Study of transmission line attenuation in broad band millimeter wave frequency range

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pandya, Hitesh Kumar B.; Austin, M. E.; Ellis, R. F.

2013-10-15

Broad band millimeter wave transmission lines are used in fusion plasma diagnostics such as electron cyclotron emission (ECE), electron cyclotron absorption, reflectometry and interferometry systems. In particular, the ECE diagnostic for ITER will require efficient transmission over an ultra wide band, 100 to 1000 GHz. A circular corrugated waveguide transmission line is a prospective candidate to transmit such wide band with low attenuation. To evaluate this system, experiments of transmission line attenuation were performed and compared with theoretical loss calculations. A millimeter wave Michelson interferometer and a liquid nitrogen black body source are used to perform all the experiments. Atmosphericmore » water vapor lines and continuum absorption within this band are reported. Ohmic attenuation in corrugated waveguide is very low; however, there is Bragg scattering and higher order mode conversion that can cause significant attenuation in this transmission line. The attenuation due to miter bends, gaps, joints, and curvature are estimated. The measured attenuation of 15 m length with seven miter bends and eighteen joints is 1 dB at low frequency (300 GHz) and 10 dB at high frequency (900 GHz), respectively.« less

FIBER AND INTEGRATED OPTICS: Emission properties of graded-index corrugated waveguides with a metal or semiconductor coating

NASA Astrophysics Data System (ADS)

Ataya, B. A.; Osovitskiĭ, A. N.

1992-02-01

A numerical method was used to investigate the emission of TE-polarized light from a graded-index corrugated waveguide coated with a metal or semiconductor and either with or without a buffer layer. The main emission characteristics of these systems were analyzed. In the case of metallized dielectric structures an optimal corrugation depth was established for which the emitted power is a maximum. It was found that when the parameters of a structure with a buffer layer were correctly chosen and a highly reflective metal coating was used, practically all the power in the waveguide wave could be emitted along a specified direction. A structure with a buffer layer and an aluminum coating was investigated experimentally.

Corrugated Waveguide Mode Content Analysis Using Irradiance Moments

PubMed Central

Jawla, Sudheer K.; Shapiro, Michael A.; Idei, Hiroshi; Temkin, Richard J.

2015-01-01

We present a novel, relatively simple method for determining the mode content of the linearly polarized modes of a corrugated waveguide using the moments of the intensity pattern of the field radiated from the end of the waveguide. This irradiance moment method is based on calculating the low-order irradiance moments, using measured intensity profiles only, of the radiated field from the waveguide aperture. Unlike the phase retrieval method, this method does not use or determine the phase distribution at the waveguide aperture. The new method was benchmarked numerically by comparison with sample mode mixtures. The results predict less than ±0.7% error bar in the retrieval of the mode content. The method was also tested using high-resolution experimental data from beams radiated from 63.5 mm and 19 mm corrugated waveguides at 170 and 250 GHz, respectively. The results showed a very good agreement of the mode content retrieved using the irradiance moment method versus the phase retrieval technique. The irradiance moment method is most suitable for cases where the modal power is primarily in the fundamental HE11 mode, with <8% of the power in high-order modes. PMID:25821260

Commissioning of inline ECE system within waveguide based ECRH transmission systems on ASDEX upgrade

NASA Astrophysics Data System (ADS)

Bongers, W. A.; Kasparek, W.; Doelman, N.; van den Braber, R.; van den Brand, H.; Meo, F.; de Baar, M. R.; Amerongen, F. J.; Donné, A. J. H.; Elzendoorn, B. S. Q.; Erckmann, V.; Goede, A. P. H.; Giannone, L.; Grünwald, G.; Hollman, F.; Kaas, G.; Krijger, B.; Michel, G.; Lubyako, L.; Monaco, F.; Noke, F.; Petelin, M.; Plaum, B.; Purps, F.; ten Pierik, J. G. W.; Schüller, C.; Slob, J. W.; Stober, J. K.; Schütz, H.; Wagner, D.; Westerhof, E.; Ronden, D. M. S.

2012-09-01

A CW capable inline electron cyclotron emission (ECE) separation system for feedback control, featuring oversized corrugated waveguides, is commissioned on ASDEX upgrade (AUG). The system is based on a combination of a polarization independent, non-resonant, Mach-Zehnder diplexer equipped with dielectric plate beam splitters [2, 3] employed as corrugated oversized waveguide filter, and a resonant Fast Directional Switch, FADIS [4, 5, 6, 7] as ECE/ECCD separation system. This paper presents an overview of the system, the low power characterisation tests and first high power commissioning on AUG.

Planar spoof plasmonic ultra-wideband filter based on low-loss and compact terahertz waveguide corrugated with dumbbell grooves.

PubMed

Zhou, Yong Jin; Yang, Bao Jia

2015-05-10

Although subwavelength planar terahertz (THz) plasmonic devices can be implemented based on planar spoof surface plasmons (SPs), they still suffer from a little high propagation loss. Here the dispersion and propagation characteristics of the spoof plasmonic waveguide composed of double metal strips corrugated with dumbbell shaped grooves have been investigated. It has been found that much lower propagation loss and longer propagation length can be achieved based on the waveguide compared with the conventional spoof plasmonic waveguide with rectangular grooves. Moreover, the waveguide can implement a decrease in size of about 22%. An ultra-wideband THz plasmonic filter for planar circuits has been demonstrated based on the proposed waveguide. The experimental verification at the microwave frequency has been conducted by scaling up the geometry size of the filter.

Optimization studies of the ITER low field side reflectometer.

PubMed

Diem, S J; Wilgen, J B; Bigelow, T S; Hanson, G R; Harvey, R W; Smirnov, A P

2010-10-01

Microwave reflectometry will be used on ITER to measure the electron density profile, density fluctuations due to MHD/turbulence, edge localized mode (ELM) density transients, and as an L-H transition monitor. The ITER low field side reflectometer system will measure both core and edge quantities using multiple antenna arrays spanning frequency ranges of 15-155 GHz for the O-mode system and 55-220 GHz for the X-mode system. Optimization studies using the GENRAY ray-tracing code have been done for edge and core measurements. The reflectometer launchers will utilize the HE11 mode launched from circular corrugated waveguide. The launched beams are assumed to be Gaussian with a beam waist diameter of 0.643 times the waveguide diameter. Optimum launcher size and placement are investigated by computing the antenna coupling between launchers, assuming the launched and received beams have a Gaussian beam pattern.

Performance Analysis of the ITER Plasma Position Reflectometry (PPR) Ex-vessel Transmission Lines

NASA Astrophysics Data System (ADS)

Martínez-Fernández, J.; Simonetto, A.; Cappa, Á.; Rincón, M. E.; Cabrera, S.; Ramos, F. J.

2018-03-01

As the design of the ITER Plasma Position Reflectometry (PPR) diagnostic progresses, some segments of the transmission line have become fully specified and estimations of their performance can already be obtained. This work presents the calculations carried out for the longest section of the PPR, which is in final state of design and will be the main contributor to the total system performance. Considering the 88.9 mm circular corrugated waveguide (CCWG) that was previously chosen, signal degradation calculations have been performed. Different degradation sources have been studied: ohmic attenuation losses for CCWG; mode conversion losses for gaps, mitre bends, waveguide sag and different types of misalignments; reflection and absorption losses due to microwave windows and coupling losses to free space Gaussian beam. Contributions from all these sources have been integrated to give a global estimation of performance in the transmission lines segments under study.

Characterization of low-frequency acoustic wave propagation through a periodic corrugated waveguide

NASA Astrophysics Data System (ADS)

Jiang, Changyong; Huang, Lixi

2018-03-01

In this paper, a periodic corrugated waveguide structure is proposed, and its unit-cell is analyzed by the wave finite element method. In low-frequency range, the unit-cell is treated as an equivalent fluid through a homogenization process, and the equivalent acoustic parameters are obtained, which are validated by finite structure simulations and experiments. The proposed structure is shown to add tortuosity to the waveguide, hence higher equivalent fluid density is achieved, while the system elastic modulus remains unchanged. As a result, the equivalent speed of sound is smaller than normal air. The application of such change of speed of sound is demonstrated in the classic quarter-wavelength resonator based on the corrugated waveguide, which gives a lower resonance frequency with the same side branch length. When the waveguide is filled with porous materials, the added tortuosity enhances the broadband, low-frequency sound absorption by increasing the equivalent mass without bringing in excess damping, the latter being partly responsible for the poor performance of usual porous materials in the low-frequency region. Therefore, the proposed structure provides another dimension for the design and optimization of porous sound absorption materials.

High-efficiency surface plasmonic polariton waveguides with enhanced low-frequency performance in microwave frequencies.

PubMed

Zhang, Dawei; Zhang, Kuang; Wu, Qun; Ding, Xumin; Sha, Xuejun

2017-02-06

In this paper, a planar waveguide based on spoof surface plasmon polaritons (SSPPs) with metals on both sides of the corrugated strip as grounds is firstly proposed in microwave region. Simple and efficient conversion between guided waves and SSPPs is realized by gradient corrugated strip with grounds on both sides. Compared with plasmonic waveguide with flaring ground [Laser Photonics Rev. 8, 146 (2014)], the addition of grounds suppresses the radiation loss effectively and improves the low-frequency performance with tighter field confinement, which leads to a wider operating bandwidth. Moreover, as the asymptotic frequency of SSPPs decreasing, the confinement of SSPPs is further enhanced by a defected ground structure (DGS), which is achieved by the periodic grooves symmetrical to those on the corrugated strip. Therefore, miniaturization of the proposed waveguide can be realized. Measured results validate both high efficiency of momentum and impedance matching and enhanced performance in the region of lower frequencies with the wave vectors close to those in free space. Such results have significant values in plasmonic functional devices and integrated circuits in microwave frequencies.

A comparative study of corrugated horn design by evolutionary techniques

NASA Technical Reports Server (NTRS)

Hoorfar, A.

2003-01-01

Here an evolutionary programming algorithm is used to optimize the pattern of a corrugated circular horn subject to various constraints on return loss, antenna beamwidth, pattern circularity, and low cross polarization.

Compact waveguide circular polarizer

DOEpatents

Tantawi, Sami G.

2016-08-16

A multi-port waveguide is provided having a rectangular waveguide that includes a Y-shape structure with first top arm having a first rectangular waveguide port, a second top arm with second rectangular waveguide port, and a base arm with a third rectangular waveguide port for supporting a TE.sub.10 mode and a TE.sub.20 mode, where the end of the third rectangular waveguide port includes rounded edges that are parallel to a z-axis of the waveguide, a circular waveguide having a circular waveguide port for supporting a left hand and a right hand circular polarization TE.sub.11 mode and is coupled to a base arm broad wall, and a matching feature disposed on the base arm broad wall opposite of the circular waveguide for terminating the third rectangular waveguide port, where the first rectangular waveguide port, the second rectangular waveguide port and the circular waveguide port are capable of supporting 4-modes of operation.

Bending Tests of Circular Cylinders of Corrugated Aluminum-alloy Sheet

NASA Technical Reports Server (NTRS)

Buckwalter, John C; Reed, Warren D; Niles, Alfred S

1937-01-01

Bending tests were made of two circular cylinders of corrugated aluminum-alloy sheet. In each test failure occurred by bending of the corrugations in a plane normal to the skin. It was found, after analysis of the effect of short end bays, that the computed stress on the extreme fiber of a corrugated cylinder is in excess of that for a flat panel of the same basic pattern and panel length tested as a pin-ended column. It is concluded that this increased strength was due to the effects of curvature of the pitch line. It is also concluded from the tests that light bulkheads closely spaced strengthen corrugated cylinders very materially.

Distributed-feedback Terahertz Quantum-cascade Lasers with Laterally Corrugated Metal Waveguides

NASA Technical Reports Server (NTRS)

Williams, Benjamin S.; Kumar, Sushil; Hu, Qing; Reno, John L.

2005-01-01

We report the demonstration of distributed-feedback terahertz quantum-cascade lasers based on a first-order grating fabricated via a lateral corrugation in a double-sided metal ridge waveguide. The phase of the facet reflection was precisely set by lithographically defined facets by dry etching. Single-mode emission was observed at low to moderate injection currents, although multimode emission was observed far beyond threshold owing to spatial hole burning. Finite-element simulations were used to calculate the modal and threshold characteristics for these devices, with results in good agreement with experiments.

Low-Gain Circularly Polarized Antenna with Torus-Shaped Pattern

NASA Technical Reports Server (NTRS)

Amaro, Luis R.; Kruid, Ronald C.; Vacchione, Joseph D.; Prata, Aluizio

2012-01-01

The Juno mission to Jupiter requires an antenna with a torus-shaped antenna pattern with approximately 6 dBic gain and circular polarization over the Deep Space Network (DSN) 7-GHz transmit frequency and the 8-GHz receive frequency. Given the large distances that accumulate en-route to Jupiter and the limited power afforded by the solar-powered vehicle, this toroidal low-gain antenna requires as much gain as possible while maintaining a beam width that could facilitate a +/-10deg edge of coverage. The natural antenna that produces a toroidal antenna pattern is the dipole, but the limited approx. = 2.2 dB peak gain would be insufficient. Here a shaped variation of the standard bicone antenna is proposed that could achieve the required gains and bandwidths while maintaining a size that was not excessive. The final geometry that was settled on consisted of a corrugated, shaped bicone, which is fed by a WR112 waveguide-to-coaxial- waveguide transition. This toroidal low-gain antenna (TLGA) geometry produced the requisite gain, moderate sidelobes, and the torus-shaped antenna pattern while maintaining a very good match over the entire required frequency range. Its "horn" geometry is also low-loss and capable of handling higher powers with large margins against multipactor breakdown. The final requirement for the antenna was to link with the DSN with circular polarization. A four-layer meander-line array polarizer was implemented; an approach that was fairly well suited to the TLGA geometry. The principal development of this work was to adapt the standard linear bicone such that its aperture could be increased in order to increase the available gain of the antenna. As one increases the aperture of a standard bicone, the phase variation across the aperture begins to increase, so the larger the aperture becomes, the greater the phase variation. In order to maximize the gain from any aperture antenna, the phase should be kept as uniform as possible. Thus, as the standard bicone fs aperture increases, the gain increase becomes less until one reaches a point of diminishing returns. In order to overcome this problem, a shaped aperture is used. Rather than the standard linear bicone, a parabolic bicone was found to reduce the amount of phase variation as the aperture increases. In fact, the phase variation is half of the standard linear bicone, which leads to higher gain with smaller aperture sizes. The antenna pattern radiated from this parabolic-shaped bicone antenna has fairly high side lobes. The Juno project requested that these sidelobes be minimized. This was accomplished by adding corrugations to the parabolic shape. This corrugated-shaped bicone antenna had reasonably low sidelobes, and the appropriate gain and beamwidth to meet project requirements.

[A Compact Source of Terahertz Radiation Based on Interaction of Electrons in à Quantum Well with an Electromagnetic Wave of a Corrugated Waveguide].

PubMed

Shchurova, L Yu; Namiot, V A; Sarkisyan, D R

2015-01-01

Coherent sources of electromagnetic waves in the terahertz frequency range are very promising for various applications, including biology and medicine. In this paper we propose a scheme of a compact terahertz source, in which terahertz radiation is generated due to effective interaction of electrons in a quantum well with an electromagnetic wave of a corrugated waveguide. We have shown that the generation of electromagnetic waves with a frequency of 1012 sec(-1) and an output power of up to 25. mW is possible in the proposed scheme.

Experimental investigation of laminar flow of viscous oil through a circular tube having integral axial corrugation roughness and fitted with twisted tapes with oblique teeth

NASA Astrophysics Data System (ADS)

Pal, Sagnik; Saha, Sujoy Kumar

2015-08-01

The experimental friction factor and Nusselt number data for laminar flow of viscous oil through a circular duct having integral axial corrugation roughness and fitted with twisted tapes with oblique teeth have been presented. Predictive friction factor and Nusselt number correlations have also been presented. The thermohydraulic performance has been evaluated. The major findings of this experimental investigation are that the twisted tapes with oblique teeth in combination with integral axial corrugation roughness perform significantly better than the individual enhancement technique acting alone for laminar flow through a circular duct up to a certain value of fin parameter.

Plasma influence on the dispersion properties of finite-length, corrugated waveguides

NASA Astrophysics Data System (ADS)

Shkvarunets, A.; Kobayashi, S.; Weaver, J.; Carmel, Y.; Rodgers, J.; Antonsen, T. M., Jr.; Granatstein, V. L.; Destler, W. W.; Ogura, K.; Minami, K.

1996-03-01

We present an experimental study of the electromagnetic properties of transverse magnetic modes in a corrugated-wall cavity filled with a radially inhomogeneous plasma. The shifts of the resonant frequencies of a finite-length, corrugated cavity were measured as a function of the background plasma density and the dispersion diagram was reconstructed up to a peak plasma density of 1012 cm-3. Good agreement with a calculated dispersion diagram is obtained for plasma densities below 5×1011 cm-3.

A high-power microwave circular polarizer and its application on phase shifter.

PubMed

Shao, Hao; Hu, Yongmei; Chang, Chao; Guo, Letian

2016-04-01

A high-power waveguide dual circular polarizer was theoretically designed and proof-of-principle was experimentally tested. It consists of two incident rectangular waveguides with a perpendicular H-plane junction, one circular waveguide with a pair of trapezoidal grooves coupled in E-plane at the top, a spherical crown located at the bottom, and an iris at the perpendicular junction of two rectangular waveguides. When wave incidents at one of the two separated rectangular waveguides, it, respectively, generates a left-hand circular polarized wave or a right-hand circular polarized wave in the circular waveguide. By adding a dumbbell-like metal plug driven with a high speed servomotor, a movable short circuit is formed along the circular waveguide to adjust the output RF phase of the rectangular port, realizing a high-speed high-power phase shifter. The C-band high power microwave (HPM) experiments were carried out, and the power capacity of the HPM polarizer and phase shifter was demonstrated to reach gigawatt level.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Read, Michael; Ives, Robert Lawrence; Marsden, David

The Phase II program developed an internal RF coupler that transforms the whispering gallery RF mode produced in gyrotron cavities to an HE11 waveguide mode propagating in corrugated waveguide. This power is extracted from the vacuum using a broadband, chemical vapor deposited (CVD) diamond, Brewster angle window capable of transmitting more than 1.5 MW CW of RF power over a broad range of frequencies. This coupling system eliminates the Mirror Optical Units now required to externally couple Gaussian output power into corrugated waveguide, significantly reducing system cost and increasing efficiency. The program simulated the performance using a broad range ofmore » advanced computer codes to optimize the design. Both a direct coupler and Brewster angle window were built and tested at low and high power. Test results confirmed the performance of both devices and demonstrated they are capable of achieving the required performance for scientific, defense, industrial, and medical applications.« less

Initial results for a 170 GHz high power ITER waveguide component test stand

NASA Astrophysics Data System (ADS)

Bigelow, Timothy; Barker, Alan; Dukes, Carl; Killough, Stephen; Kaufman, Michael; White, John; Bell, Gary; Hanson, Greg; Rasmussen, Dave

2014-10-01

A high power microwave test stand is being setup at ORNL to enable prototype testing of 170 GHz cw waveguide components being developed for the ITER ECH system. The ITER ECH system will utilize 63.5 mm diameter evacuated corrugated waveguide and will have 24 >150 m long runs. A 170 GHz 1 MW class gyrotron is being developed by Communications and Power Industries and is nearing completion. A HVDC power supply, water-cooling and control system has been partially tested in preparation for arrival of the gyrotron. The power supply and water-cooling system are being designed to operate for >3600 second pulses to simulate the operating conditions planned for the ITER ECH system. The gyrotron Gaussian beam output has a single mirror for focusing into a 63.5 mm corrugated waveguide in the vertical plane. The output beam and mirror are enclosed in an evacuated duct with absorber for stray radiation. Beam alignment with the waveguide is a critical task so a combination of mirror tilt adjustments and a bellows for offsets will be provided. Analysis of thermal patterns on thin witness plates will provide gyrotron mode purity and waveguide coupling efficiency data. Pre-prototype waveguide components and two dummy loads are available for initial operational testing of the gyrotron. ORNL is managed by UT-Battelle, LLC, for the U.S. Dept. of Energy under Contract DE-AC-05-00OR22725.

Novel types of surface acoustic wave microreflectors - Performance analysis and simulations

NASA Astrophysics Data System (ADS)

Golan, G.; Griffel, G.; Seidman, A.; Croitoru, N.

1990-06-01

Surface acoustic waves for micrograting reflectors have been characterized. Based on the perturbation theory, eight different types of structures on an acoustic waveguide were analyzed. Results of simulations of all eight types of corrugation structures were evaluated in order to find the least leaky waveguide, the most efficient reflector (with minimum necessary perturbations), and the optimal mode shape for improved performances. General design curves are presented in order to illustrate the behavior of the incident and reflected waves under a variety of structural conditions. Analytic expressions for the calculations of the mode amplitude and mode shape, and for general acoustic corrugations are derived and then the simulations results are presented.

WAVE DELAYING STRUCTURE FOR RECTANGULAR WAVE-GUIDES

DOEpatents

Robertson-Shersby-Harvie, R.B.; Dain, J.

1956-11-13

This patent relates to wave-guides and in particular describes wave delaying structure located within a wave-guide. The disclosed wave-guide has an elongated fiat metal sheet arranged in a central plane of the guide and formed with a series of transverse inductive slots such that each face presents an inductive impedance to the guide. The sheet is thickened in the area between slots to increase the self capacity of the slots. Experimental results indicate that in a wave-guide loaded in accordance with the invention the guided wavelength changes more slowly as the air wavelength is changed than the guided wavelength does in wave-guides loaded by means of corrugations.

Simple Expressions for the Design of Linear Tapers in Overmoded Corrugated Waveguides

DOE PAGES

Schaub, S. C.; Shapiro, M. A.; Temkin, R. J.

2015-08-16

In this paper, simple analytical formulae are presented for the design of linear tapers with very low mode conversion loss in overmoded corrugated waveguides. For tapers from waveguide radius a2 to a1, with a11a 2/λ. Here, λ is the wavelength of radiation. The fractional loss of the HE 11 mode in an optimized taper is 0.0293(a 2-a 1) 4/amore » $$2\\atop{1}$$1a$$2\\atop{2}$$. These formulae are accurate when a2≲2a 1. Slightly more complex formulae, accurate for a 2≤4a 1, are also presented in this paper. The loss in an overmoded corrugated linear taper is less than 1 % when a 2≤2.12a 1 and less than 0.1 % when a 2≤1.53a 1. The present analytic results have been benchmarked against a rigorous mode matching code and have been found to be very accurate. The results for linear tapers are compared with the analogous expressions for parabolic tapers. Finally, parabolic tapers may provide lower loss, but linear tapers with moderate values of a 2/a 1 may be attractive because of their simplicity of fabrication.« less

Axial Crushing Behaviors of Thin-Walled Corrugated and Circular Tubes - A Comparative Study

NASA Astrophysics Data System (ADS)

Reyaz-Ur-Rahim, Mohd.; Bharti, P. K.; Umer, Afaque

2017-10-01

With the help of finite element analysis, this research paper deals with the energy absorption and collapse behavior with different corrugated section geometries of hollow tubes made of aluminum alloy 6060-T4. Literature available experimental data were used to validate the numerical models of the structures investigated. Based on the results available for symmetric crushing of circular tubes, models were developed to investigate corrugated thin-walled structures behavior. To study the collapse mechanism and energy absorbing ability in axial compression, the simulation was carried in ABAQUS /EXPLICIT code. In the simulation part, specimens were prepared and axially crushed to one-fourth length of the tube and the energy diagram of crushing force versus axial displacement is shown. The effect of various parameters such as pitch, mean diameter, corrugation, amplitude, the thickness is demonstrated with the help of diagrams. The overall result shows that the corrugated section geometry could be a good alternative to the conventional tubes.

WAVE DELAYING STRUCTURE FOR RECTANGULAR WAVE-GUIDES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Robertson-Shersby-Harvie, R.B.; Dain, J.

1956-11-13

This patent relates to wave-guides and in particular describes wave delaying structure located within a wave-guide. The disclosed wave-guide has an elongated fiat metal sheet arranged in a central plane of the guide and formed with a series of transverse inductive slots such that each face presents an inductive impedance to the guide. The sheet is thickened in the area between slots to increase the self capacity of the slots. Experimental results indicate that in a wave-guide loaded in accordance with the invention the guided wavelength changes more slowly as the air wavelength is changed than the guided wavelength doesmore » in wave-guides loaded by means of corrugations.« less

Apodized coupled resonator waveguides.

PubMed

Capmany, J; Muñoz, P; Domenech, J D; Muriel, M A

2007-08-06

In this paper we propose analyse the apodisation or windowing of the coupling coefficients in the unit cells of coupled resonator waveguide devices (CROWs) as a means to reduce the level of secondary sidelobes in the bandpass characteristic of their transfer functions. This technique is regularly employed in the design of digital filters and has been applied as well in the design of other photonic devices such as corrugated waveguide filters and fiber Bragg gratings. The apodisation of both Type-I and Type-II structures is discussed for several windowing functions.

FIBER AND INTEGRATED OPTICS: Influence of diffraction-induced emission of light on resonant conversion of surface waves in diffraction-coupled optical waveguides

NASA Astrophysics Data System (ADS)

Kiselev, V. A.; Shaposhnikov, S. N.

1989-09-01

An investigation is reported of diffraction-induced emission of surface waves under conditions of resonant transfer of light between different regular and corrugated waveguides. It is shown that the part of the emitted light flux carried by surface waves along diffraction-coupled waveguides depends strongly on the ratio of the effective refractive indices of the guides. The dependences of the optical coupling length and of the corresponding emitted light flux on the distance between the waveguides and on the difference between their refractive indices are given.

Analysis of the multipactor effect in circular waveguides excited by two orthogonal polarization waves

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pérez, A. M.; Boria, V. E.; Gimeno, B.

2014-08-15

Circular waveguides, either employed as resonant cavities or as irises connecting adjacent guides, are widely present in many passive components used in different applications (i.e., particle accelerators and satellite subsystems). In this paper, we present the study of the multipactor effect in circular waveguides considering the coexistence of the two polarizations of the fundamental TE{sub 11} circular waveguide mode. For a better understanding of the problem, only low multipactor orders have been explored as a function of the polarization ellipse eccentricity. Special attention has been paid to the linear and circular polarizations, but other more general configurations have also beenmore » explored.« less

Microminiature optical waveguide structure and method for fabrication

DOEpatents

Strand, O.T.; Deri, R.J.; Pocha, M.D.

1998-12-08

A method for manufacturing low-cost, nearly circular cross section waveguides comprises starting with a substrate material that a molten waveguide material can not wet or coat. A thin layer is deposited of an opposite material that the molten waveguide material will wet and is patterned to describe the desired surface-contact path pedestals for a waveguide. A waveguide material, e.g., polymer or doped silica, is deposited. A resist material is deposited and unwanted excess is removed to form pattern masks. The waveguide material is etched away to form waveguide precursors and the masks are removed. Heat is applied to reflow the waveguide precursors into near-circular cross-section waveguides that sit atop the pedestals. The waveguide material naturally forms nearly circular cross sections due to the surface tension effects. After cooling, the waveguides will maintain the round shape. If the width and length are the same, then spherical ball lenses are formed. Alternatively, the pedestals can be patterned to taper along their lengths on the surface of the substrate. This will cause the waveguides to assume a conical taper after reflowing by heat. 32 figs.

Microminiature optical waveguide structure and method for fabrication

DOEpatents

Strand, Oliver T.; Deri, Robert J.; Pocha, Michael D.

1998-01-01

A method for manufacturing low-cost, nearly circular cross section waveguides comprises starting with a substrate material that a molten waveguide material can not wet or coat. A thin layer is deposited of an opposite material that the molten waveguide material will wet and is patterned to describe the desired surface-contact path pedestals for a waveguide. A waveguide material, e.g., polymer or doped silica, is deposited. A resist material is deposited and unwanted excess is removed to form pattern masks. The waveguide material is etched away to form waveguide precursors and the masks are removed. Heat is applied to reflow the waveguide precursors into near-circular cross-section waveguides that sit atop the pedestals. The waveguide material naturally forms nearly circular cross sections due to the surface tension effects. After cooling, the waveguides will maintain the round shape. If the width and length are the same, then spherical ball lenses are formed. Alternatively, the pedestals can be patterned to taper along their lengths on the surface of the substrate. This will cause the waveguides to assume a conical taper after reflowing by heat.

Conceptual design of X band waveguide dual circular polarizer

DOE PAGES

Xu, Chen; Tantawi, Sami; Wang, Juwen

2016-06-01

We present in this paper a new design of dual circular polarizer. This innovative design converts radiofrequency (rf) energy from TE10 mode in a rectangular waveguide to two polarized TE11 modes in a circular waveguide. A reflection less than ₋20 db is achieved and breakdown field is less than 42 MV/m at input of 1 MW. Meanwhile, this polarizer has a megahertz bandwidth, and the thermal stability is also discussed. This device can be used for broadcasting and receiving the circular polarized signals.

High power millimeter wave experiment of ITER relevant electron cyclotron heating and current drive system.

PubMed

Takahashi, K; Kajiwara, K; Oda, Y; Kasugai, A; Kobayashi, N; Sakamoto, K; Doane, J; Olstad, R; Henderson, M

2011-06-01

High power, long pulse millimeter (mm) wave experiments of the RF test stand (RFTS) of Japan Atomic Energy Agency (JAEA) were performed. The system consists of a 1 MW/170 GHz gyrotron, a long and short distance transmission line (TL), and an equatorial launcher (EL) mock-up. The RFTS has an ITER-relevant configuration, i.e., consisted by a 1 MW-170 GHz gyrotron, a mm wave TL, and an EL mock-up. The TL is composed of a matching optics unit, evacuated circular corrugated waveguides, 6-miter bends, an in-line waveguide switch, and an isolation valve. The EL-mock-up is fabricated according to the current design of the ITER launcher. The Gaussian-like beam radiation with the steering capability of 20°-40° from the EL mock-up was also successfully proved. The high power, long pulse power transmission test was conducted with the metallic load replaced by the EL mock-up, and the transmission of 1 MW/800 s and 0.5 MW/1000 s was successfully demonstrated with no arcing and no damages. The transmission efficiency of the TL was 96%. The results prove the feasibility of the ITER electron cyclotron heating and current drive system. © 2011 American Institute of Physics

Guided-mode interactions in thin films with surface corrugation

NASA Astrophysics Data System (ADS)

Seshadri, S. R.

1994-12-01

The guided modes in a thin-film planar dielectric waveguide sandwiched between a cover and a substrate (two different dielectrics) are considered. The interface between the cover and the film has a smooth corrugation in the longitudinal direction. For weak corrugations, the guided-mode interactions are investigated using the expansion in terms of ideal normal modes. A corresponding treament is given for the not-so-weak corrugations using the expansion in terms of local normal modes. The coupling coefficients are evaluated and reduced to simple forms. The theories are specialized for the treatment of contradirectional coupling between two guided modes taking place selectively in the neighborhood of the Bragg frequency. The coupled-mode equations governing the contradirectional interaction obtained from the local normal mode expansion procedure, in the limit of weak periodic corrugations, are identical to those deduced directly using the ideal normal mode expansion technique. The treatments for both the transverse electric and the transvers magnetic modes are included.

Generation of Bright Phase-matched Circularly-polarized Extreme Ultraviolet High Harmonics

DTIC Science & Technology

2014-12-08

circularly-polarized laser pulses field-ionize a gas in a hollow - core waveguide. We use this new light source for magnetic circular dichroism...polarized with opposite helicity in a gas-filled hollow waveguide (see Supplementary Section 6 for details on the important features of this source...mJ/pulse) driving lasers are focused into a 150-µm-diameter, 2-cm-long gas-filled hollow waveguide using lenses with focal lengths of 50 cm and 75 cm

Cup waveguide antenna with integrated polarizer and OMT

NASA Technical Reports Server (NTRS)

Kory, Carol (Inventor); Acosta, Roberto J. (Inventor); Lambert, Kevin M. (Inventor)

2011-01-01

A cup waveguide antenna with integrated polarizer and OMT for simultaneously communicating left and right hand circularly polarized electromagnetic waves is adjustable to obtain efficient propagation and reception of electromagnetic waves. The antenna includes a circular waveguide having an orthomode transducer utilizing first and second pins longitudinally spaced apart and oriented orthogonally with respect to each other. Six radially-oriented adjustable polarizer screws extend from the exterior to the interior of the waveguide. A septum intermediate the first and second pins is aligned with the first pin. Adjustment of the polarizer screws enables maximized propagation of and/or response to left hand circularly polarized electromagnetic waves by the first pin while simultaneously enabling maximized propagation of and/or response to right hand circularly polarized electromagnetic waves by the second pin.

Evaluation of low-frequency operational limit of proposed ITER low-field-side reflectometer waveguide run including miter bends.

PubMed

Wang, G; Peebles, W A; Doyle, E J; Crocker, N A; Wannberg, C; Lau, C; Hanson, G R; Doane, J L

2017-10-01

The present design concept for the ITER low-field-side reflectometer transmission line (TL) consists of an ∼40 m long, 6.35 cm diameter helically corrugated waveguide (WG) together with ten 90° miter bends. This paper presents an evaluation of the TL performance at low frequencies (33-50 GHz) where the predicted HE 11 mode ohmic and mode conversion losses start to increase significantly. Quasi-optical techniques were used to form a near Gaussian beam to efficiently couple radiation in this frequency range into the WG. It was observed that the output beams from the guide remained linearly polarized with cross-polarization power levels of ∼1.5%-3%. The polarization rotation due to the helical corrugations was in the range ∼1°-3°. The radiated beam power profiles typically show excellent Gaussian propagation characteristics at distances >20 cm from the final exit aperture. The round trip propagation loss was found to be ∼2.5 dB at 50 GHz and ∼6.5 dB at 35 GHz, showing an inverse increase with frequency. This was consistent with updated calculations of miter bend and ohmic losses. At low frequencies (33-50 GHz), the mode purity remained very good at the exit of the waveguide, and the losses are perfectly acceptable for operation in ITER. The primary challenge may come from the future addition of a Gaussian telescope and other filter components within the corrugated guide, which will likely introduce additional perturbations to the beam profile and an increase in mode-conversion loss.

Evaluation of low-frequency operational limit of proposed ITER low-field-side reflectometer waveguide run including miter bends

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Guiding; Peebles, W. A.; Doyle, E. J.

The present design concept for the ITER low-field-side reflectometer transmission line (TL) consists of an ~40 m long, 6.35 cm diameter helically corrugated waveguide (WG) together with ten 90° miter bends. This paper presents an evaluation of the TL performance at low frequencies (33-50 GHz) where the predicted HE11 mode ohmic and mode conversion losses start to increase significantly. Quasi-optical techniques were used to form a near Gaussian beam to efficiently couple radiation in this frequency range into the WG. We observed that the output beams from the guide remained linearly polarized with cross-polarization power levels of ~1.5%-3%. The polarizationmore » rotation due to the helical corrugations was in the range ~1°-3°. The radiated beam power profiles typically show excellent Gaussian propagation characteristics at distances >20 cm from the final exit aperture. The round trip propagation loss was found to be ~2.5 dB at 50 GHz and ~6.5 dB at 35 GHz, showing an inverse increase with frequency. This was consistent with updated calculations of miter bend and ohmic losses. At low frequencies (33-50 GHz), the mode purity remained very good at the exit of the waveguide, and the losses are perfectly acceptable for operation in ITER. Finally, the primary challenge may come from the future addition of a Gaussian telescope and other filter components within the corrugated guide, which will likely introduce additional perturbations to the beam profile and an increase in mode-conversion loss.« less

HRMS sky survey wideband feed system design for DSS 24 beam waveguide antenna

NASA Technical Reports Server (NTRS)

Stanton, P. H.; Lee, P. R.; Reilly, H. F.

1993-01-01

The High-Resolution Microwave Survey (HRMS) Sky Survey project will be implemented on the DSS 24 beam waveguide (BWG) antenna over the frequency range of 2.86 to 10 GHz. Two wideband, ring-loaded, corrugated feed horns were designed to cover this range. The horns match the frequency-dependent gain requirements for the DSS 24 BWG system. The performance of the feed horns and the calculated system performance of DSS 24 are presented.

Ultra-wideband filtering of spoof surface plasmon polaritons using deep subwavelength planar structures

PubMed Central

Hu, Ming Zhe; Zhang, Hao Chi; Yin, Jia Yuan; Ding, Zhao; Liu, Jun Feng; Tang, Wen Xuan; Cui, Tie Jun

2016-01-01

Novel ultra-wideband filtering of spoof surface plasmon polaritons (SPPs) is proposed in the microwave frequency using deep subwavelength planar structures printed on thin and flexible dielectric substrate. The proposed planar SPPs waveguide is composed of two mirror-oriented metallic corrugated strips, which are further decorated with parallel-arranged slots in the main corrugated strips. This compound structure provides deep subwavelength field confinement as well as flexible parameters when employed as a plasmonic waveguide, which is potential to construct miniaturization. Using momentum and impedance matching technology, we achieve a smooth conversion between the proposed SPPs waveguide and the conventional transmission line. To verify the validity of the design, we fabricate a spoof SPPs filter, and the measured results illustrate excellent performance, in which the reflection coefficient is less than −10 dB within the −3 dB passband from 1.21 GHz to 7.21 GHz with the smallest insertion loss of 1.23 dB at 2.21 GHz, having very good agreements with numerical simulations. The ultra-wideband filter with low insertion loss and high transmission efficiency possesses great potential in modern communication systems. PMID:27883028

Ultra-wideband filtering of spoof surface plasmon polaritons using deep subwavelength planar structures.

PubMed

Hu, Ming Zhe; Zhang, Hao Chi; Yin, Jia Yuan; Ding, Zhao; Liu, Jun Feng; Tang, Wen Xuan; Cui, Tie Jun

2016-11-24

Novel ultra-wideband filtering of spoof surface plasmon polaritons (SPPs) is proposed in the microwave frequency using deep subwavelength planar structures printed on thin and flexible dielectric substrate. The proposed planar SPPs waveguide is composed of two mirror-oriented metallic corrugated strips, which are further decorated with parallel-arranged slots in the main corrugated strips. This compound structure provides deep subwavelength field confinement as well as flexible parameters when employed as a plasmonic waveguide, which is potential to construct miniaturization. Using momentum and impedance matching technology, we achieve a smooth conversion between the proposed SPPs waveguide and the conventional transmission line. To verify the validity of the design, we fabricate a spoof SPPs filter, and the measured results illustrate excellent performance, in which the reflection coefficient is less than -10 dB within the -3 dB passband from 1.21 GHz to 7.21 GHz with the smallest insertion loss of 1.23 dB at 2.21 GHz, having very good agreements with numerical simulations. The ultra-wideband filter with low insertion loss and high transmission efficiency possesses great potential in modern communication systems.

Dual nature of localization in guiding systems with randomly corrugated boundaries: Anderson-type versus entropic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tarasov, Yu.V., E-mail: yutarasov@ire.kharkov.ua; Shostenko, L.D.

A unified theory for the conductance of an infinitely long multimode quantum wire whose finite segment has randomly rough lateral boundaries is developed. It enables one to rigorously take account of all feasible mechanisms of wave scattering, both related to boundary roughness and to contacts between the wire rough section and the perfect leads within the same technical frameworks. The rough part of the conducting wire is shown to act as a mode-specific randomly modulated effective potential barrier whose height is governed essentially by the asperity slope. The mean height of the barrier, which is proportional to the average slopemore » squared, specifies the number of conducting channels. Under relatively small asperity amplitude this number can take on arbitrary small, up to zero, values if the asperities are sufficiently sharp. The consecutive channel cut-off that arises when the asperity sharpness increases can be regarded as a kind of localization, which is not related to the disorder per se but rather is of entropic or (equivalently) geometric origin. The fluctuating part of the effective barrier results in two fundamentally different types of guided wave scattering, viz., inter- and intramode scattering. The intermode scattering is shown to be for the most part very strong except in the cases of (a) extremely smooth asperities, (b) excessively small length of the corrugated segment, and (c) the asperities sharp enough for only one conducting channel to remain in the wire. Under strong intermode scattering, a new set of conducting channels develops in the corrugated waveguide, which have the form of asymptotically decoupled extended modes subject to individual solely intramode random potentials. In view of this fact, two transport regimes only are realizable in randomly corrugated multimode waveguides, specifically, the ballistic and the localized regime, the latter characteristic of one-dimensional random systems. Two kinds of localization are thus shown to coexist in waveguide-like systems with randomly corrugated boundaries, specifically, the entropic localization and the one-dimensional Anderson (disorder-driven) localization. If the particular mode propagates across the rough segment ballistically, the Fabry–Pérot-type oscillations should be observed in the conductance, which are suppressed for the mode transferred in the Anderson-localized regime.« less

Development of the low-field side reflectometer for ITER

NASA Astrophysics Data System (ADS)

Muscatello, Christopher; Anderson, James; Gattuso, Anthony; Doyle, Edward; Peebles, William; Seraydarian, Raymond; Wang, Guiding; Kramer, Gerrit; Zolfaghari, Ali; Atomics Team, General; University of California Los Angeles Team; Princeton Plasma Physics Laboratory Team

2017-10-01

The Low-Field Side Reflectometer (LFSR) for ITER will provide real-time edge density profiles every 10 ms for feedback control and every 24 μs for physics evaluation. The spatial resolution will be better than 5 mm over 30 - 165 GHz, probing the scrape-off layer to the top of the pedestal in H-mode plasmas. An antenna configuration has been selected for measurements covering anticipated plasma elevations. Laboratory validation of diagnostic performance is underway using a LFSR transmission line (TL) mockup. The 40-meter TL includes circular corrugated waveguide, length calibration feature, Gaussian telescope, vacuum windows, containment membranes, and expansion joint. Transceiver modules coupled to the input of the TL provide frequency-modulated (FM) data for evaluation of performance as a monostatic reflectometer. Results from the mockup tests are presented and show that, with some further optimization, the LFSR will meet or exceed the measurement requirements for ITER. An update of the LFSR instrumentation design status is also presented with preliminary test results. Work supported by PPPL under subcontract S013252-A.

Mechanisms and Methods for Selective Wavelength Filtering

NASA Technical Reports Server (NTRS)

Tuma, Margaret (Inventor); Brown, Thomas G. (Inventor); Gruhlke, Russell (Inventor)

2007-01-01

An optical filter includes a dielectric waveguide layer, supporting waveguide modes at specific wavelengths and receiving incident light, a corrugated film layer, composed of one of a metal and a semiconductor and positioned adjacent to a second surface of the waveguide layer and a sensor layer, wherein the sensor layer is capable of absorbing optical energy and generating a corresponding electrical signal. The metal film layer supports a plurality of plasmons, the plurality of plasmons producing a first field and is excited by a transverse mode of the waveguide modes at a wavelength interval. The first field penetrates the sensor layer and the sensor layer generates an electrical signal corresponding to an intensity of received incident light within the wavelength interval.

Waveguide-mode polarization gaps in square spiral photonic crystals

NASA Astrophysics Data System (ADS)

Liu, Rong-Juan; John, Sajeev; Li, Zhi-Yuan

2015-09-01

We designed waveguide channels in two types of square spiral photonic crystals. Wide polarization gaps, in which only one circular polarization wave is allowed while the other counter-direction circular polarization wave is forbidden, can be opened up on the waveguide modes within the fundamental photonic band gap according to the calculation of band structures and transmission spectra. This phenomenon is ascribed to the chirality of the waveguide and is independent of the chirality of the background photonic crystal. Moreover, the transmission spectra show a good one-way property of the waveguide channels. The chiral quality factor demonstrates the handedness of the allowed and impeded chiral waveguide modes, and further proved the property of the waveguide-mode polarization gap. Such waveguides with waveguide-mode polarization gap are a good candidate for one-way waveguides with robust backscattering-immune transport.

Simple Correctors for Elimination of High-Order Modes in Corrugated Waveguide Transmission Lines

PubMed Central

Kowalski, Elizabeth J.; Shapiro, Michael A.; Temkin, Richard J.

2014-01-01

When using overmoded corrugated waveguide transmission lines for high power applications, it is necessary to control the mode content of the system. Ideally, overmoded corrugated transmission lines operate in the fundamental HE11 mode and provide low losses for long distances. Unwanted higher order modes (HOMs), particularly LP11 and HE12, are often excited in the experimental systems due to practical misalignments in the transmission line system. This paper discusses how the unwanted modes propagate along with the fundamental mode in the transmission line system by formulating an equation that relates the center of power offset and angle of propagation of a beam (for the HE11 and LP11 modes) or the waist size and phase front radius of curvature of a beam (for the HE11 and HE12 modes). By introducing two miter bend correctors into the transmission system—miter bends that have slightly angled or ellipsoidal mirrors—the HOMs can be precisely manipulated in the system. This technique can be used to eliminate small quantities of unwanted modes, thereby creating a nearly pure fundamental mode beam with minimal losses. Examples of these applications are calculated and show the theoretical conversion of up to 10% HOM content into the fundamental HE11 mode with minimal losses. PMID:25067859

Smooth bridge between guided waves and spoof surface plasmon polaritons.

PubMed

Liu, Liangliang; Li, Zhuo; Gu, Changqing; Xu, Bingzheng; Ning, Pingping; Chen, Chen; Yan, Jian; Niu, Zhenyi; Zhao, Yongjiu

2015-04-15

In this work, we build a smooth bridge between a coaxial waveguide and a plasmonic waveguide with subwavelength periodically cylindrical radial grooves, to realize high-efficiency mode conversion between conventional guided waves and spoof surface plasmon polaritons in broadband. This bridge consists of a flaring coaxial waveguide connected with a metal cylindrical wire corrugated with subwavelength gradient radial grooves. Experimental results of the transmission and reflection coefficients show excellent agreement with the numerical simulations. The proposed scheme can be extended readily to other bands and the bridge structure can find potential applications in the integration of conventional microwave or terahertz devices with plasmonic circuits.

Modal analysis applied to circular, rectangular, and coaxial waveguides

NASA Technical Reports Server (NTRS)

Hoppe, D. J.

1988-01-01

Recent developments in the analysis of various waveguide components and feedhorns using Modal Analysis (Mode Matching Method) are summarized. A brief description of the theory is presented, and the important features of the method are pointed out. Specific examples in circular, rectangular, and coaxial waveguides are included, with comparisons between the theory and experimental measurements. Extensions to the methods are described.

Optimizing the G/T ratio of the DSS-13 34-meter beam-waveguide antenna

NASA Technical Reports Server (NTRS)

Esquivel, M. S.

1992-01-01

Calculations using Physical Optics computer software were done to optimize the gain-to-noise temperature (G/T) ratio of DSS-13, the DSN's 34-m beam-waveguide antenna, at X-band for operation with the ultra-low-noise amplifier maser system. A better G/T value was obtained by using a 24.2-dB far-field-gain smooth-wall dual-mode horn than by using the standard X-band 22.5-dB-gain corrugated horn.

Emission Characteristics of Organic Light-Emitting Diodes and Organic Thin-Films with Planar and Corrugated Structures

PubMed Central

Wei, Mao-Kuo; Lin, Chii-Wann; Yang, Chih-Chung; Kiang, Yean-Woei; Lee, Jiun-Haw; Lin, Hoang-Yan

2010-01-01

In this paper, we review the emission characteristics from organic light-emitting diodes (OLEDs) and organic molecular thin films with planar and corrugated structures. In a planar thin film structure, light emission from OLEDs was strongly influenced by the interference effect. With suitable design of microcavity structure and layer thicknesses adjustment, optical characteristics can be engineered to achieve high optical intensity, suitable emission wavelength, and broad viewing angles. To increase the extraction efficiency from OLEDs and organic thin-films, corrugated structure with micro- and nano-scale were applied. Microstructures can effectively redirects the waveguiding light in the substrate outside the device. For nanostructures, it is also possible to couple out the organic and plasmonic modes, not only the substrate mode. PMID:20480033

New rapid method for determining edgewise compressive strength of corrugated fiberboard

Treesearch

John W. Koning

1986-01-01

The objective of this study was to determine if corrugated fiberboard specimens that had been necked down with a common router would yield acceptable edgewise compressive strength values. Tests were conducted on specimens prepared using a circular saw and router, and the results were compared with those obtained on specimens prepared according to TAPPI Test Method T...

High-performance slow light photonic crystal waveguides with topology optimized or circular-hole based material layouts

NASA Astrophysics Data System (ADS)

Wang, Fengwen; Jensen, Jakob S.; Sigmund, Ole

2012-10-01

Photonic crystal waveguides are optimized for modal confinement and loss related to slow light with high group index. A detailed comparison between optimized circular-hole based waveguides and optimized waveguides with free topology is performed. Design robustness with respect to manufacturing imperfections is enforced by considering different design realizations generated from under-, standard- and over-etching processes in the optimization procedure. A constraint ensures a certain modal confinement, and loss related to slow light with high group index is indirectly treated by penalizing field energy located in air regions. It is demonstrated that slow light with a group index up to ng = 278 can be achieved by topology optimized waveguides with promising modal confinement and restricted group-velocity-dispersion. All the topology optimized waveguides achieve a normalized group-index bandwidth of 0.48 or above. The comparisons between circular-hole based designs and topology optimized designs illustrate that the former can be efficient for dispersion engineering but that larger improvements are possible if irregular geometries are allowed.

High-performance 16-way Ku-band radial power combiner based on the TE01-circular waveguide mode

NASA Astrophysics Data System (ADS)

Montejo-Garai, José R.; Saracho-Pantoja, Irene O.; Ruiz-Cruz, Jorge A.; Rebollar, Jesús M.

2018-03-01

This work presents a 16-way Ku-band radial power combiner for high power and high frequency applications, using the very low loss TE01 circular waveguide mode. The accomplished design shows an excellent performance: the experimental prototype has a return loss better than 30 dB, with a balance for the amplitudes of (±0.15 dB) and (±2.5°) for the phases, in a 16.7% fractional bandwidth (2 GHz centered at 12 GHz). For obtaining these outstanding specifications, required, for instance, in high-frequency amplification or on plasma systems, a rigorous step-by-step procedure is presented. First, a high-purity mode transducer has been designed, from the TE10 mode in the rectangular waveguide to the TE01 mode in the circular waveguide, with very high attenuation (>50 dB) for the other propagating and evanescent modes in the circular waveguide. This transducer has been manufactured and measured in a back-to-back configuration, validating the design process. Second, an E-plane 16-way radial power divider has been designed, where the power is coupled from the 16 non-reduced-height radial standard waveguides into the TE01 circular waveguide mode, improving the insertion loss response and removing the usual tapered transformers of previous designs limiting the power handling. Finally, both the transducer and the divider have been assembled to make the final radial combiner. The prototype has been carefully manufactured, showing very good agreement between the measurements and the full-wave simulations.

Cup Cylindrical Waveguide Antenna

NASA Technical Reports Server (NTRS)

Acosta, Roberto J.; Darby, William G.; Kory, Carol L.; Lambert, Kevin M.; Breen, Daniel P.

2008-01-01

The cup cylindrical waveguide antenna (CCWA) is a short backfire microwave antenna capable of simultaneously supporting the transmission or reception of two distinct signals having opposite circular polarizations. Short backfire antennas are widely used in mobile/satellite communications, tracking, telemetry, and wireless local area networks because of their compactness and excellent radiation characteristics. A typical prior short backfire antenna contains a half-wavelength dipole excitation element for linear polarization or crossed half-wavelength dipole elements for circular polarization. In order to achieve simultaneous dual circular polarization, it would be necessary to integrate, into the antenna feed structure, a network of hybrid components, which would introduce significant losses. The CCWA embodies an alternate approach that entails relatively low losses and affords the additional advantage of compactness. The CCWA includes a circular cylindrical cup, a circular disk subreflector, and a circular waveguide that serves as the excitation element. The components that make it possible to obtain simultaneous dual circular polarization are integrated into the circular waveguide. These components are a sixpost polarizer and an orthomode transducer (OMT) with two orthogonal coaxial ports. The overall length of the OMT and polarizer (for the nominal middle design frequency of 2.25 GHz) is about 11 in. (approximately equal to 28 cm), whereas the length of a commercially available OMT and polarizer for the same frequency is about 32 in. (approximately equal to 81 cm).

LOADED WAVEGUIDES

DOEpatents

Mullett, L.B.; Loach, B.G.; Adams, G.L.

1958-06-24

>Loaded waveguides are described for the propagation of electromagnetic waves with reduced phase velocities. A rectangular waveguide is dimensioned so as to cut-off the simple H/sub 01/ mode at the operating frequency. The waveguide is capacitance loaded, so as to reduce the phase velocity of the transmitted wave, by connecting an electrical conductor between directly opposite points in the major median plane on the narrower pair of waveguide walls. This conductor may take a corrugated shape or be an aperature member, the important factor being that the electrical length of the conductor is greater than one-half wavelength at the operating frequency. Prepared for the Second U.N. International ConferThe importance of nuclear standards is duscussed. A brief review of the international callaboration in this field is given. The proposal is made to let the International Organization for Standardization (ISO) coordinate the efforts from other groups. (W.D.M.)

Phased array antenna matching: Simulation and optimization of a planar phased array of circular waveguide elements

NASA Technical Reports Server (NTRS)

Dudgeon, J. E.

1972-01-01

A computerized simulation of a planar phased array of circular waveguide elements is reported using mutual coupling and wide angle impedance matching in phased arrays. Special emphasis is given to circular polarization. The aforementioned computer program has as variable inputs: frequency, polarization, grid geometry, element size, dielectric waveguide fill, dielectric plugs in the waveguide for impedance matching, and dielectric sheets covering the array surface for the purpose of wide angle impedance matching. Parameter combinations are found which produce reflection peaks interior to grating lobes, while dielectric cover sheets are successfully employed to extend the usable scan range of a phased array. The most exciting results came from the application of computer aided optimization techniques to the design of this type of array.

Optimizing the G/T ratio of the DSS-13 34-meter beam-waveguide antenna

NASA Technical Reports Server (NTRS)

Esquivel, M. S.

1992-01-01

Calculations using Physical Optics computer software were done to optimize the gain-to-noise-temperature (G/T) ratio of Deep Space Station (DSS)-13, the Deep Space Network's (DSN's) 34-m beam-waveguide antenna, at X-band for operation with the ultra-low-noise amplifier maser system. A better G/T value was obtained by using a 24.2-dB far-field-gain smooth-wall dual-mode horn than by using the standard X-band 22.5-dB-gain corrugated horn.

Spoof Surface Plasmon Polaritons Power Divider with large Isolation.

PubMed

Zhou, Shiyan; Lin, Jing-Yu; Wong, Sai-Wai; Deng, Fei; Zhu, Lei; Yang, Yang; He, Yejun; Tu, Zhi-Hong

2018-04-13

Periodic corrugated metal structure is designed to support and propagate spoof surface plasmon polaritons (SSPPs) wave in the microwave frequencies. In this paper, firstly a plasmonic waveguide consisting of oval-ring shaped cells is proposed with the performance of high transmission efficiency in a wide frequency range. The coplanar waveguides (CPWs) with 50 Ω impedance are adopted to feed the energies or extract signals at both ends of the plasmonic waveguide. Then a well-isolated power divider is constructed based on the SSPPs waveguides aiming to equally split the energy of the SSPPs wave into two equal parts. The stepped-impedances are co-designed with the three input/output ports of the power divider to achieve the impedance-matching between the SSPPs waveguides and the coplanar waveguides. Besides, a single resistor is placed in the middle of two symmetrical half oval-rings to realize the isolation between the two output ports over the spectrum of 4.5-7.5 GHz. Finally, both plasmonic waveguide and the power divider are fabricated and tested to verify the predicted characteristics.

Methods of producing strain in a semiconductor waveguide and related devices

DOEpatents

Cox, Johathan Albert; Rakich, Peter Thomas

2016-02-16

Quasi-phase matched (QPM), semiconductor photonic waveguides include periodically-poled alternating first and second sections. The first sections exhibit a high degree of optical coupling (abbreviated "X.sup.2"), while the second sections have a low X.sup.2. The alternating first and second sections may comprise high-strain and low-strain sections made of different material states (such as crystalline and amorphous material states) that exhibit high and low X.sup.2 properties when formed on a particular substrate, and/or strained corrugated sections of different widths. The QPM semiconductor waveguides may be implemented as silicon-on-insulator (SOI), or germanium-on-silicon structures compatible with standard CMOS processes, or as silicon-on-sapphire (SOS) structures.

Spectral engineering for circular-side square microlasers.

PubMed

Weng, Hai-Zhong; Yang, Yue-De; Xiao, Jin-Long; Hao, You-Zeng; Huang, Yong-Zhen

2018-04-16

Spectral engineering has been demonstrated for the circular-side square microlasers with an output waveguide butt-coupled to one vertex. By carefully optimizing deformation parameter and waveguide connection angle, undesired high-order transverse modes are suppressed while the mode Q factors and the transverse-mode intervals are enhanced simultaneously for the low-order transverse modes. Dual-mode lasing with pure lasing spectra is realized experimentally for the circular-side square microlasers with side lengths of 16 μm, and the transverse mode intervals can be adjusted from 0.54 to 5.4 nm by changing the deformation parameter. Due to the enhanced mode confinement, single-mode lasing with a side-mode suppression-ratio of 36 dB is achieved for a 10μm-side-length circular-side square microlaser with a 1.5μm-wide waveguide.

Integrated plasmonic semi-circular launcher for dielectric-loaded surface plasmon-polariton waveguide.

PubMed

Li, Xiaowei; Huang, Lingling; Tan, Qiaofeng; Bai, Benfeng; Jin, Guofan

2011-03-28

A semi-circular plasmonic launcher integrated with dielectric-loaded surface plasmon-polaritons waveguide (DLSPPW) is proposed and analyzed theoretically, which can focus and efficiently couple the excited surface plasmon polaritons (SPPs) into the DLSPPW via the highly matched spatial field distribution with the waveguide mode in the focal plane. By tuning the incident angle or polarization of the illuminating beam, it is shown that the launcher may be conveniently used as a switch or a multiplexer that have potential applications in plasmonic circuitry. Furthermore, from an applicational point of view, it is analyzed how the coupling performance of the launcher can be further improved by employing multiple semi-circular slits.

Laser emission from diode-pumped Nd:YAG ceramic waveguide lasers realized by direct femtosecond-laser writing technique.

PubMed

Salamu, Gabriela; Jipa, Florin; Zamfirescu, Marian; Pavel, Nicolaie

2014-03-10

We report on realization of buried waveguides in Nd:YAG ceramic media by direct femtosecond-laser writing technique and investigate the waveguides laser emission characteristics under the pump with fiber-coupled diode lasers. Laser pulses at 1.06 μm with energy of 2.8 mJ for the pump with pulses of 13.1-mJ energy and continuous-wave output power of 0.49 W with overall optical efficiency of 0.13 were obtained from a 100-μm diameter circular cladding waveguide realized in a 0.7-at.% Nd:YAG ceramic. A circular waveguide of 50-μm diameter yielded laser pulses at 1.3 μm with 1.2-mJ energy.

Solid state nuclear magnetic resonance with magic-angle spinning and dynamic nuclear polarization below 25 K

PubMed Central

Thurber, Kent R.; Potapov, Alexey; Yau, Wai-Ming; Tycko, Robert

2012-01-01

We describe an apparatus for solid state nuclear magnetic resonance (NMR) with dynamic nuclear polarization (DNP) and magic-angle spinning (MAS) at 20–25 K and 9.4 Tesla. The MAS NMR probe uses helium to cool the sample space and nitrogen gas for MAS drive and bearings, as described earlier (Thurber et al., J. Magn. Reson. 2008) [1], but also includes a corrugated waveguide for transmission of microwaves from below the probe to the sample. With a 30 mW circularly polarized microwave source at 264 GHz, MAS at 6.8 kHz, and 21 K sample temperature, greater than 25-fold enhancements of cross-polarized 13C NMR signals are observed in spectra of frozen glycerol/water solutions containing the triradical dopant DOTOPA-TEMPO when microwaves are applied. As demonstrations, we present DNP-enhanced one-dimensional and two-dimensional 13C MAS NMR spectra of frozen solutions of uniformly 13C-labeled L-alanine and melittin, a 26-residue helical peptide that we have synthesized with four uniformly 13C-labeled amino acids. PMID:23238592

Solid state nuclear magnetic resonance with magic-angle spinning and dynamic nuclear polarization below 25 K.

PubMed

Thurber, Kent R; Potapov, Alexey; Yau, Wai-Ming; Tycko, Robert

2013-01-01

We describe an apparatus for solid state nuclear magnetic resonance (NMR) with dynamic nuclear polarization (DNP) and magic-angle spinning (MAS) at 20-25 K and 9.4 Tesla. The MAS NMR probe uses helium to cool the sample space and nitrogen gas for MAS drive and bearings, as described earlier, but also includes a corrugated waveguide for transmission of microwaves from below the probe to the sample. With a 30 mW circularly polarized microwave source at 264 GHz, MAS at 6.8 kHz, and 21 K sample temperature, greater than 25-fold enhancements of cross-polarized (13)C NMR signals are observed in spectra of frozen glycerol/water solutions containing the triradical dopant DOTOPA-TEMPO when microwaves are applied. As demonstrations, we present DNP-enhanced one-dimensional and two-dimensional (13)C MAS NMR spectra of frozen solutions of uniformly (13)C-labeled l-alanine and melittin, a 26-residue helical peptide that we have synthesized with four uniformly (13)C-labeled amino acids. Published by Elsevier Inc.

Test facility for the evaluation of microwave transmission components

NASA Astrophysics Data System (ADS)

Fong, C. G.; Poole, B. R.

