Laser printed nano-gratings: orientation and period peculiarities

TL;DR

This study systematically investigates how the orientation and period of nanogratings in fused silica depend on laser scanning direction and polarization, revealing new insights into laser-material interactions at the nanoscale.

Contribution

It demonstrates the vectorial nature of light-matter interaction in nanograting formation, providing a new understanding of orientation and period peculiarities during laser writing.

Findings

Nanograting period depends on scanning direction.

Tilt of nanograting wave vector observed at fixed polarization.

Heat transport flux explains the orientation dependency.

Abstract

Understanding of material behaviour at nanoscale under intense laser excitation is becoming critical for future application of nanotechnologies. Nanograting formation by linearly polarised ultra-short laser pulses has been studied systematically in fused silica for various pulse energies at 3D laser printing/writing conditions, typically used for the industrial fabrication of optical elements. The period of the nanogratings revealed a dependence on the orientation of the scanning direction. A tilt of the nanograting wave vector at a fixed laser polarisation was also observed. The mechanism responsible for this peculiar dependency of several features of the nanogratings on the writing direction is qualitatively explained by considering the heat transport flux in the presence of a linearly polarised electric field, rather than by temporal and spatial chirp of the laser beam. The confirmed vectorial nature of the light-matter interaction opens new control of material processing with nanoscale precision.