Enhanced Kerr electro-optic nonlinearity through cascaded Pockels effects

TL;DR

This paper demonstrates a significant enhancement of Kerr electro-optic nonlinearity in ferroelectric crystals via cascaded Pockels effects, enabling electric field control of nonlinear phase shifts with potential applications in photonics.

Contribution

The study introduces a novel structure that combines cascaded Pockels effects with second-harmonic generation, achieving over three orders of magnitude increase in electro-optic nonlinearity.

Findings

Nonlinear phase shift is significantly increased.

Effective nonlinear refractive index can be tuned positively or negatively.

Enhanced nonlinearity exceeds intrinsic values by over three orders of magnitude.

Abstract

We demonstrated a large enhancement of Kerr electro-optic nonlinearity through cascaded Pockels effects in a domain inversion ferroelectric crystal. We designed a structure that can implement the cascaded Pockels effects and second-harmonic generation simultaneously. The energy coupling between the fundamental lights of different polarizations led to a large nonlinear phase shift, and thus an effective electro-optic nonlinear refractive index. The effective nonlinearity can be either positive or negative, causing the second-harmonic spectra to move towards the coupling center, which in turn, offered us a way to measure the effective electro-optic nonlinear refractive index. The corresponding enhanced Kerr electro-optic nonlinearity is more than three orders of magnitude higher than the intrinsic value. These results open a door to manipulate the nonlinear phase by applying external electric field instead of light intensity in noncentrosymmetric crystals.