High power mid-IR OPCPA system pumped by a femtosecond Yb-doped fiber amplifier

Abstract

We describe an optical parametric chirped pulse amplifier (OPCPA) architecture built around a state of the art Yb-doped fiber femtosecond pump source delivering 300 fs 400 μ pulses at a repetition rate 125 kHz (50 W average power) and a central wavelength of 1030 nm. The short pump pulse duration compared to bulk Yb:YAG or Nd:YVO4 based systems results in a number of important advantages. First, it allows efficient seeding at 1550 nm using supercontinuum generation directly from the pump pulses in a bulk YAG crystal, resulting in extremely robust passive pump-signal synchronization. The short pump pulse duration also allows the use of millimeter to centimeter lengths of bulk materials to provide stretching and compression for the signal and idler, which minimizes the accumulation of higher-order spectral phase. Finally, the shorter pump pulse duration increases the damage peak intensity, permitting the use of shorter nonlinear crystals to perform the amplification, which increases the spectral bandwidth of the parametric process. Additional experiments are performed to sort out the phenomena that limit power scaling in MgO:PPLN crystals. The OPCPA stages are all operated in collinear geometry, allowing the use of both signal and idler without the introduction of angular chirp on the latter. These points result in the dual generation of 70 fs 23 μJ signal pulses at 1550 nm and 60 fs 10 μJ idler pulses at 3070 nm from a simple setup, with the added benefit of inherent CEP stability of the idler pulses.