Design and realisation of a MZI type polymer based high speed EO-modulator

We designed a 20 GHz Mach Zehnder interferometric EO-modulator based on a new developed polyesterimide. Measurements show a V/sub /spl pi// of 7.5 V, an insertion loss of 11 dB and an extinction ratio exceeding 20 dB for an interaction length of 2 cm

Electron and hole states in quantum-dot quantum wells within a spherical 8-band model

In order to study heterostructures composed both of materials with strongly different parameters and of materials with narrow band gaps, we have developed an approach, which combines the spherical 8-band effective-mass Hamiltonian and the Burt's envelope function representation. Using this method, electron and hole states are calculated in CdS/HgS/CdS/H_2O and CdTe/HgTe/CdTe/H_2O quantum-dot quantum-well heterostructures. Radial components of the wave functions of the lowest S and P electron and hole states in typical quantum-dot quantum wells (QDQWs) are presented as a function of radius. The 6-band-hole components of the radial wave functions of an electron in the 8-band model have amplitudes comparable with the amplitude of the corresponding 2-band-electron component. This is a consequence of the coupling between the conduction and valence bands, which gives a strong nonparabolicity of the conduction band. At the same time, the 2-band-electron component of the radial wave functions of a hole in the 8-band model is small compared with the amplitudes of the corresponding 6-band-hole components. It is shown that in the CdS/HgS/CdS/H_2O QDQW holes in the lowest states are strongly localized in the well region (HgS). On the contrary, electrons in this QDQW and both electron and holes in the CdTe/HgTe/CdTe/H_2O QDQW are distributed through the entire dot. The importance of the developed theory for QDQWs is proven by the fact that in contrast to our rigorous 8-band model, there appear spurious states within the commonly used symmetrized 8-band model.Comment: 15 pages, 5 figures, E-mail addresses: [email protected], [email protected]

Electron-Hole Correlations and Optical Excitonic Gaps in Quantum-Dot Quantum Wells: Tight-Binding Approach

Electron-hole correlation in quantum-dot quantum wells (QDQW's) is investigated by incorporating Coulomb and exchange interactions into an empirical tight-binding model. Sufficient electron and hole single-particle states close to the band edge are included in the configuration to achieve convergence of the first spin-singlet and triplet excitonic energies within a few meV. Coulomb shifts of about 100 meV and exchange splittings of about 1 meV are found for CdS/HgS/CdS QDQW's (4.7 nm CdS core diameter, 0.3 nm HgS well width and 0.3 nm to 1.5 nm CdS clad thickness) which have been characterized experimentally by Weller and co-workers [ D. Schooss, A. Mews, A. Eychmuller, H. Weller, Phys. Rev. B, 49, 17072 (1994)]. The optical excitonic gaps calculated for those QDQW's are in good agreement with the experiment.Comment: 3 figures, to appear in Phys.Rev.

Association of major depression with subtypes of nicotine dependence found among adult daily smokers: A latent class analysis

Nicotine dependence (ND) and major depression (MD) are highly prevalent disorders that frequently co-occur. Less is known about which aspects of ND are most strongly associated with MD. The present study was designed to determine if subtypes of smokers exist and differ in their risk of MD and lifetime MD symptoms. Latent class analysis was used to identify profiles of DSM-IV ND criteria for 8,842 daily smokers drawn from the larger 2001-2002 National Epidemiologic Survey on Alcohol and Related Conditions (NESARC). We found evidence for 4 distinct subtypes of smokers mainly characterized by increasing levels of ND severity, by number of criteria endorsed. We found a dose-response relationship between classes by increasing ND severity and odds of past-year MD and lifetime depression criteria. Class 2 was characterized by higher symptom endorsement probabilities (SEPs) for wider range of ND criteria and a higher odds of MD (OR = 3.66) compared to class 3, which was characterized by higher SEPs for physiological ND criteria, higher prevalence of ND (class 2, 71.50% vs. class 3, 81.57%), and a lower odds of MD (OR = 2.15). A post hoc contrast showed these two distinct classes of respondents with mild to moderate ND significantly differed in their likelihood of MD comorbidity (F = 12.25, 1 df, p = 0.0008). ND severity mainly characterized the classes, but unique differences may exist between smokers with mild to moderate ND. Individuals with symptom profiles not characterized by physiological dependence endorse wider range of ND criteria and have a higher likelihood of MD. (C) 2009 Elsevier Ireland Ltd. All rights reserved

Chemically synthesized carbon nanorods with dual polarized emission

We realized the synthesis of carbon nanorods—monodisperse colloidal particles with a length of 50 nm and a width of 20 nm—which can be considered an addition to the family of light-emitting carbon-based nanostructures. Their anisotropic shape is determined by the use of the surfactant aminopropylisobutyl polyhedral oligomeric silsesquioxane, and their optical properties originate from domains of polycyclic aromatic hydrocarbons incorporated within an inorganic framework. The nanorods show dual polarized emission with a quantum yield of 15–20% and emission anisotropy of ∼0.3, which changes from blue (460 nm) to yellow (565 nm) depending on the excitation wavelength. These carbon nanorods expand the range of light-emitting carbon nanomaterials available for optoelectronic and biolabeling applications.This work was supported by NPRP grant no. 8-878-1-172 from the Qatar National Research Fund (a member of the Qatar Foundation), the Research Grant Council of Hong Kong S.A.R. (CityU 11306619), the Ministry of Education and Science of the Russian Federation (grant 14.Y26.31.0028), by the RFBR Project No. 18-29-19122 mk, the National Natural Science Foundation of China (51702115), the Bavarian State Ministry of Science, Research, and Arts through the grant -Solar Technologies go Hybrid (SolTech), and the Alexander von Humboldt Foundation.Scopu