Abstract

We have measured the low frequency (undamped) electrooptic and piezoelectric coefficients in several photorefractive crystals using interferometric techniques. The electrooptic and piezoelectric measurements were independent of the frequency (in the range from 10 Hz to 100 kHz) and linear in the magnitude (in the range from 0.1 to 200 V/cm) of the applied electric field. The electrooptic coefficients measured in melt-grown BaTiO₃ single crystals at λ = 5145 Å and at T = 23°C are r₁₃ = 33 ± 2 pm/V and r₃₃=124 ± 6 pm/V. The piezoelectric coefficient d₁₃ = 57 ± 3 pm/V was measured separately. The combined Pockels coefficient r_C = 84 ± 5 pm/V was measured independently and is in good agreement with the value r_c ≡ r₃₃ − (n₁/n₃)³r₁₃ = 84 ± 5 pm/V computed from the above values of r₁₃ and r₃₃. (n₁, and n₃ are the ordinary and extraordinary indices of refraction, respectively, of tetragonal BaTiO₃.) Similar measurements at λ = 5145 Å in Sr_0.6Ba_0.4Nb₂O₆ single crystals yield the electrooptic coefficients r₁₃ = 55 ± 3 pm/V, r₃₃ = 224 ± 11 pm/V, and the piezoelectric coefficient d₁₃ = 47 ± 3 pm/V. The electrooptic and piezoelectric coefficients of LiNbO₃ single crystals were also measured. As an independent check on this data, we also measured the coupling between two optical beams in these photorefractive crystals. The ratio of the measured coupling strengths for different optical polarizations agrees with theory using the electrooptic coefficients measured above.

© 1986 Optical Society of America