Harmonic Concatenation of 1.5 fs Pulses in the Deep Ultraviolet

Laser pulses with a duration of one femto-second or shorter can be generated both in the visible-infrared (Vis-IR) and in the extreme UV, but the deep UV is a spectral region where such extremely short pulses have not yet been demonstrated. Here, a method for the synthesis of ultrashort pulses in the deep UV is demonstrated, which utilizes the temporal and spatial harmonics that are generated by two noncollinear Vis-IR pulses in a thin MgF2 plate. By controlling the groove-envelope phase of the Vis-IR pulses, spatial harmonics are concatenated to form deep UV waveforms with a duration of 1.5 fs.