White light propagation invariant beams.

Propagation invariant light fields such as Bessel light beams are of interest in a variety of current areas such as micromanipulation of atoms and mesoscopic particles, laser plasmas, and the study of optical angular momentum. Considering the optical fields as a superposition of conical waves, we discuss how the coherence properties of light play a key role in their formation. As an example, we show that Bessel beams can be created from temporally incoherent broadband light sources including a halogen bulb. By using a supercontinuum source we elucidate how the beam behaves as a function of bandwidth of the incident light field.