Measurement of superluminal phase and group velocities of Bessel beams in free space

TL;DR

This paper experimentally confirms that optical Bessel beams exhibit superluminal phase and group velocities in free space using interferometry with continuous wave and femtosecond pulses.

Contribution

It provides the first direct interferometric measurements of superluminal phase and group velocities of Bessel beams in free space.

Findings

Confirmed superluminal phase velocity of Bessel beams

Confirmed superluminal group velocity of Bessel beams

Used conical mirror to generate Bessel beams in free space

Abstract

We report on an interferometry-based measurement of the phase and group velocities of optical Bessel beams, providing confirmation of their superluminal character in the non-diffractive region. The measurements were performed in free space with a continuous wave laser and femtosecond pulses for phase and group velocities respectively. The Bessel beams were produced using a conical mirror.