Asymmetric nonlinear-mode-conversion in an optical waveguide with PT symmetry

TL;DR

This paper proposes a novel scheme for asymmetric nonlinear mode conversion in optical waveguides using PT symmetry, enabling unidirectional frequency doubling and advancing on-chip nonlinear optical device design.

Contribution

It introduces a new method combining frequency-doubling and PT symmetric modulation to achieve unidirectional nonlinear mode conversion in waveguides.

Findings

Demonstrated unidirectional second harmonic generation

Engineered one-way momentum via PT symmetry

Enabled asymmetric nonlinear mode transformation

Abstract

Asymmetric mode transformation in waveguide is of great significance for on-chip integrated devices with one-way effect, while it is challenging to achieve asymmetric nonlinear-mode-conversion (NMC) due to the limitations imposed by phase-matching. In this letter, we theoretically proposed a new scheme for realizing asymmetric NMC by combining frequency-doubling process and periodic PT symmetric modulation in an optical waveguide. By engineering the one-way momentum from PT symmetric modulation, we have demonstrated the unidirectional conversion from pump to second harmonic with desired guided modes. Our findings offer new opportunities for manipulating nonlinear optical fields with PT symmetry, which could further boost more exploration on on-chip nonlinear devices assisted by non-Hermitian optics.