Non-adiabatic Modal Dynamics around Exceptional Points in an All-Lossy Dual-Mode Optical Waveguide: Towards Chirality Driven Asymmetric Mode-Conversion

TL;DR

This paper demonstrates how an all-lossy optical waveguide with an exceptional point enables topologically controlled, asymmetric mode conversion, with potential applications in chirality-driven photonic devices.

Contribution

It introduces a novel all-lossy waveguide design with inhomogeneous loss profile that exhibits exceptional point physics and enables robust, direction-dependent mode conversion.

Findings

Breakdown of adiabatic evolution near the EP.

Mode conversion depends on light propagation direction.

Robust, topologically controlled asymmetric mode transfer.

Abstract

We report a 1D planar optical waveguide with transverse distribution of inhomogeneous loss profile, which exhibits an exceptional point (EP). The waveguide hosts two leaky resonant modes; where the interaction between them in the vicinity of the EP is controlled by proper adjustment of the inhomogeneity in attenuation profile only. We study the adiabatic dynamics of propagation constants of the coupled modes by quasi-static encirclement of control parameters around the EP. Realizing such an encirclement with the inhomogeneous loss distribution along the direction of light propagation, we report the breakdown of adiabatic evolution of two coupled modes through the waveguide in presence of an EP. Here, during conversion the output mode is irrespective of the choice of input excited mode but depends on the direction of light transportation. This topologically controlled, robust scheme of asymmetric mode conversion in the platform of the proposed all-lossy waveguide structure may open up an extensive way-out for implementation of state-transfer applications in chirality driven waveguide-based devices.