Physical Review A
Sum-frequency generation using strong-field coupling and induced transparency in atomic hydrogen
G. Z. Zhang, M. Katsuragawa, K. Hakuta, R. I. Thompson, Boris Peter Stoicheff
Abstract
The sum-frequency generation process using strong-field coupling and quantum interference is described systematically using atomic hydrogen both in theory and experiment. It is shown that strong coupling at the 3p-2s transition creates destructive interference to reduce the linear susceptibility at the resonant 3p\ensuremath{\leftarrow}1s transition. Simultaneously, two-photon coupling of the 2s and 1s states produces constructive interference to resonantly enhance the nonlinear susceptibility for sum-frequency generation at the 3p\ensuremath{\rightarrow}1s (Lyman-\ensuremath{\beta}) transition. Experimental results clearly demonstrate the theoretical predictions. When the Rabi frequency for the 3p-2s coupling exceeds the Doppler tail of the medium, the photoion signals on resonance are suppressed significantly because of induced transparency. The generated Lyman-\ensuremath{\beta} radiation grows rapidly by a factor of 250 at an atom density of ${10}^{15}$ ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$ and interaction length of 3.5 cm, resulting in a conversion efficiency of 2\ifmmode\times\else\texttimes\fi{}${10}^{\mathrm{\ensuremath{-}}4}$.