Second harmonic generation from multilayer hexagonal boron nitride
S Kim, JE Fröch, A Gardner, C Li, I Aharonovich, AS Solntsev
Proceedings of SPIE - The International Society for Optical Engineering | Published : 2019
We report second harmonic generation (SHG) from thick hexagonal boron nitride (hBN) flakes with approximately 109 layers. Surprisingly, the resulting signal is stronger when compared to previously reported few-layer experiments that showed the SHG efficiency gradually decreasing with the increasing thickness. 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.