Tapered photonic crystal fibers.

We demonstrate the tapering of a photonic crystal fiber to achieve a microstructure pitch of less than 300 nm. We probe the tapered fiber in the transverse geometry to demonstrate the scaling of the photonic bandgaps associated with the microstructure. We show that the fundamental gap can be shifted down to the communications wavelengths, or even further to the visible spectrum. Our optical measurements are correlated with band structure calculations.