Nanowalled polymer microtubes fabricated by using strained semiconductor templates.

Herein we describe the realization of nanowalled polymeric microtubes through a novel and versatile approach combining the layer-by-layer (LbL) deposition technique, the self-rolling of hybrid polymer/semiconductor microtubes and the subsequent removal of the semiconductor template. The realized channels were characterized in detail using scanning electron and atomic force microscopes. Additionally, we report on the incorporation of a dye molecule within the nanowalls of such microtubes, demonstrating a distribution of the fluorescence signal throughout the whole channel volume. This approach offers the possibility to tailor the properties of micro/nanotubes in terms of size, wall thickness and composition, thus enabling their employment for several applications.

Scalar time domain modeling and coupling of second harmonic generation process in GaAs discontinuous optical waveguide.

We present in this work the scalar potential formulation of second harmonic generation process in chi((2)) nonlinear analysis. This approach is intrinsically well suited to the applications of the concept of circuit analysis and synthesis to nonlinear optical problems, and represents a novel alternative method in the analysis of nonlinear optical waveguide, by providing a good convergent numerical solution. The time domain modeling is applied to nonlinear GaAs asymmetrical waveguide with dielectric discontinuities in the hypothesis of quasi phase matching condition in order to evaluate the efficiency conversion of the second harmonic signal. The accuracy of the modeling is validated by the good agreement with the published experimental results. The effective dielectric constant method allows to extend the analysis also to 3D optical waveguides.

Linear increase of the modal gain in 1.3 µm InAs/GaAs quantum dot lasers containing up to seven-stacked QD layers.

The authors have recently demonstrated the enhancement of the quantum dot laser modal gain, linearly scaling with the number of stacked QD layers. These results allowed the achievement of multi-quantum dot (MQD) lasers, the zero-dimensional counterpart of MQW lasers, with a modal gain as high as 42 cm(-1), in a seven-layer structure. A detailed investigation of the structural and optical properties was performed on laser structures with three, five and seven QD layers. Such an investigation clearly shows that the high uniformity of QD layer features is responsible for the linear increase of the modal gain and its high value.