Tunable 31-fs pulse generation in the near ultraviolet range using sum frequency mixing

Summary form only given. Recent progress in parametric conversion made available ultrashort pulses widely tunable in the visible. Extending the spectral range to the ultraviolet is crucial for many applications in time-resolved spectroscopy, e.g., to study small chemically reactive molecules. Ultrashort pulses were obtained close to the harmonics of the Ti:sapphire and CPM laser, but the tunability of these systems is inherently limited. Direct second-harmonic generation (SHG) using pulses generated by an optical parametric amplifier (OPA) was demonstrated to produce 50-fs pulses tunable in the range from 250 nm to 310 nm. We propose to use sum frequency mixing (SFM) with the fundamental of the laser, which has several remarkable advantages: (i) Large pulse energy is available at 800 nm, allowing efficient conversion of the OPA pulses. (ii) SFM provides even more stable pulses than the OPA system itself. This feature is of particular significance for spectroscopic applications. (iii) The tuning range is extended from 300 nm to 360 nm closing the spectral gap between the second and third harmonic of the Ti:sapphire laser.