New nano- or micro-patterned metal nonlinear metasurfaces, robust against temperature and more sustainable than current IR materials, could respond across the LWIR-to-SWIR spectrum (no band gap) for long-distance data/power transfer, thermal management, sensing, navigation, and detection. In this presentation, we discuss our recent discovery of longitudinal and transverse optical rectification (OR) in an asymmetric plasmonic grating that is inherently linear. A periodic Au stripe array breaks inversion symmetry perpendicular to the stripes, so that direct (zero frequency) electronic, rectified current, due to selective excitation of only one SPP mode, flows with incident photons polarized perpendicular to the stripes. We also measured the influence of the photon helicity on the OR current, from coupling of the spin of propagating surface plasmon-polaritons (SPPs) to their linear momentum and to the angular momentum of incident photons. It is interesting that bosonic SPPs generate this electrical current. Simple ‘photon drag’ and other models of electronic current do not completely explain the experiment. We discuss scientific advances to better understand these phenomena.
We report experimental and theoretical/simulation results from 1-D and 2-D photonic crystals of novel biomaterials that are synthesized in-house at DEVCOM SC. Inspired by these biomaterials and related phenomena, we experiment with sensing analyte molecules for chem/bio detection. Because these biomaterials have high indices of refraction, they confine photons tightly. Optical properties are predicted computationally based on experimental measurements of indices of refraction using variable-angle continuous spectra ellipsometers, with both unfocused and focused probing spots. This biomaterial, when combined with polymers that enable smooth films (polyvinyl acetate, ethyl cellulose, etc.), would be a natural, environmentally friendly, non-toxic, and toxicologically safe material appropriate for scaling up for large-area optical sensing of molecules, especially toxic industrial molecules. We carry out initial research on the detection of analyte molecules in solution via optical methods and compare to simulations. We contrast with inorganic materials for remote sensing, reconnaissance, UAVs, etc. and compare challenges in scalable fabrication including synthetic biology.
Nonlinear optical effects like Optical Rectification are needed to achieve signals and provide feedback and active control of photonic platforms. Simpler materials having tunable nonlinear optical effects that respond across much of the spectrum, instead of semiconductors. Building on our earlier results, we report a new experimental observation with theoretical analysis of a transverse, or ‘Hall Effect’ optical rectification current from surface plasmons in a simple 1-D gold metasurface, without photon drag effects. Due to the strong nanoscale resonant enhancement of the electromagnetic field, higher order polarization terms cross-couple the orthogonal planes of incidence and transverse rectified current.
We report results from thin films of novel biomaterials based on natural minerals, never before synthesized in the laboratory using primarily non-toxic and environmentally friendly materials and characterized optically. These biomaterial films have high indices of refraction and would be a natural and toxicologically safe material to use for large-area optical sensing of molecules, including toxic industrial molecules. Adhering modest concentrations of molecules in solution (water/humidity, ethanol, glucose, ammonia, etc.) to the surface of a Fabry-Perot cavity is shown experimentally to sufficiently alter the index of refraction and thickness of the Fabry-Perot films to enable detection of the molecules via optical methods (reflectance, ellipsometry, transmission, etc.). We report laboratory sensing of 3 types of molecules in solution with controlled high-quality Fabry-Perot cavities. We discuss different and better biominerals to use and discern potential applications.
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