State-selective excitation of potassium atoms by the phase control in the strong field regime

Sugita, Akihiro; Yokoyama, Keiichi  ; Itakura, Ryuji; Yamada, Hidetaka

Selective excitation to the closely lying state of potassiium atoms were examined as a fundamental research of a new laser-isotope-separation technique. Using time-resolved photon counting to measure the fluorescence intensity, the scatterd light from the pump beam and the fluorescence of interest were perfectly distinguished. Owing to this experimental setup, a high contrast more than 1000 was obtained for the selectivity. In addition, the excitation behavior when the laser intensity increased was recorded through the laser power dependence of the fluorescence intensity. As a result, it is found that the destructive interference between two excited states becomes incomplete with increasing laser power. Moreover, the relative population of the two states exhibit the power dependence expected by a computer simulation, indicating that the laser power required for the selective complete excitation is achieved.