REVIEW: Few-optical-cycle pulses tunable from the visible to the mid-infrared by optical parametric amplifiers

Ultrafast optical parametric amplifiers (OPAs) can provide, under suitable conditions, ultra-broad gain bandwidths and can thus be used as effective tools for the generation of widely tunable few-optical-cycle light pulses. In this paper we review recent work on the development of ultra-broadband OPAs and experimentally demonstrate pulses with durations approaching the single-cycle limit and almost continuous tunability from the visible to the mid-IR.