for underwater communications. The objective for underwater communications includes low-power consumption (<1 watt), compactness (<100 cubic inches), high data transfer rates (>10mbs), and long ranges (>1km, depending on turbidity) in both littoral and deep ocean environments.

Unique interactions between photons having OAM and SAM at the atomic level opens potentially new optical component options, where periodic excitation of materials (including plasmons) result in localized maxima or minima affecting its phase response. As a result, new sensing, propagation and increased conversion efficiencies can result. In the field of nonlinear optical dynamics, spiral or chiral wave phenomena in excitable media, such as those seen in low- to high-power, solid-state lasers, have long been of interest. While polarization is limited to two spin states, photons with OAM can have multiple eigenstates and "unique" interactions with materials based on those eigenvalues. For example, spiral waves with particular eigenvalues emanating from solid state lasers have to be coupled with the states of phase oscillators. When correctly modeled and then constructed, they can produce effects yielding higher performance. Three-dimensional, metamaterial optical components offer the opportunity to move well beyond current state-of-the-art optical components by exploiting OAM and SAM characteristics, while still utilizing little more than either modified or standard COTS solid state laser sources and COTS optical receivers. The nature of these unique wavefront structures causes photons to interact (or rather avoid interaction) with matter in ways that can be exploited within properly constructed metamaterials. This topic seeks to identify, design, and construct three dimensional photonic OAM and SAM metamaterial structures suitable for use as optical elements within photonic systems such as those for LADAR/LIDAR, optical communications and imagers. The interaction of the photon with Mie or Rayleigh resonances that produce electromagnetic field localizations and enhancements, and those with OAM or SAM which change both the magnitude of the interaction and the directionality, are of interest. Of particular interest is the potential for reducing turbulence induced refractions, where the atmospheric characteristics of a propagation path (e.g., estimated by Fried's coherence length (r0), Greenwood Frequency (fG), Isoplanatic Angle, Rytov Number) indicate beam bifurcation or break-up. This topic seeks to develop potential solutions for and to better understand the underlying physics and potential for photonic OAM and SAM interactions. This topic encompasses individual beam combining (coherent and incoherent methods) and unique interactions with optical sensors under conditions where turbulent flows occur. With higher photon densities, the resulting interaction and resonances with matter may induce plasmon creation well below expected bulk thresholds, providing several relevant and practical electronic device applications to commercially available sensors. Further, the investigation of photons with OAM and SAM and �metamaterials� could result in reconfigurable responsivity where the bulk EM activity, determined by the OAM scattering properties of the structures, results in novel properties. Such properties include a tunable positive to negative refractive index. This is much like a two-dimensional polarized surface material or �metasurface� that can be structured to exhibit extremely high transmissivity (or high impedance) to incident EM waves. However, an OAM �metasurface� can be structured to respond to OAM phase or �spin� in even more unique ways.

PHASE I: Perform both initial modelling and reduction of optical turbidity attenuation as measured in laboratory experiments utilizing COTS laser sources and optical sensors, which are expected to confirm initial proposed technical approaches. Conduct initial modelling utilizing existing commercially available optical simulation software, or modified versions that enable specific OAM/SAM interaction models. Carry out laboratory experimentation using synthetic sea water and normal tap water to confirm proposed capability improvement trends or objectives. For Phase I, experimental setup for attenuation measurement would be simplified and comprised of at least three in-line components: a water cell, a laser of known power, and a receiver/power meter. A calibrated laser would be made to pass through water filled cell, and on the other end of the cell, power is collected and made to fall on power meter. Introduction of various turbidity, turbulence, and plasmonic metasurfaces would then be introduced to establish known systems parameters and to provide comparative results. Dimensions, configuration and construction of the test cell would be proposed, utilizing as much available COTS hardware as possible. Alternatives to laboratory scale testing are possible, however, results mustto provide evidence of performance beyond any reasonable doubt. For example, two or more independent modeling approaches that provide performance predictions and have a correlation higher than 75% would be considered a compelling result. By the end of Phase I, the proposed capability improvement trends or objectives and goals would be refined with specific implementations identified, suitable for potential transition. Develop a Phase II plan.

PHASE II: In the first year, based upon the results of Phase I analysis, experimentation and the development plan, either fabricate new components or modify existing COTS products and subject them initially to low power