(98a) Application of Metamaterials and Rectenna for Capture of Blackbody Radiation

Metamaterials, a new synthetic set of materials with properties that do not exist on their own in nature, typically consist of various composite materials such as metals and dielectrics. Their repeating geometric structure and material set provide the metamaterial with a negative index of refraction. The negative index of refraction induces a primary function of metamaterials: their ability to manipulate electromagnetic waves. In this study, metamaterials are designed and fabricated to manipulate blackbody radiation into a well-organized, functional source of electromagnetic waves that are rectified to a DC voltage.

The metamaterial-rectenna unit is designed to convert heat into electricity using the optical properties of the blackbody radiation emitted from heat source. The blackbody radiation is optically manipulated by the metamaterial. In general, as the temperature of the object increases, the wavelength and intensity of the blackbody radiation increase. The metametarial-rectenna units fabricated in this study are designed to capture electromagnetic radiation with a frequency of 1 THz.

The constructed device uses a rectenna as the rectifying device to convert the alternating current (AC) induced from the electromagnetic waves emitted as blackbody radiation to a direct current (DC). The rectenna, containing a metal insulator metal (MIM) tunneling diode, utilizes the ordered electromagnetic radiation from the metamaterial. The metamaterial consists of copper and a photosensitive polymer in an alternating pattern that focuses the electromagnetic radiation over onto the rectenna. The metal of choice, copper, is selected due to its high thermal and electrical conductivity. SU-8 is selected as the photosensitive polymer due to its well-characterized optical properties as well as use in photolithography. The metamaterial is fabricated using various techniques of photolithography, including wet and dry etching of metals and oxides, thin-layer deposition of metals using evaporation, and electrodeposition.

In order to test the functionality of the metamaterial, a heat source applies heat at a set temperature to the metamaterial. Using test pads that have been built into the structure and connected to the rectenna, the diodes are characterized using four-point probe IV measurements. The thermal measurements utilize two of these probes to detect any voltage that is generated by the rectenna-metamaterial device when exposed to a controlled heat source. In this study, a proof of concept design of the metamaterial-rectenna units is achieved and a plan for future development is suggested.