Spontaneous emission rate of an excited atom placed near a nanofiber

Abstract

The spontaneous decay rates of an excited atom placed near a dielectric cylinder are investigated. A special attention is paid to the case when the cylinder radius is small in comparison with radiation wavelength (nanofiber or photonic wire). In this case, the analytical expressions of the transition rates for different orientations of dipole are derived. It is shown that the main contribution to decay rates is due to quasistatic interaction of atom dipole momentum with nanofiber and the contributions of guided modes are exponentially small. On the contrary, in the case when the radius of fiber is only slightly less than radiation wavelength, the influence of guided modes can be substantial. The results obtained are compared with the case of dielectric nanospheroid and ideally conducting wire.

Purcell factor for a point-like dipolar emitter coupled to a two-dimensional plasmonic waveguide

“…3b) our numerical simulation with quasi-static approximation derived in Ref. [5,24] for the nanowire. The quasi-static approximation underestimates the radiative contribution to the coupling rate since it only considers the cylindrical dipole mode.…”

Spontaneous emission of an atom placed near a nanobelt of elliptical cross section

“…The analogous process is also observed in the case of a circular nanocylinder (dotted line in Fig.10, Eq.(37)). Figure 11 illustrates a comparison for the rate of spontaneous decay (16) obtained by numerical integration (34) and an asymptotic expression (35) for the atom with the normally oriented dipole moment in close proximity to the surface (u ′ = u 0 ) of perfectly conducting cylinder. As it seen, the asymptotic expression agrees well with the numerical data up to ka = 1.…”

“…Note that the expressions (41) and (42) in case of circular nanocylinder (a = b) are significantly simplified and take the well known form [35] …”

“…It should be noted that beside the radiative and nonradiative chanels of the spontaneous decay for a dielectric cylinder (and for any dielectric waveguided structure) one must take into account energy transfer into the waveguided modes. In case of the dielectric (nonmetallic) nanobodies that correction is exponentially small [35] and may be neglected. But in case of the complex dielectric permittivity of a nanocylinder (real metals), the spontaneous decay waveguiding rate may be no longer a small value, and that correction should be taken into account.…”

“…It is a complex problem to determine directly the radiative losses described by the 3-d order terms by k. But in the case of an atom localized close to a nanobody the radiation is dipole-like, and the total dipole moment of the atom + nanobody system could be found from G (0) αβ (r,r ′ ) at large distances from the system. Thus, in the case of the nanobodies the radiative rate of the spontaneous transition (the transition from e into g) will be described by [35]:…”