Spatial and temporal characterization of a Bessel beam produced using a conical mirror

We experimentally analyze a Bessel beam produced with a conical mirror, paying particular attention to its superluminal and diffraction-free properties. We spatially characterized the beam in the radial and on-axis dimensions and verified that the central peak does not spread over a propagation distance of 73 cm. In addition, we measured the superluminal phase and group velocities of the beam in free space. Both spatial and temporal measurements show good agreement with the theoretical predictions.

Figure 1

(Color online) (a) Formation of the Bessel beam from a plane wave by a conical mirror and a plot of its radial intensity profile. (b) Schematic of experimental apparatus used for phase- and group-velocity measurements. PBS means polarizing beam splitter.

Figure 2

Normalized radial intensity profile for several CCD camera positions.

Figure 3

(Color online) (a) Measured intensity profile (dots) and numerical calculation (line) at 18.8 cm distance from the conical mirror. (b) On-axis intensity: experimental data (dots) and theoretical calculation (line).

Figure 4

(Color online) Cw measurements: period of the interference fringes $\Delta z$ as a function of the angle $\phi$ between the direction of propagation of the Gaussian and Bessel beams (dots) together with the theoretical fit (line).

Figure 5

(Color online) Pulsed measurements: normalized fringe visibility for $z=219$ (◼), 119 (▲), and 19 (●) mm as a function of the plane mirror translation $\Delta x$. The experimental data are fitted with a Gaussian curve.

Figure 6

(Color online) Displacement $x$ of the Michelson interferometer plane mirror, at which the visibility is maximized, as a function of the CCD camera position $z$ (dots) with a linear fit (line).