Optical rectification through an Al₂O₃ based MIM passive rectenna at 28.3 THz

Harevesting energy from waste heat which fluctuates between, approximately, 250 K and 1500 K, i.e., peaking at 2–11 μm, could be a game changer in terms of tapping on to renewable energy sources. However, research in this area has remained elusive due to numerous challenges. We consider waste heat to be an electromagnetic (EM) wave in the mid infrared (IR) frequency range, which can be captured through a resonant antenna and rectified into useful DC through a diode, an arrangement typically known as a rectenna. A bowtie antenna has been optimized for IR field capture and enhancement through EM simulations. At the overlap of the bowtie arms, a metal-insulator-metal (MIM) diode has been realized that can operate at such a high frequency (28.3 THz or 10.6 μm). The choice of a low permittivity insulator (Al₂O₃) helps metigate the RC time constant and the diode's cutoff frequency, whereas the two different work function metals, Au and Ti, facilitate diode operation through tunneling at no applied bias. A custom optical characterization setup employing a 10.6 μm CO₂ laser has been used to assess the IR capture and rectification ability of the rectenna device. A polarization dependent voltage output which is well above the noise level and well matched with our calculations, confirms the successful rectenna operation. According to authors' best knowledge, this is the first demonstration of rectification at 28.3 THz through a MIM diode based rectenna at zero applied bias.