Temperature field simulation of chalcogenide glass ablation by nanosecond pulsed laser-based on pump–probe technology

Abstract

Chalcogenide glass (ChG) is one of the best candidate materials for the fabrication of micro-nano resolution photonic devices by laser direct writing (LDW). In this work, the thermodynamics and the surface structures evolution of As2S3 by nanosecond pulse are investigated by the dual-laser pump–probe system. Above the ablation threshold (124, 157, 196 mJ/cm2), the descend duration of sample surface reflectivity was observed to be 25, 48, and 80 ns, respectively. Furthermore, to research the effects of pulse irradiation and surface thermal energy diffusion on the sample surface temperature, the dual-temperature model is applied. At the lowest laser fluence, the temperature drops rapidly to the melting point in a short time (23 ns), which results in the formation of a crater in the pulse action area. At the highest fluence, the surface temperature decreases slowly to the melting point (77 ns). And during this period, the material surface is continuously heated, which leads to the deepening of melting depth. So, a deep crater (294 nm) is formed on the surface, and the reflectivity declines the slowest. Secondly, due to the highest temperature in the central region and the diffusion movement of heat energy, the rim structure and the small droplet structures will appear at a higher fluence.