Browse Topic: Waveguides
ABSTRACT FBS Inc. is working with the TARDEC Electrified Armor Lab to develop a nondestructive structural health monitoring technology for composite armor panels that utilizes an array of embedded ultrasonic sensors for guided wave tomographic imaging. This technology would allow for periodic or real-time monitoring of armor integrity while being minimally intrusive and adding negligible weight. The technology is currently being developed and tested in pseudo composite armor panels and efforts are focused on reducing sensor array density, improving sensor integration procedures, and maximizing system sensitivity to damage. In addition to experimental testing and development, FBS is developing a highly-automated finite element model generation and analysis program to be used in conjunction with Abaqus/Explicit commercial finite element software. This program is specifically dedicated to modeling guided wave propagation in pseudo composite armor panels between embedded ultrasonic sensors
The paper presents a theoretical framework for the detection and first-level preliminary identification of potential defects on aero-structure components by employing ultrasonic-guided wave-based structural health monitoring strategies, systems and tools. In particular, we focus our study on ground inspection using a laser-Doppler scan of the surface velocity field, which can also be partly reconstructed or monitored using point sensors and actuators structurally integrated. Using direct wavefield data, we first question the detectability of potential defects of unknown location, size, and detailed features. Defects could be manufacturing defects or variations, which may be acceptable from a design and qualification standpoint; however, those may cause significant background signal artefacts in differentiating structure progressive damage or sudden failure like impact-induced damage and fracture. We consider the surface velocity field over continuous time stamps obtained from laser
Photonic crystals are materials for controlling and manipulating the light flow. Nano photonic devices deal with behavior of the light in the nanomaterial and devices. It works on the interaction of nano devices with light. They are periodic structures with different refractive indices. The wave guides can be constructed will have sharp and low-loss bending enabling high integration density of several orders of magnitude. On silicon surfaces, nano- and microstructures are created to lower reflection and increase light absorption. It can be applied to enhance infrared (IR) bolometer applications based on MEMS. In this work Silicon nanowires photonic crystals are grown and the electric characteristics and frequency characteristics are modeled, simulated and studied using finite element method. Waveguide is created by removing a set of wires making a path for signal flow for the frequency within the band gap. It is observed that depending on the displacements of the nanowires, waves of
Dispersive optical elements are important for many applications. In bulk, free-space optics, prisms, and gratings are often used. In optical waveguides, particularly in integrated photonics, arrayed waveguide gratings (AWG) are most commonly used. AWGs split an optical signal into different wavelength channels. Serial Arrayed Waveguide Grating enables higher resolution wavelength separation
RF filters are critical components in aerospace and defense electronic systems. In high-frequency transmissions, they channel desired signals and reject unwanted signals, enabling reliable signal processing across the RF, microwave, and millimeter wave (mmWave) electromagnetic spectrum. In operating environments with many such signals, including from jammers trying to disrupt the operation of some systems, RF filters are employed in progressively higher frequencies. At the same time, systems engineers are requesting smaller filters that fit within drop-in surface mount technology (SMT) packages mounted within compact printed circuit board (PCB) assemblies. Selecting a filter for an A&D application requires an understanding of available RF filter responses, physical formats, and technologies, with a good idea of necessary functional goals, such as separating channels or rejecting interference. The optimum filter for an aerospace and defense (A&D) system need not take up much space but
A new composition of germanosili-cate glass created by adding zinc oxide has properties good for lens applications. The new family of zinc germanosilicate glass has a high refractive index comparable to that of pure germania glass. Samples showed high transparency, good ultraviolet-shielding properties, and good glass forming ability, making them suitable for lens applications. Germanosilicate glass is essential in the manufacture of optical amplifiers, waveguides, and solid-state lasers
Micro-optics and nanostructures are key technologies for the latest optoelectronic components in smartphones, smart glasses and vehicles. Some examples used in consumer electronics include microlenses in time-of-flight or ambient light sensors, diffractive optical elements (DOE) for structured light generation, as well as surface relief gratings with nanometer precision in diffractive waveguides that enable new applications like 3D sensing and augmented reality glasses
