Wavelength dependence of two‐beam coupling gain coefficients of BaTiO3:Ce crystals

Two‐beam coupling gain coefficients of transmission and reflection gratings in BaTiO3:Ce crystals versus wavelength between 570 and 680 nm have been measured. The former decreases more quickly than predicted by theory. The latter was found to vary significantly with wavelength, while theory shows that it should vary little. In order to explain the experimental results we assumed that the effective carrier number density Neff depends on wavelength. By calculating Neff from the measured results we found that Neff is approximately a linearly decreasing function of wavelength. The slopes and intercepts for the linear functions are given for the two crystals studied.