This paper reports the 3D microprocessing of Si using a femtosecond laser at a wavelength of 1552.5 nm. As Si is optically transparent at this wavelength, the authors attempted to machine the back surface and interior of a Si substrate by a nonlinear absorption process, similar to the nonlinear process used to treat dielectric materials using visible and near-infrared ultrashort lasers. The femtosecond laser impinged on the front surface while focusing at or near the back surface. The authors scanned the laser beam linearly at several focus positions across the back surface at different scan speeds and repetition rates. Changes occurring in the interior of Si were observable only by infrared microscopy, whereas those on the back surface were observable by visible optical microscopy and scanning electron microscopy. Meanwhile, no change was detected on the front surface where the laser impinged. After a certain period, the point of irradiation showed changes; afterward, changes in the interior of Si began to occur continuously. However, the changes on the back surface occurred in a rather discrete manner, observed intermittently. This may be attributed to the heat accumulation due to multiple pulse irradiations, which increased the local temperature. This resulted in increased absorption along the incident laser path and prevented the delivery of a sufficient amount of energy to induce ablation on the back surface. The morphologies observed on the altered back surface were a granular band and a laser-induced periodic surface structure.This paper reports the 3D microprocessing of Si using a femtosecond laser at a wavelength of 1552.5 nm. As Si is optically transparent at this wavelength, the authors attempted to machine the back surface and interior of a Si substrate by a nonlinear absorption process, similar to the nonlinear process used to treat dielectric materials using visible and near-infrared ultrashort lasers. The femtosecond laser impinged on the front surface while focusing at or near the back surface. The authors scanned the laser beam linearly at several focus positions across the back surface at different scan speeds and repetition rates. Changes occurring in the interior of Si were observable only by infrared microscopy, whereas those on the back surface were observable by visible optical microscopy and scanning electron microscopy. Meanwhile, no change was detected on the front surface where the laser impinged. After a certain period, the point of irradiation showed changes; afterward, changes in the interior of Si began ...

中文翻译：

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使用红外飞秒激光脉冲对硅的背面和内部进行微加工

本文报道了使用波长为 1552.5 nm 的飞秒激光对 Si 进行 3D 微加工。由于 Si 在该波长下是光学透明的，因此作者试图通过非线性吸收工艺加工 Si 衬底的背面和内部，类似于使用可见光和近红外超短激光处理介电材料的非线性工艺。飞秒激光撞击前表面，同时聚焦在后表面或附近。作者以不同的扫描速度和重复率在背面的几个焦点位置线性扫描激光束。Si内部发生的变化只能通过红外显微镜观察到，而背面的变化可以通过可见光显微镜和扫描电子显微镜观察到。同时，在激光照射的前表面上没有检测到变化。一段时间后，照射点出现变化；之后，Si内部的变化开始不断发生。然而，背面的变化以相当离散的方式发生，间歇性地观察到。这可能是由于多次脉冲照射导致的热量积聚，从而增加了局部温度。这导致沿入射激光路径的吸收增加，并阻止传递足够量的能量以在背面引起烧蚀。在改变后的背面观察到的形态是粒状带和激光诱导的周期性表面结构。本文报道了使用 1552.5 nm 波长的飞秒激光对 Si 进行 3D 微加工。由于 Si 在该波长下是光学透明的，因此作者试图通过非线性吸收工艺加工 Si 衬底的背面和内部，类似于使用可见光和近红外超短激光处理介电材料的非线性工艺。飞秒激光撞击前表面，同时聚焦在后表面或附近。作者以不同的扫描速度和重复率在背面的几个焦点位置线性扫描激光束。Si内部发生的变化只能通过红外显微镜观察到，而背面的变化可以通过可见光显微镜和扫描电子显微镜观察到。同时，在激光照射的前表面上没有检测到变化。一段时间后，照射点有变化；之后，Si内部的变化开始了……