Temporal dynamics of the internally generated radiations in a two-photon excited four-level potassium atom

Abstract

A numerical study, stimulated by existing experimental results concerning the temporal dynamics of internally generated radiations, is presented for a four-level system of the potassium atom. An intense nanosecond duration laser pulse excites the two-photon transition 4S 1=2 $ 6S 1=2 and initiates the generation of internal radiations from quantum noise. It is shown that the temporal profiles of the generated radiations along the atomic path-1,, evolve differently as a function of certain system parameters. It is also shown that the excitation laser intensity affects the parametric emissions along path-1 and the population of the states. The path-2 emissions, which also depend on the excitation laser intensity, are most probably due to amplified spontaneous emission (ASE), without population inversion, in the case of strong excitation. We finally examine the radiation dynamics under the effect of the elastic dephasing collisions between the potassium atoms with the buffer gas atoms.

Control of the emission channels energy flow in a nonlinear laser–potassium atom interaction

“…Additionally, the saturation of the generated emissions of path-1 was observed [23,24], for considerably high laser pulse intensity (∼10 MW cm −2 ) at relatively low atomic density, (N <10 14 cm −3 ). This effect is mostly due to the population transfer to the excited states.…”

“…In some cases the flow of the excitation energy, through the available atomic channels, can be adjusted giving rise to interesting phenomena. Phenomena such as population trapping [2,5,[7][8][9][10], coherently controlled atomic transitions [3,4,11,12] and quantum interference (QI) between available excitation channels and channels of emission [13,[18][19][20][22][23][24][25] have been extensively studied in the past.…”

“…In recent studies [18][19][20][21][22][23][24][25], the nonlinear interaction of a laser pulse with an alkali atom (potassium) was analysed, focusing on the generation of new coherent or partially coherent fields, by wave mixing processes. Coherent parametric four-wave mixing (PFWM), partially coherent stimulated hyper Raman scattering (SHRS) and amplified spontaneous emission (ASE) result from such nonlinear interactions.…”

“…Coherent parametric four-wave mixing (PFWM), partially coherent stimulated hyper Raman scattering (SHRS) and amplified spontaneous emission (ASE) result from such nonlinear interactions. In addition, a destructive QI takes place on the state |6S 1/2 between the resonant two-photon laser excitation and the internally emitted fields [19,[22][23][24][25]. As a result, the emission response on both transitions of path-1 in potassium, |6S 1/2 ↔ |5P 3/2 ↔ |4S 1/2 exhibits a linear dependence on the excitation laser intensity [19].…”