Dispersion measurement method with down conversion process

Proper characterization of nonlinear crystals is essential for designing single photon sources. We show a technique for dispersion characterization of a nonlinear material by making use of phase matching in the process of parametric down conversion. Our method is demonstrated on an exemplary periodically poled potassium titanyl phosphate $KTiOPO_4$ crystal phase-matched for $396$ nm to $532$ nm and $1550$ nm. We show a procedure to characterize the dispersion in the range of $390$ to $1800$ nm by means of only one spectrometer for the UV-visible range.