Refractive index inhomogeneity is one of the important characteristics of optical coating material, which is one of the key factors to produce loss to the ultra-low residual reflection coatings except using the refrac...Refractive index inhomogeneity is one of the important characteristics of optical coating material, which is one of the key factors to produce loss to the ultra-low residual reflection coatings except using the refractive index inhomogeneity to obtain gradient-index coating. In the normal structure of antireflection coatings for center wavelength at 532 nm, the physical thicknesses of layer H and layer L are 22.18 nm and 118.86 nm, respectively. The residual reflectance caused by refractive index inhomogeneity(the degree of inhomogeneous is between -0.2 and 0.2) is about 200 ppm, and the minimum reflectivity wavelength is between 528.2 nm and 535.2 nm. A new numerical method adding the refractive index inhomogeneity to the spectra calculation was proposed to design the laser antireflection coatings, which can achieve the design of antireflection coatings with ppm residual reflection by adjusting physical thickness of the couple layers. When the degree of refractive index inhomogeneity of the layer H and layer L is-0.08 and 0.05 respectively, the residual reflectance increase from zero to 0.0769% at 532 nm. According to the above accuracy numerical method, if layer H physical thickness increases by 1.30 nm and layer L decrease by 4.50 nm, residual reflectance of thin film will achieve to 2.06 ppm. When the degree of refractive index inhomogeneity of the layer H and layer L is 0.08 and -0.05 respectively, the residual reflectance increase from zero to 0.0784% at 532 nm. The residual reflectance of designed thin film can be reduced to 0.8 ppm by decreasing the layer H of 1.55 nm while increasing the layer L of 4.94 nm.展开更多
A novel four light ray path test method for measuring residual reflectance has been presented. Residual reflectance spatial distribution at a cladding interface was measured using the technique. Residual reflectance c...A novel four light ray path test method for measuring residual reflectance has been presented. Residual reflectance spatial distribution at a cladding interface was measured using the technique. Residual reflectance could be on the order of 10-5 by matching the refractive index of Nd:glass, polymer, and cladding glass and eliminating defects in the adhesive layer. Residual reflection spatial distribution appears to be similar to Newton rings due to the edge surface flatness. The relationship between the residual reflectance and the edge surface flatness was discussed, and the results revealed that the edge surface flatness is very important during the cladding process.展开更多
This paper investigates the monolithic edge-cladding process for the elliptical disk of N31-type Nd-doped phosphate laser glass,which will be utilized under liquid cooling conditions for high-power laser systems.The t...This paper investigates the monolithic edge-cladding process for the elliptical disk of N31-type Nd-doped phosphate laser glass,which will be utilized under liquid cooling conditions for high-power laser systems.The thermal stress,interface bubbles and residual refiectivity,which are due to high-temperature casting and bonding during the monolithic edge-cladding process,are simulated and determined.The applied mould is optimized to a rectangular cavity mould,and the casting temperature is optimized to 1000℃.The resulting lower bubble density makes the mean residual refiectivity as low as 6.75×10^(-5),which is enough to suppress the amplified spontaneous emission generated in the Nd-glass disk,and the resulting maximum optical retardation is converged to 10.2–13.3 nm/cm,which is a favourable base for fine annealing to achieve the stress specification of less than or equal to 5 nm/cm.After fine annealing at the optimized 520℃,the maximum optical retardation is as low as 4.8 nm/cm,and the minimum transmitted wavefront peak-to-valley value is 0.222 wavelength(632.8 nm).An N31 elliptical disk with the size of 194 mm×102 mm×40 mm can be successfully cladded by the optimized monolithic edge-cladding process,whose edge-cladded disk with the size of 200 mm×108 mm×40 mm can achieve laser gain one-third higher than that of an N21-type disk of the same size.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61405145 and 61235011)the Natural Science Foundation of Tianjin,China(Grant No.15JCZDJC31900)the China Postdoctoral Science Foundation(Grant Nos.2015T80115 and 2014M560104)
文摘Refractive index inhomogeneity is one of the important characteristics of optical coating material, which is one of the key factors to produce loss to the ultra-low residual reflection coatings except using the refractive index inhomogeneity to obtain gradient-index coating. In the normal structure of antireflection coatings for center wavelength at 532 nm, the physical thicknesses of layer H and layer L are 22.18 nm and 118.86 nm, respectively. The residual reflectance caused by refractive index inhomogeneity(the degree of inhomogeneous is between -0.2 and 0.2) is about 200 ppm, and the minimum reflectivity wavelength is between 528.2 nm and 535.2 nm. A new numerical method adding the refractive index inhomogeneity to the spectra calculation was proposed to design the laser antireflection coatings, which can achieve the design of antireflection coatings with ppm residual reflection by adjusting physical thickness of the couple layers. When the degree of refractive index inhomogeneity of the layer H and layer L is-0.08 and 0.05 respectively, the residual reflectance increase from zero to 0.0769% at 532 nm. According to the above accuracy numerical method, if layer H physical thickness increases by 1.30 nm and layer L decrease by 4.50 nm, residual reflectance of thin film will achieve to 2.06 ppm. When the degree of refractive index inhomogeneity of the layer H and layer L is 0.08 and -0.05 respectively, the residual reflectance increase from zero to 0.0784% at 532 nm. The residual reflectance of designed thin film can be reduced to 0.8 ppm by decreasing the layer H of 1.55 nm while increasing the layer L of 4.94 nm.
文摘A novel four light ray path test method for measuring residual reflectance has been presented. Residual reflectance spatial distribution at a cladding interface was measured using the technique. Residual reflectance could be on the order of 10-5 by matching the refractive index of Nd:glass, polymer, and cladding glass and eliminating defects in the adhesive layer. Residual reflection spatial distribution appears to be similar to Newton rings due to the edge surface flatness. The relationship between the residual reflectance and the edge surface flatness was discussed, and the results revealed that the edge surface flatness is very important during the cladding process.
基金the Nd-glass project from National Major Science and Technology Project of China(No.G-GFZX0205010202.1)the Shanghai International Science&Technology Cooperation Program(No.18590712900)。
文摘This paper investigates the monolithic edge-cladding process for the elliptical disk of N31-type Nd-doped phosphate laser glass,which will be utilized under liquid cooling conditions for high-power laser systems.The thermal stress,interface bubbles and residual refiectivity,which are due to high-temperature casting and bonding during the monolithic edge-cladding process,are simulated and determined.The applied mould is optimized to a rectangular cavity mould,and the casting temperature is optimized to 1000℃.The resulting lower bubble density makes the mean residual refiectivity as low as 6.75×10^(-5),which is enough to suppress the amplified spontaneous emission generated in the Nd-glass disk,and the resulting maximum optical retardation is converged to 10.2–13.3 nm/cm,which is a favourable base for fine annealing to achieve the stress specification of less than or equal to 5 nm/cm.After fine annealing at the optimized 520℃,the maximum optical retardation is as low as 4.8 nm/cm,and the minimum transmitted wavefront peak-to-valley value is 0.222 wavelength(632.8 nm).An N31 elliptical disk with the size of 194 mm×102 mm×40 mm can be successfully cladded by the optimized monolithic edge-cladding process,whose edge-cladded disk with the size of 200 mm×108 mm×40 mm can achieve laser gain one-third higher than that of an N21-type disk of the same size.