CN108823639A - 1.5 micron wave length hot keys of one kind and laser cooling preparation method - Google Patents

Abstract

The invention discloses a preparation method of a 1.5 micron wavelength hot bond and composite laser crystal, which belongs to the technical field of laser crystal and solid laser. The method includes the following steps: treating the surface of erbium glass and cobalt-doped spinel; after the surface processing of the material, after cleaning and activation treatment, photoresisting is carried out, and the crystals with good photoresisting are left at room temperature for a period of time , put into a heating furnace to heat-treat the obtained Er:Yb:glass-spinel; the heat treatment adopts the process of heating up and cooling down in accordance with the "slow, stepped" process, and also adopts a constant temperature process. The hot bond obtained by the method of the present invention and the composite crystal Er:Yb:glass-co:spinel are used for laser experiments, and a laser output of 1.5 μm can be obtained.

Description

A 1.5 micron wavelength hot bond and compound laser crystal preparation method

technical field

The invention relates to a method for preparing a 1.5-micron wavelength hot bond and a composite laser crystal, which belongs to the technical field of laser crystals and solid lasers.

Background technique

1.5μm belongs to the human eye safety band, and it is just in the atmospheric window. At present, there are two main ways to obtain 1.5μm laser. One is the frequency conversion through the nonlinear optical process, and the other is the direct generation of laser working substances. The former method mainly uses Optical Parametric Oscillation (OPO), Stimulated Raman Scattering (SRS), Self-excited Raman Scattering and other methods to achieve frequency conversion to obtain 1.5 μm laser ^[1-5] . The latter method mainly includes a direct output 1.5μm laser semiconductor laser and a glass crystal laser pumped by LD erbium ions. Using LD to pump Er ³⁺ /Yb ³⁺ co-doped phosphate glass can meet the requirements of high peak power and small volume, and has the characteristics of good beam quality and high conversion efficiency. It has a wide range of application requirements in eye-safe laser ranging/target indication, military and optical fiber communication.

Crystal bonding technology is to directly bond homogeneous or heterogeneous crystal materials into one under certain conditions through crystal preparation (ie surface processing), cleaning, and activation treatment without using any adhesive substances. , molecular forces, and even atomic forces combine together. Crystal bonding technology is of great significance in the research of new optical devices and new solid-state lasers.

Contents of the invention

The technical problem to be solved by the present invention is to provide a hot bond and compound crystal preparation method of Er:Yb:glass and co:spinel, which can realize laser output near 1.5 microns.

Technical scheme of the present invention comprises the following steps:

(1) Material surface processing

The Mohs hardness of erbium-ytterbium co-doped phosphate glass is 4-5. Erbium-ytterbium co-doped phosphate glass Er:Yb:glass, hereinafter referred to as "erbium glass", processes the surface of erbium glass to finally obtain Er:Yb:glass The root mean square roughness of the surface is σ≤0.3nm, and the surface shape is ≤λ/10; the Mohs hardness of cobalt-doped spinel (co:spinel) is 8, and the surface root mean square roughness of the ground and polished co:spinel Degree σ≤0.6nm, surface type≤λ/10;

(2) thermal bonding

Step (1) After the surface of the material is processed, after cleaning and activation treatment, photoresist is carried out. After the crystals of the photoresist are left for a period of time at room temperature, they are placed in a heating furnace to treat the obtained Er:Yb:glass- The spinel is heat treated; the heat treatment is carried out in a "slow, step-by-step" process of heating and cooling, and a constant temperature process is also used;

Set the highest constant temperature T2 as a certain temperature in 290-310°C, preferably 300°C; room temperature-T1 rises by _1-2 °C (preferably ₁ °C) every 5 minutes, and T1 is _a certain temperature in 190-210°C _One temperature, preferably 200°C; then keep the constant temperature at T1 for not less than 10 hours; raise the temperature from T1 to T2, increase the temperature by _1-2 °C (preferably ₁ °C) every 10 minutes, keep the temperature at T2 for not less _than 10 hours ;The cooling process is symmetrical to the heating process, but there is no constant temperature process;

The key elements of heat treatment are heat treatment temperature and heat treatment time. The highest value of the heat treatment temperature is generally selected to be 0.4-0.9 times the melting point of the low melting point material in the two crystals. In addition, in order to prevent the crystal from undergoing phase transition during heating, the temperature also needs to be 80-100°C lower than the temperature at which the crystal undergoes phase transition. The heat treatment time is related to the size of the bonding surface, the rate of formation and arrangement of new chemical bonds. Normally, the high temperature holding time of heat treatment is 8-50 hours, and the actual time can be appropriately shortened or extended according to the composition of the heating material.

Erbium glass is a glassy material without a fixed melting point, and its glass softening temperature is 450°C. The melting point of spinel is 2135°C. The temperature points of the two materials are very different, and the maximum constant temperature of heat treatment should be considered according to the temperature point of erbium glass. It is further preferred to set the maximum constant temperature at 300° C. to heat-treat the Er:Yb:glass-spinel. Heating and cooling are carried out according to the "slow, step-by-step" arrangement. Room temperature -200°C rises by 1°C every 5 minutes, keeps the temperature at 200°C for 10 hours, 200-300°C rises by 1°C every 10 minutes, and keeps the temperature at 300°C for 10 hours. The cooling process is symmetrical to the heating process. Finally, the Er:Yb:glass-spinel thermal bonding of dissimilar materials was successfully realized.

The hot bond obtained by the method of the present invention and the composite crystal Er:Yb:glass-co:spinel are used for laser experiments, and a laser output of 1.5 μm can be obtained.

