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

Summary form only given. When a resonant Raman laser field interacts with a three-level energy system, the system can undergo changes of linear and nonlinear optical properties. Especially in an optically thick medium, a strong resonant electromagnetic field can dress the energy states so that another resonant probe field may not be absorbed. This is due to destructive quantum interference between two absorption paths from the ground state to the dressed states. This phenomenon is called electromagnetically induced transparency. Our recently demonstrated Raman excited spin echo technique uses optically induced spin coherence. In general, the spin coherence decay time is much longer and more temperature insensitive than the optical coherence, so that the temperature limitation of the photon echoes can be overcome. The spin echoes are read by another optical field via enhanced four-wave mixing. Here, the nonlinearity in the optical transition is enhanced by EIT. In this paper we report the EIT observation at temperatures higher than that needed for the (optical) spectral hole-burning.