Abstract
The nonlinear interaction of a four-level potassium system with a strong pump and a weak coupling laser is investigated. A strong pump pulse excites the two-photon transition
, causing prompt parametric emissions along the path-1
and delayed emissions in the second available de-excitation path-2
. A weak coupling pulse is introduced to coherently excite either the transition
(path-1) or the
one (path-2) in a V-type scheme. Results are presented for the emissions generated under the combined action of the pump-coupling pulses as a function of their delay for certain peak pulse intensities and coherence relaxation times (CRTs) related to dephasing collisions. We find that emissions in path-1 are considerably enhanced for negative delays (counterintuitive pulse sequence) of the order of the CRT. An approach is suggested for the estimation of CRTs. Emissions in path-2 are enhanced and temporally shifted, suggesting an approach to control this path by varying the pulse delay.