Concentration, morphology and composition-dependent thermal diffusivity changes occurring in bimetallic Au-Ag nanoparticles synthesized by femtosecond laser ablation were investigated using a dual- beam mode matched thermal lens technique. The synthesis utilized the variation in ablation time of silver plate kept immersed in already synthesized gold nanoparticle seeds. Thermal diffusivity values were found to increase both with an increase in concentration of the samples as well as an increase in Ag/Au weight percentage ratio. Au-Ag core–shell and nanoalloy structure show much greater variation in the thermal diffusivity compared to the other samples. A possible explanation could be the modified surface state density of the bimetallic nanoparticles. A single beam z scan technique using an Nd:YAG laser operating at a wavelength of 532 nm was employed for the nonlinear optical characterization of the samples. At a fixed laser input fluence, a switching behavior from saturable absorption (SA) to reverse saturable absorption (RSA) was observed as the ablation time of the silver plate in gold nanoparticle solution increased. The effect of laser input fluence on nonlinear optical properties of core–shell and nanoalloy structures was also studied and the optical limiting threshold of nanoalloy was calculated. The results revealed an increase in the nonlinear absorption coefficient with an increase in input fluence. A linear variation of the limiting threshold was also observed with an increase in input fluence. Thermal diffusivity studies find applications in photo thermal therapies and optical limiting properties find application in optoelectronic switches.

使用双光束模式匹配热透镜技术研究了飞秒激光烧蚀合成的双金属Au-Ag纳米颗粒中发生的浓度，形貌和成分相关的热扩散率变化。合成利用了浸没在已经合成的金纳米粒子种子中的银板的消融时间的变化。发现热扩散率值随着样品浓度的增加以及Ag / Au重量百分比的增加而增加。与其他样品相比，Au-Ag核-壳和纳米合金的结构在热扩散率上显示出更大的变化。可能的解释可能是双金属纳米粒子的表面态密度发生了变化。使用Nd的单束z扫描技术：使用波长为532 nm的YAG激光器进行样品的非线性光学表征。在固定的激光输入能量密度下，随着金纳米颗粒溶液中银板的消融时间增加，观察到了从饱和吸收（SA）到反向饱和吸收（RSA）的转换行为。还研究了激光输入能量密度对核-壳和纳米合金结构的非线性光学特性的影响，并计算了纳米合金的光学极限阈值。结果表明，非线性吸收系数随输入注量的增加而增加。随着输入注量的增加，还可以观察到极限阈值的线性变化。