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ABSTRACT: An important condition for the development of surface wave integrated-acoustic devices is the ability to guide and control the propagation of the acoustic energy. This can be implemented by deposition of metallic "loading" channels on an anisotropic piezoelectric substrate. Deposition of such two parallel channels causes an effective coupling of acoustic energy from one channel to the other. A basic requirement for this coupling effect is the existence of the two basic modes: a symmetrical and a nonsymmetrical one. A mode map that shows the number of sustained modes as a function of the device parameters (i.e., channel width; distance between channels; material velocity; and acoustical exciting frequency) is presented. This kind of map can help significantly in the design process of such a device. In this paper we devise an advanced acoustical "Y" coupler with the ability to control its effective coupling by an externally applied voltage, thereby causing modulation of the output intensities of the signals.
Physica Scripta 11/2006; 38(4):534. · 1.20 Impact Factor
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ABSTRACT: Secondary electron emission (SEE) yield (δ) of ZnO films has been investigated. The films were deposited in an RF sputtering system, using RF power (W), argon pressure (p), partial O2 pressure (pO2), and substrate temperature (Ts) as parameters. The ratio x = O/Zn is an essential factor which determines δ of the ZnO films. Auger analyses have shown that excess (over-stoichiometric, x > 1) oxygen exists in ZnO films obtained at room temperature. For x > 1, the values of maximum SEE yield δm were found to be higher than those of the stoichiometric ZnO (obtained at Ts > 200°C). The highest value of δm(=4.4) was obtained for x = 1.7.
Physica Scripta 11/2006; 37(4):555. · 1.20 Impact Factor
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ABSTRACT: This paper introduces a deposition method to create a multilayered waveguide with alternating layers of high index of refraction contrast. A very thin Ag layer, practically transparent in the mid-IR radiation wavelengths of CO(2) and Er-YAG lasers, was created. This enabled a good contrast of the indices of refraction of silver/silver iodide. Theoretical calculations as well as experiments have shown that transmission was higher at these wavelengths for two pair layers, in comparison to one pair of silver/silver iodide. Windows of transmittance and small sensitivity to bending were demonstrated for those two pair layer waveguides. This method could be extended to an increased number of pairs to configure a true photonic band gap waveguide.
Optics Express 05/2004; 12(7):1341-52. · 3.59 Impact Factor
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ABSTRACT: The application of a room-temperature-operated distributed-feedback quantum cascade laser (DFB-QCL), coupled with a silica hollow waveguide for small-volume gas sensing is demonstrated. An internally silver-coated silica capillary, with a length of 4 m and an inner diameter of 700 μm simultaneously acts as waveguide and microcapillary gas cell. This configuration provides a well defined optical path length, while maintaining a small sample volume. Ethyl chloride gas was mixed with air and detected by attenuation of the emitted laser radiation at 971cm<sup>-1</sup> down to concentration levels of 5 ppm (v/v). With the current experimental setup a limit of detection of 0.5 ppm (v/v) has been achieved. The feasibility study shows that hollow fibres provide facile light guiding for QCLs over several metres and, therefore can be used for remote gas sensing or IR light delivery in medical applications.
IEE Proceedings - Optoelectronics 09/2003; · 0.71 Impact Factor
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ABSTRACT: The objective in this study is to continue the proposed mode model (Z. Menachem et al, Opt. Eng. vol. 41, pp. 2169-2180, 2002) in order to provide a numerical tool for calculation of the output fields and power density also in the case of flexible hollow waveguides. In this study, we supposed that the flexible toroidal waveguide consists of only two sections, having different radius of curvature (R1≠R2), in order to simplify the mathematical expressions. All the terms of the bending are taken into account in the calculations. Therefore the output fields are calculated also for intermediate radius of curvature (R =0.5 m, and R2=0.4 m) for the flexible waveguide. The longitudinal components of the fields are developed into a Fourier-Bessel series. The transverse components of the fields are expressed as functions of the longitudinal components in the Laplace plane and are obtained by using the inverse Laplace transform. The separation of variables is obtained by using the orthogonal-relations. The metal boundaries of the waveguides are modeled as a lossy dielectric media.
