Mid-infrared pulse generation via achromatic quasi-phase-matched OPCPA
  We demonstrate a new regime for mid-infrared optical parametric chirped pulse amplification (OPCPA) based on achromatic quasi-phase-matching. Our mid-infrared OPCPA system is based on collinear aperiodically poled lithium niobate (APPLN) pre-amplifiers and a non-collinear PPLN power amplifier. The idler output has a bandwidth of 800 nm centered at 3.4 $\mu$m. After compression, we obtain a pulse duration of 44.2 fs and a pulse energy of 21.8 $\mu$J at a repetition rate of 50 kHz. We explain the wide applicability of the non-collinear QPM amplification scheme we used, including how it can enable octave-spanning OPCPA in a single device when combined with an aperiodic QPM grating. 
Benedikt W. Mayer, Christopher R. Phillips, Lukas Gallmann and Ursula   Keller
physics.optics