numerical aperture, making it unsuitable for high-divergence or multimode lasers with high-power laser output. The composite material preparation process that connects materials with different refractive indices includes techniques for preparing thin film composite structures of different materials, including epitaxial growth (molecular beam epitaxy, liquid phase epitaxy, and pulsed laser deposition, PLD), sputtering and deposition, and bonding techniques ([5] Li L, Chen Z, Zang Y, et al. Epitaxial growth of Si / SiC heterostructures with different preferred orientations on 6H-SiC (0001) by LPCVD [J]. CrystEngComm, 2016, 18(30): 5681-5685; [6] Liu Aiguo. Low temperature plasma surface strengthening technology [M]. Low temperature plasma surface strengthening technology, 2015; [7] Wallis G, Pomerantz DI. Field Assisted Glass‐ Metal Sealing [J]. Journal of AppliedPhysics, 1969, 40(10): (3946-3949.) This technique can produce relatively thick planar waveguides with large refractive index differences, i.e., planar waveguide structures with large numerical apertures. Bonding technology has many advantages over other techniques.First, it is easier to control the bonding interface morphology, which can combine materials of different qualities together, and the interface performance is excellent. It does not require a lattice matching layer like epitaxial growth. Second, it does not require expensive and complex equipment, making it more suitable for large-scale, low-cost production with stable and reliable processes. Third, in the fabrication of planar waveguides, it can easily fabricate configurations such as double-clad planar waveguides.

[0004] Currently, existing planar waveguide fabrication processes are mainly divided into refractive index modification processes and composite material bonding processes. First, refractive index modification processes such as ion implantation, ion exchange, and laser writing result in thin waveguide layers, small refractive index differences, and low numerical apertures, making it difficult to meet the requirements of high-power laser output. Second, composite material processes such as epitaxial growth, sputtering deposition, and traditional thermal bonding can fabricate thick-layer waveguides with large numerical apertures, but traditional thermal bonding has high temperatures, which can easily cause glass thermal distortion and rare-earth ion fluorescence quenching. At the same time, there are problems such as difficulty in matching the core-cladding-outer cladding surface topography, small effective bonding area, low interface strength, and high transmission loss, resulting in low process yield, high cost, and difficulty in large-scale application. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to overcome the defects of the existing technology. The present invention proposes a phosphate laser glass planar waveguide bonding liquid and a corresponding waveguide preparation method.

[0006] To solve the aforementioned technical problems, the technical solution adopted by the present invention is as follows: A phosphate laser glass planar waveguide bonding solution, wherein the bonding solution comprises an acid component, a salt component, and a solvent component in a molar ratio of 2:1:100 to 5:1:50, and the composition and molar percentage of each component are as follows: Acid fraction: Phosphoric acid (H3PO4) 10~60 mol%, pyrophosphate (H4P2O7) 90~40 mol%; Salt portion: Sodium tripolyphosphate (Na5P3O) 10 20-60 mol% sodium hexametaphosphate ((NaPO3)6) 80-40 mol%; solvent portion: water (H2O) 40-90 mol%, ethanol (CH3CH2OH) 60-10 mol%.

[0007] Preferably, the bonding solution comprises an acid portion, a salt portion, and a solvent portion in a molar ratio of 3:1:80 to 4:1:60, and the composition and molar percentage of each portion are as follows: Acid fraction: H3PO4 30~50 mol%, H4P2O7 70~50 mol%; Salt portion: Na5P3O 10 30~50mol%, (NaPO3) 670~50mol%; Solvent portion: H2O 50~70 mol%, CH3CH2OH 50~30 mol%.

[0008] Preferably, the bonding solution is prepared by: preparing an acid mixture, a salt mixture, and a solvent mixture according to the specified ratio; adding the acid and salt mixtures to the solvent mixture; and stirring at room temperature for 30-60 minutes to obtain a uniform and transparent bonding solution.

