Competing collinear and noncollinear interactions in chirped quasi-phase-matched optical parametric amplifiers

Chirped quasi-phase-matched optical parametric amplifiers (chirped QPM OPAs) are investigated experimentally. The measured collinear gain is constant over a broad bandwidth, which makes these devices attractive candidates for use in femtosecond amplifier systems. The experiment also shows that chirped QPM OPAs support noncollinear gain-guided modes. These modes can dominate the desired collinear gain and generate in- tense parametric fluorescence. Design guidelines to mitigate these parasitic processes are discussed.