Large few-layer hexagonal boron nitride flakes for nonlinear optics

TL;DR

This paper presents a method to fabricate large, few-layer hexagonal boron nitride flakes suitable for nonlinear optical applications, demonstrating integration with photonic structures and enhanced second-harmonic generation signals.

Contribution

It introduces a fabrication technique for large-area, few-layer hBN flakes and demonstrates their integration with photonic microstructures for nonlinear optics.

Findings

Large-area hBN flakes up to 5000 μm² fabricated.

Successful integration of hBN with circular Bragg grating.

Enhanced and uniform second-harmonic generation observed.

Abstract

Hexagonal boron nitride (hBN) is a layered dielectric material with a wide range of applications in optics and photonics. In this work, we demonstrate a fabrication method for few-layer hBN flakes with areas up to 5000 $\rm \mu m$. We show that hBN in this form can be integrated with photonic microstructures: as an example, we use a circular Bragg grating (CBG). The layer quality of the exfoliated hBN flake on a CBG is confirmed by second-harmonic generation (SHG) microscopy. We show that the SHG signal is uniform across the hBN sample outside the CBG and is amplified in the centre of the CBG.