[0009] A method for fabricating a phosphate laser glass planar waveguide using the above-mentioned bonding solution includes the following steps: S1: Perform ultrasonic cleaning on the ground and polished core glass, cladding glass and outer cladding glass; S2: The two sides of the core glass are bonded to one side of each of the two cladding glasses using bonding fluid to form a three-layer structure; then the other side of each cladding glass is bonded to one side of each of the two outer cladding glasses using bonding fluid to form a double-clad five-layer waveguide. S3: Place the double-clad five-layer waveguide on a horizontal platform, apply a weight on top and leave it stationary; S4: Annealing the double-clad five-layer waveguide structure yields a bonded phosphate laser glass planar waveguide. Preferably, the core glass is rare-earth-doped phosphate laser glass, the cladding glass is undoped phosphate laser glass, and the outer cladding glass is optical glass.

[0010] Preferably, the rare-earth-doped phosphate laser glass includes neodymium-doped phosphate laser glass, erbium-doped phosphate laser glass, ytterbium-doped phosphate laser glass, and ytterbium-erbium co-doped phosphate laser glass.

[0011] Preferably, in step S1, the polished core glass, cladding glass, and outer cladding glass are placed in a glass beaker, and high-purity ethanol is added to submerge them. Then, the beaker is placed in an ultrasonic cleaner and ultrasonically cleaned at 25°C for 10 minutes. The high-purity ethanol is then poured out. The ultrasonic process is repeated twice, for a total of three ultrasonic cleanings with high-purity ethanol.

[0012] Preferably, in step S2, the beaker is removed from the ultrasonic cleaner, and in a Class 1000 cleanroom environment, the core glass, cladding glass, and outer cladding glass are removed and wiped clean with a lint-free cloth. Bonding liquid is dripped onto one large surface of the core glass and bonded to the large surface of the cladding glass. Bonding liquid is then dripped onto the other large surface of the core glass and another cladding glass is bonded to it, thus forming a three-layer structure of core glass and cladding glass bonded to the two large surfaces. Then, another layer of outer cladding glass is bonded to the other large surface of each cladding glass using bonding liquid, forming a double-clad five-layer waveguide structure with one core glass, two cladding glasses, and two outer cladding glasses.

[0013] Preferably, in step S3, the five-layer waveguide is placed on a water platform in the cleanroom, and a weight is placed on top, and left to stand for 48 hours; wherein the mass ratio of the weight to the total mass of the five-layer waveguide is 1:1 to 5:1.

[0014] Preferably, in step S4, the five-layer waveguide is placed in a vacuum annealing furnace, heated from room temperature to 300°C over 48 hours, held at 300°C for 10 hours, and then cooled to room temperature over 48 hours to obtain a phosphate laser glass planar waveguide bonded together as one piece.

[0015] Compared with the prior art, the beneficial effects of the present invention are: This invention proposes a bonding solution and bonding method for the fabrication of phosphate laser glass planar waveguides, enabling bonding of phosphate laser glass planar waveguides at relatively low temperatures; The requirements for the surface matching of the core layer, cladding layer and outer cladding layer glass in this invention are much lower than those of bonding methods such as photoresist and anodic bonding. This reduces the difficulty of surface processing of the core layer, cladding layer and outer cladding layer glass, increases the operability of the bonding process and improves the yield, and reduces the process cost. This invention compensates for the surface shape differences between the core layer and the cladding, as well as between the cladding and the outer cladding glass, and significantly increases the effective bonding area and bonding interface strength while reducing interface loss. Attached Figure Description

[0016] The disclosure of this invention is illustrated with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of this invention. In the drawings, the same reference numerals are used to refer to the same parts. Wherein: Figure 1 This is a schematic diagram of the three-layer phosphate laser glass waveguide of the present invention; Figure 2 This is a schematic diagram of the phosphate laser glass double-clad five-layer waveguide structure of the present invention. Detailed Implementation

[0017] It is readily understood that, based on the technical solution of this invention, those skilled in the art can propose various interchangeable structural methods and implementations without altering the essential spirit of the invention. Therefore, the following detailed embodiments and accompanying drawings are merely illustrative examples of the technical solution of this invention and should not be considered as the entirety of the invention or as limitations or restrictions on the technical solution of this invention.

