Andreea Lupu - Academia.edu (original) (raw)

Papers by Andreea Lupu

$Research paper thumbnail of Analysis of ultra refraction properties in strong index contrast slab photonic crystals$

Optics Communications, 2007

This paper deals with the theoretical analysis of ultra refraction properties of slab photonic cr... more This paper deals with the theoretical analysis of ultra refraction properties of slab photonic crystals. Strong angular dispersions induced by wavelength variations have been experimentally observed near the Γ–M and Γ–K directions around λ = 1320 nm with negative and positive signs, respectively. An interpretation of these phenomena using three-dimensional plane wave method (3D-PWM) and finite-difference time-domain (3D-FDTD) calculations is presented. Equifrequency surfaces are obtained from PWM calculations and group velocities of Bloch waves excited in the patterned medium are predicted as a function of the incident wave wavelength and wavevector orientation. FDTD calculations have been performed to evaluate the influence of the finite size of the structure and to estimate the photonic crystal coupling losses for various configurations. This theoretical approach allows identifying Bloch waves responsible for the observed properties.

Applied Physics Letters, 2005

The low excess loss experimental demonstration of ten successive light divisions is presented. Th... more The low excess loss experimental demonstration of ten successive light divisions is presented. This distribution is realized by using shallow-etched rib silicon-on-insulator waveguides with compact beam splitters and 90° turns based on total internal reflection corner mirrors. The measured excess optical loss is only 0.7dB per division. This result is an important step in a 1 to 1024 optical distribution demonstration.

Applied Physics Letters, 2007

Physica Status Solidi (a), 2008

We report the demonstration of intersubband modulators operating at telecommunication wavelengths... more We report the demonstration of intersubband modulators operating at telecommunication wavelengths at room temperature based on GaN/AlN quantum wells. We first investigate electro-optical modulators making use of electron tunneling in coupled quantum wells. Electro-absorption modulation with opposite sign induced by the electron tunneling between the reservoir and active quantum wells is observed at λ = 1.3–1.6 µm and λ = 2.2 µm. We show that by reducing the mesa size down to 15 × 15 µm2, optical modulation bandwidth as large as 3 GHz can be obtained. We then investigate waveguide intersubband modulators relying on the depletion of the ground electronic state of a 3 quantum well active region. Modulation depths as large as 14 dB in the wavelength range of 1.2–1.6 µm are obtained under –9 V/+7 V voltage swing. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Applied Physics Letters, 2004

Experimental results for the refractive index variation obtained by hole depletion in SiGe /Si mu... more Experimental results for the refractive index variation obtained by hole depletion in SiGe /Si multiple quantum wells inserted in a reverse-biased p-i-n junction are reported. The electronic contribution to the index variation is unambiguously separated from the thermal one. Measured refractive index changes around 4.2×10-5V-1 are in quite good agreement with modeling.

Physica Status Solidi B-basic Solid State Physics, 2006

GaN/AlN quantum dot photodetectors based on intraband absorption and in-plane carrier transport h... more GaN/AlN quantum dot photodetectors based on intraband absorption and in-plane carrier transport have been fabricated and characterized. These photodetectors operate at room temperature at telecommunication wavelengths (1.3–1.55 μm). Their TM-polarized intraband absorption is ascribed to the transition from the ground state s to the excited state pz of the GaN dots. The responsivity peaked at 1.41 μm is as high as 8 mA/W at room temperature for the interdigitated contact photodetector. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Superlattices and Microstructures, 2006

Roumanian archives of microbiology and immunology

Toxicology in Vitro

We report results regarding the in vitro toxicology of γ-Bi2O3 represented by its isomorphous pha... more We report results regarding the in vitro toxicology of γ-Bi2O3 represented by its isomorphous phase Bi12TiO20 (γ-BTO). The γ-BTO microparticles were synthesized by two methods: coprecipitation from a bismuth nitrate-tetrabutyl titanate solution and solid state reaction of Bi2O3 and TiO2 oxides. The structural and morphological characteristics of the obtained materials were determined using X-ray diffraction (XRD), selected area electron diffraction (SAED), transmission (TEM) and scanning (SEM) electron microscopy. The elemental composition was investigated using energy dispersive spectrometry (EDS). The cytotoxicity and oxidative/nitrosative stress (intracellular reactive oxygen species (ROS) and nitric oxide (NO) release) induced by the studied microparticles in HepG2, SH-SY5Y and 3T3-L1 cell cultures were determined using the MTT, DCF-DA (2',7'-dichlorfluorescein-diacetate) and Griess methods respectively. Depending on the cell type and γ-BTO concentration, results showed only weak cytotoxic effects after 24h of γ-BTO exposure and cell proliferation effects for longer treatment times. Only reduced NO release increases (corresponding to high γ-BTO concentrations) were detected in case of SH-SY5Y and 3T3-L1 cells. The intracellular ROS production (higher for HepG2 cells) appeared inversely proportional to the γ-BTO concentration. The obtained results indicated a promising in vitro biocompatibility of γ-BTO and encourage further studies regarding its potential for biomedical applications.

Acta Microbiologica Et Immunologica Hungarica, 2008

Influence of the novel arthritis drug-substance MCS-18 on the antibody (Ab) production against te... more Influence of the novel arthritis drug-substance MCS-18 on the antibody (Ab) production against tetanus toxoid (TT) and diphtheria toxoid (DT) antigens was tested in vivo. Possible involvement of MCS-18 in Toll-like receptor (TLR) signalling pathway was further considered. Immunization of male CD1 mice was done with subcutaneous injection of TT emulsified in Freund&amp;amp;amp;#39;s Complete (FCA) or Incomplete Adjuvant (FIA) and mixed diversly with MCS-18 and different test substances. To investigate the influence of TLR activation Pam3Cys and lipopolysaccharide (LPS) emulsified in FIA were tested in combinations with MCS-18. Antibody production was analysed in vivo by tetanus- or diphtheria-toxin neutralization test. Immunogenicity of TT was significantly enhanced if administered together with FCA or TLR agonists Pam3Cys or LPS emulsified in FIA. It was shown that MCS-18 attenuated strongly the production of anti-TT Ab if administered together with the Ab elicitor FCA or TLR agonists in various combinations. MCS-18 was also active via oral administration. These findings suggest that MCS-18 could be a potent, non-toxic antagonist or a down-regulator of TLR signalling pathway. Investigations on further models are needed to establish ifMCS-18 may influence particularly the production of RA-specific auto-antibodies, too.

Acta Microbiologica et Immunologica Hungarica, 2008