Layer compression and enhanced optical properties of few-layer graphene nanosheets induced by ion irradiation

TL;DR

This study demonstrates that ion irradiation can compress few-layer graphene nanosheets, enhancing their optical properties and improving their performance as saturable absorbers in waveguide lasers.

Contribution

First experimental demonstration of layer compression and optical enhancement of graphene nanosheets via ion irradiation, leading to improved laser performance.

Findings

Layer-to-layer distance reduced after ion irradiation.

Enhanced polarization-dependent light absorption observed.

Improved Q-switched laser performance with higher repetition rate.

Abstract

Graphene has been recognized as an attractive two-dimensional material for fundamental research and wide applications in electronic and photonic devices owing to its unique properties. The technologies to modulate the properties of graphene are of continuous interest to researchers in multidisciplinary areas. Herein, we report on the first experimental observation of the layer-to-layer compression and enhanced optical properties of few-layer graphene nanosheets by applying the irradiation of energetic ion beams. After the irradiation, the space between the graphene layers was reduced, resulting in a tighter contact between the few-layer graphene nanosheet and the surface of the substrate. This processing also enhanced the interaction between the graphene nanosheets and the evanescent-field wave near the surface, thus reinforcing the polarization-dependent light absorption of the graphene layers (with 3-fold polarization extinction ratio increment). Utilizing the ion-irradiated graphene nanosheets as saturable absorbers, the passively Q-switched waveguide lasing with considerably improved performances was achieved, owing to the enhanced interactions between the graphene nanosheets and evanescent field of light. The obtained repetition rate of waveguide laser was up to 2.3 MHz with a pulse duration of 101 ns.