Spectral enhancement in optical parametric amplifiers in the saturated regime - Bigourd, D; Patankar, S; Robbie, SIO; Doyle, HW; Mecseki, K; Stuart, N; Hadjicosti, K; Leblanc, N; New, GHC; Smith, RA (APPLIED PHYSICS B-LASERS AND OPTICS, 2013)