ISSN 1223-7027
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| Title Investigation on photonic-corral-mode quantum ring lasers by laser scanning microscopy |
| Author(s) Stanciu, GA; Stanciu, SG; Hristu, R; Kwon, O; Kim, DK |
| Editor(s) Marciniak, M |
| Source ICTON 2008: PROCEEDINGS OF 2008 10TH ANNIVERSARY INTERNATIONAL CONFERENCE ON TRANSPARENT OPTICAL NETWORKS, VOL 440-42 2008 |
| Conference Title 10th International Conference on Transparent Optical Networks |
| Conference Date JUN 22-26, 2008 |
| Conference Location Athens, GREECE |
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| Abstract Ultra low threshold microcavity lasers are ideal candidates for high-density optical interconnect light Sources. Although they have been extensively studied for the last decade, mu A-level electro-pumped quantum confined lasers are still under investigation. Photonic-corral-mode quantum ring (PQR) lasers with the linewidth narrower than 0.55 angstrom generate micro-to-nano-ampere thresholds, and become ideal for CMOS-driven high-density emitter arrays for intra-chip optical interconnect as well as other applications such as displays. The PQR offers the following, advantages for extremely high-density emitter Source chip, over other semiconductor lasers presently available: a photonic quantum corral effect leads to naturally-born quantum wire behaviours for imminently recombinant carriers-, the mu A – nA threshold current capabilities mean kilo to mega PQR chip; root T – dependent spectral red shifts are smaller at high operating temperatures, allowing uniform and reliable chip emission with minimal temperature sensitivities. By using laser beam induced Current technique (LBIC) technique in laser scanning microscopy (LSM) we investigated the photocurrent confinement in the laser structure. The photocurrent map gives the possibility to analyze the laser structure Uniformity. |
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| Title Photonic-Corral-Mode Quantum Ring Lasers investigated by Laser Scanning Microscopy and Near Field Microscopy |
| Author(s) Stanciu, GA; Stanciu, SG; Hristu, R; Kim, DK; Kwon, O |
| Source 2008 2ND ICTON MEDITERRANEAN WINTER (ICTON-MW)207-210 2008 |
| Conference Title 2008 2nd ICTON Mediterranean Winter Conference |
| Conference Date DEC 11-13, 2008 |
| Conference Location Marrakech, MOROCCO |
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| Abstract Ultralow threshold microcavity lasers are ideal candidates for high-density optical interconnect light sources. Although they have been extensively studied for the last decade, mu A-level electro-pumped quantum confined lasers are still under investigation. Photonic-corral-mode quantum ring (PQR) lasers with the linewidth narrower than 0.55 angstrom generate micro-to-nano-ampere thresholds, and become ideal for CMOS-driven high-density emitter arrays for intra-chip optical interconnect as well as other applications such as displays. By using laser beam induced current technique (LBIC) technique in laser scanning microscopy (LSM) we investigated the photocurrent confinement in the laser structure. The photocurrent map gives the possibility to analyze the laser structure uniformity. The emission spectra of a PQR laser was investigated by using of microscopic optical fiber probe. |
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| Title TUNNELING AT EMITTER PERIPHERY IN SILICON NITRIDE PASSIVATED InP/InGaAs HBTs |
| Author(s) Sachelarie, D; Predusca, G; Stanciu, GA; Stanciu, SG |
| Source 2008 IEEE 20TH INTERNATIONAL CONFERENCE ON INDIUM PHOSPHIDE AND RELATED MATERIALS (IPRM)391-394 2008 |
| Conference Title 20th International Conference on Indium Phosphide and Related Materials |
| Conference Date MAY 25-29, 2008 |
| Conference Location Versailles, FRANCE |
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| Abstract This work presents a new explanation of the abnormal injection phenomena at emitter-base junction of the silicon nitride passivated InP-based heterojunction bipolar transistors. We have suggested that the emitter mesa sidewall is accumulated and that thermionic field emission from this zone becomes the principal component of the collector current. The proposed theoretical model is in good agreement with experimental collector current Gummel plots and with atomic force microscopy measurements of mesa emitter edge. |
ISSN 1092-8669
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| Title AFM examination of sol-gel matrices doped with photo sensitizers |
| Author(s) Wysocka, K; Ulatowska-Jarza, A; Bauer, J; Holowacz, I; Savu, B; Stanciu, G; Podbielska, H |
| Source OPTICA APPLICATA 38 (1):127-136 2008 |
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| Abstract Various compounds may be entrapped into the sol-gel materials, including the photosensitive agents. The nanostructure of the final material depends on the matrix itself, as well as on the structural properties of doped compound. In this work, sol-gel matrices were produced from silica based precursor tetraethoxysilan (TEOS) in the form of single layers deposited on microscopic glasses. Materials were produced with molar ratios R = 20, 32, 40 (R – the number of solvent (ethanol) moles to the number of precursor (TEOS) moles). Additionally, for each material two various concentrations of photosensitizers were prepared (0.5 mg/ml and 0.05 mg/ml). On the basis of AFM images from Atomic Force Microscope Quesant 350, the following roughness parameters were evaluated: roughness average, peak-peak height, surface skewness and fractal dimension. The roughness average S-a parameter gives information about the statistical average properties. The peak-peak height S-y is defined as the height difference between the highest and the lowest pixel in the image. The surface skewness S-sk describes the asymmetry of the height distribution histogram. The fractal dimension S-fd is calculated for the different angles by analyzing the Fourier amplitude spectrum. Comparing the results we stated that average roughness increases with increasing R factor for protoporphyrine IX dimethylester (PPIX) (dimethyl-8,13-divinyl-3,7,12,17-tetramethyl-21H,23H-porphine-2,18-dipropionate) and photolon (18-carboxy-20-(carboxymethyl)-8-ethenyl-13-ethyl-2,3-dihydro3,7,12,17-tetramethyl-21H,23H-porphin-2-propionic acid) in higher concentrations. This means that photosensitizers used as dopants influence the smoothness of sol-gel matrix. We also noticed that the smallest roughness is observed in the material doped with PPIX in higher concentration. This was stated for all the images analyzed. This indicates that sol-gel matrix enclosures the PPIX molecules, resulting in smooth material. |
