Broadband photorefractive properties and self-pumped phase conjugation in Ce-SBN:60

The first use of cerium-doped Sr
0.6
Ba
0.4
Nb
2
O
6
as a broadband self-pumped phase-conjugate mirror using internal reflection is reported. The phase-conjugate reflectivity at normal incidence ranged from two percent at 442 nm to seven percent at 515 nm and was zero at 633 nm. The electron-hole competition was found to be significant and had a wavelength dependence in one sample but not the other. The charge carrier density was
\sim 7 \times 10^{16}
cm
^-3
and was wavelength in-dependent. The absorption coefficient ranged from 2 cm
^-1
at the shorter the wavelengths to zero at longer wavelengths. The dispersion in the indexes of refraction was measured and the birefringence was -0.036. The sign of the dominant charge carriers was determined to be negative and the sign of the electrooptic coefficient, r
33
, was positive. Using the above values, a wavelength dependent coupling coefficient has been determined. The experimental results indicate that the phaseconjugate reflectivity decreases at shorter wavelengths due to increased absorptive losses and experiences a threshold effect at longer wavelengths.