Visual observation of optical Floquet-Bloch oscillations

TL;DR

This paper introduces and visually demonstrates Floquet-Bloch oscillations in waveguide arrays, revealing exotic properties like fractal spectra and fractional tunneling, advancing wave manipulation techniques.

Contribution

It proposes the concept of Floquet-Bloch oscillations, extending Bloch oscillations to Floquet systems, and provides the first experimental observation of these phenomena.

Findings

Observation of Floquet-Bloch oscillations in waveguide arrays

Revealed fractal spectrum and fractional Floquet tunneling

Demonstrated new wave manipulation method

Abstract

Bloch oscillations, an important transport phenomenon, have extensively been studied in static systems but remain largely unexplored in Floquet systems. Here, we propose a new type of Bloch oscillations, namely the "Floquet-Bloch oscillations," which refer to rescaled Bloch oscillations with a period of extended least common multiple of the modulation and Bloch periods. We report the first visual observation of such Floquet-Bloch oscillations in femtosecond-laser-written waveguide arrays by using waveguide fluorescence microscopy. These Floquet-Bloch oscillations exhibit exotic properties, such as fractal spectrum and fractional Floquet tunneling. This new transport mechanism offers an intriguing method of wave manipulation, which has significant applications in coherent quantum transport.