Plasmonic Beamsteering

ABSTRACT: The objective of this proposal is to develop a plasmonic beam steering device based on annular metallic array including electro-optically active materials. The proposed device will be designed to work either in the visible or near infrared (NIR) regimes, depending on the geometrical dimension of the metal structure. We will exploit field localization and surface plasmon generation/propagation that occur in such devices to access the regime of extraordinary optical transmission: under these circumstances both linear and nonlinear optical properties of the system as a whole are enhanced and we will have a full control on the field localization in every part of the structure. The geometrical sizes and the spacing, as well as metal thickness and form factor will be properly dimensioned to work efficiently in the enhanced transmission regime. Our preliminary simulations reveal that this approach will result in an integrated device exhibiting an extremely high sensitivity to the refractive index of the electro-optic material filling the structure. In fact the change in the optical response and the consequent field deflection is produced by the local variation of the refractive index inside sub-wavelength regions where the field is strongly localized. BENEFIT: An optical beam scanner is an indispensable device for the missile LADAR seeker. Optical scanners are used to control the position of a light beam in one or more orthogonal spatial dimensions. There is a strong need to develop a seeker with increased ability to track and engage multiple fleeting targets at increased range. Existing opto-mechanical scanners and liquid crystals (LC) based scanners can effectively scan laser beams but have limited scanning speeds. LC scanners have further limitations that include high drive voltages and non-programmable birefringent plate designs. In principle, electro-optic effect based scanners can operate at higher speeds (in the nanosecond range), but require a high driving voltage (e.g., 1000 V), which makes it very difficult to achieve ns range high-speed operation. To achieve fast automatic target tracking and recognition, a fast scanning, low-voltage, optical beam scanner is needed for future tactical missile seekers. Certain applications require the ability to quickly reconfigure the scan directions to correct for errors in the overall scanning system. Such example applications are free-space optical wireless, inter-satellites links, optical microscopy, mobile military platforms, and 3-D displays. For example, inter-satellite links require fine angular scanning tunability of the order of 1rad at high speeds to keep track of the fast moving destination satellite. Yet another case of mobile military platforms needs a scan dynamic range of 45o. Hence, demand exists for a no moving parts, scanner that can provide scanning over a large angular scan dynamic range with high resolution beam control.