Compressible octave-spanning supercontinuum generation by two-color excitation in the group velocity horizon

Micro structured fibers and photonic crystal fibers are an enabling technology, allowing for white-light supercontinuum (SC) generation at the nanojoule pulse energy level available from laser oscillators. While the generation of octave-spanning optical spectra found widespread application in frequency metrology, spectroscopy, optical communications, and medical imaging, one of the most intriguing applications, namely the compression into a coherent single-cycle pulse, remained rather disencouraging to date. The poor spectral coherence generated in the prevalent soliton fission mechanism was identified as the reason for the observed temporal incompressibility of the SC. In the following, a new route for SC generation in micro structured waveguide devices, with efficiencies comparable to that of soliton fission, yet much more favorable coherence properties, was devised. The technique relies on resonant two-color excitation based on the cross-phase modulation (XPM) interaction and borrows from the group-velocity horizon concept. The latter leads to an effective temporal confinement of two pulses and greatly enhances their XPM interaction. This concept has previously been demonstrated to exhibit the possibility for a strong all-optical manipulation of light pulses.