[0018] Specific embodiments of the present invention are described below with reference to the accompanying drawings.

[0019] This embodiment proposes a phosphate laser glass planar waveguide bonding solution and a method for preparing the corresponding waveguide.

[0020] Example 1 The core layer phosphate laser glass is neodymium-doped phosphate laser glass. The molar ratio of the acid, salt, and solvent components of the bonding solution is 5:1:50. The composition and molar percentage of each component are as follows: 1) Acidic part: Component mol% H3PO4 10 H4P2O7 90 2) Salt portion: component mol% Na5P3O 10 20 (NaPO3)6 80 3) Solvent component: Component mol% H2O 40 CH3CH2OH 60 The steps for fabricating a planar waveguide are as follows: Step 1: Place the ground and polished core glass, clad laser glass, and outer cladding glass into a glass beaker, add high-purity ethanol to submerge them, and then place the beaker in an ultrasonic cleaner and ultrasonically clean it at 25°C for 10 minutes. Then pour out the high-purity ethanol, add more high-purity ethanol to submerge them, and ultrasonically clean them again at 25°C for 10 minutes. Repeat the above operation once more, that is, use high-purity ethanol for ultrasonic cleaning three times.

[0021] Step 2: Remove the beaker from the ultrasonic cleaner. In a Class 1000 cleanroom environment, remove the core laser glass, cladding glass, and outer cladding glass. Wipe them clean with a lint-free cloth. Apply the bonding liquid described above to one large surface of the core laser glass and adhere it to the large surface of the cladding glass. Then apply the same bonding liquid to the other large surface of the core laser glass and adhere the cladding glass, thus forming a three-layer structure consisting of the core laser glass and the cladding glass adhered to the two large surfaces (e.g., ...). Figure 1 (As shown). Finally, another outer cladding glass layer is bonded to the other side of each cladding glass using the bonding liquid described above, thus forming a double-clad five-layer waveguide structure with one core laser glass and two cladding layers and two outer cladding layers (as shown). Figure 2 (As shown).

[0022] Step 3: Place the five-layer waveguide on the water platform in the cleanroom, place a 100-gram weight on top, and let it stand for 48 hours.

[0023] Step 4: The five-layer waveguide is placed in a vacuum annealing furnace, and then heated from room temperature to 300°C over 48 hours. It is then held at 300°C for 10 hours and then cooled to room temperature over 48 hours to obtain a waveguide structure bonded together as one unit.

[0024] Results and performance: effective bonding area 95%, interfacial shear strength 12MPa, transmission loss 0.08dB / cm.

[0025] Example 2 The core layer phosphate laser glass is erbium-doped phosphate laser glass. The molar ratio of the acid, salt, and solvent components of the bonding solution is 4:1:60. The composition and molar percentage of each component are as follows: 1) Acidic part: Component mol% H3PO4 30 H4P2O7 70 2) Salt portion: component mol% Na5P3O 10 30 (NaPO3)6 70 3) Solvent component: Component mol% H2O 50 CH3CH2OH 50 The steps for fabricating a planar waveguide are as follows: Step 1: Place the ground and polished core glass, clad laser glass, and outer cladding glass into a glass beaker, add high-purity ethanol to submerge them, and then place the beaker in an ultrasonic cleaner and ultrasonically clean it at 25°C for 10 minutes. Then pour out the high-purity ethanol, add more high-purity ethanol to submerge them, and ultrasonically clean them again at 25°C for 10 minutes. Repeat the above operation once more, that is, use high-purity ethanol for ultrasonic cleaning three times.

