Chiral excitation and effective bandwidth enhancement in tilted coupled optical waveguide lattices

TL;DR

This paper explores how tilting waveguides in a coupled optical lattice induces chiral light propagation and enhances effective bandwidth, mimicking atomic drift effects and breaking symmetry constraints.

Contribution

It introduces a novel waveguide tilt technique to achieve directional light excitation and bandwidth enhancement in optical lattices, emulating atomic drift phenomena.

Findings

Chiral light propagation observed in tilted waveguide lattices

Bandwidth enhancement achieved through geometric tilt

Light coupling occurs even with large detuning

Abstract

Light escape from an optical waveguide side-coupled to a waveguide lattice provides a photonic analogue of the spontaneous emission process of an excited two-level atom in a one-dimensional array of cavities. According to the Fermi golden rule the decay process is prevented when the atomic resonance frequency falls in a stop band of the lattice, while time-reversal symmetry ensures that the spontaneously emitted photon has equal probability to propagate in opposite directions of the array. This scenario is drastically modified when the quantum emitter drifts along the lattice at a constant speed. In the waveguide optics analogue the atomic drift is emulated by the introduction of a slight geometric tilt of the waveguide axis from the lattice axis. In this setting light excitation in the array is chiral, i.e. light propagates in a preferred direction of the lattice, and coupling is allowed even though the waveguide is far detuned from the tight-binding lattice band.