The effect of nanobodies, i.e., the bodies whose size is small compared to the emission wavelength, on spontaneous emission of an atom located near them is considered. The results of calculations performed within the framework of quantum and classical electrodynamics are presented both in analytic and graphical forms and can be readily used for planning experiments and analysis of experimental data. It is shown that nanobodies can be used to control efficiently the rate of spontaneous transitions. Thus, an excited atom located near a nanocylinder or a nanospheroid pole, whose transition dipole moment is directed normally to the nanobody surface, can decay with the rate that is tens and hundreds times higher than the decay rate in a free space. In the case of some (negative) dielectric constants, the decay rate can increase by a factor of 10 5 —10 6 and more. On the other hand, the decay of an excited atom whose transition dipole moment is directed tangentially to the nanobody surface substantially slows down. The probability of nonradiative decay of the excited state is shown to increase substantially in the presence of na-nobodies possessing losses.
Modification of the resonance fluorescence spectrum of a two-level atom driven by a monochromatic field in the close proximity of a plasmonic nanostructure (metal sphere) is studied in detail. It is shown that one can control this spectrum by varying several key parameters: (i) the radius of the nanosphere, (ii) polarization of the incident radiation, and (iii) the atom's location around the nanosphere (its radial coordinate and polar angle in the spherical coordinate system). These parameters affect the local field enhancement and the modification of the radiative decay rate of the atom interacting with the nanosphere, which leads to modification of the resonance fluorescence spectrum of the atom (e.g., frequency shift of the satellite lines in the Mollow-type triplet, widths of the lines, and the spectrum intensity) by contrast with that in free space. The permittivity of the metal the nanosphere is made of is also an additional parameter, which defines the nonradiative decay. The latter in combination with other parameters allows continuous control of the transition from resonance fluorescence enhancement to its quenching.
The photon-number statistics from resonance fluorescence of a two-level atom near a metal nanosphere driven by a laser field with finite bandwidth is studied theoretically. Our analysis shows that all interesting physics here takes place in a small area around the nanosphere where the near field and the atom-nanosphere coupling essentially affect the radiative properties of the atom. Computer modeling estimates this area roughly as $r\ensuremath{\le}2a$
(r is the distance from the center of the nanosphere to the atom), with
a being the radius of the nanosphere. At the larger distances, the influence of the nanoparticle vanishes and the atom tends to behave similarly to that in free space. It is shown that the distribution function
p(n,T) of the emission probability of
n photons in a given time interval
T in steady-state resonance fluorescence drastically depends on the atom location around the nanosphere for $r\ensuremath{\le}2a$, featuring a characteristic twist in the ridgelike dependence and a convergence time of up to $9\ensuremath{\mu}\text{s}$, two orders of magnitude slower than for the atom in free space. At large distances, the distribution converges to a Gaussian one, as for the atom in free space. The typical convergence time scale at large distances
r>2a tends to the convergence time of the atom in free space. There are also two areas symmetrical around the nanosphere in which $\ensuremath{\Omega}\ensuremath{\sim}\ensuremath{\gamma}$ and the convergence time goes to zero. This behavior is determined by the interplay of the radiative and nonradiative decay rates of the atom due to the coupling with the metal nanosphere and by the near-field intensity. Additional parameters are the normalized laser frequency detuning from the atomic resonance and the bandwidth of the incoming laser field.
Modification of the resonance fluorescence spec-trum of a two-level atom driving by a lasermonochromatic field in the close proximity of aplasmonic nanostructure (metal sphere) is studiedin detail. It is shown that one can control thisspectrum varying four key parameters: distancebetween the atom and the nanosphere, atom’s lo-cation around the nanosphere, the radius of thenanosphere, and polarization of the incident ra-diation. These parameters affect the local fieldenchancement, transition frequency shift and themodification of the radiative decay rate of the atominteracting with the nanosphere, which lead tomodification of the resonance fluorescence spec-trum of the atom (frequency shift of the satellitelines in the Mollow-type triplet, widths of the lines,the spectrum intensity) by contrast with that onein free space. The permittivity of the metal thenanosphere is made of is also an additional param-eter, which defines the nonradiative decay. The lat-ter in combination with other parameters allows tocontinuously control the transition from resonancefluorescence enhancement to its quenching. Thecalculation results are generalized to the case ofN two-level atoms, distributed around the nanopar-ticle in the close proximity of its surface. Thecalculations were performed for different positionsof the detector relative to the system nanoparticle-atom(s).