Nonlinear Negative Refraction by Difference Frequency Generation

TL;DR

This paper introduces a novel nonlinear difference frequency generation method to achieve negative refraction with wide tunability, low loss, and practical potential for imaging applications, overcoming limitations of previous approaches.

Contribution

The work demonstrates both theoretically and experimentally a new scheme for nonlinear negative refraction using a thin BBO crystal, enabling optical focusing and broad tunability.

Findings

Successful experimental demonstration of nonlinear negative refraction.

Achieved optical focusing using the nonlinear negative refraction scheme.

Wide tunability of the negative refraction effect.

Abstract

Negative refraction has attracted much interest for its promising capability in imaging applications. Such an effect can be implemented by negative index meta-materials, however, which are usually accompanied by high loss and demanding fabrication processes. Recently, alternative nonlinear approaches like phase conjugation and four wave mixing have shown advantages of low-loss and easy-to-implement, but associated problems like narrow accepting angles can still halt their practical applications. Here we demonstrate theoretically and experimentally a new scheme to realize negative refraction by nonlinear difference frequency generation with wide tunability, where a thin BBO slice serves as a negative refraction layer bending the input signal beam to the idler beam at a negative angle. Furthermore, we realize optical focusing effect using such nonlinear negative refraction, which may enable many potential applications in imaging science.