Abstracts Category : Other

Amplitude-modulated optical double resonance

by Leeuwen Michael Van

We have investigated the interaction betweenbichromatic optical fields and atomic transitions. We haveconsidered both the interaction of a saturating bichromatic fieldin the form of a 100% amplitude-modulated field resonantlyinteracting with a single atomic transition as well as theinteraction of a pair of 100% amplitude-modulated fields with twocoupled atomic transitions. </br>In our studies ofa single atomic transition resonantly excited by a 100%amplitude-modulated field we have used a fullyquantum-electrodynamical analysis to model the Autler-Townes effectinduced by a bichromatic optical field. We find that the effectinduced by a bichromatic field is markedly different from theeffect produced by a monochromatic exciting field. We have derivedanalytic expressions for the bichromatic Autler-Townes absorptionspectrum. The absorption spectrum consists of equally spaced linesspaced by the modulation frequency. The linewidths of neighboringlines alternate as functions of the field strength. Experimentally,we observed this spectrum for both resonant and detuned 100%amplitude-modulated driving fields by monitoring the absorption ofa weak monochromatic field as it was tuned about the resonancefrequency of the 3P/(F = 3,mF = 3) 4D/(F =4, mF = 4) transition while driving the3S/(F = 2, mF = 2) 3P/(F = 3, mF =3) transition with a saturating 100% amplitude-modulated field. Wefound excellent agreement between our predicted and measuredspectra. </br>We then investigated the resonantinteraction between a pair of 100% amplitude-modulated fields andtwo atomic transitions sharing a common atomic level. We consideredboth a three-level atomic cascade system and a three-level atomiclambda system. We examined the effect that the relative phasebetween the two modulations has on the rate at which the modulatedfields are absorbed. We find that the saturated time-averaged fieldabsorption exhibits parametric resonances in both the cascade andlambda systems. The time-averaged absorption is strongly dependentupon the relative phase of modulation between the two fields andfor certain phase differences the time-averaged absorption can beenhanced over the maximum saturated absorption experienced by cwfields of the same time-averaged intensities. We also find that thestationary atomic response exhibits periodic oscillations and forthe cascade system periodic two-photon inversions of up to 40% canbe achieved. We further find dark absorption resonances as afunction of phase in the lambda system. We analyze the results fromthe point of view of semi-classical adiabatic dressedstates.