Superluminal propagation and broadband omnidirectional antireflection in optical reflectionless potentials

TL;DR

This paper demonstrates broadband, omnidirectional antireflection and superluminal pulse delay using reflectionless potentials in stratified optical media, with potential applications in optical coatings and pulse control.

Contribution

It presents the design and experimental realization of reflectionless potentials in stratified media that achieve broadband, polarization-independent antireflection and negative pulse delay.

Findings

< 1% reflection over 350-2500 nm range

Negative delay of about 31 femtoseconds observed

Reflectionless potentials are polarization independent

Abstract

Reflectionless potentials (RPs) represent a class of potentials that offer total transmission in the context of one dimensional scattering. Optical realization of RPs in stratified medium can exhibit broadband omnidirectional antireflection property. In addition to the antireflection property, RPs are also expected to demonstrate negative delay. We designed refractive index profiles conforming to RPs and realize them in stratified media consisting of Al2O3 and TiO2 heterolayers. In these structures we observed < 1% reflection over the broad wavelength range of 350 nm to 2500 nm for angles of incidence 0 - 50 degrees. The observed reflection and transmission response of RPs are polarization independent. A negative delay of about 31 fsec with discernible pulse narrowing was observed in passage through two RPs. These RPs can be interesting for optical instrumentation as broadband, omni-directional antireflection coatings as well as in pulse control and transmission applications like delay lines.