Infrared, visible and ultraviolet broadband coherent supercontinuum generation in all-normal dispersion fibers
We numerically investigate supercontinuum (SC) generation in fibers with all-normal group velocity dispersion (GVD) under femtosecond pumping, including photonic crystal fibers (PCF), optical nanofibers and suspended core PCF. It is shown that all-normal dispersion (ANDi) fibers are ideally suited to generate extremely flat and more than octave spanning SC spectra which are highly coherent over the entire bandwidth. Due to the suppression of soliton fission in the normal GVD regime, the SC spectra are mainly generated by self-phase modulation and optical wave breaking dynamics, resulting in smooth spectral profiles without significant fine structure. A single pulse is maintained in the time domain, which can be externally compressed to the few-cycle regime. We present specific design examples of ANDi PCF for pumping at 1080 nm and extend the concept to optical nanofibers for deep ultraviolet (UV) SC generation at 400 nm pump wavelength as well as tapered suspended core PCF for visible and near UV SC generation at 465 nm and 530 nm pump wavelength. First "proof of principle" experiments confirm the basic findings of the numerical simulations and show the feasibility of the proposed SC generation scheme. © 2010 SPIE.