122 research outputs found
Pliable Polaritons: Wannier Exciton Plasmon Coupling in Metal Semiconductor Structures
Plasmonic structures are known to support the modes with subwavelength
volumes in which the field matter interactions are greatly enhanced. Coupling
between the molecular excitations and plasmons leading to formation of
plexcitons has been investigated for a number of organic molecules. However,
plasmon-exciton coupling in metal semiconductor structures have not experienced
the same degree of attention. In this work we show that the very strong
coupling regime in which the Rabi energy exceeds the exciton binding energy is
attainable in semiconductor cladded plasmonic nanoparticles and leads to
formation of Wannier Exciton Plasmon Polariton (WEPP) that is bound to the
metal nanoparticle and characterized by dramatically smaller (by factor of few)
excitonic radius and correspondingly higher ionization energy. This higher
ionization energy exceeding approaching 100meV for the CdS/Ag structures may
make room temperature Bose Einstein condensation and polariton lasing in
plasmonic/semiconductor structures possibl
Photonic Time Crystals and Parametric Amplification: similarity and distinction
Photonic Time crystals (PTC) arise in time-modulated media when the frequency
of modulation of permittivity is on the order of twice the frequency of light
and are manifested by the generation and amplification of so-called time
reversed waves propagating in the direction opposite to the incoming light.
Superficially, the observed phenomenon bears resemblance to the widely known
phenomena of optical parametric generation (OPG) and amplification (OPA) using
second or third order optical nonlinearities. I show that while indeed the same
physical mechanism underpins both PTC and OPA , the difference arises from the
boundary conditions. Thus , while dispersion for both PTC and OPA exhibit the
same bandgap in momentum space, only in the case of PTC can one have
propagation in that bandgap with exponential amplification. I also show that
PTC can be engineered with both second and third order nonlinearities, and that
rather unexpectedly, modulating permittivity on the ultrafast (few fs) rate is
not a necessity, and that one can emulate all the PTC features using materials
with a few picoseconds response time commensurate with the propagation time
through the medium
Nonlinear Optics: a look from the interaction time viewpoint and what it portends
I present a simple view of nonlinear optcal phenomena as being determined
mostly by the length of interaction time between photons and matter. This may
explain why in the last decades the progress in developing better nonlinear
materials has not been as rapid as wished. A few tentative routes towards
possible improvements in the efficiency of nonlinear optical phenomena are
suggested
Optical isolation by temporal modulation: size, frequency, and power constraints
Optical isolators are indispensable components of optical networks.
Magneto-optic isolators have excellent operating characteristics, including
low-to-no power consumption, but are not well suited for on-chip integration.
The technique of temporal modulation of dielectric constant offers an
alternative way to achieve isolation without magnetic field but is not without
its own drawbacks. In this work I examine diverse methods of optical isolation
via temporal modulation and show that independent on whether modulation is
achieved by carrier injection, Pockels and acousto-optic effects, or any other
conceivable method, there is essentially the same set of constraints on
footprint, modulation frequency, and, most important, on power consumption
required to achieve full isolation without excessive insertion loss. This power
is estimated to be on the order of at least a hundred of milliwatts and whether
this requirement is acceptable will depend on ongoing progress of both
magneto-optic and time modulated integrated technologies
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