| ISSN 0078-5466 |
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| Title Nanostructured bioglass thin films synthesized by pulsed laser deposition: CSLM, FTIR investigations and in vitro biotests |
| Author(s) Floroian, L; Savu, B; Stanciu, G; Popescu, AC; Sima, F; Mihailescu, IN; Mustata, R; Sima, LE; Petrescu, M; Tanaskovic, D; Janackovic, D |
| Source APPLIED SURFACE SCIENCE 255 (5):3056-3062 2008 |
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| Abstract We report the synthesis by pulsed laser deposition of thin structures of two bioactive glasses belonging to the SiO2-Na2O-K2O-CaO-MgO-P2O5 system, on medical grade Ti substrates. We evaluated their biocompatibility after immersion in simulated body fluids and by performing cells adhesion tests. The Films were characterized by confocal scanning laser microscopy and Fourier transform infrared spectrometry, before and after 30 and 46 days immersion in fluids. Our studies demonstrated that deposited coatings were degraded in simulated fluids. A new apatite layer was synthesized by ions changing with the fluid during the decomposition of bioglasses. We investigated after immersion in fluids cells adhesion and the cytoskelet organization of synthesized structures, by fluorescence microscopy. A good adhesion to bioglass coatings was evidenced. (C) 2008 Elsevier B.V. All rights reserved. |
| ISSN 0169-4332 |
| DOI 10.1016/j.apsusc.2008.08.105 |
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| Title Density of impurity states of shallow donors in a quantum well under intense laser field |
| Author(s) Niculescu, EC; Burileanu, LM; Radu, A |
| Source SUPERLATTICES AND MICROSTRUCTURES 44 (2):173-182 2008 |
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| Abstract The density of donor impurity states in a square GaAs-AlGaAs quantum well under an intense laser field is calculated taking into account the laser dressing effects on both the Coulomb potential and the confining potential. Using the effective-mass approximation within a variational scheme, the donor binding energy is obtained as a function of the laser dressing parameter, and the impurity position. Our results point out that a proper consideration of the density of impurity states may be of relevance in the interpretation of the optical phenomena related to shallow impurities in quantum wells, where the effects of an intense laser field compete with the quantum confinement. (C) 2008 Elsevier Ltd. All rights reserved. |
| ISSN 0749-6036 |
| DOI 10.1016/j.spmi.2008.03.005 |
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| Title INTENSE FIELD EFFECTS ON HYDROGENIC IMPURITIES IN QUANTUM WELLS |
| Author(s) Niculescu, EC; Burileanu, LM; Radu, A |
| Source UNIVERSITY POLITEHNICA OF BUCHAREST SCIENTIFIC BULLETIN-SERIES A-APPLIED MATHEMATICS AND PHYSICS 70 (4):21-24 2008 |
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| Abstract In this paper we discuss the effect of the high-frequency laser field and the impurity position on the binding energy of the shallow acceptors in GaAs/Al0.3Ga0.7As quantum wells. The calculations were performed within the effective-mass approximation and by using a variational method. |
| ISSN 1223-7027 |
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| Title BINDING ENERGY OF A SCREENED DONOR IN A CYLINDRICAL QUANTUM WIRE UNDER APPLIED MAGNETIC FIELDS |
| Author(s) Niculescu, EC; Burileanu, L |
| Source UNIVERSITY POLITEHNICA OF BUCHAREST SCIENTIFIC BULLETIN-SERIES A-APPLIED MATHEMATICS AND PHYSICS 70 (2):55-62 2008 |
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| Abstract By a variational method, we calculate the binding energy of a screened hydrogenic donor in a GaAs-Al0 3Ga0 -As quantum-well wire in the presence of a uniform magnetic field applied parallel to the wire axis The binding energy is obtained as a function of the wire radius, the field strength and the screening parameter. Our results show that the effects of spatial variation of dielectric screening on edge wire donors are larger than those on center donors. |
| ISSN 1223-7027 |
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| Title BINDING ENERGY OF AN OFF-CENTER DONOR IN CYLINDRICAL QUANTUM-WELL WIRES UNDER INTENSE LASER FIELDS |
| Author(s) Niculescu, EC; Radu, A |
| Source UNIVERSITY POLITEHNICA OF BUCHAREST SCIENTIFIC BULLETIN-SERIES A-APPLIED MATHEMATICS AND PHYSICS 70 (1):67-75 2008 |
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| Abstract In this work, we have investigated the effect of the intense high frequency laser field on the ground-state binding energy of hydrogenic impurity in cylindrical GaAs-AlGaAs quantum well wires as function of the impurity position. The binding energies were obtained using the effective-mass approximation within a variational scheme. We have shown that in the strong confinement regime the presence of the linearly polarized laser radiation partially resolves the degeneracy of donor states corresponding to symmetrical position of the impurity. |
| ISSN 1223-7027 |
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