1985-10-01

A Low Power Test Facility (LPTF) was developed to evaluate the performance of Electron Cyclotron Resonance Heating (ECRH) microwave transmission components for the Mirror Fusion Test Facility (MFTF-B). The facility generates 26 to 60 GHz in modes of TE01, TE02, or TE03 launched at power levels of 1/2 milliwatt. The propagation of the RF as it radiates from either transmitting or secondary reflecting microwave transmission components is recorded by a discriminating crystal detector mechanically manipulated at constant radius in spherical coordinates. The facility is used to test, calibrate, and verify the design of overmoded, circular waveguide components, quasi-optical reflecting elements before high power use. The test facility consists of microwave sources and metering components, such as VSWR, power and frequency meters, a rectangular TE10 to circular TE01 mode transducer, mode filter, circular TE01 to 2.5 in. diameter overmoded waveguide with mode converters for combination of TE01 to TE03 modes. This assembly then connects to a circular waveguide launcher or the waveguide component under test.

Mechanisms of amplification of ultrashort electromagnetic pulses in gyrotron traveling wave tube with helically corrugated waveguide

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ginzburg, N. S., E-mail: ginzburg@appl.sci-nnov.ru; Zaslavsky, V. Yu.; Nizhny Novgorod State University, 23 Gagarin Ave., 603950 Nizhny Novgorod

A time-domain self consistent theory of a gyrotron traveling wave tube with a helically corrugated operating waveguide has been developed. Based on this model, the process of short pulse amplification was studied in regimes of grazing and intersection of the dispersion curves of the electromagnetic wave and the electron beam. In the first case, the possibility of amplification without pulse form distortion was demonstrated for the pulse spectrum width of the order of the gain bandwidth. In the second case, when the electrons' axial velocity was smaller than the wave's group velocity, it was shown that the slippage of themore » incident signal with respect to the electron beam provides feeding of the signal by “fresh” electrons without initial modulation. As a result, the amplitude of the output pulse can exceed the amplitude of its saturated value for the case of the grazing regime, and, for optimal parameters, the peak output power can be even larger than the kinetic power of the electron beam.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xu, Chen; Tantawi, Sami; Wang, Juwen

We present in this paper a new design of dual circular polarizer. This innovative design converts radiofrequency (rf) energy from TE10 mode in a rectangular waveguide to two polarized TE11 modes in a circular waveguide. A reflection less than ₋20 db is achieved and breakdown field is less than 42 MV/m at input of 1 MW. Meanwhile, this polarizer has a megahertz bandwidth, and the thermal stability is also discussed. This device can be used for broadcasting and receiving the circular polarized signals.

The Modeling of Viscoelastic Circular Plates for Use as Waveguide Absorbers

DTIC Science & Technology

1988-09-01

oncituoe Security Ciasstircation) X THE MODELING OF VISCOELASTIC CIRCULAR PLATES FOR USE AS WAVEGUIDE ABSORBERS C 12 PERSONAL AUTmO ?S) -Hettema...33mvU3dT’U Figure 67. Experimental Jmainiey Part ot the Driving Point Jmpedancs of a 6 in Radius Elastic Plate, With and Without aaker and Mount Conecon, In

Y-junctions based on circular depressed-cladding waveguides fabricated with femtosecond pulses in Nd:YAG crystal: A route to integrate complex photonic circuits in crystals

NASA Astrophysics Data System (ADS)

Ajates, Javier G.; Romero, Carolina; Castillo, Gabriel R.; Chen, Feng; Vázquez de Aldana, Javier R.

2017-10-01

We have designed and fabricated photonic structures such as, Y-junctions (one of the basic building blocks for construction any integrated photonic devices) and Mach-Zehnder interferometers, based on circular depressed-cladding waveguides by direct femtosecond laser irradiation in Nd:YAG crystal. The waveguides were optically characterized at 633 nm, showing nearly mono-modal behaviour for the selected waveguide radius (9 μm). The effect of the splitting angle in the Y structures was investigated finding a good preservation of the modal profiles up to more than 2°, with 1 dB of additional losses in comparison with straight waveguides. The dependence with polarization of these splitters keeps in a reasonable low level. Our designs pave the way for the fabrication of arbitrarily complex 3D photonic circuits in crystals with cladding waveguides.

FIBER AND INTEGRATED OPTICS: Anisotropic waveguides with an elliptic stress-inducing cladding and a circular core

NASA Astrophysics Data System (ADS)

Arutyunyan, Z. É.; Grudinin, A. B.; Gur'yanov, A. N.; Gusovskiĭ, D. D.; Dianov, Evgenii M.; Ignat'ev, S. V.; Smirnov, O. B.

1990-10-01

A technology of fabrication of anisotropic single-mode fiber waveguides with an elliptic stress-inducing cladding and a circular core was developed. This technology was used to make fiber waveguides with a birefringence (1-3) × 10 - 4, a coefficient representing the coupling between the polarization modes h = (5-7) × 10 - 5 m - 1, and optical losses a = 0.5 dB/km in the vicinity of 1.6 μm. A comparison was made of the experimental data with the results of a theoretical analysis. It was found that certain mechanisms restricted the ability of these waveguides to maintain a constant polarization of the injected linearly polarized radiation.

24-Way Radial Power Combiner/Divider for 31 to 36 GHz

NASA Technical Reports Server (NTRS)

Epp, Larry; Hoppe, Daniel; Khan, Abdur; Kelley, Daniel

2008-01-01

The figure shows a prototype radial power-combining waveguide structure, capable of operation at frequencies from 31 to 36 GHz, that features an unusually large number (N = 24) of combining (input) ports. The combination of wide-band operation and large N is achieved by incorporating several enhancements over a basic radial power-combiner design. In addition, the structure can be operated as a power divider by reversing the roles of the input and output ports. In this structure, full-height waveguides at the combining ports are matched in impedance to reduced-height radial waveguides inside the combiner base. This match is effected by impedance-transforming stepped waveguide sections. This matching scheme is essential to achievement of large N because N is limited by the height of the waveguides in the base. Power is coupled from the 24 reduced- height radial waveguides into the TE01 mode of a circular waveguide in the base with the help of a matching post at the bottom of the base. ( TE signifies transverse electric, the first subscript is the azimuthal mode number, and the second subscript is the radial mode number.) More specifically, the matching post matches the reflections from the walls of the 24 reduced-height waveguides and enables the base design to exceed the bandwidth requirement. After propagating along the circular waveguide, the combined power is coupled, via a mode transducer, to a rectangular waveguide output port. The mode transducer is divided into three sections, each sized and shaped as part of an overall design to satisfy the mode-conversion and output-coupling requirements while enabling the circular waveguide to be wide enough for combining the 24 inputs over the frequency range of 31 to 36 GHz. During the design process, it was found that two different rectangular waveguide outputs could be accommodated through modification of only the first section of the mode converter, thereby enabling operation in multiple frequency ranges.

Nonlinear equation of the modes in circular slab waveguides and its application.

PubMed

Zhu, Jianxin; Zheng, Jia

2013-11-20

In this paper, circularly curved inhomogeneous waveguides are transformed into straight inhomogeneous waveguides first by a conformal mapping. Then, the differential transfer matrix method is introduced and adopted to deduce the exact dispersion relation for modes. This relation itself is complex and difficult to solve, but it can be approximated by a simpler nonlinear equation in practical applications, which is close to the exact relation and quite easy to analyze. Afterward, optimized asymptotic solutions are obtained and act as initial guesses for the following Newton's iteration. Finally, very accurate solutions are achieved in the numerical experiment.

Dispersion relation and electron acceleration in the combined circular and elliptical metallic-dielectric waveguide filled by plasma

NASA Astrophysics Data System (ADS)

Abdoli-Arani, A.; Montazeri, M. M.

2018-04-01

Two special types of metallic waveguide having dielectric cladding and plasma core including the combined circular and elliptical structure are studied. Longitudinal and transverse field components in the different regions are obtained. Applying the boundary conditions, dispersion relations of the electromagnetic waves in the structures are obtained and then plotted. The acceleration of an injected external relativistic electron in the considered waveguides is studied. The obtained differential equations related to electron motion are solved by the fourth-order Runge-Kutta method. Numerical computations are made, and the results are graphically presented.

A Hybrid Circuit for Spoof Surface Plasmons and Spatial Waveguide Modes to Reach Controllable Band-Pass Filters

PubMed Central

Zhang, Qian; Zhang, Hao Chi; Wu, Han; Cui, Tie Jun

2015-01-01

We propose a hybrid circuit for spoof surface plasmon polaritons (SPPs) and spatial waveguide modes to develop new microwave devices. The hybrid circuit includes a spoof SPP waveguide made of two anti-symmetric corrugated metallic strips and a traditional substrate integrated waveguide (SIW). From dispersion relations, we show that the electromagnetic waves only can propagate through the hybrid circuit when the operating frequency is less than the cut-off frequency of the SPP waveguide and greater than the cut-off frequency of SIW, generating efficient band-pass filters. We demonstrate that the pass band is controllable in a large range by designing the geometrical parameters of SPP waveguide and SIW. Full-wave simulations are provided to show the large adjustability of filters, including ultra wideband and narrowband filters. We fabricate a sample of the new hybrid device in the microwave frequencies, and measurement results have excellent agreements to numerical simulations, demonstrating excellent filtering characteristics such as low loss, high efficiency, and good square ratio. The proposed hybrid circuit gives important potential to accelerate the development of plasmonic integrated functional devices and circuits in both microwave and terahertz frequencies. PMID:26552584

A Hybrid Circuit for Spoof Surface Plasmons and Spatial Waveguide Modes to Reach Controllable Band-Pass Filters.

PubMed

Zhang, Qian; Zhang, Hao Chi; Wu, Han; Cui, Tie Jun

2015-11-10

We propose a hybrid circuit for spoof surface plasmon polaritons (SPPs) and spatial waveguide modes to develop new microwave devices. The hybrid circuit includes a spoof SPP waveguide made of two anti-symmetric corrugated metallic strips and a traditional substrate integrated waveguide (SIW). From dispersion relations, we show that the electromagnetic waves only can propagate through the hybrid circuit when the operating frequency is less than the cut-off frequency of the SPP waveguide and greater than the cut-off frequency of SIW, generating efficient band-pass filters. We demonstrate that the pass band is controllable in a large range by designing the geometrical parameters of SPP waveguide and SIW. Full-wave simulations are provided to show the large adjustability of filters, including ultra wideband and narrowband filters. We fabricate a sample of the new hybrid device in the microwave frequencies, and measurement results have excellent agreements to numerical simulations, demonstrating excellent filtering characteristics such as low loss, high efficiency, and good square ratio. The proposed hybrid circuit gives important potential to accelerate the development of plasmonic integrated functional devices and circuits in both microwave and terahertz frequencies.

Corrugated metal surface with pillars for terahertz surface plasmon polariton waveguide components

NASA Astrophysics Data System (ADS)

Zhang, Ying; Xu, Yuehong; Tian, Chunxiu; Xu, Quan; Zhang, Xueqian; Li, Yanfeng; Zhang, Xixiang; Han, Jiaguang; Zhang, Weili

2018-01-01

In the terahertz regime, due to perfect conductivity of most metals, it is hard to realize a strong confinement of Surface plasmon polaritons (SPPs) although a propagation loss could be sufficiently low. We experimentally demonstrated a structure with periodic pillars arranged on a thin metal surface that supports bound modes of spoof SPPs at terahertz (THz) frequencies. By using scanning near-field THz microscopy, the electric field distribution above the metal surface within a distance of 130 μm was mapped. The results proved that this structure could guide spoof SPPs propagating along subwavelength waveguides, and at the same time reduce field expansion into free space. Further, for the development of integrated optical circuits, several components including straight waveguide, S-bend, Y-splitter and directional couplers were designed and characterized by the same method. We believe that the waveguide components proposed here will pave a new way for the development of flexible, wideband and compact photonic circuits operating at THz frequencies.

FIBER OPTICS: Investigation of the spectral dependences of some of the polarization characteristics of fiber waveguides with an elliptic stress-inducing cladding and a circular core

NASA Astrophysics Data System (ADS)

Arutyunyan, Z. É.; Grudinin, A. B.; Gur'yanov, A. N.; Gusovskiĭ, D. D.; Dianov, Evgenii M.; Ignat'ev, S. V.; Smirnov, O. B.; Surin, S. Yu

1991-01-01

An experimental investigation was made of the spectral dependences of the modal birefringence B, of the polarization dispersion τp, and of the difference Dx-Dy between the chromatic dispersions of polarization modes in fiber waveguides with an elliptic stress-inducing cladding, a second circular buffer cladding, and a circular core. The investigation was carried out in the wavelength range 1.15-1.75 μm. The magnitude of the changes in B, τp, and Dx-Dy depended on the dimensions of the buffer cladding. The dependences obtained were explained satisfactorily by an analysis of the similarity of the distributions of the intensity of the fundamental mode and of the difference of the stresses along the optic axes of the investigated fiber waveguides.

High-Aperture-Efficiency Horn Antenna

NASA Technical Reports Server (NTRS)

Pickens, Wesley; Hoppe, Daniel; Epp, Larry; Kahn, Abdur

2005-01-01

A horn antenna (see Figure 1) has been developed to satisfy requirements specific to its use as an essential component of a high-efficiency Ka-band amplifier: The combination of the horn antenna and an associated microstrip-patch antenna array is required to function as a spatial power divider that feeds 25 monolithic microwave integrated-circuit (MMIC) power amplifiers. The foregoing requirement translates to, among other things, a further requirement that the horn produce a uniform, vertically polarized electromagnetic field in its patches identically so that the MMICs can operate at maximum efficiency. The horn is fed from a square waveguide of 5.9436-mm-square cross section via a transition piece. The horn features cosine-tapered, dielectric-filled longitudinal corrugations in its vertical walls to create a hard boundary condition: This aspect of the horn design causes the field in the horn aperture to be substantially vertically polarized and to be nearly uniform in amplitude and phase. As used here, cosine-tapered signifies that the depth of the corrugations is a cosine function of distance along the horn. Preliminary results of finite-element simulations of performance have shown that by virtue of the cosine taper the impedance response of this horn can be expected to be better than has been achieved previously in a similar horn having linearly tapered dielectric- filled longitudinal corrugations. It is possible to create a hard boundary condition by use of a single dielectric-filled corrugation in each affected wall, but better results can be obtained with more corrugations. Simulations were performed for a one- and a three-corrugation cosine-taper design. For comparison, a simulation was also performed for a linear- taper design (see Figure 2). The three-corrugation design was chosen to minimize the cost of fabrication while still affording acceptably high performance. Future designs using more corrugations per wavelength are expected to provide better field responses and, hence, greater aperture efficiencies.

Analysis of three-dimensional-cavity-backed aperture antennas using a Combined Finite Element Method/Method of Moments/Geometrical Theory of Diffraction technique

NASA Technical Reports Server (NTRS)

Reddy, C. J.; Deshpande, M. D.; Cockrell, C. R.; Beck, F. B.

1995-01-01

A combined finite element method (FEM) and method of moments (MoM) technique is presented to analyze the radiation characteristics of a cavity-fed aperture in three dimensions. Generalized feed modeling has been done using the modal expansion of fields in the feed structure. Numerical results for some feeding structures such as a rectangular waveguide, circular waveguide, and coaxial line are presented. The method also uses the geometrical theory of diffraction (GTD) to predict the effect of a finite ground plane on radiation characteristics. Input admittance calculations for open radiating structures such as a rectangular waveguide, a circular waveguide, and a coaxial line are shown. Numerical data for a coaxial-fed cavity with finite ground plane are verified with experimental data.

Compact Feeding Network for Array Radiations of Spoof Surface Plasmon Polaritons

NASA Astrophysics Data System (ADS)

Xu, Jun Jun; Yin, Jia Yuan; Zhang, Hao Chi; Cui, Tie Jun

2016-03-01

We propose a splitter feeding network for array radiations of spoof surface plasmon polaritons (SPPs), which are guided by ultrathin corrugated metallic strips. Based on the coupled mode theory, SPP fields along a single waveguide in a certain frequency range can be readily coupled into two adjacent branch waveguides with the same propagation constants. We propose to load U-shaped particles anti-symmetrically at the ends of such two branch waveguides, showing a high integration degree of the feeding network. By controlling linear phase modulations produced by the U-shaped particle chain, we demonstrate theoretically and experimentally that the SPP fields based on bound modes can be efficiently radiated to far fields in broadside direction. The proposed method shows that the symmetry of electromagnetic field modes can be exploited to the SPP transmission network, providing potential solutions to compact power dividers and combiners for microwave and optical devices and systems.

Femtosecond-laser-written Tm:KLu(WO₄)₂ waveguide lasers.

PubMed

Kifle, Esrom; Mateos, Xavier; de Aldana, Javier Rodríguez Vázquez; Ródenas, Airan; Loiko, Pavel; Choi, Sun Yung; Rotermund, Fabian; Griebner, Uwe; Petrov, Valentin; Aguiló, Magdalena; Díaz, Francesc

2017-03-15

Depressed-index channel waveguides with a circular and photonic crystal cladding structures are prepared in a bulk monoclinic Tm:KLu(WO₄)₂ crystal by 3D direct femtosecond laser writing. The channel waveguide structures are characterized and laser operation is achieved using external mirrors. In the continuous-wave mode, the maximum output power of 46 mW is achieved at 1912 nm corresponding to a slope efficiency of 15.2% and a laser threshold of only 21 mW. Passive Q-switching of a waveguide with a circular cladding is realized using single-walled carbon nanotubes. Stable 7 nJ/50 ns pulses are achieved at a repetition rate of 1.48 MHz. This first demonstration of ∼2  μm fs-laser-written waveguide lasers based on monoclinic double tungstates is promising for further lasers of this type doped with Tm³⁺ and Ho³⁺  ions.

Wavelength shifts of cladding-mode resonance in corrugated long-period fiber gratings under torsion.

PubMed

Ivanov, Oleg V; Wang, Lon A

2003-05-01

A finite deformation theory of elasticity and a theory of nonlinear photoelasticity are applied to describe the wavelength shifts of cladding-mode resonance in corrugated long-period fiber gratings under torsion. The deformation of fiber is found by use of the Murnaghan model of a solid elastic body. The quadratic photoelastic effect that is proportional to the second-order displacement gradient is investigated and compared with the classical photoelastic effect. The electromagnetic field in the twisted corrugated structure is presented as a superposition of circularly polarized modes of the etched fiber section. The wavelength shift is found to be proportional to the square of the twist angle. As predicted by our theory, a wavelength shift of the same nature has been found in a conventionally photoinduced long-period fiber grating.

Femtosecond laser inscribed cladding waveguide lasers in Nd:LiYF4 crystals

NASA Astrophysics Data System (ADS)

Li, Shi-Ling; Huang, Ze-Ping; Ye, Yong-Kai; Wang, Hai-Long

2018-06-01

Depressed circular cladding, buried waveguides were fabricated in Nd:LiYF4 crystals with an ultrafast Yb-doped fiber master-oscillator power amplifier laser. Waveguides were optimized by varying the laser writing conditions, such as pulse energy, focus depth, femtosecond laser polarization and scanning velocity. Under optical pump at 799 nm, cladding waveguides showed continuous-wave laser oscillation at 1047 nm. Single- and multi-transverse modes waveguide laser were realized by varying the waveguide diameter. The maximum output power in the 40 μm waveguide is ∼195 mW with a slope efficiency of 34.3%. The waveguide lasers with hexagonal and cubic cladding geometry were also realized.

Plasmonic micropolarizers for full Stokes vector imaging

NASA Astrophysics Data System (ADS)

Peltzer, J. J.; Bachman, K. A.; Rose, J. W.; Flammer, P. D.; Furtak, T. E.; Collins, R. T.; Hollingsworth, R. E.

2012-06-01

Polarimetric imaging using micropolarizers integrated on focal plane arrays has previously been limited to the linear components of the Stokes vector because of the lack of an effective structure with selectivity to circular polarization. We discuss a plasmonic micropolarizing filter that can be tuned for linear or circular polarization as well as wavelength selectivity from blue to infrared (IR) through simple changes in its horizontal geometry. The filter consists of a patterned metal film with an aperture in a central cavity that is surrounded by gratings that couple to incoming light. The aperture and gratings are covered with a transparent dielectric layer to form a surface plasmon slab waveguide. A metal cap covers the aperture and forms a metal-insulator-metal (MIM) waveguide. Structures with linear apertures and gratings provide sensitivity to linear polarization, while structures with circular apertures and spiral gratings give circular polarization selectivity. Plasmonic TM modes are transmitted down the MIM waveguide while the TE modes are cut off due to the sub-wavelength dielectric thickness, providing the potential for extremely high extinction ratios. Experimental results are presented for micropolarizers fabricated on glass or directly into the Ohmic contact metallization of silicon photodiodes. Extinction ratios for linear polarization larger than 3000 have been measured.

Application of Plasma Waveguides to High Energy Accelerators

DOE Office of Scientific and Technical Information (OSTI.GOV)

Milchberg, Howard M

2013-03-30

The eventual success of laser-plasma based acceleration schemes for high-energy particle physics will require the focusing and stable guiding of short intense laser pulses in reproducible plasma channels. For this goal to be realized, many scientific issues need to be addressed. These issues include an understanding of the basic physics of, and an exploration of various schemes for, plasma channel formation. In addition, the coupling of intense laser pulses to these channels and the stable propagation of pulses in the channels require study. Finally, new theoretical and computational tools need to be developed to aid in the design and analysismore » of experiments and future accelerators. Here we propose a 3-year renewal of our combined theoretical and experimental program on the applications of plasma waveguides to high-energy accelerators. During the past grant period we have made a number of significant advances in the science of laser-plasma based acceleration. We pioneered the development of clustered gases as a new highly efficient medium for plasma channel formation. Our contributions here include theoretical and experimental studies of the physics of cluster ionization, heating, explosion, and channel formation. We have demonstrated for the first time the generation of and guiding in a corrugated plasma waveguide. The fine structure demonstrated in these guides is only possible with cluster jet heating by lasers. The corrugated guide is a slow wave structure operable at arbitrarily high laser intensities, allowing direct laser acceleration, a process we have explored in detail with simulations. The development of these guides opens the possibility of direct laser acceleration, a true miniature analogue of the SLAC RF-based accelerator. Our theoretical studies during this period have also contributed to the further development of the simulation codes, Wake and QuickPIC, which can be used for both laser driven and beam driven plasma based acceleration schemes. We will continue our development of advanced simulation tools by modifying the QuickPIC algorithm to allow for the simulation of plasma particle pick-up by the wake fields. We have also performed extensive simulations of plasma slow wave structures for efficient THz generation by guided laser beams or accelerated electron beams. We will pursue experimental studies of direct laser acceleration, and THz generation by two methods, ponderomotive-induced THz polarization, and THz radiation by laser accelerated electron beams. We also plan to study both conventional and corrugated plasma channels using our new 30 TW in our new lab facilities. We will investigate production of very long hydrogen plasma waveguides (5 cm). We will study guiding at increasing power levels through the onset of laser-induced cavitation (bubble regime) to assess the role played by the preformed channel. Experiments in direct acceleration will be performed, using laser plasma wakefields as the electron injector. Finally, we will use 2-colour ionization of gases as a high frequency THz source (<60 THz) in order for femtosecond measurements of low plasma densities in waveguides and beams.« less

Multi-layer topological transmissions of spoof surface plasmon polaritons.

PubMed

Pan, Bai Cao; Zhao, Jie; Liao, Zhen; Zhang, Hao Chi; Cui, Tie Jun

2016-03-04

Spoof surface plasmon polaritons (SPPs) in microwave frequency provide a high field confinement in subwavelength scale and low-loss and flexible transmissions, which have been widely used in novel transmission waveguides and functional devices. To play more important roles in modern integrated circuits and systems, it is necessary and helpful for the SPP modes to propagate among different layers of devices and chips. Owing to the highly confined property and organized near-field distribution, we show that the spoof SPPs could be easily transmitted from one layer into another layer via metallic holes and arc-shaped transitions. Such designs are suitable for both the ultrathin and flexible single-strip SPP waveguide and double-strip SPP waveguide for active SPP devices. Numerical simulations and experimental results demonstrate the broadband and high-efficiency multi-layer topological transmissions with controllable absorption that is related to the superposition area of corrugated metallic strips. The transmission coefficient of single-strip SPP waveguide is no worse than -0.8 dB within frequency band from 2.67 GHz to 10.2 GHz while the transmission of double-strip SPP waveguide keeps above -1 dB within frequency band from 2.26 GHz to 11.8 GHz. The proposed method will enhance the realizations of highly complicated plasmonic integrated circuits.

Resent Status of ITER Equatorial Launcher Development

DOE Office of Scientific and Technical Information (OSTI.GOV)

Takahashi, K.; Kajiwara, K.; Kasugai, A.

2009-11-26

The ITER equatorial launcher is divided into a front shield and a port plug. The front shield is composed of fourteen blanket shield modules so as to form three openings for the injection of mm-wave beams into plasma. Twenty-four waveguide transmission lines, internal shields, cooling pipes and so on are installed in the port plug. The transmission lines consist of the corrugated waveguides, miter bends and the free space propagation region utilizing two mirrors in front of the waveguide outlet. The analysis of mm-wave beam propagation in the region shows that the transmission efficiency more than 99.5% is attained. Themore » high power experiments of the launcher mock-up have been carried out and the measured field patterns at each mirror and the outlet of the launcher are agreed with the calculations. It is concluded that the transmission line components in the launcher mock-up are fabricated as designed and the present mm-wave design in the launcher is feasible.« less

Radiation loss of planar surface plasmon polaritons transmission lines at microwave frequencies.

PubMed

Xu, Zhixia; Li, Shunli; Yin, Xiaoxing; Zhao, Hongxin; Liu, Leilei

2017-07-21

Radiation loss of a typical spoof surface plasmon polaritons (SSPPs) transmission line (TL) is investigated in this paper. A 325 mm-long SSPPs TL is designed and fabricated. Simulated results show that radiation loss contributes more to transmission loss than dielectric loss and conductor loss from 2 GHz to 10 GHz. Radiation loss of the SSPPs TL could be divided into two parts, one is caused by the input mode converter, and the other is caused by the corrugated metallic strip. This paper explains mechanisms of radiation loss from different parts, designs a loaded SSPPs TL with a series of resistors to absorb electromagnetic energy on corrugated metallic strip, and then discriminates radiation loss from the input mode converter, proposes the concept of average radiation length (ARL) to evaluate radiation loss from SSPPs of finite length, and concludes that radiation loss is mainly caused by corrugated structure of finite length at low frequency band and by the input mode converter at high frequency band. To suppress radiation loss, a mixed slow wave TL based on the combination of coplanar waveguides (CPWs) and SSPPs is presented. The designed structure, sample fabrication and experimental verification are discussed.

Simultaneous RGB lasing from a single-chip polymer device.

PubMed

Yamashita, Kenichi; Takeuchi, Nobutaka; Oe, Kunishige; Yanagi, Hisao

2010-07-15

This Letter describes the fabrication and operation of a single-chip white-laser device. The laser device has a multilayered structure consisting of three laser layers. Each laser layer comprises polymer claddings and a waveguide core doped with organic dye. In each laser layer, grating corrugations were fabricated by UV-nanoimprint lithography that act as distributed-feedback cavity structures. Under optical pumping, lasing output with red, green, and blue colors was simultaneously obtained from the sample edge.

Improved Modeling of Open Waveguide Aperture Radiators for use in Conformal Antenna Arrays

NASA Astrophysics Data System (ADS)

Nelson, Gregory James

Open waveguide apertures have been used as radiating elements in conformal arrays. Individual radiating element model patterns are used in constructing overall array models. The existing models for these aperture radiating elements may not accurately predict the array pattern for TEM waves which are not on boresight for each radiating element. In particular, surrounding structures can affect the far field patterns of these apertures, which ultimately affects the overall array pattern. New models of open waveguide apertures are developed here with the goal of accounting for the surrounding structure effects on the aperture far field patterns such that the new models make accurate pattern predictions. These aperture patterns (both E plane and H plane) are measured in an anechoic chamber and the manner in which they deviate from existing model patterns are studied. Using these measurements as a basis, existing models for both E and H planes are updated with new factors and terms which allow the prediction of far field open waveguide aperture patterns with improved accuracy. These new and improved individual radiator models are then used to predict overall conformal array patterns. Arrays of open waveguide apertures are constructed and measured in a similar fashion to the individual aperture measurements. These measured array patterns are compared with the newly modeled array patterns to verify the improved accuracy of the new models as compared with the performance of existing models in making array far field pattern predictions. The array pattern lobe characteristics are then studied for predicting fully circularly conformal arrays of varying radii. The lobe metrics that are tracked are angular location and magnitude as the radii of the conformal arrays are varied. A constructed, measured array that is close to conforming to a circular surface is compared with a fully circularly conformal modeled array pattern prediction, with the predicted lobe angular locations and magnitudes tracked, plotted and tabulated. The close match between the patterns of the measured array and the modeled circularly conformal array verifies the validity of the modeled circularly conformal array pattern predictions.

The waveguide laser - A review

NASA Technical Reports Server (NTRS)

Degnan, J. J.

1976-01-01

The present article reviews the fundamental physical principles essential to an understanding of waveguide gas and liquid lasers, and the current technological state of these devices. At the present time, waveguide laser transitions span the visible through submillimeter regions of the wavelength spectrum. The introduction discusses the many applications of waveguide lasers and the wide variety of laser configurations that are possible. Section 1 summarizes the properties of modes in hollow dielectric waveguides of circular, rectangular, and planar cross section. Section 2 considers various approaches to optical feedback including internal and external mirror Fabry-Perot type resonators, hollow waveguide distributed feedback structures, and ring-resonant configurations. Section 3 discusses those aspects of molecular kinetic and laser theory pertinent to the design and optimization of waveguide gas lasers.

Hollow-cylinder waveguide isolators for use at millimeter wavelengths

NASA Technical Reports Server (NTRS)

Kanda, M.; May, W. G.

1974-01-01

A semiconductor waveguide isolator consisting of a hollow column of a semiconductor mounted coaxially is considered in a circular waveguide in a longitudinal dc magnetic field. An elementary and physical analysis based on the excitation of plane waves in the guide and a more rigorous mode matching analysis are presented. These theoretical predictions are compared with experimental results for an InSb isolator at 94GHz and 75 K.

Polymer/silica hybrid integration waveguide Bragg grating based on surface plasmon polaritons.

PubMed

Tian, Liang; Wang, Fei; Wu, Yuanda; Sun, Xiaoqiang; Yi, Yunji; Zhang, Daming

2018-05-01

We proposed a device composed of a Bragg grating and a long-range surface plasmon polariton waveguide. The waveguide is formed by embedding a thin Au stripe in negative UV photoresist (SU-8 2005). The corrugated grating structure is created on a silica substrate using contact lithography and inductively coupled plasma etching, which is transferred onto the SU-8 2005 film by a spin coating process, producing a periodic modulation of refractive index along the waveguide. We achieve a transmission peak with an extinction ratio of 17 dB and a 3-dB bandwidth of 0.9 nm at a wavelength of 1575.2 nm. We achieve a reflection peak with a side-mode suppression ratio of 9.7 dB, a 3-dB bandwidth of 0.9 nm at a wavelength of 1575.2 nm when the heating electrode isn't working. The shift of the reflection peak with heating power over the range 0-6 mW is approximately 2.9 nm. This thermal dependence exhibits an average slope of -0.48  nm/mW.

Circular free-electron laser

DOEpatents

Brau, Charles A.; Kurnit, Norman A.; Cooper, Richard K.

1984-01-01

A high efficiency, free electron laser utilizing a circular relativistic electron beam accelerator and a circular whispering mode optical waveguide for guiding optical energy in a circular path in the circular relativistic electron beam accelerator such that the circular relativistic electron beam and the optical energy are spatially contiguous in a resonant condition for free electron laser operation. Both a betatron and synchrotron are disclosed for use in the present invention. A free electron laser wiggler is disposed around the circular relativistic electron beam accelerator for generating a periodic magnetic field to transform energy from the circular relativistic electron beam to optical energy.

Hyperbolic-cosine waveguide tapers and oversize rectangular waveguide for reduced broadband insertion loss in W-band electron paramagnetic resonance spectroscopy. II. Broadband characterization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sidabras, Jason W.; Anderson, James R.; Mainali, Laxman

Experimental results have been reported on an oversize rectangular waveguide assembly operating nominally at 94 GHz. It was formed using commercially available WR28 waveguide as well as a pair of specially designed tapers with a hyperbolic-cosine shape from WR28 to WR10 waveguide [R. R. Mett et al., Rev. Sci. Instrum. 82, 074704 (2011)]. The oversize section reduces broadband insertion loss for an Electron Paramagnetic Resonance (EPR) probe placed in a 3.36 T magnet. Hyperbolic-cosine tapers minimize reflection of the main mode and the excitation of unwanted propagating waveguide modes. Oversize waveguide is distinguished from corrugated waveguide, overmoded waveguide, or quasi-opticmore » techniques by minimal coupling to higher-order modes. Only the TE{sub 10} mode of the parent WR10 waveguide is propagated. In the present work, a new oversize assembly with a gradual 90° twist was implemented. Microwave power measurements show that the twisted oversize waveguide assembly reduces the power loss in the observe and pump arms of a W-band bridge by an average of 2.35 dB and 2.41 dB, respectively, over a measured 1.25 GHz bandwidth relative to a straight length of WR10 waveguide. Network analyzer measurements confirm a decrease in insertion loss of 2.37 dB over a 4 GHz bandwidth and show minimal amplitude distortion of approximately 0.15 dB. Continuous wave EPR experiments confirm these results. The measured phase variations of the twisted oversize waveguide assembly, relative to an ideal distortionless transmission line, are reduced by a factor of two compared to a straight length of WR10 waveguide. Oversize waveguide with proper transitions is demonstrated as an effective way to increase incident power and the return signal for broadband EPR experiments. Detailed performance characteristics, including continuous wave experiment using 1 μM 2,2,6,6-tetramethylpiperidine-1-oxyl in aqueous solution, provided here serve as a benchmark for other broadband low-loss probes in millimeter-wave EPR bridges.« less

Terahertz near-field imaging using subwavelength plasmonic apertures and a quantum cascade laser source.

PubMed

Baragwanath, Adam J; Freeman, Joshua R; Gallant, Andrew J; Zeitler, J Axel; Beere, Harvey E; Ritchie, David A; Chamberlain, J Martyn

2011-07-01

The first demonstration, to our knowledge, of near-field imaging using subwavelength plasmonic apertures with a terahertz quantum cascade laser source is presented. "Bull's-eye" apertures, featuring subwavelength circular apertures flanked by periodic annular corrugations were created using a novel fabrication method. A fivefold increase in intensity was observed for plasmonic apertures over plain apertures of the same diameter. Detailed studies of the transmitted beam profiles were undertaken for apertures with both planarized and corrugated exit facets, with the former producing spatially uniform intensity profiles and subwavelength spatial resolution. Finally, a proof-of-concept imaging experiment is presented, where an inhomogeneous pharmaceutical drug coating is investigated.

Distributed feedback guided surface acoustic wave microresonator

NASA Astrophysics Data System (ADS)

Golan, G.; Griffel, G.; Seidman, A.; Croitoru, N.

1989-08-01

Surface acoustic wave resonators have been used in a number of applications: high-Q frequency filtering, very accurate frequency sources, etc. A major disadvantage of conventional resonators is their large dimensions, which makes them inadequate for integrated acoustics applications. In order to overcome these size limitations a new type of microresonator was designed, developed, and tested. In this paper, theoretical calculations and measurements on two kinds of such devices (a corrugated waveguide filter and a microresonator structure) are presented and their possible applications are discussed.

Analysis of the ITER low field side reflectometer transmission line system.

PubMed

Hanson, G R; Wilgen, J B; Bigelow, T S; Diem, S J; Biewer, T M

2010-10-01

A critical issue in the design of the ITER low field side reflectometer is the transmission line (TL) system. A TL connects each launcher to a diagnostic instrument. Each TL will typically consist of ∼42 m of corrugated waveguide and up to ten miter bends. Important issues for the performance of the TL system are mode conversion and reflections. Minimizing these issues are critical to minimizing standing waves and phase errors. The performance of TL system is analyzed and recommendations are given.

Intermode light diffusion in multimode optical waveguides with rough surfaces.

PubMed

Stepanov, S; Chaikina, E I; Leskova, T A; Méndez, E R

2005-06-01

A theoretical analysis of incoherent intermode light power diffusion in multimode dielectric waveguides with rough (corrugated) surfaces is presented. The correlation length a of the surface-profile variations is assumed to be sufficiently large (a less less than lambda/2pi) to permit light scattering into the outer space only from the modes close to the critical angles of propagation and yet sufficiently small (a less less than d, where d is the average width of the waveguide) to permit direct interaction between a given mode and a large number of neighboring ones. The cases of a one-dimensional (1D) slab waveguide and a two-dimensional cylindrical waveguide (optical fiber) are analyzed, and we find that in both cases the partial differential equations that govern the evolution of the angular light power profile propagating along the waveguide are 1D and of the diffusion type. However, whereas in the former case the effective conductivity coefficient proves to be linearly dependent on the transverse-mode wave number, in the latter one the linear dependence is for the effective diffusion coefficient. The theoretical predictions are in reasonable agreement with experimental results for the intermode power diffusion in multimode (700 x 700) optical fibers with etched surfaces. The characteristic length of dispersion of a narrow angular power profile evaluated from the correlation length and standard deviation of heights of the surface profile proved to be in good agreement with the experimentally observed changes in the output angular power profiles.

Corrugation Instability of a Coronal Arcade

NASA Astrophysics Data System (ADS)

Klimushkin, D. Y.; Nakariakov, V. M.; Mager, P. N.; Cheremnykh, O. K.

2017-12-01

We analyse the behaviour of linear magnetohydrodynamic perturbations of a coronal arcade modelled by a half-cylinder with an azimuthal magnetic field and non-uniform radial profiles of the plasma pressure, temperature, and the field. Attention is paid to the perturbations with short longitudinal (in the direction along the arcade) wavelengths. The radial structure of the perturbations, either oscillatory or evanescent, is prescribed by the radial profiles of the equilibrium quantities. Conditions for the corrugation instability of the arcade are determined. It is established that the instability growth rate increases with decreases in the longitudinal wavelength and the radial wave number. In the unstable mode, the radial perturbations of the magnetic field are stronger than the longitudinal perturbations, creating an almost circularly corrugated rippling of the arcade in the longitudinal direction. For coronal conditions, the growth time of the instability is shorter than one minute, decreasing with an increase in the temperature. Implications of the developed theory for the dynamics of coronal active regions are discussed.

Hollow-cylinder waveguide isolators for use at millimeter wavelengths

NASA Technical Reports Server (NTRS)

Kanda, M.; May, W. G.

1974-01-01

The device considered in this study is a semiconductor waveguide isolator consisting of a hollow column of a semiconductor mounted coaxially in a circular waveguide in a longitudinal dc magnetic field. An elementary and physical analysis based on the excitation of plane waves in the guide and a more rigorous mode-matching analysis (MMA) are presented. These theoretical predictions are compared with experimental results for an InSb isolator at 94 GHz and 75 K.

Three-dimensional transformation optics for arbitrary coordinate systems: transforming conductive materials and boundaries.

PubMed

Kazemzadeh, Mohammad-Rahim; Alighanbari, Abbas

2018-04-16

A three-dimensional transformation optics method, leading to homogeneous materials, applicable to any non-Cartesian coordinate systems or waveguides/objects of arbitrary cross-sections is presented. Both the conductive boundary and internal material of the desired device is determined by the proposed formulation. The method is applicable to a wide range of waveguide, radiation, and cloaking problems, and is demonstrated for circular waveguide couplers and an external cloak. An advantage of the present method is that the material properties are simplified by appropriately selecting the conductive boundaries. For instance, a right-angle circular waveguide bend is presented which uses only one homogenous material. Also, transformation of conductive materials and boundaries are studied. The conditions in which the transformed boundaries remain conductive are discussed. In addition, it is demonstrated that negative infinite conductivity can be replaced with positive conductivity, without affecting the field outside the conductive boundary. It is also observed that a negative finite conductivity can be replaced with a positive one, by accepting some small errors. The general mathematical procedure and formulation for calculating the parametric surface equations of the conductive peripheries are presented.

Femtosecond laser inscribed cladding waveguides in Nd:YAG ceramics: fabrication, fluorescence imaging and laser performance.

PubMed

Liu, Hongliang; Jia, Yuechen; Vázquez de Aldana, Javier Rodríguez; Jaque, Daniel; Chen, Feng

2012-08-13

We report on the fabrication of depressed cladding waveguide lasers in Nd:YAG (neodymium doped yttrium aluminum garnet, Nd:Y3Al5O12) ceramics microstructured by femtosecond laser pulses. Full control over the confined light spatial distribution is demonstrated by the fabrication of high contrast waveguides with hexagonal, circular and trapezoidal configurations. The confocal fluorescence measurements of the waveguides reveal that the original luminescence features of Nd3+ ions are well-preserved in the waveguide regions. Under optical pump at 808 nm, cladding waveguides showed continuous wave efficient laser oscillation. The maximum output power obtained at 1064.5 nm is ~181 mW with a slope efficiency as high as 44%, which suggests that the fabricated Nd:YAG ceramic waveguides are promising candidates for efficient integrated laser sources.

Low reflectance high power RF load

DOEpatents

Ives, R. Lawrence; Mizuhara, Yosuke M.

2016-02-02

A load for traveling microwave energy has an absorptive volume defined by cylindrical body enclosed by a first end cap and a second end cap. The first end cap has an aperture for the passage of an input waveguide with a rotating part that is coupled to a reflective mirror. The inner surfaces of the absorptive volume consist of a resistive material or are coated with a coating which absorbs a fraction of incident RF energy, and the remainder of the RF energy reflects. The angle of the reflector and end caps is selected such that reflected RF energy dissipates an increasing percentage of the remaining RF energy at each reflection, and the reflected RF energy which returns to the rotating mirror is directed to the back surface of the rotating reflector, and is not coupled to the input waveguide. Additionally, the reflector may have a surface which generates a more uniform power distribution function axially and laterally, to increase the power handling capability of the RF load. The input waveguide may be corrugated for HE11 mode input energy.

Low reflectance radio frequency load

DOEpatents

Ives, R. Lawrence; Mizuhara, Yosuke M

2014-04-01

A load for traveling microwave energy has an absorptive volume defined by cylindrical body enclosed by a first end cap and a second end cap. The first end cap has an aperture for the passage of an input waveguide with a rotating part that is coupled to a reflective mirror. The inner surfaces of the absorptive volume consist of a resistive material or are coated with a coating which absorbs a fraction of incident RF energy, and the remainder of the RF energy reflects. The angle of the reflector and end caps is selected such that reflected RF energy dissipates an increasing percentage of the remaining RF energy at each reflection, and the reflected RF energy which returns to the rotating mirror is directed to the back surface of the rotating reflector, and is not coupled to the input waveguide. Additionally, the reflector may have a surface which generates a more uniform power distribution function axially and laterally, to increase the power handling capability of the RF load. The input waveguide may be corrugated for HE11 mode input energy.

Reversed Cherenkov-transition radiation in a waveguide partly filled with a left-handed medium

NASA Astrophysics Data System (ADS)

Alekhina, Tatiana Yu.; Tyukhtin, Andrey V.

2018-04-01

We analyze the electromagnetic field of a charged particle that moves uniformly in a circular waveguide and crosses a boundary between a vacuum area and an area filled with a left-handed medium exhibiting resonant frequency dispersion. The investigation of the waveguide mode components is performed analytically and numerically. The reversed Cherenkov radiation in the filled area of the waveguide and the reversed Cherenkov-transition radiation (RCTR) in the vacuum area are analyzed. The conditions for the excitation of RCTR are obtained. It is shown that the number of modes of RCTR is always finite; in particular, under certain conditions, the RCTR is composed of the first waveguide mode only. Plots of the typical fields of the excited waveguide mode are presented.

Plate forming and break down pizza box

DOEpatents

Pantisano, Frank; Devine, Scott M.

1992-01-01

A standard corrugated paper pizza box is provided with slit cuts cut through the top panel of the pizza box in a shape to form four circular serving plates with a beveled raised edge and cross slit cuts through the bottom panel of the pizza box separating the box into four essentially equal portions for easy disposal.

UV-LIGA microfabrication process for sub-terahertz waveguides utilizing multiple layered SU-8 photoresist

NASA Astrophysics Data System (ADS)

Malekabadi, Ali; Paoloni, Claudio

2016-09-01

A microfabrication process based on UV LIGA (German acronym of lithography, electroplating and molding) is proposed for the fabrication of relatively high aspect ratio sub-terahertz (100-1000 GHz) metal waveguides, to be used as a slow wave structure in sub-THz vacuum electron devices. The high accuracy and tight tolerances required to properly support frequencies in the sub-THz range can be only achieved by a stable process with full parameter control. The proposed process, based on SU-8 photoresist, has been developed to satisfy high planar surface requirements for metal sub-THz waveguides. It will be demonstrated that, for a given thickness, it is more effective to stack a number of layers of SU-8 with lower thickness rather than using a single thick layer obtained at lower spin rate. The multiple layer approach provides the planarity and the surface quality required for electroforming of ground planes or assembly surfaces and for assuring low ohmic losses of waveguides. A systematic procedure is provided to calculate soft and post-bake times to produce high homogeneity SU-8 multiple layer coating as a mold for very high quality metal waveguides. A double corrugated waveguide designed for 0.3 THz operating frequency, to be used in vacuum electronic devices, was fabricated as test structure. The proposed process based on UV LIGA will enable low cost production of high accuracy sub-THz 3D waveguides. This is fundamental for producing a new generation of affordable sub-THz vacuum electron devices, to fill the technological gap that still prevents a wide diffusion of numerous applications based on THz radiation.

Spiral-path high-sensitivity silicon photonic wire molecular sensor with temperature-independent response.

PubMed

Densmore, A; Xu, D-X; Janz, S; Waldron, P; Mischki, T; Lopinski, G; Delâge, A; Lapointe, J; Cheben, P; Lamontagne, B; Schmid, J H

2008-03-15

We demonstrate a new silicon photonic wire waveguide evanescent field (PWEF) sensor that exploits the strong evanescent field of the transverse magnetic mode of this high-index-contrast, submicrometer-dimension waveguide. High sensitivity is achieved by using a 2 mm long double-spiral waveguide structure that fits within a compact circular area of 150 microm diameter, facilitating compatibility with commercial spotting apparatus and the fabrication of densely spaced sensor arrays. By incorporating the PWEF sensor element into a balanced waveguide Mach-Zehnder interferometer circuit, a minimum detectable mass of approximately 10 fg of streptavidin protein is demonstrated with near temperature-independent response.

Distributed feedback interband cascade lasers with top grating and corrugated sidewalls

DOE Office of Scientific and Technical Information (OSTI.GOV)

Xie, Feng; Stocker, Michael; Pham, John

Distributed feedback (DFB) interband cascade lasers (ICLs) with a 1st order top surface grating were designed and fabricated. Partially corrugated sidewalls were implemented to suppress high order lateral modes. The DFB ICLs have 4 mm long and 4.5 mu m wide ridge waveguides and are mounted epi-up on AlN submounts. We demonstrated a continuous-wave (CW) DFB ICL, from a first wafer which has a large detuning of the gain peak from the DFB wavelength, with a side mode suppression ratio of 30 dB. With proper matching of grating feedback and the gain peak wavelength for the second wafer, a DFBmore » ICL was demonstrated with a maximum CW output power and a maximum wall plug efficiency reaching 42 mW and 2%, respectively, at 25 degrees C. The lasing wavelengths of both lasers are around 3.3 mu m at 25 degrees C. Published by AIP Publishing.« less

Studies of Beam Expansion and Distributed Bragg Reflector Lasers for Fiber Optics and Optical Signal Processing.

DTIC Science & Technology

1981-03-03

described theory and experiments on the DBR laser and on the use of the Distributed Bragg Deflector ( DBD ) to act as a grating bean expander. The DBD is a...and telescope. 9 .\\pplications requiring more power can use the DBD as a power combiner for several laser stripes, as shown in Fig. 3. In design...Bragg deflector ( DBD ). This device consists of a corrugated waveguide, whose grating is slanted at an angle 6 with respect to the incident beam. The

Fin-line horn antenna

DOEpatents

Reindel, John

1990-01-01

A fin line circuit card containing a fin line slot feeds a dipole antenna ich extends a quarterwave outside the waveguide and provides an energy beam focal point at or near the open end of the waveguide. The dipole antenna thus maintains a wide and nearly constant beamwidth, low VSWR and a circular symmetric radiation pattern for use in electronic warfare direction finding and surveillance applications.

Realizable feed-element patterns for multibeam reflector antenna analysis

NASA Technical Reports Server (NTRS)

Rahmat-Samii, Y.; Cramer, P., Jr.; Woo, K.; Lee, S. W.

1981-01-01

The radiation pattern of a feed element is approximately described by a simple function (cos theta) to the q power. For a given element spacing of the feed array, simple formulas for estimating the practical value of q when the element is an open-ended rectangular waveguide, an open-ended circular waveguide, a pyramidal horn, or a cigar antenna are given.

Microwave applicator for in-drum processing of radioactive waste slurry

DOEpatents

White, Terry L.

1994-01-01

A microwave applicator for processing of radioactive waste slurry uses a waveguide network which splits an input microwave of TE.sub.10 rectangular mode to TE.sub.01 circular mode. A cylindrical body has four openings, each receiving 1/4 of the power input. The waveguide network includes a plurality of splitters to effect the 1/4 divisions of power.

Circular-Polarization-Selective Transmission Induced by Spin-Orbit Coupling in a Helical Tape Waveguide

NASA Astrophysics Data System (ADS)

Liu, Yahong; Guo, Qinghua; Liu, Hongchao; Liu, Congcong; Song, Kun; Yang, Biao; Hou, Quanwen; Zhao, Xiaopeng; Zhang, Shuang; Navarro-Cía, Miguel

2018-05-01

Spin-orbit coupling of light, describing the interaction between the polarization (spin) and spatial degrees of freedom (orbit) of light, plays an important role in subwavelength scale systems and leads to many interesting phenomena, such as the spin Hall effect of light. Here, based on the spin-orbit coupling, we design and fabricate a helical tape waveguide (HTW), which can realize a circular-polarization-selective process. When the incident circularly polarized wave is of the same handedness as the helix of the HTW, a nearly complete transmission is observed; in contrast, a counterrotating circular polarization of incident wave results in a much lower transmission or is even totally blocked by the HTW. Indeed, both simulations and experiments reveal that the blocked component of power leaks through the helical aperture of the HTW and forms a conical beam analogous to helical Cherenkov radiation due to the conversion from the spin angular momentum to the orbital angular momentum. Our HTW structure demonstrates its potential as a polarization selector in a broadband frequency range.

Numerical study of remote detection outside the magnet with travelling wave Magnetic Resonance Imaging at 3T

NASA Astrophysics Data System (ADS)

López, M.; Vázquez, F.; Solís-Nájera, S.; Rodriguez, A. O.

2015-01-01

The use of the travelling wave approach for high magnetic field magnetic resonance imaging has been used recently with very promising results. This approach offer images one with greater field-of-view and a reasonable signal-to-noise ratio using a circular waveguide. This scheme has been proved to be successful at 7 T and 9.4 T with whole-body imager. Images have also been acquired with clinical magnetic resonance imaging systems whose resonant frequencies were 64 MHz and 128 MHz. These results motivated the use of remote detection of the magnetic resonance signal using a parallel-plate waveguide together with 3 T clinical scanners, to acquired human leg images. The cut-off frequency of this waveguide is zero for the principal mode, allowing us to overcome the barrier of transmitting waves at lower frequency than 300 MHz or 7 T for protons. These motivated the study of remote detection outside the actual magnet. We performed electromagnetic field simulations of a parallel-plate waveguide and a phantom. The signal transmission was done at 128 MHz and using a circular surface coil located almost 200 cm away for the magnet isocentre. Numerical simulations demonstrated that the magnetic field of the principal mode propagate inside a waveguide outside the magnet. Numerical results were compared with previous experimental-acquired image data under similar conditions.

A tunable optofluidic circular liquid fiber

NASA Astrophysics Data System (ADS)

Li, Lei; Wu, Wei; Shi, Yang; Gong, Enze; Yang, Yi

2016-01-01

This paper presents a tunable optofluidic circular liquid fiber through the numerical simulation. Fiber is a significant optical device and has been widely applied on optical fiber communication. But the fiber based solid has limited tunability. Compared to solid fiber, the fiber based liquid material is relatively infrequent. Cause for the liquid optical device has more freedom tunable properties than solid counterpart, it has attracted more interest. The traditional optofluidic waveguide is designed like a sandwich in planar channel. This two-dimensional (2D) structure liquid waveguide will face huge transmission loss in the perpendicular direction of the flow streams. In this paper, a curving microchannel is designed inside the microchip to produce centrifugal effect. Two different liquids are injected into the chip by external pumps. In a particular situation, the core flow will be totally surrounded by the cladding flow. So the liquid can form an optical waveguide. Its structure is similar to an optical fiber which high refractive index (RI) liquid is core of the waveguide and the low RI liquid is cladding of the waveguide. Profit from the reconfigurability of liquid material, this liquid fiber has excellent tunability. The diameter of the core flow can be tuned in a wider range by changing the volume ratio of the flows through the finite element analysis. It is predictable that such a tunable liquid fiber may find wider applications in lab-on-a-chip systems and integrated optical devices.

Stokes injected Raman capillary waveguide amplifier

DOEpatents

Kurnit, Norman A.

1980-01-01

A device for producing stimulated Raman scattering of CO.sub.2 laser radiation by rotational states in a diatomic molecular gas utilizing a Stokes injection signal. The system utilizes a cryogenically cooled waveguide for extending focal interaction length. The waveguide, in conjunction with the Stokes injection signal, reduces required power density of the CO.sub.2 radiation below the breakdown threshold for the diatomic molecular gas. A Fresnel rhomb is employed to circularly polarize the Stokes injection signal and CO.sub.2 laser radiation in opposite circular directions. The device can be employed either as a regenerative oscillator utilizing optical cavity mirrors or as a single pass amplifier. Additionally, a plurality of Raman gain cells can be staged to increase output power magnitude. Also, in the regenerative oscillator embodiment, the Raman gain cell cavity length and CO.sub.2 cavity length can be matched to provide synchronism between mode locked CO.sub.2 pulses and pulses produced within the Raman gain cell.

Broadbanding of circularly polarized patch antenna by waveguided magneto-dielectric metamaterial

NASA Astrophysics Data System (ADS)

Yang, Xin Mi; Wen, Juan; Liu, Chang Rong; Liu, Xue Guan; Cui, Tie Jun

2015-12-01

Design of bandwidth-enhanced circularly polarized (CP) patch antenna using artificial magneto-dielectric substrate was investigated. The artificial magneto-dielectric material adopted here takes the form of waveguided metamaterial (WG-MTM). In particular, the embedded meander line (EML) structure was employed as the building element of the WG-MTM. As verified by the retrieved effective medium parameters, the EML-based waveguided magneto-dielectric metamaterial (WG-MDM) exhibits two-dimensionally isotropic magneto-dielectric property with respect to TEM wave excitations applied in two orthogonal directions. A CP patch antenna loaded with the EML-based WG-MDM (WG-MDM antenna) has been proposed and its design procedure is described in detail. Simulation results show that the impedance and axial ratio bandwidths of the WG-MDM antenna have increased by 125% and 133%, respectively, compared with those obtained with pure dielectric substrate offering the same patch size. The design of the novel WG-MDM antenna was also validated by measurement results, which show good agreement with their simulated counterparts.

Optical device fabrication using femtosecond laser processing with glass-hologram

NASA Astrophysics Data System (ADS)

Suzuki, Jun'ichi; Arima, Yasunori; Tanaka, Shuhei

2011-03-01

Using femtosecond laser processing with glass-hologram, fabrication of 1cm-long straight waveguide and X-coupler is reported in this paper. We design and fabricate 4-level glass-hologram which generates 1cm-long straight line intensity. We fabricate 1cm-long waveguides inside fused silica at one shot exposure with the glass-hologram. We investigate the waveguide performance of near field pattern and propagation loss at wavelength of 1550nm. The near field pattern is almost circular shape. The propagation loss at 1550nm is estimated to be < 1.0 dB/cm. As an example of an optical device consisting of straight waveguides, we fabricate X-coupler or 2x2 coupler using straight line waveguides, and observe the output power ratio depending on crossing angle.

Demonstration of acoustic waveguiding and tight bending in phononic crystals

DOE PAGES

Ghasemi Baboly, M.; Raza, A.; Brady, J.; ...

2016-10-31

The systematic design, fabrication, and characterization of an isolated, single-mode, 90° bend phononic crystal (PnC) waveguide are presented. A PnC consisting of a 2D square array of circular air holes in an aluminum substrate is used, and waveguides are created by introducing a line defect in the PnC lattice. A high transmission coefficient is observed (–1 dB) for the straight sections of the waveguide, and an overall 2.3 dB transmission loss is observed (a transmission coefficient of 76%) for the 90° bend. Further optimization of the structure may yield higher transmission efficiencies. Lastly, this manuscript shows the complete design processmore » for an engineered 90° bend PnC waveguide from inception to experimental demonstration.« less

Cosmic Microwave Background Polarization Detector with High Efficiency, Broad Bandwidth, and Highly Symmetric Coupling to Transition Edge Sensor Bolometers

NASA Technical Reports Server (NTRS)

Wollack, E.; Cao, N.; Chuss, D.; Denis, K.; Hsieh, W.-T.; Moseley, S. Harvey; Schneider, G.; Stevenson, T.; Travers, D.; U-yen, K.

2008-01-01

Four probe antennas transfer signals from waveguide to microstrip lines. The probes not only provide broadband impedance matching, but also thermally isolate waveguide and detector. In addition, we developed a new photonic waveguide choke joint design, with four-fold symmetry, to suppress power leakage at the interface. We have developed facilities to test superconducting circuit elements using a cryogenic microwave probe station, and more complete systems in waveguide. We used the ring resonator shown below to measure a dielectric loss tangent < 7x10(exp -4) over 10 - 45 GHz. We have combined component simulations to predict the overall coupling from waveguide modes to bolometers. The result below shows the planar circuit and waveguide interface can utilize the high beam symmetry of HE11 circular feedhorns with > 99% coupling efficiency over 30% fractional bandwidth.

Microwave applicator for in-drum processing of radioactive waste slurry

DOEpatents

White, T.L.

1994-06-28

A microwave applicator for processing of radioactive waste slurry uses a waveguide network which splits an input microwave of TE[sub 10] rectangular mode to TE[sub 01] circular mode. A cylindrical body has four openings, each receiving 1/4 of the power input. The waveguide network includes a plurality of splitters to effect the 1/4 divisions of power. 4 figures.

Method And Apparatus For Launching Microwave Energy Into A Plasma Processing Chamber

DOEpatents

DOUGHTY, FRANK C.; [et al

2001-05-01

A method and apparatus for launching microwave energy to a plasma processing chamber in which the required magnetic field is generated by a permanent magnet structure and the permanent magnet material effectively comprises one or more surfaces of the waveguide structure. The waveguide structure functions as an impedance matching device and controls the field pattern of the launched microwave field to create a uniform plasma. The waveguide launcher may comprise a rectangular waveguide, a circular waveguide, or a coaxial waveguide with permanent magnet material forming the sidewalls of the guide and a magnetization pattern which produces the required microwave electron cyclotron resonance magnetic field, a uniform field absorption pattern, and a rapid decay of the fields away from the resonance zone. In addition, the incorporation of permanent magnet material as a portion of the waveguide structure places the magnetic material in close proximity to the vacuum chamber, allowing for a precisely controlled magnetic field configuration, and a reduction of the amount of permanent magnet material required.

Phononic Crystal Waveguide Transducers for Nonlinear Elastic Wave Sensing.

PubMed

Ciampa, Francesco; Mankar, Akash; Marini, Andrea

2017-11-07

Second harmonic generation is one of the most sensitive and reliable nonlinear elastic signatures for micro-damage assessment. However, its detection requires powerful amplification systems generating fictitious harmonics that are difficult to discern from pure nonlinear elastic effects. Current state-of-the-art nonlinear ultrasonic methods still involve impractical solutions such as cumbersome signal calibration processes and substantial modifications of the test component in order to create material-based tunable harmonic filters. Here we propose and demonstrate a valid and sensible alternative strategy involving the development of an ultrasonic phononic crystal waveguide transducer that exhibits both single and multiple frequency stop-bands filtering out fictitious second harmonic frequencies. Remarkably, such a sensing device can be easily fabricated and integrated on the surface of the test structure without altering its mechanical and geometrical properties. The design of the phononic crystal structure is supported by a perturbative theoretical model predicting the frequency band-gaps of periodic plates with sinusoidal corrugation. We find our theoretical findings in excellent agreement with experimental testing revealing that the proposed phononic crystal waveguide transducer successfully attenuates second harmonics caused by the ultrasonic equipment, thus demonstrating its wide range of potential applications for acousto/ultrasonic material damage inspection.

Waveguide Grating For Polarization Preprocessing Circuits

NASA Astrophysics Data System (ADS)

Voirin, Guy; Gradisnik, F.; Parriaux, Olivier M.; Gale, Michael T.; Kunz, Rino E.; Curtis, B. J.; Lehmann, Hans W.

1989-12-01

Periodically corrugated optical waveguides on glass with non-collinear coupling have been investigated both theoretically and experimentally. For a TE or TM polarized guided mode of a planar waveguide obliquely incident on a grating pad, there are four characteristic angles corresponding to the coupling with TE and TM reflected modes fulfilling the Bragg condition. The reflectivity is obtained by solving the coupled mode equations for the non-collinear case. The modelling shows that integrated passive functions such as polarization splitting and interference can be achieved. The polarization interference element uses the property that the coupling coefficients TM-TE and TE-TE are equal at defined incidence angles. Since the angle between the two reflected TE beams is only a few minutes of arc, the two beams can interfere. The waveguides are made by K+ ion exchange in BK7 glass for 3 hours at 380°C. The structure was designed for use at a wavelength of 633 nm and uses a 485 nm period grating which was fabricated by holographic exposure and plasma etching techniques in a 50 nm TiO2 layer e-beam evaporated onto the glass surface. The reflectivity of the grating structure was studied experimentally and compared with theory. The diffraction angles are within 30 " of arc of the predicted angles. The measured reflectivities reached 20 %. The feasibility of realizing an integrated optic preprocessing circuit for polarization interferometry has been demonstrated.

