Action of counter-propagating laser beams on two-photon excitation of potassium vapour

Abstract

Abstract.We investigate the emissions of atomic potassium excited by two photons near the 4S1/2-6S1/2 transition. Radiation near the 6S1/2-4P3/2,1/2 and 4P3/2,1/2-4S1/2 transitions are studied for the unidirectional and the bidirectional cases respectively. It is shown that the total output intensity increases considerably for the bidirectional propagation. This is attributed to the effective increase of the Doppler free excitation and the cancellation of the quantum interference effect that is associated with the multiple paths of excitation of certain states.

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

“…For high excitation intensities both emissions evolve according to an ASE process. Finally, the overall response is investigated, when the dephasing collision rate is varied, which is stimulated by existing experimental data [16]. The maximum parameter values used in the numerical model are: laser peak intensity 500 MW=cm 2 , propagation length 10 cm, collision dephasing rate 0.17 cm À1 and atomic density up to 2 Â 10 14 cm À3 , respectively.…”

“…The increase in col reflects the increase in buffer gas pressure p bg as applied in previous experiments [16]. In the present study, we examine the extreme impact of K-He collisions by varying the collision rate, within an order of magnitude, which corresponds to an increase of the buffer gas pressure p bg at approximately 130 mbar (for a given cell volume the analogy col / p bg holds).…”

“…Wellknown nonlinear phenomena, such as partially coherent amplified spontaneous emission (ASE), stimulated hyper Raman scattering (SHRS) and coherent parametric four-wave mixing (PFWM), result from such excitation schemes [2][3][4][5][7][8][9][10][11][12][13][14]. These partially coherent processes appear when the laser is tuned on or off an atomic resonance, giving rise to forward and backward propagating radiations [16]. The coherent axial emission is mostly present when the laser is tuned above an atomic resonance, obeying the axial phase matching relation.…”

“…It is shown that the excitation laser peak intensity, I max , and the elastic collisions with the buffer gas play an important role, for the temporal evolution of the emitted radiations, within the range of atomic densities studied (10 13 cm À3 5 N 5 10 14 cm À3 ). Apart from technical reasons, pertaining to experiments [16], the elastic collisions with the buffer gas should be properly taken into account when attempting to interpret the coherent emission dynamics. In the following we present and interpret the results of our numerical calculations.…”

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

“…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.…”