R.D. Crespo

Magnetostatic interaction in Fe-Co nanowires

Arrays of Fe-Co alloy nanowires with diameter around 35nm and several micrometers in length have been synthesized by codepositing Fe and Co into porous anodic alumina. The morphology, structure, and magnetic properties of the nanowires (hysteresis loops and remanence curves) were characterized by SEM, TEM, X-ray diffraction (XRD), and VSM, respectively. The XRD patterns indicate that the Fe-Co nanowires present a body-centered cubic (bcc) structure and a preferred (110) orientation perpendicular to the template surface. From the hysteresis loops obtained with the magnetic field applied in the axis direction of the nanowires, we can observe that the coercive field slightly decreases when the nanowire length increases. This magnetic behaviour is analyzed considering the shape anisotropy and the dipolar interactions among nanowires.

Fabrication parameters of Ti:LiNbO3 monomode optical waveguides from mode size

The fabrication parameters of a Ti:LiNbO3 waveguide determine the number and size of the modes supported by the waveguide. Optimization of the electro-optic-induced index change in the waveguide modulators requires both fabricating singlemode waveguides and controlling the mode size. We present a procedure of determining singlemode waveguide fabrication parameters from the needed mode size.

Complete analyis of a new method for obtaining the characteristics of slab optical waveguides with step index profiles from measurements of effective indices

A new method for characterizing step index optical waveguides from experimental values of effective indices of guided modes is presented. We find the refractive index of the film by means of a linear fitting between the square of effective index and the square of the sum of mode index plus one, avoiding the use of the highest mode; further, statistical procedure has been used to evaluate the waveguide depth through the dispersion equation (without solving the transcendental equation) avoiding the use of zeroth mode. We have checked the method by using the Monte Carlo method, analyzing all possible guides with step index profile by means of normalized parameters. Furthermore, we compare the method with those presented by other authors and we find good agreement. The proposed method is easier than others and the error analysis shows its accuracy to be good.

Analysis of single-mode optical waveguides by means of an equivalent optical waveguide technique

We present a theoretical method that makes it possible to analyze 3-D integrated optical waveguides with arbitrary refractive-index profiles. With this method it is easy to obtain effective indices, propagation constants, and coupling/switching properties of planar and channel optical waveguides. This theoretical approach involves modeling the original optical waveguide by means of an equivalent optical waveguide whose eftective index is evaluated by applying a technique that we call the asymptotic eftective-index method. The numerical values show good convergence and accuracy for effective indices, propagation constants, and coupling/switching characteristics. Theoretical and experimental values are given.

Method to analyze optical waveguides with arbitrary index profiles

We present a theoretical method which makes it possible to analyze 3-D integrated optical waveguides with arbitrary refractive index profiles. With this method it is easy to obtain effective indexes, propagation constants and coupling/switching properties of planar and channel optical waveguides. This theoretical approach involves modelling the original optical waveguide by means of an Equivalent Optical Waveguide whose effective index is evaluated by applying a technique that we call the Asymptotic Effective Index Method. The theoretical results show good convergence and accuracy for effectives indexes, propagation constants and coupling/switching characteristics.

Equivalent optical waveguide model to analyze arbitrary optical waveguides

We present a theoretical method which makes it possible to analyze 3D integrated optical waveguides with arbitrary refractive index profiles. With this method it is easy to obtain effective indexes, propagation constants and coupling/switching properties of planar and channel optical waveguides. This theoretical approach involves modelling the original optical waveguide by means of an Equivalent Optical Waveguide whose effective index is evaluated by applying a technique that we call the Asymptotic Effective Index Method. The theoretical results show good convergence and accuracy for effectives indexes, propagation constants and coupling/switching characteristics.