Electrochemical oxygen pump sensors are increasingly important in a range of industrial sensing applications. However, their development has traditionally been based on inefficient empirical approaches. We have built a detailed finite-element model of an oxygen pump electrochemical sensor that is able to simulate the distribution of oxygen within sensor components under a range of conditions. This has been used to predict key performance parameters such as the steady state output current as a function of oxygen concentration, the startup characteristics and the transient response to a step change in oxygen concentration. The model is a powerful tool enabling multiple design concepts to be compared without the need for time consuming prototype sensor construction.

An integrated photonic routing system based on non defect waveguides is presented in this paper. The self-collimation effect in photonic crystals with 2D periodicity is used for the design of waveguides. A numerical investigation to determine self-collimation spectral range in hexagonal/rectangular lattice photonic crystals is done. It is demonstrated the routing of more self-collimated Gaussian beams travelling through a hexagonal/rectangular lattice photonic crystal, on the same optical layer. Using these unique advantages of allowing self-collimated beams to cross each other without coupling and the photonic bandgap properties, one can devise structureless interconnects for photonic integrated circuits [1].

Damping effects are very important in MEMS-based sensors and actuators. In this paper we use analytical models and finite element (FE) computations to quantify the energy losses due to viscous fluid damping, acoustic radiation and thermo-elastic damping. To treat the case where squeeze/slide film models can not be applied, we have implemented in a commercial FE package a new incompressible flow solver based on a gauge formulation. We are thus able to solve for full flows around complex 3D geometries in the frequency domain and predict viscous damping of resonant MEMS structures. The full methodology is exemplified on the response of a MEMS silicon resonator, including acoustic driving and piezoelectric sensing.

A photonic crystal with two-dimensional (2D) periodicity integrated narrow band filter is presented in this paper. A combination of waveguide - cavity - waveguide based on photonic crystal with 2D periodicity is used in order to obtain an integrated, high performance narrow band filter. Through the Finite-Difference Time Domain simulation of light propagation, we demonstrate a good performance regarding the band and area of the filter that can be used in photonic integrated circuits.

This paper introduces a pressure sensing structure configured as a stress sensitive differential amplifier (SSDA), built on a Silicon-on-Insulator (SOI) membrane. Theoretical calculation show the significant increase in sensitivity which is expected from the pressure sensors in SSDA configuration compared to the traditional Wheatstone bridge circuit. Preliminary experimental measurements, performed on individual transistors placed on the membrane, exhibit state-the-art sensitivity values (1.45mV/mbar).

In this paper, we want to present a simple and efficient numerical method for SHG analysis in one-dimensional photonic crystals (PhCs) based on full nonlinear system of equations. For solving the nonlinear SHG problem we used a simple method of finite elements coupled with fixed point iteration. Our model does not need additional analytic approximation compared with some existing methods, and it can be easily extended to study the SHG problem in two-dimensional photonic crystals. We used the FlexPDE Professional program to plot the diagrams varying the parameters. At the end we obtained two maximum intensities of the second harmonic wave within each high index layer, that being in contrast to the fundamental wave peak. This result can be found also in the literature. In addition, we have plotted the lattice using the Optiwave FDTD software and we observed the propagation of the field in time.

Two CO 2 sensing mechanisms, based on the Hard Soft Acids Bases (HSAB) and Bronsted-Lowry theories, are discussed and compared. They are evaluated by selecting amino groups-based coating layers, which are deposited on Surface Acoustic Wave (SAW) devices for CO 2 detection. Experimentally measured CO 2 sensitivities of different coating layers, such as polyallylamine (PAA), polyethyleneimine (PEI), nanocomposite matrix based on PAA-aminocarbon nanotubes and PEI-aminocarbon nanotubes, emeraldine, 4-sulfocalix[4]arene-doped polyaniline, matrix based emeraldine and carbonic anhydrase (PACA) are compared and evaluated according to their corresponding sensing mechanism.

The CO2 sensing performance of several coating layers deposited on piezoelectric devices (Surface and Bulk Acoustic wave - SAW/BAW) are discussed and compared. The layers are amino groups-based polymers and their selection was based on two principles: Hard Soft Acid Bases (HSAB) and Bronsted-Lowry. Experimentally measured CO2 frequency shifts and sensitivities of emeraldine, 4-sulfocalix[4]arene-doped polyaniline, matrix based emeraldine and carbonic anhydrase (PACA) are compared to previously reported results obtained for coatings such as: polyallylamine (PAA), polyethyleneimine (PEI), nanocomposite matrix based on PAA-aminocarbon nanotubes and PEI-aminocarbon nanotubes.

