Chirped-pulse supercontinuum generation with a 200-nJ Ti:sapphire oscillator

Merging Ti:sapphire oscillator technology with the so-called long cavity oscillator concept brought significant advances in recent years. The main objective of these development efforts were the energy increase of femtosecond laser pulses directly available from Ti:sapphire oscillators. State-of-the-art lasers of this type deliver 30-60 fs pulses with energies approaching the muJ frontier (Naumov et al., 2005). Shorter durations could not be demonstrated from these lasers since there are some inherent limitations in the chirped pulse oscillator technology that set a boundary to the spectral content of the laser output. On the other hand, some spectroscopic, pump-probe and strong-field-like experiments (Dewald et al., 2006), call for broadening the output spectrum (and eventually pulse compression in many cases). Therefore, extracavity solutions are needed. Nevertheless, this is not a trivial task since single-mode fibres are instantly damaged at these pulse energies, whereas their intensity is not enough to produce significant nonlinearities in hollow fibres or bulk samples. In this work we demonstrate supercontinuum generation in a single-mode fibre with chirped 200 nJ pulses, thus eliminating the damage threshold constraint.