Frequency chirp in optical parametric amplification with large phase mismatch in noncentrosymmetric crystals

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Abstract
We present an analysis of the occurrence of a frequency chirp on picosecond pump and signal pulses as a result of optical parametric amplification with a large phase mismatch in a medium with a large second-order susceptibility. When pump depletion and differences in the group velocity are neglected, a simple analytical formula shows that the signal pulse has a frequency chirp. The sign of the chirp is determined by the sign of Δk. Numerical calculations that account for changes in the pump and differences in the group velocity demonstrate that for higher intensities of the signal and the idler, the pump, the signal, and the idler develop a chirp. In all cases the chirp is large enough to increase the bandwidth of the pulses significantly.