It is the purpose of this paper to present a novel generic concept for low drift chemical sensing which is applicable at micro and nanometer scale, based on a new, all-differential approach. At micrometer level, our principle is explained by means of surface acoustic wave (SAW) chemical sensing, while at nano level, we are using the resonant sensing principle to develop our genuine differential concept. Unlike the traditional differential approaches based on functionalized sensing layer in the sensing loop, and on a uncoated surface in the reference loop, our all differential concept provides a better response subtraction between the two paths, as the sensing loop consists of a functionalized sensing layer, as before, but, the reference loop consists of a functionalized non-sensing layer, with the same ageing and humidity behavior as the sensing layer. Twinned electronic reading is used for both loops, and thus all the common mode signals are subtracted in the differential reading, assuring the minimum base line drift of the sensor. Preliminary results of all differential sensor response to humidity and temperature variations are shown for the SAW sensors, with the sensor signal kept independent of their changes.

It is the purpose of this paper to present a novel generic concept for low drift chemical sensing which is applicable at micro and nanometer scale, based on a new, all-differential approach. At micrometer level, our principle is explained by means of surface acoustic wave (SAW) chemical sensing, while at nano level, we are using the resonant sensing principle to develop our genuine differential concept. Unlike the traditional differential approaches based on functionalized sensing layer in the sensing loop, and on a uncoated surface in the reference loop, our all differential concept provides a better response subtraction between the two paths, as the sensing loop consists of a functionalized sensing layer, as before, but, the reference loop consists of a functionalized non-sensing layer, with the same ageing and humidity behavior as the sensing layer. Twinned electronic reading is used for both loops, and thus all the common mode signals are subtracted in the differential reading, assuring the minimum base line drift of the sensor. Preliminary results of all differential sensor eliminating the effects of humidity and temperature variations are shown for the SAW sensors, with the sensor signal kept independent of their changes. Finally, the application of the novel concept for the humidity sensing with all differential resonant nanosensor is presented.

Keywords: e-CUBES Reference EPFL-CONF-174874 Record created on 2012-02-13, modified on 2017-05-10

This paper presents a finite element (FE) model for SAW gas sensors with polymer layers, taking into account not only the mass loading effect, but also the viscoelastic properties of polymer layers, including loss. The FE model considers both variations of layer density and thickness with absorbed gas concentration. The damped eigenvalue analysis allows the calculation of complex propagation constants. This is an improvement over previously published FE works in this field, e.g. [1], which considered only the frequency shift and neglected the attenuation.

The Hard Soft Acid Base (HSAB) theory is introduced as a new tool to select or design sensitive materials for carbon dioxide detection with SAW-BAW (Surface Acoustic Waves - Bulk Acoustic Waves) devices. According to HSAB, CO2 is hard acid, thus small organic or inorganic molecules, or polymers which can act as hard bases could be suitable candidates as sensing layers for carbon dioxide detection. As a consequence of this theory, we propose the following polymers as potential candidates for CO2 sensing: simple polyallylamine, N-substituted polyallylamine, polydiallylamine and polyvinylamine, and mixtures of these polymers. The SAW device coated with one of the selected polymers, polyallyamine, shows good sensitivity for CO2 concentration (in the range 500–5000 ppm), long term stability and repeatability.

This paper extends prior analysis of self - collimation effect in two dimensional photonic crystal structure patterned with a triangular lattice having hexagonal holes [1]. The equifrequency contours analysis is performed in order to determine the self - collimation effect frequency range for this structure. The routing of two self-collimated Gaussian beams travelling through a hexagonal photonic crystal, on the same optical layer is demonstrated. Using the unique advantage of allowing self-collimated beams to cross each other without coupling, one can devise structureless interconnects for photonic integrated circuits [2].

Two different designs of 2D photonic crystal lattices that exhibit large complete photonic band gaps have been recently proposed [1] : (1) honey-comb lattice with two different hole radii; (2) "tri-ellipse" pattern in a triangular lattice. We perform a full 3D analysis of guided and leaky modes in vertically symmetric slabs based on these lattices. Guided modes are obtained through the plane-wave expansion method (PWEM) with a vertical supercell. Leaky modes are obtained through a finite difference time domain (FDTD) analysis with a combination of Bloch and perfectly matched layers boundary conditions. The analysis is carried out for both even and odd modes with respect to the plane bisecting the slab. It turns out that the classical 2D effective index method predicts a false bandgap in odd modes for high-index-contrast photonic crystal slabs studied here.

Guided and leaky modes in asymmetric, hexagon-type, silicon-on-insulator (SOI) slabs are analyzed. Guided modes are obtained through the plane-wave expansion method (PWEM) in 3D with a vertical supercell. Leaky modes are obtained through the scattering matrix method (SMM) applied for the configuration known as "variable angle reflectance spectroscopy". The analysis is carried out along different symmetry directions (Γ-K and Γ-M) for TE and TM polarization of the incident plane wave. A complete picture of the modes in hexagon-type SOI slabs is obtained. This is useful in identifying the possible low-loss spectral windows that can be used for functional devices e.g. cavities and line defect waveguides.

A two dimensional photonic crystal superprism is presented in this paper. The constant (equi) frequency contours calculations are used in order to determine the superprism effect frequency range in a rectangular and hexagonal lattice photonic crystal. Through the Finite Difference Time Domain simulation of light propagation, we demonstrate a good performance regarding the resolution and the area of this demultiplexing device that can be used in photonic integrated circuits.