Self-interaction of ultrashort pulses in an epsilon-near-zero nonlinear material at the telecom wavelength

TL;DR

This paper investigates how femtosecond telecom-wavelength pulses interact within a thin indium tin oxide ENZ material, revealing effects of chirp and standing-wave formation due to multiple reflections and high nonlinearity.

Contribution

It introduces a numerical study of self-interaction effects of ultrashort pulses in ENZ materials, highlighting the roles of chirp and subwavelength reflections in spectral and temporal dynamics.

Findings

Self-interaction occurs due to multiple reflections in subwavelength ENZ layers.

Chirp magnitude and sign significantly influence spectral and temporal energy redistribution.

A standing-wave-like state can form with two pulses, localizing energy in the sample's middle.

Abstract

Dynamics of femtosecond pulses with the telecom carrier wavelength is investigated numerically in a subwavelength layer of an indium tin oxide (ITO) epsilon-near-zero (ENZ) material with high dispersion and high nonlinearity. Due to the subwavelength thickness of the ITO ENZ material, and the fact that the pulse's propagation time is shorter than its temporal width, multiple reflections give rise to self-interaction in both spectral and temporal domains, especially at wavelengths longer than the ENZ point, at which the reflections are significantly stronger. A larger absolute value of the pulse's chirp strongly affects the self-interaction by redistributing energy between wavelengths, while the sign of the chirp affects the interaction in the temporal domain. It is also found that, when two identical pulses are launched simultaneously from both ends, a subwavelength counterpart of a standing-wave state can be established. It shows robust energy localization in the middle of the sample, in terms of both the spectral and temporal intensity distributions.