Abstract
A system for measuring the in-plane crystal quality and nonlinear coefficient of a nonlinear optical
crystal using the comparative method of out-of-phase-matched second harmonic generation at a
wavelength of 1555 nm was established. The system based on wedge measurement enables easy sample
preparation, especially for a crystal with a small slope. The system also has a high accuracy for
measuring the ratio between tensor components of the nonlinear coefficient on a crystal surface. In this
study, we first measured LiNbO3 (MgO5mol% doped) to demonstrate the feasibility of our system.
Second, an organic crystal 4-N, N-dimethylamino-4-N-methyl-stilbazolium tosylate (DAST) was
measured. The in-plain crystal quality of the DAST was clearly shown by second harmonics power
mapping. The ratio of d11
DAST/d12
DAST was 6.0. Nonlinear coefficient values of d11
DAST = 296 ± 2 pm/V
and d12
DAST = 49.3 ± 0.3 pm/V were obtained.
