Weakening heat accumulation behavior caused by femtosecond pulses for high-performance antireflection micro-nano porous structures

Abstract

Multi-scale porous micro-nano structures can exhibit perfect broadband antireflection performances on material surface and have essential importance in optical and optoelectronic devices. However, heat accumulation between the subsequent laser pulses increases the temperature of the material substrate and eventually changes micro-nano structures, affecting the antireflection performance. In this study, a strategy for preparing antireflection structures was proposed by weakening the heat accumulation behavior of femtosecond pulses on materials, and the proposed strategy was experimentally demonstrated. This strategy can tune the multi-scale porosity properties of the surface structure by cooling the material substrate under high-repetition-rate laser irradiation. Thus, comprehensively improved antireflection performances can be realized over ultraviolet to near-infrared spectral regions. When the pulse repetition rate is 150 kHz, the average reflectance of the silicon and Cu surfaces is 3.50% and 3.82%, respectively. The reduction rate of the reflectance on silicon and Cu surfaces reaches 25.21% and 19.75%, respectively. More importantly, the processing speed increased three times by increasing the pulse repetition rate. The presented strategy opens a novel and convenient route for the preparation of multi-scale porous micro-nano structures for various types of structural absorbing materials.