The influence of ultrafast temporal energy regulation on the morphology of Si surfaces through femtosecond double pulse laser irradiation

TL;DR

This study explores how ultrafast double pulse laser irradiation influences silicon surface morphology, revealing that increasing pulse delay reduces damage and ripple features, highlighting the role of pulse timing in nano/micro fabrication.

Contribution

It introduces a novel understanding of how ultrafast pulse timing affects silicon surface modifications, offering an alternative mechanism for controlling ripple periodicity.

Findings

Damage area decreases with pulse delay

Crater depth and ripple periodicity reduce by 3-4% with increased delay

Pulse shaping can enhance nano/micro processing precision

Abstract

The effect of ultrashort laser-induced morphological changes upon irradiation of silicon with double pulse sequences is investigated under conditions that lead to mass removal. The temporal delay between twelve double and equal-energy pulses (Ep=0.24J/cm2 each, with pulse duration tp=430fs, 800nm laser wavelength) was varied between 0 and 14ps and a decrease of the damaged area, crater depth size and periodicity of the induced subwavelength ripples (by 3-4%) was observed with increasing pulse delay. The proposed underlying mechanism is based on the combination of carrier excitation and energy thermalization and capillary wave solidification and aims to provide an alternative explanation to the control of ripple periodicity by temporal pulse tailoring. This work demonstrates the potential of pulse shaping technology to improve nano/micro processing.