Visible-band dispersion by a tapered air-core Bragg waveguide.

ABSTRACT

We describe out-coupling of visible band light from a tapered hollow waveguide with TiO(2)/SiO(2) Bragg cladding mirrors. The mirrors exhibit an omnidirectional band for TE-polarized modes in the ~490 to 570 nm wavelength range, resulting in near-vertical radiation at mode cutoff positions. Since cutoff is wavelength-dependent, white light is spatially dispersed by the taper. Resolution on the order of 2 nm is predicted and corroborated by experimental results. These tapers can potentially form the basis for compact micro-spectrometers in lab-on-a-chip and optofluidic micro-systems.