Refraction of space-time wave packets in a dispersive medium

TL;DR

This paper introduces a new law of refraction for space-time wave packets at dispersive interfaces, enabling control of their group velocity and potential applications in nonlinear optics.

Contribution

It formulates a novel refractive invariant and refraction law for space-time wave packets in dispersive media, verified experimentally in ZnSe and CdSe.

Findings

Established a new refraction law for ST wave packets

Verified the law in ZnSe and CdSe near their band edges

Demonstrated potential for nonlinear optics applications

Abstract

Space-time (ST) wave packets are a class of pulsed optical beams whose spatio-temporal spectral structure results in propagation invariance, tunable group velocity, and fascinating refractive phenomena. Here, we investigate the refraction of ST wave packets at a planar interface between two dispersive, homogeneous, isotropic media. We formulate a new refractive invariant for ST wave packets in this configuration, from which we obtain a law of refraction that determines the change in their group velocity across the interface. We verify this new refraction law in ZnSe and CdSe, both of which manifest large chromatic dispersion at near-infrared frequencies in the vicinity of their band edges. ST wave packets can thus be a tool in nonlinear optics for bridging large group-velocity mismatches in highly dispersive scenarios.