Spatial solitons in periodic nano-structures

TL;DR

This paper develops a first-principles theory for the existence and stability of spatial solitons in subwavelength periodic semiconductor-dielectric structures, revealing how their properties depend on wavelength and geometry.

Contribution

It introduces a novel theoretical framework for analyzing TE and TM solitons in nanoscale periodic structures, including stability and mode profile insights.

Findings

TE and TM band structures become similar to homogeneous media at sub-100nm scales

TM solitons exhibit peaks inside dielectric slots reflecting subwavelength geometry

TM wave stability linked to slot waveguide modes and Brewster condition

Abstract

We present the first principle theory of the existence and stability of TE and TM spatial solitons in a subwavelength periodic semiconductor-dielectric structure. We have found that for the wavelength 1550nm and the interface separation close to and less than 100nm the band structure of the linear TE and TM waves becomes similar to the band structure of a homogeneous medium. The properties of TE solitons change accordingly. However, the transverse profiles of the TM solitons continue to reflect the subwavelength geometry of the structure and develop dominant intensity peaks inside the low index dielectric slots. Our stability analysis based on the linearized Maxwell equations indicates that the nonlinear TM waves can be approximated as the evanescently coupled modes of the slot waveguides with the low index dielectric core and the high index semiconductor cladding. Transition to the regime where the slot waveguides start to determine properties of TM waves is associated with the so called Brewster condition.