Molding light flow from photonic band gap circuits to microstructured fibers

The authors demonstrate nearly lossless, broadband coupling of light between photonic band gap (PBG) circuits and photonic crystal fibers (PCFs) using two-dimensional design paradigms. A hollow-core PBG fiber yields a coupling efficiency of better than 94% over a bandwidth of 25% of the center frequency, with peak transmittance exceeding 98%. A small-mode-area PCF consisting of a subwavelength solid core with nonadiabatic taper, combined with a PBG beam collimator at the air-waveguide exit port, yields over 98% coupling efficiency over a bandwidth of 135nm centered at a wavelength of 1.5μm.