# Second-harmonic generation in multilayer hexagonal boron nitride flakes

## TL;DR

This study demonstrates that thick multilayer hexagonal boron nitride flakes exhibit strong second-harmonic generation, making them suitable for nonlinear optical applications and layer characterization despite their increased thickness.

## Contribution

It shows that thick hBN flakes can generate significant SHG, expanding their use in nonlinear optics and characterization beyond few-layer samples.

## Key findings

- Thick hBN flakes produce comparable SHG to few-layer samples.
- SHG mapping reveals layer structure in thick flakes.
- Thick flakes are easier to exfoliate with large sizes.

## Abstract

We report second-harmonic generation (SHG) from thick hexagonal boron nitride (hBN) flakes with approximately 109-111 layers. The resulting effective second-order susceptibility is similar to previously reported few-layer experiments. This confirms that thick hBN flakes can serve as a platform for nonlinear optics, which is useful because thick flakes are easy to exfoliate while retaining a large flake size. We also show spatial second-harmonic maps revealing that SHG remains a useful tool for the characterization of the layer structure even in the case of a large number of layers.

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Source: https://tomesphere.com/paper/1902.09060