Janus and Huygens Dipoles: Near-Field Directionality Beyond Spin-Momentum Locking.

PubMed

Picardi, Michela F; Zayats, Anatoly V; Rodríguez-Fortuño, Francisco J

2018-03-16

Unidirectional scattering from circularly polarized dipoles has been demonstrated in near-field optics, where the quantum spin-Hall effect of light translates into spin-momentum locking. By considering the whole electromagnetic field, instead of its spin component alone, near-field directionality can be achieved beyond spin-momentum locking. This unveils the existence of the Janus dipole, with side-dependent topologically protected coupling to waveguides, and reveals the near-field directionality of Huygens dipoles, generalizing Kerker's condition. Circular dipoles, together with Huygens and Janus sources, form the complete set of all possible directional dipolar sources in the far- and near-field. This allows the designing of directional emission, scattering, and waveguiding, fundamental for quantum optical technology, integrated nanophotonics, and new metasurface designs.

Janus and Huygens Dipoles: Near-Field Directionality Beyond Spin-Momentum Locking

NASA Astrophysics Data System (ADS)

Picardi, Michela F.; Zayats, Anatoly V.; Rodríguez-Fortuño, Francisco J.

2018-03-01

Unidirectional scattering from circularly polarized dipoles has been demonstrated in near-field optics, where the quantum spin-Hall effect of light translates into spin-momentum locking. By considering the whole electromagnetic field, instead of its spin component alone, near-field directionality can be achieved beyond spin-momentum locking. This unveils the existence of the Janus dipole, with side-dependent topologically protected coupling to waveguides, and reveals the near-field directionality of Huygens dipoles, generalizing Kerker's condition. Circular dipoles, together with Huygens and Janus sources, form the complete set of all possible directional dipolar sources in the far- and near-field. This allows the designing of directional emission, scattering, and waveguiding, fundamental for quantum optical technology, integrated nanophotonics, and new metasurface designs.

Development of an Ultra-Wideband Circularly Polarized Multiple Layer Dielectric Rod Antenna Design

NASA Astrophysics Data System (ADS)

Wainwright, Gregory D.

This dissertations focuses on the development of a novel Ultra-Wideband (UWB) circularly polarized dielectric rod antenna (CPDRA) which yields a constant gain, pattern, and phase center. These properties are important in many applications. Within radar systems a constant phase center is desirable to avoid errors within downrange and crossrange measurements. In a reflector antenna the illumination, spillover, and phase efficiencies will remain the same over an ultra-wideband. Lastly, near field probes require smooth amplitude and phase patterns over frequency to avoid errors during the calibration process of the antenna under test. In this dissertation a novel CP feeding network has been developed for an ultra-wideband dielectric rod antenna. Circularly-polarized antennas have a major advantage over its linearly-polarized counterpart in that the polarization mismatch loss caused by misalignment between the polarizations of the incident fields and antenna can be avoided. This is important in satellite communications and broadcasts where signal propagation through the ionosphere can experience Faraday Rotation. A circularly polarized antenna is also helpful in mobile radar and communication systems where the receiving antennas orientation is not fixed. Previous research on UWB dielectric rod antenna designs has focused on Dual linear feeds. Each polarization within the dual linear feed is excited by a pair of linear launcher arms fed with a 0°-180° hybrid balun. The proposed CPDRA design does not require the 0°-180° hybrid baluns or 0°-90° hybrid for achieving CP operation. These hybrids will increase the antennas size, weight, cost, and reduce operational bandwidth. A design technique has been developed for an UWB multilayer dielectric waveguide used in a CPDRA antenna. This design technique uses near-field Electric field data from inside the waveguide, in conjunction with a genetic algorithm optimization to yield a wideband waveguide with a near field amplitude distribution that scales with frequency. A multilayered dielectric waveguide presents many fabrication challenges. The thermal expansion rates, moisture absorption rates, and vibration properties differ within the various dielectric materials used. Therefore, the development of a wideband waveguide using one material with a low dielectric constant would be advantages since 3-D printing technology can be utilized. In this dissertation novel TE01 and TM01 mode suppressors have been developed using only a single dielectric material.

Advanced Antennas Enabled by Electromagnetic Metamaterials

DTIC Science & Technology

2014-12-01

radiation patterns of a conical horn antenna and three soft horns with various homogeneous metasurface liners. The maximum cross-polarization level was...inhomogencous metasurface liners covering both the flared horn section and the straight waveguide section. The mctahorn is fed by a circular waveguide...with a diameter of 20 mm. (b) The sizes of the metallic patches at each row of the metasurface in the flared horn section. Both the length and width

Mid-Infrared Photonic Devices Fabricated by Ultrafast Laser Inscription

DTIC Science & Technology

2016-07-01

active and passive photonic devices in single crystal, ceramic and glass substrates. This range of devices span applications such as: astrophysics [16...waveguide has been published this year in Applied Physics Letters. Reference: Macdonald, J.R., et al., Compact mid-infrared Cr:ZnSe channel...waveguide laser. Applied Physics Letters, 2013. 102(16): p. 161110. High efficiency circular cladding WG laser The initial demonstration of square double

Investigation of Truncated Waveguides

NASA Technical Reports Server (NTRS)

Lourie, Nathan P.; Chuss, David T.; Henry, Ross M.; Wollack, Edward J.

2013-01-01

The design, fabrication, and performance of truncated circular and square waveguide cross-sections are presented. An emphasis is placed upon numerical and experimental validation of simple analytical formulae that describe the propagation properties of these structures. A test component, a 90-degree phase shifter, was fabricated and tested at 30 GHz. The concepts explored can be directly applied in the design, synthesis and optimization of components in the microwave to sub-millimeter wavebands.

Temporal profile measurements of relativistic electron bunch based on wakefield generation

DOE PAGES

Bettoni, S.; Craievich, P.; Lutman, A. A.; ...

2016-02-25

A complete characterization of the time-resolved longitudinal beam phase space is important to optimize the final performances of an accelerator, and in particular this is crucial for Free Electron Laser (FEL) facilities. In this study we propose a novel method to characterize the profile of a relativistic electron bunch by passively streaking the beam using its self-interaction with the transverse wakefield excited by the bunch itself passing off-axis through a dielectric-lined or a corrugated waveguide. Results of a proof-of-principle experiment at the SwissFEL Injector Test Facility are discussed.

Thin-walled composite tubes using fillers subjected to quasistatic axial compression

NASA Astrophysics Data System (ADS)

AL-Qrimli, Haidar F.; Mahdi, Fadhil A.; Ismail, Firas B.; Alzorqi, Ibrahim S.

2015-04-01

It has been demonstrated that composites are lightweight, fatigue resistant and easily melded, a seemingly attractive alternative to metals. However, there has been no widespread switch from metals to composites in the automotive sector. This is because there are a number of technical issues relating to the use of composite materials that still need to be resolved including accurate material characterization, manufacturing and joining process. The total of 36 specimens have been fabricated using the fibre-glass and resin (epoxy) with a two different geometries (circular and corrugated) each one will be filled with five types of filler (Rice Husk, Wood Chips, Aluminium Chips, Coconut Fibre, Palm Oil Fibre) all these type will be compared with empty Tubes for circular and corrugated in order to comprehend the crashworthiness parameters (initial failure load, average load, maximum crushing load, load ratio, energy absorption, specific energy absorption, volumetric energy absorption, crushing force efficiency and crush strain relation) which are considered very sufficient parameters in the design of automotive industry parts. All the tests have been done using the “INSTRON Universal machine” which is computerized in order to simply give a high precision to the collection of the results, along with the use of quasi-static load to test and observe the behaviour of the fabricated specimens.

Multi-mode horn antenna simulation

NASA Technical Reports Server (NTRS)

Dod, L. R.; Wolf, J. D.

1980-01-01

Radiation patterns were computed for a circular multimode horn antenna using waveguide electric field radiation expressions. The circular multimode horn was considered as a possible reflector feed antenna for the Large Antenna Multifrequency Microwave Radiometer (LAMMR). This horn antenna uses a summation of the TE sub 11 deg and TM sub 11 deg modes to generate far field primary radiation patterns with equal E and H plane beamwidths and low sidelobes. A computer program for the radiation field expressions using the summation of waveguide radiation modes is described. The sensitivity of the multimode horn antenna radiation patterns to phase variations between the two modes is given. Sample radiation pattern calculations for a reflector feed horn for LAMMR are shown. The multimode horn antenna provides a low noise feed suitable for radiometric applications.

Dual-polarization 8.45 GHz traveling-wave maser

NASA Technical Reports Server (NTRS)

Quinn, R. B.

1987-01-01

An 8.5 GHz dual-channel, dual-polarization traveling-wave maser (TWM) amplifier was installed in the XKR solar system radar cone at DSS 14. The TWM is based on the Blk IIA 8.45 GHz maser structure, with two of the four maser stages being used for each channel, and each maser half then followed by a high-performance GaAs FET amplifier to achieve the desired net gain. A shortened low-noise input waveguide and an orthogonal-mode junction which is cooled to 4.5 K feeds each amplifier chain. The rotation of an external polarizer permits the polarization of each channel to be defined as either linear or circular. A circular waveguide switch was also developed to provide for noise calibration and to protect the maser from incident transmitter power.

Characteristics of phase-correcting fresnel zone plates and elliptical waveguides

NASA Astrophysics Data System (ADS)

Wiltse, James C.

1994-02-01

The primary area of activity has been concentrated on the investigations relating to Fresnel zone plate antennas. A secondary effort has dealt with the characteristics of propagation in waveguides of elliptical cross section. In both cases, applications at microwave and millimeter-wavelengths have been emphasized. Thorough literature searches were conducted, and the results are given in Appendices A and B. The zone plate work has dealt with both transmission and reflection types, and has included considering the off-axis-fed cases. In the latter case, the plate may consist of elliptical zones, rather than the usual circular configuration. In general, the characteristics studied include far-field patterns, focal region fields, off-axis performance, bandwidth, and aberrations. In the case of propagation in elliptical waveguides, the attenuation and modal properties were studied for enclosed metal waveguides, coaxial transmission lines, and various surface waveguides.

Final Report Advanced Quasioptical Launcher System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jeffrey Neilson

2010-04-30

This program developed an analytical design tool for designing antenna and mirror systems to convert whispering gallery RF modes to Gaussian or HE11 modes. Whispering gallery modes are generated by gyrotrons used for electron cyclotron heating of fusion plasmas in tokamaks. These modes cannot be easily transmitted and must be converted to free space or waveguide modes compatible with transmission line systems.This program improved the capability of SURF3D/LOT, which was initially developed in a previous SBIR program. This suite of codes revolutionized quasi-optical launcher design, and this code, or equivalent codes, are now used worldwide. This program added functionality tomore » SURF3D/LOT to allow creating of more compact launcher and mirror systems and provide direct coupling to corrugated waveguide within the vacuum envelope of the gyrotron. Analysis was also extended to include full-wave analysis of mirror transmission line systems. The code includes a graphical user interface and is available for advanced design of launcher systems.« less

Femtosecond-laser inscribed double-cladding waveguides in Nd:YAG crystal: a promising prototype for integrated lasers.

PubMed

Liu, Hongliang; Chen, Feng; Vázquez de Aldana, Javier R; Jaque, D

2013-09-01

We report on the design and implementation of a prototype of optical waveguides fabricated in Nd:YAG crystals by using femtosecond-laser irradiation. In this prototype, two concentric tubular structures with nearly circular cross sections of different diameters have been inscribed in the Nd:YAG crystals, generating double-cladding waveguides. Under 808 nm optical pumping, waveguide lasers have been realized in the double-cladding structures. Compared with single-cladding waveguides, the concentric tubular structures, benefiting from the large pump area of the outermost cladding, possess both superior laser performance and nearly single-mode beam profile in the inner cladding. Double-cladding waveguides of the same size were fabricated and coated by a thin optical film, and a maximum output power of 384 mW and a slope efficiency of 46.1% were obtained. Since the large diameters of the outer claddings are comparable with those of the optical fibers, this prototype paves a way to construct an integrated single-mode laser system with a direct fiber-waveguide configuration.

The Electron Bernstein Waves Heating Project In The TJ-II Stellarator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fernandez, A.; Cappa, A.; Castejon, F.

2007-09-28

TJ-II is a middle sized flexible Heliac operating in Madrid, whose plasmas are created and heated by ECRH via two 300 kW gyrotrons at second harmonic X-mode (53.2 GHz). Neutral beam injection is used for second phase heating. Since the cut off density for the 2nd harmonic X-mode (n{sub c} = 1.7x10 {sup 19} m{sup -3}) is reached during NBI, EBWs are considered both for providing additional heating after NBI switch on and to perform kinetic studies in high-density plasmas. Previous work has shown that the most suitable scheme for launching EBWs in TJ-II is O-X-B mode conversion, which hasmore » acceptable heating efficiency for central densities above 1.2x10{sup 19} m{sup -3}, with an operating frequency of 28 GHz. In this work, the most relevant theoretical calculations are presented, including the relativistic effects both in ray trajectory and absorption, as well as the results of the optimization of the beam parameters that provide the maximum O-X conversion efficiency at the critical layer. A system based on a 28 GHz-100 ms diode gyrotron will be used to deliver 300 kW through a corrugated waveguide. The microwave beam is directed and focused by a steerable mirror located inside the vacuum vessel. A diagnostic for measuring the EBW emission has been designed and tested on the bench. It uses a section of corrugated waveguide and a glass lens to focus the emission from the plasma into the aperture of a dual polarized quad-ridged horn. It will allow us to determine the EBW mode conversion efficiency, and also provides an indication of the electron temperature evolution in overdense plasmas.« less

Propagation of Electromagnetic Waves in Slab Waveguide Structure Consisting of Chiral Nihility Claddings and Negative-Index Material Core Layer

NASA Astrophysics Data System (ADS)

Helal, Alaa N. Abu; Taya, Sofyan A.; Elwasife, Khitam Y.

2018-06-01

The dispersion equation of an asymmetric three-layer slab waveguide, in which all layers are chiral materials is presented. Then, the dispersion equation of a symmetric slab waveguide, in which the claddings are chiral materials and the core layer is negative index material, is derived. Normalized cut-off frequencies, field profile, and energies flow of right-handed and left-handed circularly polarized modes are derived and plotted. We consider both odd and even guided modes. Numerical results of guided low-order modes are provided. Some novel features, such as abnormal dispersion curves, are found.

Towards an integrated AlGaAs waveguide platform for phase and polarisation shaping

NASA Astrophysics Data System (ADS)

Maltese, G.; Halioua, Y.; Lemaître, A.; Gomez-Carbonell, C.; Karimi, E.; Banzer, P.; Ducci, S.

2018-05-01

We propose, design and fabricate an on-chip AlGaAs waveguide capable of generating a controlled phase delay of π/2 between the guided transverse electric and magnetic modes. These modes possess significantly strong longitudinal field components as a direct consequence of their strong lateral confinement in the waveguide. We demonstrate that the effect of the device on a linearly polarised input beam is the generation of a field, which is circularly polarised in its transverse components and carries a phase vortex in its longitudinal component. We believe that the discussed integrated platform enables the generation of light beams with tailored phase and polarisation distributions.

Wave attenuation and mode dispersion in a waveguide coated with lossy dielectric material

NASA Technical Reports Server (NTRS)

Lee, C. S.; Chuang, S. L.; Lee, S. W.; Lo, Y. T.

1984-01-01

The modal attenuation constants in a cylindrical waveguide coated with a lossy dielectric material are studied as functions of frequency, dielectric constant, and thickness of the dielectric layer. A dielectric material best suited for a large attenuation is suggested. Using Kirchhoff's approximation, the field attenuation in a coated waveguide which is illuminated by a normally incident plane wave is also studied. For a circular guide which has a diameter of two wavelengths and is coated with a thin lossy dielectric layer (omega sub r = 9.1 - j2.3, thickness = 3% of the radius), a 3 dB attenuation is achieved within 16 diameters.

Large tuning of birefringence in two strip silicon waveguides via optomechanical motion.

PubMed

Ma, Jing; Povinelli, Michelle L

2009-09-28

We present an optomechanical method to tune phase and group birefringence in parallel silicon strip waveguides. We first calculate the deformation of suspended, parallel strip waveguides due to optical forces. We optimize the frequency and polarization of the pump light to obtain a 9 nm deformation for an optical power of 20 mW. Widely tunable phase and group birefringence can be achieved by varying the pump power, with maximum values of 0.026 and 0.13, respectively. The giant phase birefringence allows linear to circular polarization conversion within 30 microm for a pump power of 67 mW. The group birefringence gives a tunable differential group delay of 6fs between orthogonal polarizations. We also evaluate the tuning performance of waveguides with different cross sections.

CWG - MUTUAL COUPLING PROGRAM FOR CIRCULAR WAVEGUIDE-FED APERTURE ARRAY (IBM PC VERSION)

NASA Technical Reports Server (NTRS)

Bailey, M. C.

1994-01-01

Mutual Coupling Program for Circular Waveguide-fed Aperture Array (CWG) was developed to calculate the electromagnetic interaction between elements of an antenna array of circular apertures with specified aperture field distributions. The field distributions were assumed to be a superposition of the modes which could exist in a circular waveguide. Various external media were included to provide flexibility of use, for example, the flexibility to determine the effects of dielectric covers (i.e., thermal protection system tiles) upon the impedance of aperture type antennas. The impedance and radiation characteristics of planar array antennas depend upon the mutual interaction between all the elements of the array. These interactions are influenced by several parameters (e.g., the array grid geometry, the geometry and excitation of each array element, the medium outside the array, and the internal network feeding the array.) For the class of array antenna whose radiating elements consist of small holes in a flat conducting plate, the electromagnetic problem can be divided into two parts, the internal and the external. In solving the external problem for an array of circular apertures, CWG will compute the mutual interaction between various combinations of circular modal distributions and apertures. CWG computes the mutual coupling between various modes assumed to exist in circular apertures that are located in a flat conducting plane of infinite dimensions. The apertures can radiate into free space, a homogeneous medium, a multilayered region or a reflecting surface. These apertures are assumed to be excited by one or more modes corresponding to the modal distributions in circular waveguides of the same cross sections as the apertures. The apertures may be of different sizes and also of different polarizations. However, the program assumes that each aperture field contains the same modal distributions, and calculates the complex scattering matrix between all mode and aperture combinations. The scattering matrix can then be used to determine the complex modal field amplitudes for each aperture with a specified array excitation. CWG is written in VAX FORTRAN for DEC VAX series computers running VMS (LAR-15236) and IBM PC series and compatible computers running MS-DOS (LAR-15226). It requires 360K of RAM for execution. To compile the source code for the PC version, the NDP Fortran compiler and linker will be required; however, the distribution medium for the PC version of CWG includes a sample MS-DOS executable which was created using NDP Fortran with the -vms compiler option. The standard distribution medium for the PC version of CWG is a 3.5 inch 1.44Mb MS-DOS format diskette. The standard distribution medium for the VAX version of CWG is a 1600 BPI 9track magnetic tape in DEC VAX BACKUP format. The VAX version is also available on a TK50 tape cartridge in DEC VAX BACKUP format. Both machine versions of CWG include an electronic version of the documentation in Microsoft Word for Windows format. CWG was developed in 1993 and is a copyrighted work with all copyright vested in NASA.

CWG - MUTUAL COUPLING PROGRAM FOR CIRCULAR WAVEGUIDE-FED APERTURE ARRAY (VAX VMS VERSION)

NASA Technical Reports Server (NTRS)

Bailey, M. C.

1994-01-01

Mutual Coupling Program for Circular Waveguide-fed Aperture Array (CWG) was developed to calculate the electromagnetic interaction between elements of an antenna array of circular apertures with specified aperture field distributions. The field distributions were assumed to be a superposition of the modes which could exist in a circular waveguide. Various external media were included to provide flexibility of use, for example, the flexibility to determine the effects of dielectric covers (i.e., thermal protection system tiles) upon the impedance of aperture type antennas. The impedance and radiation characteristics of planar array antennas depend upon the mutual interaction between all the elements of the array. These interactions are influenced by several parameters (e.g., the array grid geometry, the geometry and excitation of each array element, the medium outside the array, and the internal network feeding the array.) For the class of array antenna whose radiating elements consist of small holes in a flat conducting plate, the electromagnetic problem can be divided into two parts, the internal and the external. In solving the external problem for an array of circular apertures, CWG will compute the mutual interaction between various combinations of circular modal distributions and apertures. CWG computes the mutual coupling between various modes assumed to exist in circular apertures that are located in a flat conducting plane of infinite dimensions. The apertures can radiate into free space, a homogeneous medium, a multilayered region or a reflecting surface. These apertures are assumed to be excited by one or more modes corresponding to the modal distributions in circular waveguides of the same cross sections as the apertures. The apertures may be of different sizes and also of different polarizations. However, the program assumes that each aperture field contains the same modal distributions, and calculates the complex scattering matrix between all mode and aperture combinations. The scattering matrix can then be used to determine the complex modal field amplitudes for each aperture with a specified array excitation. CWG is written in VAX FORTRAN for DEC VAX series computers running VMS (LAR-15236) and IBM PC series and compatible computers running MS-DOS (LAR-15226). It requires 360K of RAM for execution. To compile the source code for the PC version, the NDP Fortran compiler and linker will be required; however, the distribution medium for the PC version of CWG includes a sample MS-DOS executable which was created using NDP Fortran with the -vms compiler option. The standard distribution medium for the PC version of CWG is a 3.5 inch 1.44Mb MS-DOS format diskette. The standard distribution medium for the VAX version of CWG is a 1600 BPI 9track magnetic tape in DEC VAX BACKUP format. The VAX version is also available on a TK50 tape cartridge in DEC VAX BACKUP format. Both machine versions of CWG include an electronic version of the documentation in Microsoft Word for Windows format. CWG was developed in 1993 and is a copyrighted work with all copyright vested in NASA.

Evaporated As2S3 Luneburg lenses for LiNbO3:Ti optical waveguides

NASA Technical Reports Server (NTRS)

Busch, J. R.; Wood, V. E.; Kenan, R. P.; Verber, C. M.

1981-01-01

Luneburg lenses of good quality were formed on high index optical waveguides by evaporation of arsenic trisulfide glass through simple masks. Using only two thin circular aperture masks, lenses with focal spots of a few times the diffraction limited width at f/4 were obtained. These lenses were designed for and tested at both visible (633 nm) and infrared wavelengths. Procedures for the design, fabrication, and testing of lenses of this type are described.

Dielectric millimeter waveguides. Volume 1

NASA Astrophysics Data System (ADS)

Yeh, Cavour

1988-03-01

This report summarizes the result of the research carried out for the Postdoctoral Task E-6-7108 administered by the University of Dayton under contract F30602-81-C-0206 with RADC. The primary objectives of this research program were to learn whether there exists a dielectric waveguide configuration which offers a lower loss figure than a circular dielectric rod and to establish an experimental technique to measure the guiding characteristics of waves on dielectric structures. These objectives were met. Future research areas are also described in this report.

Bunch radiation from a semi-infinite waveguide with dielectric filling inside a waveguide with larger radius

NASA Astrophysics Data System (ADS)

Galyamin, S. N.; Tyukhtin, A. V.; Vorobev, V. V.; Aryshev, A.

2018-02-01

We consider a point charge and Gaussian bunch of charged particles moving along the axis of a circular perfectly conducting pipe with uniform dielectric filling and open end. It is supposed that this semi-infinite waveguide is located in collinear infinite vacuum pipe with perfectly conducting walls and larger diameter. We deal with two cases corresponding to the open end of the inner waveguide with and without flange. Radiation produced by a charge or bunch flying from dielectric part to wide vacuum part is analyzed. We use modified residue-calculus technique and construct rigorous analytical theory describing scattered field in each sub-area of the structure. Cherenkov radiation generated in the dielectric waveguide and penetrating into the vacuum regions of the structure is of main interest throughout the present paper. We show that this part of radiation can be easily analyzed using the presented formalism. We also perform numerical simulation in CST PS code and verify the analytical results.

Concentric Circular Grating Generated by the Patterning Trapping of Nanoparticles in an Optofluidic Chip

PubMed Central

Dai, Hailang; Cao, Zhuangqi; Wang, Yuxing; Li, Honggen; Sang, Minghuang; Yuan, Wen; Chen, Fan; Chen, Xianfeng

2016-01-01

Due to the field enhancement effect of the hollow-core metal-cladded optical waveguide chip, massive nanoparticles in a solvent are effectively trapped via exciting ultrahigh order modes. A concentric ring structure of the trapped nanoparticles is obtained since the excited modes are omnidirectional at small incident angle. During the process of solvent evaporation, the nanoparticles remain well trapped since the excitation condition of the optical modes is still valid, and a concentric circular grating consisting of deposited nanoparticles can be produced by this approach. Experiments via scanning electron microscopy, atomic force microscopy and diffraction of a probe laser confirmed the above hypothesis. This technique provides an alternative strategy to enable effective trapping of dielectric particles with low-intensity nonfocused illumination, and a better understanding of the correlation between the guided modes in an optical waveguide and the nanoparticles in a solvent. PMID:27550743

High-order modes of spoof surface plasmonic wave transmission on thin metal film structure.

PubMed

Liu, Xiaoyong; Feng, Yijun; Zhu, Bo; Zhao, Junming; Jiang, Tian

2013-12-16

Recently, conformal surface plasmon (CSP) structure has been successfully proposed that could support spoof surface plasmon polaritons (SPPs) on corrugated metallic strip with ultrathin thickness [Proc. Natl. Acad. Sci. U.S.A. 110, 40-45 (2013)]. Such concept provides a flexible, conformal, and ultrathin wave-guiding element, very promising for application of plasmonic devices, and circuits in the frequency ranging from microwave to mid-infrared. In this work, we investigated the dispersions and field patterns of high-order modes of spoof SPPs along CSP structure of thin metal film with corrugated edge of periodic array of grooves, and carried out direct measurement on the transmission spectrum of multi-band of surface wave propagation at microwave frequency. It is found that the mode number and mode bands are mainly determined by the depth of the grooves, providing a way to control the multi-band transmission spectrum. We have also experimentally verified the high-order mode spoof SPPs propagation on curved CSP structure with acceptable bending loss. The multi-band propagation of spoof surface wave is believed to be applicable for further design of novel planar devices such as filters, resonators, and couplers, and the concept can be extended to terahertz frequency range.

Grating-coupled surface plasmons on InSb: a versatile platform for terahertz plasmonic sensing (Conference Presentation)

NASA Astrophysics Data System (ADS)

Talbayev, Diyar; Zhou, Jiangfeng; Lin, Shuai; Bhattarai, Khagendra

2017-05-01

Detection and identification of molecular materials based on their THz frequency vibrational resonances remains an open technological challenge. The need for such technology is illustrated by its potential uses in explosives detection (e.g., RDX) or identification of large biomolecules based on their THz-frequency vibrational fingerprints. The prevailing approaches to THz sensing often rely on a form of waveguide spectroscopy, either utilizing geometric waveguides, such as metallic parallel plate, or plasmonic waveguides made of structured metallic surfaces with sub-wavelength corrugation. The sensitivity of waveguide-based sensing devices is derived from the long (1 cm or longer) propagation and interaction distance of the THz wave with the analyte. We have demonstrated that thin InSb layers with metallic gratings can support high quality factor "true" surface plasmon (SP) resonances that can be used for THz plasmonic sensing. We find two strong SP absorption resonances in normal-incidence transmission and investigate their dispersion relations, dependence on InSb thickness, and the spatial distribution of the electric field. The sensitivity of this approach relies on the frequency shift of the SP resonance when the dielectric function changes in the immediate vicinity of the sensor, in the region of deeply sub-wavelength thickness. Our computational modeling indicates that the sensor sensitivity can exceed 0.25 THz per refractive index unit. One of the SP resonances also exhibits a splitting when tuned in resonance with a vibrational mode of an analyte, which could lead to new sensing modalities for the detection of THz vibrational features of the analyte.

Pseudo-One-Dimensional Magnonic Crystals for High-Frequency Nanoscale Devices

NASA Astrophysics Data System (ADS)

Banerjee, Chandrima; Choudhury, Samiran; Sinha, Jaivardhan; Barman, Anjan

2017-07-01

The synthetic magnonic crystals (i.e., periodic composites consisting of different magnetic materials) form one fascinating class of emerging research field, which aims to command the process and flow of information by means of spin waves, such as in magnonic waveguides. One of the intriguing features of magnonic crystals is the presence and tunability of band gaps in the spin-wave spectrum, where the high attenuation of the frequency bands can be utilized for frequency-dependent control on the spin waves. However, to find a feasible way of band tuning in terms of a realistic integrated device is still a challenge. Here, we introduce an array of asymmetric saw-tooth-shaped width-modulated nanoscale ferromagnetic waveguides forming a pseudo-one-dimensional magnonic crystal. The frequency dispersion of collective modes measured by the Brillouin light-scattering technique is compared with the band diagram obtained by numerically solving the eigenvalue problem derived from the linearized Landau-Lifshitz magnetic torque equation. We find that the magnonic band-gap width, position, and the slope of dispersion curves are controllable by changing the angle between the spin-wave propagation channel and the magnetic field. The calculated profiles of the dynamic magnetization reveal that the corrugation at the lateral boundary of the waveguide effectively engineers the edge modes, which forms the basis of the interactive control in magnonic circuits. The results represent a prospective direction towards managing the internal field distribution as well as the dispersion properties, which find potential applications in dynamic spin-wave filters and magnonic waveguides in the gigahertz frequency range.

Waveguide-Mode Terahertz Free Electron Lasers Driven by Magnetron-Based Microtrons

NASA Astrophysics Data System (ADS)

Jeong, Young Uk; Miginsky, Sergey; Gudkov, Boris; Lee, Kitae; Mun, Jungho; Shim, Gyu Il; Bae, Sangyoon; Kim, Hyun Woo; Jang, Kyu-Ha; Park, Sunjeong; Park, Seong Hee; Vinokurov, Nikolay

2016-04-01

We have developed small-sized terahertz free-electron lasers by using low-cost and compact microtrons combining with magnetrons as high-power RF sources. We could stabilize the bunch repetition rate by optimizing a modulator for the magnetron and by coupling the magnetron with an accelerating cavity in the microtron. By developing high-performance undulators and low-loss waveguide-mode resonators having small cross-sectional areas, we could strengthen the interaction between the electron beam and the THz wave inside the FEL resonators to achieve lasing even with low-current electron beams from the microtron. We used a parallel-plate waveguide in a planar electromagnet undulator for our first THz FEL. We try to reduce the size of the FEL resonator by combining a dielectric-coated circular waveguide and a variable-period helical undulator to realize a table-top THz FEL for applying it to the security inspection on airports.

Efficient laser emission from cladding waveguide inscribed in Nd:GdVO(4) crystal by direct femtosecond laser writing.

PubMed

Liu, Hongliang; Tan, Yang; Vázquez de Aldana, Javier R; Chen, Feng

2014-08-01

We report on the fabrication of depressed cladding waveguides in Nd:GdVO(4) laser crystal by using femtosecond laser inscription. The cross section of the structure is a circular shape with a diameter of 150 μm. Under the optical pump at 808 nm, the continuous wave (cw) as well as pulsed (Q-switched by graphene saturable absorber) waveguide lasing at 1064 nm has been realized, supporting guidance of both TE and TM polarizations. The maximum output power of 0.57 W was obtained in the cw regime, while the maximum pulse energy of the pulsed laser emissions was up to 19 nJ (corresponding to a maximum average output power of 0.33 W, at a resonant frequency of 18 MHz). The slope efficiencies achieved for the cw and pulsed Nd:GdVO(4) waveguide lasers were as high as 68% and 52%, respectively.

Homogenizing microwave illumination in thermoacoustic tomography by a linear-to-circular polarizer based on frequency selective surfaces

NASA Astrophysics Data System (ADS)

He, Yu; Shen, Yuecheng; Feng, Xiaohua; Liu, Changjun; Wang, Lihong V.

2017-08-01

A circularly polarized antenna, providing more homogeneous illumination compared to a linearly polarized antenna, is more suitable for microwave induced thermoacoustic tomography (TAT). The conventional realization of a circular polarization is by using a helical antenna, but it suffers from low efficiency, low power capacity, and limited aperture in TAT systems. Here, we report an implementation of a circularly polarized illumination method in TAT by inserting a single-layer linear-to-circular polarizer based on frequency selective surfaces between a pyramidal horn antenna and an imaging object. The performance of the proposed method was validated by both simulations and experimental imaging of a breast tumor phantom. The results showed that a circular polarization was achieved, and the resultant thermoacoustic signal-to-noise was twice greater than that in the helical antenna case. The proposed method is more desirable in a waveguide-based TAT system than the conventional method.

SiN-assisted polarization-insensitive multicore fiber to silicon photonics interface

NASA Astrophysics Data System (ADS)

Poulopoulos, Giannis N.; Kalavrouziotis, Dimitrios; Mitchell, Paul; Macdonald, John R.; Bakopoulos, Paraskevas; Avramopoulos, Hercules

2015-06-01

We demonstrate a polarization-insensitive coupler interfacing multicore-fiber (MCF) to silicon waveguides. It comprises a 3D glass fanout transforming the circular MCF core-arrangement to linear and performing initial tapering, followed by a Spot-Size-Converter on the silicon chip. Glass waveguides are formed of multiple overlapped modification elements and appropriate offsetting thereof yields tapers with symmetric cross-section. The Spot-Size-Converter is an inverselytapered silicon waveguide with a tapered polymer overcladding where light is initially coupled, whereas phase-matching gradually shifts it towards the silicon core. Co-design of the glass fanout and Spot-Size-Converter obtains theoretical loss below 1dB for the overall Si-to-MCF transition in both polarizations.

Development of a wavelength tunable filter using MEMS technology

NASA Astrophysics Data System (ADS)

Liu, Junting

Microelectromechanical systems (MEMS) for optical applications have received intensive attention in recent years because of their potential applications in optical telecommunication. Traditional wavelength division multiplexing (WDM) offers high capacity but requires the fabrication of selective add-drop filters. MEMS technology offers an effective way to fabricate these components at low cost. This thesis presents the development of a device that tunes the Bragg wavelength by coupling into the evanescent field of the grating. A Bragg grating is a periodic perturbation of the refractive index along a fiber or a periodic perturbation of the structure of a planar waveguide. The Bragg wavelength can be tuned by changing the degree to which a dielectric slab couples into the evanescent field. The result is a change in the effective index of the grating, and thus a change in the wavelength that which it reflects. In this thesis Bragg gratings were successfully written into an optical fiber using phase mask technique. Mechanical polishing was used to side-polish the fiber and remove cladding to expose the core. Grating structures were also fabricated in planar waveguide using E-beam writing and dry etching. In order to achieve the smoothest possible morphology of the waveguide, plasma dry etching of transparent substrates was studied in great detail. It is found that the pre-etch cleaning procedure greatly influences the ability to obtain a smooth etched surface. Upper limits of evanescent field tuning were investigated by applying different index liquids such as D. I. water and index matching oils or by positioning different dielectric materials such as glass and silicon close to the grating. Planar waveguides were found to be more sensitive to effective index change. Two kinds of computer simulation were carried out to understand the mode profile and to estimate the value of effective index of planar waveguide under "dry" and "wet" conditions. The first one used an average depth of grating approximation. The second explicitly considered the corrugated structure of the waveguide. Results of both simulations were compared with the experimental results in order to find the proper simulation approach. The fiber or planar waveguide gratings were "device" integrated and their pro and cons were compared. Devices using an optical fiber employed a microactuator driven by electrothermal vibromotor to change the degree of coupling between fiber and "tuning block". Device using planar waveguides used an electrostatic force actuated membrane, flip-chip mounted atop the waveguide. All devices were fabricated using polysilicon surface micromachining processes. I concluded that devices driven by electrostatic force were easier to actuate and their integration with waveguide less challenging.

High-Power Rf Load

DOEpatents

Tantawi, Sami G.; Vlieks, Arnold E.

1998-09-01

A compact high-power RF load comprises a series of very low Q resonators, or chokes [16], in a circular waveguide [10]. The sequence of chokes absorb the RF power gradually in a short distance while keeping the bandwidth relatively wide. A polarizer [12] at the input end of the load is provided to convert incoming TE.sub.10 mode signals to circularly polarized TE.sub.11 mode signals. Because the load operates in the circularly polarized mode, the energy is uniformly and efficiently absorbed and the load is more compact than a rectangular load. Using these techniques, a load having a bandwidth of 500 MHz can be produced with an average power dissipation level of 1.5 kW at X-band, and a peak power dissipation of 100 MW. The load can be made from common lossy materials, such as stainless steel, and is less than 15 cm in length. These techniques can also produce loads for use as an alternative to ordinary waveguide loads in small and medium RF accelerators, in radar systems, and in other microwave applications. The design is easily scalable to other RF frequencies and adaptable to the use of other lossy materials.

Flying radio frequency undulator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kuzikov, S. V.; Vikharev, A. A.; Savilov, A. V.

2014-07-21

A concept for the room-temperature rf undulator, designed to produce coherent X-ray radiation by means of a relatively low-energy electron beam and pulsed mm-wavelength radiation, is proposed. The “flying” undulator is a high-power short rf pulse co-propagating together with a relativistic electron bunch in a helically corrugated waveguide. The electrons wiggle in the rf field of the −1st spatial harmonic with the phase velocity directed in the opposite direction in respect to the bunch velocity, so that particles can irradiate high-frequency Compton's photons. A high group velocity (close to the speed of light) ensures long cooperative motion of the particlesmore » and the co-propagating rf pulse.« less

Electro-optical tunable waveguide embedded multiscan Bragg gratings in lithium niobate by direct femtosecond laser writing.

PubMed

Kroesen, Sebastian; Horn, Wolfgang; Imbrock, Jörg; Denz, Cornelia

2014-09-22

optical tunable Bragg gratings in lithium niobate fabricated by direct femtosecond laser writing. The hybrid design that consists of a circular type-II waveguide and a multiscan type-I Bragg grating exhibits low loss ordinary and extraordinary polarized guiding as well as narrowband reflections in the c-band of optical communications. High bandwidth tunability of more than a peak width and nearly preserved electro-optic coefficients of r(13) = 7.59 pm V(-1) and r(33) = 23.21 pm V(-1) are demonstrated.

Omni-directional L-band antenna for mobile communications

NASA Technical Reports Server (NTRS)

Kim, C. S.; Moldovan, N.; Kijesky, J.

1988-01-01

The principle and design of an L-band omni-directional mobile communication antenna are discussed. The antenna is a circular wave guide aperture with hybrid circuits attached to higher order mode excitation. It produces polarized and symmetric two split beams in elevation. The circular waveguide is fed by eight probes with a 90 degree phase shift between their inputs. Radiation pattern characteristics are controlled by adjusting the aperture diameter and mode excitation. This antenna satisfies gain requirements as well as withstanding the harsh environment.

Energy levels of a quantum particle on a cylindrical surface with non-circular cross-section in electric and magnetic fields

NASA Astrophysics Data System (ADS)

Cruz, Philip Christopher S.; Bernardo, Reginald Christian S.; Esguerra, Jose Perico H.

2017-04-01

We calculate the energy levels of a quantum particle on a cylindrical surface with non-circular cross-section in uniform electric and magnetic fields. Using separation of variables method and a change of independent variable, we show that the problem can be reduced to a one-dimensional Schrödinger equation for a periodic potential. The effects of varying the shape of the cross-section while keeping the same perimeter and the strengths of the electric and magnetic fields are investigated for elliptical, corrugated, and nearly-rectangular tubes with radial dimensions of the order of a nanometer. The geometric potential has minima at the angular positions where there is a significant amount of curvature. For the elliptical and corrugated tubes, it is shown that as the tube departs from the circular shape of cross-section the double-degeneracy between the energy levels is lifted. For the nearly-rectangular tube, it is shown that energy level crossings occur as the horizontal dimension of the tube is varied while keeping the same perimeter and radius of circular corners. The interplay between the curvature and the strength of the electric and magnetic fields determines the overall behavior of the energy levels. As the strength of the electric field increases, the overall potential gets skewed creating a potential well on the side corresponding to the more negative electric potential. The energy levels of the first few excited states approach more positive values while the ground state energy level approaches a more negative value. For large electric fields, all bound state energy levels tend to more negative values. The contribution of weak magnetic fields to the overall potential behaves in the same way as the electric field contribution but with its sign depending on the direction of the component of the momentum parallel to the cylindrical axis. Large magnetic fields lead to pairing of energy levels reminiscent of 2D Landau levels for the elliptical and nearly-rectangular tubes.

Energy levels of a quantum particle on a cylindrical surface with non-circular cross-section in electric and magnetic fields

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cruz, Philip Christopher S., E-mail: pscruz1@up.edu.ph; Bernardo, Reginald Christian S., E-mail: rcbernardo@nip.upd.edu.ph; Esguerra, Jose Perico H., E-mail: jesguerra@nip.upd.edu.ph

We calculate the energy levels of a quantum particle on a cylindrical surface with non-circular cross-section in uniform electric and magnetic fields. Using separation of variables method and a change of independent variable, we show that the problem can be reduced to a one-dimensional Schrödinger equation for a periodic potential. The effects of varying the shape of the cross-section while keeping the same perimeter and the strengths of the electric and magnetic fields are investigated for elliptical, corrugated, and nearly-rectangular tubes with radial dimensions of the order of a nanometer. The geometric potential has minima at the angular positions wheremore » there is a significant amount of curvature. For the elliptical and corrugated tubes, it is shown that as the tube departs from the circular shape of cross-section the double-degeneracy between the energy levels is lifted. For the nearly-rectangular tube, it is shown that energy level crossings occur as the horizontal dimension of the tube is varied while keeping the same perimeter and radius of circular corners. The interplay between the curvature and the strength of the electric and magnetic fields determines the overall behavior of the energy levels. As the strength of the electric field increases, the overall potential gets skewed creating a potential well on the side corresponding to the more negative electric potential. The energy levels of the first few excited states approach more positive values while the ground state energy level approaches a more negative value. For large electric fields, all bound state energy levels tend to more negative values. The contribution of weak magnetic fields to the overall potential behaves in the same way as the electric field contribution but with its sign depending on the direction of the component of the momentum parallel to the cylindrical axis. Large magnetic fields lead to pairing of energy levels reminiscent of 2D Landau levels for the elliptical and nearly-rectangular tubes.« less

Dielectric image line groove antennas for millimeterwaves

NASA Astrophysics Data System (ADS)

Solbach, K.; Wolff, I.

Grooves in the ground plane of dielectric image lines are proposed as a new radiating structure. A figure is included showing the proposed groove structure as a discontinuity in a dielectric image line. A wave incident on the dielectric image line is partly reflected by the discontinuity, partly transmitted across the groove, and partly radiated into space above the line. In a travelling-wave antenna, a number of grooves are arranged below a dielectric guide, with spacings around one guide wavelength to produce a beam in the upper half space. A prescribed aperture distribution can be effected by tapering the series radiation resistance of the grooves. This can be done by adjusting the depths of the grooves with a constant width or by varying the widths of the grooves with a constant depth. Attention is also given to circular grooves. Here, the widths of the holes are chosen so that they can be considered as waveguides operating far below the cut-off frequency of the fundamental circular waveguide mode.

Controlling circular polarization of light emitted by quantum dots using chiral photonic crystal slabs

NASA Astrophysics Data System (ADS)

Lobanov, S. V.; Tikhodeev, S. G.; Gippius, N. A.; Maksimov, A. A.; Filatov, E. V.; Tartakovskii, I. I.; Kulakovskii, V. D.; Weiss, T.; Schneider, C.; Geßler, J.; Kamp, M.; Höfling, S.

2015-11-01

We study the polarization properties of light emitted by quantum dots that are embedded in chiral photonic crystal structures made of achiral planar GaAs waveguides. A modification of the electromagnetic mode structure due to the chiral grating fabricated by partial etching of the waveguide layer has been shown to result in a high circular polarization degree ρc of the quantum dot emission in the absence of external magnetic field. The physical nature of the phenomenon can be understood in terms of the reciprocity principle taking into account the structural symmetry. At the resonance wavelength, the magnitude of | ρc| is predicted to exceed 98%. The experimentally achieved value of | ρc|=81 % is smaller, which is due to the contribution of unpolarized light scattered by grating defects, thus breaking its periodicity. The achieved polarization degree estimated removing the unpolarized nonresonant background from the emission spectra can be estimated to be as high as 96%, close to the theoretical prediction.

A C-band broadband ortho-mode transducer for radioastronomy polarimetry.

PubMed

Ferreira, Ivan S; Tello, Camilo; Bergano, Miguel; Villela, Thyrso; Barbosa, Domingos; Smoot, George F

2016-01-01

We describe the design, the construction and performance of a narrow band ortho-mode transducer, currently used in the 5 GHz polarimetric receiver of the Galactic Emission Mapping project. The ortho-mode transducer was designed to achieve a high degree of transmission within the 400 MHz of the GEM band around the 5 GHz (4.8-5.2 GHz). It is composed of a circular-to-square waveguide transition, a septum polarizer, a thin waveguide coupler and a smooth square-to-rectangular waveguide transition with custom waveguide bends to the output ports. Our simulations and measurements show a very low level of cross-polarization of about -60 dB and a good impedance match for all three ports (S11; S22; S33 < -30 dB) with only 0:25 dB of insertion loss offset across the 400 MHz (4.8-5.2 GHz) of the reception bandwidth.

LASER APPLICATIONS AND OTHER TOPICS IN QUANTUM ELECTRONICS: Reflection of an electromagnetic pulse from a subcritical waveguide taper and from a supercritical-density plasma in a waveguide

NASA Astrophysics Data System (ADS)

Rukhadze, Anri A.; Tarakanov, V. P.

2006-09-01

Two related problems are studied by numerical simulations using the KARAT code: the reflection of the TM01 mode of an electromagnetic pulse from the subcritical taper of the section of a circular waveguide and the reflection of the same pulse from a 'cold' collisionless plasma with a density increasing up to a supercritical value along the waveguide axis. It is shown that in the former case the pulse is totally reflected with an insignificant distortion of its shape, in accordance with the linear theory. In the latter case, the character of reflection depends substantially on the plasma density increase length, the pulse duration, and the wave field amplitude, a significant field deceleration and amplitude growth occurring near the critical point; the pulse absorption in the plasma far exceeds the absorption due to the linear transformation of the incident transverse wave to the longitudinal plasma oscillations.

Phase 2: Array automated assembly task low cost silicon solar array project

NASA Technical Reports Server (NTRS)

Jones, G. T.

1979-01-01

Several microwave systems for use in solar cell fabrication were developed and experimentally tested. The first system used a standing wave rectangular waveguide horn applicator. Satisfactory results were achieved with this system for impedance matching and wafer surface heating uniformity. The second system utilized a resonant TM sub 011 mode cylindrical cavity but could not be employed due to its poor energy coupling efficiency. The third and fourth microwave systems utilized a circular waveguide operating in the TM sub 01 and TM sub 11 but had problems with impedance matching, efficiency, and field uniformity.

Enhancement of output power in a two-section periodical circular waveguide structure using magnetized plasma and a relativistic electron beam

NASA Astrophysics Data System (ADS)

Hasanbeigi, A.; Ashrafi, A.; Mehdian, H.

2018-02-01

In the present paper, the excitation of electromagnetic wave by relativistic electron beam, as a radiation source, in a two-section periodical plasma waveguide is investigated. The dispersion relation of TM wave is derived and then solved numerically. Next, the effect of plasma, as an extra controlling parameter, on this radiation source is investigated. Results show that the presence of magnetized plasma can lead to significant increase in output power and it can be an extra parameter for tuning the frequency by varying the plasma density.

On-chip synthesis of circularly polarized emission of light with integrated photonic circuits.

PubMed

He, Li; Li, Mo

2014-05-01

The helicity of circularly polarized (CP) light plays an important role in the light-matter interaction in magnetic and quantum material systems. Exploiting CP light in integrated photonic circuits could lead to on-chip integration of novel optical helicity-dependent devices for applications ranging from spintronics to quantum optics. In this Letter, we demonstrate a silicon photonic circuit coupled with a 2D grating emitter operating at a telecom wavelength to synthesize vertically emitting, CP light from a quasi-TE waveguide mode. Handedness of the emitted circular polarized light can be thermally controlled with an integrated microheater. The compact device footprint enables a small beam diameter, which is desirable for large-scale integration.

Pure chiral optical fibres.

PubMed

Poladian, L; Straton, M; Docherty, A; Argyros, A

2011-01-17

We investigate the properties of optical fibres made from chiral materials, in which a contrast in optical activity forms the waveguide, rather than a contrast in the refractive index; we refer to such structures as pure chiral fibres. We present a mathematical formulation for solving the modes of circularly symmetric examples of such fibres and examine the guidance and polarisation properties of pure chiral step-index, Bragg and photonic crystal fibre designs. Their behaviour is shown to differ for left- and right-hand circular polarisation, allowing circular polarisations to be isolated and/or guided by different mechanisms, as well as differing from equivalent non-chiral fibres. The strength of optical activity required in each case is quantified.

High-Power X-Band Semiconductor RF Switch for Pulse Compression Systems of Future Colliders

NASA Astrophysics Data System (ADS)

Tantawi, Sami G.; Tamura, Fumihiko

2000-04-01

We describe the potential of semiconductor X-band RF switch arrays as a means of developing high power RF pulse compression systems for future linear colliders. The switch systems described here have two designs. Both designs consist of two 3dB hybrids and active modules. In the first design the module is composed of a cascaded active phase shifter. In the second design the module uses arrays of SPST (Single Pole Single Throw) switches. Each cascaded element of the phase shifter and the SPST switch has similar design. The active element consists of symmetrical three-port tee-junctions and an active waveguide window in the symmetrical arm of the tee-junction. The design methodology of the elements and the architecture of the whole switch system are presented. We describe the scaling law that governs the relation between power handling capability and number of elements. The design of the active waveguide window is presented. The waveguide window is a silicon wafer with an array of four hundred PIN/NIP diodes covering the surface of the window. This waveguide window is located in an over-moded TE01 circular waveguide. The results of high power RF measurements of the active waveguide window are presented. The experiment is performed at power levels of tens of megawatts at X-band.

SYSTEMS FOR EXPOSING MICE TO 2,450-MHZ ELECTROMAGNETIC FIELDS

EPA Science Inventory

Two systems for exposing mice to 2,450-MHz electromagnetic fields are described. In a waveguide system, four mice were placed in a Styrofoam cage and exposed dorsally to circularly polarized electromagnetic fields. The temperature and humidity in the mouse holder were kept consta...

On-chip sub-terahertz surface plasmon polariton transmission lines with mode converter in CMOS

PubMed Central

Liang, Yuan; Yu, Hao; Wen, Jincai; Apriyana, Anak Agung Alit; Li, Nan; Luo, Yu; Sun, Lingling

2016-01-01

An on-chip low-loss and high conversion efficiency plasmonic waveguide converter is demonstrated at sub-THz in CMOS. By introducing a subwavelength periodic corrugated structure onto the transmission line (T-line) implemented by a top-layer metal, surface plasmon polaritons (SPP) are established to propagate signals with strongly localized surface-wave. To match both impedance and momentum of other on-chip components with TEM-wave propagation, a mode converter structure featured by a smooth bridge between the Ground coplanar waveguide (GCPW) with 50 Ω impedance and SPP T-line is proposed. To further reduce area, the converter is ultimately simplified to a gradual increment of groove with smooth gradient. The proposed SPP T-lines with the converter is designed and fabricated in the standard 65 nm CMOS process. Both near-field simulation and measurement results show excellent conversion efficiency from quasi-TEM to SPP modes in a broadband frequency range. The converter achieves wideband impedance matching (<−9 dB) with excellent transmission efficiency (averagely −1.9 dB) from 110 GHz–325 GHz. The demonstrated compact and wideband SPP T-lines with mode converter have shown great potentials to replace existing waveguides as future on-chip THz interconnects. To the best of the author’s knowledge, this is the first time to demonstrate the (sub)-THz surface mode conversion on-chip in CMOS technology. PMID:27444782

Near-zero dispersion flattened, low-loss porous-core waveguide design for terahertz signal transmission

NASA Astrophysics Data System (ADS)

Sultana, Jakeya; Islam, Md. Saiful; Atai, Javid; Islam, Muhammad Rakibul; Abbott, Derek

2017-07-01

We demonstrate a photonic crystal fiber with near-zero flattened dispersion, ultralower effective material loss (EML), and negligible confinement loss for a broad spectrum range. The use of cyclic olefin copolymer Topas with improved core confinement significantly reduces the loss characteristics and the use of higher air filling fraction results in flat dispersion characteristics. The properties such as dispersion, EML, confinement loss, modal effective area, and single-mode operation of the fiber have been investigated using the full-vector finite element method with the perfectly matched layer absorbing boundary conditions. The practical implementation of the proposed fiber is achievable with existing fabrication techniques as only circular-shaped air holes have been used to design the waveguide. Thus, it is expected that the proposed terahertz waveguide can potentially be used for flexible and efficient transmission of terahertz waves.

Passive Q-switching of femtosecond-laser-written Tm:KLu(WO4)2 waveguide lasers by graphene and MoS2 saturable absorbers

NASA Astrophysics Data System (ADS)

Kifle, Esrom; Mateos, Xavier; Vázquez de Aldana, Javier Rodríguez; Ródenas, Airan; Loiko, Pavel; Zakharov, Viktor; Veniaminov, Andrey; Yu, Haohai; Zhang, Huaijin; Chen, Yanxue; Aguiló, Magdalena; Díaz, Francesc; Griebner, Uwe; Petrov, Valentin

2018-02-01

A buried depressed-index channel waveguide with a circular cladding and a core diameter of 40 μm is fabricated in a bulk monoclinic 3 at.% Tm:KLu(WO4)2 crystal by femtosecond direct laser writing. In the continuous-wave regime, the Tm waveguide laser generates 210 mW at 1849.6 nm with a slope efficiency η of 40.8%. Passively Q-switched operation is achieved by inserting transmission-type 2D saturable absorbers (SAs) based on few-layer graphene and MoS2. Using the graphene-SA, a maximum average output power of 25 mW is generated at 1844.8 nm. The pulse characteristics (duration/energy) are 88 ns/18 nJ at a repetition rate of 1.39 MHz.

Aperture excited dielectric antennas

NASA Technical Reports Server (NTRS)

Crosswell, W. F.; Chatterjee, J. S.; Mason, V. B.; Tai, C. T.

1974-01-01

The results of a comprehensive experimental and theoretical study of the effect of placing dielectric objects over the aperture of waveguide antennas are presented. Experimental measurements of the radiation patterns, gain, impedance, near-field amplitude, and pattern and impedance coupling between pairs of antennas are given for various Plexiglas shapes, including the sphere and the cube, excited by rectangular, circular, and square waveguide feed apertures. The waveguide excitation of a dielectric sphere is modeled using the Huygens' source, and expressions for the resulting electric fields, directivity, and efficiency are derived. Calculations using this model show good overall agreement with experimental patterns and directivity measurements. The waveguide under an infinite dielectric slab is used as an impedance model. Calculations using this model agree qualitatively with the measured impedance data. It is concluded that dielectric loaded antennas such as the waveguide excited sphere, cube, or sphere-cylinder can produce directivities in excess of that obtained by a uniformly illuminated aperture of the same cross section, particularly for dielectric objects with dimensions of 2 wavelengths or less. It is also shown that for certain configurations coupling between two antennas of this type is less than that for the same antennas without dielectric loading.

BIOLOGICAL EFFECTS OF LONG-TERM EXPOSURE OF RATS TO 970-MHZ RADIOFREQUENCY RADIATION

EPA Science Inventory

Rats (N=16) exposed individually in circularly polarized waveguides to 970-MHz electromagnetic radiation (SAR=2.5 mW/g, 22 h daily for 70 consecutive days) had significantly higher serum levels of triglycerides, albumin, and total protein compared with sham-irradiated controls. N...

A hybrid waveguide cell for the dielectric properties of reservoir rocks

NASA Astrophysics Data System (ADS)

Siggins, A. F.; Gunning, J.; Josh, M.

2011-02-01

A hybrid waveguide cell is described for broad-band measurements of the dielectric properties of hydrocarbon reservoir rocks. The cell is designed to operate in the radio frequency range of 1 MHz to 1 GHz. The waveguide consists of 50 Ω coaxial lines feeding into a central cylindrical section which contains the sample under test. The central portion of the waveguide acts as a circular waveguide and can accept solid core plugs of 38 mm diameter and lengths from 2 to 150 mm. The central section can also be used as a conventional coaxial waveguide when a central electrode with spring-loaded end collets is installed. In the latter mode the test samples are required to be in the form of hollow cylinders. An additional feature of the cell is that the central section is designed to telescope over a limited range of 1-2 mm with the application of an axial load. Effective pressures up to 35 MPa can be applied to the sample under the condition of uniaxial strain. The theoretical basis of the hybrid waveguide cell is discussed together with calibration results. Two reservoir rocks, a Donnybrook sandstone and a kaolin rich clay, are then tested in the cell, both as hollow cylinders in coaxial mode and in the form of solid core plugs. The complex dielectric properties of the two materials over the bandwidth of 1 MHz to 1 GHz are compared with the results of the two testing methods.

Off-axis spectral beam combining of Bragg reflection waveguide photonic crystal diode lasers

NASA Astrophysics Data System (ADS)

Sun, Fangyuan; Wang, Lijie; Zhao, Yufei; Hou, Guanyu; Shu, Shili; Zhang, Jun; Peng, Hangyu; Tian, Sicong; Tong, Cunzhu; Wang, Lijun

2018-06-01

The spectral beam combining (SBC) of Bragg reflection waveguide photonic crystal (BRW-PC) diode lasers was studied for the first time. An off-axis feedback system was constructed using a stripe mirror and a spatial filter to control beam quality in the external cavity. It was found that the BRW-PC diode lasers with a low divergence and a circular beam provided a simplified and cost-effective SBC. The off-axis feedback broke the beam quality limit of a single element, and an M 2 factor of 3.8 times lower than that of a single emitter in the slow axis was demonstrated.

Integrated Lloyd's mirror on planar waveguide facet as a spectrometer.

PubMed

Morand, Alain; Benech, Pierre; Gri, Martine

2017-12-10

A low-cost and simple Fourier transform spectrometer based on the Lloyd's mirror configuration is proposed in order to have a very stable interferogram. A planar waveguide coupled to a fiber injection is used to spatially disperse the optical beam. A second beam superposed to the previous one is obtained by a total reflection of the incident beam on a vertical glass face integrated in the chip by dicing with a specific circular precision saw. The interferogram at the waveguide output is imaged on a near-infrared camera with an objective lens. The contrast and the fringe period are thus dependent on the type and the fiber position and can be optimized to the pixel size and the length of the camera. Spectral resolution close to λ/Δλ=80 is reached with a camera with 320 pixels of 25 μm width in a wavelength range from O to L bands.

Microfiber Optical Sensors: A Review

PubMed Central

Lou, Jingyi; Wang, Yipei; Tong, Limin

2014-01-01

With diameter close to or below the wavelength of guided light and high index contrast between the fiber core and the surrounding, an optical microfiber shows a variety of interesting waveguiding properties, including widely tailorable optical confinement, evanescent fields and waveguide dispersion. Among various microfiber applications, optical sensing has been attracting increasing research interest due to its possibilities of realizing miniaturized fiber optic sensors with small footprint, high sensitivity, fast response, high flexibility and low optical power consumption. Here we review recent progress in microfiber optical sensors regarding their fabrication, waveguide properties and sensing applications. Typical microfiber-based sensing structures, including biconical tapers, optical gratings, circular cavities, Mach-Zehnder interferometers and functionally coated/doped microfibers, are summarized. Categorized by sensing structures, microfiber optical sensors for refractive index, concentration, temperature, humidity, strain and current measurement in gas or liquid environments are reviewed. Finally, we conclude with an outlook for challenges and opportunities of microfiber optical sensors. PMID:24670720

Novel On-wafer Radiation Pattern Measurement Technique for MEMS Actuator Based Reconfigurable Patch Antennas

NASA Technical Reports Server (NTRS)

Simons, Rainee N.

2002-01-01

The paper presents a novel on-wafer, antenna far field pattern measurement technique for microelectromechanical systems (MEMS) based reconfigurable patch antennas. The measurement technique significantly reduces the time and the cost associated with the characterization of printed antennas, fabricated on a semiconductor wafer or dielectric substrate. To measure the radiation patterns, the RF probe station is modified to accommodate an open-ended rectangular waveguide as the rotating linearly polarized sampling antenna. The open-ended waveguide is attached through a coaxial rotary joint to a Plexiglas(Trademark) arm and is driven along an arc by a stepper motor. Thus, the spinning open-ended waveguide can sample the relative field intensity of the patch as a function of the angle from bore sight. The experimental results include the measured linearly polarized and circularly polarized radiation patterns for MEMS-based frequency reconfigurable rectangular and polarization reconfigurable nearly square patch antennas, respectively.

Determining noise temperatures in beam waveguide systems

NASA Technical Reports Server (NTRS)

Imbriale, W.; Veruttipong, W.; Otoshi, T.; Franco, M.

1994-01-01

A new 34-m research and development antenna was fabricated and tested as a precursor to introducing beam waveguide (BWG) antennas and Ka-band (32 GHz) frequencies into the NASA/JPL Deep Space Network. For deep space use, system noise temperature is a critical parameter. There are thought to be two major contributors to noise temperature in a BWG system: the spillover past the mirrors, and the conductivity loss in the walls. However, to date, there are no generally accepted methods for computing noise temperatures in a beam waveguide system. An extensive measurement program was undertaken to determine noise temperatures in such a system along with a correspondent effort in analytic prediction. Utilizing a very sensitive radiometer, noise temperature measurements were made at the Cassegrain focus, an intermediate focal point, and the focal point in the basement pedestal room. Several different horn diameters were used to simulate different amounts of spillover past the mirrors. Two analytic procedures were developed for computing noise temperature, one utilizing circular waveguide modes and the other a semiempirical approach. The results of both prediction methods are compared to the experimental data.

