Papers by Alexander Lisyansky
An active one-dimensional Fibonacci photonic quasi-crystal is realized via spin coating. Luminesc... more An active one-dimensional Fibonacci photonic quasi-crystal is realized via spin coating. Luminescence properties of an organic dye embedded in the quasi-crystal are studied experimentally and compared to theoretical simulations. The luminescence occurs via the pseudo-bandedge mode and follows the dispersion properties of the Fibonacci crystal. Time resolved luminescence measurement of the active structure shows faster spontaneous emission rate, indicating the effect of the large photon densities available at the bandedge due to the presence of critically localized states. The experimental results are in good agreement with the theoretical calculations for steady-state luminescence spectra.
We propose a new model for the quantum-confined Stark effect describing the behavior of quantum w... more We propose a new model for the quantum-confined Stark effect describing the behavior of quantum well exciton in the electric field parallel to the direction of the structure's growth. For the case of the narrow well this model gives a better description of the effect than does the infinite-well approximation. The simplicity of the model allows one to advance further
Compositional disorder and interface roughness are two main contributions to the inhomogeneous br... more Compositional disorder and interface roughness are two main contributions to the inhomogeneous broadening of exciton spectra in quantum wells (QW). In the presence of disorder, the center-of-mass motion of the exciton in a QW structure is determined by the Schrödinger equation with the random effective potential. The variance of this effective potential,sigma ^2= , is an important characteristic determining the
Phys Rev B, 1996
We derive the off-shell scattering matrix for a spherical scatterer. The result obtained generali... more We derive the off-shell scattering matrix for a spherical scatterer. The result obtained generalizes the off-on-shell matrix commonly used in the theory of scalar waves propagation in random media.
The variance of the Lyapunov exponent is calculated exactly in the one-dimensional Anderson model... more The variance of the Lyapunov exponent is calculated exactly in the one-dimensional Anderson model with random site energies distributed according to the Cauchy distribution. We derive an exact analytical criterion for the validity of the single parameter scaling in this model. According to this criterion, states with energies from the conduction band of the underlying non-random system satisfy single parameter scaling when disorder is small enough. At the same time, single parameter scaling is not valid for states close to band boundaries and those outside of the original spectrum even in the case of small disorder. The obtained results are applied to the Kronig-Penney model with the potential in the form of periodically positioned $\delta$-functions with random strengths. We show that an increase in the disorder can restore single parameter scalingbehavior for states from band-gaps of this model.
Proceedings of SPIE - The International Society for Optical Engineering
ABSTRACT
It is shown that it is possible to significantly modify optical spectra of Bragg multiple quantum... more It is shown that it is possible to significantly modify optical spectra of Bragg multiple quantum well structures by introducing wells with different exciton energies. The reflection spectrum of the resulting structures is characterized by high contrast and tuning possibilities.
OMB No. 074-0188 -PubliL.uLporting burden for this collection of information is estimated to aver... more OMB No. 074-0188 -PubliL.uLporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302, and to the Office of Management and Budget, Paperwork Reduction Project (0704-0188), Washington, DC 20503
Physical Review B, 2000
The structure of polariton spectrum is analyzed for periodic multiple quantum well structures wit... more The structure of polariton spectrum is analyzed for periodic multiple quantum well structures with periods at or close to Bragg resonance condition at the wavelength of the exciton resonance. The results obtained used to discuss recent reflection and luminescent experiments by M. Hübner et al [Phys. Rev. Lett. 83, 2841] carried out with long multiple quantum well structures. It is argued that the discussion of quantum well structures with large number of wells is more appropriate in terms of normal modes of infinite periodic structures rather then in terms of superand sub-radiant modes.
We consider propagation of coupled waves (polaritons) formed by a scalar electromagnetic wave and... more 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
In Bragg multiple quantum well (MQW) structures, where the period is equal to the half wavelength... more In Bragg multiple quantum well (MQW) structures, where the period is equal to the half wavelength of the exciton emission line, an enhanced interaction between light and excitons gives rise to a broad photonic stop band. Introducing a defect (a well with characteristics different from those of the host QW) into such a structure, one can significantly modify its optical spectra. In this talk we consider a defect QW, which exciton frequency is different from the frequency of host QWs. We study how inhomogeneous broadening of QW excitons affects the characteristics of the transmission resonance induced by such a defect. We show that the resonance is mostly controlled by the susceptibility of the defect well, while homogeneous and inhomogeneous broadenings of the host QWs do not affect the resonance even for very large values of the respective widths. It is also interesting that inhomogeneous and homogeneous widths of the excitons in the defect well influence the shape of the transmissi...
physica status solidi (c)
tunneling of electromagnetic waves through polariton gaps
International Journal of Modern Physics B, 1999
Within the framework of an exactly solvable model, which takes into account the interaction of fl... more Within the framework of an exactly solvable model, which takes into account the interaction of fluctuating modes with equal and opposite momenta, we consider phase diagrams in systems with coupled scalar order parameters. We show that, in agreement with the renormalization group theory, the fluctuation interaction can split the continuous disorder-order transition into two phase transitions of the first order. Moreover, the transition may occur into the anomalous, from the mean field theory point of view phase. The effect disappears when the fluctuation interaction is suppressed.
Physical Review B, 2004
The reflection spectrum of a multiple quantum well structure with an inserted defect well is cons... more The reflection spectrum of a multiple quantum well structure with an inserted defect well is considered. The defect is characterized by the exciton frequency different from that of the host's wells. It is shown that for relatively short structures, the defect produces significant modifications of the reflection spectrum, which can be useful for optoelectronic applications. Inhomogeneous broadening is shown to affect the spectrum in a non-trivial way, which cannot be described by the standard linear dispersion theory. A method of measuring parameters of both homogeneous and inhomogeneous broadenings of the defect well from a single CW reflection spectrum is suggested.
Physical Review E, 1997
In order to study an influence of correlations on the localization properties of classical waves ... more In order to study an influence of correlations on the localization properties of classical waves in random superlattices we introduce a generalized random Thue-Morse model as a four-state Markov process with two parameters that determine probabilities of different configurations. It is shown that correlations can bring about a considerable change in the transmission properties of the structures and in the localization characteristics of states at different frequencies.
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Papers by Alexander Lisyansky