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The full-wave electromagnetic characterization of reconfigurable antenna sensors for non-invasive detection of melanoma-related anomalies of the skin is presented. To this end, an enhanced locally conformal finite-difference time-domain procedure, based on the definition of effective material parameters and a suitable normalization of the electromagnetic field-related quantities, is adopted. In this way, an insightful understanding of the physical processes responsible for the performance of considered class of devices is achieved. This in turn is important in order to enhance the structure reliability, optimizing the design cycle. A suitable microelectromechanical-system-based sensor layout is finally discussed in details. [ABSTRACT FROM PUBLISHER]

In this paper, we study an unconventional kind of quasi-three-dimensional (3-D) photonic crystal (PhC) with circular lattice pattern: it consists of air holes in a GaAs material (n=3.408) along circular concentric lines. This particular PhC geometry has peculiar behavior if compared with the traditional square and triangular lattices, but it is difficult to model by using conventional numerical approaches such as wave expansion method. The resonance and the radiation aspects are analyzed by the 3-D finite-element method (FEM). The model, based on a scattering matrix approach, considers the cavity resonance frequency and evaluates the input-output relationship by enclosing the photonic crystal slab (PhCS) in a black box in order to define the responses at different input-output ports. The scattering matrix method gives important information about the frequency responses of the passive 3-D crystal in the 3-D spatial domain. A high sensitivity of the scattering parameters to the variation of the geometrical imperfection is also observed. The model is completed by the quality factor (Q-factor) estimation. We fabricated the designed circular photonic crystal over a slab membrane waveguide embedding InAs/GaAs quantum dots emitting around 1.28 mum. Good agreement between numerical and experimental results was found, thus validating the 3-D FEM full-wave investigation. [ABSTRACT FROM PUBLISHER]

Due to their delta-like density of states, quantum dots (QDs) were expected to improve laser device performances with respect to quantum wells (QWs). Nevertheless, some important drawbacks limit this technology. For instance, QD laser still suffers from a low value of the modal gain, due to the low areal density of QDs, and inhomogeneous broadening, especially when multistacked layers are used. In this paper, we demonstrate that a linear increase of the QD modal gain with the QD layers number, as typically achieved in multi-QW lasers, is possible by a careful control of the Stranski-Krastanov QDs growth and QDs stacking optimization. A low-transparency current density of 10 A/cm2 per QD layer and a modal gain of 6 cm-1 per QD layer were achieved from laser structures containing up to seven QD layers. We demonstrate 10-Gb/s direct modulation (until a temperature of 50 degC) and high T 0 (110 K) from a single-mode device containing six QD layers. [ABSTRACT FROM PUBLISHER]

Electron transfer through the redox metalloprotein azurin immobilized on Au (111) by its disulphide bridge is studied by scanning tunneling microscopy (STM) in buffer solution and (for the first time) in air. STM analysis gives evidences of a stable and robust binding of the molecules in both cases. Bright spots, associated with azurin molecules, are clearly visible in STM images. The image contrast of adsorbed azurin is highly affected by the bias potential with proteins visible only for some well-defined voltage values. This experimental demonstration of the possibility to induce tunneling through azurin in air could disclose very interesting perspectives for the development of protein-based hybrid nanodevices operating in nonliquid environments. [ABSTRACT FROM PUBLISHER]

We report a double emission layer structure, incorporating a double phosphorescent ldquoguest/host systemrdquo of tris (1-Phenylisoquinoline) iridium (III) (Ir(piq)3) 15wt% doped into two different host molecules, 4,4'-bis[N-(1-napthyl)-N-phenyl-amino] biphenyl (NPB) and bis-(2-methyl-8-quinolinolato)-4-(phenyl-phenolato) aluminum-(III) (BAlq). The proposed configuration reduces the efficiency rolloff, providing high stability at high operating luminance. A maximum current efficiency of 9.5 cd/A, at a driving voltage of 3 V, and a remarkably long device lifetime of more than 2500 h at a starting luminance of 6000 cd/m2 have been measured. [ABSTRACT FROM PUBLISHER]

In this letter, we report on experimental results of directly modulated single-transverse mode 1.3-mum InAs-InGaAs quantum-dot (QD) lasers in a wide temperature range. A 3.125-Gb/s data modulation over temperature with an extinction ratio up to 10 dB is reported. Moreover, 10-Gb/s eye patterns at 15 degC and 50 degC and 5-Gb/s modulation in the whole explored temperature range (15 degC-85 degC) are demonstrated. These results were obtained by exploiting heterostructures containing six layers of high modal gain InAs QDs grown without incorporation of p-doping in the active region or tunnelling injection structure implementation. QD lasers exhibited a saturation modal gain as high as 36.3 cm-1, ground state lasing from short cavities down to 400-mum length and a characteristic temperature of about 110 K in a large temperature range between 15 degC and 85 degC [ABSTRACT FROM PUBLISHER]

A semiconductor laser containing seven InAs-InGaAs stacked quantum-dot (QD) layers was grown by molecular beam epitaxy. Shallow mesa ridge-waveguide lasers with stripe width of 120 mum were fabricated and tested. A high modal gain of 41 cm-1 was obtained at room temperature corresponding to a modal gain of ~6 cm-1 per QD layer, which is very promising to enable the realization of 1.3-mum ultrashort cavity devices such as vertical-cavity surface-emitting lasers. Ground state laser action was achieved for a 360-mum-cavity length with as-cleaved facets. The transparency current density per QD layer and internal quantum efficiency were 13 A/cm2 and 67%, respectively [ABSTRACT FROM PUBLISHER]