High Transmission Coefficient Research Articles

Plasmonic colour filters for CMOS image sensors

C colour filters in CMOS image sensors are made of dyes or pigments and exploit their particular absorption properties to produce different colours. Plasmonic colour filters are superior to conventional colour filters made of dyes and pigments, especially when the pixel size is reduced to a few microns in size. This is because the dyes or pigments based filters cannot be made much thinner than several hundred nanometres due to their low absorption coefficients as well as due to fabrication of each of the three dye filters for RGB colour schemes demands complex lithographic processes. In addition to these, dyes and pigments based filters are prone to colour cross talk at submicron scale. Colour filters based on plasmonic filters can overcome the above difficulties. Also, the plasmonic filters integrated w i t h CMOS image sensors are environmentally friendly compared to their toxic counterparts. Here, we present plasmonic colour filtersdesign based on localised surface plasmon resonances in aluminium nanodisks that are angle insensitive, polarization insensitive, inexpensive, compatible with existing CMOS technology and have high transmission coefficients.

Key comparison SIM.EM.RF-K5b.CL: scattering coefficients by broad-band methods, 2 GHz–18 GHz — type N connector

The first key comparison in microwave frequencies within the SIM (Sistema Interamericano de Metrología) region has been carried out. The measurands were the S-parameters of 50 ohm coaxial devices with Type-N connectors and were measured at 2 GHz, 9 GHz and 18 GHz. SIM.EM.RF-K5b.CL was the identification assigned and it was based on a parent CCEM key comparison named CCEM.RF-K5b.CL. For this reason, the measurements standards and their nominal values were selected accordingly, i.e. two one-port devices (a matched and a mismatched load) to cover low and high reflection coefficients and two attenuators (3dB and 20 dB) to cover low and high transmission coefficients. This key comparison has met the need for ensuring traceability in high-frequency measurements across America by linking SIM's results to CCEM. Six NMIs have participated in this comparison which was piloted by the Instituto Nacional de Tecnología Industrial (Argentina). A linking method of multivariate values was proposed and implemented in order to allow the linking of 2-dimensional results.KEY WORDS FOR SEARCHMain textTo reach the main text of this paper, click on Final Report. Note that this text is that which appears in Appendix B of the BIPM key comparison database kcdb.bipm.org/.The final report has been peer-reviewed and approved for publication by the CCEM, according to the provisions of the CIPM Mutual Recognition Arrangement (CIPM MRA).

Electrical and optical properties of nanosized films of doped zinc and indium oxides deposited by RF magnetron sputtering at room temperature

We have compared the electrical and optical properties of nanosized films of tin-doped indium oxide (ITO) and aluminum-doped zinc oxide (AZO) deposited on silicon and glass substrates by low-power RF magnetron sputtering at room temperature. Dependences of the resistivity and optical transmission coefficient of deposited oxides on the RF radiation power are presented. The plots of resistivity versus RF sputtering power for both oxides are nonlinear, with a minimum in the region of 50 W. For AZO, this minimum has been observed for the first time. The minimum value of resistivity for AZO is about 2.9 × 10−3 Ω cm and that for ITO is about 5.4 × 10−4 Ω cm. Both oxides are characterized by high optical transmission coefficients, close to 90% in a wavelength range of 500–1000 nm.

A High-Sensitivity Fully Passive Neurosensing System for Wireless Brain Signal Monitoring

A high-sensitivity, fully passive neurosensing system is presented for wireless brain signal monitoring. The proposed system is able to detect very low-power brain-like signals, viz. as low as $-$ 82 dBm (50 $\mu\hbox{V}_{\rm pp}$ ) at ${\rm f}_{\rm neuro}>\hbox{ 1 kHz}$ . It is also able to read emulated neural signals as low as $-$ 70 dBm (200 $\mu\hbox{V}_{\rm pp}$ ) at ${\rm f}_{\rm neuro}>\hbox{ 100 Hz}$ . This is an improvement of up to 22 dB in sensitivity as compared with previously reported neural signals. The system is comprised of an implanted neurosensor and an exterior interrogator. The neurosensor receives an external carrier signal and mixes it with the neural signals prior to retransmitting to the interrogator. Of importance is that the implanted neurosensor is fully passive and does not require a battery nor rectifier/regulator but is concurrently wireless for unobtrusive neurosensing with minimal impact to the individual's activity. To achieve this remarkable high sensitivity, the sensing system employed: 1) a subharmonic mixer using an anti-parallel diode pair; 2) a pair of implanted/interrogator antennas with high transmission coefficient $\vert{S}_{21}\vert$ ;and 3) a matching circuit between the implanted antenna and the mixer. This neurosensing system brings forward a new possibility of wireless neural signal detection using passive brain implants.