Electrical and Electronics Engineers in Israel, 2002. The 22nd Convention of; 01/2003
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ABSTRACT: Thin Ag-W films were prepared on Si (100) substrate and on metal (Ag and Co) seed layers by electroless technology for ULSI
applications. The thin film electrical and physical parameters were studied as a function of the film composition. The thin
film composition depends on the electroless bath formula. The role of the tungsten in silver matrix was studied via measurements
of the film microhardness and thermal stability as function of the composition. The Ag-W films, thicker than 200 nm, exhibited
a specific electrical resistivity of about 2μΩ* and a reflectivity larger than 90%. These films have not corroded in air at
temperatures up to 200°C (thermal stable). Therefore, we assume that silvertungsten films can be used for applications where
reliable conducting thin films is required, such as packaging and interconnects for microelectronics.
Journal of Electronic Materials 03/2001; 30(4):355-359. · 1.47 Impact Factor
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ABSTRACT: In this paper are presented the results of the study of Ag-W thin films deposited by ion beam sputtering (IBS) and electroless (El) technology on SiO<sub>2</sub>/Si substrates for MOS (Ag-W/SiO<sub>2</sub>/Si) capacitors. This is the first application of the Ag-W films for metallization and interconnects in microelectronics. From the C-V characteristics of capacitors, measured as deposited and annealed at temperatures up to 475°C, has resulted that Ag-W films may maintain normal C-V shape and low failures (less that 30%) for annealing at T〈400°C. The capacitors exhibited almost ideal C-V high frequency characteristics and flat band voltage near to zero. Using the Zerbst model and C-t characteristics of capacitors were obtained the values of lifetime (τ) and velocity of recombination (s). The generation lifetime and the recombination surface velocity were of the same order of those for similar structures with Cu, Co and Al metallization. Those results indicate that Ag-W layers are MOS technology compatible and can be used in microelectronics as a new interconnect and metallization material
Solid-State and Integrated-Circuit Technology, 2001. Proceedings. 6th International Conference on; 02/2001
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L Hvozdara,
S Gianordoli,
G Strasser,
W Schrenk,
K Unterrainer,
E Gornik,
C S Murthy,
M Kraft,
V Pustogow,
B Mizaikoff,
A Inberg, N Croitoru
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ABSTRACT: We demonstrate what we believe is the first application of the recently developed electrically pumped GaAs/AlGaAs quantum-cascade lasers in a spectroscopic gas-sensing system by use of hollow waveguides. Laser light with an emission maximum at 10.009 microm is used to investigate the mid-infrared absorption of ethene at atmospheric pressure. We used a 434-mm-long silver-coated silica hollow waveguide as a sensing element, which served as a gas absorption cell. Different mixtures of helium and ethene with known concentrations are flushed through the waveguide while the laser radiation that passes through the waveguide is analyzed with a Fourier-transform infrared spectrometer. The experimentally obtained discrete ethene spectrum agrees well with the calculated spectrum. A detection threshold of 250 parts per million is achieved with the current setup.
Applied Optics 01/2001; 39(36):6926-30. · 1.41 Impact Factor
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Microelectronics Reliability. 01/2001; 41:67-72.
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G. Golan,
E. Rabinovich,
A Inberg,
A. Axelevitch,
M. Oksman,
Y. Rosenwaks,
A. Kozlovsky,
P.J. Rancoita,
M. Rattagi,
A Seidman, N. Croitoru
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ABSTRACT: The structure, microhardness and deformation character for silicon detectors were investigated following a neutron irradiation, using optical and Atomic Force (AFM) microscopes. The results of these investigations have given an important contribution to the understanding of silicon damage process by neutron irradiation. It was shown that in the interval of neutron fluences 9.9×10<sup>10</sup>⩽Φ⩽3.12×10<sup>15</sup> n/cm <sup>2</sup> the damage is accumulative (from small punctual to large defects). The abrupt changes of microstructure together with the electrical and mechanical properties were found for Φ⩾10<sup>14 </sup> n/cm<sup>2</sup>. Different kinds of defects (dislocations and interstitials) and their complexes appeared under neutron irradiation. For all fluences the regions (“White” -“W”) with a microhardness smaller than in nonirradiated silicon were observed. Microhardness is larger in the regions where the concentration of dislocation loops is high. The “W”, regions have a small number of the dislocations loops, and single punctual defects were seen there using Atomic Force Microscope. The dislocation loops are placed in specific (“Black”-“B”) regions, which increase in size with the increase of neutron fluence due to a process of vacancies and interstitials accumulation
Microelectronics, 2000. Proceedings. 2000 22nd International Conference on; 02/2000
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ABSTRACT: Plastic hollow waveguides were used for non-contacting temperature measurements. Employing these fibres, the authors performed temperature measurements between room temperature and 120 degrees C, achieving good agreement with theoretically expected values. The temperature and spatial resolutions of the waveguides were measured. The temperature resolution was found to be 0.8 degrees C (fibre dimensions: internal diameter 2.4 mm, length 60 cm) and the spatial resolution was approximately equal to the inner diameter (ID) of the waveguide. The curvature loss of the waveguide increased with decreasing radii of curvature. It was also shown that waveguides with dielectric layer thicknesses of 0.2-0.6 mu m are suitable for radiometry at this temperature range.
