SUM-FREQUENCY GENERATION USING STRONG-FIELD COUPLING AND INDUCED TRANSPARENCY IN ATOMIC-HYDROGEN

The sum-frequency generation process using strong-field coupling and q uantum 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 linea r susceptibility at the resonant 3p<--1s transition. Simultaneously, t wo-photon coupling of the 2s and 1s states produces constructive inter ference to resonantly enhance the nonlinear susceptibility for sum-fre quency generation at the 3p-->1s (Lyman-beta) transition. Experimental results clearly demonstrate the theoretical predictions. When the Rab i frequency for the 3p-2s coupling exceeds the Doppler tail of the med ium, the photoion signals on resonance are suppressed significantly be cause of induced transparency. The generated Lyman-beta radiation grow s rapidly by a factor of 250 at an atom density of 10(15) cm(-3) and i nteraction length of 3.5 cm, resulting in a conversion efficiency of 2 X 10(-4).