Electromagnetic Wave Propagation through Circular Waveguides Containing Radially Inhomogeneous Lossy Media

DTIC Science & Technology

1989-08-01

where the slope becomes infinite. This point could represent a cutoff frequency of the two coupled complex modes as a/b increases and the cutin ...a good example of attenuation near the cutin for each mode. A common characteristic throughout these plots, and also very similar to the cc versus a/b

Enhanced Light Extraction from OLEDs Fabricated on Patterned Plastic Substrates

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hippola, Chamika; Kaudal, Rajiv; Manna, Eeshita

A key scientific and technological challenge in organic light-emitting diodes (OLEDs) is enhancing the light outcoupling factor η out, which is typically <20%. This paper reports experimental and modeling results of a promising approach to strongly increase η out by fabricating OLEDs on novel flexible nanopatterned substrates that result in a >2× enhancement in green phosphorescent OLEDs (PhOLEDs) fabricated on corrugated polycarbonate (PC). The external quantum efficiency (EQE) reaches 50% (meaning ηout ≥50%); it increases 2.6x relative to a glass/ITO device and 2× relative to devices on glass/poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) or flat PC/PEDOT:PSS. A significant enhancement is also observed formore » blue PhOLEDs with EQE 1.7× relative to flat PC. The corrugated PC substrates are fabricated efficiently and cost-effectively by direct room-temperature molding. These substrates successfully reduce photon losses due to trapping/waveguiding in the organic+anode layers and possibly substrate, and losses to plasmons at the metal cathode. Focused ion beam gauged the conformality of the OLEDs. Dome-shaped convex nanopatterns with height of ~280–400 nm and pitch ~750–800 nm were found to be optimal. Lastly, substrate design and layer thickness simulations, reported first for patterned devices, agree with the experimental results that present a promising method to mitigate photon loss paths in OLEDs.« less

Enhanced Light Extraction from OLEDs Fabricated on Patterned Plastic Substrates

DOE PAGES

Hippola, Chamika; Kaudal, Rajiv; Manna, Eeshita; ...

2018-02-19

A key scientific and technological challenge in organic light-emitting diodes (OLEDs) is enhancing the light outcoupling factor η out, which is typically <20%. This paper reports experimental and modeling results of a promising approach to strongly increase η out by fabricating OLEDs on novel flexible nanopatterned substrates that result in a >2× enhancement in green phosphorescent OLEDs (PhOLEDs) fabricated on corrugated polycarbonate (PC). The external quantum efficiency (EQE) reaches 50% (meaning ηout ≥50%); it increases 2.6x relative to a glass/ITO device and 2× relative to devices on glass/poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) or flat PC/PEDOT:PSS. A significant enhancement is also observed formore » blue PhOLEDs with EQE 1.7× relative to flat PC. The corrugated PC substrates are fabricated efficiently and cost-effectively by direct room-temperature molding. These substrates successfully reduce photon losses due to trapping/waveguiding in the organic+anode layers and possibly substrate, and losses to plasmons at the metal cathode. Focused ion beam gauged the conformality of the OLEDs. Dome-shaped convex nanopatterns with height of ~280–400 nm and pitch ~750–800 nm were found to be optimal. Lastly, substrate design and layer thickness simulations, reported first for patterned devices, agree with the experimental results that present a promising method to mitigate photon loss paths in OLEDs.« less

Color waveguide transparent screen using lens array holographic optical element

NASA Astrophysics Data System (ADS)

Liu, Siqi; Sun, Peng; Wang, Chang; Zheng, Zhenrong

2017-11-01

A color transparent screen was designed in this paper, a planar glass was used as a waveguide structure and the lens array holographic optical element (HOE) was used as a display unit. The lens array HOE was exposed by two coherent beams. One was the reference wave which directly illuminated on the holographic material and the other was modulated by the micro lens array. The lens array HOE can display the images with see-through abilities. Unlike the conventional lens array HOE, a planar glass was adopted as the waveguide in the experiment. The projecting light was totally internal-reflected in the planar glass to eliminate the undesired zero-order diffracted light. By using waveguide, it also brings advantage of compact structure. Colorful display can be realized in our system as the holographic materials were capable for multi-wavelength display. In this paper, a color transparent screen utilizing the lens array HOE and waveguide were designed. Experiment results showed a circular display area on the transparent screen. The diameter of the area is 20 mm and it achieved the pixel resolution of 100 μm. This simple and effective method could be an alternative in the augment reality (AR) applications, such as transparent phone and television.

Fabrication of low loss waveguide using fundamental light of Yb-based femtosecond laser (Conference Presentation)

NASA Astrophysics Data System (ADS)

Imai, Ryo; Konishi, Kuniaki; Yumoto, Junji; Gonokami, Makoto K.

2017-03-01

Laser direct writing of optical devices and circuits is attracted attention because of its ability of three-dimensional fabrication without any mask[1]. Recently, Yb-fiber or solid-state laser has been commonly used for fabrication in addition to traditional Ti:S laser. However, it is reported that waveguide cannot be fabricated in fused silica by using the fundamental light from Yb-based femtosecond laser[2]. Some groups reported on waveguide fabrication by using second-harmonic beam of such lasers[3], but wavelength conversion using nonlinear process has drawbacks such as destabilization of laser power and beam deformation by walk off. In this study, we investigated fabrication of low-loss waveguide in fused silica by using the fundamental beam (1030nm) from an Yb solid-state femtosecond laser with a pulse duration of 250 fs. The NA of focusing objective lens was 0.42. The fabricated waveguide was made to have a circular cross-section by shaping laser beam with a slit[4]. We fixed repetition rate to 150 kHz, and identified appropriate scan speed and pulse energy for fabrication of low loss waveguide. Waveguide fabricated with appropriate condition had a propagation loss of 0.2 dB/cm, and this is the first report on optical waveguides in a fused silica fabricated by femto-second laser pulses at a wavelength of 1030nm. [1]K. M. Davis, et. al., Opt. Lett 21, 1729(1996) [2]J. Canning, et. al., Opt. Mater. Express 1, 998(2011) [3]L. Shah, et. al., Opt. Express 13, 1999(2005) [4]M. Ams, et. al., Opt. Express 13, 5676(2005)

Design and implementation of optical switches based on nonlinear plasmonic ring resonators: Circular, square and octagon

NASA Astrophysics Data System (ADS)

Ghadrdan, Majid; Mansouri-Birjandi, Mohammad Ali

2018-05-01

In this paper, all-optical plasmonic switches (AOPS) based on various configurations of circular, square and octagon nonlinear plasmonic ring resonators (NPRR) were proposed and numerically investigated. Each of these configurations consisted of two metal-insulator-metal (MIM) waveguides coupled to each other by a ring resonator (RR). Nonlinear Kerr effect was used to show switching performance of the proposed NPRR. The result showed that the octagon switch structure had lower threshold power and higher transmission ratio than square and circular switch structures. The octagon switch structure had a low threshold power equal to 7.77 MW/cm2 and the high transmission ratio of approximately 0.6. Therefore, the octagon switch structure was an appropriate candidate to be applied in optical integration circuits as an AOPS.

Microwave transmission efficiency and simulations of electron plasma in ELTRAP device

NASA Astrophysics Data System (ADS)

Ikram, M.; Mushtaq, A.; Ali, S.

2017-11-01

A Thomson backscattering experiment has been performed in a Penning-Malmberg device ELTRAP. To estimate the minimum sensitivity of diagnostics, we have computed the signal to noise ratio and found that the present bunch has a number density of 4.3 × 108 cm-3, which is three orders of magnitude less than the desired density of 1011 cm-3. To increase the signal level from the RF studies to the GHz range, the transmission efficiency from the rectangular waveguide orthogonally coupled to a prototype circular waveguide was experimentally analyzed on a test-bench. It is observed that the lengths of waveguides play an important role in the transmission efficiency and return loss. When the length of the optimum rectangular waveguide (>2 λg = 31 cm) is reduced to 7 cm, due to geometrical constraints of the ELTRAP device, consequently, the transmission efficiency is also reduced and shifts away from the maximum 3 GHz operating frequency. The useful frequency band is then reduced with the increasing length of the prototype circular waveguide (102 cm). Using the electromagnetic Particle-In-Cell simulations involving the electron cyclotron resonance heating (ECRH), we have utilized a magnetic field of 0.1 T resonating with 2.8 GHz RF drive during each time step (1 ps) having the power level of 0.04 V to the middle and to the end of the trap. A more efficient increase in the radial and azimuthal temperature profiles is observed as compared to the axial temperature profile. The reason is the use of ECRH to heat electrons in cyclotron motion, which is completely kinetic and magnetron motion which is almost entirely potential based. The axial motion interchanges in between the kinetic and potential with a slight enhancement in axial motion to maintain the total canonical angular momentum conserved. The temperature profile of the confined electron plasma increases with the variation of densities from 5 × 107 m-3 to 1012 m-3. The major heating effect occurs when the RF power is injected from the position close to one end with respect to the middle position of the trap.

A parametric study of cut-off corrugated surface properties

NASA Technical Reports Server (NTRS)

Mentzer, C. A.; Peters, L., Jr.

1973-01-01

Corrugated horns involve a junction between the corrugated surface and a conducting groundplane. Proper horn design requires an understanding of the electromagnetic properties of the corrugated surface and this junction. Therefore, an integral equation solution has been used to study the influence of corrugation density and shape on the power loss. Surface current, and the scattering from a groundplane-corrugated surface junction. Both square and vee shape corrugations have been considered over the range of corrugation depths where the surface acts as a cut-off corrugated surface.

Properties of cutoff corrugated surfaces for corrugated horn design. [corrugation shape and density effects on scattering

NASA Technical Reports Server (NTRS)

Mentzer, C. A.; Peters, L., Jr.

1974-01-01

Corrugated horns involve a junction between the corrugated surface and a conducting ground plane. Proper horn design requires an understanding of the electromagnetic properties of the corrugated surface and this junction. An integral equation solution has been used to study the influence of corrugation density and tooth thickness on the power loss, surface current, and the scattering from a ground plane/corrugated surface junction.

Design of the ITER Electron Cyclotron Heating and Current Drive Waveguide Transmission Line

NASA Astrophysics Data System (ADS)

Bigelow, T. S.; Rasmussen, D. A.; Shapiro, M. A.; Sirigiri, J. R.; Temkin, R. J.; Grunloh, H.; Koliner, J.

2007-11-01

The ITER ECH transmission line system is designed to deliver the power, from twenty-four 1 MW 170 GHz gyrotrons and three 1 MW 127.5 GHz gyrotrons, to the equatorial and upper launchers. The performance requirements, initial design of components and layout between the gyrotrons and the launchers is underway. Similar 63.5 mm ID corrugated waveguide systems have been built and installed on several fusion experiments; however, none have operated at the high frequency and long-pulse required for ITER. Prototype components are being tested at low power to estimate ohmic and mode conversion losses. In order to develop and qualify the ITER components prior to procurement of the full set of 24 transmission lines, a 170 GHz high power test of a complete prototype transmission line is planned. Testing of the transmission line at 1-2 MW can be performed with a modest power (˜0.5 MW) tube with a low loss (10-20%) resonant ring configuration. A 140 GHz long pulse, 400 kW gyrotron will be used in the initial tests and a 170 GHz gyrotron will be used when it becomes available. Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U.S. Dept. of Energy under contract DE-AC05-00OR22725.

Co-simulation of a complete rectenna with a circular slot loop antenna in CPW technology

NASA Astrophysics Data System (ADS)

Rivière, Jérôme; Douyère, Alexandre; Cazour, Jonathan; Alicalapa, Frédéric; Luk, Jean-Daniel Lan Sun

2017-05-01

This study starts with the design of a planar and compact CPW antenna fabricated on Arlon AD1000 substrate, ɛr=10.35. The antenna is a coplanar waveguide (CPW) fed circular slot loop antenna matched to the standard impedance 50 Ω by two stubs. The goal is to implement this antenna with a CPW RF/DC rectifier to build an optimized low power level rectenna. The rectenna design is restricted to allow easy and fast fabrication of an array with a high reproducibility. The full rectenna is simulated and achieves 10% effciency at -20 dBm.

Experimental Testing of a Metamaterial Slow Wave Structure for High-Power Microwave Generation

NASA Astrophysics Data System (ADS)

Shipman, K.; Prasad, S.; Andreev, D.; Fisher, D. M.; Reass, D. B.; Schamiloglu, E.; Gilmore, M.

2017-10-01

A high-power L band source has been developed using a metamaterial (MTM) to produce a double negative slow wave structure (SWS) for interaction with an electron beam. The beam is generated by a 700 kV, 6 kA short pulse (10 ns) accelerator. The design of the SWS consists of a cylindrical waveguide, loaded with alternating split-rings that are arrayed axially down the waveguide. The beam is guided down the center of the rings, where electrons interact with the MTM-SWS producing radiation. Power is extracted axially via a circular waveguide, and radiated by a horn antenna. Microwaves are characterized by an external detector placed in a waveguide. Mode characterization is performed using a neon bulb array. The bulbs are lit by the electric field, resulting in an excitation pattern that resembles the field pattern. This is imaged using an SLR camera. The MTM structure has electrically small features so breakdown is a concern. In addition to high speed cameras, a fiber-optic-fed, sub-ns photomultiplier tube array diagnostic has been developed and used to characterize breakdown light. Work supported by the Air Force Office of Scientific Research, MURI Grant FA9550-12-1-0489.

Electron dynamics and transverse-kick elimination in a high-field short-period helical microwave undulator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, C.; Shumail, M.; Tantawi, S.

2012-10-15

Single electron dynamics for a circular polarized standing wave (CPSW) undulator synthesized from a corrugated cavity operating with a very low-loss HE{sub 11} mode are analyzed. The mechanism of the transverse drift of the CPSW undulator and its elimination are researched, and the tapered-field ends are found effectively to suppress the kick. A prototype of the CPSW undulator with the characters of short undulating-period 1.4 cm, high field K {approx} 1, large aperture {approx} 5 cm, and variable polarization is designed and modeled, whose 3-dimensional electromagnetic fields are used to research the suppression of the transverse kick.

Analysis of the electromagnetic scattering from an inlet geometry with lossy walls

NASA Technical Reports Server (NTRS)

Myung, N. H.; Pathak, P. H.; Chunang, C. D.

1985-01-01

One of the primary goals is to develop an approximate but sufficiently accurate analysis for the problem of electromagnetic (EM) plane wave scattering by an open ended, perfectly-conducting, semi-infinite hollow circular waveguide (or duct) with a thin, uniform layer of lossy or absorbing material on its inner wall, and with a simple termination inside. The less difficult but useful problem of the EM scattering by a two-dimensional (2-D), semi-infinite parallel plate waveguide with an impedance boundary condition on the inner walls was chosen initially for analysis. The impedance boundary condition in this problem serves to model a thin layer of lossy dielectric/ferrite coating on the otherwise perfectly-conducting interior waveguide walls. An approximate but efficient and accurate ray solution was obtained recently. That solution is presently being extended to the case of a moderately thick dielectric/ferrite coating on the walls so as to be valid for situations where the impedance boundary condition may not remain sufficiently accurate.

Polarizability extraction of complementary metamaterial elements in waveguides for aperture modeling

NASA Astrophysics Data System (ADS)

Pulido-Mancera, Laura; Bowen, Patrick T.; Imani, Mohammadreza F.; Kundtz, Nathan; Smith, David

2017-12-01

We consider the design and modeling of metasurfaces that couple energy from guided waves to propagating wave fronts. To this purpose, we develop a comprehensive, multiscale dipolar interpretation for large arrays of complementary metamaterial elements embedded in a waveguide structure. Within this modeling technique, the detailed electromagnetic response of each metamaterial element is replaced by a polarizable dipole, described by means of an effective polarizability. In this paper, we present two methods to extract this effective polarizability. The first method invokes surface equivalence principles, averaging over the effective surface currents and charges induced in the element's surface in order to obtain the effective dipole moments, from which the effective polarizability can be inferred. The second method is based in the coupled-mode theory, from which a direct relationship between the effective polarizability and the amplitude coefficients of the scattered waves can be deduced. We demonstrate these methods on several variants of waveguide-fed metasurface elements (both one- and two-dimensional waveguides), finding excellent agreement between the two, as well as with the analytical expressions derived for circular and elliptical irises. With the effective polarizabilities of the metamaterial elements accurately determined, the radiated fields generated by a waveguide-fed metasurface can be found self-consistently by including the interactions between polarizable dipoles. The dipole description provides an effective perspective and computational framework for engineering metasurface structures such as holograms, lenses, and beam-forming arrays, among others.

Waveguides having patterned, flattened modes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Messerly, Michael J.; Pax, Paul H.; Dawson, Jay W.

Field-flattening strands may be added to and arbitrarily positioned within a field-flattening shell to create a waveguide that supports a patterned, flattened mode. Patterning does not alter the effective index or flattened nature of the mode, but does alter the characteristics of other modes. Compared to a telecom fiber, a hexagonal pattern of strands allows for a three-fold increase in the flattened mode's area without reducing the separation between its effective index and that of its bend-coupled mode. Hexagonal strand and shell elements prove to be a reasonable approximation, and, thus, to be of practical benefit vis-a-vis fabrication, to thosemore » of circular cross section. Patterned flattened modes offer a new and valuable path to power scaling.« less

Design and characterization of a W-band system for modulated DNP experiments.

PubMed

Guy, Mallory L; Zhu, Lihuang; Ramanathan, Chandrasekhar

2015-12-01

Magnetic-field and microwave-frequency modulated DNP experiments have been shown to yield improved enhancements over conventional DNP techniques, and even to shorten polarization build-up times. The resulting increase in signal-to-noise ratios can lead to significantly shorter acquisition times in signal-limited multi-dimensional NMR experiments and pave the way to the study of even smaller sample volumes. In this paper we describe the design and performance of a broadband system for microwave frequency- and amplitude-modulated DNP that has been engineered to minimize both microwave and thermal losses during operation at liquid helium temperatures. The system incorporates a flexible source that can generate arbitrary waveforms at 94GHz with a bandwidth greater than 1GHz, as well as a probe that efficiently transmits the millimeter waves from room temperature outside the magnet to a cryogenic environment inside the magnet. Using a thin-walled brass tube as an overmoded waveguide to transmit a hybrid HE11 mode, it is possible to limit the losses to 1dB across a 2GHz bandwidth. The loss is dominated by the presence of a quartz window used to isolate the waveguide pipe. This performance is comparable to systems with corrugated waveguide or quasi-optical components. The overall excitation bandwidth of the probe is seen to be primarily determined by the final antenna or resonator used to excite the sample and its coupling to the NMR RF coil. Understanding the instrumental limitations imposed on any modulation scheme is key to understanding the observed DNP results and potentially identifying the underlying mechanisms. We demonstrate the utility of our design with a set of triangular frequency-modulated DNP experiments. Copyright © 2015 Elsevier Inc. All rights reserved.

Aerodynamic effects of corrugation and deformation in flapping wings of hovering hoverflies.

PubMed

Du, Gang; Sun, Mao

2012-05-07

We investigated the aerodynamic effects of wing deformation and corrugation of a three-dimensional model hoverfly wing at a hovering condition by solving the Navier-Stokes equations on a dynamically deforming grid. Various corrugated wing models were tested. Insight into whether or not there existed significant aerodynamic coupling between wing deformation (camber and twist) and wing corrugation was obtained by comparing aerodynamic forces of four cases: a smooth-plate wing in flapping motion without deformation (i.e. a rigid flat-plate wing in flapping motion); a smooth-plate wing in flapping motion with deformation; a corrugated wing in flapping motion without deformation (i.e. a rigid corrugated wing in flapping motion); a corrugated wing in flapping motion with deformation. There was little aerodynamic coupling between wing deformation and corrugation: the aerodynamic effect of wing deformation and corrugation acting together was approximately a superposition of those of deformation and corrugation acting separately. When acting alone, the effect of wing deformation was to increase the lift by 9.7% and decrease the torque (or aerodynamic power) by 5.2%, and that of wing corrugation was to decrease the lift by 6.5% and increase the torque by 2.2%. But when acting together, the wing deformation and corrugation only increased the lift by ~3% and decreased the torque by ~3%. That is, the combined aerodynamic effect of deformation and corrugation is rather small. Thus, wing corrugation is mainly for structural, not aerodynamic, purpose, and in computing or measuring the aerodynamic forces, using a rigid flat-plate wing to model the corrugated deforming wing at hovering condition can be a good approximation. Copyright © 2012 Elsevier Ltd. All rights reserved.

Dispersion analysis and measurement of circular cylindrical wedge-like acoustic waveguides.

PubMed

Yu, Tai-Ho

2015-09-01

This study investigated the propagation of flexural waves along the outer edge of a circular cylindrical wedge, the phase velocities, and the corresponding mode displacements. Thus far, only approximate solutions have been derived because the corresponding boundary-value problems are complex. In this study, dispersion curves were determined using the bi-dimensional finite element method and derived through the separation of variables and the Hamilton principle. Modal displacement calculations clarified that the maximal deformations appeared at the outer edge of the wedge tip. Numerical examples indicated how distinct thin-film materials deposited on the outer surface of the circular cylindrical wedge influenced the dispersion curves. Additionally, dispersion curves were measured using a laser-induced guided wave, a knife-edge measurement scheme, and a two-dimensional fast Fourier transform method. Both the numerical and experimental results correlated closely, thus validating the numerical solution. Copyright © 2015 Elsevier B.V. All rights reserved.

A New Approach to Suppress the Effect of Machining Error for Waveguide Septum Circular Polarizer at 230 GHz Band in Radio Astronomy

NASA Astrophysics Data System (ADS)

Hasegawa, Yutaka; Harada, Ryohei; Tokuda, Kazuki; Kimura, Kimihiro; Ogawa, Hideo; Onishi, Toshikazu; Nishimura, Atsushi; Han, Johnson; Inoue, Makoto

2017-05-01

A new stepped septum-type waveguide circular polarizer (SST-CP) was developed to operate in the 230 GHz band for radio astronomy, especially submillimeter-band VLBI observations. For previously reported SST-CP models, the 230 GHz band is too high to achieve the design characteristics in manufactured devices because of unexpected machining errors. To realize a functional SST-CP that can operate in the submillimeter band, a new method was developed, in which the division surface is shifted from the top step of the septum to the second step from the top, and we simulated the expected machining error. The SST-CP using this method can compensate for specified machining errors and suppress serious deterioration. To verify the proposed method, several test pieces were manufactured, and their characteristics were measured using a VNA. These results indicated that the insertion losses were approximately 0.75 dB, and the input return losses and the crosstalk of the left- and right-hand circular polarization were greater than 20 dB at 220-245 GHz on 300 K. Moreover, a 230 GHz SST-CP was developed by the proposed method and installed in a 1.85-m radio telescope receiver systems, and then had used for scientific observations during one observation season without any problems. These achievements demonstrate the successful development of a 230 GHz SST-CP for radio astronomical observations. Furthermore, the proposed method can be applicable for observations in higher frequency bands, such as 345 GHz.

Overmoded subterahertz surface wave oscillator with pure TM{sub 01} mode output

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Guangqiang; Zeng, Peng; Wang, Dongyang

2016-02-15

Overmoded O-type Cerenkov generators using annular electron beams are facing the problem of multi-modes output due to the inevitable structural discontinuities. A simple but effective method to achieve the pure TM{sub 01} mode output is applied on the 0.14 THz overmoded surface wave oscillator (SWO) in this paper. In spite of still using an overmoded slow wave structure to ensure the easy fabrication, the followed smooth circular waveguide is shrinkingly tapered to the output waveguide with appropriate radius that it cuts off other higher modes except TM{sub 01} mode. Moreover, the modified device here has the same power capacity as themore » previous one according to the numerical analysis. By optimized lengths of the transition waveguide and tapered waveguide, particle-in-cell simulation results indicate that the subterahertz wave with output power increased 14.2% at the same frequency is obtained from the proposed SWO under the previous input conditions, and importantly, the output power is all carried by TM{sub 01} mode as expected. Further simulation results in the pulse regime confirm the feasibility of the optimized structure in the actual experiments. This simple and viable design is also applicable to overmoded devices in the lower frequency band of subterahertz wave.« less

Diode-laser pumping into the emitting level for efficient lasing of depressed cladding waveguides realized in Nd:YVO4 by the direct femtosecond-laser writing technique.

PubMed

Pavel, Nicolaie; Salamu, Gabriela; Jipa, Florin; Zamfirescu, Marian

2014-09-22

Depressed cladding waveguides have been realized in Nd:YVO(4) employing direct writing technique with a femtosecond-laser beam. It was shown that the output performances of such laser devices are improved by the reduction of the quantum defect between the pump wavelength and the laser wavelength. Thus, under the classical pump at 808 nm (i.e. into the (4)F(5/2) level), a 100-μm diameter circular waveguide inscribed in a 0.7-at.% Nd:YVO(4) outputted 1.06-μm laser pulses with 3.0-mJ energy, at 0.30 optical efficiency and slope efficiency of 0.32. The pump at 880 nm (i.e.directly into the (4)F(3/2) emitting level) increased the pulse energy at 3.8 mJ and improved both optical efficiency and slope efficiency at 0.36 and 0.39, respectively. The same waveguide yielded continuous-wave 1.5-W output power at 1.06 μm under the pump at 880 nm. Laser emission at 1.34 μm was also improved using the pump into the (4)F(3/2) emitting level of Nd:YVO(4).

NASA Tech Briefs, December 2010

NASA Technical Reports Server (NTRS)

2010-01-01

Topics include: Coherent Frequency Reference System for the NASA Deep Space Network; Diamond Heat-Spreader for Submillimeter-Wave Frequency Multipliers; 180-GHz I-Q Second Harmonic Resistive Mixer MMIC; Ultra-Low-Noise W-Band MMIC Detector Modules; 338-GHz Semiconductor Amplifier Module; Power Amplifier Module with 734-mW Continuous Wave Output Power; Multiple Differential-Amplifier MMICs Embedded in Waveguides; Rapid Corner Detection Using FPGAs; Special Component Designs for Differential-Amplifier MMICs; Multi-Stage System for Automatic Target Recognition; Single-Receiver GPS Phase Bias Resolution; Ultra-Wideband Angle-of-Arrival Tracking Systems; Update on Waveguide-Embedded Differential MMIC Amplifiers; Automation Framework for Flight Dynamics Products Generation; Product Operations Status Summary Metrics; Mars Terrain Generation; Application-Controlled Parallel Asynchronous Input/Output Utility; Planetary Image Geometry Library; Propulsion Design With Freeform Fabrication (PDFF); Economical Fabrication of Thick-Section Ceramic Matrix Composites; Process for Making a Noble Metal on Tin Oxide Catalyst; Stacked Corrugated Horn Rings; Refinements in an Mg/MgH2/H2O-Based Hydrogen Generator; Continuous/Batch Mg/MgH2/H2O-Based Hydrogen Generator; Strain System for the Motion Base Shuttle Mission Simulator; Ko Displacement Theory for Structural Shape Predictions; Pyrotechnic Actuator for Retracting Tubes Between MSL Subsystems; Surface-Enhanced X-Ray Fluorescence; Infrared Sensor on Unmanned Aircraft Transmits Time-Critical Wildfire Data; and Slopes To Prevent Trapping of Bubbles in Microfluidic Channels.

Optical modelling of far-infrared astronomical instrumentation exploiting multimode horn antennas

NASA Astrophysics Data System (ADS)

O'Sullivan, Créidhe; Murphy, J. Anthony; Mc Auley, Ian; Wilson, Daniel; Gradziel, Marcin L.; Trappe, Neil; Cahill, Fiachra; Peacocke, T.; Savini, G.; Ganga, K.

2014-07-01

In this paper we describe the optical modelling of astronomical telescopes that exploit bolometric detectors fed by multimoded horn antennas. In cases where the horn shape is profiled rather than being a simple cone, we determine the beam at the horn aperture using an electromagnetic mode-matching technique. Bolometers, usually placed in an integrating cavity, can excite many hybrid modes in a corrugated horn; we usually assume they excite all modes equally. If the waveguide section feeding the horn is oversized these modes can propagate independently, thereby increasing the throughput of the system. We use an SVD analysis on the matrix that describes the scattering between waveguide (TE/TM) modes to recover the independent orthogonal fields (hybrid modes) and then propagate these to the sky independently where they are added in quadrature. Beam patterns at many frequencies across the band are then added with a weighting appropriate to the source spectrum. Here we describe simulations carried out on the highest-frequency (857-GHz) channel of the Planck HFI instrument. We concentrate in particular on the use of multimode feedhorns and consider the effects of possible manufacturing tolerances on the beam on the sky. We also investigate the feasibility of modelling far-out sidelobes across a wide band for electrically large structures and bolometers fed by multi-mode feedhorns. Our optical simulations are carried out using the industry-standard GRASP software package.

Theory of Gyrotron Traveling Wave Amplifiers at Harmonics of the Gyration Frequency

NASA Astrophysics Data System (ADS)

Li, Qiangfa

In developing gyrotrons at millimeter and submillimeter wavelengths, a means of operation at lower applied magnetic fields is desirable because of the size and weight of convetional magnets, and the expense and complexity of cryogenic magnets. This requirement can be met by operating the devices at higher harmonics of the electron gyration frequency. In the present work, a unified theory is developed for the gyrotron traveling wave amplifers (gyro-TWA) at harmonics of the gyration frequency, both in the nonlinear regime and in the linear regime. This theory can be applied to a wide class of waveguide cross sections, arbitrary harmonic number, any waveguide mode, and generalized electron beam model. The fields in the beam-field interaction region in the waveguide are expressed in the form of an infinite series of multipoles expanded around the guiding center of the electrons. A set of equations governing the nonlinear behavior of the gyro-TWA is derived. A general dispersion equation is derived both from that set of nonlinear equations by an iteration method and from plasma kinetic theory. The latter is employed to analyze gyro-TWA devices in a systematic and generalized manner. The Laplace transformation is introduced to allow inclusion of the initial values at the input end of the waveguide. From the linear theory it is found that for a gyrotron working at s-th gyration harmonic the electrons can interact only with the 2s-th order multipole field component. It is also found that a higher order waveguide mode is not always better than a lower order mode for the gyro-TWA working at higher harmonics. A novel out-ridged waveguide is proposed and analyzed for the use in gyrotrons. The prominent features of this new waveguide include simplicity of manufacture, freedom from local modes, good separation of lower order modes, high power handling ability, and high gain per unit length at higher gyration harmonics. A comparison of the gyro-TWAs with several different waveguide structures, such as the out-ridged, magnetron-type, rectangular and circular waveguides, is made through numerical examples of the gain-frequency curves computed from the linear kinetic theory.

Test of superplastically formed corrugated aluminum compression specimens with beaded webs

NASA Technical Reports Server (NTRS)

Davis, Randall C.; Royster, Dick M.; Bales, Thomas T.; James, William F.; Shinn, Joseph M., Jr.

1991-01-01

Corrugated wall sections provide a highly efficient structure for carrying compressive loads in aircraft and spacecraft fuselages. The superplastic forming (SPF) process offers a means to produce complex shells and panels with corrugated wall shapes. A study was made to investigate the feasibility of superplastically forming 7475-T6 aluminum sheet into a corrugated wall configuration and to demonstrate the structural integrity of the construction by testing. The corrugated configuration selected has beaded web segments separating curved-cap segments. Eight test specimens were fabricated. Two specimens were simply a single sheet of aluminum superplastically formed to a beaded-web, curved-cap corrugation configuration. Six specimens were single-sheet corrugations modified by adhesive bonding additional sheet material to selectively reinforce the curved-cap portion of the corrugation. The specimens were tested to failure by crippling in end compression at room temperature.

Design and simulation of MEMS microvalves for silicon photonic biosensor chip

NASA Astrophysics Data System (ADS)

Amemiya, Yoshiteru; Nakashima, Yuuto; Maeda, Jun; Yokoyama, Shin

2018-04-01

For the early and easy diagnosis of diseases, we have proposed a silicon photonic biosensor chip with two kinds of MEMS microvalves for a multiple-item detection system. The driving voltage of the vertical type with the circular-plate capacitor structure and that of the lateral type with the comb-shaped electrode are investigated. From mechanical calculations, the driving voltage of the vertical type is estimated to be 30 V and that of the lateral type to be 15 V. The propagation loss at the intersecting waveguides of arrayed ring-resonator biosensors is also estimated. In the case of optimized intersecting waveguides, more than 67% transmittance of TE-mode light is simulated for the series connection of 20 intersecting waveguides. It is confirmed that it is possible to fabricate an 8 × 12 arrayed biosensor chip in an area of 1 × 1.5 mm2 taking the device size of the microvalves into consideration. We have, for the first time, designed a whole system, including sensors and a fluid channel with MEMS microvalves.

Microstructured optical fibers for terahertz waveguiding regime by using an analytical field model

NASA Astrophysics Data System (ADS)

Sharma, Dinesh Kumar; Sharma, Anurag; Tripathi, Saurabh Mani

2017-12-01

Microstructured optical fibres (MOFs) are seen as novel optical waveguide for the potential applications in the terahertz (THz) band as they provide a flexible route towards THz waveguiding. Using the analytical field model (Sharma et al., 2014) developed for index-guiding MOFs with hexagonal lattice of circular air-holes in the photonic crystal cladding; we aim to study the propagation characteristics such as effective index, near and the far-field radiation patterns and its evolution from near-to-far-field domain, spot size, effective mode area, and the numerical aperture at the THz regime. Further, we present an analytical field expression for the next higher-order mode of the MOF for studying the modal properties at terahertz frequencies. Also, we investigate the mode cut-off conditions for identifying the single-mode operation range at THz frequencies. Emphasis is put on studying the coupling characteristics of MOF geometries for efficient mode coupling. Comparisons with available experimental and numerical simulation results, e.g., those based on the full-vector finite element method (FEM) and the finite-difference frequency-domain (FDFD) method have been included.

Concentration methods for high-resolution THz spectroscopy of nucleic-acid biomolecules and crystals

NASA Astrophysics Data System (ADS)

Brown, E. R.; Zhang, W.; Mendoza, E. A.; Kuznetsova, Y.; Brueck, S. R. J.; Rahman, M.; Norton, M. L.

2012-03-01

Biomolecules can exhibit low-lying vibrational modes in the THz region which are detectable in transmission given a strong molecular dipole moment and optical depth, and a spectrometer of adequate sensitivity. The nucleic acids are particularly interesting because of applications such as label-free gene assay, bio-agent detection, etc. However for nucleic acids, sample preparation and THz coupling are of paramount importance because of the strong absorption by liquid water and the small concentration of molecules present in physiological solutions. Concentration methods become necessary to make the THz vibrational modes detectable, either by concentrating the nucleic-acid sample itself in a small volume but large area, or by concentrating the THz radiation down to the volume of the sample. This paper summarizes one type of the first method: nanofluidic channel arrays for biological nucleic acids; and two types of the second method: (1) a circular-waveguide pinhole, and (2) a circular-waveguide, conical-horn coupling structure, both for DNA crystals. The first method has been demonstrated on a very short artificial nucleic acid [small-interfering (si) RNA (17-to-25 bp)] and a much longer, biological molecule [Lambda-phage DNA (48.5 kbp)]. The second method has been demonstrated on small (~100 micron) single crystals of DNA grown by the sitting-drop method.

Rotational MEMS mirror with latching arm for silicon photonics

NASA Astrophysics Data System (ADS)

Brière, Jonathan; Beaulieu, Philippe-Olivier; Saidani, Menouer; Nabki, Frederic; Menard, Michaël.

2015-02-01

We present an innovative rotational MEMS mirror that can control the direction of propagation of light beams inside of planar waveguides implemented in silicon photonics. Potential applications include but are not limited to optical telecommunications, medical imaging, scan and spectrometry. The mirror has a half-cylinder shape with a radius of 300 μm that provides low and constant optical losses over the full angular displacement range. A circular comb drive structure is anchored such that it allows free or latched rotation experimentally demonstrated over 8.5° (X-Y planar rotational movement) using 290V electrostatic actuation. The entire MEMS structure was implemented using the MEMSCAP SOIMUMPs process. The center of the anchor beam is designed to be the approximate rotation point of the circular comb drive to counter the rotation offset of the mirror displacement. A mechanical characterization of the MEMS mirror is presented. The latching mechanism provides up to 20 different angular locking positions allowing the mirror to counter any resonance or vibration effects and it is actuated with an electrostatic linear comb drive. An innovative gap closing structure was designed to reduce optical propagation losses due to beam divergence in the interstitial space between the mirror and the planar waveguide. The gap closing structure is also electrostatically actuated and includes two side stoppers to prevent stiction.

Porus electrode comprising a bonded stack of pieces of corrugated metal foil

NASA Technical Reports Server (NTRS)

Mccallum, J. (Inventor)

1973-01-01

An electrode suitable for use in an electrochemical cell is described. The electrode is composed of a porous conductive support with a bonded stack of pieces of thin corrugated nickel foil where the corrugations are oriented approximately perpendicular to the sides of the electrode and form an array of passages through the electrode. Active material such as cadmium hydroxide or nickel hydroxide is uniformly distributed within the passages. The support may comprise also a piece of thin flat nickel foil between adjacent pieces of the corrugated foil, forming a barrier between the passages formed on each side of it. Typically the corrugations in the odd corrugated layers are oriented at a small angle from the perpendicular in one direction and the corrugations in the even corrugated layers are oriented at a small angle from the perpendicular in the opposite direction.

Transverse circular-polarized Bessel beam generation by inward cylindrical aperture distribution.

PubMed

Pavone, S C; Ettorre, M; Casaletti, M; Albani, M

2016-05-16

In this paper the focusing capability of a radiating aperture implementing an inward cylindrical traveling wave tangential electric field distribution directed along a fixed polarization unit vector is investigated. In particular, it is shown that such an aperture distribution generates a non-diffractive Bessel beam whose transverse component (with respect to the normal of the radiating aperture) of the electric field takes the form of a zero-th order Bessel function. As a practical implementation of the theoretical analysis, a circular-polarized Bessel beam launcher, made by a radial parallel plate waveguide loaded with several slot pairs, arranged on a spiral pattern, is designed and optimized. The proposed launcher performance agrees with the theoretical model and exhibits an excellent polarization purity.

Synthesis and characterization of a new family of alkylammonium-chromium phosphates with worm-like morphology

NASA Astrophysics Data System (ADS)

Amghouz, Zakariae; Espina, Aránzazu; García, José R.

2015-01-01

A series of layered alkylammonium-chromium phosphates, formulated as [CnH2n+1NH3]Cr(OH)PO4 (n=2-6), has been synthesized under hydrothermal conditions. The interlayer spacing, increasing linearly with the increase of alkyl-chain length from 13.61 Å (n=2) to 21.20 Å (n=6), is occupied by a double sheet of packed amine molecules with a tilt angle of ca. 51° respect to the inorganic sheet. The powders are constituted by circular plates (diameter=0.5-3 μm, thickness= 50 nm) with central holes when n=4-6, stacked in axial direction showing worm-like morphologies. The presence of holes, and some corrugated and zig-zag fashions observed on the edge of thin circular plates are the most probable ways for the reduction of the steric tensions between organic and inorganic portions in these hybrid materials. The thermal and thermo-oxidative stability of selected compounds have been studied, including the determination of activation energy data for the decomposition processes.

Anatomy of the Corrugator Muscle.

PubMed

Hwang, Kun; Lee, Jung Hun; Lim, Hee Joong

2017-03-01

The aim of this article is to systematically review the anatomy and action of the corrugator muscle. PubMed and Scopus were searched using the terms "corrugator" AND "anatomy." Among the 60 full texts from the 145 relevant abstracts, 34 articles without sufficient content were excluded and 4 articles drawn from the reference lists were added. Among the 30 articles analyzed (721 hemifaces), 28% classified by oblique head and transverse head, and 72% did not. Corrugator originated mostly from the medial supraorbital rim (45%), followed by the medial frontal bone (31%), the medial infraorbital rim (17%), and the upper nasal process (7%). Corrugator extended through the frontalis and orbicularis oculi (41%), only the frontalis (41%), or only the orbicularis oculi (18%). Corrugator ran superolaterally (59%), or laterally (41%). Corrugators inserted mostly to the middle of the eyebrow (57%), or the medial half of the eyebrow (36%), but also to the glabella region (7%). The length of the corrugator ranged 38 to 53 mm. The transverse head (23.38 mm) was longer than the oblique head (19.75 mm). Corrugator was thicker at the medial canthus than at the midpupillary line. Corrugator was innervated by the temporal branch of the facial nerve (66%), the zygomatic branch (17%), or the angular nerve (zygomatic branch and buccal branch, 17%). Supraorbital nerve (60%) or supratrochlear nerve (40%) penetrated the corrugator. The action was depressing, pulling the eyebrow medially (91%), or with medial eyebrow elevation and lateral eyebrow depression (9%). Surgeons must keep this anatomy in mind during surgical procedures.

A modified hexagonal photonic crystal fiber for terahertz applications

NASA Astrophysics Data System (ADS)

Islam, Md. Saiful; Sultana, Jakeya; Faisal, Mohammad; Islam, Mohammad Rakibul; Dinovitser, Alex; Ng, Brian W.-H.; Abbott, Derek

2018-05-01

We present a Zeonex based highly birefringent and dispersion flattened porous core photonic crystal fiber (PC-PCF) for polarization preserving applications in the terahertz region. In order to facilitate birefringence, an array of elliptical shaped air holes surrounded by porous cladding is introduced. The porous cladding comprises circular air-holes in a modified hexagonal arrangement. The transmission characteristics of the proposed PCF are investigated using a full-vector finite element method with perfectly matched layer (PML) absorbing boundary conditions. Simulation results show a high birefringence of 0.086 and an ultra-flattened dispersion variation of ± 0.03 ps/THz/cm at optimal design parameters. Besides, a number of other important wave-guiding properties including frequency dependence of the effective material loss (EML), confinement loss, and effective area are also investigated to assess the fiber's effectiveness as a terahertz waveguide.

Spin selective filtering of polariton condensate flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gao, T.; Department of Materials Science and Technology, University of Crete, 71003 Heraklion, Crete; Antón, C.

2015-07-06

Spin-selective spatial filtering of propagating polariton condensates, using a controllable spin-dependent gating barrier, in a one-dimensional semiconductor microcavity ridge waveguide is reported. A nonresonant laser beam provides the source of propagating polaritons, while a second circularly polarized weak beam imprints a spin dependent potential barrier, which gates the polariton flow and generates polariton spin currents. A complete spin-based control over the blocked and transmitted polaritons is obtained by varying the gate polarization.

Corrugated megathrust revealed offshore from Costa Rica

NASA Astrophysics Data System (ADS)

Edwards, Joel H.; Kluesner, Jared W.; Silver, Eli A.; Brodsky, Emily E.; Brothers, Daniel S.; Bangs, Nathan L.; Kirkpatrick, James D.; Wood, Ruby; Okamoto, Kristina

2018-03-01

Exhumed faults are rough, often exhibiting topographic corrugations oriented in the direction of slip; such features are fundamental to mechanical processes that drive earthquakes and fault evolution. However, our understanding of corrugation genesis remains limited due to a lack of in situ observations at depth, especially at subducting plate boundaries. Here we present three-dimensional seismic reflection data of the Costa Rica subduction zone that image a shallow megathrust fault characterized by corrugated, and chaotic and weakly corrugated topographies. The corrugated surfaces extend from near the trench to several kilometres down-dip, exhibit high reflection amplitudes (consistent with high fluid content/pressure) and trend 11-18° oblique to subduction, suggesting 15 to 25 mm yr-1 of trench-parallel slip partitioning across the plate boundary. The corrugations form along portions of the megathrust with greater cumulative slip and may act as fluid conduits. In contrast, weakly corrugated areas occur adjacent to active plate bending faults where the megathrust has migrated up-section, forming a nascent fault surface. The variations in megathrust roughness imaged here suggest that abandonment and then reestablishment of the megathrust up-section transiently increases fault roughness. Analogous corrugations may exist along significant portions of subduction megathrusts globally.

Corrugated megathrust revealed offshore from Costa Rica

USGS Publications Warehouse

Edwards, Joel H.; Kluesner, Jared; Silver, Eli A.; Brodsky, Emily E.; Brothers, Daniel; Bangs, Nathan L.; Kirkpatrick, James D.; Wood, Ruby; Okamato, Kristina

2018-01-01

Exhumed faults are rough, often exhibiting topographic corrugations oriented in the direction of slip; such features are fundamental to mechanical processes that drive earthquakes and fault evolution. However, our understanding of corrugation genesis remains limited due to a lack of in situ observations at depth, especially at subducting plate boundaries. Here we present three-dimensional seismic reflection data of the Costa Rica subduction zone that image a shallow megathrust fault characterized by corrugated, and chaotic and weakly corrugated topographies. The corrugated surfaces extend from near the trench to several kilometres down-dip, exhibit high reflection amplitudes (consistent with high fluid content/pressure) and trend 11–18° oblique to subduction, suggesting 15 to 25 mm yr−1 of trench-parallel slip partitioning across the plate boundary. The corrugations form along portions of the megathrust with greater cumulative slip and may act as fluid conduits. In contrast, weakly corrugated areas occur adjacent to active plate bending faults where the megathrust has migrated up-section, forming a nascent fault surface. The variations in megathrust roughness imaged here suggest that abandonment and then reestablishment of the megathrust up-section transiently increases fault roughness. Analogous corrugations may exist along significant portions of subduction megathrusts globally.

Advanced designs for non-imaging submillimeter-wave Winston cone concentrators

NASA Astrophysics Data System (ADS)

Nelson, A. O.; Grossman, E. N.

2014-05-01

We describe the design and simulation of several non-imaging concentrators designed to couple submillimeter wavelength radiation from free space into highly overmoded, rectangular, WR-10 waveguide. Previous designs are altered to improve the uniformity of efficiency rather than the efficiency itself. The concentrators are intended for use as adapters between instruments using overmoded WR-10 waveguide as input or output and sources propagating through free space. Previous simulation and measurement have shown that the angular response is primarily determined by the Winston cone and is well predicted by geometric optics theory while the efficiencies are primarily determined by the transition section. Additionally, previous work has shown insensitivity to polarization, orientation and beam size. Several separate concentrator designs are studied, all of which use a Winston cone (also known as a compound parabolic concentrator) with an input diameter ranging from 4 mm to 16 mm, and "throat" diameters of less than 0.5 mm to 4 mm as the initial interface. The use of various length adiabatic circular-to-rectangular transition sections is investigated, along with the effect of an additional, 25 mm waveguide section designed to model the internal waveguide of the power meter. Adapters without a transition section and a rectangular Winston cone throat aperture and double cone configurations are also studied. Adapters are analyzed in simulation for consistent efficiency across the opening aperture.

Heat transfer enhancement and pumping power optimization using CuO-water nanofluid through rectangular corrugated pipe

NASA Astrophysics Data System (ADS)

Salehin, Musfequs; Ehsan, Mohammad Monjurul; Islam, A. K. M. Sadrul

2017-06-01

Heat transfer enhancement by corrugation in fluid domain is a popular method. The rate of improvement is more when it is used highly thermal conductive fluid as heating or cooling medium. In this present study, heat transfer augmentation was investigated numerically by implementing corrugation in the fluid domain and nanofluid as the base fluid in the turbulent forced convection regime. Finite volume method (FVM) was applied to solve the continuity, momentum and energy equations. All the numerical simulations were considered for single phase flow. A rectangle corrugated pipe with 5000 W/m2 constant heat flux subjected to the corrugated wall was considered as the fluid domain. In the range of Reynolds number 15000 to 40000, thermo-physical and hydrodynamic behavior was investigated by using CuO-water nanofluid from 1% to 5% volume fraction as the base fluid through the corrugated fluid domain. Corrugation justification was performed by changing the amplitude of the corrugation and the corrugation wave length for obtaining the increased heat transfer rate with minimum pumping power. For using CuO-water nanofluid, augmentation was also found more in the rectangle corrugated pipe both in heat transfer and pumping power requirement with the increase of Reynolds number and the volume fraction of nanofluid. For the increased pumping power, optimization of pumping power by using nanofluid was also performed for economic finding.

Investigation into the vibration of metro bogies induced by rail corrugation

NASA Astrophysics Data System (ADS)

Ling, Liang; Li, Wei; Foo, Elbert; Wu, Lei; Wen, Zefeng; Jin, Xuesong

2017-01-01

The current research of rail corrugation mainly focuses on the mechanisms of its formation and development. Compared with the root causes and development mechanisms, the wheel-rail impacts, the fatigue failure of vehicle-track parts, and the loss of ride comfort due to rail corrugation should also be taken into account. However, the influences of rail corrugation on vehicle and track vibration, and failure of vehicle and track structural parts are barely discussed in the literature. This paper presents an experimental and numerical investigation of the structural vibration of metro bogies caused by rail corrugation. Extensive experiments are conducted to investigate the effects of short-pitch rail corrugation on the vibration accelerations of metro bogies. A dynamic model of a metro vehicle coupled with a concrete track is established to study the influence of rail corrugation on the structural vibration of metro bogies. The field test results indicate that the short-pitch rail corrugation generates strong vibrations on the axle-boxes and the bogie frames, therefore, accelerates the fatigue failure of the bogie components. The numerical results show that short-pitch rail corrugation may largely reduce the fatigue life of the coil spring, and improving the damping value of the primary vertical dampers is likely to reduce the strong vibration induced by short-pitch rail corrugation. This research systematically studies the effect of rail corrugation on the vibration of metro bogies and proposes some remedies for mitigating strong vibrations of metro bogies and reducing the incidence of failure in primary coil springs, which would be helpful in developing new metro bogies and track maintenance procedures.

Interference, focusing and excitation of ultracold atoms

NASA Astrophysics Data System (ADS)

Kandes, M. C.; Fahy, B. M.; Williams, S. R.; Tally, C. H., IV; Bromley, M. W. J.

2011-05-01

One of the pressing technological challenges in atomic physics is to go orders-of-magnitude beyond the limits of photon-based optics by harnessing the wave-nature of dilute clouds of ultracold atoms. We have developed parallelised algorithms to perform numerical calculations of the Gross-Pitaevskii equation in up to three dimensions and with up to three components to simulate Bose-Einstein condensates. A wide-ranging array of the physics associated with atom optics-based systems will be presented including BEC-based Sagnac interferometry in circular waveguides, the focusing of BECs using Laguerre-Gauss beams, and the interactions between BECs and Ince-Gaussian laser beams and their potential applications. One of the pressing technological challenges in atomic physics is to go orders-of-magnitude beyond the limits of photon-based optics by harnessing the wave-nature of dilute clouds of ultracold atoms. We have developed parallelised algorithms to perform numerical calculations of the Gross-Pitaevskii equation in up to three dimensions and with up to three components to simulate Bose-Einstein condensates. A wide-ranging array of the physics associated with atom optics-based systems will be presented including BEC-based Sagnac interferometry in circular waveguides, the focusing of BECs using Laguerre-Gauss beams, and the interactions between BECs and Ince-Gaussian laser beams and their potential applications. Performed on computational resources via NSF grants PHY-0970127, CHE-0947087 and DMS-0923278.

Compact rf polarizer and its application to pulse compression systems

DOE PAGES

Franzi, Matthew; Wang, Juwen; Dolgashev, Valery; ...

2016-06-01

We present a novel method of reducing the footprint and increasing the efficiency of the modern multi-MW rf pulse compressor. This system utilizes a high power rf polarizer to couple two circular waveguide modes in quadrature to a single resonant cavity in order to replicate the response of a traditional two cavity configuration using a 4-port hybrid. The 11.424 GHz, high-Q, spherical cavity has a 5.875 cm radius and is fed by the circularly polarized signal to simultaneously excite the degenerate TE 114 modes. The overcoupled spherical cavity has a Q 0 of 9.4×10 4 and coupling factor (β) ofmore » 7.69 thus providing a loaded quality factor Q L of 1.06×10 4 with a fill time of 150 ns. Cold tests of the polarizer demonstrated good agreement with the numerical design, showing transmission of -0.05 dB and reflection back to the input rectangular WR 90 waveguide less than -40 dB over a 100 MHz bandwidth. This novel rf pulse compressor was tested at SLAC using XL-4 Klystron that provided rf power up to 32 MW and generated peak output power of 205 MW and an average of 135 MW over the discharged signal. A general network analysis of the polarizer is discussed as well as the design and high power test of the rf pulse compressor.« less

EVALUATION OF BURIED CONDUITS AS PERSONNEL SHELTERS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Albright, G.H.; LeDoux, J.C.; Mitchell, R.A.

1960-07-14

Supersedes ITR-1421. Twelve large-diameter buried conduit sections of various shapes were tested in the 60- to l49-psi overpressure region of Burst Priscilla to make an empirical determination of the degree of personnel protection afforded by commercially available steel and concrete conduits at depths of burial of 5, 7.5, and 10 feet below grade. Essentially, it was desired to assure that Repartment of Defense Class I, 100psi and comparable radiations, and Class II, 50-psi and comparable radiations, protection is afforded by use of such conduits of various configurations. Measurements were made of free-field overpressure at the ground surface above the structure;more » pressure inside the structures; acceleration of each structure; deflection of each structure; dust inside each structure; fragmentary missiles inside the concrete structures; and gamma and neutron radiation dose inside each structure. All buried conduit sections tested provided adequate Class I protection for the conditions under which the conduits were tested. Standard 8-foot concrete sewer pipe withstood 126-psi overpressure without significant damage, minor tension cracks observed; standard 10-gage corrugated-steel 8-foot circular conduit sections withstood 126- psi overpressure without significant damage; and standard 10-gage corrugated- steel cattle-pass conduits withstood 149-psi overpressure without significant damage. Durations of positive pressure were from 206 to 333 milliseconds. (auth)« less

Scanning electron microscopic study of the tegumental surface of adult Schistosoma sinensium.

PubMed

Kruatrachue, M; Upatham, E S; Sahaphong, S; Tongthong, T; Khunborivan, V

1983-12-01

The SEM study of tegumental surface of adult Schistosoma sinensium reveals that the male tegument lacks tubercles or bosses; instead it is corrugated with small pits or perforated ridges. On the dorsal surface, spines are present whose number and size progressively increase towards the posterior end of the body. In addition, there are three types of papillae interspersed among the ridges and spines. The first type of papillae has crater-like holes surrounded by a circular doughnut-shaped elevation; some are ciliated and others are non-ciliated. They are generally found on the dorsal and ventral surfaces. The second is sensory papillae which are hemispherical in shape bearing apical cilia. They are found to be concentrated around the oral sucker and on the posterior end of the worm. The third is fungiform papillae without cilia which are found on the posterior end. There are short spines present on the tegument lining the gynecophoral canal of the male worm. The tegument of the female S. sinensium is corrugated with ridges on the ventral surface. Small spines are present on the anterior portion of the dorsal surface. They become larger and increased in number towards the posterior end of the worm. The three types of papillae are present but they are much fewer and less developed than those in the male worm.

Analysis of a novel non-contacting waveguide backshort

NASA Technical Reports Server (NTRS)

Weller, T. M.; Katehi, L. P. B.; Mcgrath, William R.

1992-01-01

A new non-contacting waveguide backshort has been developed for millimeter and submillimeter wave frequencies. The design consists of a metal bar with rectangular or circular holes cut into it, which is covered with a dielectric (mylar) layer to form a snug fit with the walls of a waveguide. Hole geometries are adjusted to obtain a periodic variation of the guide impedance on the correct length scale, in order to produce efficient reflection of RF power. It is a mechanically rugged design which can be easily fabricated for frequencies from 1 to 1000 GHz and is thus a sound alternative to the miniaturization of conventional non-contacting shorts. To aid in high-frequency design, a rigorous full-wave analysis has been completed, which will allow variations of the size, number and spacing of the holes to be easily analyzed. This paper will review the backshort design and the method developed for theoretical characterization, followed by a comparison of the experimental and numerical results. Low frequency models operating from 4-6 GHz are shown to demonstrate return loss of greater than -0.2 dB over a 33 percent bandwidth. The theory is in good agreement with measured data.

Substrate Integrated Waveguide (SIW)-Based Wireless Temperature Sensor for Harsh Environments.

PubMed

Tan, Qiulin; Guo, Yanjie; Zhang, Lei; Lu, Fei; Dong, Helei; Xiong, Jijun

2018-05-03

This paper presents a new wireless sensor structure based on a substrate integrated circular waveguide (SICW) for the temperature test in harsh environments. The sensor substrate material is 99% alumina ceramic, and the SICW structure is composed of upper and lower metal plates and a series of metal cylindrical sidewall vias. A rectangular aperture antenna integrated on the surface of the SICW resonator is used for electromagnetic wave transmission between the sensor and the external antenna. The resonant frequency of the temperature sensor decreases when the temperature increases, because the relative permittivity of the alumina ceramic increases with temperature. The temperature sensor presented in this paper was tested four times at a range of 30⁻1200 °C, and a broad band coplanar waveguide (CPW)-fed antenna was used as an interrogation antenna during the test process. The resonant frequency changed from 2.371 to 2.141 GHz as the temperature varied from 30 to 1200 °C, leading to a sensitivity of 0.197 MHz/°C. The quality factor of the sensor changed from 3444.6 to 35.028 when the temperature varied from 30 to 1000 °C.

Shifting of infrared radiation using rotational raman resonances in diatomic molecular gases

DOEpatents

Kurnit, Norman A.

1980-01-01

A device for shifting the frequency of infrared radiation from a CO.sub.2 laser by stimulated Raman scattering in either H.sub.2 or D.sub.2. The device of the preferred embodiment comprises an H.sub.2 Raman laser having dichroic mirrors which are reflective for 16 .mu.m radiation and transmittive for 10 .mu.m, disposed at opposite ends of an interaction cell. The interaction cell contains a diatomic molecular gas, e.g., H.sub.2, D.sub.2, T.sub.2, HD, HT, DT and a capillary waveguide disposed within the cell. A liquid nitrogen jacket is provided around the capillary waveguide for the purpose of cooling. In another embodiment the input CO.sub.2 radiation is circularly polarized using a Fresnel rhomb .lambda./4 plate and applied to an interaction cell of much longer length for single pass operation.

User's Manual for FEMOM3DR. Version 1.0

NASA Technical Reports Server (NTRS)

Reddy, C. J.

1998-01-01

FEMoM3DR is a computer code written in FORTRAN 77 to compute radiation characteristics of antennas on 3D body using combined Finite Element Method (FEM)/Method of Moments (MoM) technique. The code is written to handle different feeding structures like coaxial line, rectangular waveguide, and circular waveguide. This code uses the tetrahedral elements, with vector edge basis functions for FEM and triangular elements with roof-top basis functions for MoM. By virtue of FEM, this code can handle any arbitrary shaped three dimensional bodies with inhomogeneous lossy materials; and due to MoM the computational domain can be terminated in any arbitrary shape. The User's Manual is written to make the user acquainted with the operation of the code. The user is assumed to be familiar with the FORTRAN 77 language and the operating environment of the computers on which the code is intended to run.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ming, Xianshun; Liu, Xinyu; Sun, Liqun

We develop the theory of all-dielectric absorbers based on temporal coupled mode theory (TCMT), with parameters extracted from eigenfrequency simulations. An infinite square array of cylindrical resonators embedded in air is investigated, and we find that it supports two eigenmodes of opposite symmetry that are each responsible for half of the total absorption. The even and odd eigenmodes are found to be the hybrid electric (EH111) and hybrid magnetic (HE111) waveguide modes of a dielectric wire of circular cross section, respectively. The geometry of the cylindrical array is shown to be useful for individual tuning of the radiative loss ratesmore » of the eigenmodes, thus permitting frequency degeneracy. Further, by specifying the resonators’ loss tangent, the material loss rate can be made to equal the radiative loss rate, thus achieving a state of degenerate critical coupling and perfect absorption. Our results are supported by S-parameter simulations, and agree well with waveguide theory.« less

A four-port vertical-coupling optical interface based on two-dimensional grating coupler

NASA Astrophysics Data System (ADS)

Zhang, Zan; Zhang, Zanyun; Huang, Beiju; Cheng, Chuantong; Gao, Tianxi; Hu, Xiaochuan; Zhang, Lin; Chen, Hongda

2016-10-01

In this work, a fiber-to-chip optical interface with four output ports is proposed. External lights irradiate vertically from single mode fiber to the center of optical interface can be coupled into silicon photonic chips and split into four siliconon- insulator (SOI) waveguides. If the light is circular polarized, the power of light will be equally split into four ports. Meanwhile, all lights travel in the four channel will be converted into TE polarization. The optical interface is based on a two-dimensional grating coupler with carefully designed duty cycle and period. Simulation results show that the coupling efficiency of each port can reach 11.6% so that the total coupling efficiency of the interface is 46.4%. And Lights coupled into four waveguides are all converted into TE polarization. Further, the optical interface has a simple grating structure allowing for easy fabrication.

Low-Loss Coupling of Quantum Cascade Lasers into Hollow-Core Waveguides with Single-Mode Output in the 3.7-7.6 μm Spectral Range.

PubMed

Patimisco, Pietro; Sampaolo, Angelo; Mihai, Laura; Giglio, Marilena; Kriesel, Jason; Sporea, Dan; Scamarcio, Gaetano; Tittel, Frank K; Spagnolo, Vincenzo

2016-04-13

We demonstrated low-loss and single-mode laser beam delivery through hollow-core waveguides (HCWs) operating in the 3.7-7.6 μm spectral range. The employed HCWs have a circular cross section with a bore diameter of 200 μm and metallic/dielectric internal coatings deposited inside a glass capillary tube. The internal coatings have been produced to enhance the spectral response of the HCWs in the range 3.5-12 µm. We demonstrated Gaussian-like outputs throughout the 4.5-7.6 µm spectral range. A quasi single-mode output beam with only small beam distortions was achieved when the wavelength was reduced to 3.7 μm. With a 15-cm-long HCW and optimized coupling conditions, we measured coupling efficiencies of >88% and transmission losses of <1 dB in the investigated infrared spectral range.

