Organic electroluminescent devices and their application

Several organic electroluminescent devices have been fabricated by multi-source high vacuum deposition system. For high brightness organic electroluminescent device, the maximum brightness is over 40000 cd/m². For quantum well structures, quantum size effect has been investigated and the high light emission efficiencies of the devices have been obtained. White-light emission from organic multi-quantum well structures is proposed at first. Brightness of the white-light MQW devices reaches 4000 cd/m² at 17 V. Presented at the 1st Czech-Chinese Workshop “Advanced Materials for Optoelectronics”, Prague, Czech Republic, June 13–17, 1998. The research is supported by the National “863” Project of China [No. 863-307-05-05(02)] and by the National Natural Science Foundation of China [No. 69637010].     

Complete Axiomatizations for Quantum Actions

We present two equivalent axiomatizations for a logic of quantum actions: one in terms of quantum transition systems, and the other in terms of quantum dynamic algebras. The main contribution of the paper is conceptual, offering a new view of quantum structures in terms of their underlying logical dynamics. We also prove Representation Theorems, showing these axiomatizations to be complete with respect to the natural Hilbert-space semantics. The advantages of this setting are many: (1) it provides a clear and intuitive dynamic-operational meaning to key postulates (e.g. Orthomodularity, Covering Law); (2) it reduces the complexity of the Solèr–Mayet axiomatization by replacing some of their key higher-order concepts (e.g. “automorphisms of the ortholattice”) by first-order objects (“actions”) in our structure; (3) it provides a link between traditional quantum logic and the needs of quantum computation. PACS: 02.10.-v Logic; set theory and algebra; 03.65.-w Quantum mechanics; 03.65.Fd Algebraic methods; 03.67.-a Quantum information.     

Magnetoexciton light absorption in inhomogeneous quasi-two-dimensional systems

The problem of exciton light absorption in quasi-two-dimensional inhomogeneous systems in a strong transverse magnetic field H is analyzed. We assume that a random Gaussian field (“white noise”) acting separately on an electron and a hole is due to (1) fluctuations in the quantum well thickness or (2) fluctuations in the concentrations of the solid solution components. The problem of a magnetoexciton in a random Gaussian white noise field has been reduced to the problem of the motion in an H-dependent effective field of a single particle with the effective magnetic mass of the exciton, which is a function of the magnetic field and parameters of the quantum wells, in a field characterized by “colored noise,” whose correlation function is different from that of the white noise field. In this approximation, the problem of a magnetoexciton in isolated and coupled quantum dots is considered. In the coherent-potential approximation, the exciton absorption in random fields of the first and second type in single and coupled quantum wells has been calculated. The absorption decreases as H increases in the range of strong magnetic fields, which is in agreement with experimental data. Zh. éksp. Teor. Fiz. 114, 1451–1465 (October 1998)     

半导体量子器件物理讲座 第六讲 半导体量子阱激光器

量子阱结构是半导体光电子器件的核心组成部分,它是半导体光电子集成的重要基础,文章在描述了量子结构的态密度,量子尺寸效应,粒子数反转的基础上,介绍了量子阱导质结构激光器的工作原理,器件结构,器件性能,并对其在可见光激光器和大功率激光器件中显现出来的优越性作了进一步的说明。     

“Spherical” quantum dots

Quantum dots with a three-dimensional confining potential, i.e. “spherical” quantum dots, are considered with inclusion of electron-electron interaction (a quantum analog of the Thomson atom). The energy spectrum of two-electron parabolic quantum dots has been determined by numerical diagonalization of the full Hamiltonian in a one-particle basis. Fiz. Tverd. Tela (St. Petersburg) 40, 2134–2135 (November 1998)     

MV-Algebra for Cultural Rules

This paper reports preliminary results on a new area of application of quantum structures, motivated by a reading of the 2004 monograph Reasoning in Quantum Theory. Ethnographers often describe a particular culture by describing rules of social relations that they assert characterize that culture. Viable cultures exist over periods of time, that is, over sequences of “generations”. To embody this, we define a suitable set of objects and relations, and a structure on which cultural rules act as “operators” on a set of “configurations” on generations. This yields an MV-algebra of those operators. This implies that culture theory might be studied as an example of the theory of quantum structures. The author acknowledges Dick Greechie in appreciation for the many comments he offered on this paper and on the development of this line of research. Useful comments of an unidentified reviewer helped clarify results. Only the author is responsible for any errors, and for the ideas asserted. This paper was delivered at the meetings of the International Quantum Structures Association, IQSA-Malta 2006.     

