18 research outputs found
Local polariton modes and resonant tunneling of electromagnetic waves through periodic Bragg multiple quantum well structures
We study analytically defect polariton states in Bragg multiple-quantum-well
structures and defect induced changes in transmission and reflection spectra.
Defect layers can differ from the host layers in three ways: exciton-light
coupling strength, exciton resonance frequency, and inter-well spacing. We show
that a single defect leads to two local polariton modes in the photonic
bandgap. These modes cause peculiarities in reflection and transmission
spectra. Each type of defect can be reproduced experimentally, and we show that
each of these plays a distinct role in the optical properties of the system.
For some defects, we predict a narrow transmission window in the forbidden gap
at the frequency set by parameters of the defect. We obtain analytical
expressions for corresponding local frequencies as well as for reflection and
transmission coefficients. We show that the presence of the defects leads to
resonant tunneling of the electromagnetic waves via local polariton modes
accompanied by resonant enhancement of the field inside the sample, even when a
realistic absorption is taken into account. On the basis of the results
obtained, we make recommendations regarding the experimental observation of the
effects studied in readily available samples.Comment: 17 pages, 10 figures, RevTex, Submitted to PR
Concept of local polaritons and optical properties of mixed polar crystals
The concept of local polaritons is used to describe optical properties of
mixed crystals in the frequency region of their {\it restrahlen} band. It is
shown that this concept allows for a physically transparent explanation of the
presence of weak features in the spectra of so called one-mode crystals, and
for one-two mode behavior. The previous models were able to explain these
features only with the use of many fitting parameters. We show that under
certain conditions new impurity-induced polariton modes may arise within the
{\it restrahlen} of the host crystals, and study their dispersion laws and
density of states. Particularly, we find that the group velocity of these
excitations is proportional to the concentration of the impurities and can be
thousands of times smaller then the speed of light in vacuum.Comment: 21 pages, 5 figures, RevTex, Phys. Rev. B, 62, 6301 (2000
Resonance tunneling of polaritons in 1-D chain with a single defect
We consider propagation of coupled waves (polaritons) formed by a scalar
electromagnetic wave and excitations of a finite one dimensional chain of
dipoles. It is shown that a microscopic defect (an impurity dipole) embedded in
the chain causes resonance tunneling of the electromagnetic wave with the
frequency within the forbidden band between two polariton branches. We
demonstrate that resonance tunneling occurs due to local polariton states
caused by the defect.Comment: 11 pages, 9 figures (PS-format), RevTe
Scaling in One-Dimensional Localized Absorbing Systems
Numerical study of the scaling of transmission fluctuations in the one-dimensional localization problem in the presence of absorption is carried out. Violations of single-parameter scaling for lossy systems are found and explained on the basis of a new criterion for different types of scaling behavior derived by Deych et al
Nanostructured optical waveguide with a highly confined mode
We propose a transmission line working at telecom wavelengths with cross
section as small as , which is 1.6 times smaller than that of
optimized silicon waveguide. The proposed line can be implemented as a
subwavelength fiber with plasmonic cladding. This considerable decrease in the
line cross section is achieved by utilizing a plasmonic quasi-antisymmetric
mode. The required plasmonic cladding is rather thin, therefore, losses are
moderate and could be compensated by using amplifying core materials. Such a
transmission line can find applications in densely integrated optical systems
Local Polariton States in Polar Crystals with Impurities
We show that an impurity embedded in an ionic crystal can give rise to a
novel kind of local states. These states exist within a polariton gap of a
material and are a mix of excitations of the crystal, such as phonons or
excitons, and the transverse electromagnetic field. The electromagnetic
component of the states along with the corresponding excitations of the
material are localized in the vicinity of an impurity.Comment: 9 pages, RevTe
Impurity-induced polaritons in a one-dimensional chain
A detailed analytical study of an impurity induced polariton band arising
inside a spectral gap between lower and upper polariton branches is presented.
Using the microcanonical method, we calculate the density of states and
localization length of the impurity polaritons. Analytical results are compared
with numerical simulations and excellent agreement is found.Comment: 10 pages, 3 figures, RevTe
Optical Spectra and Inhomogeneous Broadening in CdTe/CdZnTe MQW Structures with Defects
Optical spectra of Bragg multiple quantum wells with defects are studied analytically and numerically. It is shown that in systems with relatively strong exciton-photon coupling several different types of spectrum can be observed. The effects due to inhomogeneous exciton broadening are studied using numerical simulations
Optical Spectra and Inhomogeneous Broadening in CdTe/CdZnTe MQW Structures with Defects
Optical spectra of Bragg multiple quantum wells with defects are studied analytically and numerically. It is shown that in systems with relatively strong exciton-photon coupling several different types of spectrum can be observed. The effects due to inhomogeneous exciton broadening are studied using numerical simulations