Search results for "Transducer"
showing 10 items of 173 documents
Multiobjective optimization of an ultrasonic transducer using NIMBUS
2005
The optimal design of an ultrasonic transducer is a multiobjective optimization problem since the final outcome needs to satisfy several conflicting criteria. Simulation tools are often used to avoid expensive and time-consuming experiments, but even simulations may be inefficient and lead to inadequate results if they are based only on trial and error. In this work, the interactive multiobjective optimization method NIMBUS is applied in designing a high-power ultrasonic transducer. The performance of the transducer is simulated with a finite element model, and three design goals are formulated as objective functions to be minimized. To find an appropriate compromise solution, additional pr…
Humidity Insensitive Conductometric Sensors for Ammonia Sensing
2014
Interest in molecular materials has been driven in large part by their various and prosperous applications, especially in the domain of organic electronics, where they offer many advantages as well as alternative approaches compared to their inorganic counterparts. Most of conductometric transducers are resistors[[ and transistors[[[, but rarely diodes[6]. In our laboratory, we designed and characterized new molecular material based devices. Molecular Semiconductor Doped Insulator (MSDI) heterojunctions were built around a heterojunction between a Molecular Semiconductor (MS) and a Doped Insulator (DI)[7][8]. This new device exhibits interesting electronic properties that allow ammonia sens…
Tunable chirped fibre Bragg grating device controlled by variable magnetic fields
2002
A novel dynamic chirping fibre Bragg grating device based on a magnetic field applied to a magnetostrictive transducer capable of tuning its dispersion is presented. Chirping ranges up to 300 ps/nm have been demonstrated, which are suitable for several applications such as tunable transversal filtering and dynamic dispersion compensation.
Tunable dispersion device based on a tapered fiber Bragg grating and nonuniform magnetic fields
2003
We present a new variable dispersion device based on tuning the chirp of a tapered fiber Bragg grating by means of a magnetic transducer. By using a nonuniform magnetic field, we demonstrate a 188-472-ps/nm dispersion tuning range, suitable for tunable radio-frequency filters and dispersion compensation, among others.
Electrically tunable photonic true-time-delay line
2010
We present a new application of the acousto-optic superlattice modulation of a fiber Bragg grating based on the dynamic phase and group delay properties of this fiber-optic component. We demonstrate a tunable photonic true-time-delay line based on the group delay change of the light reflected from the grating sidebands. The delay is electrically tuned by adjusting the voltage applied to a piezoelectric transducer that generates the acoustic wave propagating along the grating. In our experiments, a true-time delay of 400 ps is continuously adjusted (300 ps within the 3 dB amplitude range of the first sideband), using a 12 cm long uniform grating.
Assessment of the fundamental flexural guided wave in cortical bone by an ultrasonic axial-transmission array transducer
2013
Abstract The fundamental flexural guided wave (FFGW), as modeled, for example, by the A0 Lamb mode, is a clinically useful indicator of cortical bone thickness. In the work described in this article, we tested so-called multiridge-based analysis, based on the crazy climber algorithm and short-time Fourier transform, for assessment of the FFGW component recorded by a clinical array transducer featuring a limited number of elements. Methods included numerical finite-element simulations and experiments in bone phantoms and human radius specimens ( n = 41). The proposed approach enabled extraction of the FFGW component and determination of its group velocity. This group velocity was in good ag…
The multimodal detection as a tool for molecular material-based gas sensing
2013
Abstract The adsorption of a target gas on a material induces a change in several physical characteristics, such as the dielectric constant, the work function or the conductivity. The use of different transducers sensitive to the variation of these parameters appears to be a relevant methodology worthy of investigation. In the field of sensors, molecular materials present interesting and potentially valuable features as sensing elements for real gas sensor applications. In this article, we review the different types of conductimetric transducers and also show how a molecular material-based microwave transducer can be used for gas sensing. Among conductimetric transducers, resistors have bee…
Photo-acoustic phase-delayed excitation of guided waves in coated bone phantoms
2013
Photo-acoustic skeletal quantitative ultrasound enables assessment of the fundamental flexural guided wave (FFGW) propagating in bone. This mode, consistent with the F(1,1) tube mode can now be measured through a coating of soft tissue. Interference due to ultrasound propagation in the soft tissue surrounding the bone is reduced by using phase-delayed ultrasound excitation. Photo-acoustic phase-delayed excitation was done on five axisymmetric bone phantoms (1-5 mm wall thickness), coated by a 5 mm thick soft-tissue mimicking layer. A fiber head comprising a linear array of four optical fibers (400 μm diameter), illuminated by pulsed laser diodes (905 nm wavelength) generated ultrasound. Thi…
Nonlinear photon-assisted tunneling transport in optical gap antennas.
2014
International audience; We introduce strongly coupled optical gap antennas to interface optical radiation with current-carrying electrons at the nanoscale. The transducer relies on the nonlinear optical and electrical properties of an optical gap antenna operating in the tunneling regime. We discuss the underlying physical mechanisms controlling the conversion involving d-band electrons and demonstrate that a simple two-wire optical antenna can provide advanced optoelectronic functionalities beyond tailoring the electromagnetic response of a single emitter. Interfacing an electronic command layer with a nanoscale optical device may thus be facilitated by the optical rectennas discussed here.
Nanoassembled plasmonic-photonic hybrid cavity for tailored light-matter coupling.
2010
We propose and demonstrate a hybrid cavity system in which metal nanoparticles are evanescently coupled to a dielectric photonic crystal cavity using a nanoassembly method. While the metal constituents lead to strongly localized fields, optical feedback is provided by the surrounding photonic crystal structure. The combined effect of plasmonic field enhancement and high quality factor (Q approximately 900) opens new routes for the control of light-matter interaction at the nanoscale.