Optical characterization of periodically-poled KTiOPO4.
We demonstrate how the Maker fringes that are observable in spontaneous parametric down-conversion (SPDC) give a direct visualization of the poling quality of a periodically-poled crystal. Identical Maker fringes are observed in the optical spectrum of collinear SPDC and the temperature dependence of second harmonic generation. We analyze these Maker fringes via a unified treatment of the tuning curve in crystals with small and slowly-varying deformations of the poling structure. Our theoretical model, based on a Fourier analysis of the poling deformations, distinguishes between duty-cycle variations and variations of the poling phase. The analysis indicates that the poling phase is approximately fixed, while the duty-cycle typically varies between 36% and 64%.
Huygens Laboratory, Leiden University, P.O. Box 9504, 2300 RA Leiden, The Netherlands. peeters@molphys.leidenuniv.nl
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