[0026] Step 2: Remove the beaker from the ultrasonic cleaner. In a Class 1000 cleanroom environment, remove the core laser glass, cladding glass, and outer cladding glass. Wipe them clean with a lint-free cloth. Apply the bonding liquid described above to one large surface of the core laser glass and bond it to the large surface of the cladding glass. Apply the same bonding liquid to the other large surface of the core laser glass and then bond the cladding glass, thus forming a three-layer structure consisting of the core laser glass and the cladding glass bonded to the two large surfaces. Finally, bond another layer of outer cladding glass to the other large surface of each cladding glass using the same bonding liquid, thus forming a double-clad five-layer waveguide structure with one core laser glass, two cladding layers, and two outer cladding layers.

[0027] Step 3: Place the five-layer waveguide on the water platform in the cleanroom, place a 100-gram weight on top, and let it stand for 48 hours.

[0028] Step 4: The five-layer waveguide structure is placed in a vacuum annealing furnace, then heated from room temperature to 300°C over 48 hours, held at 300°C for 10 hours, and then cooled to room temperature over 48 hours to obtain a bonded waveguide structure.

[0029] Results and performance: effective bonding area 96%, interfacial shear strength 13MPa, transport loss 0.07dB / cm.

[0030] Example 3 The core layer phosphate laser glass is ytterbium-doped phosphate laser glass. The molar ratio of the acid, salt, and solvent components of the bonding solution is 3:1:80. The composition and molar percentage of each component are as follows: 1) Acidic part: Component mol% H3PO4 50 H4P2O7 50 2) Salt portion: component mol% Na5P3O 10 50 (NaPO3)6 50 3) Solvent component: Component mol% H2O 70 CH3CH2OH 30 The steps for fabricating a planar waveguide are as follows: Step 1: Place the ground and polished core glass, clad laser glass, and outer cladding glass into a glass beaker, add high-purity ethanol to submerge them, and then place the beaker in an ultrasonic cleaner and ultrasonically clean it at 25°C for 10 minutes. Then pour out the high-purity ethanol, add more high-purity ethanol to submerge them, and ultrasonically clean them again at 25°C for 10 minutes. Repeat the above operation once more, that is, use high-purity ethanol for ultrasonic cleaning three times.

[0031] Step 2: Remove the beaker from the ultrasonic cleaner. In a Class 1000 cleanroom environment, remove the core laser glass, cladding glass, and outer cladding glass. Wipe them clean with a lint-free cloth. Apply the bonding liquid described above to one large surface of the core laser glass and bond it to the large surface of the cladding glass. Apply the same bonding liquid to the other large surface of the core laser glass and then bond the cladding glass, thus forming a three-layer structure consisting of the core laser glass and the cladding glass bonded to the two large surfaces. Finally, bond another layer of outer cladding glass to the other large surface of each cladding glass using the same bonding liquid, thus forming a double-clad five-layer waveguide structure with one core laser glass, two cladding layers, and two outer cladding layers.

[0032] Step 3: Place the five-layer waveguide on the water platform in the cleanroom, place a 100-gram weight on top, and let it stand for 48 hours.

[0033] Step 4: The five-layer waveguide structure is placed in a vacuum annealing furnace, then heated from room temperature to 300°C over 48 hours, held at 300°C for 10 hours, and then cooled to room temperature over 48 hours to obtain a bonded waveguide structure.

[0034] Results and performance: effective bonding area 97%, interfacial shear strength 14 MPa, transmission loss 0.06 dB / cm.

[0035] Example 4 The core layer phosphate laser glass is ytterbium-erbium co-doped phosphate laser glass. The molar ratio of the acid, salt, and solvent components of the bonding solution is 2:1:100. The composition and molar percentage of each component are as follows: 1) Acidic part: Component mol% H3PO4 60 H4P2O7 40 2) Salt portion: component mol% Na5P3O 10 60 (NaPO3)6 40 3) Solvent component: Component mol% H2O 90 CH3CH2OH 10 The steps for fabricating a planar waveguide are as follows: Step 1: Place the ground and polished core glass, clad laser glass, and outer cladding glass into a glass beaker, add high-purity ethanol to submerge them, and then place the beaker in an ultrasonic cleaner and ultrasonically clean it at 25°C for 10 minutes. Then pour out the high-purity ethanol, add more high-purity ethanol to submerge them, and ultrasonically clean them again at 25°C for 10 minutes. Repeat the above operation once more, that is, use high-purity ethanol for ultrasonic cleaning three times.

