Harmonic Concatenation of 1.5-Femtosecond-Pulses in the Deep UV

Waveforms with durations short enough to probe the electronic timescale can be generated both in the extreme UV and in the IR-VIS region of the electromagnetic spectrum [1]. In the deep UV (DUV), where for example many basic aromatic molecules absorb radiation and undergo photochemical reactions [2], pulses with such extremely short durations have not yet been demonstrated. A fundamental difficulty is rooted in the large group velocity dispersion of any optical component in the DUV, causing a DUV pulse to be readily broadened and distorted before it reaches the sample. The present record for the shortest DUV pulses is 2.8 fs [3].