We present the initial results of entraining colloidal quantum dots emitting at wavelengths from 0.5um through 1.2um, in various micro-structured optical fibers. Conventional and non-conventional, micro-structured optical fibers fabricated at Virginia Tech’s Fiber & ElectroOptics Research Center (FEORC) have been combined with semiconductor, colloidal quantum dots fabricated by the VT Advanced Biomedical Center (VTabc). The results are presented primarily in the form of visual verification and analysis of entrainment phenomena, for a cross-section of colloidal dot and micro-structured fiber forms. Unique optical, electro-optical and material properties resulting from the combinations are visibly suggested in the results. Core/clad/free space propagation properties and effects of emitted and absorbed light fields are observed to be dependent on the structure, aspect ratio and materials of the fibers as well as the properties of the colloidal quantum dots. Basic spectral data on representative free-space materials will be presented in the current paper. The presentation will explore in passing, the research options available to such quantum dot-fiber combinations, including advanced sensors, sources and filters.
Standard meteorological sensors and sensor suites used for weather and environmental monitoring are currently based primarily on electronic instrumentation that is frequently susceptible to destruction and/or interruption from natural (e.g. lightning) and man-made sources of Electromagnetic Interference (EMI). The cost of replacement or shielding of these systems is high in terms of frequency of replacement and the incipient capital cost. Sensors based on optical fibers have been developed in sufficient variety as to allow the development of full meteorological instrumentation suitess based on individual or multiplexed optical fiber sensors. Examples of sensing functions which can be implemented using optical fibers include: wine speed (cup anemometers & Doppler lidars), wind direction (vanes & lidars), temperature, humidity, barometric pressure, accumulated precipitation and precipitation rate (fiber lidar). Suites of such sensors are capable of using little or no electronics in the environmentally exposed regions, substantially reducing system EMI susceptibility and adding functional capability. The current presentation seeks to explore options available in such meteorological suites and examine the issues in their design and deployment. Performance data on several newer fiber sensors suitable to meteorological use will be presented and discussed.
A miniaturized optical fiber magnetometer has been designed, assembled and evaluated for the detection and classification of vehicles. The sensor element consists of a Fabry-Perot cavity formed between the parallel ends of a high quantity cylindrical metallic glass ribbon and a single mode optical fiber, both held int a hollow tube with an inner diameter several microns larger than the ribbon and the fiber. This sensor head is then potted in a small-diameter, rugged, nonmagnetic housing to allow handling and installation into a protected section of parking lot or other environment to enable vehicle signature detection and analysis. The minimum detectable magnetic field is on the order of 100 nT at dc. The sensor has been used to evaluate the potential detection and analysis of vehicle signatures. When material in a vehicle passes nearby the sensor element, it perturbs the magnetic field and produces a complex output signal dependent upon the shape of the ferrous material in the vehicle, its distance and orientation with respect to the sensor element, and the sped of the vehicle. We have also considered the use of wavelet methods to allow the processing of such data, because it allows variations in differential phasing corresponding to varying vehicles speeds.
The objective of this paper is to describe the performance of optical fiber sensors that have been embedded within polymer matrix composites (PMCs) for more than 15 years. This paper was included in a session concerning the history of sensors for smart materials and structures, and was intended as an overview of early work in this area. Our group at Virginia Tech has been involved in the use of embedded fiber sensors since 1978 when R. Claus, then at the NASA Langley Research Center, helped embed sensors in PMCs to monitor cure and post-cure strain and temperature. Our oldest surviving cross-ply laminate composite specimen with embedded fiber sensors dates from 1982, and was fabricated on campus using a hot platen press. We have recently physically examined this specimen to study possible degradation of the material in the vicinity of the embedded fiber elements, and interrogated the embedded sensors using intensity, modal, interferometric and time-of-flight measurement systems. The basic conclusions of this work thus far are 1) the sensor fibers are still functional, 2) the sensor leads have not been sheared off the specimen after 15 years of use, 3) the composite specimen has not delaminated or otherwise showed signs of degradation, and 4) problems concerning the motion of sensor elements within curing systems, the interconnect problem, and cross-sensitivities that were difficulties in the early 1980s remain key issues today.
Recent advances in diffractive liquid crystal (LC) modulation structures for projection display service have generated diffractive spatial light modulator (SLM) devices capable of high performance in transmission and/or reflection. Patterning of the LC domain alignments has resulted in the generation of near perfect phase diffraction grating structures in the lC material, which can be controlled by a single electrode or by an array of segmented electrodes, such as an array of pixels. Consequently, diffractive artifacts from inter-electrode gaps can be eliminated and/or suppressed in a wider spectrum of applications with enhanced performance relative to previous structures. Transmissive diffractive LC modulators suitable for display or switch applications with modulation efficiencies in excess of 90 percent and contrast ratios of greater than 1500:1 in un-polarized light have been demonstrated. Operation of this type of modulator in reflection has also been verified and demonstrated. Comparison of patterned alignment, LC device performance with MEMS and other diffractive structures will be given. Extensions of these techniques to devices which include beam scanners and controllable diffractive optics will be proposed.
The rapid development of solid-state lasers in al three primary colors has opened up the possibility of new electronic displays. Many of the limitations of light-valve displays are eliminated if laser-light sources are used. Other light-valve options can only be realized using laser sources. This paper will describe some of the more advanced options for the laser and show how these can be used to obtain high-performance electronic displays.
The optical efficiency of a liquid-crystal light-valve projector is determined by the optical design, the method of modulation and the efficiency of the light source. A projector has been built with efficient optics. This projector has been tested with polarized and unpolarized light using rotation of polarization as a modulation technique and also with unpolarized light by using a diffraction grating formed in the liquid crystal. The diffraction technique uses a Schlieren optical system. The light sources tested have been xenon arcs, metal halide arcs and efficient solid-state lasers. The optical system reduces laser speckle significantly when laser sources are used. All combinations exceeded 3 lumens per watt when compared on a white light basis. Experimental results of the combinations will be given. Heating of the panel by absorption of visible light limits the minimum panel size that can be used for a given light output. Typical values will be presented for the choice of panel size for a given light output.