Journal of Physics D Applied Physics 12/1998; 26(7):1036. · 2.54 Impact Factor
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ABSTRACT: Two types (plastic and fused silica) of waveguides suitable for transmitting and Er-YAG laser radiation were prepared and characterized. The temperature of several points on the external surface of the waveguides was measured. Optical parameters (transmission, focusing, misalignment) of the two types of waveguides were measured and compared. The importance of heating (due to losses) on the long time delivery performance is also shown.
Journal of Physics D Applied Physics 12/1998; 29(3):569. · 2.54 Impact Factor
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ABSTRACT: A novel type of flexible hollow waveguide that facilitates delivery of infrared radiation from source to treatment site, and made of polyimide tubes, was developed.
Polyimide tubes with flat internal wall and optimal conditions of deposition of guiding metal and dielectric layers were used to obtain low losses of radiation and high quality of beam shape.
Etching of the internal wall of polyimide tubes, high reflective metal (silver) layers and suitable dielectric layers (index of refraction and thickness) were deposited as guiding elements to obtain a waveguide suitable for infrared transmission.
Polyimide waveguides of very low attenuation (transmission of approximately 95% through 1 meter length) beam profile of variable shape as a function of bending radius and type of tbe, large delivered radiation power (more than 25 Watts), constant delivered power as a function of time (during more than 250 seconds), and very low divergence of the delivered beam (angle of divergence less than 1 degree), were obtained. The polyimide waveguides also are very flexible and may be bent to a radius of bending less than 5 cm. The polyimide plastic hollow waveguide is suitable for medical applications (chemical and physical stable and nontoxic).
The optical and mechanical parameters correspond with those requested for applications in medicine for infrared laser treatments or radiometric measurements (non-contact thermometry). Waveguides for applications in surgery are under preparation.
Journal of Clinical Laser Medicine & Surgery 05/1998; 16(2):127-33.
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ABSTRACT: We refined flexible waveguides previously developed for CO(2) and Er:YAG laser radiation to transmit free-electron-laser (FEL) radiation. One can tune this laser over several segments of the radiation spectrum. This laser has a high peak power of as much as 10 MW with pulse energy of as much as 100 mJ. We made the waveguides of either Teflon or fused-silica tubes internally coated with metal and dielectric layers. We optimized the internal coatings specifications for transmission of various radiation wavelengths in the mid-IR range and enabled transmission of high-peak radiation. We performed experiments in three major FEL sites in the United States over a more than 1-year period when we measured and examined various characteristics of transmission. We used the analysis of these experiments as feedback to further improve these waveguides. The good preliminary results encourage us to invest more effort to further develop these waveguides until a suitable waveguide is obtained for this type of laser and make possible its introduction to the medical field where its characteristics can be exploited in surgical applications.
Applied Optics 10/1997; 36(25):6289-93. · 1.41 Impact Factor
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ABSTRACT: Surface acoustic wave directional couplers have long been known in both microwave and integrated acoustic applications. Such couplers are ideal for integration in acoustical signal processing devices, such as modulators or switches. There are, however, very few publications concerning the frequency response of these devices. This article represents both experimental and theoretical studies on the frequency response of directional couplers, with and without a thin strip deposited in the gap between the main channels. The beam propagation method, used in integrated optics, was adapted for acoustical directional couplers. It enabled the analysis and prediction of the frequency response of these types of couplers. Calculations were performed for the channels and interdigital transducers in the frequency range of 50–90 MHz. By using proper dimensions of the couplers’ parameters, coupling efficiency for the higher part of the frequencies, in the receiver channel, was increased. This increase enables the selection of receiver frequencies and, therefore, a frequency channelizer could be developed. A thin strip between the main channels increases the coupling efficiency between the two channels and thereby reduces by about 30% the length of the coupler required for different frequency selections or conventional switches. This reduction makes it possible to obtain more compact devices with reduced losses. © 1996 American Institute of Physics.