Description of drawings

Figure 1Er:Yb:glass surface morphology

Figure 2 Surface interference pattern

Figure 3co: surface morphology of spinel

Figure 4 appearance diagram; (a) co:spinel and Er:Yb:glass; (b) hot bond and composite crystal

Figure 5Er:Yb:glass-co:spinel bonding interface HR-TEM large field image

Figure 6 Erbium glass-spinel bonded crystal experimental setup

Detailed ways

The present invention will be further described below in conjunction with the examples, but the present invention is not limited to the following examples.

Example 1

1. Surface processing (precision)

Erbium-ytterbium co-doped phosphate glass (Er:Yb:glass, hereinafter referred to as "erbium glass") has a Mohs hardness of 4 to 5. We use diamond abrasives with a particle size of 3 μm to grind the surface of the erbium glass. Use a laser plane interferometer to view the surface until the image of the processed surface in the interferometer becomes a circular spot, and then proceed to the next processing step - rough polishing. The rough polishing of erbium glass is carried out with a cerium oxide polishing solution with a particle size of 500 mesh (25 μm). After a period of time, use a laser plane interferometer to view the processed surface until wide parallel stripes appear on the image of the processed surface in the interferometer. Then carry out the final fine polishing. The hardness of erbium glass is low, and the surface topography changes rapidly when polished. Fine polishing Use 1.5μm cerium oxide polishing solution to fine polish the erbium glass. During the fine polishing, the surface morphology is observed at regular intervals using a laser plane interferometer and a Zygo profiler to ensure that its flatness and roughness meet the requirements of optical glue. Finally, the surface root mean square roughness σ of Er:Yb:glass is 0.3nm, and the surface type is <λ/10. The detection image of the Zygo profiler is shown in Figure 1, and the surface shape is shown in Figure 2.

The Mohs hardness of cobalt-doped spinel (co:spinel) is 8, and its grinding and polishing process is similar to that of erbium glass. Use alumina micropowder grinding liquid with a particle size of 3 μm to grind the crystal surface, use alumina fine powder grinding liquid with a particle size of 0.5 μm to roughly polish the crystal surface, and finally use alumina fine powder grinding liquid with a particle size of 0.05 μm to polish the crystal surface Finely polished. The surface root mean square roughness σ of co:spinel is 0.6nm, and the surface type is <λ/10. The detection image of the Zygo profiler is shown in Figure 3, and the surface shape is shown in Figure 3.

2. Thermal bonding (process)

After the surface of the material is processed, after cleaning and activation treatment, the photoresist is carried out. After the photoresisted crystal is left at room temperature for a period of time, it is put into a heating furnace for heat treatment. The key elements of heat treatment are heat treatment temperature and heat treatment time.

Set the maximum constant temperature to 300°C, and heat-treat the Er:Yb:glass-spinel. Heating and cooling are carried out according to the "slow, step-by-step" arrangement. Room temperature -200°C rises by 1°C every 5 minutes, keeps the temperature at 200°C for 10 hours, 200-300°C rises by 1°C every 10 minutes, and keeps the temperature at 300°C for 10 hours. The cooling process is symmetrical to the heating process. Finally, the Er:Yb:glass-spinel thermal bonding of dissimilar materials was successfully realized.

The size of the co:spinel used in the bonding experiment is 22mm in diameter and 3mm in thickness, and the size of Er:Yb:glass is 25mm in diameter and 5mm in thickness.

In order to analyze the bonding effect of Er:Yb:glass-co:spinel, we used a high-resolution transmission electron microscope (HR-TEM) to image the bonding surface of the two with a large field of view, as shown in Figure 5. It can be seen from Figure 5 that the bonding surface is smooth without obvious defects.

At the same time, the laser experiment was carried out with the hot bond and the compound crystal Er:Yb:glass-co:spinel, and a laser output of 1.5μm with a single pulse energy of 120μJ, a pulse width of 5ns, a repetition frequency of 10Hz, and M ² =1.3 was obtained.

Claims (3)

1. A 1.5 micron wavelength hot bond and compound laser crystal preparation method, is characterized in that, comprises the following steps: (1) Material surface processing The Mohs hardness of erbium-ytterbium co-doped phosphate glass is 4-5. Erbium-ytterbium co-doped phosphate glass Er:Yb:glass, hereinafter referred to as "erbium glass", processes the surface of erbium glass to finally obtain Er:Yb:glass The root mean square roughness of the surface is σ≤0.3nm, and the surface shape is ≤λ/10; the Mohs hardness of cobalt-doped spinel (co:spinel) is 8, and the surface root mean square roughness of the ground and polished co:spinel Degree σ≤0.6nm, surface type≤λ/10; (2) thermal bonding Step (1) After the surface of the material is processed, after cleaning and activation treatment, photoresist is carried out. After the crystals of the photoresist are left for a period of time at room temperature, they are placed in a heating furnace to treat the obtained Er:Yb:glass- The spinel is heat treated; the heat treatment is carried out in a "slow, step-by-step" process of heating and cooling, and a constant temperature process is also used; Set the highest constant temperature T ₂ to a certain temperature of 290-310°C; room temperature-T ₁ rises by 1-2°C every 5 minutes, and T ₁ is a certain temperature of 190-210°C _; Less than 10 hours; temperature rise from T ₁ to T ₂ , 1-2°C (preferably 1°C) every 10 minutes, constant temperature at T ₂ for not less than 10 hours, the temperature drop process is symmetrical to the temperature rise process. 2. according to claim 1, a kind of 1.5 micron wavelength heat bond and composite laser crystal preparation method is characterized in that, room temperature-T1 rises ₁ ℃ every 5 minutes. 3. according to claim 1, a kind of 1.5 micron wavelength hot bond and composite laser crystal preparation method is characterized in that, T1 is 200 DEG C _; the temperature rises from T1 to T2, and rises by ₁ DEG C every ₁₀ minutes; T ₂ is 300°C.