Control of surface modes in low loss hollow-core photonic bandgap fibers.

We report on the fabrication and characterization of hollow-core photonic bandgap fibers that do not suffer from surface mode coupling within the photonic bandgap of the cladding. This enables low attenuation over the full spectral width of the bandgap--we measured a minimum loss of 15 dB/km and less than 50 dB/km over 300 nm for a fiber operating at 1550 nm. As a result of the increased bandwidth, the fiber has reduced dispersion and dispersion slope--by a factor of almost 2 compared to previous fibers. These features are important for several applications in high-power ultrashort pulse compression and delivery. Realizing these advances has been possible due to development of a modified fabrication process which makes the production of low-loss hollow-core fibers both simpler and quicker than previously.