A low-threshold yellow solid-state laser based on energy transfer

Abstract

The present invention discloses a low-threshold yellow light solid-state laser based on energy transfer, comprising a pump source, a focusing coupling system, and a resonant cavity; the resonant cavity comprises an input mirror and an output mirror arranged relatively in the resonant cavity, and a laser gain medium arranged between the input mirror and the output mirror, wherein the laser gain medium is Ce, Dy: LuGdAG transparent ceramic, and its chemical formula is (Gd 1‑x‑y‑z Lu x Dy y Ce z )3Al5O 12 , wherein 0.30≤x≤0.5, 0.03≤y≤0.3, 0.005≤z≤0.02, Ce, Dy: LuGdAG transparent ceramics are prepared by co-precipitation method. The present invention adopts Ce, Dy: LuGdAG transparent ceramics as laser gain medium, through Ce 3+ Co-doping, Dy 3+ The absorbed wavelength photon energy can be transferred to Ce 3+ , thereby increasing Ce 3+ 5d‑4f transition, Gd 3+ The doping of Gd improves the energy level loss between ions. 3+ The incorporation of ions with large radius makes the multi-ion-doped lattice more stable, ultimately achieving efficient yellow laser output.

Description

Technical Field

[0001] The invention belongs to the field of solid-state lasers, and in particular relates to a low-threshold yellow light solid-state laser based on energy transfer. Background Art

[0002] Yellow lasers (550-620 nm) have important applications in spectral analysis, lidar, medical aesthetics, and biochemical monitoring. Several methods are currently available for generating yellow light: nonlinear crystal frequency doubling (patent CN105071217), dual-wavelength sum frequency generation, fiber lasers incorporating nonlinear optical techniques, and Raman lasers. However, these methods primarily utilize nonlinear frequency conversion of infrared lasers. This results in, on the one hand, poor stability of the yellow light output power and beam quality due to competition between fundamental frequency modes during the nonlinear conversion process; on the other hand, the complexity of the system directly leads to a larger laser size, which seriously impacts laser reliability. Materials capable of directly emitting yellow light have received significant attention in recent years. Current research, both domestically and internationally, focuses on organic solid fuels, organic-inorganic hybrid crystals, rare-earth ion-doped laser crystals, and color-center LiF crystals. While these approaches facilitate system miniaturization, the physicochemical stability of the laser dye itself and the complexity of the laser cooling system limit the development of all-solid-state dye lasers.

[0003] Semiconductor laser pumping of dysprosium-doped laser medium is the most direct way to generate laser. According to the special energy level structure of dysprosium-doped laser medium, semiconductor laser pumping is used to 4 F 9 / 2 → 6 H 13 / 2 The energy level transition can directly generate yellow light laser. This structure does not require nonlinear frequency conversion and has the advantages of small size, good stability and low noise.

[0004] The literature (Ju Qiaojun, Shen Hua, Yao Wenming, Chen Jiansheng, Tan Huiming, Liu Wenpeng, Luo Jianqiao, Zhang Qingli, Gao Jing. Semiconductor laser pumped Dy:YAG yellow laser [J]. Chinese Laser, 2017, 44(04): 23-28.) reported the use of Dy:YAG to achieve semiconductor direct pumping of yellow laser output, but the obtained laser output power was low and could not meet the actual application requirements. Summary of the Invention

[0005] The purpose of the present invention is to provide a low-threshold yellow light solid laser based on energy transfer, which can achieve high-efficiency yellow light laser output under the excitation of a pump source.

[0006] To achieve the above-mentioned object, the technical solution adopted by the present invention is as follows: a low-threshold yellow solid-state laser based on energy transfer, comprising a pump source, a focusing coupling system, and a resonant cavity; the resonant cavity comprises an input mirror and an output mirror arranged opposite to each other in the resonant cavity, and a laser gain medium arranged between the input mirror and the output mirror, wherein the laser gain medium is a Ce, Dy: LuGdAG transparent ceramic, whose chemical formula is (Gd 1-x-y-z Lu x Dy y Ce z )3Al5O 12 , wherein 0.30≤x≤0.5, 0.03≤y≤0.3, 0.005≤z≤0.02, and the Ce, Dy: LuGdAG transparent ceramic is prepared by a co-precipitation method.

