72 research outputs found
Multipole interaction between atoms and their photonic environment
Macroscopic field quantization is presented for a nondispersive photonic
dielectric environment, both in the absence and presence of guest atoms.
Starting with a minimal-coupling Lagrangian, a careful look at functional
derivatives shows how to obtain Maxwell's equations before and after choosing a
suitable gauge. A Hamiltonian is derived with a multipolar interaction between
the guest atoms and the electromagnetic field. Canonical variables and fields
are determined and in particular the field canonically conjugate to the vector
potential is identified by functional differentiation as minus the full
displacement field. An important result is that inside the dielectric a dipole
couples to a field that is neither the (transverse) electric nor the
macroscopic displacement field. The dielectric function is different from the
bulk dielectric function at the position of the dipole, so that local-field
effects must be taken into account.Comment: 17 pages, to be published in Physical Review
Angular redistribution of near-infrared emission from quantum dots in 3D photonic crystals
We study the angle-resolved spontaneous emission of near-infrared light
sources in 3D photonic crystals over a wavelength range from 1200 to 1550 nm.
To this end PbSe quantum dots are used as light sources inside titania inverse
opal photonic crystals. Strong deviations from the Lambertian emission profile
are observed. An attenuation of 60 % is observed in the angle dependent radiant
flux emitted from the samples due to photonic stop bands. At angles that
correspond to the edges of the stop band the emitted flux is increased by up to
34 %. This increase is explained by the redistribution of Bragg-diffracted
light over the available escape angles. The results are quantitatively
explained by an expanded escape-function model. This model is based on
diffusion theory and adapted to photonic crystals using band structure
calculations. Our results are the first angular redistributions and escape
functions measured at near-infrared, including telecom, wavelengths. In
addition, this is the first time for this model to be applied to describe
emission from samples that are optically thick for the excitation light and
relatively thin for the photoluminesence light.Comment: 24 pages, 8 figures (current format = single column, double spaced
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