Giant second-harmonic generation enabled by bound-state continuum cavity on lithium niobate membra

TL;DR

This paper demonstrates a significant enhancement in second harmonic generation using bound-state continuum cavities on lithium niobate membranes, enabling more efficient integrated optical sources for various applications.

Contribution

It introduces a novel approach combining BIC cavities with lithium niobate membranes to achieve giant SHG enhancement and detailed numerical analysis of the underlying mechanisms.

Findings

Achieved up to 108-fold enhancement in SHG signal.

Demonstrated a minimum interaction time of 350 ps.

Realized a conversion efficiency of 4.77x10^-6.

Abstract

In this paper, we proposed and numerically demonstrated a giant enhancement up to 108 in both forward and backward propagation of the Second Harmonic Generation by combining the high-quality factor cavities of the Bound States in the Continuum and the excellent nonlinear optical crystal of lithium niobate. The enhancement factor is defined as the ratio of the second harmonic signal generated by the structure (lithium niobate membrane with Si grating) divided by the signal generated by lithium niobate membrane alone. Furthermore, a minimum interaction time of 350 ps is achieved despite the etching less lithium niobate membrane with a conversion efficiency of 4.77x10-6. The origin of the enhancements is linked to the excitation of a Fano-like shape Symmetry-Protected Mode (SPM) that is revealed by Finite Difference Time Domain (FDTD) simulations. The proposed platform opens the way to a new generation of efficient integrated optical sources compatible with nanophotonic devices for classical and quantum applications.