Abstract
We present the generation of optical pulses with a spectral range of 500-2400 nm and energies up to 10 µJ at 1 kHz repetition rate by cascaded second-order nonlinear interaction of few-cycle pulses in beta-barium borate (BBO). Numerical simulations with a 1D+time split-step model are performed to explain the experimental findings. The large bandwidth and smooth spectral amplitude of the resulting pulses make them an ideal seed for ultra-broadband optical parametric chirped pulse amplification and an attractive source for spectroscopic applications.
Highlights
Few-cycle light pulses with mJ-scale pulse energies are of high interest to produce isolated attosecond pulses in gases and on surfaces [1, 2]
We present the generation of optical pulses with a spectral range of 500-2400 nm and energies up to 10 μJ at 1 kHz repetition rate by cascaded second-order nonlinear interaction of few-cycle pulses in beta-barium borate (BBO)
The scheme we present in the following was adapted from Fattahi et al [16] who used difference frequency generation (DFG) in BBO to generate pulses in the range of 1000-2500 nm for seeding a short-wavelength infrared (SWIR) optical parametric chirped-pulse amplification (OPCPA) system
Summary
Few-cycle light pulses with mJ-scale pulse energies are of high interest to produce isolated attosecond pulses in gases and on surfaces [1, 2]. Classical laser systems have proved incapable of directly generating or amplifying such pulses due to the lack of broadband gain materials that would allow to enter the few-cycle regime These systems – e.g. Ti:Sapphire systems – are used in combination with nonlinear broadening techniques like hollow core fiber (HCF) compression to overcome this limitation [3]. The Petawatt-Field-Synthesizer (PFS) project that aims for multiJoule pulse energies tries to work around this issue by employing DKDP-crystals which can be grown to very large apertures [10, 11] With these crystals and an Yb:YAG-based pump system [12,13] (frequency-doubled central wavelength of 515 nm) the phase-matchable spectral range for the seed is 700-1400 nm – a rather exotic wavelength band for high-energy OPA systems. In contrast to their setup where the DFG was optimized for maximal energy around 2000 nm and long wavelength components were separated spectrally from the input pulses we took advantage of cascaded nonlinear interactions to produce pulses with an ultra-broad spectrum of 500-2400 nm and separated the output from the input by polarization selection
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