ATTENUATION OF SOLITARY WAVE BY PARAMETERIZED FLEXIBLE MANGROVE MODELS

The systematic laboratory investigation on tsunami attenuation by flexible mangrove models was performed in order to improve the knowledge on tsunami-coastal forest interaction. A sophisticated parameterization method, based on structural and bio-mechanical properties of a mature mangrove (Rhizophora sp.), was developed for the construction of the mangrove models under assumption of stiff and flexible structure. The forest model examined in the laboratory experiments consisted of the selected flexible mangrove models, arranged in different configurations, which was impacted by a tsunami-like solitary wave of varying height, propagating in different water depths. Based on the envelopes of max. wave height and wave forces induced on single tree models, wave evolution modes were determined to identify the source of wave attenuation. The results indicate the dependence of wave transmission on the observed wave evolution modes and relative forest width: the highest transmission coefficient is attributed to nonbreaking waves (ca. 0.78 and 0.55 for forest width of 0.75 and 3.0 m, respectively), while the lowest transmission coefficient corresponds to wave breaking in front of/in the forest model (ca. 0.5 and 0.3 for forest width of 0.75 and 3.0 m, respectively).

Homogenization of fluid–porous interface coupling in a biconnected fractured media

The modelization of mass transfer through biconnected fractured porous media is studied by homogenizing the coupling between the Darcyan percolation and the viscous Stokes flow on their interface governed by the Beavers–Joseph law. The case of high transmission coefficients is considered. The asymptotic behaviour is completely described with the help of the solutions of some specific local problems and of a nonhomogeneous Neumann problem defined by the effective permeability tensor.

Quantitative Analysis of the Optical Losses in CZTS Thin-Film Semiconductors

For the first time, a quantitative approach was carried out to model the optical losses in several Cu2 ZnSnS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub> (CZTS) based thin-film heterojunction solar cells having different window and buffer layers. The modeling indicates that the heterojunction of glass/FTO/TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> /In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /CZTS has a lower reflection and higher transmission coefficient than glass/FTO/In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> /CZTS and conventional glass/FTO/CdS/CZTS structures. These optical losses at the interfaces (reflection) and inside the thickness (absorption) of stacked layers were calculated based on the known optical constants such as refractive index and extinction coefficient. While TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> windowed device resulted in a promising high short-circuit current and energy conversion efficiency, the In <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> S <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> windowed and conventional CdS windowed devices showed to be less efficient. We compared our theoretical analysis with the practical reports given for such structures in the literature. Further studies are required to reduce the reflection and absorption losses of CZTS structures in practice. So far, the overall performance parameters (e.g., Jsc and η) are much less than our theoretical estimations. The size of the TiO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> nanoparticles on the layer is about 100 nm.

Effect of Different Current Densities in the Studies of 1/f noise on the Thin Films of Silver

Abstract: Silver (Ag) thin films are having remarkable characteristics. They have found extensive applications in electronic and optical devices. Silver thin films have potential applications in ultra-high density optical non-volatile memories, transparent electrodes and in fluorescence imaging. Measurements of nonlinear properties are very interesting from the point of the view of optoelectronic and all optical switches. Hence these films are studied in the present work. 1/f noise and nonlinear effects in Silver thin films for different current densities on varying the thickness of the films, at room temperature are studied. The specific dependence of 1/f noise on the thickness of the film, the effect of current densities on 1/f noise for the films of various thicknesses (430A o to 1180A o ) has been investigated. It is noticed that, for a constant current, the thickness of the film leads to an increase of 1/f noise.1/f noise plays an important role in choosing frequency band in which a device can be effectively used. Silver thin films are regarded as a material with many attracting properties such as good conduction, high transmission coefficient etc. It is specially used in optoelectronic devices.

Structural, optical and electrical properties of TiO2 thin films synthesized by sol–gel technique

The influence of annealing temperature on the structure, optical and electrical property of TiO thinfilms with (101) preferential orientation were deposited on glass substrates by sol–gel technique has beenstudied. As-deposited films were amorphous, and the XRD studies showed that the formation of anatase phasewas initiated at annealing temperature close to 400 °C. The grain size of the film annealed at 550 °C was about22 nm. The transmission spectra, recorded in the UV visible range reveal a relatively high transmissioncoefficient (~70%) in the obtained films. The transmittance data analysis indicates that the optical band gap (E)is closely related to the annealing temperature, an indirect band gap ranging from 3.43 eV to 3.04 eV wasdeduced. The electrical resistivity measurement that were carried out in function of the annealing temperature showed a sharp decrease in resistivity was found to be 0.0802 .cm.2g

