Major growth in the image sensor market is largely as a result of the expansion of digital imaging into cameras, whether stand-alone or integrated within smart cellular phones or automotive vehicles. Applications in biomedicine, education, environmental monitoring, optical communications, pharmaceutics and machine vision are also driving the development of imaging technologies. Organic photodiodes (OPDs) are now being investigated for existing imaging technologies, as their properties make them interesting candidates for these applications. OPDs offer cheaper processing methods, devices that are light, flexible and compatible with large (or small) areas, and the ability to tune the photophysical and optoelectronic properties − both at a material and device level. Although the concept of OPDs has been around for some time, it is only relatively recently that significant progress has been made, with their performance now reaching the point that they are beginning to rival their inorganic counterparts in a number of performance criteria including the linear dynamic range, detectivity, and color selectivity. This review covers the progress made in the OPD field, describing their development as well as the challenges and opportunities.

Organic Photodiodes: The Future of Full Color Detection and Image Sensing

Virtually all electronic and optoelectronic devices necessitate a challenging assembly of conducting, semiconducting and insulating materials into specific geometries with low-scattering interfaces and microscopic feature dimensions. A variety of wafer-based processing approaches have been developed to address these requirements, which although successful are at the same time inherently restricted by the wafer size, its planar geometry and the complexity associated with sequential high-precision processing steps. In contrast, optical-fibre drawing from a macroscopic preformed rod is simpler and yields extended lengths of uniform fibres. Recently, a new family of fibres composed of conductors, semiconductors and insulators has emerged. These fibres share the basic device attributes of their traditional electronic and optoelectronic counterparts, yet are fabricated using conventional preform-based fibre-processing methods, yielding kilometres of functional fibre devices. Two complementary approaches towards realizing sophisticated functions are explored: on the single-fibre level, the integration of a multiplicity of functional components into one fibre, and on the multiple-fibre level, the assembly of large-scale two- and three-dimensional geometric constructs made of many fibres. When applied together these two approaches pave the way to multifunctional fabric systems.

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Towards multimaterial multifunctional fibres that see, hear, sense and communicate

Aspects of the subject disclosure may include, for example, receiving, by a feed point of a dielectric antenna, electromagnetic waves from a dielectric core coupled to the feed point without an electrical return path, where at least a portion of the dielectric antenna comprises a conductive surface, directing, by the feed point, the electromagnetic waves to a proximal portion of the dielectric antenna, and radiating, via an aperture of the dielectric antenna, a wireless signal responsive to the electromagnetic waves being received at the aperture. Other embodiments are disclosed.

Method and apparatus for coupling an antenna to a device

A distributed antenna and backhaul system provide network connectivity for a small cell deployment. Rather than building new structures, and installing additional fiber and cable, embodiments described herein disclose using high-bandwidth, millimeter-wave communications and existing power line infrastructure. Above ground backhaul connections via power lines and line-of-sight millimeter-wave band signals as well as underground backhaul connections via buried electrical conduits can provide connectivity to the distributed base stations. An overhead millimeter-wave system can also be used to provide backhaul connectivity. Modules can be placed onto existing infrastructure, such as streetlights and utility poles, and the modules can contain base stations and antennas to transmit the millimeter-waves to and from other modules.

Backhaul link for distributed antenna system

A distributed antenna system is provided that frequency shifts the output of one or more microcells to a 60 GHz or higher frequency range for transmission to a set of distributed antennas. The cellular band outputs of these microcell base station devices are used to modulate a 60 GHz (or higher) carrier wave, yielding a group of subcarriers on the 60 GHz carrier wave. This group will then be transmitted in the air via analog microwave RF unit, after which it can be repeated or radiated to the surrounding area. The repeaters amplify the signal and resend it on the air again toward the next repeater. In places where a microcell is required, the 60 GHz signal is shifted in frequency back to its original frequency (e.g., the 1.9 GHz cellular band) and radiated locally to nearby mobile devices.

