Chapter 1 A Mid-IR Antenna Integrated with a Geometrically Asymmetrical Metal-Insulator-Metal Rectifying Diode Filiz Yesilkoy, Siddharth Potbhare, Nick Kratzmeier, Akin Akturk, Neil Goldsman, Martin Peckerar and Mario Dagenais 1.1 Introduction Rectennas integrate the demodulating element of an electromagnetic wave trans- ducer directly with an antenna. This leads to highly compact, microminiaturized receivers with physically short paths leading from free space to the preampli- fier/amplifier chain. The approach can provide better control over the geometry of the signal pathway and their impedances. As a result, impedance matching can be realized for more efficient transfer of energy. Moveover, the short signal pathway minimizes noise pick-up and provides a better signal-to-noise (SNR) ratio. The demodulator of choice for the rectenna is the metal-insulator-metal (MIM) tunnel diode. The tunnel-transport process is exceptionally fast, offering high- frequency rectification. In fact, rectennas have been used as detectors in the near infrared (IR), detecting wavelengths as short as 0.633μ m [8]. The fabrication of rectennas is relatively simple, involving either a single or a two-layer metal deposition process. It offers the possibility of cheap manufacture of large-scale, large-area sensor sheets. If this goal is realized, rectennas may also be used as energy harvesters, pulling in electromagnetic energy from the GHz to the THz frequency ranges. Even if the detection efficiency is small ( 1%) the large area and low cost may make this approach an attractive addition to existing solar or RF harvesters. When a thin plastic sheet is used as the substrate to fabricate the rectennas, the resulting technology should contribute to flexible or wearable electronics. Moreover, one can envision coating an airframe with large area infrared detectors acting as a fly’s-eye lens detecting the direction of incoming threats. A large format, lensed system is also possible. Filiz Yesilkoy Department of Electrical and Computer Engineering, University of Maryland, College Park, MD 20742 USA and CoolCAD Electronics LLC, 5000 College Avenue, Suite 2103, College Park, MD 20740, USA e-mail: filizyesilkoy@gmail.com 1