[0007] The present invention adopts Ce, Dy: LuGdAG transparent ceramic as laser gain medium, wherein Ce 3+ Co-doping, Dy 3 + Ions can transfer the absorbed wavelength photon energy to Ce 3+ ions, thereby increasing Ce 3+ 5d-4f transition of ions, Gd 3 + Ion doping improves the energy level loss between ions. In addition, Gd 3+ As ions with large radius, doping makes the multi-ion doped lattice more stable, ultimately achieving efficient yellow light laser output.

[0008] Preferably, the specific steps of preparing Ce, Dy: LuGdAG transparent ceramics by co-precipitation method include:

[0009] (1) According to (Gd 1-x-y-z Lu x Dy y Ce z )3Al5O 12 According to the stoichiometric ratio of each element, Dy(NO3)3, Gd(NO3)3, Eu(NO3)3 and Lu(NO3)3 solutions were measured respectively, mixed and stirred evenly, and dispersant (NH4)2SO4 solution was added dropwise;

[0010] (2) adding the mixed solution dropwise to a precipitant solution with continuous stirring, wherein the precipitant is NH3·H2O and / or NH4HCO3, and adjusting the pH value of the system to between 7.2 and 7.8; aging and filtering the obtained precursor precipitate; drying the precursor precipitate, grinding and sieving, and calcining to obtain a ceramic powder;

[0011] (3) The ceramic powder is pressed into shape and cooled to obtain a green body, and the green body is pre-sintered under vacuum conditions. The vacuum-sintered sample is then subjected to hot isostatic pressing and annealed to obtain a transparent ceramic.

[0012] Preferably, the calcination temperature in step (2) is 1000-1200° C., and the holding time is 3-8 hours.

[0013] Preferably, the vacuum sintering temperature in step (3) is 1500-1750° C., and the holding time is 3-15 hours.

[0014] Preferably, the hot isostatic pressing pressure in step (3) is 150-200 MPa, the sintering temperature is 1500-1750° C., and the holding time is 3-8 h.

[0015] Preferably, the annealing in step (3) is carried out in an air atmosphere, the annealing temperature is 1200-1400° C., and the holding time is 12-20 h.

[0016] Preferably, the pump source is composed of a plurality of 450nm GaN or InGaN laser diodes, or the pump source is an intracavity frequency-doubled optically pumped semiconductor laser, and the wavelength range of the output light is 440-480nm.

[0017] Preferably, the focusing coupling system includes a collimating lens and a focusing lens, the lens is a convex lens, and the focusing ratio is 1:0.8.

[0018] Preferably, the resonant cavity is a plano-planar cavity or a plano-concave cavity, the input mirror is a total reflection mirror, and the total reflection mirror is one of a plane mirror, a plano-convex mirror or a plano-concave mirror. The input mirror is coated with an anti-reflection film for the pump light band, a total reflection film for the laser or a high reflection film on the side close to the pump source; the output mirror is one of a plane mirror, a plano-convex mirror or a plano-concave mirror, and is coated with a film that is highly reflective for lasers in the required band (such as 550-620nm, etc.), and the laser transmittance is 1-40%.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The present invention can directly realize the output of semiconductor-pumped solid-state laser (yellow light), which is conducive to the miniaturization and integration of yellow solid-state lasers;

[0021] 2. Ce,Dy:LuGdAG transparent ceramics as laser gain medium, wherein Ce 3+ Co-doping, Dy 3+ Ions can transfer the absorbed wavelength photon energy to Ce 3+ ions, thereby increasing Ce 3+ 5d-4f transition of ions, Gd 3+Ion doping improves the energy level loss between ions. In addition, Gd 3+ As ions with large radius, doping makes the multi-ion doped lattice more stable, ultimately achieving efficient yellow light laser output.

[0022] 3. In the preparation of ceramic powder, the co-precipitation method is used to make the powder mixing more uniform and the sintering activity higher; in the sintering method, vacuum pre-sintering combined with hot isostatic pressing is used to sinter ceramics, which can more effectively obtain dense, optically high-quality Ce, Dy: LuGdAG transparent ceramics. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a structural schematic diagram of a solid-state laser provided by an embodiment of the present invention.

[0024] In the figure, 1-pump source, 2-focusing coupling system, 3-input mirror, 4-laser gain medium, 5-output mirror, 6-yellow laser output, 7-resonant cavity.

