1,2-dichloroethane (${{\rm C}_2}{{\rm H}_4}{{\rm Cl}_2}$) and 1,2-dibromoethane (${{\rm C}_2}{{\rm H}_4}{{\rm Br}_2}$) show linear absorption (LA) and stimulated light scattering in response to the excitation by 820 nm 18 fs laser pulses. Using the $Z$-scan technique, with these pulses separated by 12.2 ns (much shorter than both samples’ thermal diffusivity time constants ${\tau _{\rm th}}$’s) and extended over 41 ms (considerably longer than ${\tau _{\rm th}}$’s), we investigated the thermal lensing effect of both samples and found that LA dominates their heating. In addition, relative to ${{\rm C}_2}{{\rm H}_4}{{\rm Br}_2}$, ${{\rm C}_2}{{\rm H}_4}{{\rm Cl}_2}$ shows more/less thermal lensing effect before/after the exposure time passes ${\tau _{\rm th}}$’s. This means that the thermal lensing effect is more severely reinforced by heating and stabilized by thermal diffusivity in ${{\rm C}_2}{{\rm H}_4}{{\rm Cl}_2}$ than in ${{\rm C}_2}{{\rm H}_4}{{\rm Br}_2}$. Notably, the Kerr lensing effect is negligible in this study, although it is noticeable in a $Z$-scan study with 17 ps laser pulses.

中文翻译：

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1,2-二氯乙烷和1,2-二溴乙烷中的短脉冲诱导热透镜效应

1,2-二氯乙烷（$ {{\ rm C} _2} {{\ rm H} _4} {{\ rm Cl} _2} $）和1,2-二溴乙烷（$ {{\ rm C} _2} { {\ rm H} _4} {{\ rm Br} _2} $）响应820 nm 18 fs激光脉冲的激发，显示出线性吸收（LA）和受激光散射。使用$ Z $ -scan技术，这些脉冲之间的间隔为12.2 ns（比两个样本的热扩散时间常数$ {\ tau _ {\ rm th}} $ 's短），并延长了41 ms（长得多）与$ {\ tau _ {\ rm th}} $相比），我们研究了两个样品的热透镜效应，发现LA主导了它们的加热。此外，相对于$ {{\ rm C} _2} {{\ rm H} _4} {{\ rm Br} _2} $而言，$ {{\ rm C} _2} {{\ rm H} _4} { {\ rm Cl} _2} $在曝光时间经过$ {\ tau _ {\ rm th}} $ s之前/之后，显示出更多/更少的热透镜效果。这意味着，热透镜效应被更严重通过加热增强和在通过热扩散稳定的$ {{\ RMÇ} _2} {{\ RM H} _4} {{\ RM氯} _2} $比$ {{ \ rm C} _2} {{\ rm H} _4} {{\ rm Br} _2} $。值得注意的是，尽管在以17 ps激光脉冲进行的$ Z $扫描研究中值得注意，但Kerr透镜效应在本研究中可以忽略不计。