Spectral tunneling of lattice nonlocal solitons

TL;DR

This paper investigates how nonlocal nonlinearities in photorefractive media enable spatial solitons to tunnel through optical lattices, reducing radiative losses and allowing propagation beyond the Bragg angle.

Contribution

It demonstrates that nonlocal diffusion nonlinearities facilitate spectral tunneling of solitons, contrasting with local nonlinear media where losses are significant.

Findings

Self-bending solitons survive near and beyond the Bragg angle.

Spectral tunneling occurs through the spatial frequency band around the Bragg frequency.

Nonlocal nonlinearity reduces radiative losses during soliton propagation.

Abstract

We address spectral tunneling of walking spatial solitons in photorefractive media with nonlocal diffusion of the nonlinear response and an imprinted shallow optical lattice. In contrast to materials with local nonlinearities, where solitons travelling across the lattice close to the Bragg angle suffer large radiative losses, in photorefractive media with diffusion nonlinearity resulting in self-bending solitons survive when their propagation angle approaches and even exceeds the Bragg angle. In the spatial frequency domain this effect can be considered as tunneling through the band of spatial frequencies centered around the Bragg frequency where the spatial group velocity dispersion is positive.