Linear and nonlinear excitonic absorption in semiconducting quantum wires crystallized in a dielectric matrix

Spectra of linear and nonlinear absorption of GaAs and CdSe semiconducting quantum wires crystallized in a transparent dielectric matrix (inside chrysotile-asbestos nanotubes) have been measured. Their features are interpreted in terms of excitonic transitions and filling of the exciton phase space in the quantum wires. The theoretical model presented here has allowed us to calculate the energies of excitonic transitions that are in qualitative agreement with experimental data. The calculated exciton binding energies in quantum wires are a factor of several tens higher than in bulk semiconductors. The cause of this increase in the exciton binding energy is not only the size quantization, but also the “dielectric enhancement,” i.e., stronger attraction between electrons and holes owing to the large difference between permittivities of the semiconductor and dielectric matrix. Zh. éksp. Teor. Fiz. 114, 700–710 (August 1998)     

A global version of the quantum duality principle

The “quantum duality principle” states that a quantisation of a Lie bialgebra provides also a quantisation of the dual formal Poisson group and, conversely, a quantisation of a formal Poisson group yields a quantisation of the dual Lie bialgebra as well. We extend this to a much more general result: namely, for any principal ideal domainR and for each primepεR we establish an “inner” Galois’ correspondence on the categoryHA of torsionless Hopf algebras overR, using two functors (fromHA to itself) such that the image of the first and the second is the full subcategory of those Hopf algebras which are commutative and cocommutative, modulop, respectively (i.e., they are“quantum function algebras” (=QFA) and“quantum universal enveloping algebras” (=QUEA), atp, respectively). In particular we provide a machine to get two quantum groups — a QFA and a QUEA — out of any Hopf algebraH over a fieldk: apply the functors tok[ν] ⊗k H forp=ν. A relevant example occurring in quantum electro-dynamics is studied in some detail. Presented at the 10th International Colloquium on Quantum Groups: “Quantum Groups and Integrable Systems”, Prague, 21–23 June 2001     

Structure theorem for covariant bundles on quantum homogeneous spaces

The natural generalization of the notion of bundle in quantum geometry is that of bimodule. If the base space has quantum group symmetries, one is particularly interested in bimodules covariant (equivariant) under these symmetries. Most attention has so far been focused on the case with maximal symmetry — where the base space is a quantum group and the bimodules are bicovariant. The structure of bicovariant bimodules is well understood through their correspondence with crossed modules. We investigate the “next best” case — where the base space is a quantum homogeneous space and the bimodules are covariant. We present a structure theorem that resembles the one for bicovariant bimodules. Thus, there is a correspondence between covariant bimodules and a new kind of “crossed” modules which we define. The latter are attached to the pair of quantum groups which defines the quantum homogeneous space. We apply our structure theorem to differential calculi on quantum homogeneous spaces and discuss a related notion of induced differential calculus. Presented at the 10th International Colloquium on Quantum Groups: “Quantum Groups and Integrable Systems”, Prague, 21–23 June 2001. This work was supported by a NATO fellowship grant.     

Anisotropy of optical phonons in semiconductor superlattices: Raman scattering experiments

Experiments on Raman scattering in the “forward” geometry, permitting observation of anisotropy of the optical phonons, are performed on specially prepared short-period GaAs/AlAs superlattice structures with the substrates removed and the surfaces covered with an antireflective layer. The experimental data agree well with the computational results obtained for the angular dispersion of optical phonons in superlattices on the basis of a modified continuum model. Pis’ma Zh. éksp. Teor. Fiz. 68, No. 1, 50–55 (10 July 1998)     

A classification of quantum GL(2,C)’s

We show that the two-parameter standard quantum GL(2, C) (except for roots of unity) and the Jordanian quantum GL(2, C) have the “same” representation theory as the (ordinary) group GL(2, C), and that they are the only quantum groups with this property. Presented at the 9th Colloquium “Quantum Groups and Integrable Systems”, Prague, 22–24 June 2000.     

Multiphoton polymerization with the holographic control of femtosecond and continuous laser radiation

A unit in which two lasers, one with femtosecond and the other continuous radiation, were used was designed and manufactured. Both lasers worked under holographic control conditions provided by two spatial optic modulators. Experiments with creating several polymer structures by several femtosecond optical “traps” simultaneously were performed. The possibility of the production of one polymer article by simultaneous displacement of several femtosecond optical traps was demonstrated. A polymer article was also prepared by several femtosecond traps and manipulated with the use of several continuous traps. The possibility of focusing femtosecond radiation onto an extended object (“thread” 13 μm long) and the preparation of a polymer object by controlling a femtosecond optical trap in three-dimensional space was demonstrated.     

