Electromagnetically induced transparency over spectral hole-burning temperature in an inhomogeneously broadened solid

The electromagnetically induced transparency (EIT) observations at temperatures higher than that needed for the (optical) spectral hole-burning are reported. A 0.05 at. % Pr³⁺-doped yttrium silicate (Pr:YSO) is used as the testing medium. A Λ-type three level system of the Pr:YSO interacting with Raman lasers is analyzed. The absorption coefficient α to approximately 10/cm is calculated for the transmission curve. Both coupling and probe lasers are forward propagating with an angle of approximately 100 mrads. At T = 12 K, the probe transmission is increased by 15%. Considering the optical density and overlap-to-nonoverlap ratio of the laser beams, the transparency inside the medium should be higher by a factor of exp(1.5).