Rectennas at optical frequencies: How to analyze the response

Optical rectennas, antenna-coupled diode rectifiers that receive optical-frequency electromagnetic radiation and convert it to DC output, have been proposed for use in harvesting electromagnetic radiation from a blackbody source. The operation of these devices is qualitatively different from that of lower-frequency rectennas, and their design requires a new approach. To that end, we present a method to determine the rectenna response to high frequency illumination. It combines classical circuit analysis with classical and quantum-based photon-assisted tunneling response of a high-speed diode. We demonstrate the method by calculating the rectenna response for low and high frequency monochromatic illumination, and for radiation from a blackbody source. Such a blackbody source can be a hot body generating waste heat, or radiation from the sun

Extraction of Zero-Point Energy from the Vacuum: Assessment of Stochastic Electrodynamics-Based Approach as Compared to Other Methods

In research articles and patents several methods have been proposed for the extraction of zero-point energy from the vacuum. None of the proposals have been reliably demonstrated, yet they remain largely unchallenged. In this paper the underlying thermodynamics principles of equilibrium, detailed balance, and conservation laws are presented for zero-point energy extraction. The proposed methods are separated into three classes: nonlinear processing of the zero-point field, mechanical extraction using Casimir cavities, and the pumping of atoms through Casimir cavities. The first two approaches are shown to violate thermodynamics principles, and therefore appear not to be feasible, no matter how innovative their execution. The third approach, based upon stochastic electrodynamics, does not appear to violate these principles, but may face other obstacles. Initial experimental results are tantalizing but, given the lower than expected power output, inconclusive.</p

OPTICAL RECTENNA SOLAR CELLS USING GRAPHENE GEOMETRIC DIODES

ABSTRACT A solar cell using micro-antennas to convert radiation to alternating current and ultrahigh-speed diodes to rectify the AC can in principle provide extremely high conversion efficiencies. Currently investigated rectennas using metal/insulator/metal (MIM) diodes are limited in their RC response time and have poor impedance matching to the antenna. We have investigated a new rectifier, referred to as a geometric diode, which can overcome these limitations. The geometric diode consists of a conducting thin-film, such as graphene, patterned in a geometry that leads to diode behavior. We have experimentally demonstrated geometric diodes made from graphene and simulated their characteristics using the Drude model for charge transport. Here we compare the characteristics of rectennas using MIM diodes with those based on geometric diodes and show the improved performance of the latter

Demonstration of Thermoradiative Power Generation Using Compensated Infrared Rectennas

Thermoradiative devices convert low-temperature waste heat to electricity. These devices harvest heat and generate energy using deep space as a heat sink by radiating through the 8 to 13 μm atmospheric window. Infrared rectennas, which consist of ultrahigh speed diodes coupled to micrometer-scale antennas, can be tuned to these frequencies and are a good candidate for thermoradiative power generation at room temperature, if certain challenges can be circumvented. Practical optical rectennas require a high diode conversion efficiency, a high coupling efficiency between the diode and antenna, and a large array of devices sufficient to produce significant power. The novelty of our approach lies in designing and building a diode compensation structure at terahertz and arraying 250000 diodes, two approaches that have never been reported before. We demonstrate that a Ni/NiO/Al2O3/Cr/Au metal-double insulator–metal (MI2M) diode-based infrared rectenna with a 2.5 μm transmission line compensation structure in a staggered array can produce power from a temperature difference, and with development, it has the potential to produce competitive power outputs