Direct phase matching measurements are a powerful way to characterize the frequency conversion properties of small (submillimeter) crystals of new nonlinear materials. These measurements represent a level of characterization lying between powder tests and detailed refractive index and d coefficient determinations. Since crystals as small as 100um can be studied, a decision to pursue the development of a material can be made at an early stage of crystal growth. Representative data on some new harmonic generators are presented to illustrate various features of the technique.
Stephan P. Velsko,
"Direct Measurements Of Phase Matching Properties In Small Single Crystals Of New Nonlinear Materials," Optical Engineering 28(1), 280176 (1 January 1989). http://dx.doi.org/10.1117/12.7976905