[0025] Figure 2 This is a SEM image of the ceramic sample after sintering and annealing in Example 1 of the present invention. DETAILED DESCRIPTION

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that the illustrations provided in the present embodiments are merely schematic illustrations of the basic concept of the present invention. Although the illustrations only show components relevant to the present invention and are not drawn according to the number, shape, and size of components in actual implementation, the shape, number, and proportion of each component in actual implementation may be arbitrarily changed, and the component layout may also be more complex.

[0027] like Figure 1 As shown, the present invention provides a low-threshold yellow solid-state laser based on energy transfer, comprising a pump source 1, a focusing coupling system 2, and a resonant cavity 7. The resonant cavity 7 includes an input mirror 3 and an output mirror 5 arranged opposite to each other in the resonant cavity, and a laser gain medium 4 disposed between the input mirror 3 and the output mirror 5. The pump source 1 converges pump light through the focusing coupling system 2 and irradiates the laser gain medium 4.

[0028] The pump source 1 can be a GaN or InGaN laser diode with a wavelength of about 450 nm or an intracavity frequency-doubled optical pump semiconductor laser, and the wavelength range of its output light is 440-480 nm.

[0029] The focusing coupling system 2 includes a collimating lens and a focusing lens, wherein the lens is a convex lens and the focusing ratio is 1:0.8.

[0030] The laser gain medium 4 is Ce, Dy: LuGdAG transparent ceramic, and its chemical formula is (Gd1-x-y Lu x Dy y Ce z )3Al5O 12 , where 0.30≤x≤0.5, 0.03≤y≤0.3, 0.005≤z≤0.02, where, by Ce 3+ Co-doping, Dy 3+ Ions can transfer the absorbed wavelength photon energy to Ce 3+ ions, thereby increasing Ce 3+ 5d-4f transition of ions, Gd 3+ Ion doping improves the energy level loss between ions. In addition, Gd 3+ As ions with large radius, doping makes the multi-ion doped lattice more stable, ultimately achieving efficient yellow light laser output.

[0031] The resonant cavity 7 is a plano-planar cavity or a plano-concave cavity, the input mirror 3 is a total reflection mirror, and the total reflection mirror is one of a plane mirror, a plano-convex mirror or a plano-concave mirror. The input mirror 3 is close to the pump source 1 and is coated with an anti-reflection film for the pump light band, a total reflection film for the laser or a high reflection film; the output mirror 5 is one of a plane mirror, a plano-convex mirror or a plano-concave mirror, and is coated with a film that is highly reflective for lasers in the required band (such as 550-620nm, etc.), and the laser transmittance is 1-40%.

[0032] The optical transmission path is as follows: the pump light emitted by the pump source 1 is focused by the focusing coupling system 2 onto the laser gain medium 4 located in the resonant cavity 7; the laser gain medium 4 absorbs the pump light, oscillates in the resonant cavity 7, and excites yellow laser light, which is output through the output mirror 5.

[0033] The above laser device was used to simulate the generation of 578nm laser:

[0034] Example 1: When the chemical formula of the laser gain medium used is (Gd 0.18 Lu 0.5 Dy 0.3 Ce 0.02 )3Al5O 12 , that is, when the values of x, y, and z are x=0.500, y=0.30, and z=0.02 respectively, 450nm GaN is used as the LD pump source. When the co-precipitation method is used, Dy2O3, Lu2O3, Eu2O3, and Gd2O3 raw materials are first dissolved in dilute HNO3 to prepare Dy(NO3)3, Gd(NO3)3, Eu(NO3)3, and Lu(NO3)3 solutions respectively. The calibrated nitrate solution is used as the raw material and the stoichiometric ratio (Gd 0.18 Lu 0.5 Dy 0.3 Ce0.02 )3Al5O 12 Measure a certain volume of nitrate solution separately and mix the five nitrates mentioned above together with continuous and vigorous stirring. To improve the powder properties, a 98.5% (NH4)2SO4 solution was selected as a dispersant and added dropwise to the continuously stirred mixed nitrate solution. A 1.4 mol / L NH4HCO3 solution was used as a precipitant. Finally, the pH was adjusted to 7.2 and the mixture was aged for 24 hours after stirring. The precipitate was then poured into a centrifuge, washed and filtered with deionized water, dried, ground and sieved, and calcined at 1000°C for 3 hours to obtain the corresponding powder. The powder was then pressed into shape, cooled, and other conditions to obtain a green blank. The green blank was pre-sintered at 1500°C for 3 hours under vacuum conditions. The vacuum-sintered sample was then placed in a hot isostatic pressing furnace chamber with a pressure of 150 MPa, a sintering temperature of 1500°C, and a sintering time of 3 hours. Finally, it was annealed in an air atmosphere at an annealing temperature of 1200°C for 12 hours to obtain transparent ceramics.

