Efficient hyper-Raman scattering in resonant coherent media

We propose and analyze a hyper-Raman scheme for generation of coherent light in a five-level atomic system based on electromagnetically induced transparency (EIT). We show that EIT suppresses linear and nonlinear photon absorption and enables the hyper-Raman process to proceed through real, near-resonant intermediate states. The scheme greatly enhances hyper-Raman efficiency and may be used for generating short-wavelength radiation at low pump intensities.