Multi-GHz repetition rate, deep ultraviolet femtosecond source operating in the burst mode

High-repetition-rate ultrafast laser sources at GHz level are of great interest for various applications, such as laser ablation [1] , ultrafast time-domain spectroscopy [2] and electron guns [3] . Electro-optic (EO) frequency combs, in recent years, are becoming more and more attractive as a new kind of GHz-repetition-rate laser sources, due to their cavity-less all-fiber configuration, flexible repetition rate selection and inherently stable spectral line-spacing and carrier-envelope offset frequency. However, relying on commercially available EO modulators and fiber compoments, existing EO combs are mainly at ~1 μm and ~1.5 μm, with few demonstrations of frequency conversion to other spectral regions. Here, we present a two-stage forth-harmonic generation (FHG) of a 11.48 GHz EO comb in the burst mode at 1.03 μm, leading to 294 mW deep ultraviolet (UV) pulses with an estimated pulse duration of sub-300 fs. This source is promising for driving X-band photoinjectors with multi-bunch operation.