Ultrashort optical-vortex pulse generation in few-cycle regime.

We generated a 2.3-cycle, 5.9-fs, 56-μJ ultrashort optical-vortex pulse (ranging from ~650 to ~950 nm) in few-cycle regime, by optical parametric amplification. It was performed even by using passive elements (a pair of prisms and chirped mirrors) for chirp compensation. Spectrally-resolved interferograms and intensity profiles showed that the obtained pulses have no spatial or topological-charge dispersion during the amplification process. To the best of our knowledge, it is the first generation of optical-vortex pulses in few-cycle regime. They can be powerful tools for ultrabroadband and/or ultrafast spectroscopy and experiments of high-intensity field physics.