Wave damping by a vertical porous structure placed near and away from a rigid vertical wall

Damping of water waves by a vertical porous structure placed at some distance from a vertical wall is investigated within the framework of linear water wave theory. The rectangular porous structure is placed on a small rectangular elevation. An incident wave of small amplitude propagates through the structure – some portion gets reflected back while some portion gets transmitted to a third region bounded vertically by a rigid wall which is considered to be at a distance near the porous structure, and also away from the wall at a large distance as a separate case. Boundary value problems are set up in all three regions and, by using the matching conditions along the vertical boundaries, a system of linear equations is deduced. The roots of the relevant dispersion relation are used in setting up the system of equations. The overall scattering phenomenon is studied with respect to different relevant parameters. The dependence of the coefficients on the thickness (width) of the porous structure is investigated for different numbers of modes and porosity. It is observed that, except for the case when the porous structure is thin, the reflection and transmission coefficients give rise to values as expected. In the case, when the rigid wall is nearer to the structure, the reflection coefficient decreases rapidly for a thin structure and converges for all numbers of evanescent modes afterwards. The transmission coefficient also decreases as the width increases, ultimately converging and vanishing for a wide structure. When the wall is at a large distance away from the structure, the behavior of both the reflection and transmission coefficients remain the same. For both cases of the wall being nearer and away from the structure, higher porosity gives rise to lower reflection coefficients and higher transmission coefficients. However, the transmission coefficients converge and vanish when the porous structure is very wide. We also discuss the energy loss against the width of the porous structure for different values of number of modes and porosity. Irrespective of the positioning of the rigid wall, we observe that for higher values of porosity, energy loss is more pronounced when the structure is not thin, whereas energy loss is same for all numbers of modes. All our observations are supported by graphs. Good agreement of our result with earlier results justifies our model.

Allee Effect from Parasite Spill-Back

The exchange of native pathogens between wild and domesticated animals can lead to novel disease threats to wildlife. However, the dynamics of wild host-parasite systems exposed to a reservoir of domesticated hosts are not well understood. A simple mathematical model reveals that the spill-back of native parasites from domestic to wild hosts may cause a demographic Allee effect in the wild host population. A second model is tailored to the particulars of pink salmon (Oncorhynchus gorbuscha) and salmon lice (Lepeophtheirus salmonis), for which parasite spill-back is a conservation and fishery concern. In both models, parasite spill-back weakens the coupling of parasite and wild host abundance-particularly at low host abundance-causing parasites per host to increase as a wild host population declines. These findings show that parasites shared across host populations have effects analogous to those of generalist predators and can similarly cause an unstable equilibrium in a focal host population that separates persistence and extirpation. Allee effects in wildlife arising from parasite spill-back are likely to be most pronounced in systems where the magnitude of transmission from domestic to wild host populations is high because of high parasite abundance in domestic hosts, prolonged sympatry of domestic and wild hosts, a high transmission coefficient for parasites, long-lived parasite larvae, and proximity of domesticated populations to wildlife migration corridors.

Photocurrent Calculation of Intersubband Transitions to Continuum-Localized States in GaAs/AlGaAs Multiquantum Wells for Mid-Infrared Photodetector

In this paper, we propose a system based on GaAs heterostructure where it is possible to generate photocurrent with mid-infrared radiation. This system is based on a central quantum well (CQW) embedded in a superlattice. Because of the CQW, which acts as a defect, there are localized states between the mini-bands in the continuum of the conduction band. Unlike the usual systems where the final states are delocalized, the oscillator strength due to the transitions between electrons occupying the ground-state to these continuum-localized states is enhanced. An applied electrical bias mixes the mini-band states with the localized state in the continuum, and due to the combined effects of strong oscillator strength and high transmission coefficients, narrow and sharp peaks are observed in the photocurrent when exciting these final states. We calculate and present results of the absorption and photocurrent for a system built to operate at 4.1 μm and discuss their dependence with the bias applied to the system and with the intensity of the incident radiation.

Thin-form birefringence quarter-wave plate for lower terahertz range based on silicon grating

We have developed a thin quarter-wave plate (QWP) operating at low terahertz frequency of 0.51 THz by etching micro-grating on a silicon substrate. The grating period is 30 μm, and the etching depth is 156 μm. Stokes parameters are used to characterize the QWP. The QWP shows a high transmission coefficient of 0.93 and a low polarization dependent loss (PDL) of 1.4 dB at 0.51 THz.