Remote distributed antenna system

There is provided a feedback-controlled self-heat-monitoring fiber, including an insulator having a fiber length with at least one metal-semiconductor-metal thermal sensing element along the fiber length and disposed at a position in a cross section of the fiber for sensing changes in fiber temperature. An electronic circuit is connected to the thermal sensing element for indicating changes in fiber temperature. A controller is connected for controlling optical transmission through an optical transmission element, that is disposed along the fiber length, in response to indications of changes in fiber temperature.

Thermal sensing fiber devices

Optical fields are measured using sequential arrangements of optical components such as lenses, filters, and beam splitters in conjunction with planar arrays of point detectors placed on a common axis1. All such systems are constrained in terms of size, weight, durability and field of view. Here a new, geometric approach to optical-field measurements is presented that lifts some of the aforementioned limitations and, moreover, enables access to optical information on unprecedented length and volume scales. Tough polymeric photodetecting fibres drawn from a preform2 are woven into light-weight, low-optical-density, two- and three-dimensional constructs that measure the amplitude and phase of an electromagnetic field on very large areas. First, a three-dimensional spherical construct is used to measure the direction of illumination over 4π steradians. Second, an intensity distribution is measured by a planar array using a tomographic algorithm. Finally, both the amplitude and phase of an optical wave front are acquired with a dual-plane construct. Hence, the problem of optical-field measurement is transformed from one involving the choice and placement of lenses and detector arrays to that of designing geometrical constructions of polymeric, light-sensitive fibres.

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Large-scale optical-field measurements with geometric fibre constructs.

Thermal sensing and thermography yield important information about the dynamics of many physical, chemical, and biological phenomena. Spatially resolved thermal sensing enables failure detection in technological systems when the failure mechanism is correlated with localized changes in temperature. Indeed, IR-imaging systems have become ubiquitous for applications where line-of-sight contact can be made between the measured object and the camera lens. Nevertheless, many critical applications do not lend themselves to radiative IR imaging because of the subterraneous nature of the monitored surface, spatial constraints, or cost considerations. The recent challenge of monitoring the skin temperature beneath the thermal tiles on the space shuttle represents a good example in which high-spatial-resolution information is required on very large surface areas but which cannot be obtained using traditional thermal-imaging systems. Thus, the problem of continuously monitoring and detecting a thermal excitation on very large areas (100 m) with high resolution (1 cm) is one that has remained largely unsolved. We present a new methodology for measuring spatially resolved temperature information on large areas with high spatial resolution and low cost. Underlying our approach is a new fiber material that senses heat along its entire length and generates an electrical signal. This is in contrast to all previous work on thermal sensing using fibers, which require the use of optical probing signals. Although the fibers are produced by thermal drawing, they contain a set of materials that have not been traditionally associated with this process. The use of thermal drawing guarantees the production of extremely long fibers, while the innovation in preparation of the preform and choice of materials allows the incorporation of novel functionalities. Specifically, both thermal and electrical functionalities are obtained in the fibers studied in this communication, while optical and optoelectronic functionalities in alternative designs have been obtained previously and are reported elsewhere. The fibers are produced by a novel fabrication technique that enables the incorporation of materials with widely disparate electrical and thermal properties in a single, macroscopic, cylindrical preform rod, which subsequently undergoes thermal drawing to give solid-state microstructured fibers with high uniformity. The main requirements in the materials used in this preform-to-fiber approach are as follows: 1) the component which supports the draw stress should be glassy, so as to be drawn at reasonable speeds in a furnace, with self-maintaining structural regularity; 2) the materials must be above their respective softening or melting points at the draw temerature to enable fiber codrawing; and 3) the materials should exhibit good adhesion/wetting in the viscous and solid states without delamination, even when subjected to thermal quenching. According to these requirements, we identified suitable semiconducting, insulating, and metallic materials. The insulating material is a 75 lm thick polymer film: polysulfone (Ajedium, USA), having a glass-transition temperature, Tg = 190 °C. The chosen semiconducting glass, Ge17As23Se14Te46 (GAST), was arrived at by optimizing the composition formula GexAs40–xSeyTe60–y (10 < x < 20 and 10 < y < 15) under constraints of compatibility of Tg and viscosity with the codrawn polymer. Metallic electrodes are made of the alloy 96 %Sn–4 %Ag, which has a low meltingtemperature range (TM = 221–229 °C) below the fiber-drawing temperature of 270 °C. The chemical composition of the glass is chosen such that the electronic mobility gap of the amorphous semiconductor is small, yielding high electrical responsivity to small changes in temperature. The fabrication process (see Fig. 1A) begins with preparing cylindrical rods of the glass (see “Amorphous Semiconductor Synthesis” in the Experimental section). A cylindrical shell of polymer having an inner diameter equal to that of the glass rod is prepared with four slits removed from the walls. Four thin rods of the metal alloy are then placed in these slits. The glass rod is inserted into the polymer shell (Fig. 1A(a)), and a polymer sheet is then rolled around the resulting cylinder to provide a protective cladding (Fig. 1A(b)). Finally, the cylinder is thermally consolidated (Fig. 1A(c)) and subsequently is drawn in a fiber-draw tower producing hundreds of meters of C O M M U N IC A IO N S

