Miyamoto Isamu, Cvecek Kristian, Schmidt Michael
Osaka University, 1-12 Yama-Oka, Suita, Osaka 565-0871, Japan.
Opt Express. 2011 May 23;19(11):10714-27. doi: 10.1364/OE.19.010714.
Thermal conduction model is presented, by which nonlinear absorptivity of ultrashort laser pulses in internal modification of bulk glass is simulated. The simulated nonlinear absorptivity agrees with experimental values with maximum uncertainty of ± 3% in a wide range of laser parameters at 10 ps pulse duration in borosilicate glass. The nonlinear absorptivity increases with increasing energy and repetition rate of the laser pulse, reaching as high as 90%. The increase in the average absorbed laser power is accompanied by the extension of the laser-absorption region toward the laser source. Transient thermal conduction model for three-dimensional heat source shows that laser energy is absorbed by avalanche ionization seeded by thermally excited free-electrons at locations apart from the focus at pulse repetition rates higher than 100 kHz.
提出了热传导模型，利用该模型模拟了超短激光脉冲在块状玻璃内部改性中的非线性吸收率。在硼硅酸盐玻璃中，当脉冲持续时间为10 ps时，在很宽的激光参数范围内，模拟得到的非线性吸收率与实验值相符，最大不确定度为±3%。非线性吸收率随激光脉冲能量和重复频率的增加而增大，高达90%。平均吸收激光功率的增加伴随着激光吸收区域向激光源方向的扩展。三维热源的瞬态热传导模型表明，在脉冲重复频率高于100 kHz时，激光能量在远离焦点的位置被热激发自由电子引发的雪崩电离所吸收。
