We present a design and detailed fabrication of periodic and quasi-periodic plasmonic arrays including infrared scattering, patterning stripe, particle, and hole arrays with large periodicities for longwave IR scattering, and experimental reflectivity and backwards scattering from these metamaterials. We experimentally verify LWIR and other infrared diffraction from sparser arrays and arrays of holes in plasmonic metals. We simulate, using critical coupling analytical models and numerical algorithms, the reflectivity, scattering, etc. of these metamaterial arrays, and compare to the laser-based measurements. We also investigate a hole array in a plasmonic material (Ag).We find plasmonic resonances at both the air-Ag and Ag-substrate interfaces to be present, increasing transmission via the Extraordinary Optical Transmission effect, which may be tuned by an electromagnetic field to shift the resonance position, and in the future may enable novel tunable rectification.
We report chemical warfare agent (CWA and) Toxic Industrial Compound (TIC) detection with colorimetric dyes, dispersed in porous polymer coatings on long (>1 m) fibers, for lightweight remote fiber-based sensing exploiting optical fibers’ quality, length, and low weight/power requirements. Illuminating LED light travels longitudinally within the polymer fiber core and evanescently interacts with the colorimetric dyes, dispersed in a porous polymer cladding. Reflectivity and absorption, measured by a precise COTS sensor, change with small amounts of TICs or CWAs. The cladding regenerates its signal after ~15 minutes. Minimum Detectable Concentration is below 1 ppm for ammonia. We report chemical testing at 2 different facilities against 3 CWAs, 2 agent-relevant TICs, and ammonia as a control, and field trials. We plan applications in remote sensing, reconnaissance, perimeter and airborne sensing, detecting other toxic materials, and manufacturing. We acknowledge funding from DTRA.
Combinatorial colorimetry has detected chemical compounds and uniquely identifies toxic industrial compounds at the ppmv level. We investigate colorimetric dyes, coated with polymers, on long fibers for lightweight remote/standoff fiber-based sensing (unmanned monitoring points, UAVs) exploiting optical fibers’ quality, length, low weight; retaining performance and low power needs. We model/ investigate an advanced longitudinal lightweight polymer fiber colorimetric sensing platform, sensitivity to fiber length, light propagation, and loss of light and sensitivity due to losses in the cladding, the spatial transient’s effect, and predict long lightweight fiber sensor sensitivity/selectivity. Visible light from illuminating LEDs travels along the polymer or silica fiber core and evanescently interacts with colorimetric dyes. Dyes are in porous, mechanically strong polymers with optimized thickness in order to enable analytes to reach the cladding/core interface yet mechanically strong.
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