Enhancement of the second-harmonic generation based on the cascaded second- and third-order nonlinear processes in a multimode optical microcavity

TL;DR

This paper investigates how cascaded second- and third-order nonlinear processes in multimode microcavities can enhance second-harmonic generation, revealing complex interactions like optical parametric oscillation and four-wave mixing that can be manipulated to improve efficiency.

Contribution

It demonstrates the coherent interplay of nonlinear processes in microcavities and proposes methods to surpass efficiency limitations of second-harmonic generation.

Findings

Non-degenerate optical parametric oscillation (OPO) appears at high pump powers.

The presence of third-order nonlinearity significantly alters the OPO threshold.

Interference between OPO and four-wave mixing can break the efficiency limit.

Abstract

Optical microcavities are often used to realize enhanced nonlinear optical interactions for highly efficient second-harmonic generation. With increased pump power, the efficiency of nonlinear frequency conversion can be increased further, while some other unwanted nonlinear effects will also emerge, leading to complicated dynamics or instability. Here, we study the interplay between cascaded second- and third-order nonlinear processes and investigate their impact on the second-harmonic generation in microcavities. It is found that the non-degenerate optical parametric oscillation (OPO) appears and the presence of $\chi^{(3)}$ process can modify the OPO threshold significantly when the multimode cavity is strongly pumped at the fundamental optical mode. One can even break the efficiency limitation of the second-harmonic mode restricted by the OPO by utilizing the interference between the OPO and the four-wave mixing. The present coherent interplay between nonlinear optical processes in microcavities is conducive to exploring new physics in the cavity nonlinear photonics.