Terahertz Imaging Using Nanorectifier-Based Detectors and Broadband Thermal Sources

Several terahertz imaging experiments have been conducted at room temperature using a self-switching diode (SSD) rectenna as a detector, and a broadband thermal source (at 610 °C) as a continuous-wave terahertz generator. Since the terahertz emission produced by the source is non-coherent with random polarizations and has a wide-ranging spectrum, the SSD-based rectenna employed in this work utilizes a planar spiral micro-antenna which has a circular polarization that able to effectively capture all incident radiation regardless of the angles. The antenna has been designed for a broadband frequency response in the range of 0.1-10 THz. This is to ensure the terahertz images produced are ascribed to the terahertz radiation collected by the antenna, but without eliminating the possibility of thermal effects at frequencies higher than the terahertz region. In order to further validate the results obtained, an Airy pattern experiment has been conducted. Based on this experiment, the effective frequency response of the SSD rectenna is estimated at 2.29 THz. The utilization of thermal source and micro-size rectenna in this work may pave the way to explore many opportunities in developing flexible, compact, and low-cost terahertz imaging systems without the use of expensive components (e.g., typically lasers are used as terahertz sources).