White light Bessel-like beams generated by miniature all-fiber device.

Micron-sized white light propagation invariant beams generated by a simple and compact fiber device are presented. The all-fiber device is fabricated by splicing a short piece of large-core multimode fiber onto a small-core single mode white light delivery fiber. Because this fiber device offers an inherent spatial coherence, nondiffracting white light beams can be created with a temporally incoherent broadband light source (a halogen bulb) and, most importantly, the surrounding fringes don't fade as the bandwidth of the light source increases because the underlying physics of this fiber device is different from that of the axicon. White light Bessel-like beams have been generated from multimode fibers with core diameters of 50 μm, 105 μm, and 200 μm. The distance of nondiffracting propagation of the white light Bessel beam increases with increasing core size of the multimode fiber. Propagation characteristics of red, green, and blue individual beams are also presented.