Structural modification of transparent materials with band gap by laser radiation at the absorption edge

The problem of control over the process of structural modification of transparent materials by laser radiation is currently of great practical interest. This work proposes a novel method of controllable modification of a material structure, using laser pulses with wavelength at the material fundamental absorption edge. The method is based on the effect of thermal shift of the semiconductor absorption edge. The structure is modified by local heating of the material with laser pulses focused inside a transparent semiconductor. The laser heating process is investigated numerically and experimentally in order to determine the conditions under which the preset increase in temperature occurs in the local material area. As clarified, the heating is a threshold process and can be of two spatial structures: spot-like and line-like. The proposed method provides temperature changes in a large range, and therefore can be used for different structural modifications. It has multiple applications in practical tasks such as the optical recording of information, the formation of various photonic or other microstructures with complicated topology inside transparent materials, and the dividing of semiconductor wafers into chips. (C) 2019 Optical Society of America