[0036] Step 2: Remove the beaker from the ultrasonic cleaner. In a Class 1000 cleanroom environment, remove the core laser glass, cladding glass, and outer cladding glass. Wipe them clean with a lint-free cloth. Apply the bonding liquid described above to one large surface of the core laser glass and bond it to the large surface of the cladding glass. Apply the same bonding liquid to the other large surface of the core laser glass and then bond the cladding glass, thus forming a three-layer structure consisting of the core laser glass and the cladding glass bonded to the two large surfaces. Finally, bond another layer of outer cladding glass to the other large surface of each cladding glass using the same bonding liquid, thus forming a double-clad five-layer waveguide structure with one core laser glass, two cladding layers, and two outer cladding layers.

[0037] Step 3: Place the five-layer waveguide on the water platform in the cleanroom, place a 100-gram weight on top, and let it stand for 48 hours.

[0038] Step 4: The five-layer waveguide structure is placed in a vacuum annealing furnace, then heated from room temperature to 300°C over 48 hours, held at 300°C for 10 hours, and then cooled to room temperature over 48 hours to obtain a bonded waveguide structure.

[0039] Results and performance: effective bonding area 94%, interfacial shear strength 11 MPa, transmission loss 0.09 dB / cm.

[0040] Summarize: This invention achieves chemical bonding at the glass interface through a specific phosphate-based bonding solution and a 300°C low-temperature annealing process, eliminating the need for high-temperature melting. This effectively avoids glass thermal distortion, internal stress, and rare-earth ion fluorescence quenching caused by traditional high-temperature bonding, significantly improving the optical consistency and stability of waveguides.

[0041] The bonding fluid has moderate fluidity and filling properties, which can adaptively fill the small surface errors of the core layer, cladding, and outer cladding glass, reduce the stringent requirements for ultra-precision polishing, simplify the processing flow, and improve the process tolerance and product yield.

[0042] The bonding fluid can form a uniform and continuous transition layer at the interface, enabling the effective bonding area to reach more than 94%, significantly improving the interfacial shear strength, avoiding failure problems such as delamination, cracking, and debonding, and meeting the long-term reliable operation requirements of high-power lasers.

[0043] The bonding interface is bubble-free, impurity-free, and has a high refractive index matching degree. The optical transmission loss can be reduced to below 0.1dB / cm, which greatly improves the waveguide gain efficiency and output beam quality, making it more suitable for high-power, high-beam-quality laser systems.

[0044] It eliminates the need for expensive equipment such as vacuum bonding, anodic bonding, and high temperature and high pressure, and can be completed in a conventional clean environment and vacuum annealing furnace. The process is short, has good repeatability, and low preparation cost, which can meet the needs of industrial-scale mass production.

[0045] It is compatible with various rare earth phosphate laser glasses such as neodymium-doped, erbium-doped, ytterbium-doped, and ytterbium-erbium co-doped lasers, and is suitable for all-solid-state planar waveguide lasers of different bands and power levels, with strong versatility.

[0046] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit it. Although the present patent has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the protection scope of the present invention.

Claims

1. A phosphate laser glass planar waveguide bonding solution, characterized in that, The bonding solution consists of an acid component, a salt component, and a solvent component in a molar ratio of 2:1:100 to 5:1:

50. The composition and molar percentage of each component are as follows: Acid fraction: Phosphoric acid (H3PO4) 10~60 mol%, pyrophosphate (H4P2O7) 90~40 mol%; Salt portion: Sodium tripolyphosphate (Na5P3O) 10 20-60 mol% sodium hexametaphosphate ((NaPO3)6) 80-40 mol%; solvent portion: water (H2O) 40-90 mol%, ethanol (CH3CH2OH) 60-10 mol%.