Normal modes in an overmoded circular waveguide coated with lossy material

NASA Technical Reports Server (NTRS)

Lee, C. S.; Lee, S. W.; Chuang, S. L.

1985-01-01

The normal modes in an overmoded waveguide coated with a lossy material are analyzed, particularly for their attenuation properties as a function of coating material, layer thickness, and frequency. When the coating material is not too lossy, the low-order modes are highly attenuated even with a thin layer of coating. This coated guide serves as a mode suppressor of the low-order modes, which can be particularly useful for reducing the radar cross section (RCS) of a cavity structure such as a jet inlet. When the coating material is very lossy, low-order modes fall into two distinct groups: highly and lowly attenuated modes. However, as a/lambda (a = radius of the cylinder; lambda = the free-space wavelength) increases, the separation between these two groups becomes less distinctive. The attenuation constants of most of the low-order modes become small, and decrease as a function of lambda sup 2/a sup 3.

Modeling multimode feed-horn coupled bolometers for millimeter-wave and terahertz astronomical instrumentation

NASA Astrophysics Data System (ADS)

Kalinauskaite, Eimante; Murphy, Anthony; McAuley, Ian; Trappe, Neil A.; Bracken, Colm P.; McCarthy, Darragh N.; Doherty, Stephen; Gradziel, Marcin L.; O'Sullivan, Creidhe; Maffei, Bruno; Lamarre, Jean-Michel A.; Ade, Peter A. R.; Savini, Giorgio

2016-07-01

Multimode horn antennas can be utilized as high efficiency feeds for bolometric detectors, providing increased throughput and sensitivity over single mode feeds, while also ensuring good control of beam pattern characteristics. Multimode horns were employed in the highest frequency channels of the European Space Agency Planck Telescope, and have been proposed for future terahertz instrumentation, such as SAFARI for SPICA. The radiation pattern of a multimode horn is affected by the details of the coupling of the higher order waveguide modes to the bolometer making the modeling more complicated than in the case of a single mode system. A typical cavity coupled bolometer system can be most efficiently simulated using mode matching, typically with smooth walled waveguide modes as the basis and computing an overall scattering matrix for the horn-waveguide-cavity system that includes the power absorption by the absorber. In this paper we present how to include a cavity coupled bolometer, modelled as a thin absorbing film with particular interest in investigating the cavity configuration for optimizing power absorption. As an example, the possible improvements from offsetting the axis of a cylindrically symmetric absorbing cavity from that of a circular waveguide feeding it (thus trapping more power in the cavity) are discussed. Another issue is the effect on the optical efficiency of the detectors of the presence of any gaps, through which power can escape. To model these effects required that existing in-house mode matching software, which calculates the scattering matrices for axially symmetric waveguide structures, be extended to be able to handle offset junctions and free space gaps. As part of this process the complete software code 'PySCATTER' was developed in Python. The approach can be applied to proposed terahertz systems, such as SPICASAFARI.

Superimposed coherent terahertz wave radiation from mono-energetically bunched multi-beam

DOE PAGES

Shin, Young -Min; Fermi National Accelerator Lab.

2012-06-27

Intense coherent radiation is obtained from multiple electron beams monochromatically bunched over the wide higher-order-mode (HOM) spectral band in the THz regime. The overmoded waveguide corrugated by dielectric-implanted staggered gratings superimposes evanescent waves emitted from the low energy electron beams. The dispersion and transmission simulations of the three-beam slow wave structure show that the first two fundamental modes (more » $$TE_{10}$$ and $$TE_{20}$$) are considerably suppressed ($$\\sim-50$$ dB) below the multi-beam resonating mode ($$TE_{30}$$) at the THz regime (0.8–1.24 THz). The theoretical calculations and particle-in-cell simulations show that with significantly higher interaction impedance and power growth rate radiation of the $$TE_{30}$$ mode is $$\\sim$$23 dBm and $$\\sim$$50 dBm stronger than the $$TE_{10}$$ and $$TE_{20}$$ modes around 1 THz, respectively. As a result, this highly selective HOM multi-beam interaction has potential applications for power THz sources and high intensity accelerators.« less

Curved cap corrugated sheet

NASA Technical Reports Server (NTRS)

Davis, R. C.; Bales, T. T.; Royster, D. M.; Jackson, L. R. (Inventor)

1984-01-01

The report describes a structure for a strong, lightweight corrugated sheet. The sheet is planar or curved and includes a plurality of corrugation segments, each segment being comprised of a generally U-shaped corrugation with a part-cylindrical crown and cap strip, and straight side walls and with secondary corrugations oriented at right angles to said side walls. The cap strip is bonded to the crown and the longitudinal edge of said cap strip extends beyond edge at the intersection between said crown and said side walls. The high strength relative to weight of the structure makes it desirable for use in aircraft or spacecraft.

Numerical investigation of the aerodynamic and structural characteristics of a corrugated wing

NASA Astrophysics Data System (ADS)

Hord, Kyle

Previous experimental studies on static, bio-inspired corrugated wings have shown that they produce favorable aerodynamic properties such as delayed stall compared to streamlined wings and flat plates at high Reynolds numbers (Re ≥ 4x104). The majority of studies have been carried out with scaled models of dragonfly forewings from the Aeshna Cyanea in either wind tunnels or water channels. In this thesis, the aerodynamics of a corrugated airfoil was studied using computational fluid dynamics methods at a low Reynolds number of 1000. Structural analysis was also performed using the commercial software SolidWorks 2009. The flow field is described by solving the incompressible Navier-Stokes equations on an overlapping grid using the pressure-Poisson method. The equations are discretized in space with second-order accurate central differences. Time integration is achieved through the second-order Crank-Nicolson implicit method. The complex vortex structures that form in the corrugated airfoil valleys and around the corrugated airfoil are studied in detail. Comparisons are made with experimental measurements from corrugated wings and also with simulations of a flat plate. Contrary to the studies at high Reynolds numbers, our study shows that at low Reynolds numbers the wing corrugation does not provide any aerodynamic benefit compared to a smoothed flat plate. Instead, the corrugated profile generates more pressure drag which is only partially offset by the reduction of friction drag, leading to more total drag than the flat plate. Structural analysis shows that the wing corrugation can increase the resistance to bending moments on the wing structure. A smoothed structure has to be three times thicker to provide the same stiffness. It was concluded the corrugated wing has the structural benefit to provide the same resistance to bending moments with a much reduced weight.

Configuration study of new low-loss MM (Millimeter) wave guiding structures

NASA Astrophysics Data System (ADS)

Yeh, C.

1985-11-01

The result of the research carried out at EMtec Engineering, Inc., Los Angeles, under Contract DAAG 29-84-C-0025 with the Army Research Office is discussed. The primary objective was to learn whether there exists a dielectric waveguide configuration which offers lower loss figure than a circular dielectric rod. Important evidence was found which showed that it is feasible to optimize a configuration to achieve low-loss guidance of mm waves. Future research areas are also described.

Management of in-tube projectiles using acoustic channel

NASA Astrophysics Data System (ADS)

Kostina, M. A.; Bortalevich, S. I.; Loginov, E. L.; Shinyakov, Y. A.; Sukhorukov, M. P.

2018-03-01

The article describes the method of measuring the distance from the operator's console installed outside the pipe to the in-tube projectile. A method for measuring distance in the absence of an echo signal is proposed. To do this, two identical ultrasonic locators operating at different frequencies were installed inside and outside the pipeline. The change in the duration of an acoustic pulse propagating in a circular waveguide with rigid walls is shown, which leads to a decrease in the data transfer rate.

Determination of the geometric corrugation of graphene on SiC(0001) by grazing incidence fast atom diffraction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zugarramurdi, A.; Debiossac, M.; Lunca-Popa, P.

2015-03-09

We present a grazing incidence fast atom diffraction (GIFAD) study of monolayer graphene on 6H-SiC(0001). This system shows a Moiré-like 13 × 13 superlattice above the reconstructed carbon buffer layer. The averaging property of GIFAD results in electronic and geometric corrugations that are well decoupled; the graphene honeycomb corrugation is only observed with the incident beam parallel to the zigzag direction while the geometric corrugation arising from the superlattice is revealed along the armchair direction. Full-quantum calculations of the diffraction patterns show the very high GIFAD sensitivity to the amplitude of the surface corrugation. The best agreement between the calculated and measuredmore » diffraction intensities yields a corrugation height of 0.27 ± 0.03 Å.« less

Disappointment and regret enhance corrugator reactivity in a gambling task

PubMed Central

Wu, Yin; Clark, Luke

2015-01-01

This study investigated how the corrugator and zygomaticus respond to decision outcomes (i.e., gains and losses). We used a gambling task in which participants were presented with obtained followed by non-obtained outcomes. Activity at the corrugator site was sensitive to decision outcomes, such that higher obtained losses (disappointment) and higher non-obtained gains (regret) both heightened corrugator reactivity. Activity at the zygomaticus site was not responsive to obtained or non-obtained outcomes, but did show sensitivity to emotional images in the same participants, in the form of a positive linear relationship with self-reported emotional valence. Corrugator activity was negatively related to emotional valence. The findings indicate the sensitivity of corrugator to objective decision outcomes and also counterfactual comparisons, highlighting the utility of facial electromyography in research on decision making and gambling behavior. PMID:25345723

Three-dimensional train track model for study of rail corrugation

NASA Astrophysics Data System (ADS)

Jin, X. S.; Wen, Z. F.; Wang, K. Y.; Zhou, Z. R.; Liu, Q. Y.; Li, C. H.

2006-06-01

Rail corrugation is a main factor causing the vibration and noise from the structures of railway vehicles and tracks. A calculation model is put forward to analyse the effect of rail corrugation with different depths and wavelengths on the dynamical behaviour of a passenger car and a curved track in detail. Also the evolution of initial corrugation with different wavelengths is investigated. In the numerical analysis, Kalker's non-Hertzian rolling contact theory is modified and used to calculate the frictional work density on the contact area of the wheel and rail in rolling contact. The material loss per unit area is assumed to be proportional to the frictional work density to determine the wear depth of the contact surfaces of the curved rails. The combined influences of the corrugation development and the vertical and lateral coupled dynamics of the passenger car and the curved track are taken into account. The numerical results indicate that: (1) the corrugation with high passing frequencies has a great influence on the dynamical performance of the wheelset and track, but little on the car-body and the bogie frame; (2) the deeper the corrugation depth is, the greater the influence and the rail material wear are; but the longer the corrugation wavelength is, the smaller the influence and the wear are; and (3) the initial corrugation with a fixed wavelength on the rail running surface decreases with increasing number of the passenger car passages.

Method of making porous conductive supports for electrodes. [by electroforming and stacking nickel foils

NASA Technical Reports Server (NTRS)

Schaer, G. R. (Inventor)

1973-01-01

Porous conductive supports for electrochemical cell electrodes are made by electroforming thin corrugated nickel foil, and by stacking pieces of the corrugated foil alternatively with pieces of thin flat nickel foil. Corrugations in successive corrugated pieces are oriented at different angles. Adjacent pieces of foil are bonded by heating in a hydrogen atmosphere and then cutting the stack in planes perpendicular to the foils.

Composite corrugated structures for morphing wing skin applications

NASA Astrophysics Data System (ADS)

Thill, C.; Etches, J. A.; Bond, I. P.; Potter, K. D.; Weaver, P. M.

2010-12-01

Composite corrugated structures are known for their anisotropic properties. They exhibit relatively high stiffness parallel (longitudinal) to the corrugation direction and are relatively compliant in the direction perpendicular (transverse) to the corrugation. Thus, they offer a potential solution for morphing skin panels (MSPs) in the trailing edge region of a wing as a morphing control surface. In this paper, an overview of the work carried out by the present authors over the last few years on corrugated structures for morphing skin applications is first given. The second part of the paper presents recent work on the application of corrugated sandwich structures. Panels made from multiple unit cells of corrugated sandwich structures are used as MSPs in the trailing edge region of a scaled morphing aerofoil section. The aerofoil section features an internal actuation mechanism that allows chordwise length and camber change of the trailing edge region (aft 35% chord). Wind tunnel testing was carried out to demonstrate the MSP concept but also to explore its limitations. Suggestions for improvements arising from this study were deduced, one of which includes an investigation of a segmented skin. The overall results of this study show that the MSP concept exploiting corrugated sandwich structures offers a potential solution for local morphing wing skins for low speed and small air vehicles.

Theoretical study of corrugated plates: Shear stiffness of a trapezoidally corrugated plate with discrete attachments to a rigid flange at the ends of the corrugations

NASA Technical Reports Server (NTRS)

Hsiao, C.; Libove, C.

1972-01-01

Analysis and numerical results are presented for the elastic shear stiffness of a corrugated shear web with a certain type of discrete attachments at the ends of the trough lines of the corrugations, namely point attachments to a rigid flange which interferes with the deformations of the end cross sections by preventing downward movement but permitting upward (lifting off) movement. The analysis is based on certain assumed modes of deformation of the cross sections in conjunction with the method of minimum total potential energy and the calculus of variations in order to obtain equations for the manner in which the assumed modes of deformation vary along the length of the corrugation. The numerical results are restricted to the case of equal-width crests and troughs but otherwise apply to a wide variety of geometries. They are in the form of graphs which give the overall shear stiffness as a fraction of the overall shear stiffness that could be obtained by having continuous attachment at the ends of the corrugations.

An Experimental Study on the Shear Hysteresis and Energy Dissipation of the Steel Frame with a Trapezoidal-Corrugated Steel Plate

PubMed Central

Shon, Sudeok; Yoo, Mina; Lee, Seungjae

2017-01-01

The steel frame reinforced with steel shear wall is a lateral load resisting system and has higher strength and shear performance than the concrete shear wall system. Especially, using corrugated steel plates in these shear wall systems improves out-of-plane stiffness and flexibility in the deformation along the corrugation. In this paper, a cyclic loading test of this steel frame reinforced with trapezoidal-corrugated steel plate was performed to evaluate the structural performance. The hysteresis behavior and the energy dissipation capacity of the steel frame were also compared according to the corrugated direction of the plate. For the test, one simple frame model without the wall and two frame models reinforced with the plate are considered and designed. The test results showed that the model reinforced with the corrugated steel plate had a greater accumulated energy dissipation capacity than the experimental result of the non-reinforced model. Furthermore, the energy dissipation curves of two reinforced frame models, which have different corrugated directions, produced similar results. PMID:28772624

An Experimental Study on the Shear Hysteresis and Energy Dissipation of the Steel Frame with a Trapezoidal-Corrugated Steel Plate.

PubMed

Shon, Sudeok; Yoo, Mina; Lee, Seungjae

2017-03-06

The steel frame reinforced with steel shear wall is a lateral load resisting system and has higher strength and shear performance than the concrete shear wall system. Especially, using corrugated steel plates in these shear wall systems improves out-of-plane stiffness and flexibility in the deformation along the corrugation. In this paper, a cyclic loading test of this steel frame reinforced with trapezoidal-corrugated steel plate was performed to evaluate the structural performance. The hysteresis behavior and the energy dissipation capacity of the steel frame were also compared according to the corrugated direction of the plate. For the test, one simple frame model without the wall and two frame models reinforced with the plate are considered and designed. The test results showed that the model reinforced with the corrugated steel plate had a greater accumulated energy dissipation capacity than the experimental result of the non-reinforced model. Furthermore, the energy dissipation curves of two reinforced frame models, which have different corrugated directions, produced similar results.

Direct write fabrication of waveguides and interconnects for optical printed wiring boards

NASA Astrophysics Data System (ADS)

Dingeldein, Joseph C.

Current copper based circuit technology is becoming a limiting factor in high speed data transfer applications as processors are improving at a faster rate than are developments to increase on board data transfer. One solution is to utilize optical waveguide technology to overcome these bandwidth and loss restrictions. The use of this technology virtually eliminates the heat and cross-talk loss seen in copper circuitry, while also operating at a higher bandwidth. Transitioning current fabrication techniques from small scale laboratory environments to large scale manufacturing presents significant challenges. Optical-to-electrical connections and out-of-plane coupling are significant hurdles in the advancement of optical interconnects. The main goals of this research are the development of direct write material deposition and patterning tools for the fabrication of waveguide systems on large substrates, and the development of out-of-plane coupler components compatible with standard fiber optic cabling. Combining these elements with standard printed circuit boards allows for the fabrication of fully functional optical-electrical-printed-wiring-boards (OEPWBs). A direct dispense tool was designed, assembled, and characterized for the repeatable dispensing of blanket waveguide layers over a range of thicknesses (25-225 μm), eliminating waste material and affording the ability to utilize large substrates. This tool was used to directly dispense multimode waveguide cores which required no UV definition or development. These cores had circular cross sections and were comparable in optical performance to lithographically fabricated square waveguides. Laser direct writing is a non-contact process that allows for the dynamic UV patterning of waveguide material on large substrates, eliminating the need for high resolution masks. A laser direct write tool was designed, assembled, and characterized for direct write patterning waveguides that were comparable in quality to those produced using standard lithographic practices (0.047 dB/cm loss for laser written waveguides compared to 0.043 dB/cm for lithographic waveguides). Straight waveguides, and waveguide turns were patterned at multimode and single mode sizes, and the process was characterized and documented. Support structures such as angled reflectors and vertical posts were produced, showing the versatility of the laser direct write tool. Commercially available components were implanted into the optical layer for out-of-plane routing of the optical signals. These devices featured spherical lenses on the input and output sides of a total internal reflection (TIR) mirror, as well as alignment pins compatible with standard MT design. Fully functional OEPWBs were fabricated featuring input and output out-of-plane optical signal routing with total optical losses not exceeding 10 dB. These prototypes survived thermal cycling (-40°C to 85°C) and humidity exposure (95±4% humidity), showing minimal degradation in optical performance. Operational failure occurred after environmental aging life testing at 110°C for 216 hours.

Disappointment and regret enhance corrugator reactivity in a gambling task.

PubMed

Wu, Yin; Clark, Luke

2015-04-01

This study investigated how the corrugator and zygomaticus respond to decision outcomes (i.e., gains and losses). We used a gambling task in which participants were presented with obtained followed by non-obtained outcomes. Activity at the corrugator site was sensitive to decision outcomes, such that higher obtained losses (disappointment) and higher non-obtained gains (regret) both heightened corrugator reactivity. Activity at the zygomaticus site was not responsive to obtained or non-obtained outcomes, but did show sensitivity to emotional images in the same participants, in the form of a positive linear relationship with self-reported emotional valence. Corrugator activity was negatively related to emotional valence. The findings indicate the sensitivity of corrugator to objective decision outcomes and also counterfactual comparisons, highlighting the utility of facial electromyography in research on decision making and gambling behavior. © 2014 The Authors. Psychophysiology published by Wiley Periodicals, Inc. on behalf of Society for Psychophysiological Research.

Numerical and Experimental Investigations on Mechanical Behavior of Composite Corrugated Core

NASA Astrophysics Data System (ADS)

Dayyani, Iman; Ziaei-Rad, Saeed; Salehi, Hamid

2012-06-01

Tensile and flexural characteristics of corrugated laminate panels were studied using numerical and analytical methods and compared with experimental data. Prepreg laminates of glass fiber plain woven cloth were hand-laid by use of a heat gun to ease the creation of the panel. The corrugated panels were then manufactured by using a trapezoidal machined aluminium mould. First, a series of simple tension tests were performed on standard samples to evaluate the material characteristics. Next, the corrugated panels were subjected to tensile and three-point bending tests. The force-displacement graphs were recorded. Numerical and analytical solutions were proposed to simulate the mechanical behavior of the panels. In order to model the energy dissipation due to delamination phenomenon observed in tensile tests in all members of corrugated core, plastic behavior was assigned to the whole geometry, not only to the corner regions. Contrary to the literature, it is shown that the three-stage mechanical behavior of composite corrugated core is not confined to aramid reinforced corrugated laminates and can be observed in other types such as fiber glass. The results reveal that the mechanical behavior of the core in tension is sensitive to the variation of core height. In addition, for the first time, the behavior of composite corrugated core was studied and verified in bending. Finally, the analytical and numerical results were validated by comparing them with experimental data. A good degree of correlation was observed which showed the suitability of the finite element model for predicting the mechanical behavior of corrugated laminate panels.

Optical properties of nonimaging concentrators with corrugated reflectors

NASA Astrophysics Data System (ADS)

Roennelid, Mats; Perers, Bengt; Karlsson, Bjorn

1994-09-01

A ray tracing study has been performed on the optical properties of cylindrical nonimaging concentrators with linear corrugated reflectors. The corrugations are assumed to be V-formed and to have an extension parallel to the meridian plane of the concentrators. It is shown that the acceptance angle for radiation incident in the meridian plane can be increased for moderate corrugations. This increased acceptance is balanced by a decreased acceptance of radiation from other directions. Calculations of angular acceptance for a 2X compound parabolic concentrator is presented. It is shown that the annual irradiation on a solar collector with booster reflector can be increased if corrugated reflectors are used instead of smooth reflectors.

Experimental Investigation of the Strength of Multiweb Beams with Corrugated Webs

NASA Technical Reports Server (NTRS)

Fraser, Allister F

1956-01-01

The results of an experimental investigation of the strength of multiweb beams with corrugated webs are reported. Included in the investigation were two types of connection between the web and the skin. A comparison between the structural efficiency of corrugated-web and channel-web multiweb beams is presented, and it is shown that, for a considerable range of the structural index, corrugated-web beams can be built which are structurally more efficient than channel-web beams.

Flow around a corrugated wing over the range of dragonfly flight

NASA Astrophysics Data System (ADS)

Padinjattayil, Sooraj; Agrawal, Amit

2017-11-01

The dragonfly flight is very much affected by the corrugations on their wings. A PIV based study is conducted on a rigid corrugated wing for a range of Reynolds number 300-12000 and three different angles of attack (5°-15°) to understand the mechanism of dragonfly flight better. The study revealed that the shape of the corrugation plays a key role in generating vortices. The vortices trapped in the valleys of corrugation dictates the shape of a virtual airfoil around the corrugated wing. A fluid roller bearing effect is created over the virtual airfoil when the trapped vortices merge with each other. A travelling wave produced by the moving virtual boundary around the fluid roller bearings avoids the formation of boundary layer on the virtual surface, thereby leading to high aerodynamic performance. It is found that the lift coefficient increases as the number of vortices increases on the suction surface. Also, it is shown that the partially merged co- rotating vortices give higher lift as compared to fully merged vortices. Further, the virtual airfoil formed around the corrugated wing is compared with a superhydrophobic airfoil which exhibits slip on its surface; several similarities in their flow characteristics are observed. The corrugated airfoil performs superior to the superhydrophobic airfoil in the aerodynamic efficiency due to the virtual slip caused by the travelling wave.

DIII-D Electron Cyclotron Heating System Status and Upgrades

DOE PAGES

Cengher, Mirela; Lohr, John; Gorelov, Yuri; ...

2016-06-23

The DIII-D Electron Cyclotron Heating (ECH) system consists of six 110 GHz gyrotrons with corrugated coaxial 31.75 mm waveguide transmission lines and steerable launching mirrors. The system has been gradually updated, leading to increased experimental flexibility and a high system reliability of 91% in the past year. Operationally, the gyrotrons can generate up to a total of 4.8 MW of rf power for pulses up to 5 seconds. The maximum ECH energy injected into the DIII-D is 16.6 MJ. The HE1,1 mode content is over 85% for all the lines, and the transmission coefficient is better than -1.1 dB formore » all the transmission lines, close to the theoretical value. A new depressed collector gyrotron was recently installed and was injecting up to 640 kW of power into the plasma during 2014-2015 tokamak operations. Four dual waveguide launchers, which can steer the RF beams ±20 degrees poloidally and toroidally, are used for real-time neoclassical tearing mode control and suppression. The launchers now have increased poloidal scanning speed and beam positioning accuracy of ~±2 mm at the plasma center. Two more gyrotrons are expected to be installed and operational in 2015- 2016. The first is a repaired 110 GHz, 1 MW gyrotron that had a gun failure after more than 11 years of operation at DIII-D. The second is a newly designed depressed collector tube in the 1.5 MW class, operating at 117.5 GHz, manufactured by Communications and Power Industries (CPI).« less

Incorporation of wavelength selective devices into waveguides with applications to a miniature spectrometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stallard, B. R.; Kaushik, S.; Hadley, G. R.

1996-02-01

This report pertains to a Laboratory Directed Research and Development project which was funded for FY94 and FY95. The goal was to develop building blocks for small, cheap sensors that use optical spectroscopy as a means of detecting chemical analytes. Such sensors can have an impact on a wide variety of technologies, such as: industrial process control, environmental monitors, chemical analysis in medicine, and automotive monitors. We describe work in fabricating and demonstrating a waveguide/grating device that can serve as the wavelength dispersive component in a miniature spectrometer. Also, we describe the invention and modeling of a new way tomore » construct an array of optical interference filters using sub-wavelength lithography to tune the index of refraction of a fixed Fabry-Perot cavity. Next we describe progress in more efficiently calculating the fields in grating devices. Finally we present the invention of a new type of near field optical probe, applicable to scanning microscopy or optical data storage, which is based on a circular grating constructed in a waveguide. This result diverges from the original goal of the project but is quite significant in that it promises to increase the data storage capacity of CD-ROMs by 10 times.« less

Electromagnetic study of second harmonic generation by a corrugated waveguide

NASA Astrophysics Data System (ADS)

Neviere, Michel; Popov, E.; Reinisch, Raymond

1995-09-01

When an incident plane wave with circular frequency (omega) falls on a grating coated by a layer of nonlinear material, it generates a nonlinear polarization PNL(2(omega) ) which acts as a source term and produces a second harmonic (SH) field called signal. The excitation of an electromagnetic resonance like surface plasmon or a guided wave increases the local field and thus the signal. The problem is to be able to compute and optimize the latter. We have developed a new theory which uses a coordinate transformation mapping the grating profile onto a plane. This simplifies the boundary conditions but complicates the propagation equation. Taking advantage of the psuedoperiodicity of the problem, the Fourier harmonics of the field are solution of a set of first order differential equations with constant coefficients. The resolution of this system via eigenvalue and eigenvector technique avoid numerical instabilities and lead to accurate results which agree perfectly with those found via the Rayleigh method or by the Differential method, when they work. A phenomenological approach is then developed to explain the unusual shape of the resonance lines at 2(omega) , which is based on the poles and zeros of the scattering operator S at (omega) and 2(omega) . It is shown that S(2(omega) ) presents 3 complex poles with 3 associated complex zeros. Their knowledge, plus the nonlinear reflectivity of the plane device allows predicting all the possible shapes of the 2(omega) signal as a function of angle of incidence. The phenomenological study explains an experimental result, found a few years ago, that if 2(omega) lies inside the absorption band of the guiding material instead of the transparent region, the enhanced second harmonic generation (SHG) is changed into a reduced one. It means that in the case phase matching can lead to a minimum instead of maximum. An algorithm is then proposed to maximize the signal intensity; with polyurethane as a guiding material a conversion factor of up to 40% is found when incident power is equal to 40 kW.

Theoretical study of corrugated plates: Shearing of a trapezoidally corrugated plate with trough lines permitted to curve

NASA Technical Reports Server (NTRS)

Lin, C.; Libove, C.

1971-01-01

A theoretical analysis is presented of the elastic shearing of a trapezoidally corrugated plate with discrete attachments at the ends of the corrugations. Numerical results on effective shear stiffness, stresses, and displacements are presented for selected geometries and end-attachment conditions. It is shown that the frame-like deformation of the cross-sections, which results from the absence of continuous end attachments, can lead to large transverse bending stresses and large reductions in shearing stiffness.

Method and apparatus for corrugating strips

DOEpatents

Day, Jack R.; Curtis, Charles H.

1983-01-01

The invention relates to a method and a machine for transversely corrugating a continuous strip of metallic foil. The product foil comprises a succession of alternately disposed corrugations, each defining in cross section, a major segment of a circle. The foil to be corrugated is positioned to extend within a vertical passage in the machine. The walls of the passage are heated to promote the desired deformation of the foil. Foil-deforming rollers are alternately passed obliquely across the passage to respectively engage transverse sections of the foil. The rollers and their respective section of deformed foil comprise a stacked assembly which is moved incrementally through the heated passageway. As the assembly emerges from the passageway, the rollers spill from the corrugated foil and are recovered for re-use.

Flexible cryogenic conduit

DOEpatents

Brindza, Paul Daniel; Wines, Robin Renee; Takacs, James Joseph

1999-01-01

A flexible and relatively low cost cryogenic conduit is described. The flexible cryogenic conduit of the present invention comprises a first inner corrugated tube with single braided serving, a second outer corrugated tube with single braided serving concentric with the inner corrugated tube, and arranged outwardly about the periphery of the inner corrugated tube and between the inner and outer corrugated tubes: a superinsulation layer; a one half lap layer of polyester ribbon; a one half lap layer of copper ribbon; a spirally wound refrigeration tube; a second one half lap layer of copper ribbon; a second one half lap layer of polyester ribbon; a second superinsulation layer; a third one half lap layer of polyester ribbon; and a spirally wound stretchable and compressible filament.

Dispersion analysis of leaky guided waves in fluid-loaded waveguides of generic shape.

PubMed

Mazzotti, M; Marzani, A; Bartoli, I

2014-01-01

A fully coupled 2.5D formulation is proposed to compute the dispersive parameters of waveguides with arbitrary cross-section immersed in infinite inviscid fluids. The discretization of the waveguide is performed by means of a Semi-Analytical Finite Element (SAFE) approach, whereas a 2.5D BEM formulation is used to model the impedance of the surrounding infinite fluid. The kernels of the boundary integrals contain the fundamental solutions of the space Fourier-transformed Helmholtz equation, which governs the wave propagation process in the fluid domain. Numerical difficulties related to the evaluation of singular integrals are avoided by using a regularization procedure. To improve the numerical stability of the discretized boundary integral equations for the external Helmholtz problem, the so called CHIEF method is used. The discrete wave equation results in a nonlinear eigenvalue problem in the complex axial wavenumbers that is solved at the frequencies of interest by means of a contour integral algorithm. In order to separate physical from non-physical solutions and to fulfill the requirement of holomorphicity of the dynamic stiffness matrix inside the complex wavenumber contour, the phase of the radial bulk wavenumber is uniquely defined by enforcing the Snell-Descartes law at the fluid-waveguide interface. Three numerical applications are presented. The computed dispersion curves for a circular bar immersed in oil are in agreement with those extracted using the Global Matrix Method. Novel results are presented for viscoelastic steel bars of square and L-shaped cross-section immersed in water. Copyright © 2013 Elsevier B.V. All rights reserved.

Utilizing Snap-Tite slip line pipe as a direct burial cross pipe, construction and first interim report, October, 2007.

DOT National Transportation Integrated Search

2007-10-01

The Maine Department of Transportation uses reinforced concrete, polymer coated corrugated metal, : corrugated aluminum or corrugated polyethylene for highway cross pipes. Design life for cross pipe is 50 : plus years. Repair of failed cross pipes in...

CPW-fed Circularly Polarized Slot Antenna with Small Gap and Stick-shaped Shorted Strip for UHF FRID Readers

NASA Astrophysics Data System (ADS)

Pan, Chien-Yuan; Su, Chum-Chieh; Yang, Wei-Lin

2018-04-01

A new circularly polarized (CP) slot antenna with a small gap and a stick-shaped shorted strip is presented. The proposed antenna has a sufficient bandwidth for ultrahigh frequency (UHF) radio-frequency identification (RFID) reader applications. The antenna structure consists of a rectangular slot with a small gap, a stick-shaped shorted strip and a 50 Ω coplanar waveguide (CPW) feedline with an asymmetrical ground plane. By using the stick -shaped shorted strip to disturb magnetic current distribution on the slot, the CP radiation can be generated. The measured results demonstrate that the proposed antenna can reach a 10 dB return loss impedance bandwidth of 14.1 % (894-1030 MHz) and a 3 dB axial ratio (AR) bandwidth of 6.4 % (910-970 MHz). The whole antenna size is 80 × 80 × 1.6 mm3.

Sound reflection by a resonator array in a multimode cylindrical waveguide

NASA Astrophysics Data System (ADS)

Lapin, A. D.

2012-09-01

The paper considers the problem of scattering of the mth symmetric mode by an array of Q rings of identical, closely located Helmholtz resonators joined by necks to the walls of a wide circular pipe. The distance between rings is equal to half the wavelength of this mode at frequency ω, equal or close to the eigen-frequency of the resonator ring with allowance for the connected mass and interaction of neighboring rings via inhomogeneous modes. The coefficient of reflection of the mth mode from this grating array is calculated.

OVERMODED HIGH-POWER RF MAGNETIC SWITCHES AND CIRCULATORS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tantawi, Sami

2002-08-20

We present design methodology for active rf magnetic components which are suitable for pulse compression systems of future X-band linear colliders. These components comprise an array of active elements arranged together so that the total electromagnetic field is reduced and the power handling capabilities are increased. The active element of choice is a magnetic material (garnet), which can be switched by changing a biasing magnetic field. A novel design allows these components to operate in the low loss circular waveguide mode TE{sub 01}. We describe the design methodology, the switching elements and circuits.

Low-Loss Coupling of Quantum Cascade Lasers into Hollow-Core Waveguides with Single-Mode Output in the 3.7–7.6 μm Spectral Range

PubMed Central

Patimisco, Pietro; Sampaolo, Angelo; Mihai, Laura; Giglio, Marilena; Kriesel, Jason; Sporea, Dan; Scamarcio, Gaetano; Tittel, Frank K.; Spagnolo, Vincenzo

2016-01-01

We demonstrated low-loss and single-mode laser beam delivery through hollow-core waveguides (HCWs) operating in the 3.7–7.6 μm spectral range. The employed HCWs have a circular cross section with a bore diameter of 200 μm and metallic/dielectric internal coatings deposited inside a glass capillary tube. The internal coatings have been produced to enhance the spectral response of the HCWs in the range 3.5–12 µm. We demonstrated Gaussian-like outputs throughout the 4.5–7.6 µm spectral range. A quasi single-mode output beam with only small beam distortions was achieved when the wavelength was reduced to 3.7 μm. With a 15-cm-long HCW and optimized coupling conditions, we measured coupling efficiencies of >88% and transmission losses of <1 dB in the investigated infrared spectral range. PMID:27089343

Degenerate critical coupling in all-dielectric metasurface absorbers

DOE PAGES

Ming, Xianshun; Liu, Xinyu; Sun, Liqun; ...

2017-09-27

We develop the theory of all-dielectric absorbers based on temporal coupled mode theory (TCMT), with parameters extracted from eigenfrequency simulations. An infinite square array of cylindrical resonators embedded in air is investigated, and we find that it supports two eigenmodes of opposite symmetry that are each responsible for half of the total absorption. The even and odd eigenmodes are found to be the hybrid electric (EH111) and hybrid magnetic (HE111) waveguide modes of a dielectric wire of circular cross section, respectively. The geometry of the cylindrical array is shown to be useful for individual tuning of the radiative loss ratesmore » of the eigenmodes, thus permitting frequency degeneracy. Further, by specifying the resonators’ loss tangent, the material loss rate can be made to equal the radiative loss rate, thus achieving a state of degenerate critical coupling and perfect absorption. Our results are supported by S-parameter simulations, and agree well with waveguide theory.« less

Nonlinear finite element modeling of corrugated board

Treesearch

A. C. Gilchrist; J. C. Suhling; T. J. Urbanik

1999-01-01

In this research, an investigation on the mechanical behavior of corrugated board has been performed using finite element analysis. Numerical finite element models for corrugated board geometries have been created and executed. Both geometric (large deformation) and material nonlinearities were included in the models. The analyses were performed using the commercial...

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dalvit, Diego; Messina, Riccardo; Maia Neto, Paulo

We develop the scattering approach for the dispersive force on a ground state atom on top of a corrugated surface. We present explicit results to first order in the corrugation amplitude. A variety of analytical results are derived in different limiting cases, including the van der Waals and Casimir-Polder regimes. We compute numerically the exact first-order dispersive potential for arbitrary separation distances and corrugation wavelengths, for a Rubidium atom on top of a silicon or gold corrugated surface. We consider in detail the correction to the proximity force approximation, and present a very simple approximation algorithm for computing the potential.

Method and apparatus for corrugating strips

DOEpatents

Day, J.R.; Curtis, C.H.

1981-10-27

The invention relates to a method and a machine for transversely corrugating a continuous strip of metallic foil. The product foil comprises a succession of alternately disposed corrugations, each defining in a cross section, a major segment of a circle. The foil to be corrugated is positioned to extend within a vertical passage in the machine. The walls of the passage are heated to promote the desired deformation of the foil. Foil-deforming rollers are alternately passed obliquely across the passage to respectively engage transverse sections of the foil. The rollers and their respective section of deformed foil comprise a stacked assembly which is moved incrementally through the heated passageway. As the assembly emerges from the passageway, the rollers spill from the corrugated foil and are recovered for re-use.

Theoretical prediction on corrugated sandwich panels under bending loads

NASA Astrophysics Data System (ADS)

Shu, Chengfu; Hou, Shujuan

2018-05-01

In this paper, an aluminum corrugated sandwich panel with triangular core under bending loads was investigated. Firstly, the equivalent material parameters of the triangular corrugated core layer, which could be considered as an orthotropic panel, were obtained by using Castigliano's theorem and equivalent homogeneous model. Secondly, contributions of the corrugated core layer and two face panels were both considered to compute the equivalent material parameters of the whole structure through the classical lamination theory, and these equivalent material parameters were compared with finite element analysis solutions. Then, based on the Mindlin orthotropic plate theory, this study obtain the closed-form solutions of the displacement for a corrugated sandwich panel under bending loads in specified boundary conditions, and parameters study and comparison by the finite element method were executed simultaneously.

A modal approach based on perfectly matched layers for the forced response of elastic open waveguides

NASA Astrophysics Data System (ADS)

Gallezot, M.; Treyssède, F.; Laguerre, L.

2018-03-01

This paper investigates the computation of the forced response of elastic open waveguides with a numerical modal approach based on perfectly matched layers (PML). With a PML of infinite thickness, the solution can theoretically be expanded as a discrete sum of trapped modes, a discrete sum of leaky modes and a continuous sum of radiation modes related to the PML branch cuts. Yet with numerical methods (e.g. finite elements), the waveguide cross-section is discretized and the PML must be truncated to a finite thickness. This truncation transforms the continuous sum into a discrete set of PML modes. To guarantee the uniqueness of the numerical solution of the forced response problem, an orthogonality relationship is proposed. This relationship is applicable to any type of modes (trapped, leaky and PML modes) and hence allows the numerical solution to be expanded on a discrete sum in a convenient manner. This also leads to an expression for the modal excitability valid for leaky modes. The physical relevance of each type of mode for the solution is clarified through two numerical test cases, a homogeneous medium and a circular bar waveguide example, excited by a point source. The former is favourably compared to a transient analytical solution, showing that PML modes reassemble the bulk wave contribution in a homogeneous medium. The latter shows that the PML mode contribution yields the long-term diffraction phenomenon whereas the leaky mode contribution prevails closer to the source. The leaky mode contribution is shown to remain accurate even with a relatively small PML thickness, hence reducing the computational cost. This is of particular interest for solving three-dimensional waveguide problems, involving two-dimensional cross-sections of arbitrary shapes. Such a problem is handled in a third numerical example by considering a buried square bar.

Atom chips in the real world: the effects of wire corrugation

NASA Astrophysics Data System (ADS)

Schumm, T.; Estève, J.; Figl, C.; Trebbia, J.-B.; Aussibal, C.; Nguyen, H.; Mailly, D.; Bouchoule, I.; Westbrook, C. I.; Aspect, A.

2005-02-01

We present a detailed model describing the effects of wire corrugation on the trapping potential experienced by a cloud of atoms above a current carrying micro wire. We calculate the distortion of the current distribution due to corrugation and then derive the corresponding roughness in the magnetic field above the wire. Scaling laws are derived for the roughness as a function of height above a ribbon shaped wire. We also present experimental data on micro wire traps using cold atoms which complement some previously published measurements [CITE] and which demonstrate that wire corrugation can satisfactorily explain our observations of atom cloud fragmentation above electroplated gold wires. Finally, we present measurements of the corrugation of new wires fabricated by electron beam lithography and evaporation of gold. These wires appear to be substantially smoother than electroplated wires.

Baseline Receiver Concept for a Next Generation Very Large Array

NASA Astrophysics Data System (ADS)

Srikanth, Sivasankaran; Wes Grammer, Silver Sturgis, Rob Selina

2018-01-01

The Next Generation Very Large Array (ngVLA) is envisioned to be an interferometric array with 10 times the effective collecting area and spatial resolution as the current VLA, operating over a frequency range of 1.2-116 GHz. Achieving these goals will require 214 antennas of nominal 18m diameter, on baselines of 300km. Maximizing sensitivity for each receiver band, while also minimizing the overall operating cost are the primary design goals. Therefore, receivers and feeds will be cryogenically cooled, with multiple bands integrated into a common cryostat to the greatest extent possible. Using feed designs that yield broad bandwidths and high aperture efficiencies are key to meeting these goals.The proposed receiver configuration will be implemented as six independent bands, each with its own feed. The upper five bands will be integrated into a single compact cryostat, while the lowest-frequency band occupies a second cryostat of similar volume and mass. The lowest-band feed is cooled to 80K, while all other feeds are cooled to 20K.For optimum performance at the higher frequencies, waveguide-bandwidth (~1.66:1) receivers are proposed to cover 12.6 – 50.5 GHz and 70 – 116 GHz in four separate bands, integrated into a single cryostat. Excellent LNA noise performance is readily achievable, and using waveguide throughout the signal chain reduces losses and their associated noise contributions, without adding undue size or weight. An axially-corrugated conical feed horn with wide flare angle (~50degree half-angle), based on a design by G. Cortes and L. Baker, is being considered for these receivers.For continuous coverage between 1.2 – 12.6 GHz, waveguide or even octave-bandwidth receivers are not cost-effective, given the > 10:1 frequency range. For these bands, wideband (3.25:1) receivers mated to a Caltech-designed quad-ridge feed horn (QRFH) are proposed. These feeds are highly compact, and cryogenically cooled to reduce losses ahead of the LNAs. Aperture efficiency and LNA noise temperature may be somewhat less than optimum: however, there would be significant cost savings by effectively halving the number of receivers and cryostats required per antenna.

Microwave blackbodies for spaceborne receivers

NASA Technical Reports Server (NTRS)

Stacey, J. M.

1985-01-01

The properties of microwave blackbody targets are explained as they apply to the calibration of spaceborne receivers. Also described are several practicable, blackbody targets used to test and calibrate receivers in the laboratory and in the thermal vacuum chamber. Problems with the precision and the accuracy of blackbody targets, and blackbody target design concepts that overcome some of the accuracy limitations present in existing target designs, are presented. The principle of the Brewster angle blackbody target is described where the blackbody is applied as a fixed-temperature test target in the laboratory and as a variable-temperature target in the thermal vacuum chamber. The reflectivity of a Brewster angle target is measured in the laboratory. From this measurement, the emissivity of the target is calculated. Radiatively cooled thermal suspensions are discussed as the coolants of blackbody targets and waveguide terminations that function as calibration devices in spaceborne receivers. Examples are given for the design of radiatively cooled thermal suspensions. Corrugated-horn antennas used to observe the cosmic background and to provide a cold-calibration source for spaceborne receivers are described.

Near-Infrared and Optical Beam Steering and Frequency Splitting in Air-Holes-in-Silicon Inverse Photonic Crystals.

PubMed

Tasolamprou, Anna C; Koschny, Thomas; Kafesaki, Maria; Soukoulis, Costas M

2017-11-15

We present the design of a dielectric inverse photonic crystal structure that couples line-defect waveguide propagating modes into highly directional beams of controllable directionality. The structure utilizes a triangular lattice made of air holes drilled in an infinitely thick Si slab, and it is designed for operation in the near-infrared and optical regime. The structure operation is based on the excitation and manipulation of dark dielectric surface states, in particular on the tailoring of the dark states' coupling to outgoing radiation. This coupling is achieved with the use of properly designed external corrugations. The structure adapts and matches modes that travel through the photonic crystal and the free space. Moreover it facilitates the steering of the outgoing waves, is found to generate well-defined, spatially and spectrally isolated beams, and may serve as a frequency splitting component designed for operation in the near-infrared regime and in particular the telecom optical wavelength band. The design complies with the state-of-the-art Si nanofabrication technology and can be directly scaled for operation in the optical regime.

Near-Infrared and Optical Beam Steering and Frequency Splitting in Air-Holes-in-Silicon Inverse Photonic Crystals

PubMed Central

2017-01-01

We present the design of a dielectric inverse photonic crystal structure that couples line-defect waveguide propagating modes into highly directional beams of controllable directionality. The structure utilizes a triangular lattice made of air holes drilled in an infinitely thick Si slab, and it is designed for operation in the near-infrared and optical regime. The structure operation is based on the excitation and manipulation of dark dielectric surface states, in particular on the tailoring of the dark states’ coupling to outgoing radiation. This coupling is achieved with the use of properly designed external corrugations. The structure adapts and matches modes that travel through the photonic crystal and the free space. Moreover it facilitates the steering of the outgoing waves, is found to generate well-defined, spatially and spectrally isolated beams, and may serve as a frequency splitting component designed for operation in the near-infrared regime and in particular the telecom optical wavelength band. The design complies with the state-of-the-art Si nanofabrication technology and can be directly scaled for operation in the optical regime. PMID:29541653

Backward spoof surface wave in plasmonic metamaterial of ultrathin metallic structure.

PubMed

Liu, Xiaoyong; Feng, Yijun; Zhu, Bo; Zhao, Junming; Jiang, Tian

2016-02-04

Backward wave with anti-parallel phase and group velocities is one of the basic properties associated with negative refraction and sub-diffraction image that have attracted considerable interest in the context of photonic metamaterials. It has been predicted theoretically that some plasmonic structures can also support backward wave propagation of surface plasmon polaritons (SPPs), however direct experimental demonstration has not been reported, to the best of our knowledge. In this paper, a specially designed plasmonic metamaterial of corrugated metallic strip has been proposed that can support backward spoof SPP wave propagation. The dispersion analysis, the full electromagnetic field simulation and the transmission measurement of the plasmonic metamaterial waveguide have clearly validated the backward wave propagation with dispersion relation possessing negative slope and opposite directions of group and phase velocities. As a further verification and application, a contra-directional coupler is designed and tested that can route the microwave signal to opposite terminals at different operating frequencies, indicating new application opportunities of plasmonic metamaterial in integrated functional devices and circuits for microwave and terahertz radiation.

Adhesive in the buckling failure of corrugated fiberboard : a finite element investigation

Treesearch

Adeeb A. Rahman; Said M. Abubakr

1998-01-01

This research study proposed to include the glue material in a finite element model that represents the actual geometry and material properties of a corrugated fiberboard. The model is a detailed representation of the different components of the structure (adhesive, linerboard, medium) to perform buckling analysis of corrugated structures under compressive loads. The...

Dynamic tension testing equipment for paperboard and corrugated fiberboard

Treesearch

W. D. Godshall

1965-01-01

The objective of this work was to develop a method, the testing equipment, and the instrumentation with which dynamic stress-strain information may be obtained for paperboards and built-up corrugated fiberboards as used in corrugated fiberboard containers. Much information is available on the properties of these materials when subjected to static or low rates of...

A CPW-fed circular wide-slot UWB antenna with wide tunable and flexible reconfigurable dual notch bands.

PubMed

Li, Yingsong; Li, Wenxing; Ye, Qiubo

2013-01-01

A coplanar waveguide (CPW)-fed circular slot antenna with wide tunable dual band-notched function and frequency reconfigurable characteristic is designed, and its performance is verified experimentally for ultra-wideband (UWB) communication applications. The dual band-notched function is achieved by using a T-shaped stepped impedance resonator (T-SIR) inserted inside the circular ring radiation patch and by etching a parallel stub loaded resonator (PSLR) in the CPW transmission line, while the wide tunable bands can be implemented by adjusting the dimensions of the T-SIR and the PSLR. The notch band reconfigurable characteristic is realized by integrating three switches into the T-SIR and the PSLR. The numerical and experimental results show that the proposed antenna has a wide bandwidth ranging from 2.7 GHz to 12 GHz with voltage standing wave ratio (VSWR) less than 2, except for the two notch bands operating at 3.8-5.9 GHz and 7.7-9.2 GHz, respectively. In addition, the proposed antenna has been optimized to a compact size and can provide omnidirectional radiation patterns, which are suitable for UWB communication applications.

A CPW-Fed Circular Wide-Slot UWB Antenna with Wide Tunable and Flexible Reconfigurable Dual Notch Bands

PubMed Central

Li, Yingsong; Li, Wenxing; Ye, Qiubo

2013-01-01

A coplanar waveguide (CPW)-fed circular slot antenna with wide tunable dual band-notched function and frequency reconfigurable characteristic is designed, and its performance is verified experimentally for ultra-wideband (UWB) communication applications. The dual band-notched function is achieved by using a T-shaped stepped impedance resonator (T-SIR) inserted inside the circular ring radiation patch and by etching a parallel stub loaded resonator (PSLR) in the CPW transmission line, while the wide tunable bands can be implemented by adjusting the dimensions of the T-SIR and the PSLR. The notch band reconfigurable characteristic is realized by integrating three switches into the T-SIR and the PSLR. The numerical and experimental results show that the proposed antenna has a wide bandwidth ranging from 2.7 GHz to 12 GHz with voltage standing wave ratio (VSWR) less than 2, except for the two notch bands operating at 3.8–5.9 GHz and 7.7–9.2 GHz, respectively. In addition, the proposed antenna has been optimized to a compact size and can provide omnidirectional radiation patterns, which are suitable for UWB communication applications. PMID:24222733

Design of optimum rear passivated submicron Al corrugation in very thin textured silicon back-contact back-junction solar cell for absorption enhancement up to near-infrared region

NASA Astrophysics Data System (ADS)

Abdullah, Mohd Faizol; Hashim, Abdul Manaf

2018-01-01

The optical reflection and absorption in a very thin textured back-contact back-junction silicon (Si) solar cell are investigated. The introduction of nanotexturing on front Si surface has significantly increased the absorption in the ultraviolet (UV)-visible region with a low reflection of below 0.05. The introduction of rear surface corrugation formed by a combination of SiO2-Al has successfully enhanced the absorption up to near-infrared (NI) region. The optimum crest width, periodicity, and trough depth of corrugation are derived, which lead to high absorption up to 0.97. The internal reflection and scattering that occur near the plasmonic Al corrugation are contributing to the local maximum electric field intensity in both transverse magnetic (TM) and transverse electric (TE) modes. Since there is no perpendicular electric component in TE mode, a coupling of electric field within a corrugation trough is not observed but is only observed in TM mode. On 10-μm-thick Si, the application of Si nanocones (NCs) and optimized rear Al corrugation results in 56% improvement in photogenerated current, Jsc, compared to the reference flat Si. Thinning down the Si to only 2 μm severely limits the Jsc. Our optimized Al corrugation manages to compensate net 9% and 7% Jsc loss in 2-μm Si in respect to 10-μm-thick Si for the model with and without front Si NCs. The results seem to reveal the optimum design of rear Al corrugation for the absorption enhancement from UV up to NI wavelength region.

Simplified dragonfly airfoil aerodynamics at Reynolds numbers below 8000

NASA Astrophysics Data System (ADS)

Levy, David-Elie; Seifert, Avraham

2009-07-01

Effective aerodynamics at Reynolds numbers lower than 10 000 is of great technological interest and a fundamental scientific challenge. The current study covers a Reynolds number range of 2000-8000. At these Reynolds numbers, natural insect flight could provide inspiration for technology development. Insect wings are commonly characterized by corrugated airfoils. In particular, the airfoil of the dragonfly, which is able to glide, can be used for two-dimensional aerodynamic study of fixed rigid wings. In this study, a simplified dragonfly airfoil is numerically analyzed in a steady free-stream flow. The aerodynamic performance (such as mean and fluctuating lift and drag), are first compared to a "traditional" low Reynolds number airfoil: the Eppler-E61. The numerical results demonstrate superior performances of the corrugated airfoil. A series of low-speed wind and water tunnel experiments were performed on the corrugated airfoil, to validate the numerical results. The findings indicate quantitative agreement with the mean wake velocity profiles and shedding frequencies while validating the two dimensionality of the flow. A flow physics numerical study was performed in order to understand the underlying mechanism of corrugated airfoils at these Reynolds numbers. Airfoil shapes based on the flow field characteristics of the corrugated airfoil were built and analyzed. Their performances were compared to those of the corrugated airfoil, stressing the advantages of the latter. It was found that the flow which separates from the corrugations and forms spanwise vortices intermittently reattaches to the aft-upper arc region of the airfoil. This mechanism is responsible for the relatively low intensity of the vortices in the airfoil wake, reducing the drag and increasing the flight performances of this kind of corrugated airfoil as compared to traditional low Reynolds number airfoils such as the Eppler E-61.

Flexural strengthening of Reinforced Concrete (RC) Beams Retrofitted with Corrugated Glass Fiber Reinforced Polymer (GFRP) Laminates

NASA Astrophysics Data System (ADS)

Aravind, N.; Samanta, Amiya K.; Roy, Dilip Kr. Singha; Thanikal, Joseph V.

2015-01-01

Strengthening the structural members of old buildings using advanced materials is a contemporary research in the field of repairs and rehabilitation. Many researchers used plain Glass Fiber Reinforced Polymer (GFRP) sheets for strengthening Reinforced Concrete (RC) beams. In this research work, rectangular corrugated GFRP laminates were used for strengthening RC beams to achieve higher flexural strength and load carrying capacity. Type and dimensions of corrugated profile were selected based on preliminary study using ANSYS software. A total of twenty one beams were tested to study the load carrying capacity of control specimens and beams strengthened with plain sheets and corrugated laminates using epoxy resin. This paper presents the experimental and theoretical study on flexural strengthening of Reinforced Concrete (RC) beams using corrugated GFRP laminates and the results are compared. Mathematical models were developed based on the experimental data and then the models were validated.

The Monster Sound Pipe

ERIC Educational Resources Information Center

Ruiz, Michael J.; Perkins, James

2017-01-01

Producing a deep bass tone by striking a large 3 m (10 ft) flexible corrugated drainage pipe immediately grabs student attention. The fundamental pitch of the corrugated tube is found to be a semitone lower than a non-corrugated smooth pipe of the same length. A video (https://youtu.be/FU7a9d7N60Y) of the demonstration is included, which…

A corrugated perfect magnetic conductor surface supporting spoof surface magnon polaritons.

PubMed

Liu, Liang-liang; Li, Zhuo; Gu, Chang-qing; Ning, Ping-ping; Xu, Bing-zheng; Niu, Zhen-yi; Zhao, Yong-jiu

2014-05-05

In this paper, we demonstrate that spoof surface magnon polaritons (SSMPs) can propagate along a corrugated perfect magnetic conductor (PMC) surface. From duality theorem, the existence of surface electromagnetic modes on corrugated PMC surfaces are manifest to be transverse electric (TE) mode compared with the transverse magnetic (TM) mode of spoof surface plasmon plaritons (SSPPs) excited on corrugated perfect electric conductor surfaces. Theoretical deduction through modal expansion method and simulation results clearly verify that SSMPs share the same dispersion relationship with the SSPPs. It is worth noting that this metamaterial will have more similar properties and potential applications as the SSPPs in large number of areas.

Research on a 170 GHz, 2 MW coaxial cavity gyrotron with inner-outer corrugation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hou, Shenyong, E-mail: houshenyong@sohu.com; Yu, Sheng; Li, Hongfu

2015-03-15

In this paper, a coaxial cavity gyrotron with inner-outer corrugation is researched. The electron kineto-equations and the first order transmission line equations of the gyrotron are derived from Lorentz force equation and the transmission line theory, respectively. And then, a 2 MW, 170 GHz coaxial cavity gyrotron with inner-outer corrugation is designed. By means of numerical calculation, the beam-wave interaction of the coaxial cavity gyrotron with inner-outer corrugation is investigated. Results show that the efficient and the outpower of the gyrotron are 42.3% and 2.38 MW, respectively.

Non-binding conductor load bearing roller for a gas-insulated transmission line having a corrugated outer conductor

DOEpatents

Fischer, William H.

1984-01-01

A gas-insulated transmission line includes a corrugated outer conductor, an inner conductor disposed within and insulated from the outer conductor by means of support insulators and an insulating gas, and a non-binding transport device for supporting and permitting movement of the inner conductor/insulating support assembly axially along the corrugated outer conductor without radial displacement and for moving without binding along corrugations of any slope less than vertical. The transport device includes two movable contacts, such as skids or rollers, supported on a common pivot lever, the pivot lever being rotatably disposed about a pivot lever axis, which pivot lever axis is in turn disposed on the periphery of a support insulator or particle trap if one is used. The movable contacts are separated axially a distance equal to the axial distance between the peaks and valleys of the corrugations of the outer conductor and separated radially a distance equal to the radial distance between the peaks and valleys of the corrugations of the outer conductor. The transport device has the pivot lever axis disposed parallel to the motion of travel of the inner conductor/insulating support assembly.

Curved grating fabrication techniques for concentric-circle grating, surface-emitting semiconductor lasers

NASA Technical Reports Server (NTRS)

Jordan, Rebecca H.; King, Oliver; Wicks, Gary W.; Hall, Dennis G.; Anderson, Erik H.; Rooks, Michael J.

1993-01-01

We describe the fabrication and operational characteristics of a novel, surface-emitting semiconductor laser that makes use of a concentric-circle grating to both define its resonant cavity and to provide surface emission. A properly fabricated circular grating causes the laser to operate in radially inward- and outward-going circular waves in the waveguide, thus, introducing the circular symmetry needed for the laser to emit a beam with a circular cross-section. The basic circular-grating-resonator concept can be implemented in any materials system; an AlGaAs/GaAs graded-index, separate confinement heterostructure (GRINSCH), single-quantum-well (SQW) semiconductor laser, grown by molecular beam epitaxy (MBE), was used for the experiments discussed here. Each concentric-circle grating was fabricated on the surface of the AlGaAs/GaAs semiconductor laser. The circular pattern was first defined by electron-beam (e-beam) lithography in a layer of polymethylmethacrylate (PMMA) and subsequently etched into the semiconductor surface using chemically-assisted (chlorine) ion-beam etching (CAIBE). We consider issues that affect the fabrication and quality of the gratings. These issues include grating design requirements, data representation of the grating pattern, and e-beam scan method. We provide examples of how these techniques can be implemented and their impact on the resulting laser performance. A comparison is made of the results obtained using two fundamentally different electron-beam writing systems. Circular gratings with period lambda = 0.25 microns and overall diameters ranging from 80 microns to 500 microns were fabricated. We also report our successful demonstration of an optically pumped, concentric-circle grating, semiconductor laser that emits a beam with a far-field divergence angle that is less than one degree. The emission spectrum is quite narrow (less than 0.1 nm) and is centered at wavelength lambda = 0.8175 microns.

Corrugated QWIP for Tactical Army Applications

DTIC Science & Technology

2008-12-01

1 CORRUGATED QWIP FOR TACTICAL ARMY APPLICATIONS David. P. Forrai, Darrel W. Endres L-3 Communications Cincinnati Electronics Mason, OH 45040...Directorate (NVESD) have been developing the corrugated quantum well infrared photodetector (C- QWIP ) technology for applications in tactical LWIR...imaging. The C- QWIP was invented at ARL and shows promise to overcome some of the limitations in commercially available QWIPs . The C- QWIP uses micro

Nanophononics at low temperature: manipulating heat at the nanoscale

NASA Astrophysics Data System (ADS)

Bourgeois, Olivier

2014-03-01

Nanophononics is an emerging field of condensed matter that deals with transport of thermal phonons at small length scales. When the section of a waveguide becomes smaller than the mean free path or the phonon wavelength, heat transfer are strongly affected. Here, I will present the results we obtained by ultra- sensitive measurements of thermal conductance of suspended nano-objects (nanowires and membranes) using the 3 ω method. This experimental set-up allows the measurement of power as small as a fraction of femtoWatt (10-15 Watt). These experiments show that the concepts of mean free path and dominant wavelength are crucial to understand the phonon thermal transport below 10K. The phonon transport, at this temperature, is well described by the Casimir-Ziman model used here to treat the data. The contribution of the thermal contact between a nanowire and the heat bath has been estimated to be close to one, thanks to the fact that the nanowire are made out of monolithic single crystal. Strong reduction of thermal conductance has been obtained in serpentine nanowire where the transport of ballistic phonons is blocked. Moreover, in corrugated silicon nanowire, we showed that the corrugations induce significant backscattering of phonon that severely reduces the mean free path, beating in some cases, the Casimir limit. These experiments demonstrate the ability to manipulate ballistic phonons by adjusting the geometry of thermal conductors, and hence manipulate heat transfer. Finally, the use of these new concepts of engineering ballistic phonons at the nanoscale allows considering the development of new nanostructured materials for thermoelectrics at room temperature, opening exciting prospects for future applications in the energy recovery. J.-S. Heron, T. Fournier, N. Mingo and O. Bourgeois, Nano Letters 9, 1861 (2009). J-S. Heron, C. Bera, T. Fournier, N. Mingo, and O. Bourgeois, Phys. Rev. B 82, 155458 (2010). C. Blanc, A. Rajabpour, S. Volz, T. Fournier, and O. Bourgeois, Appl. Phys. Lett. 103, 043109 (2013). EU Merging Project grant Agreement No. 309150.

The non-storm time corrugated upper thermosphere: What is beyond MSIS?

NASA Astrophysics Data System (ADS)

Liu, Huixin; Thayer, Jeff; Zhang, Yongliang; Lee, Woo Kyoung

2017-06-01

Observations in the recent decade have revealed many thermospheric density corrugations/perturbations under nonstorm conditions (Kp < 2). They are generally not captured by empirical models like Mass Spectrometer Incoherent Scatter (MSIS) but are operationally important for long-term orbital evolution of Low Earth Orbiting satellites and theoretically for coupling processes in the atmosphere-ionosphere system. We review these density corrugations by classifying them into three types which are driven respectively by the lower atmosphere, ionosphere, and solar wind/magnetosphere. Model capabilities in capturing these features are discussed. A summary table of these corrugations is included to provide a quick guide on their magnitudes, occurring latitude, local time, and season.