Engineers have suggested a colorful solution to next-generation energy collection: Luminescent solar concentrators (LSCs) in windows. The team designed and built foot-square “windows” that sandwich a conjugated polymer between two clear acrylic panels. The thin middle layer is designed to absorb light in a specific wavelength and guide it to panel edges lined with solar cells. Conjugated polymers are chemical compounds that can be tuned with specific chemical or physical properties for a variety of applications such as conductive films or sensors for biomedical devices
Most technologies today rely on devices that transport energy in the form of light, radio, or mechanical waves; however, these waveguiding channels are susceptible to disorder and damage, either in manufacturing or after they are deployed in harsh environments
The field of photonic integration — the area of photonics in which waveguides and devices are fabricated as an integrated system onto a flat wafer — is relatively young compared to electronics. Photonic integration has focused on communications applications traditionally fabricated on silicon chips, because these are less expensive and more easily manufactured
Despite enormous advances in integrated photonics over the last decade, an efficient integrated phase delay remains to be demonstrated. This problem is fundamental – most monolithic thin film deposition relies on centro symmetric materials (such as silicon, silicon dioxide, silicon nitride), which by definition do not have an electro-optic effect. Such materials have been shown to be excellent transparent materials, however they are either optically passive, or rely on very small plasma dispersion effect or power-hungry thermo-optic effect for tunability. These phase change materials have losses associated due to heating or carrier injection in the waveguides. This research shows that graphene can be used to provide electro-optic properties to traditionally passive optical materials
Conductive oxides-based modulator devices could provide promising candidates for ultra-compact and ultra-fast optical interconnects in future integrated photonic circuits. Army Research Office, Research Triangle Park, North Carolina The major goals of this research project included two parts. First, an ultracompact plasmonic electrooptical (EO) modulator was to be developed and investigated for efficient intensity modulation. Second, an ultracompact and high-speed EO modulator based on a dielectric platform was to be developed for straightforward integration with existing CMOS technology. Both modulators were targeted to facilitate next-generation interconnects for integrated photonic circuits. This work performed on this project explored novel conductive oxide-based slot waveguides based on the unique properties of indium-tin-oxide (ITO). This research was one of the first experimental attempts to demonstrate optical modulators at nanoscale, and one of the first systematic
Photonic choke-joint (PCJ) structures for dual-polarization waveguides have been investigated at NASA's Goddard Space Flight Center for use in device and component packaging. This interface enables the realization of a high-performance, non-contacting waveguide joint without degrading the in-band signal propagation properties. The choke properties of two tiling approaches — symmetric square Cartesian and octagonal quasi-crystal lattices of metallic posts — are explored and optimal PCJ design parameters are presented. For each of these schemes, the experimental results for structures with finite tilings demonstrate near ideal transmission and reflection performance over a full waveguide band
NASA’s Jet Propulsion Laboratory has developed a low-loss dielectric waveguide that provides a simple, versatile, and flexible transmission medium. Dielectric waveguides — long, solid pieces of dielectric that confine electromagnetic waves — offer high bandwidth and low transmission loss compared to conventional metallic waveguides. Despite these advantages, practical use of these waveguides has been limited because a large fraction of signal power is lost at the state-of-the-art interconnects joining conventional metallic waveguides and dielectric waveguides. JPL’s interconnect solution uses lens coupling to reduce these losses by a factor of 10 or more, yielding a reliable, cost-effective alternative to conventional waveguides
Aging infrastructure has a major impact on safety, increasing the need to assess damage severity. Machinery, systems, and components such as airplanes, cars, pumps, and pipes in the oil and chemical industry are subject to varying cyclic service loading and environmental influences. Sometimes multilayered coatings are used, requiring a high-resolution inspection to confirm the presence of a defect such as a delamination, and accurately locate and quantify its size. Highly attenuating materials may significantly increase the inspection time while limiting defect observability. Guided waves have been recognized as having excellent potential for nondestructive inspection. However, the presence of viscoelastic coatings used for corrosion protection is one of the major obstacles for guided wave inspection