[0035] Figure 1 This is the SEM image of the ceramic sample after sintering and annealing in this example. It can be seen that the grain size does not exceed 1 μm and no pores appear, indicating that the ceramic is well densified and has good optical quality.

[0036] After that, the material is processed and coated, and the above laser test device is used to generate LD-pumped 578nm yellow laser.

[0037] Example 2: When the chemical formula of the laser gain medium used is (Gd 0.44 Lu 0.4 Dy 0.15 Ce 0.01 )3Al5O 12 , that is, when the values of x, y, and z are x=0.40, y=0.15, and z=0.01 respectively, 450nm GaN is used as the LD pump source. When the co-precipitation method is used, Dy2O3, Lu2O3, Eu2O3, and Gd2O3 raw materials are first dissolved in dilute HNO3 to prepare Dy(NO3)3, Gd(NO3)3, Eu(NO3)3, and Lu(NO3)3 solutions respectively. The calibrated nitrate solution is used as the raw material and the stoichiometric ratio (Gd 0.44 Lu 0.4 Dy 0.15 Ce 0.01 )3Al5O 12Measure a certain volume of nitrate solution and mix the five nitrates mentioned above together while stirring vigorously. To improve the powder properties, a 99.0% (NH4)2SO4 solution was used as a dispersant. Add the solution dropwise to the stirred mixed nitrate solution, using a 1.5 mol / L NH4HCO3 solution as a precipitant. Finally, adjust the pH to 7.5, stir, and age for 24 hours. The precipitate was then poured into a centrifuge, washed and filtered with deionized water, placed in an oven to dry, ground and sieved, and calcined at 1100°C for 6 hours to obtain the corresponding powder. The powder was then pressed into shape, cooled, and other conditions to obtain a blank. The blank was pre-sintered at 1600°C under vacuum conditions for 8 hours. The vacuum-sintered sample was then placed in a hot isostatic pressing furnace chamber with a pressure of 180 MPa, a sintering temperature of 1600°C, and a time of 5 hours. Finally, it was annealed in an air atmosphere at an annealing temperature of 1300°C for 15 hours to obtain transparent ceramics.

[0038] The SEM image of the ceramic sample after sintering and annealing in this embodiment is similar to that in Example 1.

[0039] After that, the material is processed and coated and the above laser test device is used to generate LD-pumped 578nm yellow laser.

[0040] Example 3: When the chemical formula of the laser gain medium used is (Gd 0.45 Lu 0.5 Dy 0.03 Ce 0.02 )3Al5O 12 , that is, when the values of x, y, and z are x=0.500, y=0.03, and z=0.02 respectively, 450nm GaN is used as the LD pump source. When the co-precipitation method is used, Dy2O3, Lu2O3, Eu2O3, and Gd2O3 raw materials are first dissolved in dilute HNO3 to prepare Dy(NO3)3, Gd(NO3)3, Eu(NO3)3, and Lu(NO3)3 solutions respectively. The calibrated nitrate solution is used as the raw material and the stoichiometric ratio (Gd 0.45 Lu 0.5 Dy 0.03 Ce 0.02 )3Al5O 12Measure a certain volume of nitrate solution and mix the five nitrates mentioned above together with continuous and vigorous stirring. To improve the powder properties, a 99.5% (NH4)2SO4 solution was used as a dispersant and added dropwise to the continuously stirred mixed nitrate solution. A 1.6 mol / L NH4HCO3 solution was used as a precipitant. Finally, the pH was adjusted to 7.8 and the mixture was aged for 24 hours after stirring. The precipitate was then poured into a centrifuge, washed and filtered with deionized water, placed in an oven to dry, ground and sieved, and calcined at 1200°C for 8 hours to obtain the corresponding powder. The powder was then pressed into shape, cooled, and other conditions to obtain a green blank. The green blank was pre-sintered at 1750°C for 15 hours under vacuum conditions. The vacuum-sintered sample was then placed in a hot isostatic pressing furnace chamber with a pressure of 200 MPa, a sintering temperature of 1750°C, and a time of 8 hours. Finally, it was annealed in an air atmosphere at an annealing temperature of 1400°C for 20 hours to obtain transparent ceramics.