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Thermal‐Sensing Fiber Devices by Multimaterial Codrawing

A preform-to-fiber approach to the fabrication of functional fiber-based devices by thermal drawing in the viscous state is presented. A macroscopic preform rod containing metallic, semiconducting, and insulating constituents in a variety of geometries and close contact produces kilometer-long novel nanostructured fibers and fiber devices. We first review the material selection criteria and then describe metal-semiconductor-metal photosensitive and thermally sensitive fibers. These flexible, lightweight, and low-cost functional fibers may pave the way for new types of fiber sensors, such as thermal sensing fabrics, artificial skin, and large-area optoelectronic screens. Next, the preform-to-fiber approach is used to fabricate spectrally tunable photodetectors that integrate a photosensitive core and a nanostructured photonic crystal structure containing a resonant cavity. An integrated, self-monitoring optical-transmission waveguide is then described that incorporates optical transport and thermal monitoring. This fiber allows one to predict power-transmission failure, which is of paramount importance if high-power optical transmission lines are to be operated safely and reliably in medical, industrial and defense applications. A hybrid electron-photon fiber consisting of a hollow core (for optical transport by means of a photonic bandgap) and metallic wires (for electron transport) is described that may be used for transporting atoms and molecules by radiation pressure. Finally, a solid microstructured fiber fabricated with a highly nonlinear chalcogenide glass enables the generation of supercontinuum light at near-infrared wavelengths

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Kilometer-Long Ordered Nanophotonic Devices by Preform-to-Fiber Fabrication

The invention provides an optical fiber photodetector including a photoconductive element, such as a semiconducting element, having a fiber length. The semiconducting element is characterized as a non-composite material in at least one fiber direction. At least one pair of conducting electrodes is in contact with the semiconducting element along the fiber length, and an insulator is provided along the fiber length. An optical resonator can be disposed along the fiber length and along a path of illumination to the semiconducting element. The resonator is dimensioned to substantially reflect all illumination wavelengths except for a prescribed range of wavelengths transmitted to the semiconducting element. The fiber photodetector can be arranged in a photodetecting fiber grid, photodetecting fiber fabric, or other configuration for detecting incident illumination.

Jerimy Arnold

Papers

Thermal sensing fiber devices

Large-scale optical-field measurements with geometric fibre constructs.

Thermal‐Sensing Fiber Devices by Multimaterial Codrawing

Kilometer-Long Ordered Nanophotonic Devices by Preform-to-Fiber Fabrication

Optoelectronic fiber photodetector