Characterization of QPM gratings in quadratic media via second-harmonic-power measurements only

A new scheme for non-destructive characterization of quasi-phase-matching grating structures and temperature gradients via inverse Fourier theory using second-harmonic-generation experiments is proposed. We show how it is possible to retrieve the relevant information via measuring only the power in the generated second harmonic field, thus avoiding more complicated phase measurements. The potential of the scheme is emphasized through theoretical and numerical investigations in the case of periodically poled lithium niobate bulk crystals.