Supercontinuum in silica nanowires

Fibers are gaining widespread acceptance for generating ultra-broad spectra. The most common approach involves a photonic crystal fiber with carefully designed core size and dispersion characteristics. Although this system provides confinement of light to micrometer (and sometimes sub-micrometer) dimensions, this confinement is achieved at the expense of a complex core structure. An alternative to microstructured fibers is the use of silica fibers with sub-wavelength diameters whose waveguiding properties were initially demonstrated by our group. Silica nanowires are a model system because they are a step-index, all-core cylindrical waveguide, and therefore easily modeled. The nanowires have applications in integrated photonics and sensing. We present recent results for supercontinuum generation using femtosecond laser pulses in nanowires of various diameters and lengths. We observe supercontinuum generation in over interaction lengths as short as 10 mm. The evolution of the spectra is examined with respect to self-phase modulation and solition self-splitting. We will discuss the nonlinear effects and the resulting spectra as a function of the dispersion characteristics for the fibers and of the input laser power.