Efficiency and phase of optical parametric amplification in chirped quasi-phase-matched gratings

Three-wave nonlinear interactions in chirped quasi-phase-matched (QPM) gratings are shown to exhibit conversion efficiency approaching 100% with increasing input pump and signal intensities, evading backconversion, as long as the idler vanishes at the input and the QPM grating is sufficiently chirped. The signal phase is described in terms of Kerr-like self- and cross-phase modulations, in the cascade χ(3) approximation. Achieving high gain and efficiency simultaneously can lead to a large nonlinear phase, and the resulting trade-off is discussed.