Thermal sensing and thermography yield important information about the dynamics of many physical, chemical, and biological phenomena. [1,2] 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 2 ) with high resolution (1 cm 2 ) is one that has remained largely unsolved. [3,4] 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. [5] 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. [6,7] 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, ins...

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 axis. 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 preform 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 4pi 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.

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 largearea 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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