Corrugated metal-coated tapered tip for scanning near-field optical microscope.

PubMed

Antosiewicz, Tomasz J; Szoplik, Tomasz

2007-08-20

This paper addresses an important issue of light throughput of a metal-coated tapered tip for scanning near-field microscope (SNOM). Corrugations of the interface between the fiber core and metal coating in the form of parallel grooves of different profiles etched in the core considerably increase the energy throughput. In 2D FDTD simulations in the Cartesian coordinates we calculate near-field light emitted from such tips. For a certain wavelength range total intensity of forward emission from the corrugated tip is 10 times stronger than that from a classical tapered tip. When realized in practice the idea of corrugated tip may lead up to twice better resolution of SNOM.

The monster sound pipe

NASA Astrophysics Data System (ADS)

Ruiz, Michael J.; Perkins, James

2017-03-01

Producing a deep bass tone by striking a large 3 m (10 ft) flexible corrugated drainage pipe immediately grabs student attention. The fundamental pitch of the corrugated tube is found to be a semitone lower than a non-corrugated smooth pipe of the same length. A video (https://youtu.be/FU7a9d7N60Y) of the demonstration is included, which illustrates how an Internet keyboard can be used to estimate the fundamental pitches of each pipe. Since both pipes have similar end corrections, the pitch discrepancy between the smooth pipe and drainage tube is due to the corrugations, which lower the speed of sound inside the flexible tube, dropping its pitch a semitone.

Impact-damaged graphite-thermoplastic trapezoidal-corrugation sandwich and semi-sandwich panels

NASA Technical Reports Server (NTRS)

Jegley, D.

1993-01-01

The results of a study of the effects of impact damage on compression-loaded trapezoidal-corrugation sandwich and semi-sandwich graphite-thermoplastic panels are presented. Sandwich panels with two identical face sheets and a trapezoidal corrugated core between them, and semi-sandwich panels with a corrugation attached to a single skin are considered in this study. Panels were designed, fabricated and tested. The panels were made using the manufacturing process of thermoforming, a less-commonly used technique for fabricating composite parts. Experimental results for unimpacted control panels and panels subjected to impact damage prior to loading are presented. Little work can be found in the literature about these configurations of thermoformed panels.

Mechanical behavior of Kenaf/Epoxy corrugated sandwich structures

NASA Astrophysics Data System (ADS)

Bakhori, S.; Hassan, M. Z.; Daud, Y.; Sarip, S.; Rahman, N.; Ismail, Z.; Aziz, S. A.

2015-12-01

This study presents the response of kenaf/epoxy corrugated sandwich structure during quasi-static test. Force-displacements curves have been deducted to determine the deformation pattern and collapse behavior of the structure. Kenaf/epoxy sandwich structures skins fabricated by using hand layup technique and the corrugated core were moulded by using steel mould. Different thicknesses of corrugated core web with two sizes of kenaf fibers were used. The corrugated core is then bonded with the skins by using poly-epoxy resin and has been cut into different number of cells. The specimens then tested under tensile and compression at different constant speeds until the specimens fully crushed. Tensile tests data showed the structure can be considered brittle when it breaking point strain, ε less than 0.025. In compression test, the specimens fail due to dominated by stress concentration that initiated by prior cracks. Also, the specimens with more number of cells and thicker core web have higher strength and the ability to absorb higher energy.

Spacecraft wall design for increased protection against penetration by space debris impacts

NASA Technical Reports Server (NTRS)

Schonberg, William P.; Tullos, Randy J.

1990-01-01

All orbiting spacecraft are susceptible to impacts by meteoroids and pieces of orbital space debris. These impacts occur at extremely high speeds and can damage flight-critical systems, which can in turn lead to catastrophic failure of the spacecraft. The design of a spacecraft for a long-duration mission into the meteoroid and space debris environment must include adequate protection against perforation of pressurized components by such impacts. This paper presents the results of an investigation into the perforation resistance of dual-wall structural systems fabricated with monolithic bumper plates and with corrugated bumper plates of equal weight. A comparative analysis of the impact damage in dual-wall systems with corrugated bumper specimens and that in dual-wall specimens with monolithic bumpers of similar weight is performed to determine the advantages and disadvantages of employing corrugated bumpers in structural wall systems for long-duration spacecraft. The analysis indicates that a significant increase in perforation protection can be achieved if a monolithic bumper is replaced by a corrugated bumper of equal weight. The parameters of the corrugations in the corrugated bumper plates are optimized in a manner that minimizes the potential for the creation of ricochet debris in the event of an oblique hypervelocity impact. Several design examples using the optimization scheme are presented and discussed.

Efficiency enhancement of flexible OLEDs by using nano-corrugated substrates and conformal Ag transparent anodes

NASA Astrophysics Data System (ADS)

Wang, Li; Luo, Yu; Feng, Xueming; Pei, Yuechen; Lu, Bingheng; Cheng, Shenggui

2018-05-01

In flexible OLEDs (FOLEDs), the traditional ITO anode has disadvantages such as refractive-index mismatches among substrate and other functional layers, leads to light loss of nearly 80%, meanwhile, its brittle nature and lack in raw materials hinder its further applications. We investigated an efficient FOLED using a semi-transparent silver (Ag) anode, whereas the device was built on a nano-corrugated flexible polycarbonate (PC) substrate prepared by thermal nanoimprint lithography. The corrugations were well preserved on each layer of the device, both the micro-cavity effect and surface plasmon polariton (SPP) modes of light loss were effectively suppressed. As a result, the current efficiency of the FOLED using a conformal corrugated Ag anode enhanced by 100% compared with a planar Ag anode device, and enhanced by 13% with conventional ITO device. In addition, owing to the quasi-periodical arrangements of the corrugations, the device achieved broad spectra and Lambertian angular emission. The Ag anode significantly improved the bending properties of the OLED as compared to the conventional ITO device, leading to a longer lifetime in practical use. The proposed manufacturing strategy will be useful for fabricating nano corrugations on plastic substrate of FOLED in a cost-effective and convenient manner.

Reversal of neuromuscular block with sugammadex: a comparison of the corrugator supercilii and adductor pollicis muscles in a randomized dose-response study.

PubMed

Yamamoto, S; Yamamoto, Y; Kitajima, O; Maeda, T; Suzuki, T

2015-08-01

Neuromuscular monitoring using the corrugator supercilii muscle is associated with a number of challenges. The aim of this study was to assess reversal of a rocuronium-induced neuromuscular blockade with sugammadex according to monitoring either using the corrugator supercilii muscle or the adductor pollicis muscle. We hypothesized that a larger dose of sugammadex would be required to obtain a train-of-four (TOF) ratio of 1.0 with the corrugator supercilii muscle than with the adductor pollicis muscle. Forty patients aged 20-60 years and 40 patients aged ≥ 70 years were enrolled. After induction of anesthesia, we recorded the corrugator supercilii muscle response to facial nerve stimulation and the adductor pollicis muscle response to ulnar nerve stimulation using acceleromyography. All patients received 1 mg/kg rocuronium. When the first twitch (T1) of TOF recovered to 10% of control values at the corrugator supercilii, rocuronium infusion was commenced to maintain a T1 of 10% of the control at the corrugator supercilii. Immediately after discontinuation of rocuronium infusion, 2 mg/kg or 4 mg/kg of sugammadex was administered. The time for recovery to a TOF ratio of 1.0 and the number of patients not reaching a TOF ratio of 1.0 by 5 min at each dose and muscle was recorded. When neuromuscular block at the corrugator supercilii was maintained at a T1 of 10% of control, that at the adductor pollicis was deep (post-tetanic count ≤ 5). Sugammadex 4 mg/kg completely antagonized neuromuscular block at both muscles within 5 min. The time to a TOF ratio of 1.0 at the adductor pollicis was significantly longer in the group ≥ 70 years than the group 20-60 years (mean (SD): 178 (42.8) s vs. 120 (9.4) s, P < 0.0001). In contrast, 2 mg/kg sugammadex reversed neuromuscular blockade at the corrugator supercilii but not at the adductor pollicis, with 10 patients in the group 20-60 years and 8 patients in the group ≥ 70 years requiring an additional sugammadex (P < 0.05 vs. 4 mg/kg sugammadex). Sugammadex 4 mg/kg was required to reverse a moderate rocuronium-induced neuromuscular block when the corrugator supercilii muscle is used for monitoring. © 2015 The Acta Anaesthesiologica Scandinavica Foundation. Published by John Wiley & Sons Ltd.

Design, fabrication and evaluation of chalcogenide glass Luneburg lenses for LiNbO3 integrated optical devices

NASA Technical Reports Server (NTRS)

Wood, V. E.; Busch, J. R.; Verber, C. M.

1982-01-01

Optical waveguide Luneburg lenses of arsenic trisulfide glass are described. The lenses are formed by thermal evaporation of As2S3 through suitably placed masks onto the surface of LiNbO3:Ti indiffused waveguides. The lenses are designed for input apertures up to 1 cm and for speeds of f/5 or better. They are designed to focus the TM sub 0 guided mode of a beam of wavelength, external to the guide, of 633 nm. The refractive index of the As2S3 films and the changes induced in the refractive index by exposure to short wavelength light were measured. Some correlation between film thickness and optical properties was noted. The short wavelength photosensitivity was used to shorten the lens focal length from the as deposited value. Lenses of rectangular shape, as viewed from above the guide, as well as conventional circular Luneburg lenses, were made. Measurements made on the lenses include thickness profile, general optical quality, focal length, quality of focal spot, and effect of ultraviolet irradiation on optical properties.

Dual circularly polarized broadside beam antenna based on metasurfaces

NASA Astrophysics Data System (ADS)

Tellechea, A.; Caminita, F.; Martini, E.; Ederra, I.; Teniente, J.; Iriarte, J. C.; Gonzalo, R.; Maci, S.

2018-02-01

Design details of a Ku band metasurface (MTS) antenna with dual circularly polarized (CP) broadside radiation is shown in this work. By means of the surface impedance tensor modulation, synchronized propagation of two transversal magnetic (TM) and transverse electric (TE) surface waves (SWs) is ensured in the structure, which contribute to the radiation in broadside direction by the generation of a CP leaky wave. The structure is implemented by elliptical subwavelength metallic elements with a cross-shaped aperture in the center, printed on top of a thin substrate with high permittivity (AD1000 with a thickness of λ0/17). For the experimental validation, the MTS prototype has been excited employing an orthomode transducer composed by a metallic stepped septum inside an air-filled waveguide. Two orthogonal TE11 modes excited with ±90° phase shift in the feed couple with the TM and TE SWs supported by the MTS and generate RHCP or LHCP broadside beam. Experimental results are compared with the simulation predictions. Finally, conclusions are drawn.

Stylus type MEMS texture sensor covered with corrugated diaphragm

NASA Astrophysics Data System (ADS)

Tsukamoto, Takashiro; Asao, Hideaki; Tanaka, Shuji

2017-09-01

In this paper, a stylus type MEMS texture sensor covered with a corrugated palylene diaphragm, which prevent debris from jamming into the sensor without significant degradation of sensitivity and bandwidth, was reported. A new fabrication process using a lost-foil method to make the corrugated diaphragm on a 3-axis piezoresistive force sensor at wafer level has been developed. The texture sensor could detect the surface microstructure as small as about 10 \

[Progressive damage monitoring of corrugated composite skins by the FBG spectral characteristics].

PubMed

Zhang, Yong; Wang, Bang-Feng; Lu, Ji-Yun; Gu, Li-Li; Su, Yong-Gang

2014-03-01

In the present paper, a method of monitoring progressive damage of composite structures by non-uniform fiber Bragg grating (FBG) reflection spectrum is proposed. Due to the finite element analysis of corrugated composite skins specimens, the failure process under tensile load and corresponding critical failure loads of corrugated composite skin was predicated. Then, the non-uniform reflection spectrum of FBG sensor could be reconstructed and the corresponding relationship between layer failure order sequence of corrugated composite skin and FBG sensor reflection spectrums was acquired. A monitoring system based on FBG non-uniform reflection spectrum, which can be used to monitor progressive damage of corrugated composite skins, was built. The corrugated composite skins were stretched under this FBG non-uniform reflection spectrum monitoring system. The results indicate that real-time spectrums acquired by FBG non-uniform reflection spectrum monitoring system show the same trend with the reconstruction reflection spectrums. The maximum error between the corresponding failure and the predictive value is 8.6%, which proves the feasibility of using FBG sensor to monitor progressive damage of corrugated composite skin. In this method, the real-time changes in the FBG non-uniform reflection spectrum within the scope of failure were acquired through the way of monitoring and predicating, and at the same time, the progressive damage extent and layer failure sequence of corru- gated composite skin was estimated, and without destroying the structure of the specimen, the method is easy and simple to operate. The measurement and transmission section of the system are completely composed of optical fiber, which provides new ideas and experimental reference for the field of dynamic monitoring of smart skin.

Contact-angle hysteresis on periodic microtextured surfaces: Strongly corrugated liquid interfaces.

PubMed

Iliev, Stanimir; Pesheva, Nina

2016-06-01

We study numerically the shapes of a liquid meniscus in contact with ultrahydrophobic pillar surfaces in Cassie's wetting regime, when the surface is covered with identical and periodically distributed micropillars. Using the full capillary model we obtain the advancing and the receding equilibrium meniscus shapes when the cross-sections of the pillars are both of square and circular shapes, for a broad interval of pillar concentrations. The bending of the liquid interface in the area between the pillars is studied in the framework of the full capillary model and compared to the results of the heterogeneous approximation model. The contact angle hysteresis is obtained when the three-phase contact line is located on one row (block case) or several rows (kink case) of pillars. It is found that the contact angle hysteresis is proportional to the line fraction of the contact line on pillars tops in the block case and to the surface fraction for pillar concentrations 0.1-0.5 in the kink case. The contact angle hysteresis does not depend on the shape (circular or square) of the pillars cross-section. The expression for the proportionality of the receding contact angle to the line fraction [Raj et al., Langmuir 28, 15777 (2012)LANGD50743-746310.1021/la303070s] in the case of block depinning is theoretically substantiated through the capillary force, acting on the solid plate at the meniscus contact line.

Curved Waveguide Based Nuclear Fission for Small, Lightweight Reactors

NASA Technical Reports Server (NTRS)

Coker, Robert; Putnam, Gabriel

2012-01-01

The focus of the presented work is on the creation of a system of grazing incidence, supermirror waveguides for the capture and reuse of fission sourced neutrons. Within research reactors, neutron guides are a well known tool for directing neutrons from the confined and hazardous central core to a more accessible testing or measurement location. Typical neutron guides have rectangular, hollow cross sections, which are crafted as thin, mirrored waveguides plated with metal (commonly nickel). Under glancing angles with incoming neutrons, these waveguides can achieve nearly lossless transport of neutrons to distant instruments. Furthermore, recent developments have created supermirror surfaces which can accommodate neutron grazing angles up to four times as steep as nickel. A completed system will form an enclosing ring or spherical resonator system to a coupled neutron source for the purpose of capturing and reusing free neutrons to sustain and/or accelerate fission. While grazing incidence mirrors are a known method of directing and safely using neutrons, no method has been disclosed for capture and reuse of neutrons or sustainment of fission using a circular waveguide structure. The presented work is in the process of fabricating a functional, highly curved, neutron supermirror using known methods of Ni-Ti layering capable of achieving incident reflection angles up to four times steeper than nickel alone. Parallel work is analytically investigating future geometries, mirror compositions, and sources for enabling sustained fission with applicability to the propulsion and energy goals of NASA and other agencies. Should research into this concept prove feasible, it would lead to development of a high energy density, low mass power source potentially capable of sustaining fission with a fraction of the standard critical mass for a given material and a broadening of feasible materials due to reduced rates of release, absorption, and non-fission for neutrons. This advance could be applied to direct propulsion through guided fission products or as a secondary energy source for high impulse electric propulsion. It would help meet national needs for highly efficient energy sources with limited dependence on fossil fuels or conflict materials, and it would improve the use of low grade fissile materials which would help reduce national stockpiles and waste.

Core design for use with precision composite reflectors

NASA Technical Reports Server (NTRS)

Porter, Christopher C. (Inventor); Jacoy, Paul J. (Inventor); Schmitigal, Wesley P. (Inventor)

1992-01-01

A uniformly flexible core, and method for manufacturing the same, is disclosed for use between the face plates of a sandwich structure. The core is made of a plurality of thin corrugated strips, the corrugations being defined by a plurality of peaks and valleys connected to one another by a plurality of diagonal risers. The corrugated strips are orthogonally criss-crossed to form the core. The core is particularly suitable for use with high accuracy spherically curved sandwich structures because undesirable stresses in the curved face plates are minimized due to the uniform flexibility characteristics of the core in both the X and Y directions. The core is self venting because of the open geometry of the corrugations. The core can be made from any suitable composite, metal, or polymer. Thermal expansion problems in sandwich structures may be minimized by making the core from the same composite materials that are selected in the manufacture of the curved face plates because of their low coefficients of thermal expansion. Where the strips are made of a composite material, the core may be constructed by first cutting an already cured corrugated sheet into a plurality of corrugated strips and then secondarily bonding the strips to one another or, alternatively, by lying a plurality of uncured strips orthogonally over one another in a suitable jig and then curing and bonding the entire plurality of strips to one another in a single operation.

Conductor load bearing roller for a gas-insulated transmission line having a corrugated outer conductor

DOEpatents

Fischer, William H.; Yoon, Kue H.

1984-04-10

A gas-insulated transmission line includes a corrugated outer conductor, an inner conductor disposed within and insulated from the outer conductor by means of support insulators and an insulating gas, and a transport device for supporting and permitting movement of the inner conductor/insulating support assembly axially along the corrugated outer conductor without radial displacement. The transport device includes two movable contacts, such as skids or rollers, supported on a common pivot lever, the pivot lever being rotatably disposed about a pivot lever axis, which pivot lever axis is in turn disposed on the periphery of a support insulator or particle trap if one is used. The movable contacts are separated axially a distance equal to the axial distance between the peaks and valleys of the corrugations of the outer conductor and separated radially a distance equal to the radial distance between the peaks and valleys of the corrugations of the outer conductor. The transport device has the pivot lever axis disposed perpendicular to the direction of travel of the inner conductor/insulating support assembly.

Design of Ultra-Wideband Tapered Slot Antenna by Using Binomial Transformer with Corrugation

NASA Astrophysics Data System (ADS)

Chareonsiri, Yosita; Thaiwirot, Wanwisa; Akkaraekthalin, Prayoot

2017-05-01

In this paper, the tapered slot antenna (TSA) with corrugation is proposed for UWB applications. The multi-section binomial transformer is used to design taper profile of the proposed TSA that does not involve using time consuming optimization. A step-by-step procedure for synthesis of the step impedance values related with step slot widths of taper profile is presented. The smooth taper can be achieved by fitting the smoothing curve to the entire step slot. The design of TSA based on this method yields results with a quite flat gain and wide impedance bandwidth covering UWB spectrum from 3.1 GHz to 10.6 GHz. To further improve the radiation characteristics, the corrugation is added on the both edges of the proposed TSA. The effects of different corrugation shapes on the improvement of antenna gain and front-to-back ratio (F-to-B ratio) are investigated. To demonstrate the validity of the design, the prototypes of TSA without and with corrugation are fabricated and measured. The results show good agreement between simulation and measurement.

Timoshenko-Type Theory in the Stability Analysis of Corrugated Cylindrical Shells

NASA Astrophysics Data System (ADS)

Semenyuk, N. P.; Neskhodovskaya, N. A.

2002-06-01

A technique is proposed for stability analysis of longitudinally corrugated shells under axial compression. The technique employs the equations of the Timoshenko-type nonlinear theory of shells. The geometrical parameters of shells are specified on discrete set of points and are approximated by segments of Fourier series. Infinite systems of homogeneous algebraic equations are derived from a variational equation written in displacements to determine the critical loads and buckling modes. Specific types of corrugated isotropic metal and fiberglass shells are considered. The calculated results are compared with those obtained within the framework of the classical theory of shells. It is shown that the Timoshenko-type theory extends significantly the possibility of exact allowance for the geometrical parameters and material properties of corrugated shells compared with Kirchhoff-Love theory.

Corrugated walls analysis in microchannels through porous medium under Electromagnetohydrodynamic (EMHD) effects

NASA Astrophysics Data System (ADS)

Rashid, M.; Shahzadi, Iqra; Nadeem, S.

2018-06-01

This study looks for corrugated walls analysis in microchannels through porous medium under the impact of Electromagnetohydrodynamic (EMHD) effects. The incompressible and electrically conducting second grade fluid is considered between the two slit microparallel plates. The periodic sinusoidal waves are described for the small amplitude either in phase or out of phase for the corrugations of two wavy walls. By employing mathematical computation, we evaluated the corrugation effects on velocity for EMHD flow. By using perturbation technique, we investigated the analytical solutions of the velocity and volume flow rate. The influence of all parameters on velocity and the mean velocity profiles have been analyzed through graphs. The important conclusion from the analysis is that the small value of amplitude ratio parameter reduces the unobvious wave effect on the velocity.

Reverberatory screen for a radiant burner

DOEpatents

Gray, Paul E.

1999-01-01

The present invention relates to porous mat gas fired radiant burner panels utilizing improved reverberatory screens. The purpose of these screens is to boost the overall radiant output of the burner relative to a burner using no screen and the same fuel-air flow rates. In one embodiment, the reverberatory screen is fabricated from ceramic composite material, which can withstand higher operating temperatures than its metallic equivalent. In another embodiment the reverberatory screen is corrugated. The corrugations add stiffness which helps to resist creep and thermally induced distortions due to temperature or thermal expansion coefficient differences. As an added benefit, it has been unexpectedly discovered that the corrugations further increase the radiant efficiency of the burner. In a preferred embodiment, the reverberatory screen is both corrugated and made from ceramic composite material.

Elastic constants for superplastically formed/diffusion-bonded corrugated sandwich core

NASA Technical Reports Server (NTRS)

Ko, W. L.

1980-01-01

Formulas and associated graphs for evaluating the effective elastic constants for a superplastically formed/diffusion bonded (SPF/DB) corrugated sandwich core, are presented. A comparison of structural stiffnesses of the sandwich core and a honeycomb core under conditions of equal sandwich core density was made. The stiffness in the thickness direction of the optimum SPF/DB corrugated core (that is, triangular truss core) is lower than that of the honeycomb core, and that the former has higher transverse shear stiffness than the latter.

A method for modeling discontinuities in a microwave coaxial transmission line

NASA Technical Reports Server (NTRS)

Otoshi, T. Y.

1992-01-01

A method for modeling discontinuities in a coaxial transmission line is presented. The methodology involves the use of a nonlinear least-squares fit program to optimize the fit between theoretical data (from the model) and experimental data. When this method was applied to modeling discontinuities in a slightly damaged Galileo spacecraft S-band (2.295-GHz) antenna cable, excellent agreement between theory and experiment was obtained over a frequency range of 1.70-2.85 GHz. The same technique can be applied for diagnostics and locating unknown discontinuities in other types of microwave transmission lines, such as rectangular, circular, and beam waveguides.

A method for modeling discontinuities in a microwave coaxial transmission line

NASA Astrophysics Data System (ADS)

Otoshi, T. Y.

1992-08-01

A method for modeling discontinuities in a coaxial transmission line is presented. The methodology involves the use of a nonlinear least-squares fit program to optimize the fit between theoretical data (from the model) and experimental data. When this method was applied to modeling discontinuities in a slightly damaged Galileo spacecraft S-band (2.295-GHz) antenna cable, excellent agreement between theory and experiment was obtained over a frequency range of 1.70-2.85 GHz. The same technique can be applied for diagnostics and locating unknown discontinuities in other types of microwave transmission lines, such as rectangular, circular, and beam waveguides.

Design and measurement of a direct-drillable smooth walled feedhorn at 1.2 THz for the next generation BLASTPol experiment

NASA Astrophysics Data System (ADS)

Groppi, Christopher E.; Mauskopf, P. M.; Ade, P. A. R.; Underhill, M.

2016-07-01

We present the design and measurement of a direct-drillable smooth walled feedhorn for the Next Generation BLASTPol balloon experiment. Custom milling cutters were obtained commercially and used to fabricate a two feedhorn structures with UG-387 flanges, each with 0.5mm section of circular waveguide, which were then mated back to back. These horns were then tested at Cardiff University using a rotation stage scanner to measure E and H plane cuts of the horn. The measurements show good agreement in both the beam FWHM and sidelobes as compared to HFSS simulations of the horn.

Intrinsic hybrid modes in a corrugated conical horn

NASA Astrophysics Data System (ADS)

Dendane, A.; Arnold, J. M.

1988-08-01

Computational requirements for the generation of intrinsic modes in a nonseparable waveguide geometry requiring a full vector field description with anistropic impedance boundaries were derived. Good agreement is shown between computed and measured radiation patterns in copolar and crosspolar configurations. This agreement establishes that the intrinsic mode correctly accounts for the local normal mode conversion which takes place along the horn in a conventional mode coupling scheme, at least for cone semiangles up to 15 deg. The advantage of the intrinsic mode formulation over the conventional mode-coupling theory is that, to construct a single intrinsic mode throughout the horn, only one local normal mode field is required at each cross section, whereas mode conversion from the HE11 mode would require all the HE1n modes to be known at each cross section. The intrinsic mode accounts also for fields which would appear as backward modes in coupled-mode theory. A complete coupled-mode theory solution requires the inversion of a large matrix at each cross section, whereas the intrinsic mode can be constructed explicitly using a simple Fourier-like integral; the perturbation solution of Dragone (1977) is difficult to make rigorous.

Near-Infrared and Optical Beam Steering and Frequency Splitting in Air-Holes-in-Silicon Inverse Photonic Crystals

DOE PAGES

Tasolamprou, Anna C.; Koschny, Thomas; Kafesaki, Maria; ...

2017-09-28

Here, we present the design of a dielectric inverse photonic crystal structure that couples line-defect waveguide propagating modes into highly directional beams of controllable directionality. The structure utilizes a triangular lattice made of air holes drilled in an infinitely thick Si slab, and it is designed for operation in the near-infrared and optical regime. The structure operation is based on the excitation and manipulation of dark dielectric surface states, in particular on the tailoring of the dark states’ coupling to outgoing radiation. This coupling is achieved with the use of properly designed external corrugations. The structure adapts and matches modesmore » that travel through the photonic crystal and the free space. Moreover it facilitates the steering of the outgoing waves, is found to generate well-defined, spatially and spectrally isolated beams, and may serve as a frequency splitting component designed for operation in the near-infrared regime and in particular the telecom optical wavelength band. The design complies with the state-of-the-art Si nanofabrication technology and can be directly scaled for operation in the optical regime.« less

Near-Infrared and Optical Beam Steering and Frequency Splitting in Air-Holes-in-Silicon Inverse Photonic Crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tasolamprou, Anna C.; Koschny, Thomas; Kafesaki, Maria

Here, we present the design of a dielectric inverse photonic crystal structure that couples line-defect waveguide propagating modes into highly directional beams of controllable directionality. The structure utilizes a triangular lattice made of air holes drilled in an infinitely thick Si slab, and it is designed for operation in the near-infrared and optical regime. The structure operation is based on the excitation and manipulation of dark dielectric surface states, in particular on the tailoring of the dark states’ coupling to outgoing radiation. This coupling is achieved with the use of properly designed external corrugations. The structure adapts and matches modesmore » that travel through the photonic crystal and the free space. Moreover it facilitates the steering of the outgoing waves, is found to generate well-defined, spatially and spectrally isolated beams, and may serve as a frequency splitting component designed for operation in the near-infrared regime and in particular the telecom optical wavelength band. The design complies with the state-of-the-art Si nanofabrication technology and can be directly scaled for operation in the optical regime.« less

Microwave Radiometers from 0.6 to 22 GHz for Juno, a Polar Orbiter around Jupiter

NASA Technical Reports Server (NTRS)

P. Pingree; Janssen, M.; Oswald, J.; Brown, S.; Chen, J.; Hurst, K.; Kitiyakara, A.; Maiwald, F.; Smith, S.

2008-01-01

A compact radiometer instrument is under development at JPL for Juno, the next NASA New Frontiers mission, scheduled to launch in 2011. This instrument is called the MWR (MicroWave Radiometer), and its purpose is to measure the thermal emission from Jupiter's atmosphere at selected frequencies from 0.6 to 22 GHz. The objective is to measure the distributions and abundances of water and ammonia in Jupiter's atmosphere, with the goal of understanding the previously unobserved dynamics of the subcloud atmosphere, and to discriminate among models for planetary formation in our solar system. The MWR instrument is currently being developed to address these science questions for the Juno mission. As part of a deep space mission aboard a solar-powered spacecraft, MWR is designed to be compact, lightweight, and low power. The entire MWR instrument consists of six individual radiometer channels with approximately 4% bandwidth at 0.6, 1.25,2.6,5.2, 10,22 GHz operating in direct detection mode. Each radiometer channel has up to 80 dB of gain with a noise figure of several dB. The highest frequency channel uses a corrugated feedhorn and waveguide transmission lines, whereas all other channels use highly phase stable coaxial cables and either patch array or waveguide slot array antennas. Slot waveguide array antennas were chosen for the low loss at the next three highest frequencies and patch array antennas were implemented due to the mass constraint at the two lowest frequencies. The six radiometer channels receive their voltage supplies and control lines from an electronics unit that also provides the instrument communication interface to the Juno spacecraft. For calibration purposes each receiver has integrated noise diodes, a Dicke switch, and temperature sensors near each component that contributes to the noise figure. In addition, multiple sensors will be placed along the RF transmission lines and the antennas in order to measure temperature gradients. All antennas and RF transmission lines must withstand low temperatures and the harsh radiation environment surrounding Jupiter; the receivers and control electronics are protected by a radiation-shielding enclosure on the Juno spacecraft that also provides for a benign and stable operating temperature environment. This paper will focus on the concept of the MWR instrument and will present results of one breadboard receiver channel.

1. Elkmont vehicle bridge at Elkmont Campground, galvanized corrugated arch. ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

1. Elkmont vehicle bridge at Elkmont Campground, galvanized corrugated arch. - Great Smoky Mountains National Park Roads & Bridges, Elkmont Vehicle Bridge, Spanning Little River at Elkmont Campground, Gatlinburg, Sevier County, TN

Use of a corrugated beam pipe as a passive deflector for bunch length measurements

NASA Astrophysics Data System (ADS)

Seok, Jimin; Chung, Moses; Kang, Heung-Sik; Min, Chang-Ki; Na, Donghyun

2018-02-01

We report the experimental demonstration of bunch length measurements using a corrugated metallic beam pipe as a passive deflector. The corrugated beam pipe has been adopted for reducing longitudinal chirping after the bunch compressors in several XFEL facilities worldwide. In the meantime, there have been attempts to measure the electron bunch's longitudinal current profile using the dipole wakefields generated in the corrugated pipe. Nevertheless, the bunch shape reconstructed from the nonlinearly deflected beam suffers from significant distortion, particularly near the head of the bunch. In this paper, we introduce an iterative process to improve the resolution of the bunch shape reconstruction. The astra and elegant simulations have been performed for pencil beam and cigar beam cases, in order to verify the effectiveness of the reconstruction process. To overcome the undesirable effects of transverse beam spreads, a measurement scheme involving both the corrugated beam pipe and the spectrometer magnet has been employed, both of which do not require a dedicated (and likely very expensive) rf system. A proof-of-principle experiment was carried out at Pohang Accelerator Laboratory (PAL) Injector Test Facility (ITF), and its results are discussed together with a comparison with the rf deflector measurement.

Wakefield computations for a corrugated pipe as a beam dechirper for FEL applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ng, C. K.; Bane, K. L.F.

A beam “dechirper” based on a corrugated, metallic vacuum chamber has been proposed recently to cancel residual energy chirp in a beam before it enters the undulator in a linac-based X-ray FEL. Rather than the round geometry that was originally proposed, we consider a pipe composed of two parallel plates with corrugations. The advantage is that the strength of the wake effect can be tuned by adjusting the separation of the plates. The separation of the plates is on the order of millimeters, and the corrugations are fractions of a millimeter in size. The dechirper needs to be meters longmore » in order to provide sufficient longitudinal wakefield to cancel the beam chirp. Considerable computation resources are required to determine accurately the wakefield for such a long structure with small corrugation gaps. Combining the moving window technique and parallel computing using multiple processors, the time domain module in the parallel finite-element electromagnetic suite ACE3P allows efficient determination of the wakefield through convergence studies. In this paper, we will calculate the longitudinal, dipole and quadrupole wakefields for the dechirper and compare the results with those of analytical and field matching approaches.« less

Pressure and heating-rate distributions on a corrugated surface in a supersonic turbulent boundary layer

NASA Technical Reports Server (NTRS)

Sawyer, J. W.

1977-01-01

Drag and heating rates on wavy surfaces typical of current corrugated plate designs for thermal protection systems were determined experimentally. Pressure-distribution, heating-rate, and oil-flow tests were conducted in the Langley Unitary Plan wind tunnel at Mach numbers of 2.4 and 4.5 with the corrugated surface exposed to both thick and thin turbulent boundary layers. Tests were conducted with the corrugations at cross-flow angles from 0 deg to 90 deg to the flow. Results show that for cross-flow angles of 30 deg or less, the pressure drag coefficients are less than the local flat-plate skin-friction coefficients and are not significantly affected by Mach number, Reynolds number, or boundary-layer thickness over the ranges investigated. For cross-flow angles greater than 30 deg, the drag coefficients increase significantly with cross-flow angle and moderately with Reynolds number. Increasing the Mach number causes a significant reduction in the pressure drag. The average and peak heating penalties due to the corrugated surface are small for cross-flow angles of 10 deg or less but are significantly higher for the larger cross-flow angles.

Novel wideband microwave polarization network using a fully-reconfigurable photonic waveguide interleaver with a two-ring resonator-assisted asymmetric Mach-Zehnder structure.

PubMed

Zhuang, Leimeng; Beeker, Willem; Leinse, Arne; Heideman, René; van Dijk, Paulus; Roeloffzen, Chris

2013-02-11

We propose and demonstrate a novel wideband microwave photonic polarization network for dual linear-polarized antennas. The polarization network is based on a waveguide-implemented fully-reconfigurable optical interleaver using a two-ring resonator-assisted asymmetric Mach-Zehnder structure. For microwave photonic signal processing, this structure is able to serve as a wideband 2 × 2 RF coupler with reconfigurable complex coefficients, and therefore can be used as a polarization network for wideband antennas. Such a device can equip the antennas with not only the polarization rotation capability for linear-polarization signals but also the capability to operate with and tune between two opposite circular polarizations. Operating together with a particular modulation scheme, the device is also able to serve for simultaneous feeding of dual-polarization signals. These photonic-implemented RF functionalities can be applied to wideband antenna systems to perform agile polarization manipulations and tracking operations. An example of such a interleaver has been realized in TriPleX waveguide technology, which was designed with a free spectral range of 20 GHz and a mask footprint of smaller than 1 × 1 cm. Using the realized device, the reconfigurable complex coefficients of the polarization network were demonstrated with a continuous bandwidth from 2 to 8 GHz and an in-band phase ripple of smaller than 5 degree. The waveguide structure of the device allows it to be further integrated with other functional building blocks of a photonic integrated circuit to realize on-chip, complex microwave photonic processors. Of particular interest, it can be included in an optical beamformer for phased array antennas, so that simultaneous wideband beam and polarization trackings can be achieved photonically. To our knowledge, this is the first-time on-chip demonstration of an integrated microwave photonic polarization network for dual linear-polarized antennas.

7. DETAIL VIEW UNDER BRIDGE OF CORRUGATED STEEL, BEAMS, RODS, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

7. DETAIL VIEW UNDER BRIDGE OF CORRUGATED STEEL, BEAMS, RODS, AND ABUTMENT - Price River Bridge, Spanning Price River, 760 North Street in Carbonville, 1 mile northwest of Price, Carbonville, Carbon County, UT

Corrugated steel culvert pipe deterioration : final report, August 2009.

DOT National Transportation Integrated Search

2009-08-01

This research provides the basis for developing a comprehensive plan for inspection, cleaning, condition assessment and : prediction of remaining service life of CSCP (Corrugated Steel Culvert Pipe). Inspection frequency guidelines were developed : t...

Influence of charge carriers on corrugation of suspended graphene

NASA Astrophysics Data System (ADS)

Kirilenko, Demid A.; Gorodetsky, Andrei; Baidakova, Marina V.

2018-02-01

Electronic degrees of freedom are predicted to play a significant role in mechanics of two-dimensional crystalline membranes. Here we show that appearance of charge carriers may cause a considerable impact on suspended graphene corrugation, thus leading to additional mechanism resulting in charge carriers mobility variation with their density. This finding may account for some details of suspended graphene conductivity dependence on its doping level and suggests that proper modeling of suspended graphene-based device properties must include the influence of charge carriers on its surface corrugation.

Particle trap to sheath contact for a gas-insulated transmission line having a corrugated outer conductor

DOEpatents

Fischer, William H.; Cookson, Alan H.; Yoon, Kue H.

1984-04-10

A particle trap to outer elongated conductor or sheath contact for gas-insulated transmission lines. The particle trap to outer sheath contact of the invention is applicable to gas-insulated transmission lines having either corrugated or non-corrugated outer sheaths. The contact of the invention includes an electrical contact disposed on a lever arm which in turn is rotatably disposed on the particle trap and biased in a direction to maintain contact between the electrical contact and the outer sheath.

Corrugated cover plate for flat plate collector

DOEpatents

Hollands, K. G. Terry; Sibbitt, Bruce

1978-01-01

A flat plate radiant energy collector is providing having a transparent cover. The cover has a V-corrugated shape which reduces the amount of energy reflected by the cover away from the flat plate absorber of the collector.

Optical function of the finite-thickness corrugated pellicle of euglenoids.

PubMed

Inchaussandague, Marina E; Skigin, Diana C; Dolinko, Andrés E

2017-06-20

We explore the electromagnetic response of the pellicle of selected species of euglenoids. These microorganisms are bounded by a typical surface pellicle formed by S-shaped overlapping bands that resemble a corrugated film. We investigate the role played by this structure in the protection of the cell against UV radiation. By considering the pellicle as a periodically corrugated film of finite thickness, we applied the C-method to compute the reflectance spectra. The far-field results revealed reflectance peaks with a Q-factor larger than 10 3 in the UV region for all the illumination conditions investigated. The resonant behavior responsible for this enhancement has also been illustrated by near-field computations performed by a photonic simulation method. These results confirm that the corrugated pellicle of euglenoids shields the cell from harmful UV radiation and open up new possibilities for the design of highly UV-reflective surfaces.

Assessment of rail long-pitch corrugation

NASA Astrophysics Data System (ADS)

Valehrach, Jan; Guziur, Petr; Riha, Tomas; Plasek, Otto

2017-09-01

The paper focuses on defects of the running surface of the rail, namely the rail corrugation defect and specifically long-pitch corrugation in curves of small radii. These defects cause a shorter life of the rails, greater maintenance costs and increase the noise and vibration pollution. Therefore, it is very important to understand the formation and development of the imperfection of the rails. In the paper, various sections of railway tracks in the Czech Republic are listed, each of them completed with comparison of defect development, the particular track superstructure, rolling stock, axle load, traffic load etc. Based on performed measurements, defect development has been proved as different on sections with similar (or even same) parameters. The paper assumes that a train velocity is the significant circumstance for defect development rates. Assessment of track section with under sleeper pads, which are expected to be the one of the possible ways to suppress the corrugation defect development, is included in evaluation.

Ultrasonic geometrical characterization of periodically corrugated surfaces.

PubMed

Liu, Jingfei; Declercq, Nico F

2013-04-01

Accurate characterization of the characteristic dimensions of a periodically corrugated surface using ultrasonic imaging technique is investigated both theoretically and experimentally. The possibility of accurately characterizing the characteristic dimensions is discussed. The condition for accurate characterization and the quantitative relationship between the accuracy and its determining parameters are given. The strategies to avoid diffraction effects instigated by the periodical nature of a corrugated surface are also discussed. Major causes of erroneous measurements are theoretically discussed and experimentally illustrated. A comparison is made between the presented results and the optical measurements, revealing acceptable agreement. This work realistically exposes the capability of the proposed ultrasonic technique to accurately characterize the lateral and vertical characteristic dimensions of corrugated surfaces. Both the general principles developed theoretically as well as the proposed practical techniques may serve as useful guidelines to peers. Copyright © 2012 Elsevier B.V. All rights reserved.

A Simple Experiment to Explore Standing Waves in a Flexible Corrugated Sound Tube

NASA Astrophysics Data System (ADS)

Amorim, Maria Eva; Sousa, Teresa Delmira; Carvalho, P. Simeão; Sousa, Adriano Sampaioe

2011-09-01

Sound tubes, pipes, and singing rods are used as musical instruments and as toys to perform amusing experiments. In particular, corrugated tubes present unique characteristics with respect to the sounds they can produce; that is why they have been studied so intensively, both at theoretical and experimental levels.1-4 Experimental studies usually involve expensive and sophisticated equipment that is out of reach of school laboratory facilities.3-6 In this paper we show how to investigate quantitatively the sounds produced by a flexible sound tube corrugated on the inside by using educational equipment readily available in school laboratories, such as the oscilloscope, the microphone, the anemometer, and the air pump. We show that it is possible for students to study the discontinuous spectrum of sounds produced by a flexible corrugated tube and go even further, computing the speed of sound in air with a simple experimental procedure.

Processing of AlGaAs/GaAs quantum-cascade structures for terahertz laser

NASA Astrophysics Data System (ADS)

Szerling, Anna; Kosiel, Kamil; Szymański, Michał; Wasilewski, Zbig; Gołaszewska, Krystyna; Łaszcz, Adam; Płuska, Mariusz; Trajnerowicz, Artur; Sakowicz, Maciej; Walczakowski, Michał; Pałka, Norbert; Jakieła, Rafał; Piotrowska, Anna

2015-01-01

We report research results with regard to AlGaAs/GaAs structure processing for THz quantum-cascade lasers (QCLs). We focus on the processes of Ti/Au cladding fabrication for metal-metal waveguides and wafer bonding with indium solder. Particular emphasis is placed on optimization of technological parameters for the said processes that result in working devices. A wide range of technological parameters was studied using test structures and the analysis of their electrical, optical, chemical, and mechanical properties performed by electron microscopic techniques, energy dispersive x-ray spectrometry, secondary ion mass spectroscopy, atomic force microscopy, Fourier-transform infrared spectroscopy, and circular transmission line method. On that basis, a set of technological parameters was selected for the fabrication of devices lasing at a maximum temperature of 130 K from AlGaAs/GaAs structures grown by means of molecular beam epitaxy. Their resulting threshold-current densities were on a level of 1.5 kA/cm2. Furthermore, initial stage research regarding fabrication of Cu-based claddings is reported as these are theoretically more promising than the Au-based ones with regard to low-loss waveguide fabrication for THz QCLs.

Accurate core position control in polymer optical waveguides using the Mosquito method for three-dimensional optical wiring

NASA Astrophysics Data System (ADS)

Date, Kumi; Ishigure, Takaaki

2017-02-01

Polymer optical waveguides with graded-index (GI) circular cores are fabricated using the Mosquito method, in which the positions of parallel cores are accurately controlled. Such an accurate arrangement is of great importance for a high optical coupling efficiency with other optical components such as fiber ribbons. In the Mosquito method that we developed, a core monomer with a viscous liquid state is dispensed into another liquid state monomer for cladding via a syringe needle. Hence, the core positions are likely to shift during or after the dispensing process due to several factors. We investigate the factors, specifically affecting the core height. When the core and cladding monomers are selected appropriately, the effect of the gravity could be negligible, so the core height is maintained uniform, resulting in accurate core heights. The height variance is controlled in +/-2 micrometers for the 12 cores. Meanwhile, larger shift in the core height is observed when the needle-tip position is apart from the substrate surface. One of the possible reasons of the needle-tip height dependence is the asymmetric volume contraction during the monomer curing. We find a linear relationship between the original needle-tip height and the core-height observed. This relationship is implemented in the needle-scan program to stabilize the core height in different layers. Finally, the core heights are accurately controlled even if the cores are aligned on various heights. These results indicate that the Mosquito method enables to fabricate waveguides in which the cores are 3-dimensionally aligned with a high position accuracy.

14. DETAIL OF SOUTHWEST FRONT OF WAREHOUSE, SHOWING CORRUGATED PLASTER/ASBESTOS ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

14. DETAIL OF SOUTHWEST FRONT OF WAREHOUSE, SHOWING CORRUGATED PLASTER/ASBESTOS WALLS, WINDOWS AND ROOF. VIEW TO NORTHEAST. - Commercial & Industrial Buildings, International Harvester Company Showroom, Office & Warehouse, 10 South Main Street, Dubuque, Dubuque County, IA

Synthesis and characterization of a new family of alkylammonium–chromium phosphates with worm-like morphology

DOE Office of Scientific and Technical Information (OSTI.GOV)

Amghouz, Zakariae, E-mail: amghouz.uo@uniovi.es; Departamento de Química Orgánica e Inorgánica, Universidad de Oviedo-CINN, 33006 Oviedo; Espina, Aránzazu

A series of layered alkylammonium–chromium phosphates, formulated as [C{sub n}H{sub 2n+1}NH{sub 3}]Cr(OH)PO{sub 4} (n=2–6), has been synthesized under hydrothermal conditions. The interlayer spacing, increasing linearly with the increase of alkyl-chain length from 13.61 Å (n=2) to 21.20 Å (n=6), is occupied by a double sheet of packed amine molecules with a tilt angle of ca. 51° respect to the inorganic sheet. The powders are constituted by circular plates (diameter=0.5–3 µm, thickness=∼50 nm) with central holes when n=4–6, stacked in axial direction showing worm-like morphologies. The presence of holes, and some corrugated and zig-zag fashions observed on the edge of thinmore » circular plates are the most probable ways for the reduction of the steric tensions between organic and inorganic portions in these hybrid materials. The thermal and thermo-oxidative stability of selected compounds have been studied, including the determination of activation energy data for the decomposition processes. - Graphical abstract: A novel series of layered alkylammonium–chromium phosphates, [C{sub n}H{sub 2n+1}NH{sub 3}]Cr(OH)PO{sub 4} (n=2–6), was obtained and characterized. The interlayer spacing, increasing linearly with the increase of alkyl-chain length, is occupied by a double sheet of packed amine molecules. The powders are constituted by circular plates (diameter=0.5–3 µm, thickness=∼50 nm) with central holes when n=4–6, stacked in axial direction showing worm-like morphologies. - Highlights: • A series of alkylammonium–chromium phosphates has been obtained by the hydrothermal method. • The interlayer spacing increases linearly with the increase of alkyl-chain length. • The interlayer spacing is occupied by a double sheet of packed amine molecules. • The powders are constituted by stacked circular plates showing wormlike morphology. • Thermal behaviour depends on the atmosphere used and the intercalated amine.« less

15. Culvert and corrugated pipe with place of a thousand ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

15. Culvert and corrugated pipe with place of a thousand drips in background looking S. - Great Smoky Mountains National Park Roads & Bridges, Roaring Fork Motor Nature Trail, Between Cherokee Orchard Road & U.S. Route 321, Gatlinburg, Sevier County, TN

Structural efficiency studies of corrugated compression panels with curved caps and beaded webs

NASA Technical Reports Server (NTRS)

Davis, R. C.; Mills, C. T.; Prabhakaran, R.; Jackson, L. R.

1984-01-01

Curved cross-sectional elements are employed in structural concepts for minimum-mass compression panels. Corrugated panel concepts with curved caps and beaded webs are optimized by using a nonlinear mathematical programming procedure and a rigorous buckling analysis. These panel geometries are shown to have superior structural efficiencies compared with known concepts published in the literature. Fabrication of these efficient corrugation concepts became possible by advances made in the art of superplastically forming of metals. Results of the mass optimization studies of the concepts are presented as structural efficiency charts for axial compression.

Numerical analysis of beam with sinusoidally corrugated webs

NASA Astrophysics Data System (ADS)

Górecki, Marcin; Pieńko, Michał; Łagoda, GraŻyna

2018-01-01

The paper presents numerical tests results of the steel beam with sinusoidally corrugated web, which were performed in the Autodesk Algor Simulation Professional 2010. The analysis was preceded by laboratory tests including the beam's work under the influence of the four point bending as well as the study of material characteristics. Significant web's thickness and use of tools available in the software allowed to analyze the behavior of the plate girder as beam, and also to observe the occurrence of stresses in the characteristic element - the corrugated web. The stress distribution observed on the both web's surfaces was analyzed.

Numerical study of signal propagation in corrugated coaxial cables

DOE PAGES

Li, Jichun; Machorro, Eric A.; Shields, Sidney

2017-01-01

Our article focuses on high-fidelity modeling of signal propagation in corrugated coaxial cables. Taking advantage of the axisymmetry, the authors reduce the 3-D problem to a 2-D problem by solving time-dependent Maxwell's equations in cylindrical coordinates.They then develop a nodal discontinuous Galerkin method for solving their model equations. We prove stability and error analysis for the semi-discrete scheme. We we present our numerical results, we demonstrate that our algorithm not only converges as our theoretical analysis predicts, but it is also very effective in solving a variety of signal propagation problems in practical corrugated coaxial cables.

Impact of interfacial imperfection on transverse wave in a functionally graded piezoelectric material structure with corrugated boundaries

NASA Astrophysics Data System (ADS)

Kumar Singh, Abhishek; Kumar, Santan; Kumari, Richa

2018-03-01

The propagation behavior of Love-type wave in a corrugated functionally graded piezoelectric material layered structure has been taken into account. Concretely, the layered structure incorporates a corrugated functionally graded piezoelectric material layer imperfectly bonded to a functionally graded piezoelectric material half-space. An analytical treatment has been employed to determine the dispersion relation for both cases of electrically open condition and electrically short condition. The phase velocity of the Love-type wave has been computed numerically and its dependence on the wave number has been depicted graphically for a specific type of corrugated boundary surfaces for both said conditions. The crux of the study lies in the fact that the imperfect bonding of the interface, the corrugated boundaries present in the layer, and the material properties of the layer and the half-space strongly influence the phase velocity of the Love-type wave. It can be remarkably noted that the imperfect bonding of the interface reduces the phase velocity of the Love-type wave significantly. As a special case of the problem, it is noticed that the procured dispersion relation for both cases of electrically open and electrically short conditions is in accordance with the classical Love wave equation.

A finite element study on rail corrugation based on saturated creep force-induced self-excited vibration of a wheelset-track system

NASA Astrophysics Data System (ADS)

Chen, G. X.; Zhou, Z. R.; Ouyang, H.; Jin, X. S.; Zhu, M. H.; Liu, Q. Y.

2010-10-01

The present work proposes friction coupling at the wheel-rail interface as the mechanism for formation of rail corrugation. Stability of a wheelset-track system is studied using the finite element complex eigenvalue method. Two models for a wheelset-track system on a tight curved track and on a straight track are established. In these two models, motion of the wheelset is coupled with that of the rail by friction. Creep force at the interface is assumed to become saturated and approximately equal to friction force, which is equal to the normal contact force multiplied by dynamic coefficient of friction. The rail is supported by vertical and lateral springs and dampers at the positions of sleepers. Numerical results show that there is a strong propensity of self-excited vibration of the wheelset-track system when the friction coefficient is larger than 0.21. Some unstable frequencies fall in the range 60-1200 Hz, which correspond to frequencies of rail corrugation. Parameter sensitivity analysis shows that the dynamic coefficient of friction, spring stiffness and damping of the sleeper supports all have important influences on the rail corrugation formation. Bringing the friction coefficient below a certain level can suppress or eliminate rail corrugation.

Bounded Error Schemes for the Wave Equation on Complex Domains

NASA Technical Reports Server (NTRS)

Abarbanel, Saul; Ditkowski, Adi; Yefet, Amir

1998-01-01

This paper considers the application of the method of boundary penalty terms ("SAT") to the numerical solution of the wave equation on complex shapes with Dirichlet boundary conditions. A theory is developed, in a semi-discrete setting, that allows the use of a Cartesian grid on complex geometries, yet maintains the order of accuracy with only a linear temporal error-bound. A numerical example, involving the solution of Maxwell's equations inside a 2-D circular wave-guide demonstrates the efficacy of this method in comparison to others (e.g. the staggered Yee scheme) - we achieve a decrease of two orders of magnitude in the level of the L2-error.

Electron Cyclotron Heating system status and upgrades on DIII-D

DOE PAGES

Cengher, Mirela; Lohr, John; Gorelov, Yuri; ...

2016-06-02

The Electron Cyclotron Heating (ECH) system on the DIII-D tokamak consists of six 110 GHz gyrotrons with corrugated coaxial 31.75 mm waveguide transmission lines and steerable launching mirrors. The system has been gradually updated, leading to increased experimental flexibility and a high system reliability of 91% in the past year. Operationally, the gyrotrons can generate up to a total of 4.8 MW of rf power for pulses up to 5 seconds in length. The maximum ECH energy injected into the DIII-D has been 16.6 MJ. The HE11 mode content is over 85% for all the lines, and the transmission coefficientmore » is better than -1.1 dB for all the transmission lines, close to the theoretical value. A new depressed collector gyrotron was recently installed and was injecting up to 640 kW of power into the plasma during 2014-2015 tokamak operations. Three dual waveguide launchers, which can steer the RF beams ±20 degrees poloidally and toroidally, were used for real-time neoclassical tearing mode control and suppression. The launchers now have increased poloidal scanning speed and beam positioning accuracy of ~±2 mm at the plasma center. A new method of in-situ calibration of the mirror angle was used in conjunction with the upgrading of the encoders and motors for the launchers. Two more gyrotrons are expected to be installed and operational in 2015-2016. The first is a repaired 110 GHz, 1 MW gyrotron that had a gun failure after more than 11 years of operation at DIII-D. The second is a newly designed depressed collector tube in the 1.5 MW class, operating at 117.5 GHz, manufactured by Communications and Power Industries (CPI). It operates in the TE20,9 mode and has achieved 1.8 MW for short pulses during factory testing. Furthermore, this gyrotron is undergoing rework to address a high voltage standoff problem.« less

5. Detail, 5panel door and corrugated metal siding, Oil House, ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

5. Detail, 5-panel door and corrugated metal siding, Oil House, Southern Pacific Railroad Carlin Shops, southwest facade, view to northeast (210mm lens). - Southern Pacific Railroad, Carlin Shops, Oil House, Foot of Sixth Street, Carlin, Elko County, NV

Numerical study on the flow and heat transfer characteristics of slush nitrogen in a corrugated pipe

NASA Astrophysics Data System (ADS)

Li, Y. J.; Wu, S. Q.; Jin, T.

2017-12-01

Slush nitrogen has lower temperature, higher density and higher heat capacity than that of liquid nitrogen at normal boiling point. It is considered to be a potential coolant for high-temperature superconductive cables (HTS) that would decrease nitrogen consumption and storage cost. The corrugated pipe can help with the enhancement of heat transfer and flexibility of the coolants for HTS cables. In this paper, a 3-D Euler-Euler two-fluid model has been developed to study the flow and heat transfer characteristics of slush nitrogen in a horizontal helically corrugated pipe. By comparing with the empirical formula for pressure drop, the numerical model is confirmed to be effective for the prediction of slush nitrogen flow in corrugated pipes. The flow and heat transfer characteristics of slush nitrogen in a horizontal pipe at various working conditions (inlet solid fraction of 0-20%, inlet velocity of 0-3 m/s, heat flux of 0-12 kW/m2) have been analyzed. The friction factor of slush nitrogen is lower than that of subcooled liquid nitrogen when the slush Reynolds number is higher than 4.2×104. Moreover, the heat transfer coefficient of slush nitrogen flow in the corrugated pipe is higher than that of subcooled liquid nitrogen at velocities which is higher than that 1.76 m/s, 0.91 m/s and 0.55 m/s for slush nitrogen with solid fraction of 5%, 10% and 20%, respectively. The slush nitrogen has been confirmed to have better heat transfer performance and lower pressure drop instead of using liquid nitrogen flowing through a helically corrugated pipe.

NUCLEAR REACTOR CORE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Preece, G.E.; Bell, F.R.; Page, R.W.

1963-03-01

A nuclear reactor core is described. It contains fuel in the form of blocks or pellets that have a grooved, wrinkled, or corrugated surface to provide a greater radiating surface area. The surfaces of spaces in the core are correspondingly corrugated for maximum heat exchange area. (C.E.S.)

Fast rail corrugation detection based on texture filtering

NASA Astrophysics Data System (ADS)

Xiao, Jie; Lu, Kaixia

2018-02-01

The condition detection of rails in high-speed railway is one of the important means to ensure the safety of railway transportation. In order to replace the traditional manual inspection, save manpower and material resources, and improve the detection speed and accuracy, it is of great significance to develop a machine vision system for locating and identifying defects on rails automatically. Rail defects exhibit different properties and are divided into various categories related to the type and position of flaws on the rail. Several kinds of interrelated factors cause rail defects such as type of rail, construction conditions, and speed and/or frequency of trains using the rail. Rail corrugation is a particular kind of defects that produce an undulatory deformation on the rail heads. In high speed train, the corrugation induces harmful vibrations on wheels and its components and reduces the lifetime of rails. This type of defects should be detected to avoid rail fractures. In this paper, a novel method for fast rail corrugation detection based on texture filtering was proposed.

Modeling of second-harmonic generation of circumferential guided wave propagation in a composite circular tube

NASA Astrophysics Data System (ADS)

Li, Mingliang; Deng, Mingxi; Gao, Guangjian; Xiang, Yanxun

2018-05-01

This paper investigated modeling of second-harmonic generation (SHG) of circumferential guided wave (CGW) propagation in a composite circular tube, and then analyzed the influences of interfacial properties on the SHG effect of primary CGW. Here the effect of SHG of primary CGW propagation is treated as a second-order perturbation to its linear wave response. Due to the convective nonlinearity and the inherent elastic nonlinearity of material, there are second-order bulk driving forces and surface/interface driving stresses in the interior and at the surface/interface of a composite circular tube, when a primary CGW mode propagates along its circumference. Based on the approach of modal expansion analysis for waveguide excitation, the said second-order driving forces/stresses are regarded as the excitation sources to generate a series of double-frequency CGW modes that constitute the second-harmonic field of the primary CGW propagation. It is found that the modal expansion coefficient of each double-frequency CGW mode is closely related to the interfacial stiffness constants that are used to describe the interfacial properties between the inner and outer circular parts of the composite tube. Furthermore, changes in the interfacial stiffness constants essentially influence the dispersion relation of CGW propagation. This will remarkably affect the efficiency of cumulative SHG of primary CGW propagation. Some finite element simulations have been implemented of response characteristics of cumulative SHG to the interfacial properties. Both the theoretical analyses and numerical simulations indicate that the effect of cumulative SHG is found to be much more sensitive to changes in the interfacial properties than primary CGW propagation. The potential of using the effect of cumulative SHG by primary CGW propagation to characterize a minor change in the interfacial properties is considered.

Energy conversion device with improved seal

DOEpatents

Miller, Gerald R.; Virkar, Anil V.

1980-01-01

An energy conversion device comprising an improved sealing member adapted to seal a cation-permeable casing to the remainder of the device. The sealing member comprises a metal substrate which (i) bears a nonconductive and corrosion resistant coating on the major surface to which said casing is sealed, and (ii) is corrugated so as to render it flexible, thereby allowing said member to move relative to said casing without cracking the seal therebetween. Corrugations may be circumferential, radial, or both radial and circumferential so as to form dimples. The corrugated member may be in form of a bellows or in a substantially flat form, such as a disc.

Experimental investigation of heat transfer and effectiveness in corrugated plate heat exchangers having different chevron angles

NASA Astrophysics Data System (ADS)

Kılıç, Bayram; İpek, Osman

2017-02-01

In this study, heat transfer rate and effectiveness of corrugated plate heat exchangers having different chevron angles were investigated experimentally. Chevron angles of plate heat exchangers are β = 30° and β = 60°. For this purpose, experimentally heating system used plate heat exchanger was designed and constructed. Thermodynamic analysis of corrugated plate heat exchangers having different chevron angles were carried out. The heat transfer rate and effectiveness values are calculated. The experimental results are shown that heat transfer rate and effectiveness values for β = 60° is higher than that of the other. Obtained experimental results were graphically presented.

Acoustic radiation efficiency of a periodically corrugated rigid piston

NASA Astrophysics Data System (ADS)

Estrada, Héctor; Uris, Antonio; Meseguer, Francisco

2012-09-01

The radiation of sound by a periodically corrugated rigid piston is explored using theoretical and numerical approaches and compared with the radiation of flat rigid piston. The depth and the period of the corrugation are considered to be comparable with the wavelength in the surrounding fluid. Radiation enhancement is predicted due to cavity resonances and coherent diffraction. In addition, broad regions of low radiation efficiency are observed. Both effects could have an impact in acoustic transducers technology, either to increase the piston radiated power or to create a source of evanescent acoustic waves. The possibilities offered by this strategy in the nonlinear acoustic regime are also briefly discussed.

WKB calculation of multiple spin exchange in monolayer solid 3He

NASA Astrophysics Data System (ADS)

Ashizawa, Hisayuki; Hirashima, D. S.

2000-10-01

An insight is given into the multiple spin exchange in the registered 3×3 phase of solid 3He adsorbed on graphite with a WKB calculation taking account of the corrugation of the substrate potential. The corrugation is essential for this phase to be realized, and is found to suppress the exchange processes of many (>=4) particles to make only the two- and the three-spin exchanges relevant. When the magnitude of the corrugation is modest, the exchange can be ferromagnetic, in agreement with the experiment by Ikegami et al. [Phys. Rev. Lett. 81, 2478 (1998)]. Validity and limitation of the WKB approximation are also discussed.

Possible origin and significance of extension-parallel drainages in Arizona's metamophic core complexes

USGS Publications Warehouse

Spencer, J.E.