[0041] The SEM image of the ceramic sample after sintering and annealing in this embodiment is similar to that in Example 1.

[0042] After that, the material is processed and coated and the above laser test device is used to generate LD-pumped 578nm yellow laser.

[0043] By comparison, it is found that the laser output effect of Example 2 is better, the simulated laser stability is better, and the slope efficiency is the highest at 9.7%.

Claims

1. A low-threshold yellow solid-state laser based on energy transfer, comprising a pump source, a focusing coupling system, and a resonant cavity; the resonant cavity comprises an input mirror and an output mirror arranged opposite to each other in the resonant cavity, and a laser gain medium disposed between the input mirror and the output mirror, characterized in that: The laser gain medium is Ce, Dy: LuGdAG transparent ceramic, and its chemical formula is (Gd 1-x-y-z Lu x Dy y Ce z )3Al5O 12 , where 0.30≤ x ≤0.5,0.03≤ y ≤0.3,0.005≤ z ≤0.02, the Ce, Dy: LuGdAG transparent ceramic is prepared by a co-precipitation method; The specific steps of preparing Ce, Dy: LuGdAG transparent ceramics by co-precipitation method include: (1) According to (Gd 1-x-y-z Lu x Dy y Ce z )3Al5O 12 According to the stoichiometric ratio of each element, Dy(NO3)3, Gd(NO3)3, Eu(NO3)3 and Lu(NO3)3 solutions were measured respectively, mixed and stirred evenly, and dispersant (NH4)2SO4 solution was added dropwise; (2) adding the mixed solution dropwise to a precipitant solution while stirring continuously, wherein the precipitant is NH3·H2O and / or NH4HCO3, and adjusting the pH value of the system to be between 7.2 and 7.8; aging and filtering to obtain a precursor precipitate; drying the precursor precipitate, grinding and sieving, and calcining to obtain a ceramic powder; (3) The ceramic powder is pressed into shape and cooled to obtain a green body, and the green body is pre-sintered under vacuum conditions. The vacuum-sintered sample is then hot isostatically pressed and annealed to obtain a transparent ceramic.

2. The low-threshold yellow solid-state laser based on energy transfer according to claim 1, characterized in that: The calcination temperature in step (2) is 1000-1200°C, and the holding time is 3-8h.

3. The low-threshold yellow solid-state laser based on energy transfer according to claim 1, characterized in that: The vacuum sintering temperature in step (3) is 1500-1750°C, and the holding time is 3-15h.

4. The low-threshold yellow solid-state laser based on energy transfer according to claim 1, characterized in that: The hot isostatic pressing pressure in step (3) is 150-200 MPa, the sintering temperature is 1500-1750°C, and the holding time is 3-8 hours.

5. The low-threshold yellow solid-state laser based on energy transfer according to claim 1, characterized in that: The annealing in step (3) is carried out in an air atmosphere, the annealing temperature is 1200-1400°C, and the holding time is 12-20h.

6. The low-threshold yellow solid-state laser based on energy transfer according to claim 1, characterized in that: The pump source is composed of a plurality of 450nm GaN or InGaN laser diodes, or the pump source is an intracavity frequency-doubled optical pump semiconductor laser, and the wavelength range of the output light is 440-480nm.

7. The low-threshold yellow solid-state laser based on energy transfer according to claim 1, characterized in that: The focusing coupling system includes a collimating lens and a focusing lens, wherein the lens is a convex lens and the focusing ratio is 1:0.

8.

8. The low-threshold yellow solid-state laser based on energy transfer according to claim 1, characterized in that: The resonant cavity is a flat cavity or a plano-concave cavity, the input mirror is a total reflection mirror, and the total reflection mirror is one of a plane mirror, a plano-convex mirror or a plano-concave mirror. The input mirror is coated with one of an anti-reflection film for the pump light band, a total reflection film for the laser or a high reflection film on the side close to the pump source; the output mirror is one of a plane mirror, a plano-convex mirror or a plano-concave mirror, and is coated with a film that is highly reflective for laser light in the required band, and has a laser transmittance of 1-40%.

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