Mismatch characteristics of optical parametric chirped pulse amplification

Abstract

The stability of an optical parametric chirped pulse amplifier (OPCPA) is influenced by time and the angular matching of the input beams. We derived the Gaussian dependence of the monochromatic signal gain on the small mismatch between the signal and pump beams. Gain characteristics were also calculated for polychromatic amplification and the impact of different beam mismatches and interaction geometries was explained. The asymmetry of the energy gain, and the square root dependence of the phase matched wavelength on beam angles were found. The predicted dependences were verified in a noncollinear OPCPA system with LBO and KDP crystal amplifying pulses of a Ti:sapphire laser around a central wavelength of 800 nm, pumped by the third harmonic frequency of an iodine gas laser at a wavelength of 438 nm. The widths of the gain curves in the dependence on both the pump-signal or the phase matching angles varied from several tenths to a few milliradians. The gain curve widths dependent on the pump-signal pulse delay were about two thirds of the pump pulse width for moderate pumping and about a half of the pump pulse width for pumping on the order of GW cm −2 . A stable gain output is achieved if angular and temporal fluctuations are fractions of the measured gain curve widths, and when the signal direction is between the pump and the crystal principal axis (i.e. in the psz geometry).

Numerical Simulations of Transfer of Spatial Beam Aberrations in Optical Parametric Chirped-Pulse Amplification

“…Several articles have considered beam quality in OPCPA systems [26,27], mainly by examining the influences of the pump beam-profile and dephasing on OPA gain and signal beam quality. A theoretical model was developed for dephasing effects due to angular deviation from ideal phase matching, and the impact of the angular content of 2 Advances in Condensed Matter Physics the beam on small signal gain and conversion efficiency in a strongly depleted regime was evaluated numerically [26].…”