Measurement of superluminal phase and group velocities of Bessel beams   in free space
  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. 
B. Braverman, K. B. Kuntz, M. Lobino, E. M. Pessina, and A. I. Lvovsky