Surface-dressed optical Bloch equations are solved for a two-level atom near or adsorbed on a rough surface, which is modeled as a hemispheroid protrusion on a perfectly conducting surface. Effects of the laser bandwidth are included by means of a phase-diffusion model. The presence of the surface roughness generates a dephasing broadening mechanism on the adatomic resonance fluorescence spectrum, which can be strongly enhanced by plasmon resonances depending on the shape of the hemispheroid. The dependence of the electrodynamics of the adatom on the adatom-hemispheroid distance is also evaluated.
helpful discussions; Melinda W. Certain for assistance in some of our derivations; Kay Kilcoyne and Cathy Ryan for their excellent typing; and Betty Hirschfelder for her critical proofreading.
AppendixExpressions for Exact Density Matrix Elements of Semiclassical Two-Level Systems. The general expression for the density matrix, eq 1.33, can be specialized to the case of a two-level system. Taking the initial condition to be poo(to=O) = 1, and performing some algebraic simplifications, we obtainIn these expressions the summation variables range over all positive and negative integer values, including zero. Note that para = 1 ppp and Im (pag) is not required. It is sometimes convenient to restrict one's attention to the long-time averages of the density matrix elements, defined as Performing this average on eq A1 gives ( P p p ) = I T (a,2klx+)IZ~I(P,21+1 lx+)12 + IC k (~, 2 k 1~-) 1~~1 ( P , 2 1 + 1 Ix-)Iz (A4) while (~~0 ) = 0. We refer to ( p a p ) as the "saturation".The surface-dressed optical Bloch equations for a two-level atom near a metal surface are solved for the case of a strong driving field. An analytic form is obtained for the adatomic resonance fluorescence spectrum. Due to the multiphoton effects of the surface-reflected field and the surface plasmon resonance, the three-peak spectrum is strongly influenced by the surface. A unique surface-induced asymmetry in the side peaks is revealed.
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