Generation of high-energy broadband femtosecond deep-ultraviolet pulses by highly nondegenerate noncollinear four-wave mixing in a thin transparent solid

We present a simple and efficient technique for the generation of ultrashort deep-ultraviolet pulses based on four-wave mixing of noncollinear laser pulses in a thin solid. Sub-30-fs pulses (Fourier-limit of 13 fs) centered at 270 nm, with energies up to 6 μJ, were obtained by mixing the fundamental and the second harmonic of a Ti:sapphire amplifier in fused silica. Temporal characterization was performed with a dispersionless self-diffraction FROG setup. Spectra as broad as 20 nm were also obtained that can in principle support sub-4-fs deep-ultraviolet pulses.The results are well described by two-dimensional numerical simulations.