It is desirable to measure the electromagnetic properties of devices and materials in the millimeter part of the spectrum. For guided wave-based devices and materials (waveguides, coaxial devices), a vector network analyzer (VNA) is an excellent tool for this purpose since it provides full reflection and transmission characterization at high precision
Electro-optic modulators rely on a change in the index of refraction for the optical wave as a function of an applied voltage. The corresponding change in index acts to delay the wavefront in the waveguide. The goal of this work was to develop a high-speed, high-power waveguide-based modulator (phase and amplitude) and investigate its use as a pulse slicer. The key innovation in this effort is the use of potassium titanyl phosphate (KTP) waveguides, making the high-power, polarization- based waveguide amplitude modulator possible. Furthermore, because it is fabricated in KTP, the waveguide component will withstand high optical power and have a significantly higher RF modulation figure of merit (FOM) relative to lithium niobate. KTP waveguides support high-power TE and TM modes — a necessary requirement for polarization-based modulation as with a Pockels cell
Microwave heating is an important process for many commercial, industrial, and household applications. Industrial microwave ovens are widely used for chemical processing, agri-food, medical products, and consumer products applications. Resonant cavities are often used to speed up chemical reactions, and have the advantages of being small and producing efficient distributions of microwave energy. These multimode cavities can be considered as batch ovens where products can be treated; alternatively, microwave tunnels with multiple waveguides can be used to provide continuous production
Aircraft-engine rotating equipment usually operates at high temperature and stress. Non-invasive inspection of microcracks in those components poses a challenge for the non-destructive evaluation community. A low-profile ultrasonic guided wave sensor can detect cracks in situ. The key feature of the sensor is that it should withstand high temperatures and excite strong surface wave energy to inspect surface/subsurface cracks. As far as the innovators know at the time of this reporting, there is no existing sensor that is mounted to the rotor disks for crack inspection; the most often used technology includes fluorescent penetrant inspection or eddy-current probes for disassembled part inspection
Solid-state frequency multipliers are used to produce tunable broadband sources at millimeter and submillimeter wavelengths. The maximum power produced by a single chip is limited by the electrical breakdown of the semiconductor and by the thermal management properties of the chip. The solution is to split the drive power to a frequency tripler using waveguides to divide the power among four chips, then recombine the output power from the four chips back into a single waveguide
Today’s rugged embedded computing industry demands the best of technology and reliability. Driven by requirements for higher performance solutions, platforms continually evolve. Standards organizations, such as the VSO (VMEbus Standards Organization), are diligently working to bring the technology for these solutions to the mainstream. The VSO’s VPX architecture, based on Tyco Electronics’ MULTIGIG RT2 backplane connector as qualified to the VITA 46.0 standard, is the latest technology to be applied to rugged embedded computing. In addition to dealing with escalating processing, power, and cooling requirements of leading edge solutions, the VSO is now addressing the need to realize high bandwidth and high fidelity transmission via alternative media — e.g. fiber optic and coaxial wave guides. This technology is crucial in realizing the full potential of today’s cutting edge C4ISR gear, including RF intensive radar, SIGINT and IED defeat gear, as well as systems benefiting from fiber
A theoretical analysis has revealed that tapered optical waveguides could be useful as white-light whispering-gallerymode (WGM) optical resonators. The compactness and the fixed-narrow-frequency- band nature of the resonances of prior microdisk and microsphere WGM resonators are advantageous in low-power, fixed-narrow-frequency-band applications. However for optical-processing applications in which there are requirements for power levels higher and/or spectral responses broader than those of prior microdisk and microsphere WGM resonators, white-light WGM resonators in the form of optical tapers would be preferable
Monolithic microwave integrated-circuit (MMIC) amplifiers of a type now being developed for operation at frequencies of hundreds of gigahertz contain InP high- electron-mobility transistors (HEMTs) in a differential configuration. The differential configuration makes it possible to obtain gains greater than those of amplifiers having the single-ended configuration. To reduce losses associated with packaging, the MMIC chips are designed integrally with, and embedded in, waveguide packages, with the additional benefit that the packages are compact enough to fit into phased transmitting and/or receiving antenna arrays
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