Realizing normal group-velocity dispersion in free space via angular dispersion

TL;DR

This paper demonstrates how to generate normal group-velocity dispersion in free space using angular dispersion, challenging previous assumptions and employing a versatile pulsed-beam shaper to produce both normal and anomalous GVD.

Contribution

It identifies conditions for normal GVD via angular dispersion and introduces a pulsed-beam shaper to symmetrically produce both types of GVD in free space for the first time.

Findings

Normal GVD can be achieved in free space with angular dispersion.

A pulsed-beam shaper can produce arbitrary angular-dispersion profiles.

Normal and anomalous GVD are realized on equal footing in free space.

Abstract

It has long been thought that normal group-velocity dispersion (GVD) cannot be produced in free space via angular dispersion. Indeed, conventional diffractive or dispersive components such as gratings or prisms produce only anomalous GVD. We identify the conditions that must be fulfilled by the angular dispersion introduced into a plane-wave pulse to yield normal GVD. We then utilize a pulsed-beam shaper capable of introducing arbitrary angular-dispersion profiles to symmetrically produce normal and anomalous GVD in free space, which are realized here on the same footing for the first time.