2. The phosphate laser glass planar waveguide bonding solution according to claim 1, characterized in that, The bonding solution consists of an acid component, a salt component, and a solvent component in a molar ratio of 3:1:80 to 4:1:

60. The composition and molar percentage of each component are as follows: Acid fraction: H3PO4 30~50 mol%, H4P2O7 70~50 mol%; Salt portion: Na5P3O 10 30~50mol%, (NaPO3) 670~50mol%; Solvent portion: H2O 50~70 mol%, CH3CH2OH 50~30 mol%.

3. The phosphate laser glass planar waveguide bonding solution according to claim 1, characterized in that, The bonding solution is prepared by: preparing an acid mixture, a salt mixture, and a solvent mixture according to the specified ratio; adding the acid and salt mixtures to the solvent mixture; and stirring at room temperature for 30-60 minutes to obtain a uniform and transparent bonding solution.

4. A method for fabricating a phosphate laser glass planar waveguide using the bonding solution as described in claim 1, characterized in that, Includes the following steps: S1: Perform ultrasonic cleaning on the ground and polished core glass, cladding glass and outer cladding glass; S2: The two sides of the core glass are bonded to one side of each of the two cladding glasses using bonding fluid to form a three-layer structure; then the other side of each cladding glass is bonded to one side of each of the two outer cladding glasses using bonding fluid to form a double-clad five-layer waveguide. S3: Place the double-clad five-layer waveguide on a horizontal platform, apply a weight on top and leave it stationary; S4: Anneal the double-clad five-layer waveguide to obtain a phosphate laser glass planar waveguide bonded together as one piece.

5. The method for fabricating a phosphate laser glass planar waveguide according to claim 4, characterized in that, The core glass is rare-earth-doped phosphate laser glass, the cladding glass is undoped phosphate laser glass, and the outer cladding glass is optical glass.

6. The method for fabricating a phosphate laser glass planar waveguide according to claim 5, characterized in that, The rare-earth-doped phosphate laser glass includes neodymium-doped phosphate laser glass, erbium-doped phosphate laser glass, ytterbium-doped phosphate laser glass, and ytterbium-erbium co-doped phosphate laser glass.

7. The method for fabricating a phosphate laser glass planar waveguide according to claim 4, characterized in that, In step S1, the polished core glass, cladding glass, and outer cladding glass are placed in a glass beaker, and high-purity ethanol is added to submerge them. The beaker is then placed in an ultrasonic cleaner and ultrasonically cleaned at 25°C for 10 minutes. The high-purity ethanol is then poured out. The ultrasonic process is repeated twice, for a total of three ultrasonic cleanings with high-purity ethanol.

8. The method for fabricating a phosphate laser glass planar waveguide according to claim 4, characterized in that, In step S2, the beaker is removed from the ultrasonic cleaner. In a Class 1000 cleanroom environment, the core glass, cladding glass, and outer cladding glass are removed and wiped clean with a lint-free cloth. Bonding liquid is dripped onto one large surface of the core glass and bonded to the large surface of the cladding glass. Bonding liquid is then dripped onto the other large surface of the core glass and another cladding glass is bonded to it, thus forming a three-layer structure of core glass and cladding glass bonded to the two large surfaces. Then, another layer of outer cladding glass is bonded to the other large surface of each cladding glass using bonding liquid, forming a double-clad five-layer waveguide structure with one core glass, two cladding glasses, and two outer cladding glasses.

9. The method for fabricating a phosphate laser glass planar waveguide according to claim 4, characterized in that, In step S3, the five-layer waveguide is placed on a water platform in the cleanroom, and a weight is placed on top of it. The waveguide is left to stand for 48 hours. The mass ratio of the weight to the total mass of the five-layer waveguide is 1:1 to 5:

1.

10. The method for fabricating a phosphate laser glass planar waveguide according to claim 4, characterized in that, In step S4, the five-layer waveguide is placed in a vacuum annealing furnace and heated from room temperature to 300°C over 48 hours. It is then held at 300°C for 10 hours and cooled to room temperature over 48 hours to obtain a phosphate laser glass planar waveguide bonded together as one piece.

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