A special microstructured optical fiber, which may be used in a wavelength-division-multiplexing (WDM) optical fiber transmission system for residual chromatic dispersion compensation, is designed and analyzed. The proposed structure is obtained by introducing a small Ge-doped core at the center of a conventional photonic crystal fiber. The behavior of the resulting geometry has been optimized by a genetic algorithm in conjunction with an efficient vectorial finite element formulation. Numerical results show that the designed photonic crystal fiber exhibits flattened negative dispersion over E + S + C + L + U wavelength bands with an average dispersion of - 212 ps ·km^-1 ·nm^-1.

An efficient finite-element vector beam propagation formulation for dielectric media with transverse anisotropy is thoroughly presented. This formulation is expressed in terms of the magnetic field's transverse components and includes perfectly matched layers at the truncated boundaries and the wide-angle Pade approach. Several key examples demonstrate the usefulness and effectiveness of the present scheme.

A very short passive polarization rotator is proposed, consisting of a single-section asymmetric waveguide. The use of a genetic algorithm together with the finite-element method was crucial to achieve a structure with 99% polarization conversion and a length of 90 /spl mu/m. This optimum structure exhibits a low total insertion loss: 1.16 dB.

In this work a plasmonic sensor with a D-Shaped microstructured optical fiber $\left(\mathrm{MOF}\right)$ is proposed to detect a wide range of analyte refractive index $\left(\mathrm{RI} ;{\mathrm{n}}_{\mathrm{a}}\right)$ by doping the pure silica $\left({\mathrm{SiO}}_2\right)$ core with distinct concentrations of Germanium Dioxide $\left({\mathrm{GeO}}_2\right)$, causing the presentation of high spectral sensitivity. In this case, the fiber is shaped by polishing a coating of ${\mathrm{SiO}}_2$, on the region that will be doped with ${\mathrm{GeO}}_2$, in the polished area, a thin gold $\left(\mathrm{Au}\right)$ layer, which constitutes the plasmonic material, is introduced, followed by the analyte, in a way which the gold layer is deposited between the ${\mathrm{SiO}}_2$. and the analyte. The numerical results obtained in the study shows that the sensor can determine efficiently a range of 0.13 refractive index units $\left(\mathrm{RIU}\right)$, with a limit operation where ${\mathrm{n}}_{\mathrm{a}}$ varies from 1.32 to 1.45. Within this application, the sensor has reached an average wavelength sensitivity $\left(\mathrm{WS}\right)$ of up to $11,650.63 \mathrm{nm}/\mathrm{RIU}$. With this level of sensitivity, the D-Shaped format and wide range of ${\mathrm{n}}_{\mathrm{a}}$ detection, the proposed fiber has great potential for sensing applications in several areas.

This study analyses the influence of a metasurface coupled to a rectangular microstrip antenna. The proposed metasurface converts linearly polarised electromagnetic waves into circularly polarised electromagnetic waves. The rectangular microstrip antenna is designed to operate at 2.45 GHz. The metasurface is coupled to the antenna in order to provide a structure capable of radiating circularly polarised electromagnetic waves without the need for adjustments to the antenna feed. In this analysis, the metasurface was designed from unit cells, distributed in a periodic arrangement acting as a polariser, when coupled to the upper part of the antenna. The geometry of the unit cells and their distribution in the arrangement were calculated in order to obtain an axial ratio below 3 dB in the design frequency range. Prototypes of the microstrip antenna and the metasurface were constructed to obtain experimental results and it was possible to observe a good convergence between the simulated and measured results.