2000-01-01

The corrugated form of the Harcuvar, South Mountains, and Catalina metamorphic core complexes in Arizona reflects the shape of the middle Tertiary extensional detachment fault that projects over each complex. Corrugation axes are approximately parallel to the fault-displacement direction and to the footwall mylonitic lineation. The core complexes are locally incised by enigmatic, linear drainages that parallel corrugation axes and the inferred extension direction and are especially conspicuous on the crests of antiformal corrugations. These drainages have been attributed to erosional incision on a freshly denuded, planar, inclined fault ramp followed by folding that elevated and preserved some drainages on the crests of rising antiforms. According to this hypothesis, corrugations were produced by folding after subacrial exposure of detachment-fault foot-walls. An alternative hypothesis, proposed here, is as follows. In a setting where preexisting drainages cross an active normal fault, each fault-slip event will cut each drainage into two segments separated by a freshly denuded fault ramp. The upper and lower drainage segments will remain hydraulically linked after each fault-slip event if the drainage in the hanging-wall block is incised, even if the stream is on the flank of an antiformal corrugation and there is a large component of strike-slip fault movement. Maintenance of hydraulic linkage during sequential fault-slip events will guide the lengthening stream down the fault ramp as the ramp is uncovered, and stream incision will form a progressively lengthening, extension-parallel, linear drainage segment. This mechanism for linear drainage genesis is compatible with corrugations as original irregularities of the detachment fault, and does not require folding after early to middle Miocene footwall exhumations. This is desirable because many drainages are incised into nonmylonitic crystalline footwall rocks that were probably not folded under low-temperature, surface conditions. An alternative hypothesis, that drainages were localized by small fault grooves as footwalls were uncovered, is not supported by analysis of a down-plunge fault projection for the southern Rincon Mountains that shows a linear drainage aligned with the crest of a small antiformal groove on the detachment fault, but this process could have been effective elsewhere. Lineation-parallel drainages now plunge gently southwestward on the southwest ends of antiformal corrugations in the South and Buckskin Mountains, but these drainages must have originally plunged northeastward if they formed by either of the two alternative processes proposed here. Footwall exhumation and incision by northeast-flowing streams was apparently followed by core-complex arching and drainage reversal.

Heat transfer and pressure drop studies of TiO2/DI water nanofluids in helically corrugated tubes using spiraled rod inserts

NASA Astrophysics Data System (ADS)

Anbu, S.; Venkatachalapathy, S.; Suresh, S.

2018-05-01

An experimental study on the convective heat transfer and friction factor characteristics of TiO2/DI water nanofluids in uniformly heated plain and helically corrugated tubes (HCT) with and without spiraled rod inserts (SRI) under laminar flow regime is presented in this paper. TiO2 nanoparticles with an average size of 32 nm are dispersed in deionized (DI) water to form stable suspensions containing 0.1, 0.15, 0.2, and 0.25% volume concentrations of nanoparticles. It is found that the inclusion of nanoparticles to DI water ameliorated Nusselt number which increased with nanoparticles concentration upto 0.2%. Two spiraled rod inserts made of copper with different pitches (pi = 50 mm and 30 mm) are inserted in both plain and corrugated tubes and it is found that the addition of these inserts increased the Nusselt number substantially. For Helically corrugated tube with lower pitch and maximum height of corrugation (pc = 8 mm, hc = 1 mm) with 0.2% volume concentration of nanoparticles, a maximum enhancement of 15% in Nusselt number is found without insert and with insert having lower pitch (pi = 30 mm) the enhancement is 34% when compared to DI water in plain tube. The results on friction factor show a maximum penalty of about 53.56% for the above HCT.

Singing Corrugated Pipes

ERIC Educational Resources Information Center

Crawford, Frank S.

1974-01-01

Presents theoretical and experimental observations made with a musical toy called Hummer consisting of a corrugated flexible plastic tube about three-feet long and one-inch diam open at both ends. Included are descriptions of three new instruments: the Water Pipe, the Gas-Pipe Corrugahorn Bugle, and the Gas-Pipe Blues Corrugahorn. (CC)

Use of a corrugated surface to enhance radiation tolerance in a GaAs solar cell

NASA Technical Reports Server (NTRS)

Leon, Rosa P.; Piszczor, Michael F., Jr.

1985-01-01

The use of a corrugated surface on a GaAs solar cell and its effects on radiation resistance were studied. A compute code was developed to determine the performance of the cell for various geometric parameters. The large optical absorption coefficient of GaAs allows grooves to be only 4-5 micrometers deep. Using accepted material parameters for GaAs solar cells the theoretical performances were compared for various corrugated cells before and after minority carrier diffusion length degradation. The total power output was maximized for both n(+)/p and p(+)/n cells. Optimum values of 1.0-1.5 and 5.0 micrometers for groove and ridge widths respectively were determined.

SELF-TRAPPING OF DISKOSEISMIC CORRUGATION MODES IN NEUTRON STAR SPACETIMES

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsang, David; Pappas, George

2016-02-10

We examine the effects of higher-order multipole contributions of rotating neutron star (NS) spacetimes on the propagation of corrugation (c-)modes within a thin accretion disk. We find that the Lense–Thirring precession frequency, which determines the propagation region of the low-frequency fundamental corrugation modes, can experience a turnover allowing for c-modes to become self-trapped for sufficiently high dimensionless spin j and quadrupole rotational deformability α. If such self-trapping c-modes can be detected, e.g., through phase-resolved spectroscopy of the iron line for a high-spin low-mass accreting neutron star, this could potentially constrain the spin-induced NS quadrupole and the NS equation of state.

Rectangular microstrip antenna with corrugation like defects at radiating edge: A new approach to reduce cross polarization radiation

NASA Astrophysics Data System (ADS)

Pawar, U. A.; Mondal, D.; Nagaraju, A.; Chakraborty, S.; Singh, L. L. K.; Chattopadhyay, S.

2018-03-01

In this paper, single layer, simple and compact RMA, with corrugation like defects at the radiating edge, is studied thoroughly to reduce XP radiation from the patch. Unlike the earlier works reported on defected ground structure integrated patches and defect patch structures, in this work, corrugation like linear defects have been placed at the radiating edges of the patch to reduce cross polarisation radiation. Around 30-40 dB of CP-XP isolation is observed in H-plane with 7% impedance bandwidth and in E-plane also, more than 55 dB CP-XP isolation is found. The proposed structure is very simple to design and easy to fabricate.

Self-Trapping of Diskoseismic Corrugation Modes in Neutron Star Spacetimes

NASA Astrophysics Data System (ADS)

Tsang, David; Pappas, George

2016-02-01

We examine the effects of higher-order multipole contributions of rotating neutron star (NS) spacetimes on the propagation of corrugation (c-)modes within a thin accretion disk. We find that the Lense-Thirring precession frequency, which determines the propagation region of the low-frequency fundamental corrugation modes, can experience a turnover allowing for c-modes to become self-trapped for sufficiently high dimensionless spin j and quadrupole rotational deformability α. If such self-trapping c-modes can be detected, e.g., through phase-resolved spectroscopy of the iron line for a high-spin low-mass accreting neutron star, this could potentially constrain the spin-induced NS quadrupole and the NS equation of state.

Fields and coupling between coils embedded in conductive environments

NASA Astrophysics Data System (ADS)

Chu, Son; Vallecchi, Andrea; Stevens, Christopher J.; Shamonina, Ekaterina

2018-02-01

An approximate solution is developed for the mutual inductance of two circular coils enclosed by insulating cavities in a conducting medium. This solution is used to investigate the variation of the mutual inductance upon the conductivity of the background (e.g., soil, seawater or human body), as well as upon other parameters such as the vertical of the coils and the displacement of one of the coils in the horizontal plane. Our theoretical results are compared with full wave simulations and a previous solution valid when a conductive slab is inserted between two coupled resonant coils. The proposed approach can have direct impact on the design and optimisation of magnetoinductive waveguides and wireless power transfer for underground/underwater networks and embedded biomedical systems.

Enhanced spin wave propagation in magnonic rings by bias field modulation

NASA Astrophysics Data System (ADS)

Venkat, G.; Venkateswarlu, D.; Joshi, R. S.; Franchin, M.; Fangohr, H.; Anil Kumar, P. S.; Prabhakar, A.

2018-05-01

We simulate the spin wave (SW) dynamics in ring structures and obtain the ω - k dispersion relations corresponding to the output waveguide. Different bias field configurations affect the transfer of SW power from one arm of the structure to the other arm. To this end, we show that circular or radial bias fields are more suitable for energy transfer across the ring than the conventional horizontal bias field Hx. The SW dispersion shows that modes excited, when the bias field is along the ring radius, are almost 10 dB higher in power when compared to the modal power in the case of Hx. This is also corroborated by the SW energy density in the receiving stub.

Optical fiber designs for beam shaping

NASA Astrophysics Data System (ADS)

Farley, Kevin; Conroy, Michael; Wang, Chih-Hao; Abramczyk, Jaroslaw; Campbell, Stuart; Oulundsen, George; Tankala, Kanishka

2014-03-01

A large number of power delivery applications for optical fibers require beams with very specific output intensity profiles; in particular applications that require a focused high intensity beam typically image the near field (NF) intensity distribution at the exit surface of an optical fiber. In this work we discuss optical fiber designs that shape the output beam profile to more closely correspond to what is required in many real world industrial applications. Specifically we present results demonstrating the ability to transform Gaussian beams to shapes required for industrial applications and how that relates to system parameters such as beam product parameter (BPP) values. We report on the how different waveguide structures perform in the NF and show results on how to achieve flat-top with circular outputs.

A high resolution soil moisture radiometer

NASA Technical Reports Server (NTRS)

Dod, L. R.

1980-01-01

The design of an L-band high resolution soil moisture radiometer is described. The selected system is a planar slotted waveguide array at L-band frequencies. The square aperture is 74.75 m by 74.75 m subdivided into 8 tilted subarrays. The system has a 290 km circular orbit and provides a spatial resolution of 1 km. The aperture forms 230 simultaneous beams in a cross-track pattern which covers a swath 420 km wide. A revisit time of 6 days is provided for an orbit inclination of 50 deg. The 1 km resolution cell allows an integration time of 1/7 second and sharing this time period sequentially between two orthogonal polarization modes can provide a temperature resolution of 0.7 K.

Topological transitions in continuously deformed photonic crystals

NASA Astrophysics Data System (ADS)

Zhu, Xuan; Wang, Hai-Xiao; Xu, Changqing; Lai, Yun; Jiang, Jian-Hua; John, Sajeev

2018-02-01

We demonstrate that multiple topological transitions can occur, with high sensitivity, by continuous change of the geometry of a simple two-dimensional dielectric-frame photonic crystal consisting of circular air holes. By changing the radii of the holes and/or the distance between them, multiple transitions between normal and topological photonic band gaps (PBGs) can appear. The time-reversal symmetric topological PBGs resemble the quantum spin Hall insulator of electrons and have two counterpropagating edge states. We search for optimal topological transitions, i.e., sharp transitions sensitive to the geometry, and optimal topological PBGs, i.e., large PBGs with a clean spectrum of edge states. Such optimizations reveal that dielectric-frame photonic crystals are promising for optical sensors and unidirectional waveguides.

Investigations of the polarization behavior of quantum cascade lasers by Stokes parameters.

PubMed

Janassek, Patrick; Hartmann, Sébastien; Molitor, Andreas; Michel, Florian; Elsäßer, Wolfgang

2016-01-15

We experimentally investigate the full polarization behavior of mid-infrared emitting quantum cascade lasers (QCLs) in terms of measuring the complete Stokes parameters, instead of only projecting them on a linear polarization basis. We demonstrate that besides the pre-dominant linear TM polarization of the emitted light as governed by the selection rules of the intersubband transition, small non-TM contributions, e.g., circularly polarized light, are present reflecting the birefringent behavior of the semiconductor quantum well waveguide. Surprisingly unique is the persistence of these polarization properties well below laser threshold. These investigations give further insight into understanding, manipulating, and exploiting the polarization properties of QCLs, both from a laser point of view and with respect toward applications.

Auto-locking waveguide amplifier system for lidar and magnetometric applications

NASA Astrophysics Data System (ADS)

Pouliot, A.; Beica, H. C.; Carew, A.; Vorozcovs, A.; Carlse, G.; Kumarakrishnan, A.

2018-02-01

We describe a compact waveguide amplifier system that is suitable for optically pumping rubidium magnetometers. The system consists of an auto-locking vacuum-sealed external cavity diode laser, a semiconductor tapered amplifier and a pulsing unit based on an acousto-optic modulator. The diode laser utilises optical feedback from an interference filter to narrow the linewidth of an inexpensive laser diode to 500 kHz. This output is scannable over an 8 GHz range (at 780 nm) and can be locked without human intervention to any spectral marker in an expandable library of reference spectra, using the autolocking controller. The tapered amplifier amplifies the output from 50 mW up to 2 W with negligible distortions in the spectral quality. The system can operate at visible and near infrared wavelengths with MHz repetition rates. We demonstrate optical pumping of rubidium vapour with this system for magnetometric applications. The magnetometer detects the differential absorption of two orthogonally polarized components of a linearly polarized probe laser following optical pumping by a circularly polarized pump laser. The differential absorption signal is studied for a range of pulse lengths, pulse amplitudes and DC magnetic fields. Our results suggest that this laser system is suitable for optically pumping spin-exchange free magnetometers.

Method for producing ultrafine-grained materials using repetitive corrugation and straightening

DOEpatents

Zhu, Yuntian T.; Lowe, Terry C.; Jiang, Honggang; Huang, Jianyu

2001-01-01

A method of refining the grain structure and improving the hardness and strength properties of a metal or metal alloy workpiece is disclosed. The workpiece is subjected to forces that corrugate and then straighten the workpiece. These steps are repeated until an ultrafine-grained product having improved hardness and strength is produced.

Optimum fiber distribution in singlewall corrugated fiberboard

Treesearch

Millard W. Johnson; Thomas J. Urbanik; William E. Denniston

1979-01-01

Determining optimum distribution of fiber through rational design of corrugated fiberboard could result in significant reductions in fiber required to meet end-use conditions, with subsequent reductions in price pressure and extension of the softwood timber supply. A theory of thin plates under large deformations is developed that is both kinematically and physically...

More rapid edgewise crush test methods

Treesearch

Thomas J. Urbanik; Arthur H. Catlin; Davide R. Friedman; Richard C. Lund

1993-01-01

The use of paraffin wax to reinforce the loading edges of corrugated fiberboard edge-crush specimens requires that the specimens be reconditioned after waxing. The traditional practice employing a 24-h reconditioning period is a conservative approach based on the moisture response rate of corrugated containers. An interlaboratory study was conducted to determine the...

Finite element corroboration of buckling phenomena observed in corrugated boxes

Treesearch

Thomas J. Urbanik; Edmond P. Saliklis

2003-01-01

Conventional compression strength formulas for corrugated fiberboard boxes are limited to geometry and material that produce an elastic postbuckling failure. Inelastic postbuckling can occur in squatty boxes and trays, but a mechanistic rationale for unifying observed strength data is lacking. This study combines a finite element model with a parametric design of the...

Soda-Anthraquinone Durian (Durio Zibethinus Murr.) Rind Linerboard and Corrugated Medium Paper: A Preliminary Test

NASA Astrophysics Data System (ADS)

Rizal Masrol, Shaiful; Irwan Ibrahim, Mohd Halim; Adnan, Sharmiza; Mubarak Sa'adon, Amir; Ika Sukarno, Khairil; Fadrol Hisham Yusoff, Mohd

2017-08-01

A preliminary test was conducted to investigate the characteristics of linerboard and corrugated medium paper made from durian rind waste. Naturally dried durian rinds were pulped according to Soda-Anthraquinone (Soda-AQ) pulping process with a condition of 20% active alkali, 0.1% AQ, 7:1 liquor to material ratio, 120 minutes cooking time and 170°C cooking temperature. The linerboard and corrugated medium paper with a basis weight of 120 gsm were prepared and evaluated according to Malaysian International Organization for Standardization (MS ISO) and Technical Association of the Pulp and Paper Industry (TAPPI). The results indicate that the characteristics of durian rind linerboard are comparable with other wood or non-wood based paper and current commercial paper. However, low CMT value for corrugated medium and water absorptiveness quality for linerboard could be improved in future. Based on the bulk density (0.672 g/cm3), burst index (3.12 kPa.m2/g) and RCT (2.00 N.m2/g), the durian rind has shown a good potential and suitable as an alternative raw material source for linerboard industry.

Geologic continuous casting below continental and deep-sea detachment faults and at the striated extrusion of Sacsayhuaman, Peru

USGS Publications Warehouse

Spencer, J.E.

1999-01-01

In the common type of industrial continuous casting, partially molten metal is extruded from a vessel through a shaped orifice called a mold in which the metal assumes the cross-sectional form of the mold as it cools and solidifies. Continuous casting can be sustained as long as molten metal is supplied and thermal conditions are maintained. I propose that a similar process produced parallel sets of grooves in three geologic settings, as follows: (1) corrugated metamorphic core complexes where mylonized mid-crustal rocks were exhumed by movement along low-angle normal faults known as detachment faults; (2) corrugated submarine surfaces where ultramafic and mafic rocks were exhumed by normal faulting within oceanic spreading centers; and (3) striated magma extrusions exemplified by the famous grooved outcrops at the Inca fortress of Sacsayhuaman in Peru. In each case, rocks inferred to have overlain the corrugated surface during corrugation genesis molded and shaped a plastic to partially molten rock mass as it was extruded from a moderate- to high-temperature reservoir.

Wakefield potentials of corrugated structures

DOE Office of Scientific and Technical Information (OSTI.GOV)

Novokhatski, A.

A corrugated structure, which is used in “dechirper” devices, is usually a pipe or two plates with small corrugations (bumps) on the walls. There is a good single-mode description of the wake potentials excited by a relativistic bunch if the wave length of the mode is much longer than the distance between the bumps in the pipe. However, ultrashort bunches, which are now used in free electron lasers, excite much higher frequency fields and the corresponding wake potentials will be very different from the single-mode description. We have made analyses of these wake potentials based on a numerical solution ofmore » Maxwell’s equations. It was confirmed that the behavior of the wakefields of ultrashort bunches in corrugated structures is not much different from the fields excited usually in accelerating structures where the wake potentials are described by the exponential function. For a practical application we present results for the SLAC “dechirper.” We also carried out calculations for a similar device, that was installed and measured at the Pohang Accelerator Laboratory, Korea. As a result, we find very good agreement with the experimental results.« less

Wakefield potentials of corrugated structures

DOE PAGES

Novokhatski, A.

2015-10-22

A corrugated structure, which is used in “dechirper” devices, is usually a pipe or two plates with small corrugations (bumps) on the walls. There is a good single-mode description of the wake potentials excited by a relativistic bunch if the wave length of the mode is much longer than the distance between the bumps in the pipe. However, ultrashort bunches, which are now used in free electron lasers, excite much higher frequency fields and the corresponding wake potentials will be very different from the single-mode description. We have made analyses of these wake potentials based on a numerical solution ofmore » Maxwell’s equations. It was confirmed that the behavior of the wakefields of ultrashort bunches in corrugated structures is not much different from the fields excited usually in accelerating structures where the wake potentials are described by the exponential function. For a practical application we present results for the SLAC “dechirper.” We also carried out calculations for a similar device, that was installed and measured at the Pohang Accelerator Laboratory, Korea. As a result, we find very good agreement with the experimental results.« less

Measurements of terahertz radiation generated using a metallic, corrugated pipe

DOE PAGES

Bane, Karl; Stupakov, Gennady; Antipov, Sergey; ...

2016-11-23

Here, a method for producing narrow-band THz radiation proposes passing an ultra-relativistic beam through a metallic pipe with small periodic corrugations. We present results of a measurement of such an arrangement at Brookhaven's Accelerator Test Facility (ATF). Our pipe was copper and was 5 cm long; the aperture was cylindrically symmetric, with a 1 mm (radius) bore and a corrugation depth (peak-to-peak) of 60 µm. In the experiment we measured both the effect on the beam of the structure wakefield and the spectral properties of the radiation excited by the beam. We began by injecting a relatively long beam comparedmore » to the wavelength of the radiation, but with short rise time, to excite the structure, and then used a downstream spectrometer to infer the radiation wavelength. This was followed by injecting a shorter bunch, and then using an interferometer (also downstream of the corrugated pipe) to measure the spectrum of the induced THz radiation. For the THz pulse we obtain and compare with calculations: the central frequency, the bandwidth, and the spectral power—compared to a diffraction radiation background signal.« less

Measurements of terahertz radiation generated using a metallic, corrugated pipe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bane, Karl; Stupakov, Gennady; Antipov, Sergey

Here, a method for producing narrow-band THz radiation proposes passing an ultra-relativistic beam through a metallic pipe with small periodic corrugations. We present results of a measurement of such an arrangement at Brookhaven's Accelerator Test Facility (ATF). Our pipe was copper and was 5 cm long; the aperture was cylindrically symmetric, with a 1 mm (radius) bore and a corrugation depth (peak-to-peak) of 60 µm. In the experiment we measured both the effect on the beam of the structure wakefield and the spectral properties of the radiation excited by the beam. We began by injecting a relatively long beam comparedmore » to the wavelength of the radiation, but with short rise time, to excite the structure, and then used a downstream spectrometer to infer the radiation wavelength. This was followed by injecting a shorter bunch, and then using an interferometer (also downstream of the corrugated pipe) to measure the spectrum of the induced THz radiation. For the THz pulse we obtain and compare with calculations: the central frequency, the bandwidth, and the spectral power—compared to a diffraction radiation background signal.« less

Influence of prestress and periodic corrugated boundary surfaces on Rayleigh waves in an orthotropic medium over a transversely isotropic dissipative semi-infinite substrate

NASA Astrophysics Data System (ADS)

Gupta, Shishir; Ahmed, Mostaid

2017-01-01

The paper environs the study of Rayleigh-type surface waves in an orthotropic crustal layer over a transversely isotropic dissipative semi-infinite medium under the effect of prestress and corrugated boundary surfaces. Separate displacement components for both media have been derived in order to characterize the dynamics of individual materials. Suitable boundary conditions have been employed upon the surface wave solutions of the elasto-dynamical equations that are taken into consideration in the light of corrugated boundary surfaces. From the real part of the sixth-order complex determinantal expression, we obtain the frequency equation for Rayleigh waves concerning the proposed earth model. Possible special cases have been envisaged and they fairly comply with the corresponding results for classical cases. Numerical computations have been performed in order to graphically demonstrate the role of the thickness of layer, prestress, corrugation parameters and dissipation on Rayleigh wave velocity. The study may be regarded as important due to its possible applications in delay line services and investigating deformation characteristics of solids as well as typical rock formations.

Psychometric properties of startle and corrugator response in NPU, Affective Picture Viewing, and Resting State tasks

PubMed Central

Kaye, Jesse T.; Bradford, Daniel E.; Curtin, John J.

2016-01-01

The current study provides a comprehensive evaluation of critical psychometric properties of commonly used psychophysiology laboratory tasks/measures within the NIMH RDoC. Participants (N = 128) completed the No Shock, Predictable Shock, Unpredictable Shock (NPU) task, Affective Picture Viewing task, and Resting State task at two study visits separated by one week. We examined potentiation/modulation scores in NPU (predictable or unpredictable shock vs. no shock) and Affective Picture Viewing tasks (pleasant or unpleasant vs. neutral pictures) for startle and corrugator responses with two commonly used quantification methods. We quantified startle potentiation/modulation scores with raw and standardized responses. We quantified corrugator potentiation/modulation in the time and frequency domains. We quantified general startle reactivity in the Resting State Task as the mean raw startle response during the task. For these three tasks, two measures, and two quantification methods we evaluated effect size robustness and stability, internal consistency (i.e., split-half reliability), and one-week temporal stability. The psychometric properties of startle potentiation in the NPU task were good but concerns were noted for corrugator potentiation in this task. Some concerns also were noted for the psychometric properties of both startle and corrugator modulation in the Affective Picture Viewing task, in particular for pleasant picture modulation. Psychometric properties of general startle reactivity in the Resting State task were good. Some salient differences in the psychometric properties of the NPU and Affective Picture Viewing tasks were observed within and across quantification methods. PMID:27167717

Enhanced photoluminescence of corrugated Al2O3 film assisted by colloidal CdSe quantum dots.

PubMed

Bai, Zhongchen; Hao, Licai; Zhang, Zhengping; Huang, Zhaoling; Qin, Shuijie

2017-05-19

We present the enhanced photoluminescence (PL) of a corrugated Al 2 O 3 film enabled by colloidal CdSe quantum dots. The colloidal CdSe quantum dots are fabricated directly on a corrugated Al 2 O 3 substrate using an electrochemical deposition (ECD) method in a microfluidic system. The photoluminescence is excited by using a 150 nm diameter ultraviolet laser spot of a scanning near-field optical microscope. Owing to the electron transfer from the conduction band of the CdSe quantum dots to that of Al 2 O 3 , the enhanced photoluminescence effect is observed, which results from the increase in the recombination rate of electrons and holes on the Al 2 O 3 surface and the reduction in the fluorescence of the CdSe quantum dots. A periodically-fluctuating fluorescent spectrum was exhibited because of the periodical wire-like corrugated Al 2 O 3 surface serving as an optical grating. The spectral topographic map around the fluorescence peak from the Al 2 O 3 areas covered with CdSe quantum dots was unique and attributed to the uniform deposition of CdSe QDs on the corrugated Al 2 O 3 surface. We believe that the microfluidic ECD system and the surface enhanced fluorescence method described in this paper have potential applications in forming uniform optoelectronic films of colloidal quantum dots with controllable QD spacing and in boosting the fluorescent efficiency of weak PL devices.

Rail corrugation growth accounting for the flexibility and rotation of the wheel set and the non-Hertzian and non-steady-state effects at contact patch

NASA Astrophysics Data System (ADS)

Vila, Paloma; Baeza, Luis; Martínez-Casas, José; Carballeira, Javier

2014-05-01

In this work, a simulation tool is developed to analyse the growth of rail corrugation consisting of several models connected in a feedback loop in order to account for both the short-term dynamic vehicle-track interaction and the long-term damage. The time-domain vehicle-track interaction model comprises a flexible rotating wheel set model, a cyclic track model based on a substructuring technique and a non-Hertzian and non-steady-state three-dimensional wheel-rail contact model, based on the variational theory by Kalker. Wear calculation is performed with Archard's wear model by using the contact parameters obtained with the non-Hertzian and non-steady-state three-dimensional contact model. The aim of this paper is to analyse the influence of the excitation of two coinciding resonances of the flexible rotating wheel set on the rail corrugation growth in the frequency range from 20 to 1500 Hz, when contact conditions similar to those that can arise while a wheel set is negotiating a gentle curve are simulated. Numerical results show that rail corrugation grows only on the low rail for two cases in which two different modes of the rotating wheel set coincide in frequency. In the first case, identified by using the Campbell diagram, the excitation of both the backward wheel mode and the forward third bending mode of the wheel set model (B-F modes) promotes the growth of rail corrugation with a wavelength of 110 mm for a vehicle velocity of 142 km/h. In the second case, the excitation of both the backward wheel mode and the backward third bending mode (B-B modes) gives rise to rail corrugation growth at a wavelength of 156 mm when the vehicle velocity is 198 km/h.

An InP/Si heterojunction photodiode fabricated by self-aligned corrugated epitaxial lateral overgrowth

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, Y. T., E-mail: yasun@kth.se; Omanakuttan, G.; Lourdudoss, S.

2015-05-25

An n-InP/p-Si heterojunction photodiode fabricated by corrugated epitaxial lateral overgrowth (CELOG) method is presented. N-InP/p-Si heterojunction has been achieved from a suitable pattern containing circular shaped openings in a triangular lattice on the InP seed layer on p-Si substrate and subsequent CELOG of completely coalesced n-InP. To avoid current path through the seed layer in the final photodiode, semi-insulating InP:Fe was grown with adequate thickness prior to n-InP growth in a low pressure hydride vapor phase epitaxy reactor. The n-InP/p-Si heterointerface was analyzed by scanning electron microscopy and Raman spectroscopy. Room temperature cross-sectional photoluminescence (PL) mapping illustrates the defect reductionmore » effect in InP grown on Si by CELOG method. The InP PL intensity measured above the InP/Si heterojunction is comparable to that of InP grown on a native planar substrate indicating low interface defect density of CELOG InP despite of 8% lattice mismatch with Si. The processed n-InP/p-Si heterojunction photodiodes show diode characteristics from the current-voltage (I-V) measurements with a dark current density of 0.324 mA/cm{sup 2} at a reverse voltage of −1 V. Under the illumination of AM1.5 conditions, the InP/Si heterojunction photodiode exhibited photovoltaic effect with an open circuit voltage of 180 mV, a short circuit current density of 1.89 mA/cm{sup 2}, an external quantum efficiency of 4.3%, and an internal quantum efficiency of 6.4%. This demonstration of epitaxially grown InP/Si heterojunction photodiode will open the door for low cost and high efficiency solar cells and photonic integration of III-Vs on silicon.« less

Photovoltaic effect in ferroelectric ceramics

NASA Technical Reports Server (NTRS)

Epstein, D. J.; Linz, A.; Jenssen, H. P.

1982-01-01

The ceramic structure was simulated in a form that is more tractable to correlation between experiment and theory. Single crystals (of barium titanate) were fabricated in a simple corrugated structure in which the pedestals of the corrugation simulated the grain while the intervening cuts could be filled with materials simulating the grain boundaries. The observed photovoltages were extremely small (100 mv).

Strength and processing properties of wet-formed hardboards from recycled corrugated containers and commercial hardboard fibers

Treesearch

J. F. Hunt; C. B. Vick

1999-01-01

Recycled paper fiber recovered from our municipal solid waste stream could potentially be used in structural hardboard products. This study compares strength properties and processing variables of wet-formed high-density hardboard panels made from recycled old corrugated container (OCC) fibers and virgin hardboard fibers using continuous pressure during drying. The...

Comparison of postbuckling model and finite element model with compression strength of corrugated boxes

Treesearch

Thomas J. Urbanik; Edmond P. Saliklis

2002-01-01

Conventional compression strength formulas for corrugated fiberboard boxes are limited to geometry and material that produce an elastic postbuckling failure. Inelastic postbuckling can occur in squatty boxes and trays, but a mechanistic rationale for unifying observed strength data is lacking. This study employs a finite element model, instead of actual experiments, to...

Binderless fiberboard : comparison of fiber from recycled corrugated containers and refined small-diameter whole treetops

Treesearch

John F. Hunt; Karen Supan

2006-01-01

Whereas many research activities focus on developing value-added processes that use forest residues, scientists must also investigate the mechanical properties of products made from recycled fiber resources. This study compared the tensile and bending properties of binderless panels made from recycled corrugated containers with properties of panels made from lodgepole...

Self-Relevance Appraisal Influences Facial Reactions to Emotional Body Expressions

PubMed Central

Grèzes, Julie; Philip, Léonor; Chadwick, Michèle; Dezecache, Guillaume; Soussignan, Robert; Conty, Laurence

2013-01-01

People display facial reactions when exposed to others' emotional expressions, but exactly what mechanism mediates these facial reactions remains a debated issue. In this study, we manipulated two critical perceptual features that contribute to determining the significance of others' emotional expressions: the direction of attention (toward or away from the observer) and the intensity of the emotional display. Electromyographic activity over the corrugator muscle was recorded while participants observed videos of neutral to angry body expressions. Self-directed bodies induced greater corrugator activity than other-directed bodies; additionally corrugator activity was only influenced by the intensity of anger expresssed by self-directed bodies. These data support the hypothesis that rapid facial reactions are the outcome of self-relevant emotional processing. PMID:23405230

Waveguide arrangements based on adiabatic elimination

DOEpatents

Suchowski, Haim; Mrejen, Michael; Wu, Chihhui; Zhang, Xiang

2016-09-13

This disclosure provides systems, methods, and apparatus related to nanophotonics. In one aspect, an arrangement of waveguides includes a substrate and three waveguides. Each of the three waveguides may be a linear waveguide. A second waveguide is positioned between a first waveguide and a third waveguide. The dimensions and positions of the first, the second, and the third waveguides are specified to substantially eliminate coupling between the first waveguide and the third waveguide over a distance of about 1 millimeter to 2 millimeters along lengths of the first waveguide, the second waveguide, and the third waveguide.

Variable stiffness corrugated composite structure with shape memory polymer for morphing skin applications

NASA Astrophysics Data System (ADS)

Gong, Xiaobo; Liu, Liwu; Scarpa, Fabrizio; Leng, Jinsong; Liu, Yanju

2017-03-01

This work presents a variable stiffness corrugated structure based on a shape memory polymer (SMP) composite with corrugated laminates as reinforcement that shows smooth aerodynamic surface, extreme mechanical anisotropy and variable stiffness for potential morphing skin applications. The smart composite corrugated structure shows a low in-plane stiffness to minimize the actuation energy, but also possess high out-of-plane stiffness to transfer the aerodynamic pressure load. The skin provides an external smooth aerodynamic surface because of the one-sided filling with the SMP. Due to variable stiffness of the shape memory polymer the morphing skin exhibits a variable stiffness with a change of temperature, which can help the skin adjust its stiffness according different service environments and also lock the temporary shape without external force. Analytical models related to the transverse and bending stiffness are derived and validated using finite element techniques. The stiffness of the morphing skin is further investigated by performing a parametric analysis against the geometry of the corrugation and various sets of SMP fillers. The theoretical and numerical models show a good agreement and demonstrate the potential of this morphing skin concept for morphing aircraft applications. We also perform a feasibility study of the use of this morphing skin in a variable camber morphing wing baseline. The results show that the morphing skin concept exhibits sufficient bending stiffness to withstand the aerodynamic load at low speed (less than 0.3 Ma), while demonstrating a large transverse stiffness variation (up to 191 times) that helps to create a maximum mechanical efficiency of the structure under varying external conditions.

Moisture diffusion through a corrugated fiberboard under compressive loading : its deformation and stiffness response

Treesearch

Adeeb A. Rahman; Thomas J. Urbanik; Mustafa Mahamid

2002-01-01

This research develops a model using finite element to study the response of a panel made of a typical commercial corrugated fireboard due to an induced moisture function at one side of the fiberboard. The model predicts how the moisture diffusion will permeate through the fiberboard's layers (medium and liners) providing information on moisture content at any...

Strength and life criteria for corrugated fiberboard by three methods

Treesearch

Thomas J. Urbanik

1997-01-01

The conventional test method for determining the stacking life of corrugated containers at a fixed load level does not adequately predict a safe load when storage time is fixed. This study introduced multiple load levels and related the probability of time at failure to load. A statistical analysis of logarithm-of-time failure data varying with load level predicts the...

Optical coating on a corrugated surface to align the polarization of an unpolarized wave without loss

NASA Astrophysics Data System (ADS)

Jen, Yi Jun

2017-12-01

A multilayer comprising birefringent thin films is devised to present to function as a polarization beam splitter and waveplate simultaneously. By arranging such a multilayer on a right triangle-shaped corrugated surface, a polarizer is realized to align the randomly oscillating electric field of an unpolarized wave into a linear polarized wave without loss.

Fabrication and evaluation of superplastically formed/weld-brazed corrugated compression panels with beaded webs

NASA Technical Reports Server (NTRS)

Royster, D. M.; Davis, R. C.; Shinn, J. M., Jr.; Bales, T. T.; Wiant, H. R.

1985-01-01

A study was made to investigate the feasibility of superplastically forming corrugated panels with beaded webs and to demonstrate the structural integrity of these panels by testing. The test panels in the study consist of superplastically formed titanium alloy Ti-6Al-4V half-hat elements that are joined by weld-brazing to titanium alloy Ti-6Al-4V caps to form either single-corrugation compression panels or multiple-corrugation compression panels. Stretching and subsequent thinning of the titanium sheet during superplastic forming is reduced by approximately 35 percent with a shallow half-hat die concept instead of a deep die concept and results in a more uniform thickness across the beaded webs. The complete panels are tested in end compression at room temperature and the results compared with analysis. The heavily loaded panels failed at loads approaching the yield strength of the titanium material. At maximum load, the caps wrinkled locally accompanied with separation of the weld-braze joint in the wrinkle. None of the panels tested, however, failed catastrophically in the weld-braze joint. Experimental test results are in good agreement with structural analysis of the panels.

Mitigation of Biofilm Formation on Corrugated Cardboard Fresh Produce Packaging Surfaces Using a Novel Thiazolidinedione Derivative Integrated in Acrylic Emulsion Polymers.

PubMed

Brandwein, Michael; Al-Quntar, Abed; Goldberg, Hila; Mosheyev, Gregory; Goffer, Moshe; Marin-Iniesta, Fulgencio; López-Gómez, Antonio; Steinberg, Doron

2016-01-01

Various surfaces associated with the storage and packing of food are known to harbor distinct bacterial pathogens. Conspicuously absent among the plethora of studies implicating food packaging materials and machinery is the study of corrugated cardboard packaging, the worldwide medium for transporting fresh produce. In this study, we observed the microbial communities of three different store-bought fruits and vegetables, along with their analog cardboard packaging using high throughput sequencing technology. We further developed an anti-biofilm polymer meant to coat corrugated cardboard surfaces and mediate bacterial biofilm growth on said surfaces. Integration of a novel thiazolidinedione derivative into the acrylic emulsion polymers was assessed using Energy Dispersive X-ray Spectrometry (EDS) analysis and surface topography was visualized and quantified on corrugated cardboard surfaces. Biofilm growth was measured using q-PCR targeting the gene encoding 16s rRNA. Additionally, architectural structure of the biofilm was observed using SEM. The uniform integration of the thiazolidinedione derivative TZD-6 was confirmed, and it was determined via q-PCR to reduce biofilm growth by ~80% on tested surfaces. A novel and effective method for reducing microbial load and preventing contamination on food packaging is thereby proposed.

The effects of road crossings on prairie stream habitat and function

USGS Publications Warehouse

Bouska, Wesley W.; Keane, Timothy; Paukert, Craig P.

2010-01-01

Improperly designed stream crossing structures may alter the form and function of stream ecosystems and habitat and prohibit the movement of aquatic organisms. Stream sections adjoining five concrete box culverts, five low-water crossings (concrete slabs vented by one or multiple culverts), and two large, single corrugated culvert vehicle crossings in eastern Kansas streams were compared to reference reaches using a geomorphologic survey and stream classification. Stream reaches were also compared upstream and downstream of crossings, and crossing measurements were used to determine which crossing design best mimicked the natural dimensions of the adjoining stream. Four of five low-water crossings, three of five box culverts, and one of two large, single corrugated pipe culverts changed classification from upstream to downstream of the crossings. Mean riffle spacing upstream at low-water crossings (8.6 bankfull widths) was double that of downstream reaches (mean 4.4 bankfull widths) but was similar upstream and downstream of box and corrugated pipe culverts. There also appeared to be greater deposition of fine sediments directly upstream of these designs. Box and corrugated culverts were more similar to natural streams than low-water crossings at transporting water, sediments, and debris during bankfull flows.

Investigation on Periodically Surface-Corrugated Long-Period Gratings Inscribed on Photonic Crystal Fibers

NASA Astrophysics Data System (ADS)

Han, Young-Geun

2017-04-01

Transmission characteristics of periodically surface-corrugated long-period gratings (LPGs) inscribed on photonic crystal fibers (PCFs) using a wet-etching technique were experimentally investigated. A conventional wet method was implemented to periodically engrave the silica cladding region of the PCFs resulting in the periodic surface corrugation in the PCF. After applying the external strain to the PCF with the periodic surface micro-ridges, periodic modulation of refractive index based on the photoelastic effect is induced resulting in the formation of the PCF-based LPG. Increasing the applied strain successfully improves the extinction ratio of the resonant peak of the PCF-based LPG without the resonant wavelength shift. We also measured the transmission characteristics of the PCF-based LPG with variations in temperature and ambient index.

The scatter of obliquely incident plane waves from a corrugated conducting surface

NASA Technical Reports Server (NTRS)

Levine, D. N.

1975-01-01

A physical optics solution is presented for the scattering of plane waves from a perfectly conducting corrugated surface in the case of waves incident from an arbitrary direction and for an observer far from the surface. This solution was used to compute the radar cross section of the surface in the case of backscatter from irregular (i.e., stochastic) corrugations and to point out a correction to the literature on this problem. A feature of the solution is the occurrence of singularities in the scattered fields which appear to be a manifestation of focussing by the surface at its stationary points. Whether or not the singularities occur in the solution depends on the manner in which one restricts the analysis to the far field.

MR imaging with remote reception using a coil array

NASA Astrophysics Data System (ADS)

Vazquez, F.; Marrufo, O.; Martin, R.; Rodriguez, A. O.

2012-10-01

A strategy for imaging a large field-of-view has recently been proposed applying remote detection with a waveguide and single loop coils. RF coils produce a traveling-wave propagating through the bore of the magnet, which is large enough so the cutoff frequency is below the Larmor frequency. This assumption also considers that a human subject inside the magnet bore. We applied the travelling-wave concept to generate images of a human leg at 3 Tesla. Two circular-shaped coils were used as the reception device and a whole-body coil was used for transmission. Images showed a good signal-to-noise ratio along the entire leg. This experimental results contradict the assumption that a whole-body 7T/65cm imager or higher was necessary to generate images with this approach.

Response of corrugated fiberboard to moisture flow : a 3-D finite element transient nonlinear analysis

Treesearch

Adeeb A. Rahman; Thomas J. Urbanik; Mustafa Mahamid

2003-01-01

Collapse of fiberboard packaging boxes, in the shipping industry, due to rise in humidity conditions is common and very costly. A 3D FE nonlinear model is developed to predict the moisture flow throughout a corrugated packaging fiberboard sandwich structure. The model predicts how the moisture diffusion will permeate through the layers of a fiberboard (medium and...

Effect of discrete track support by sleepers on rail corrugation at a curved track

NASA Astrophysics Data System (ADS)

Jin, X. S.; Wen, Z. F.

2008-08-01

The paper investigates into the effect of discrete track support by sleepers on the initiation and development of rail corrugation at a curved track when a railway vehicle passes through using a numerical method. The numerical method considers a combination of Kalker's rolling contact theory with non-Hertzian form, a linear frictional work model and a dynamics model of a half railway vehicle coupled with the curved track. The half-vehicle has a two-axle bogie and doubled suspension systems. It is treated as a full dynamic rigid multi-body model. In the track model, an Euler beam is used to model the rail, and the discrete track support by sleepers moving backward with respect to the vehicle running direction is considered to simulate the effect of the discrete sleeper support on the wheels/rails in rolling contact when the vehicle moves on the track. The sleeper is treated as a rigid body and the ballast bed is replaced with equivalent mass bodies. The numerical analysis exams in detail the variations of wheel/rail normal loads, the creepages, and the rail wear volume along the curved track. Their variations are much concerned with the discrete track support. The numerical results show that the discrete track support causes the fluctuating of the normal loads and creepages at a few frequencies. These frequencies comprise the passing frequency of the sleepers and the excited track resonant frequencies, which are higher than the sleeper passing frequency. Consequently, rail corrugation with several wavelengths initiates and develops. Also the results show that the contact vibrating between the curved rails and the four wheels of the same bogie has different frequencies. In this way, the different key frequencies to be excited play an important role in the initiation and development of curved rail corrugation. Therefore, the corrugations caused by the four wheels of the same bogie present different wavelengths. The paper shows and discusses the depths of the initial corrugations caused by the four wheels of the same bogie, at the entering transition curve, the circle curve and the exit transition curve of the curved track, respectively.

Preliminary greenhouse design for a Martian colony: Structural, solar collection, and light distribution systems

NASA Technical Reports Server (NTRS)

1990-01-01

The design of a greenhouse that will be a component of a long-term habitat on Mars is presented. The greenhouse will be the primary food source for people stationed on Mars. The food will be grown in three identical underground modules, pressurized at 1 atm to allow a shirt-sleeve environment within the greenhouse. The underground location will support the structure, moderate the large environmental variations on the surface, and protect the crops from cosmic radiation. The design effort is concentrated on the outer structure and the lighting system for the greenhouse. The structure is inflatable and made of a Kevlar 49/Epoxy composite and a pipe-arched system that is corrugated to increase stiffness. This composite is pliable in an uncured state, which allows it to be efficiently packaged for transport. The lighting system consists of several flat-plate fiber optic solar collectors with dual-axis tracking systems that will continually track the sun. This design is modeled after the Himawari collector, which was designed by Dr. Kei Mori and is currently in use in Japan. The light will pass through Fresnel lenses that filter out undesirable wavelengths and send the light into the greenhouses by way of fiber optic cables. When the light arrives at the greenhouse, it is dispersed to the plants via a waveguide and diffuser system.

Design of 280 GHz feedhorn-coupled TES arrays for the balloon-borne polarimeter SPIDER

NASA Astrophysics Data System (ADS)

Hubmayr, Johannes; Austermann, Jason E.; Beall, James A.; Becker, Daniel T.; Benton, Steven J.; Bergman, A. Stevie; Bond, J. Richard; Bryan, Sean; Duff, Shannon M.; Duivenvoorden, Adri J.; Eriksen, H. K.; Filippini, Jeffrey P.; Fraisse, A.; Galloway, Mathew; Gambrel, Anne E.; Ganga, K.; Grigorian, Arpi L.; Gualtieri, Riccardo; Gudmundsson, Jon E.; Hartley, John W.; Halpern, M.; Hilton, Gene C.; Jones, William C.; McMahon, Jeffrey J.; Moncelsi, Lorenzo; Nagy, Johanna M.; Netterfield, C. B.; Osherson, Benjamin; Padilla, Ivan; Rahlin, Alexandra S.; Racine, B.; Ruhl, John; Rudd, T. M.; Shariff, J. A.; Soler, J. D.; Song, Xue; Ullom, Joel N.; Van Lanen, Jeff; Vissers, Michael R.; Wehus, I. K.; Wen, Shyang; Wiebe, D. V.; Young, Edward

2016-07-01

We describe 280 GHz bolometric detector arrays that instrument the balloon-borne polarimeter spider. A primary science goal of spider is to measure the large-scale B-mode polarization of the cosmic microwave background (cmb) in search of the cosmic-inflation, gravitational-wave signature. 280 GHz channels aid this science goal by constraining the level of B-mode contamination from galactic dust emission. We present the focal plane unit design, which consists of a 16x16 array of conical, corrugated feedhorns coupled to a monolithic detector array fabricated on a 150 mm diameter silicon wafer. Detector arrays are capable of polarimetric sensing via waveguide probe-coupling to a multiplexed array of transition-edge-sensor (TES) bolometers. The spider receiver has three focal plane units at 280 GHz, which in total contains 765 spatial pixels and 1,530 polarization sensitive bolometers. By fabrication and measurement of single feedhorns, we demonstrate 14.7° FHWM Gaussian-shaped beams with <1% ellipticity in a 30% fractional bandwidth centered at 280 GHz. We present electromagnetic simulations of the detection circuit, which show 94% band-averaged, single-polarization coupling efficiency, 3% reflection and 3% radiative loss. Lastly, we demonstrate a low thermal conductance bolometer, which is well-described by a simple TES model and exhibits an electrical noise equivalent power (NEP) = 2.6 x 10-17 W/√Hz, consistent with the phonon noise prediction.

Effect of section properties on load carrying capacity of 10m span precast concrete closed spandrel arch bridge with corrugated section

NASA Astrophysics Data System (ADS)

Ong, Chong Yong; Choong, Kok Keong; Miralimov, Mirzakhid

2017-10-01

Various precast concrete arch bridge systems have been developed since 1960's. The reinforced concrete section of these systems is solid rectangular which is not an efficient section. Inspired by the nature of banana tree trunk, a relatively new corrugated section of precast concrete arch bridge was introduced and patented in Malaysia in 2008. This folded plate section is an open section which tends to open under vehicular loading. Hence, effect of section properties on load carrying capacity of precast concrete closed spandrel arch bridge with corrugated section under vehicle loading is presented in this paper. The arch bridge model has a clear span of 10m with 2.5m, 3.0m and 3.5m clear rise. For the corrugated section dimension model, overall depth varies from 475mm to 575mm, top and bottom flange thickness varies from 135mm to 155mm and web thickness varies from 90mm to 120mm. Linear and non-linear computational analysis are carried out using 2D PLAXIS software (in longitudinal direction) and LUSAS software (in transverse direction). In longitudinal direction, the sagging moment in non-linear analysis increases approximately 18% compared to linear analysis for different rise span ratio. From the analysis results, as the rise of arch increases, the sagging moment and hogging moment increases, but the axial force decreases. Besides, as the overall depth of corrugated section increases, the internal forces of the arch also increase. In transverse direction, the maximum tensile stress of concrete at crown and haunch decreases as slenderness ratio increases.

Enhanced light out-coupling efficiency of organic light-emitting diodes with an extremely low haze by plasma treated nanoscale corrugation

NASA Astrophysics Data System (ADS)

Hwang, Ju Hyun; Lee, Hyun Jun; Shim, Yong Sub; Park, Cheol Hwee; Jung, Sun-Gyu; Kim, Kyu Nyun; Park, Young Wook; Ju, Byeong-Kwon

2015-01-01

Extremely low-haze light extraction from organic light-emitting diodes (OLEDs) was achieved by utilizing nanoscale corrugation, which was simply fabricated with plasma treatment and sonication. The haze of the nanoscale corrugation for light extraction (NCLE) corresponds to 0.21% for visible wavelengths, which is comparable to that of bare glass. The OLEDs with NCLE showed enhancements of 34.19% in current efficiency and 35.75% in power efficiency. Furthermore, the OLEDs with NCLE exhibited angle-stable electroluminescence (EL) spectra for different viewing angles, with no change in the full width at half maximum (FWHM) and peak wavelength. The flexibility of the polymer used for the NCLE and plasma treatment process indicates that the NCLE can be applied to large and flexible OLED displays.Extremely low-haze light extraction from organic light-emitting diodes (OLEDs) was achieved by utilizing nanoscale corrugation, which was simply fabricated with plasma treatment and sonication. The haze of the nanoscale corrugation for light extraction (NCLE) corresponds to 0.21% for visible wavelengths, which is comparable to that of bare glass. The OLEDs with NCLE showed enhancements of 34.19% in current efficiency and 35.75% in power efficiency. Furthermore, the OLEDs with NCLE exhibited angle-stable electroluminescence (EL) spectra for different viewing angles, with no change in the full width at half maximum (FWHM) and peak wavelength. The flexibility of the polymer used for the NCLE and plasma treatment process indicates that the NCLE can be applied to large and flexible OLED displays. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr06547f

The Cassie-Wenzel transition of fluids on nanostructured substrates: Macroscopic force balance versus microscopic density-functional theory.

PubMed

Tretyakov, Nikita; Papadopoulos, Periklis; Vollmer, Doris; Butt, Hans-Jürgen; Dünweg, Burkhard; Daoulas, Kostas Ch

2016-10-07

Classical density functional theory is applied to investigate the validity of a phenomenological force-balance description of the stability of the Cassie state of liquids on substrates with nanoscale corrugation. A bulk free-energy functional of third order in local density is combined with a square-gradient term, describing the liquid-vapor interface. The bulk free energy is parameterized to reproduce the liquid density and the compressibility of water. The square-gradient term is adjusted to model the width of the water-vapor interface. The substrate is modeled by an external potential, based upon the Lennard-Jones interactions. The three-dimensional calculation focuses on substrates patterned with nanostripes and square-shaped nanopillars. Using both the force-balance relation and density-functional theory, we locate the Cassie-to-Wenzel transition as a function of the corrugation parameters. We demonstrate that the force-balance relation gives a qualitatively reasonable description of the transition even on the nanoscale. The force balance utilizes an effective contact angle between the fluid and the vertical wall of the corrugation to parameterize the impalement pressure. This effective angle is found to have values smaller than the Young contact angle. This observation corresponds to an impalement pressure that is smaller than the value predicted by macroscopic theory. Therefore, this effective angle embodies effects specific to nanoscopically corrugated surfaces, including the finite range of the liquid-solid potential (which has both repulsive and attractive parts), line tension, and the finite interface thickness. Consistently with this picture, both patterns (stripes and pillars) yield the same effective contact angles for large periods of corrugation.

Interconnect Between a Waveguide and a Dielectric Waveguide Comprising an Impedance Matched Dielectric Lens

NASA Technical Reports Server (NTRS)

Decrossas, Emmanuel (Inventor); Chattopadhyay, Goutam (Inventor); Chahat, Nacer (Inventor); Tang, Adrian J. (Inventor)

2016-01-01

A lens for interconnecting a metallic waveguide with a dielectric waveguide is provided. The lens may be coupled a metallic waveguide and a dielectric waveguide, and minimize a signal loss between the metallic waveguide and the dielectric waveguide.

Spatial frequency maps of power flow in metamaterials and photonic crystals: Investigating backward-wave modes across the electromagnetic spectrum

NASA Astrophysics Data System (ADS)

Aghanejad, Iman; Markley, Loïc

2017-11-01

We present spatial frequency maps of power flow in metamaterials and photonic crystals in order to provide insights into their electromagnetic responses and further our understanding of backward power in periodic structures. Since 2001, many different structures across the electromagnetic spectrum have been presented in the literature as exhibiting an isotropic negative effective index. Although these structures all exhibit circular or spherical equifrequency contours that resemble those of left-handed media, here we show through k -space diagrams that the distribution of power in the spatial frequency domain can vary considerably across these structures. In particular, we show that backward power arises from high-order right-handed harmonics in photonic crystals, magnetodielectric crystals, and across the layers of coupled-plasmonic-waveguide metamaterials, while arising from left-handed harmonic pairs in split-ring resonator and wire composites, plasmonic crystals, and along the layers of coupled-plasmonic-waveguide metamaterials. We also show that the fishnet structure exhibits the same left-handed harmonic pairs as the latter group. These observations allow us to categorize different metamaterials according to their spatial spectral source of backward power and identify the mechanism behind negative refraction at a given interface. Finally, we discuss how k -space maps of power flow can be used to explain the high or low transmittance of power into different metamaterial or photonic crystal structures.

RF window assembly comprising a ceramic disk disposed within a cylindrical waveguide which is connected to rectangular waveguides through elliptical joints

DOEpatents

Tantawi, Sami G.; Dolgashev, Valery A.; Yeremian, Anahid D.

2016-03-15

A high-power microwave RF window is provided that includes a cylindrical waveguide, where the cylindrical waveguide includes a ceramic disk concentrically housed in a central region of the cylindrical waveguide, a first rectangular waveguide, where the first rectangular waveguide is connected by a first elliptical joint to a proximal end of the cylindrical waveguide, and a second rectangular waveguide, where the second rectangular waveguide is connected by a second elliptical joint to a distal end of the cylindrical waveguide.

Plasmonic Antenna Coupling for QWIPs

NASA Technical Reports Server (NTRS)

Hong, John

2007-01-01

In a proposed scheme for coupling light into a quantum-well infrared photodetector (QWIP), an antenna or an array of antennas made of a suitable metal would be fabricated on the face of what would otherwise be a standard QWIP. This or any such coupling scheme is required to effect polarization conversion: Light incident perpendicularly to the face is necessarily polarized in the plane of the face, whereas, as a matter of fundamental electrodynamics and related quantum selection rules, light must have a non-zero component of perpendicular polarization in order to be absorbed in the photodetection process. In a prior coupling scheme, gratings in the form of surface corrugations diffract normally gles, thereby imparting some perpendicular polarization. Unfortunately, the corrugation- fabrication process increases the overall nonuniformity of a large QWIP array. The proposed scheme is an alternative to the use of surface corrugations.

Experimental Demonstration of Longitudinal Beam Phase-Space Linearizer in a Free-Electron Laser Facility by Corrugated Structures

NASA Astrophysics Data System (ADS)

Deng, Haixiao; Zhang, Meng; Feng, Chao; Zhang, Tong; Wang, Xingtao; Lan, Taihe; Feng, Lie; Zhang, Wenyan; Liu, Xiaoqing; Yao, Haifeng; Shen, Lei; Li, Bin; Zhang, Junqiang; Li, Xuan; Fang, Wencheng; Wang, Dan; Couprie, Marie-emmanuelle; Lin, Guoqiang; Liu, Bo; Gu, Qiang; Wang, Dong; Zhao, Zhentang

2014-12-01

Removal of the undesired time-energy correlations in the electron beam is of paramount importance for efficient lasing of a high-gain free-electron laser. Recently, it has been theoretically and experimentally demonstrated that the longitudinal wakefield excited by the electrons themselves in a corrugated structure allows for precise control of the electron beam phase space. In this Letter, we report the first utilization of a corrugated structure as a beam linearizer in the operation of a seeded free-electron laser driven by a 140 MeV linear accelerator, where a gain of ˜10 000 over spontaneous emission was achieved at the second harmonic of the 1047 nm seed laser, and a free-electron laser bandwidth narrowing by 50% was observed, in good agreement with the theoretical expectations.

Enhanced light out-coupling efficiency of organic light-emitting diodes with an extremely low haze by plasma treated nanoscale corrugation.

PubMed

Hwang, Ju Hyun; Lee, Hyun Jun; Shim, Yong Sub; Park, Cheol Hwee; Jung, Sun-Gyu; Kim, Kyu Nyun; Park, Young Wook; Ju, Byeong-Kwon

2015-02-14

Extremely low-haze light extraction from organic light-emitting diodes (OLEDs) was achieved by utilizing nanoscale corrugation, which was simply fabricated with plasma treatment and sonication. The haze of the nanoscale corrugation for light extraction (NCLE) corresponds to 0.21% for visible wavelengths, which is comparable to that of bare glass. The OLEDs with NCLE showed enhancements of 34.19% in current efficiency and 35.75% in power efficiency. Furthermore, the OLEDs with NCLE exhibited angle-stable electroluminescence (EL) spectra for different viewing angles, with no change in the full width at half maximum (FWHM) and peak wavelength. The flexibility of the polymer used for the NCLE and plasma treatment process indicates that the NCLE can be applied to large and flexible OLED displays.

Effects of micro-structure on aerodynamics of Coccinella septempunctata elytra (ladybird) in forward flight as assessed via electron microscopy.

PubMed

Xiang, Jinwu; Liu, Kai; Li, Daochun; Du, Jianxun

2017-11-01

The effects of micro-structure on aerodynamics of Coccinella septempunctata (Coleoptera: Coccinellidae) elytra in forward flight were investigated. The micro-structure was examined by a scanning electron microscope and a digital microscope. Based on the experimental results, five elytron models were constructed to separately investigate the effects of the camber and the local corrugation in both leading edge and trailing edge on aerodynamics. Computational fluid dynamic simulations of five elytron models were conducted by solving the Reynolds-Averaged Navier-Stokes equations with the Reynolds number of 245. The results show that camber and the local corrugation in the leading edge play significant roles in improving the aerodynamic performance, while the local corrugation in the trailing edge has little effect on aerodynamics. Copyright © 2017 Elsevier Ltd. All rights reserved.

Buckling test of a 3-meter-diameter corrugated graphite-epoxy ring-stiffened cylinder

NASA Technical Reports Server (NTRS)

Davis, R. C.

1982-01-01

A three m diameter by three m long corrugated cylindrical shell with external stiffening rings was tested to failure by buckling. The corrugation geometry for the graphite epoxy composite cylinder wall was optimized to withstand a compressive load producing an ultimate load intensity of 157.6 kN/m without buckling. The test method used to produce the design load intensity was to mount the specimen as a cantilevered cylinder and apply a pure bending moment to the end. A load introduction problem with the specimen was solved by using the BOSOR 4 shell of revolution computer code to analyze the shell and attached loading fixtures. The cylinder test loading achieved was 101 percent of design ultimate, and the resulting mass per unit of shell wall area was 1.96 kg/sq m.

USSR Report, Transportation

DTIC Science & Technology

1984-12-21

During the years of gas- turbine engines, aviators encountered quite a few problems. Bearings in these engines were wearing out in 200 to 400 hours...and the time between overhaul of the GTD [gas- turbine engines] of that time de- pended precisely on their operation. Today bearings in aviation last...with vertical corrugating. The transverse bulkheads between holds Nos 2-4 also have vertical corrugating. The hull has been framed according to a

MTR BUILDING, TRA603. EAST SIDE. CAMERA FACING WEST. CORRUGATED IRON ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

MTR BUILDING, TRA-603. EAST SIDE. CAMERA FACING WEST. CORRUGATED IRON BUILDING MARKED WITH "X" IS TRA-651. TRA-626, TO ITS RIGHT, HOUSED COMPRESSOR EQUIPMENT FOR THE AIRCRAFT NUCLEAR PROPULSION PROGRAM. LATER, IT WAS USED FOR STORAGE. INL NEGATIVE NO. HD46-42-4. Mike Crane, Photographer, April 2005 - Idaho National Engineering Laboratory, Test Reactor Area, Materials & Engineering Test Reactors, Scoville, Butte County, ID

FE analysis of creep and hygroexpansion response of a corrugated fiberboard to a moisture flow : a transient nonlinear analysis

Treesearch

Adeeb A. Rahman; Thomas J. Urbanik; Mustafa Mahamid

2006-01-01

This paper presents a model using finite element method to study the response of a typical commercial corrugated fiberboard due to an induced moisture function at one side of the fiberboard. The model predicts how the moisture diffusion will permeate through the fiberboard’s layers(medium and liners) providing information on moisture content at any given point...

A rheological model for immersed corrugated elastic plates.

PubMed

Meier, D; Franklin, H; Predoi, M V; Rousseau, M; Izbicki, J L

2017-03-01

The influence of surface imperfections on the propagation of guided waves in an immersed elastic plate can be interpreted by means of a rheological model. The corrugated surface is modeled by a very thin interface, similar to a Jones spring model, which replaces the continuity boundary conditions at the liquid - corrugated solid-plate interface. As the surrounding liquid is considered to be perfect, only one complex stiffness is used for the model of Jones. The selection of the plate guided mode and the test frequency are motivated by the detectability and non-interference with other modes. The spring stiffness is obtained by a best fit procedure, between the analytical solution and the results obtained by the finite elements method (FEM). One way ensuring the agreement of the two approaches, rheological and FEM, is to consider angular resonances provided by the transmission coefficients. Small changes in the parameters of the roughness keep the positions of the angular resonances of the plate practically unchanged, while at the same time large variations of the half width of the transmission coefficient curve is observed. The effect of corrugation parameters on the guided modes in the plate can be predicted by using the rheological model with the deduced spring complex stiffness. Copyright © 2016. Published by Elsevier B.V.

