Electromagnetically induced transparency (EIT) in atomic hydrogen: realization of high conversion efficiency for nonlinear optical generation

Sum-frequency generation with electromagnetically induced transparency is investigated experimentally as the generation of coherent Lyman-(Beta) radiation (103 nm) in atomic hydrogen. We demonstrate that with the application of a strong laser field to couple the 2 s and 3 p levels, the resonant Lyman-(Beta) transition becomes transparent, and the generated wave continues to grow without suffering resonant absorption. At a density-length product NL of 3 X 1015 cm-2, a conversion efficiency of 2 X 10-4 is obtained for the coherent 103 nm radiation.