We will develop novel bowtie nanoantennas and resonant tunneling diodes to convert the mid-IR portion of the solar spectrum to electric power. We will take advantage of the large enhanced electric field by the lightning rod effect and by the gap plasmon resonances to enhance the in-plane electric field in the ?knot? of the bowtie and increase the efficiency of electron tunneling.

What is the intellectual merit of the proposed activity?

Our approach will initially complement solar cells by converting infrared blackbody radiation from the earth, at night, during rainy days or from heat generated by the inefficient solar energy conversion during day time. Then, we will extend this technology to higher frequencies and will challenge current solar cells for solar energy conversion of the visible spectrum. This research will enhance our understanding of efficient coupling to nanoantenna in the mid-IR and the visible spectrum and will help us understand the physics of tunneling at very high frequencies which is not well understood.

What are the broader impacts of the proposed activity?

Our new devices will impact the field of solar energy collection and will allow collection of energy from spectral regions that were previously ignored. We anticipate that our novel technology will eliminate the need for large volumes of relatively expensive semiconductors and will allow for much more extensive harvesting of energy from ambient radiation. A new experiment on energy scavenging will be introduced in our undergraduate class in optoelectronics and will complement the solar energy laboratory being established in our Department.

Project Report

The main outcome of this project is the demonstration of electromagnetic energy scavenging of infrared radiation around a wavelength of 10 um by using a small 5 micron long optical antenna and a rectifying tunneling diode. Optical rectification of the incident radiation is demonstrated. A small DC voltage is produced when the IR radiation is directed on the antenna. Our technology is scalable to arrays, is compatible with flexible substrates, and does not require cryogenic refrigeration of the antenna element. The DC generated energy can be stored in a battery and can subsequently be used to power any electronic devices. Being able to convert infrared energy into a useful form of energy is transformative. Any human activities typically involve using energy and converting a sizable fraction of this energy to heat. It is usually difficult to transform back heat to a higher form of usable energy. This is what our technology allows us to do. Of course, we are still limited by the second law of thermodynamics and we cannot get aroung increasing the entropy of the universe. But we can create useful energy from a non-thermal equilibrium situation. We are proposing a completely new approach to extracting energy from the environment. In particular, we have demonstrated energy conversion using an asymmetric metal-insulator-metal (MIM) Ni-NiOx-Ni nanoantenna/tunneling diode. We use a geometrically asymmetric field enhancing technique in a planar device to decouple the RC time constant and simultaneously minimize the capacitance and the resistance. In this way, we have been able to get a response at frequencies as high as 30 THz, the operation frequency of a CO2 laser. A study of the antenna response was also conducted at frequencies slighthtly below 1 THz.

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University of Maryland College Park
College Park
United States
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