Noncollinear phase-matching geometries in ultra-broadband quasi-parametric amplification

Optical parametric chirped pulse amplification(OPCPA)shows great potential in producing ultrashort high-intensity pulses because of its large gain bandwidth.Quasi-parametric chirped pulse amplification(QPCPA)may further extend the bandwidth.However,behavior of QPCPA at a limited pump intensity(e.g.,≤5 GW/cm^(2) in a nanosecond pumped QPCPA)has not yet been investigated fully.We discuss detailedly the ultra-broadband amplification and the noncollinear phasematching geometry in QPCPA,model and develop a novel noncollinear geometry in QPCPA,namely triple-wavelength phase-matching geometry,which provides two additional phase-matching points around the phase-matching point at the central wavelength.Our analysis demonstrates that the triple-wavelength phase-matching geometry can support stable,ultra-broadband amplification in QPCPA.The numerical simulation results show that ultrashort pulse with a pulse duration of 7.92 fs can be achieved in QPCPA when the pump intensity is limited to 5 GW/cm^(2),calculated using the nonlinear coefficient of YCa;O(BO;);.

Optical modification of nonlinear crystals for quasi-parametric chirped-pulse amplification

Quasi-parametric chirped-pulse amplification(QPCPA),which features a theoretical peak power much higher than those obtained with Ti:sapphire laser or optical parametric chirped-pulse amplification,is promising for future ultra-intense lasers.The doped rare-earth ion used for idler dissipation is critical for effective QPCPA,but is usually not compatible with traditional crystals.Thus far,only one dissipative crystal of Sm^(3+)-doped yttrium calcium oxyborate has been grown and applied.Here we introduce optical means to modify traditional crystals for QPCPA applications.We theoretically demonstrate two dissipation schemes by idler frequency doubling and sum-frequency generation with an additional laser.In contrast to absorption dissipation,the proposed nonlinear dissipations ensure not only high signal efficiency but also high small-signal gain.The demonstrated ability to optically modify crystals will facilitate the wide application of QPCPA.

Numerical study of spatial chirp distortion in quasi-parametric chirped-pulse amplification

Optical parametric chirped-pulse amplification is inevitably subject to high-order spatial chirp,particularly under the condition of saturated amplification and a Gaussian pump;this corresponds to an irreversible spatiotemporal distortion and consequently degrades the maximum attainable focused intensity.In this paper,we reveal that such spatial chirp distortion can be significantly mitigated in quasi-parametric chirped-pulse amplification(QPCPA)with idler absorption.Simulation results show that the quality of focused intensity in saturated QPCPA is nearly ideal,with a spatiotemporal Strehl ratio higher than 0.98.As the seed bandwidth increases,the idler absorption spectrum may not be uniform,but the Strehl ratio in QPCPA can be still high enough due to stronger idler absorption.