Journal of Applied Physics 01/1997; · 2.17 Impact Factor
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ABSTRACT: Minimal invasive surgery (MIS) is the preferred method for
performing medical operations today due to its lower cost, fast healing,
and minimal post-operative pain and discomfort to the treated patients.
It is rapidly expanding with the development and miniaturization of
two-dimensional (2-D) and three-dimensional (3-D) endoscopic imaging
systems. Laser surgery has also proved itself to be a preferred tool of
operation over standard tools in a lot of the cases. Development of a
reliable flexible fiber or waveguide will enable surgeons to bring the
laser beam transcendoscopically within body cavities. It will combine
the endoscopy technique with the advantageous laser interaction with
tissue to create a powerful surgical tool which will be the ultimate
choice of operating procedure. A number of research groups have
suggested flexible waveguides for the mid-IR region between 2.5 and 11
μm, which contains very important and useful laser wavelengths and is
not covered by silica fibers. The chief goals for the development of
such delivery devices are summarized. The different solutions suggested
are broadly described and thoroughly analyzed for their performance and
potential
IEEE Journal of Selected Topics in Quantum Electronics 01/1997; · 3.78 Impact Factor
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ABSTRACT: Microhardness analysis of Diamond-Like Carbon (DLC) films deposited by PECVD, using R.F. generator was carried out. This analysis was realized by a standard tester PMT-3 which consists of a flat field optical microscope and a diamond stylus probe. Vickers indentation measurements were done with constant loads of: 10 g, 20 g, 30 g, 50 g, 60 g and 70 g in a continuous pressure. It was shown that microhardness results of the DLC thin films are strongly dependent on the methodological principles of the measurement technique and instrumentation. An iterations method was used in order to choose the correct load value. Every loading was accompanied with a metallographical control of the indentor's stamps quality. Best results were obtained for 10 g, 20 g and 30 g loads. The analysis is based on the empirical approach and the “cavity model” of the indentation hardness
Electrical and Electronics Engineers in Israel, 1996., Nineteenth Convention of; 12/1996
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ABSTRACT: Photoconductivity of doped amorphous diamond-like-carbon (a:DLC) films has not yet been studied because of strong recombination and short lifetime of excited free carriers. Obviously, high photoconductivity response of a:DLC films may lead to the development of photodevices based on this new material. The aim of this work was to investigate the influence of doping on the photoconductivity of a:DLC films. The a:DLC films were grown by the RF glow discharge technique using methane gas (CH<sub>4</sub>), with iodine as doping element. The deposition was made on silicon and glass substrates. The photoconductivity effect was measured using collateral structures. The concentration and bonding energy of the doping elements in a:DLC films was determined using X-ray photoelectron spectroscopy (XPS). This study has shown that iodine doping increased the photoconductivity σ<sub>ph</sub> and the decay time τ<sub>d</sub>. The measured data have contributed new information about iodine neutralization of the dangling bonds, which increase the lifetime of free carriers in a:DLC
Electrical and Electronics Engineers in Israel, 1996., Nineteenth Convention of; 12/1996
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ABSTRACT: Surface Acoustic Waves (SAW) directional couplers have long been
known in both microwave and integrated acoustic applications. However,
there have been very few publications concerning the frequency response
of these devices. This paper represents both experimental and
theoretical studies on the frequency response of directional couplers,
with and without a thin strip deposited in the gap, between the main
channels. Beam propagation method (BPM), adapted from integrated optics,
was used to analyze the frequency response of this type of couplers.
Calculations and measurements were performed in the frequency range of
50-90 MHz. By using proper dimensions of couplers parameters, the
efficiency of coupling for the higher part of the frequencies, in the
receiver channel, was increased. This increase enables the selection of
receiver frequencies and therefore, a frequency channelizer could be
developed. A thin strip between the main channels, increases the
coupling efficiency between the two channels and, therefore, reduces by
about 30% the length of the coupler required for different frequency
selections or conventional switches. This reduction makes it possible to
obtain more compact devices with reduced losses
Electrical and Electronics Engineers in Israel, 1996., Nineteenth Convention of; 12/1996
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ABSTRACT: Flexible plastic waveguides (FPW) were devised for the delivery of Er-YAG laser radiation. The FPW characteristics were studied under various conditions. In vitro studies were carried out to explore the drilling procedure on extracted teeth and the FPW-tissue mutual effects. The results which were obtained proved that the FPW as a delivery device might be a substitute hand applicator for the pneumatic turbine for drilling in teeth.
IEEE Transactions on Biomedical Engineering 11/1995; · 2.28 Impact Factor