Plasmonic waves allow perfect transmission through sub-wavelength metallic gratings

We investigate the transmission properties of a metallic layer with narrow slits. Recent measurements and numerical calculations concerning the light transmission through metallic sub-wavelength structures suggest that an unexpectedly high transmission coefficient is possible. We analyze the time harmonic Maxwell's equations in the $H$-parallel case for a fixed incident wavelength. Denoting by $\eta>0$ the typical size of the complex structure, effective equations describing the limit $\eta\to 0$ are derived. For metallic permittivities with negative real part, plasmonic waves can be excited on the surfaces of the channels. When these waves are in resonance with the height of the layer, the result can be perfect transmission through the layer.

Inertial likelihood maximization for reaction coordinates with high transmission coefficients

For bilinearly coupled oscillator models, we examine the statistical relationship between transmission coefficients and committor distribution variances for reaction coordinates obtained by likelihood maximization. Transmission coefficients usually but not always increase as committor distributions narrow for the original version of likelihood maximization. We propose a new inertial version of likelihood maximization that uses velocity information to optimize purely configuration dependent coordinates. The coordinates from inertial likelihood maximization have higher transmission coefficients than coordinates from the original likelihood maximization procedure. Inertial likelihood maximization should be useful for understanding mechanisms of inertial reactions from atomistic simulations.

진공유리의 설계 조건에 따른 단열 성능 연구

Recently, the low-emissivity glass has been used to reduce the energy loss through building windows. However, it simply reduces the inflow of solar rays and has a relatively high heat transmission coefficient. To solve the problems, a high-efficiency vacuum glazing has been under development but it has not been actively used due to its high price and insufficient performance. In this paper, the effects of internal pressure, pillar (spacer) height, pillar diameter, pillar interval, emissivity etc. on the performance of vacuum glazing have been analyzed with three-dimensional computational fluid dynamics and structural analysis. As a result, the performance of vacuum glazing was predicted more accurately and major factors that determine the performance of vacuum glazing were optimized.

Influence of Low Temperature Annealing on Structure and Photoelectric Properties of MgZnO Thin Films

Structural and optical properties of MgxZn1-xO (x=0.23) thin films grown by radio frequency (R.F.) magnetron sputtering and annealed with different temperature (from 100°C to 400°C) are reported. The films were single-phase, highly c-axis oriented and wurtzite structure. The transmission spectra, recorded in the visible range, reveal a high transmission coefficient (about 95 %) in the obtained films. Besides, when the annealing temperature is 100°C, the crystalline grains are smooth, compact and uniformly distributed. As the annealing temperature increases from 100°C to 400°C, the crystalline grains get larger, but the annealing temperature does not influence optical transmittance obviously.

Switching behavior of a nonlinear Mach–Zehnder interferometer with exponentially saturable nonlinearity

Using beam propagation method, we investigated the switching behavior of a nonlinear Mach-Zehnder interferometer (NMZI). The focus of the present investigation was exponentially saturable type nonlinearity of the NMZI. The results were compared with the results of NMZIs with saturable type nonlinearity. NMZIs with both types of nonlinearity offer stable on and off states; however, exponentially saturable nonlinearity proves to be much better, as NMZIs with this type of nonlinearity offer a stable on state with higher transmission coefficient (i.e., with lower device loss) compared to those with saturable nonlinearity. Moreover, the stable on state could be achieved at much lower power levels. © 2012 Society of Photo-Optical Instrumentation Engineers (SPIE). (DOI: 10.1117/1.OE.51 .7.074604)

Design and analysis of thermally tunable liquid-crystal-filled microstructured polymer optical fiber

A highly tunable bandgap-guiding microstructured polymer optical fiber (mPOF) is designed by infiltrating the cladding air holes with a liquid crystal. Bandgap is blue shifted as temperature is increased. A high thermal tuning sensitivity of -5.5 nm/℃ is achieved at the long-wavelength edge of the bandgap. Mode properties and effective mode area of the fundamental mode are investigated by using the full-vector finite element method. The designed fiber has a large effective area and high power transmission coefficient between the index guiding modes and the bandgap guiding modes. Our results provide theoretical references for applications of mPOF in sensing and tunable fiber-optic devices.

Structural and Optical Properties of CdS Thin Films Grown by Sputtering

Cadmium sulfide (CdS) thin films with (111) preferential orientation were grown on glass substrates at room temperature by radio frequency (R.F.) magnetron sputtering. The structural and optical properties of CdS films have been investigated by X-ray diffraction, Scanning Electron Microscope micrographs, PL spectra and transmittance spectra. The grain sizes have been evaluated. The transmission spectra of the obtained films reveal a relatively high transmission coefficient (80%) in the visible range. All these results show that the grain sizes increased while the optical band gap decreased with increasing the thickness of CdS films.