Resonant Bloch-wave beatings

TL;DR

This paper introduces a new phenomenon called Bloch-wave beatings in waveguide arrays, characterized by periodic amplitude increases in Bloch oscillations due to resonant mode conversion, with potential implications for controlling light propagation.

Contribution

The study reveals the occurrence of Bloch-wave beatings in multimode waveguide arrays with bending and refractive index gradients, highlighting conditions for their prominence and control.

Findings

Bloch-wave beatings occur during resonant mode conversion.

Beating frequency decreases with reduced waveguide bending amplitude.

Beating amplitude is limited by the second Floquet-Bloch band.

Abstract

We introduce Bloch-wave beatings in arrays of multimode periodically bent waveguides with a transverse refractive index gradient. The new phenomenon manifests itself in the periodic drastic increase of the amplitude of the Bloch oscillations that accompanies resonant conversion of modes guided by the individual waveguides. The Bloch-wave beatings are found to be most pronounced when the length of the resonant mode conversion substantially exceeds the longitudinal period of the Bloch oscillations. The beating frequency decreases when the amplitude of waveguide bending decreases, while the beating amplitude is restricted by the amplitude of the Bloch oscillations that emerge from the second allowed band of the Floquet-Bloch lattice spectrum.