Abstract
A numerical study of the emissions of a four-level potassium atom excited either by a single pulse or by a pair of temporally separated pulses is presented. For a low-intensity single-pulse two-photon excitation (vertical bar 4S(1/2)> <-> vertical bar 6S(1/2)>), parametric emissions along path-1 (vertical bar 6S(1/2)> <-> vertical bar 5P(3/2)> <-> vertical bar 4S(1/2)>) are generated while along path-2 (vertical bar 6S(1/2)> <-> vertical bar 4P(3/2)> <-> vertical bar 4S(1/2)>) are essentially inactive. But for high single-pulse excitation, the path-1 emissions saturate and delayed path-2 amplified spontaneous emissions appear. It is shown that in the case of a double-pulse excitation scheme, proper temporal separation of the pulses and saturation of path-1 emissions caused by the first pulse can be applied to selectively transfer the excitation energy from path-1 to path-2 emissions.