Trends in microdisk laser research and linear optical modelling

Research into microdisk lasers demonstrates new achievements both in the technology and in the associated physical effects and applications. Melting and rounding of the disk edge boosts the Q-factors due to improved surface smoothness. In-plane cavity shape is widely used as a design instrument. Optimal shaping of pumped area lowers the threshold power. Photonic molecules made of several microdisks as “photonic atoms” show lasing at several closely spaced frequencies. A microdisk with a single quantum dot as an active region is considered as the most promising system for realisation of a single photon emitter necessary for quantum computing. These new effects and devices can be simulated with accurate numerical techniques, developed recently for “warm-cavity” linear modelling, that are able to bring a new vision of the physics of lasing.     

Exciton-exciton collisions and conversion of interwell excitons in GaAs/AlGaAs superlattices

The ratio of the densities of intra-and interwell excitons in a symmetric system of coupled quantum wells — a superlattice based on a GaAs/AlGaAs heterostructure — is investigated over a wide range of optical excitation power densities. Conversion of interwell excitons into intrawell excitons as a result of exciton-exciton collisions is observed at high exciton densities. Direct evidence for such a conversion mechanism is the square-root dependence of the interwell exciton density on the optical excitation level. The decrease in the lifetime of interwell excitons with increasing excitation density, as measured directly by time-resolved spectroscopy methods, confirms the explanation proposed for the effect. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 8, 623–628 (25 April 1997)     

Quantum dot lasers and integrated optoelectronics on silicon platform Invited Paper

Chip-scale integration of optoelectronic devices such as lasers, waveguides, and modulators on silicon is prevailing as a promising approach to realize future ultrahigh speed optical interconnects. We review recent progress of the direct epitaxy and fabrication of quantum dot (QD) lasers and integrated guided-wave devices on silicon. This approach involves the development of molecular beam epitaxial growth of selforganized QD lasers directly on silicon substrates and their monolithic integration with amorphous silicon waveguides and quantum well electroabsorption modulators. Additionally, we report a preliminary study of long-wavelength (> 1.3 μm) QD lasers grown on silicon and integrated crystalline silicon waveguides using membrane transfer technology.     

Three short distance structures from quantum algebras

We review known and we present new results on three types of short distance structures of observables which typically appear in studies of quantum group related algebras. In particular, one of the short distance structures is shown to suggest a new mechanism for the introduction of internal symmetries. Presented at the 6th International Colloquium on Quantum Groups: “Quantum Groups and Integrable Systems”, Prague, 19–21 June 1997.     

Bragg quantum wells in weak confinement regime

The optical properties of Bragg quantum wells are studied for exciton confinement under center-of-mass quantization. A variational model of Wannier exciton envelope function, that embodies the correct boundary conditions for center-of-mass, is adopted for calculation. The present non-adiabatic exciton model is compared with adiabatic results and with heuristic “hard sphere” model. The radiative self-energy of a single-quantum well (SQW) and multi-quantum wells (MQWs) are computed in the semiclassical framework, and in effective mass approximation, by self-consistent solution of Schroedinger and Maxwell equations. This microscopic solution is free from “fitting” parameter values, except for the non-radiative broadening, and also the exciton dead-layer and the additional boundary condition are not taken ad hoc, but come coherently from the variational principle and self-consistent Schroedinger-Maxwell solution. Dispersion curves of exciton-polariton propagating in a MQW, under Bragg condition, are studied by selected numerical examples. The case of optical gap in correspondence of higher excited states is studied, and, moreover, the interesting effect of gap enhancement or inhibition, in correspondence of non-resonant Bragg energy, will be addressed.     

Quantum sets and clifford algebras

The mathematical language presently used for quantum physics is a high-level language. As a lowest-level or basic language I construct a quantum set theory in three stages: (1) Classical set theory, formulated as a Clifford algebra of “S numbers” generated by a single monadic operation, “bracing,” Br = {…}. (2) Indefinite set theory, a modification of set theory dealing with the modal logical concept of possibility. (3) Quantum set theory. The quantum set is constructed from the null set by the familiar quantum techniques of tensor product and antisymmetrization. There are both a Clifford and a Grassmann algebra with sets as basis elements. Rank and cardinality operators are analogous to Schroedinger coordinates of the theory, in that they are multiplication or “Q-type” operators. “P-type” operators analogous to Schroedinger momenta, in that they transform theQ-type quantities, are bracing (Br), Clifford multiplication by a setX, and the creator ofX, represented by Grassmann multiplicationc(X) by the setX. Br and its adjoint Br* form a Bose-Einstein canonical pair, andc(X) and its adjointc(X)* form a Fermi-Dirac or anticanonical pair. Many coefficient number systems can be employed in this quantization. I use the integers for a discrete quantum theory, with the usual complex quantum theory as limit. Quantum set theory may be applied to a quantum time space and a quantum automaton. This material is based upon work supported in part by NSF Grant No. PHY8007921.