OBJECTIVE: Develop novel solutions for plasmonic field enhancement of receiver circuits for energy harvesting applications. DESCRIPTION: Plasmonic field enhancement is now a viable technological tool. It is used extensively in enhancing the sensitivity of a number of spectroscopic techniques. Surface enhanced Raman spectroscopy and spectroscopy depending on Stark effect are key examples. It appears to be possible to achieve improvement for electromagnetic energy detection (and possibly, enable harvesting of energy from the thermal ambient) using plasmonic field enhancement. The establishment of a plasmon wave has been shown to enhance the electric field in nanoantennae. While plasmonic enhancement of the electric field in optical nanoantennae has been demonstrated, the tunneling diode resistance capacitance (RC) time-constant of a diode monolithically integrated with a nanoantenna was found too large for assuring electric field rectification and to lead to meaningful detection. This solicitation seeks solutions to the limited bandwidth of"rectennae"by reducing the forward diode resistance and capacitance, leading to an overall increase of the coupling efficiency of radiation to the"rectenna"and to an overall increase in conversion efficiency. It will also be expected to improve understanding of the way plasmon generation affects the way light can couple to antenna structures"Rectennas"are integrated structures (antenna, tunnel-diode hybrids) in which the detection element (diode demodulator) is directly embedded at the feed-point of the antenna. They have been shown to function in the terahertz frequency range. As such, they can act to"detect"ambient IR radiation, scavenging it from the environment. The"rectified, optical energy can be used to charge batteries or capacitors. These structures are small (less than 10 microns in their largest dimension) to enable the demodulation of light in the near-infrared (IR) frequency range. The end-line goal of this project is the development of large area, inexpensive sheets that can transform incident infrared radiation into electricity with efficiency suitable for energy harvesting applications. The work also has possible application in the area of IR commuinication. The rectenna structures could be detector circuits for any near-IR communication scheme. Proposed rectenna array solutions should be low cost and be able to transduce beamed infrared power to electric energy and to store the energy in a capacitor or in a battery. Performance metrics include a minimum of 5% conversion efficiency in a 1cm x 1cm array. PHASE I: Investigate and outline a method of integrating antenna and detector structures in such a way as to utilize plasmonic field enhancement to lower the effective diode turn-on voltage. Outline a pathway to lowering the diode time-constants by lowering either (or both) diode forward resistance and capacitance. Demonstrate the viability of the chosen approach. Initial Phase I milestone will be the demonstration of a functioning"rectenna"device capable of detecting infrared radiation in the millimeter wave range of frequencies. Provide a benchmark measurement of conversion efficiency (the ratio of incident infrared power to electric power dissipated in a load). Propose a plan for specific set of interim demonstrations for Phase II of conversion efficiency for their rectenna design as well as conversion efficiency in an area array (e.g. 1mm by 1mm) of rectennas leading to the end goal. PHASE II: Demonstrate infrared detection using the Phase I proposed"rectenna"structure. The goal is to demonstrate a minimum of 5% conversion efficiency in a 1cm x 1cm array with an agreed to set of interim demonstrations for quantifying progress during Phase II. Quantify the ambient heat (10 micron wavelength) to electric energy conversion efficiency of the developed rectenna arrays. Investigate a low cost manufacturing process for rectenna arrays. PHASE III: Transition the developed technology to appropriate DoD platforms. PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The private sector potential includes: Enhanced-detection efficiency in microwave communication systems and the possibility of infrared energy scavenging from the environment. The resulting system can be used to distance power unmanned autonomous vehicles (UAVs) as well as to perform energy scavenging for power management. REFERENCES: 1. Bean, J.A., Tiwari, B., Bernstein, G.H., Fay, P., & Porod, W. (2009). Thermal infrared detection using dipole antenna-coupled metal-oxide-metal diodes."Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures,"27(1), 1114. 2. Faris, S., Gustafson, T. K., & Wiesner, J. (1973). Detection of optical and infrared radiation with DC-biased electron-tunneling metal-barrier-metal diodes."IEEE Journal of Quantum Electronics,"9(7), 737745. 3. Heiblum, M., Shihyuan, W., Whinnery, J., & Gustafson, T.K. (1978). Characteristics of integrated MOM junctions at dc and at optical frequencies."IEEE Journal of Quantum Electronics,"14(3), 159169. 4. Hobbs, P.C.D., Laibowitz, R.B., Libsch, F.R., LaBianca, N.C., & Chiniwalla, P.P. (2007). Efficient waveguide-integrated tunnel junction detectors at 1.6 m."Optics Express,"15(25), 1637616389.