Ultra-low threshold supercontinuum generation in sub-wavelength waveguides.

We show that optical waveguides with sub-wavelength transverse dimensions optimize the effective nonlinearity and provide desireable dispersive properties for generating supercontinuum with ultra-low threshold power. Using a tapered small-core microstructured fiber with a sub-wavelength diameter core, we generate an octave-spanning supercontinuum with 250 pJ pulses from a femtosecond modelocked Ti:sapphire oscillator.