This article [J. Micro/Nanolith. MEMS MOEMS. 10, , 043013 (2011)] was published online on 1 December 2011 without three additional coauthors: Isabel Alvarez, Maria Teresa Fernandez, and Agustin Costa, all from the Physical Chemistry Department, University of Oviedo, Oviedo, Spain. The authors regret the omissions.
Carbon microelectrodes have been implemented as sensing phases in order to improve the efficiency of the electrochemical sensing in capillary electrophoresis microchips. Surface and embedded carbon microelectrodes were fabricated on glassy substrates using a laser lithography technique. Both types of microelectrodes were successfully verified and, in the case of embedded microelectrodes, are proving to be an excellent alternative to increase the sensitivity of biosensors based on capillary electrophoresis.
KEYWORDS: Waveguides, Refractive index, Photonic crystals, Dielectrics, Planar waveguides, Optical sensors, Global system for mobile communications, Scattering, Wave propagation, Radio propagation
In this work, we demonstrate the possibility of planar waveguide photonic crystals to be used in general sensing proposes. The electromagnetic performance of photonic crystals obtained by connecting in cascade planar optical waveguides with high index contrast was analysed. In our case, the periodicity of the lattice is obtained in the substrate, instead of in the guiding region, as in conventional waveguide photonic crystals. The theoretical model involves a new generalized scattering matrix concept, together with the generalized telegraphist equations formulism and the modal matching technique. The implementation of the pattern waveguide photonic crystals was carried out by connecting abruptly planar optical waveguides. To get the periodic lattice, we use the substrate refractive index as lattice periodic parameter, and the waveguide lengths as lattice constant. Photonic band gaps and photonic windows were obtained. In all cases the power conservation was excellent. If a local defect is introduced in the PBG structure, an on state can be introduced in the gap. The local defect modifies the optical path, so that the PBG is broken, and the on state appears in the PBG interval. Besides, the on state wavelength can be tuned if the optical path of the defect is modified: changing the physical length or/and the refraction index of the defect. In this way, planar waveguide photonic crystals could be used for sensing applications when a specimen modifies refraction index lattice site. Sensing properties of planar waveguide photonic crystals, with single and double sensing channel, are demonstrated.
Refraction index evaluation by means of a quasi-normal incidence technique is presented. The theoretical procedure
involves Fresnel equations as well as a complete statistical algorithm developed for experimental values treatment. The
characteristics of the experimental technique are analyzed in depth and rules for high precision measurements are given.
Refraction indices of soda lime and BK7 substrates were evaluated as function of wavelength. Accuracies of the order of
10-3 in refraction indices determination were obtained. Finally, and making use of high precision polishing techniques,
the authors are adapting this method for the reproduction of step and graded index profile functions and diffusion depths
of integrated optical waveguides.
KEYWORDS: Waveguides, Global system for mobile communications, Integrated optics, Electromagnetism, Electromagnetic scattering, Refractive index, Diffusion, Optical engineering, Planar waveguides, Transmission electron microscopy
We present an extension of the equivalent optical waveguide method to analyze multimode optical waveguides with arbitrary refractive-index profiles. Effective indices, propagation constant and coupling/switching properties of multimode planar by means of an equivalent optical waveguide for each guide mode. The effective indices are evaluated by applying the asymptotic effective index method. Numerical values were obtained and compared with those presented by other authors. In all cases, a good convergence and accuracy was noticed.
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.
Julio Fernandez Diaz, Jose Virgos Rovira, Ana Guinea Rueda, Sergio Palacios Diaz, Rosario Diaz Crespo, Susana Fernandez, J. Martinez-Garcia, Jose Rodriguez Garcia
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.
In this work, a method for evaluating the radiation losses of abrupt transitions in planar optical waveguides is presented. We analyze optical discontinuities due to geometrical changes and/or variations of the refractive index profile of the waveguides. The modal matching technique is used to evaluate the radiation, as well as the reflection and transmission coefficients. Both symmetrical and non-symmetrical planar waveguides are considered. Step and graded index profiles are taken into account. Results of radiation losses are given.
Jose Rodriguez Garcia, Susana Fernandez, Sergio Palacios Diaz, Rosario Diaz Crespo, Julio Fernandez Diaz, Ana Guinea Rueda, Jose Virgos Rovira, Jose Olivares
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.
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.
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.
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