46 research outputs found
Polariton Local States in Periodic Bragg Multiple Quantum Well Structures
We analytically study optical properties of several types of defects in Bragg
multiple quantum well structures. We show that a single defect leads to two
local polariton modes in the photonic band gap. These modes lead to
peculiarities in reflection and transmission spectra. Detailed recommendations
for experimental observation of the studied effects are given.Comment: 3 pages, 1 figure, RevTex, Submitted to Opt. Let
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
Single parameter scaling in 1-D localized absorbing systems
Numerical study of the scaling of transmission fluctuations in the 1-D
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 [Phys. Rev. Lett., {\bf 84}, 2678 (2000)].Comment: 7 pages, 6 figures, RevTex, submitted to Phys. Rev.
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
Statistical properties of one-dimensional random lasers
Statistical properties of a laser based on a one-dimensional disordered
superlattice open at one side are studied numerically. The passive normal modes
of the system are determined using the Feshbach projection technique. It is
found that the mode competition due to the spacial hole burning leads to a
saturation of the number of lasing modes with increasing pump rate. It is also
responsible for nonmonotonic dependence of intensities of lasing modes as
functions of pumping. Computed distributions of spectral spacing and intensity
statistics are in qualitative agreement with experimental results.Comment: 4 pages (v2: minor corrections, published version
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