Mitigation of Biofilm Formation on Corrugated Cardboard Fresh Produce Packaging Surfaces Using a Novel Thiazolidinedione Derivative Integrated in Acrylic Emulsion Polymers

PubMed Central

Brandwein, Michael; Al-Quntar, Abed; Goldberg, Hila; Mosheyev, Gregory; Goffer, Moshe; Marin-Iniesta, Fulgencio; López-Gómez, Antonio; Steinberg, Doron

2016-01-01

Various surfaces associated with the storage and packing of food are known to harbor distinct bacterial pathogens. Conspicuously absent among the plethora of studies implicating food packaging materials and machinery is the study of corrugated cardboard packaging, the worldwide medium for transporting fresh produce. In this study, we observed the microbial communities of three different store-bought fruits and vegetables, along with their analog cardboard packaging using high throughput sequencing technology. We further developed an anti-biofilm polymer meant to coat corrugated cardboard surfaces and mediate bacterial biofilm growth on said surfaces. Integration of a novel thiazolidinedione derivative into the acrylic emulsion polymers was assessed using Energy Dispersive X-ray Spectrometry (EDS) analysis and surface topography was visualized and quantified on corrugated cardboard surfaces. Biofilm growth was measured using q-PCR targeting the gene encoding 16s rRNA. Additionally, architectural structure of the biofilm was observed using SEM. The uniform integration of the thiazolidinedione derivative TZD-6 was confirmed, and it was determined via q-PCR to reduce biofilm growth by ~80% on tested surfaces. A novel and effective method for reducing microbial load and preventing contamination on food packaging is thereby proposed. PMID:26909074

Experimental investigation on the dynamic response of clamped corrugated sandwich plates subjected to underwater impulsive loadings

NASA Astrophysics Data System (ADS)

Huang, Wei; Zhang, Wei; Li, Dacheng; Hypervelocity Impact Research Center Team

2015-06-01

Corrugated sandwich plates are widely used in marine industry because such plates have high strength-to-weight ratios and blast resistance. The laboratory-scaled fluid-structure interaction experiments are performed to demonstrate the shock resistance of solid monolithic plates and corrugated sandwich plates by quantifying the permanent transverse deflection at mid-span of the plates as a function of impulsive loadings per areal mass. Sandwich structures with 6mm-thick and 10mm-thick 3003 aluminum corrugated core and 5A06 face sheets are compared with the 5A06 solid monolithic plates in this paper. The dynamic deformation of plates are captured with the the 3D digital speckle correlation method (DIC). The results affirm that sandwich structures show a 30% reduction in the maximum plate deflection compare with a monolithic plate of identical mass per unit area, and the peak value of deflection effectively reduced by increasing the thickness core. The failure modes of sandwich plates consists of core crushing, imprinting, stretch tearing of face sheets, bending and permanent deformation of entire structure with the increasing impulsive loads, and the failure mechanisms are analyzed with the postmortem panels and dynamic deflection history captured by cameras. National Natural Science Foundation of China (NO.: 11372088).

Anisotropic Strain Relaxation of Graphene by Corrugation on Copper Crystal Surfaces.

PubMed

Deng, Bing; Wu, Juanxia; Zhang, Shishu; Qi, Yue; Zheng, Liming; Yang, Hao; Tang, Jilin; Tong, Lianming; Zhang, Jin; Liu, Zhongfan; Peng, Hailin

2018-05-01

Corrugation is a ubiquitous phenomenon for graphene grown on metal substrates by chemical vapor deposition, which greatly affects the electrical, mechanical, and chemical properties. Recent years have witnessed great progress in controlled growth of large graphene single crystals; however, the issue of surface roughness is far from being addressed. Here, the corrugation at the interface of copper (Cu) and graphene, including Cu step bunches (CuSB) and graphene wrinkles, are investigated and ascribed to the anisotropic strain relaxation. It is found that the corrugation is strongly dependent on Cu crystallographic orientations, specifically, the packed density and anisotropic atomic configuration. Dense Cu step bunches are prone to form on loose packed faces due to the instability of surface dynamics. On an anisotropic Cu crystal surface, Cu step bunches and graphene wrinkles are formed in two perpendicular directions to release the anisotropic interfacial stress, as revealed by morphology imaging and vibrational analysis. Cu(111) is a suitable crystal face for growth of ultraflat graphene with roughness as low as 0.20 nm. It is believed the findings will contribute to clarifying the interplay between graphene and Cu crystal faces, and reducing surface roughness of graphene by engineering the crystallographic orientation of Cu substrates. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization of microwave plasma in a multicusp using 2D emission based tomography: Bessel modes and wave absorption

NASA Astrophysics Data System (ADS)

Rathore, Kavita; Bhattacharjee, Sudeep; Munshi, Prabhat

2017-06-01

A tomographic method based on the Fourier transform is used for characterizing a microwave plasma in a multicusp (MC), in order to obtain 2D distribution of plasma emissions, plasma (electron) density (Ne) and temperature (Te). The microwave plasma in the MC is characterized as a function of microwave power, gas pressure, and axial distance. The experimentally obtained 2D emission profiles show that the plasma emissions are generated in a circular ring shape. There are usually two bright rings, one at the plasma core and another near the boundary. The experimental results are validated using a numerical code that solves Maxwell's equations inside a waveguide filled with a plasma in a magnetic field, with collisions included. It is inferred that the dark and bright circular ring patterns are a result of superposition of Bessel modes (TE11 and TE21) of the wave electric field inside the plasma filled MC, which are in reasonable agreement with the plasma emission profiles. The tomographically obtained Ne and Te profiles indicate higher densities in the plasma core (˜1010 cm-3) and enhanced electron temperature in the ECR region (˜13 eV), which are in agreement with earlier results using a Langmuir probe and optical emission spectroscopy (OES) diagnostics.

A Microstrip Patch-Fed Short Backfire Antenna for the Tracking and Data Relay Satellite System-Continuation (TDRSS-C) Multiple Access (MA) Array

NASA Technical Reports Server (NTRS)

Nessel, James A.; Kory, Carol L.; Lambert, Kevin M.; Acosta, Roberto J.

2006-01-01

Short Backfire Antennas (SBAs) are widely utilized for mobile satellite communications, tracking, telemetry, and wireless local area network (WLAN) applications due to their compact structure and excellent radiation characteristics [1-3]. Typically, these SBA s consist of an excitation element (i.e., a half-wavelength dipole), a reflective bottom plane, a planar sub-reflector located above the "exciter", and an outer circular rim. This configuration is capable of achieving gains on the order of 13-15 dBi, but with relatively narrow bandwidths (approx.3%-5%), making it incompatible with the requirements of the next generation enhanced Tracking and Data Relay Satellite System-Continuation (TDRSS-C) Multiple Access (MA) array [1]. Several attempts have been made to enhance the bandwidth performance of the common dipole-fed SBA by employing various other feeding mechanisms (e.g., waveguide, slot) with moderate success [4-5]. In this paper, a novel method of using a microstrip patch is employed for the first time to excite an SBA. The patch element is fed via two H-shaped slots electromagnetically coupled to a broadband hybrid coupler to maintain a wide bandwidth, as well as provide for dual circular polarization capabilities.

Ultrathin efficient perovskite solar cells employing a periodic structure of a composite hole conductor for elevated plasmonic light harvesting and hole collection

NASA Astrophysics Data System (ADS)

Long, Mingzhu; Chen, Zefeng; Zhang, Tiankai; Xiao, Yubin; Zeng, Xiaoliang; Chen, Jian; Yan, Keyou; Xu, Jianbin

2016-03-01

We developed a molecule/polymer composite hole transporting material (HTM) with a periodic microstructure for morphology replication of a corrugated Au electrode, which in combination plays a dual role in the optical and electronic enhancement of high performance perovskite solar cells (PSCs). The electro-optics revealed that perovskite couldn't readily extinct the red light even though the thickness increased to 370 nm, but we found that the quasi periodic microstructure composite (PMC) HTM in combination with the conformal Au electrode could promote the absorption through the enhanced cavity effects, leading to comparable absorption even using much thinner perovskite (240 nm). We identified that the cavity was the combination of Fabry-Pérot interferometer and surface plasmonic resonance, with light harvesting enhancement through surface plasmon polariton or waveguide modes that propagate in the plane of the perovskite layer. On the other hand, the PMC HTM increased hole conductivity by one order of magnitude with respect to standard spiro-OMeTAD HTM due to molecular packing and self-assembly, embodying traceable hole mobility and density elevation up to 3 times, and thus the hysteresis was greatly avoided. Owing to dual optical and electronic enhancement, the PMC PSC afforded high efficiency PSC using as thin as 240 nm perovskite layer, delivering a Voc of 1.05 V, Jsc of 22.9 mA cm-2, FF of 0.736, and efficiency amounting to 17.7% PCE, the highest efficiency with ultrathin perovskite layer.We developed a molecule/polymer composite hole transporting material (HTM) with a periodic microstructure for morphology replication of a corrugated Au electrode, which in combination plays a dual role in the optical and electronic enhancement of high performance perovskite solar cells (PSCs). The electro-optics revealed that perovskite couldn't readily extinct the red light even though the thickness increased to 370 nm, but we found that the quasi periodic microstructure composite (PMC) HTM in combination with the conformal Au electrode could promote the absorption through the enhanced cavity effects, leading to comparable absorption even using much thinner perovskite (240 nm). We identified that the cavity was the combination of Fabry-Pérot interferometer and surface plasmonic resonance, with light harvesting enhancement through surface plasmon polariton or waveguide modes that propagate in the plane of the perovskite layer. On the other hand, the PMC HTM increased hole conductivity by one order of magnitude with respect to standard spiro-OMeTAD HTM due to molecular packing and self-assembly, embodying traceable hole mobility and density elevation up to 3 times, and thus the hysteresis was greatly avoided. Owing to dual optical and electronic enhancement, the PMC PSC afforded high efficiency PSC using as thin as 240 nm perovskite layer, delivering a Voc of 1.05 V, Jsc of 22.9 mA cm-2, FF of 0.736, and efficiency amounting to 17.7% PCE, the highest efficiency with ultrathin perovskite layer. Electronic supplementary information (ESI) available: XRD patterns corresponding to the perovskite; AFM images of 3D PMC HTM perovskite solar cells; performance statistics for 3D PMC HTM; ultraviolet photoelectron spectra (UPS) of HTMs on FTO. See DOI: 10.1039/c5nr05042a

A method for the measurement of dispersion curves of circumferential guided waves radiating from curved shells: experimental validation and application to a femoral neck mimicking phantom

NASA Astrophysics Data System (ADS)

Nauleau, Pierre; Minonzio, Jean-Gabriel; Chekroun, Mathieu; Cassereau, Didier; Laugier, Pascal; Prada, Claire; Grimal, Quentin

2016-07-01

Our long-term goal is to develop an ultrasonic method to characterize the thickness, stiffness and porosity of the cortical shell of the femoral neck, which could enhance hip fracture risk prediction. To this purpose, we proposed to adapt a technique based on the measurement of guided waves. We previously evidenced the feasibility of measuring circumferential guided waves in a bone-mimicking phantom of a circular cross-section of even thickness. The goal of this study is to investigate the impact of the complex geometry of the femoral neck on the measurement of guided waves. Two phantoms of an elliptical cross-section and one phantom of a realistic cross-section were investigated. A 128-element array was used to record the inter-element response matrix of these waveguides. This experiment was simulated using a custom-made hybrid code. The response matrices were analyzed using a technique based on the physics of wave propagation. This method yields portions of dispersion curves of the waveguides which were compared to reference dispersion curves. For the elliptical phantoms, three portions of dispersion curves were determined with a good agreement between experiment, simulation and theory. The method was thus validated. The characteristic dimensions of the shell were found to influence the identification of the circumferential wave signals. The method was then applied to the signals backscattered by the superior half of constant thickness of the realistic phantom. A cut-off frequency and some portions of modes were measured, with a good agreement with the theoretical curves of a plate waveguide. We also observed that the method cannot be applied directly to the signals backscattered by the lower half of varying thicknesses of the phantom. The proposed approach could then be considered to evaluate the properties of the superior part of the femoral neck, which is known to be a clinically relevant site.

A V-band wafer probe using ridge-trough waveguide

NASA Astrophysics Data System (ADS)

Godshalk, Edward M.

1991-12-01

A V-band (50-75 GHz) wafer probe is presented. The probe features a type of waveguide developed to allow transition from rectangular waveguide to coplanar waveguide. The waveguide consists of a ridge extending from the upper waveguide wall into a trough in the lower waveguide wall, and is known as the ridge-trough waveguide. A mathematical model is presented that allows important properties of the ridge-trough waveguide, such as the cutoff frequency and characteristic impedance, to be calculated.

Interaction potential between a helium atom and metal surfaces

NASA Technical Reports Server (NTRS)

Takada, Y.; Kohn, W.

1985-01-01

By employing an S-matrix theory for evanescent waves, the repulsive potential between a helium atom and corrugated metal surfaces has been calculated. P-wave interactions and intra-atomic correlation effects were found to be very important. The corrugation part of the interaction potential is much weaker than predicted by the effective-medium theory. Application to Cu, Ni, and Ag (110) surfaces gives good agreement with experiment without any adjustable parameters.

Computer analysis speeds corrugated horn design

NASA Technical Reports Server (NTRS)

Loefer, G. R.; Newton, J. M.; Schuchardt, J. M.; Dees, J. W.

1976-01-01

A computer analysis program is developed for selecting the optimum flare angle and horn length of a corrugated horn design, the horn diameter, and the radiation pattern, before resorting to machining operations. The calculated antenna pattern is best suited to narrowband designs, and averaging of the E and H planes is recommended for wideband work. The program language used is BASIC. Some design examples are provided with representative data, printouts, and a rundown of the equations programmed.

Enhanced response and sensitivity of self-corrugated graphene sensors with anisotropic charge distribution

PubMed Central

Yol Jeong, Seung; Jeong, Sooyeon; Won Lee, Sang; Tae Kim, Sung; Kim, Daeho; Jin Jeong, Hee; Tark Han, Joong; Baeg, Kang-Jun; Yang, Sunhye; Seok Jeong, Mun; Lee, Geon-Woong

2015-01-01

We introduce a high-performance molecular sensor using self-corrugated chemically modified graphene as a three dimensional (3D) structure that indicates anisotropic charge distribution. This is capable of room-temperature operation, and, in particular, exhibiting high sensitivity and reversible fast response with equilibrium region. The morphology consists of periodic, “cratered” arrays that can be formed by condensation and evaporation of graphene oxide (GO) solution on interdigitated electrodes. Subsequent hydrazine reduction, the corrugated edge area of the graphene layers have a high electric potential compared with flat graphene films. This local accumulation of electrons interacts with a large number of gas molecules. The sensitivity of 3D-graphene sensors significantly increases in the atmosphere of NO2 gas. The intriguing structures have several advantages for straightforward fabrication on patterned substrates, high-performance graphene sensors without post-annealing process. PMID:26053892

Rayleigh and Wood anomalies in the diffraction of acoustic waves from the periodically corrugated surface of an elastic medium

NASA Astrophysics Data System (ADS)

Maradudin, A. A.; Simonsen, I.

2016-05-01

By the use of the Rayleigh method we have calculated the angular dependence of the reflectivity and the efficiencies of several other diffracted orders when the periodically corrugated surface of an isotropic elastic medium is illuminated by a volume acoustic wave of shear horizontal polarization. These dependencies display the signatures of Rayleigh and Wood anomalies, usually associated with the diffraction of light from a metallic grating. The Rayleigh anomalies occur at angles of incidence at which a diffracted order appears or disappears; the Wood anomalies here are caused by the excitation of the shear horizontal surface acoustic waves supported by the periodically corrugated surface of an isotropic elastic medium. The dispersion curves of these waves in both the nonradiative and radiative regions of the frequency-wavenumber plane are calculated, and used in predicting the angles of incidence at which the Wood anomalies are expected to occur.

Study on transport packages used for food freshness preservation based on thermal analysis

NASA Astrophysics Data System (ADS)

Yu, Ying

2016-12-01

In recent time, as the Chinese consumption level increases, the consumption quantity of high-value fruits, vegetables and seafood products have been increasing year by year. As a consequence, the traffic volume of refrigerated products also increases yearly and the popularization degree of the cold-chain transportation enhances. A low-temperature environment should be guaranteed during transportation, thus there is about 40% of diesel oil should be consumed by the refrigerating system and the cold-chain transportation becomes very costly. This study aimed to explore methods that could reduce the cost of transport packages of refrigerated products. On the basis of the heat transfer theory and the fluid mechanics theory, the heat exchanging process of corrugated cases during the operation of refrigerating system was analyzed, the heat transfer process of corrugated cases and refrigerator van was theoretically analyzed and the heat balance equation of corrugated cases was constructed.

Simulation and analysis on ultrasonic testing for the cement grouting defects of the corrugated pipe

DOE Office of Scientific and Technical Information (OSTI.GOV)

Qingbang, Han; Ling, Chen; Changping, Zhu

2014-02-18

The defects exist in the cement grouting process of prestressed corrugated pipe may directly impair the bridge safety. In this paper, sound fields propagation in concrete structures with corrugated pipes and the influence of various different defects are simulated and analyzed using finite element method. The simulation results demonstrate a much complex propagation characteristic due to multiple reflection, refraction and scattering, where the scattering signals caused by metal are very strong, while the signals scattered by an air bubble are weaker. The influence of defect both in time and frequency domain are found through deconvolution treatment. In the time domain,more » the deconvolution signals correspond to larger defect display a larger head wave amplitude and shorter arrive time than those of smaller defects; in the frequency domain, larger defect also shows a stronger amplitude, lower center frequency and lower cutoff frequency.« less

Two-phase flow patterns in adiabatic and diabatic corrugated plate gaps

NASA Astrophysics Data System (ADS)

Polzin, A.-E.; Kabelac, S.; de Vries, B.

2016-09-01

Correlations for two-phase heat transfer and pressure drop can be improved considerably, when they are adapted to specific flow patterns. As plate heat exchangers find increasing application as evaporators and condensers, there is a need for flow pattern maps for corrugated plate gaps. This contribution presents experimental results on flow pattern investigations for such a plate heat exchanger background, using an adiabatic visualisation setup as well as a diabatic setup. Three characteristic flow patterns were observed in the considered range of two-phase flow: bubbly flow, film flow and slug flow. The occurrence of these flow patterns is a function of mass flux, void fraction, fluid properties and plate geometry. Two different plate geometries having a corrugation angle of 27° and 63°, respectively and two different fluids (water/air and R365mfc liquid/vapor) have been analysed. A flow pattern map using the momentum flux is presented.

Vibroacoustic Characterization of Corrugated-Core and Honeycomb-Core Sandwich Panels

NASA Technical Reports Server (NTRS)

Allen, Albert; Schiller, Noah

2016-01-01

The vibroacoustic characteristics of two candidate launch vehicle fairing structures, corrugated- core and honeycomb-core sandwich designs, were studied. The study of these structures has been motivated by recent risk reduction efforts focused on mitigating high noise levels within the payload bays of large launch vehicles during launch. The corrugated-core sandwich concept is of particular interest as a dual purpose structure due to its ability to harbor resonant noise control systems without appreciably adding mass or taking up additional volume. Specifically, modal information, wavelength dispersion, and damping were determined from a series of vibrometer measurements and subsequent analysis procedures carried out on two test panels. Numerical and analytical modeling techniques were also used to assess assumed material properties and to further illuminate underlying structural dynamic aspects. Results from the tests and analyses described herein may serve as a reference for additional vibroacoustic studies involving these or similar structures.

Electrodeposited Ni-Based Magnetic Mesoporous Films as Smart Surfaces for Atomic Layer Deposition: An "All-Chemical" Deposition Approach toward 3D Nanoengineered Composite Layers.

PubMed

Zhang, Jin; Quintana, Alberto; Menéndez, Enric; Coll, Mariona; Pellicer, Eva; Sort, Jordi

2018-05-02

Mesoporous Ni and Cu-Ni (Cu 20 Ni 80 and Cu 45 Ni 55 in at. %) films, showing a three-dimensional (3D) porous structure and tunable magnetic properties, are prepared by electrodeposition from aqueous surfactant solutions using micelles of P-123 triblock copolymer as structure-directing entities. Pores between 5 and 30 nm and dissimilar space arrangements (continuous interconnected networks, circular pores, corrugated mesophases) are obtained depending on the synthetic conditions. X-ray diffraction studies reveal that the Cu-Ni films have crystallized in the face-centered cubic structure, are textured, and exhibit certain degree of phase separation, particularly those with a higher Cu content. Atomic layer deposition (ALD) is used to conformally coat the mesopores of Cu 20 Ni 80 film with amorphous Al 2 O 3 , rendering multiphase "nano-in-meso" metal-ceramic composites without compromising the ferromagnetic response of the metallic scaffold. From a technological viewpoint, these 3D nanoengineered composite films could be appealing for applications like magnetically actuated micro/nanoelectromechanical systems (MEMS/NEMS), voltage-driven magneto-electric devices, capacitors, or as protective coatings with superior strength and tribological performance.

Corrugated outer sheath gas-insulated transmission line

DOEpatents

Kemeny, George A.; Cookson, Alan H.

1981-01-01

A gas-insulated transmission line includes two transmission line sections each of which are formed of a corrugated outer housing enclosing an inner high-voltage conductor disposed therein, with insulating support means supporting the inner conductor within the outer housing and an insulating gas providing electrical insulation therebetween. The outer housings in each section have smooth end sections at the longitudinal ends thereof which are joined together by joining means which provide for a sealing fixed joint.

Particle trap to sheath non-binding contact for a gas-insulated transmission line having a corrugated outer conductor

DOEpatents

Fischer, William H.

1984-04-24

A non-binding particle trap to outer sheath contact for use in gas insulated transmission lines having a corrugated outer conductor. The non-binding feature of the contact according to the teachings of the invention is accomplished by having a lever arm rotatably attached to a particle trap by a pivot support axis disposed parallel to the direction of travel of the inner conductor/insulator/particle trap assembly.

Ultrathin Organic Solar Cells with a Power Conversion Efficiency of Over ≈13.0%, Based on the Spatial Corrugation of the Metal Electrode-Cathode Fabry-Perot Cavity.

PubMed

In, Sungjun; Park, Namkyoo

2018-04-01

The application of nanophotonic structures for organic solar cells (OSCs) is quite popular and successful, and has led to increased optical absorption, better spectral overlap with solar irradiances, and improved charge collection. Significant improvements in the power conversion efficiency (PCE) have also been reported, exceeding 11%. Nonetheless, with the given material properties of OSCs with low optical absorption, narrow spectrum, short transport length of carriers, and nonuniform photocarrier generations resulting from the nanophotonic structure, the PCE of single-junction OSCs has been stagnant over the past few years, at a barrier of 12%. Here, an ultrathin inverted OSC structure with the highest efficiency of ≈13.0%, while being made from widely used organic materials, is demonstrated. By introducing a smooth spatial corrugation to the vertical plasmonic cavity enclosing the active layer, in-plane propagation modes and hybridized Fabry-Perot cavity modes inside the corrugated cavity are derived to achieve an ultralow Q , uniform coverage of optical absorption, in addition to uniform photocarrier generation and transport. As the first demonstration of ultra-broadband absorption with the introduction of spatial corrugation to the ultrathin metal film electrode-cathode Fabry-Perot cavity, future applications of the same concept in other light-harvesting devices utilizing different materials and structures are expected.

Method and apparatus for preventing cyclotron breakdown in partially evacuated waveguide

DOEpatents

Moeller, Charles P.

1987-01-01

Cyclotron breakdown is prevented in a partially evacuated waveguide by providing a section of waveguide having an axial cut therein in order to apply a potential across the two halves of the waveguide. This section is positioned in the waveguide crossing the area of electron cyclotron resonance. The potential applied across the waveguide halves is used to deflect seed electrons into the wall of the waveguide in order to prevent ionization of gas molecules and creation of more electron ion pairs which would result in cyclotron breakdown. Support means is also disclosed for electrically isolating the waveguide halves and transition means is provided between the section of the waveguide with the axial cut and the solid waveguide at either end thereof.

Evaluation of slot-to-slot coupling between dielectric slot waveguides and metal-insulator-metal slot waveguides.

PubMed

Kong, Deqing; Tsubokawa, Makoto

2015-07-27

We numerically analyzed the power-coupling characteristics between a high-index-contrast dielectric slot waveguide and a metal-insulator-metal (MIM) plasmonic slot waveguide as functions of structural parameters. Couplings due mainly to the transfer of evanescent components in two waveguides generated high transmission efficiencies of 62% when the slot widths of the two waveguides were the same and 73% when the waveguides were optimized by slightly different widths. The maximum transmission efficiency in the slot-to-slot coupling was about 10% higher than that in the coupling between a normal slab waveguide and an MIM waveguide. Large alignment tolerance of the slot-to-slot coupling was also proved. Moreover, a small gap inserted into the interface between two waveguides effectively enhances the transmission efficiency, as in the case of couplings between a normal slab waveguide and an MIM waveguide. In addition, couplings with very wideband transmissions over a wavelength region of a few hundred nanometers were validated.

Slotted Polyimide-Aerogel-Filled-Waveguide Arrays

NASA Technical Reports Server (NTRS)

Rodriguez-Solis, Rafael A.; Pacheco, Hector L.; Miranda, Felix A.; Meador, Mary Ann B.

2013-01-01

Polyimide aerogels were considered to serve as a filling for millimeter-wave waveguides. While these waveguides present a slightly higher loss than hollow waveguides, they have less losses than Duroid substrate integrated waveguides (less than 0.15 dB at Ka-band, in a 20 mm section), and exhibit an order of magnitude of mass reduction when compared to commercial waveguides. A Ka-band slotted aerogel-filled-waveguide array was designed, which provided the same gain (9 dBi) as its standard waveguide counterpart, and a slotted aerogel-filled-waveguide array using folded-slots was designed for comparison, obtaining a gain of 9 dB and a bandwidth of 590 MHz.

Competition and evolution of dielectric waveguide mode and plasmonic waveguide mode

NASA Astrophysics Data System (ADS)

Yuan, Sheng-Nan; Fang, Yun-Tuan

2017-10-01

In order to study the coupling and evolution law of the waveguide mode and two plasmonic surface modes, we construct a line defect waveguide based on hexagonal honeycomb plasmonic photonic crystal. Through adjusting the radius of the edge dielectric rods, the competition and evolution behaviors occur between dielectric waveguide mode and plasmonic waveguide mode. There are three status: only plasmonic waveguide modes occur for rA < 0.09a; only dielectric waveguide modes occur for rA > 0.25a; two kinds of modes coexist for 0.09a < rA < 0.25a. The plasmonic waveguide mode has advantages in achieving slow light.

Explosion resistant insulator and method of making same

DOEpatents

Meyer, Jeffry R.; Billings, Jr., John S.; Spindle, Harvey E.; Hofmann, Charles F.

1983-01-01

An electrical insulator assembly and method of manufacturing same, having a generally cylindrical or conical body portion formed of a breakable cast solid insulation system and a reinforcing member having a corrugated configuration and formed of a web or mesh type reinforcing fabric. When the breakable body member has been broken, the corrugated configured reinforcing web member provides a path of escape for pressurized insulating fluid while limiting the movement of body member fragments in the direction of escape of the pressurized fluid.

Coolant mass flow equalizer for nuclear fuel

DOEpatents

Betten, Paul R.

1978-01-01

The coolant mass flow distribution in a liquid metal cooled reactor is enhanced by restricting flow in sub-channels defined in part by the peripheral fuel elements of a fuel assembly. This flow restriction, which results in more coolant flow in interior sub-channels, is achieved through the use of a corrugated liner positioned between the bundle of fuel elements and the inner wall of the fuel assembly coolant duct. The corrugated liner is expandable to accommodate irradiation induced growth of fuel assembly components.

Design and measurement of a TE{sub 13} input converter for high order mode gyrotron travelling wave amplifiers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Yan; Liu, Guo, E-mail: liuguo@uestc.edu.cn; Shu, Guoxiang

2016-03-15

A technique to launch a circular TE{sub 13} mode to interact with the helical electron beam of a gyrotron travelling wave amplifier is proposed and verified by simulation and cold test in this paper. The high order (HOM) TE{sub 13} mode is excited by a broadband Y-type power divider with the aid of a cylindrical waveguide system. Using grooves and convex strips loaded at the lateral planes of the output cylindrical waveguide, the electric fields of the potential competing TE{sub 32} and TE{sub 71} modes are suppressed to allow the transmission of the dominant TE{sub 13} mode. The converter performancemore » for different structural dimensions of grooves and convex strips is studied in detail and excellent results have been achieved. Simulation predicts that the average transmission is ∼−1.8 dB with a 3 dB bandwidth of 7.2 GHz (91.5–98.7 GHz) and port reflection is less than −15 dB. The conversion efficiency to the TE{sub 32} and TE{sub 71} modes are, respectively, under −15 dB and −24 dB in the operating frequency band. Such an HOM converter operating at W-band has been fabricated and cold tested with the radiation boundary. Measurement from the vector network analyzer cold test and microwave simulations show a good reflection performance for the converter.« less

Characterization of the polarization and frequency selective bolometric detector architecture

NASA Astrophysics Data System (ADS)

Leong, Jonathan Ryan Kyoung Ho

2009-01-01

The Cosmic Microwave Background (CMB) has been a wonderful probe of fundamental physics and cosmology. In the future, we look towards using the polarization information encoded in the CMB for investigating the gravity waves generated by inflation. This is a daunting task as it requires orders of magnitude increases in sensitivity as well as close attention to systematic rejection and astrophysical foreground removal. We have characterized a novel detector architecture which is aimed at making these leaps towards gravity wave detection in the CMB. These detectors are called the Polarization and Frequency Selective Bolometers (PFSBs). They attempt to use all the available photon information incident on a single pixel by selecting out the two orthogonal polarizations and multiple frequency bands into separately stacked detectors in a smooth-walled waveguide. This approach is inherently multimoded and thus solves problems with downlink and readout throughput by catching more photons per detector at the higher frequencies where the number of detectors required is prohibitively large. We have found that the PFSB architecture requires the use of a square cross-section waveguide. A simulation we developed has illuminated the fact that the curved field lines of the higher order modes can be eliminated by degeneracies which exist only for a square guide and not a circular one. In the square guide configuration, the PFSBs show good band selection and polarization efficiency to a level of about 90% over the beam out to at least 20° from on-axis.

Multimode Directional Coupler

NASA Technical Reports Server (NTRS)

Simons, Rainee N. (Inventor); Wintucky, Edwin G. (Inventor)

2016-01-01

A multimode directional coupler is provided. In some embodiments, the multimode directional coupler is configured to receive a primary signal and a secondary signal at a first port of a primary waveguide. The primary signal is configured to propagate through the primary waveguide and be outputted at a second port of the primary waveguide. The multimode directional coupler also includes a secondary waveguide configured to couple the secondary signal from the primary waveguide with no coupling of the primary signal into the secondary waveguide. The secondary signal is configured to propagate through the secondary waveguide and be outputted from a port of the secondary waveguide.

Photonic Waveguide Choke Joint with Absorptive Loading

NASA Technical Reports Server (NTRS)

Wollack, Edward J. (Inventor); U-Yen, Kongpop (Inventor); Chuss, David T. (Inventor)

2016-01-01

A photonic waveguide choke includes a first waveguide flange member having periodic metal tiling pillars, a dissipative dielectric material positioned within an area between the periodic metal tiling pillars and a second waveguide flange member disposed to be coupled with the first waveguide flange member and in spaced-apart relationship separated by a gap. The first waveguide flange member has a substantially smooth surface, and the second waveguide flange member has an array of two-dimensional pillar structures formed therein.

Combined action of corrugation and Weibel instabilities from electron-beam interaction with laser-irradiated plasma

NASA Astrophysics Data System (ADS)

Bai, Yafeng; Tian, Ye; Zhang, Zhijun; Cao, Lihua; Liu, Jiansheng

2018-03-01

The combined action of corrugation and Weibel instabilities was experimentally observed in the interaction between energetic electrons and a laser-irradiated insulated target. The energetic electron beam, driven by an ultrashort laser pulse, splits into filaments with a diameter of ˜10 μm while traversing an insulated target, owing to the corrugation instability. The filaments continued to split into thinner filaments owing to the Weibel instability if a preplasma was induced by a heating beam on the rear side of the target. When the time delay between the heating beam and electron beam was larger than 1 ps, a merging of the current filaments was observed. The characteristic filamentary structures disappeared when the time delay between the two beams was larger than 3 ps. A simplified model was developed to analyze this process; the obtained results were in good agreement with the experiment. Two-dimensional particle-in-cell simulations supported our analysis and reproduced the filamentation of the electron beam inside the plasma.

Stacked Corrugated Horn Rings

NASA Technical Reports Server (NTRS)

Sosnowski, John B.

2010-01-01

This Brief describes a method of machining and assembly when the depth of corrugations far exceeds the width and conventional machining is not practical. The horn is divided into easily machined, individual rings with shoulders to control the depth. In this specific instance, each of the corrugations is identical in profile, and only differs in diameter and outer profile. The horn is segmented into rings that are cut with an interference fit (zero clearance with all machining errors biased toward contact). The interference faces can be cut with a reverse taper to increase the holding strength of the joint. The taper is a compromise between the interference fit and the clearance of the two faces during assembly. Each internal ring is dipped in liquid nitrogen, then nested in the previous, larger ring. The ring is rotated in the nest until the temperature of the two parts equalizes and the pieces lock together. The resulting assay is stable, strong, and has an internal finish that cannot be achieved through other methods.

Helical plasma thruster

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beklemishev, A. D., E-mail: bekl@bk.ru

2015-10-15

A new scheme of plasma thruster is proposed. It is based on axial acceleration of rotating magnetized plasmas in magnetic field with helical corrugation. The idea is that the propellant ionization zone can be placed into the local magnetic well, so that initially the ions are trapped. The E × B rotation is provided by an applied radial electric field that makes the setup similar to a magnetron discharge. Then, from the rotating plasma viewpoint, the magnetic wells of the helically corrugated field look like axially moving mirror traps. Specific shaping of the corrugation can allow continuous acceleration of trapped plasma ionsmore » along the magnetic field by diamagnetic forces. The accelerated propellant is expelled through the expanding field of magnetic nozzle. By features of the acceleration principle, the helical plasma thruster may operate at high energy densities but requires a rather high axial magnetic field, which places it in the same class as the VASIMR{sup ®} rocket engine.« less

Sliding states of a soft-colloid cluster crystal: Cluster versus single-particle hopping

NASA Astrophysics Data System (ADS)

Rossini, Mirko; Consonni, Lorenzo; Stenco, Andrea; Reatto, Luciano; Manini, Nicola

2018-05-01

We study a two-dimensional model for interacting colloidal particles which displays spontaneous clustering. Within this model we investigate the competition between the pinning to a periodic corrugation potential and a sideways constant pulling force which would promote a sliding state. For a few sample particle densities and amplitudes of the periodic corrugation potential we investigate the depinning from the statically pinned to the dynamically sliding regime. This sliding state exhibits the competition between a dynamics where entire clusters are pulled from a minimum to the next and a dynamics where single colloids or smaller groups leave a cluster and move across the corrugation energy barrier to join the next cluster downstream in the force direction. Both kinds of sliding states can occur either coherently across the entire sample or asynchronously: the two regimes result in different average mobilities. Finite temperature tends to destroy separate sliding regimes, generating a smoother dependence of the mobility on the driving force.

On the Stability of Shocks with Particle Pressure

NASA Astrophysics Data System (ADS)

Finazzi, Stefano; Vietri, Mario

2008-11-01

We perform a linear stability analysis for corrugations of a Newtonian shock, with particle pressure included, for an arbitrary diffusion coefficient. We study first the dispersion relation for homogeneous media, showing that, besides the conventional pressure waves and entropy/vorticity disturbances, two new perturbation modes exist, dominated by the particles' pressure and damped by diffusion. We show that, due to particle diffusion into the upstream region, the fluid will be perturbed also upstream; we treat these perturbation in the short-wavelength (WKBJ) regime. We then show how to construct a corrugational mode for the shock itself, one, that is, where the shock executes free oscillations (possibly damped or growing) and sheds perturbations away from itself; this global mode requires the new modes. Then, using the perturbed Rankine-Hugoniot conditions, we show that this leads to the determination of the corrugational eigenfrequency. We solve numerically the equations for the eigenfrequency in the WKBJ regime for the models of Amato & Blasi, showing that they are stable. We then discuss the differences between our treatment and previous work.

Integrated current collector and catalyst support

DOEpatents

Bregoli, Lawrence J.

1985-10-22

An integrated current collecting electrode for a molten carbonate fuel cell includes a corrugated metal conductive strip positioned in contact with a catalyst layer. The corrugations of the metal strip form a plurality of gas channels immediately adjacent the surface of the catalyst through which a reactant gas flows. Each channel is filled with a particulate material to maintain separation between the metal strip and the catalyst in ensuring gas channel integrity. The catalyst may be in the form of a compacted, particulate material provided the particle size of the material within the gas channels is larger than that of the catalyst particles to prevent catalyst migration to the metal conductor and provide reactant gas access to the catalyst layer. The gas channels formed by the corrugations of the metal strip are arranged in an offset pattern along the direction of gas flow for improved reactant gas distribution to the catalyst layer. The particulate material positioned within the gas flow channels may be a ceramic conductor such as a perovskite or a spinel for enhanced current collection.

Integrated current collector and catalyst support

DOEpatents

Bregoli, L.J.

1984-10-17

An integrated current collecting electrode for a molten carbonate fuel cell includes a corrugated metal conductive strip positioned in contact with a catalyst layer. The corrugations of the metal strip form a plurality of gas channels immediately adjacent the surface of the catalyst through which a reactant gas flows. Each channel is filled with a particulate material to maintain separation between the metal strip and the catalyst in ensuring gas channel integrity. The catalyst may be in the form of a compacted, particulate material provided the particle size of the material within the gas channels is larger than that of the catalyst particles to prevent catalyst migration to the metal conductor and provide reactant gas access to the catalyst layer. The gas channels formed by the corrugations of the metal strip are arranged in an offset pattern along the direction of gas flow for improved reactant gas distribution to the catalyst layer. The particulate material positioned within the gas flow channels may be a ceramic conductor such as a perovskite or a spinel for enhanced current collection.

Acoustic one-way mode conversion and transmission by sonic crystal waveguides

NASA Astrophysics Data System (ADS)

Ouyang, Shiliang; He, Hailong; He, Zhaojian; Deng, Ke; Zhao, Heping

2016-09-01

We proposed a scheme to achieve one-way acoustic propagation and even-odd mode switching in two mutually perpendicular sonic crystal waveguides connected by a resonant cavity. The even mode in the entrance waveguide is able to switch to the odd mode in the exit waveguide through a symmetry match between the cavity resonant modes and the waveguide modes. Conversely, the odd mode in the exit waveguide is unable to be converted into the even mode in the entrance waveguide as incident waves and eigenmodes are mismatched in their symmetries at the waveguide exit. This one-way mechanism can be applied to design an acoustic diode for acoustic integration devices and can be used as a convertor of the acoustic waveguide modes.

A semi-analytical beam model for the vibration of railway tracks

NASA Astrophysics Data System (ADS)

Kostovasilis, D.; Thompson, D. J.; Hussein, M. F. M.

2017-04-01

The high frequency dynamic behaviour of railway tracks, in both vertical and lateral directions, strongly affects the generation of rolling noise as well as other phenomena such as rail corrugation. An improved semi-analytical model of a beam on an elastic foundation is introduced that accounts for the coupling of the vertical and lateral vibration. The model includes the effects of cross-section asymmetry, shear deformation, rotational inertia and restrained warping. Consideration is given to the fact that the loads at the rail head, as well as those exerted by the railpads at the rail foot, may not act through the centroid of the section. The response is evaluated for a harmonic load and the solution is obtained in the wavenumber domain. Results are presented as dispersion curves for free and supported rails and are validated with the aid of a Finite Element (FE) and a waveguide finite element (WFE) model. Closed form expressions are derived for the forced response, and validated against the WFE model. Track mobilities and decay rates are presented to assess the potential implications for rolling noise and the influence of the various sources of vertical-lateral coupling. Comparison is also made with measured data. Overall, the model presented performs very well, especially for the lateral vibration, although it does not contain the high frequency cross-section deformation modes. The most significant effects on the response are shown to be the inclusion of torsion and foundation eccentricity, which mainly affect the lateral response.

Electron Bernstein Wave Emission Studies on the TJ-II Stellarator

DOE Office of Scientific and Technical Information (OSTI.GOV)

Caughman, John B; Fernandez, A.; Cappa, A.

2009-01-01

Electron Bernstein Wave (EBW) heating is important for high-beta plasma experiments and will be used for heating over-dense plasmas on TJ-II. TJ-II is a medium sized Heliac operating at CIEMAT in Madrid, whose plasmas are created and heated by ECH via two 300 kW gyrotrons at second harmonic X-mode (53.2 GHz), with additional heating provided by two neutral beam injectors. Theoretical work has shown that the most suitable scheme for launching EBWs in TJ-II is O-X-B mode conversion, which has acceptable heating efficiency for central densities above 1.2 x 1019 m-3.[1] A system based on a 28 GHz-100ms diode gyrotronmore » will be used to deliver 300 kW through a corrugated waveguide. The microwave heating beam will be directed and focused by a steering mirror located inside the vacuum vessel. Prior to the heating experiments, measurement of the thermal EBW emission (EBE) from the plasma is being made to help determine the optimum launch angle for EBW mode conversion, and also to provide an indication of the electron temperature evolution in over-dense plasmas. A dual-polarized quad-ridged broadband horn is used to measure the EBW emission and polarization at 28 GHz. Initial measurements indicate that the emission in under-dense plasmas corresponds to oblique electron cyclotron emission (ECE) and then converts to EBE when the plasma becomes over-dense during neutral beam injection.« less

Optical waveguide device with an adiabatically-varying width

DOEpatents

Watts,; Michael R. , Nielson; Gregory, N [Albuquerque, NM

2011-05-10

Optical waveguide devices are disclosed which utilize an optical waveguide having a waveguide bend therein with a width that varies adiabatically between a minimum value and a maximum value of the width. One or more connecting members can be attached to the waveguide bend near the maximum value of the width thereof to support the waveguide bend or to supply electrical power to an impurity-doped region located within the waveguide bend near the maximum value of the width. The impurity-doped region can form an electrical heater or a semiconductor junction which can be activated with a voltage to provide a variable optical path length in the optical waveguide. The optical waveguide devices can be used to form a tunable interferometer (e.g. a Mach-Zehnder interferometer) which can be used for optical modulation or switching. The optical waveguide devices can also be used to form an optical delay line.

Microwave Analysis with Monte Carlo Methods for ECH Transmission Lines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kaufman, Michael C.; Lau, Cornwall H.; Hanson, Gregory R.

A new code framework, MORAMC, is presented which model transmission line (TL) systems consisting of overmoded circular waveguide and other components including miter bends and transmission line gaps. The transmission line is modeled as a set of mode converters in series where each component is composed of one or more converters. The parametrization of each mode converter can account for the fabrication tolerances of physically realizable components. These tolerances as well as the precision to which these TL systems can be installed and aligned gives a practical limit to which the uncertainty of the microwave performance of the system canmore » be calculated. Because of this, Monte Carlo methods are a natural fit and are employed to calculate the probability distribution that a given TL can deliver a required power and mode purity. Several examples are given to demonstrate the usefulness of MORAMC in optimizing TL systems.« less

Microwave Analysis with Monte Carlo Methods for ECH Transmission Lines

DOE PAGES

Kaufman, Michael C.; Lau, Cornwall H.; Hanson, Gregory R.

2018-03-08

A new code framework, MORAMC, is presented which model transmission line (TL) systems consisting of overmoded circular waveguide and other components including miter bends and transmission line gaps. The transmission line is modeled as a set of mode converters in series where each component is composed of one or more converters. The parametrization of each mode converter can account for the fabrication tolerances of physically realizable components. These tolerances as well as the precision to which these TL systems can be installed and aligned gives a practical limit to which the uncertainty of the microwave performance of the system canmore » be calculated. Because of this, Monte Carlo methods are a natural fit and are employed to calculate the probability distribution that a given TL can deliver a required power and mode purity. Several examples are given to demonstrate the usefulness of MORAMC in optimizing TL systems.« less

Confining standing waves in optical corrals.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Babayan, Y.; McMahon, J. M.; Li, S.

2009-03-01

Near-field scanning optical microscopy images of solid wall, circular, and elliptical microscale corrals show standing wave patterns confined inside the structures with a wavelength close to that of the incident light. The patterns inside the corrals can be tuned by changing the size and material of the walls, the wavelength of incident light, and polarization direction for elliptical corrals. Finite-difference time-domain calculations of the corral structures agree with the experimental observations and reveal that the electric and magnetic field intensities are out of phase inside the corral. A theoretical modal analysis indicates that the fields inside the corrals can bemore » attributed to p- and s-polarized waveguide modes, and that the superposition of the propagating and evanescent modes can explain the phase differences between the fields. These experimental and theoretical results demonstrate that electromagnetic fields on a dielectric surface can be controlled in a predictable manner.« less

Microwave Analysis with Monte Carlo Methods for ECH Transmission Lines

NASA Astrophysics Data System (ADS)

Kaufman, M. C.; Lau, C.; Hanson, G. R.

2018-03-01

A new code framework, MORAMC, is presented which model transmission line (TL) systems consisting of overmoded circular waveguide and other components including miter bends and transmission line gaps. The transmission line is modeled as a set of mode converters in series where each component is composed of one or more converters. The parametrization of each mode converter can account for the fabrication tolerances of physically realizable components. These tolerances as well as the precision to which these TL systems can be installed and aligned gives a practical limit to which the uncertainty of the microwave performance of the system can be calculated. Because of this, Monte Carlo methods are a natural fit and are employed to calculate the probability distribution that a given TL can deliver a required power and mode purity. Several examples are given to demonstrate the usefulness of MORAMC in optimizing TL systems.

Terahertz Focusing and Polarization Control in Large-Area Bias-Free Semiconductor Emitters

NASA Astrophysics Data System (ADS)

Carthy, Joanna L.; Gow, Paul C.; Berry, Sam A.; Mills, Ben; Apostolopoulos, Vasilis

2018-03-01

We show that, when large-area multiplex terahertz semiconductor emitters, that work on diffusion currents and Schottky potentials, are illuminated by ultrashort optical pulses they can radiate a directional electromagnetic terahertz pulse which is controlled by the angular spectrum of the incident optical beam. Using the lens that focuses the incident near-infrared pulse, we have demonstrated THz emission focusing in free space, at the same point where the optical radiation would focus. We investigated the beam waist and Gouy phase shift of the THz emission as a function of frequency. We also show that the polarization profile of the emitted THz can be tailored by the metallic patterning on the semiconductor, demonstrating radial polarization when a circular emitter design is used. Our techniques can be used for fast THz beam steering and mode control for efficiently coupling to waveguides without the need for THz lenses or parabolic mirrors.

Normal and lateral Casimir forces between deformed plates

NASA Astrophysics Data System (ADS)

Emig, Thorsten; Hanke, Andreas; Golestanian, Ramin; Kardar, Mehran

2003-02-01

The Casimir force between macroscopic bodies depends strongly on their shape and orientation. To study this geometry dependence in the case of two deformed metal plates, we use a path-integral quantization of the electromagnetic field which properly treats the many-body nature of the interaction, going beyond the commonly used pairwise summation (PWS) of van der Waals forces. For arbitrary deformations we provide an analytical result for the deformation induced change in the Casimir energy, which is exact to second order in the deformation amplitude. For the specific case of sinusoidally corrugated plates, we calculate both the normal and the lateral Casimir forces. The deformation induced change in the Casimir interaction of a flat and a corrugated plate shows an interesting crossover as a function of the ratio of the mean plate distance H to the corrugation length λ: For λ≪H we find a slower decay ˜H-4, compared to the H-5 behavior predicted by PWS which we show to be valid only for λ≫H. The amplitude of the lateral force between two corrugated plates which are out of registry is shown to have a maximum at an optimal wavelength of λ≈2.5 H. With increasing H/λ≳0.3 the PWS approach becomes a progressively worse description of the lateral force due to many-body effects. These results may be of relevance for the design and operation of novel microelectromechanical systems (MEMS) and other nanoscale devices.

Photonic crystal slab waveguides in moderate index contrast media: Generalized transverse Bragg waveguides

NASA Astrophysics Data System (ADS)

Burckel, David Bruce

One of the anticipated advantages of photonic crystal waveguides is the ability to tune waveguide dispersion and propagation characteristics to achieve desired properties. The majority of research into photonic crystal waveguides centers around high index contrast photonic crystal waveguides with complete in-plane bandgaps in the photonic crystal cladding. This work focuses on linear photonic crystal waveguides in moderate index materials, with insufficient index contrast to guarantee a complete in-plane bandgap. Using a technique called Interferometric Lithography (IL) as well as standard semiconductor processing steps, a process flow for creating large area (˜cm 2), linear photonic crystal waveguides in a spin-deposited photocurable polymer is outlined. The study of such low index contrast photonic crystal waveguides offers a unique opportunity to explore the mechanisms governing waveguide confinement and photonic crystal behavior in general. Results from two optical characterization experiments are provided. In the first set of experiments, rhodamine 590 organic laser dye was incorporated into the polymer prior to fabrication of the photonic crystal slab. Emission spectra from waveguide core modes exhibit no obvious spectral selectivity owing to variation in the periodicity or geometry of the photonic crystal. In addition, grating coupled waveguides were fabricated, and a single frequency diode laser was coupled into the waveguide in order to study the transverse mode structure. To this author's knowledge, the optical mode profile images are the first taken of photonic crystal slab waveguides, exhibiting both simple low order mode structure as well as complex high order mode structure inconsistent with effective index theory. However, no obvious correlation between the mode structure and photonic crystal period or geometry was evident. Furthermore, in both the laser dye-doped and grating coupled waveguides, low loss waveguiding was observed regardless of wavelength to period ratio. These optical results indicated a need for a deeper understanding of the confinement/guiding mechanisms in such waveguide structures. A simplification of the full 2-D problem to a more tractable "tilted 1-D" geometry led to the proposal of a new waveguide geometry, Generalized Transverse Bragg Waveguides (GTBW), as well as a new propagation mode characterized by spatial variation in both the transverse direction as well as the direction of propagation. GTBW demonstrate many of the same dispersion tunability traits exhibited in complete bandgap photonic crystal waveguides, under more modest fabrication demands, and moreover provide much insight into photonic crystal waveguide modes of all types. Generalized Transverse Bragg Waveguides are presented in terms of the standard physical properties associated with waveguides, including the dispersion relation, expressions for the spatial field profile, and the concepts of phase and group velocity. In addition, the proposal of at least one obvious application, semiconductor optical amplifiers, is offered.

Integration of a waveguide self-electrooptic effect device and a vertically coupled interconnect waveguide

DOEpatents

Vawter, G Allen [Corrales, NM

2008-02-26

A self-electrooptic effect device ("SEED") is integrated with waveguide interconnects through the use of vertical directional couplers. Light initially propagating in the interconnect waveguide is vertically coupled to the active waveguide layer of the SEED and, if the SEED is in the transparent state, the light is coupled back to the interconnect waveguide.

Simplified flangeless unisex waveguide coupler assembly

DOEpatents

Michelangelo, Dimartino; Moeller, Charles P.

1993-01-01

A unisex coupler assembly is disclosed capable of providing a leak tight coupling for waveguides with axial alignment of the waveguides and rotational capability. The sealing means of the coupler assembly are not exposed to RF energy, and the coupler assembly does not require the provision of external flanges on the waveguides. In a preferred embodiment, O ring seals are not used and the coupler assembly is, therefore, bakeable at a temperature up to about 150.degree. C. The coupler assembly comprises a split collar which clamps around the waveguides and a second collar which fastens to the split collar. The split collar contains an inner annular groove. Each of the waveguides is provided with an external annular groove which receives a retaining ring. The split collar is clamped around one of the waveguides with the inner annular groove of the split collar engaging the retaining ring carried in the external annular groove in the waveguide. The second collar is then slipped over the second waveguide behind the annular groove and retaining ring therein and the second collar is coaxially secured by fastening means to the split collar to draw the respective waveguides together by coaxial force exerted by the second collar against the retaining ring on the second waveguide. A sealing ring is placed against an external sealing surface at a reduced external diameter end formed on one waveguide to sealingly engage a corresponding sealing surface on the other waveguide as the waveguides are urged toward each other.

Simplified flangeless unisex waveguide coupler assembly

DOEpatents

Michelangelo, D.; Moeller, C.P.

1993-05-04

A unisex coupler assembly is disclosed capable of providing a leak tight coupling for waveguides with axial alignment of the waveguides and rotational capability. The sealing means of the coupler assembly are not exposed to RF energy, and the coupler assembly does not require the provision of external flanges on the waveguides. In a preferred embodiment, O ring seals are not used and the coupler assembly is, therefore, bakeable at a temperature up to about 150 C. The coupler assembly comprises a split collar which clamps around the waveguides and a second collar which fastens to the split collar. The split collar contains an inner annular groove. Each of the waveguides is provided with an external annular groove which receives a retaining ring. The split collar is clamped around one of the waveguides with the inner annular groove of the split collar engaging the retaining ring carried in the external annular groove in the waveguide. The second collar is then slipped over the second waveguide behind the annular groove and retaining ring therein and the second collar is coaxially secured by fastening means to the split collar to draw the respective waveguides together by coaxial force exerted by the second collar against the retaining ring on the second waveguide. A sealing ring is placed against an external sealing surface at a reduced external diameter end formed on one waveguide to sealingly engage a corresponding sealing surface on the other waveguide as the waveguides are urged toward each other.

Simplified flangeless unisex waveguide coupler assembly

DOE Office of Scientific and Technical Information (OSTI.GOV)

Michelangelo, D.; Moeller, C.P.

1993-05-04

A unisex coupler assembly is disclosed capable of providing a leak tight coupling for waveguides with axial alignment of the waveguides and rotational capability. The sealing means of the coupler assembly are not exposed to RF energy, and the coupler assembly does not require the provision of external flanges on the waveguides. In a preferred embodiment, O ring seals are not used and the coupler assembly is, therefore, bakeable at a temperature up to about 150 C. The coupler assembly comprises a split collar which clamps around the waveguides and a second collar which fastens to the split collar. Themore » split collar contains an inner annular groove. Each of the waveguides is provided with an external annular groove which receives a retaining ring. The split collar is clamped around one of the waveguides with the inner annular groove of the split collar engaging the retaining ring carried in the external annular groove in the waveguide. The second collar is then slipped over the second waveguide behind the annular groove and retaining ring therein and the second collar is coaxially secured by fastening means to the split collar to draw the respective waveguides together by coaxial force exerted by the second collar against the retaining ring on the second waveguide. A sealing ring is placed against an external sealing surface at a reduced external diameter end formed on one waveguide to sealingly engage a corresponding sealing surface on the other waveguide as the waveguides are urged toward each other.« less

Compensated electron and hole pockets in an underdoped high- Tc superconductor

NASA Astrophysics Data System (ADS)

Sebastian, Suchitra E.; Harrison, N.; Goddard, P. A.; Altarawneh, M. M.; Mielke, C. H.; Liang, Ruixing; Bonn, D. A.; Hardy, W. N.; Andersen, O. K.; Lonzarich, G. G.

2010-06-01

We report quantum oscillations in the underdoped high-temperature superconductor YBa2Cu3O6+x over a wide range in magnetic field 28≤μ0H≤85T corresponding to ≈12 oscillations, enabling the Fermi surface topology to be mapped to high resolution. As earlier reported by Sebastian [Nature (London) 454, 200 (2008)10.1038/nature07095], we find a Fermi surface comprising multiple pockets, as revealed by the additional distinct quantum oscillation frequencies and harmonics reported in this work. We find the originally reported broad low-frequency Fourier peak at ≈535T to be clearly resolved into three separate peaks at ≈460 , ≈532 , and ≈602T , in reasonable agreement with the reported frequencies of Audouard [Phys. Rev. Lett. 103, 157003 (2009)10.1103/PhysRevLett.103.157003]. However, our increased resolution and angle-resolved measurements identify these frequencies to originate from two similarly sized pockets with greatly contrasting degrees of interlayer corrugation. The spectrally dominant frequency originates from a pocket (denoted α ) that is almost ideally two-dimensional in form (exhibiting negligible interlayer corrugation). In contrast, the newly resolved weaker adjacent spectral features originate from a deeply corrugated pocket (denoted γ ). On comparison with band structure, the d -wave symmetry of the interlayer dispersion locates the minimally corrugated α pocket at the “nodal” point knodal=(π/2,π/2) , and the significantly corrugated γ pocket at the “antinodal” point kantinodal=(π,0) within the Brillouin zone. The differently corrugated pockets at different locations indicate creation by translational symmetry breaking—a spin-density wave has been suggested from the suppression of Zeeman splitting for the spectrally dominant pocket. In a broken-translational symmetry scenario, symmetry points to the nodal (α) pocket corresponding to holes, with the weaker antinodal (γ) pocket corresponding to electrons—likely responsible for the negative Hall coefficient reported by LeBoeuf [Nature (London) 450, 533 (2007)10.1038/nature06332]. Given the similarity in α and γ pocket volumes, their opposite carrier type and the previous report of a diverging effective mass in Sebastian [Proc. Nat. Am. Soc. 107, 6175 (2010)10.1073/pnas.0913711107], we discuss the possibility of a secondary Fermi surface instability at low dopings of the excitonic insulator type, associated with the metal-insulator quantum critical point. Its potential involvement in the enhancement of superconducting transition temperatures is also discussed.

Evanescent fields of laser written waveguides

NASA Astrophysics Data System (ADS)

Jukić, Dario; Pohl, Thomas; Götte, Jörg B.

2015-03-01

We investigate the evanescent field at the surface of laser written waveguides. The waveguides are written by a direct femtosecond laser writing process into fused silica, which is then sanded down to expose the guiding layer. These waveguides support eigenmodes which have an evanescent field reaching into the vacuum above the waveguide. We study the governing wave equations and present solution for the fundamental eigenmodes of the modified waveguides.

Vertical waveguides integrated with silicon photodetectors: Towards high efficiency and low cross-talk image sensors

NASA Astrophysics Data System (ADS)

Tut, Turgut; Dan, Yaping; Duane, Peter; Yu, Young; Wober, Munib; Crozier, Kenneth B.

2012-01-01

We describe the experimental realization of vertical silicon nitride waveguides integrated with silicon photodetectors. The waveguides are embedded in a silicon dioxide layer. Scanning photocurrent microscopy is performed on a device containing a waveguide, and on a device containing the silicon dioxide layer, but without the waveguide. The results confirm the waveguide's ability to guide light onto the photodetector with high efficiency. We anticipate that the use of these structures in image sensors, with one waveguide per pixel, would greatly improve efficiency and significantly reduce inter-pixel crosstalk.

Microoptoelectromechanical system (MOEMS) based laser

DOEpatents

Hutchinson, Donald P.

2003-11-04

A method for forming a folded laser and associated laser device includes providing a waveguide substrate, micromachining the waveguide substrate to form a folded waveguide structure including a plurality of intersecting folded waveguide paths, forming a single fold mirror having a plurality of facets which bound all ends of said waveguide paths except those reserved for resonator mirrors, and disposing a pair of resonator mirrors on opposite sides of the waveguide to form a lasing cavity. A lasing material is provided in the lasing cavity. The laser can be sealed by disposing a top on the waveguide substrate. The laser can include a re-entrant cavity, where the waveguide substrate is disposed therein, the re-entrant cavity including the single fold mirror.

Electrically Tunable Nd:YAG waveguide laser based on Graphene

PubMed Central

Ma, Linan; Tan, Yang; Akhmadaliev, Shavkat; Zhou, Shengqiang; Chen, Feng

2016-01-01

We demonstrate a tunable hybrid Graphene-Nd:YAG cladding waveguide laser exploiting the electro-optic and the Joule heating effects of Graphene. A cladding Nd:YAG waveguide was fabricated by the ion irradiation. The multi-layer graphene were transferred onto the waveguide surface as the saturable absorber to get the Q-switched pulsed laser oscillation in the waveguide. Composing with appropriate electrodes, graphene based capacitance and heater were formed on the surface of the Nd:YAG waveguide. Through electrical control of graphene, the state of the hybrid waveguide laser was turned on or off. And the laser operation of the hybrid waveguide was electrically tuned between the continuous wave laser and the nanosecond pulsed laser. PMID:27833114

Low-loss curved subwavelength grating waveguide based on index engineering

NASA Astrophysics Data System (ADS)

Wang, Zheng; Xu, Xiaochuan; Fan, D. L.; Wang, Yaoguo; Chen, Ray T.

2016-03-01

Subwavelength grating (SWG) waveguide is an intriguing alternative to conventional optical waveguides due to its freedom to tune a few important waveguide properties such as dispersion and refractive index. Devices based on SWG waveguide have demonstrated impressive performances compared to those of conventional waveguides. However, the large loss of SWG waveguide bends jeopardizes their applications in integrated photonics circuits. In this work, we propose that a predistorted refractive index distribution in SWG waveguide bends can effectively decrease the mode mismatch noise and radiation loss simultaneously, and thus significantly reduce the bend loss. Here, we achieved the pre-distortion refractive index distribution by using trapezoidal silicon pillars. This geometry tuning approach is numerically optimized and experimentally demonstrated. The average insertion loss of a 5 μm SWG waveguide bend can be reduced drastically from 5.58 dB to 1.37 dB per 90° bend for quasi-TE polarization. In the future, the proposed approach can be readily adopted to enhance performance of an array of SWG waveguide-based photonics devices.