Abstract

Many research fields have benefited tremendously from the ever lasting development of ultrashort pulses, especially nonlinear spectroscopy [1] which aims at investigating femtosecond scale dynamics of molecular motion. Of particular interest is the availability of coherent light and ultrashort pulses across large wavelength ranges, ideally spanning several octaves from the UV to the mid-IR. The limited wavelength range and bandwidths of optical gain media requires, for ultrabroadband spectra, some form of continuum generation. Spectra broadened in highly nonlinear fibers, in particular photonic crystal fibers (PCFs), can span from the visible to mid-IR [2], although with a low spectral energy density (sub-pJ/nm). Using amplified visible pulses in bulk matter obviates this issue, however in order to achieve sufficient broadening, especially to to the longer wavelength side, often requires excessive pulse energy [3] or is not possible. Whilst this is partly a consequence of the reduced confinement of the unguided pulse, material dispersion is also crucial. Initiating spectral broadening in the normal dispersion regime is known to inhibit the onset of soliton dynamics and therefore also supercontinuum generation. This motivates initiating supercontinuum above the zero-dispersion wavelength of bulk materials by pumping in the anomalous dispersion regime.

© 2011 IEEE