143 research outputs found
Quantum theory of photonic crystal polaritons
We formulate a full quantum mechanical theory of the interaction between
electromagnetic modes in photonic crystal slabs and quantum well excitons
embedded in the photonic structure. We apply the formalism to a high index
dielectric layer with a periodic patterning suspended in air. The strong
coupling between electromagnetic modes lying above the cladding light line and
exciton center of mass eigenfunctions manifests itself with the typical
anticrossing behavior. The resulting band dispersion corresponds to the
quasi-particles coming from the mixing of electromagnetic and material
excitations, which we call photonic crystal polaritons. We compare the results
obtained by using the quantum theory to variable angle reflectance spectra
coming from a scattering matrix approach, and we find very good quantitative
agreement.Comment: Proceedings of the "8th Conference on Optics of Excitons in Confined
Systems" (OECS-8), 15-17 September 2003, Lecce (Italy
Single-Photon Imaging and Efficient Coupling to Single Plasmons
We demonstrate strong coupling of single photons emitted by individual
molecules at cryogenic and ambient conditions to individual nanoparticles. We
provide images obtained both in transmission and reflection, where an
efficiency greater than 55% was achieved in converting incident narrow-band
photons to plasmon-polaritons (plasmons) of a silver nanoparticle. Our work
paves the way to spectroscopy and microscopy of nano-objects with sub-shot
noise beams of light and to triggered generation of single plasmons and
electrons in a well-controlled manner
Plasmon spectra of nanospheres under a tightly focused beam
We study the modification of the far-field cross sections and the near-field
enhancement for gold and silver nanospheres illuminated by a tightly focused
beam. Using a multipole-expansion approach we obtain an analytical solution to
the scattering problem and provide insight on the effects of focusing on the
optical response. Large differences with respect to Mie theory are found
especially when the nanoparticle supports quadrupole or higher-order
resonances.Comment: 19 pages, 7 figure
Light scattering by an oscillating dipole in a focused beam
The interaction between a focused beam and a single classical oscillating
dipole or a two-level system located at the focal spot is investigated. In
particular, the ratio of the scattered to incident power is studied in terms of
the oscillator's scattering cross section and the effective focal area. Debye
diffraction integrals are applied to calculate it and results are reported for
a directional dipolar wave. Multipole expansion of the incident beam is then
considered and the equivalence between this and the Debye diffraction approach
is discussed. Finally, the phase change of the electric field upon the
interaction with a single oscillator is studied.Comment: 9 pages, 6 figure
Lasing at the band edges of plasmonic lattices
We report room temperature lasing in two-dimensional diffractive lattices of
silver and gold plasmon particle arrays embedded in a dye-doped polymer that
acts both as waveguide and gain medium. As compared to conventional dielectric
distributed feedback lasers, a central question is how the underlying band
structure from which lasing emerges is modified by both the much stronger
scattering and the disadvantageous loss of metal. We use spectrally resolved
back-focal plane imaging to measure the wavelength- and angle dependence of
emission below and above threshold, thereby mapping the band structure. We find
that for silver particles, the band structure is strongly modified compared to
dielectric reference DFB lasers, since the strong scattering gives large stop
gaps. In contrast, gold particles scatter weakly and absorb strongly, so that
thresholds are higher, but the band structure is not strongly modified. The
experimental findings are supported by finite element and fourier modal method
calculations of the single particle scattering strength and lattice extinction.Comment: 10 pages, 8 figure
Strong extinction of a laser beam by a single molecule
We present an experiment where a single molecule strongly affects the
amplitude and phase of a laser field emerging from a subwavelength aperture. We
achieve a visibility of -6% in direct and +10% in cross-polarized detection
schemes. Our analysis shows that a close to full extinction should be possible
using near-field excitation.Comment: 5 pages, 4 figures, submitted to PR
Perfect Reflection of Light by an Oscillating Dipole
We show theoretically that a directional dipole wave can be perfectly
reflected by a single point-like oscillating dipole. Furthermore, we find that
in the case of a strongly focused plane wave up to 85 % of the incident light
can be reflected by the dipole. Our results hold for the full spectrum of the
electromagnetic interactions and have immediate implications for achieving
strong coupling between a single propagating photon and a single quantum
emitter.Comment: 3 figure
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