The influence of boundary conditions on the form of the optical beam in the array of coupled optical waveguides

TL;DR

This paper explores how boundary conditions influence the shape of optical beams in coupled waveguide arrays, revealing intermediate beam forms between known oscillation modes based on input wave packet width.

Contribution

It introduces the concept of intermediate optical beam forms in waveguide arrays, dependent on boundary conditions and input wave packet width, expanding understanding beyond traditional modes.

Findings

Optical beam form varies with boundary conditions and input width.

Intermediate beam forms are observed between Bloch oscillations and breathing modes.

Qualitative explanation of beam transformation based on input width.

Abstract

We investigate the optical beam behavior in the periodical array of the coupled optical waveguides with the monotonic change of the refractive index in the transverse direction. We consider the dependence of the form of the optical beam on the boundary conditions. It is well known that if the input wave packet is wide enough, the optical Bloch oscillations occur, while for the enough narrow input wave packet the breathing mode is observed. We show that if the input wave packet is neither too wide nor too narrow, the optical beam takes a peculiar form which can be considered neither as the Bloch oscillations nor as the breathing mode. We qualitatively explain the transformation of this intermediate form of the optical beam when the width of the input wave packet changes.