The objective of this research is to develop a new class of room temperature metal-insulator-insulator-metal tunnel diode detectors and monolithically integrate them within novel miniature antenna focal plane array configurations for high resolution and high responsivity THz/infrared imaging as well as energy harvesting. The approach is to enhance nonlinearity of the diodes up to 30THz by using dual tunnel junctions and employ a system level design by addressing issues of antenna-diode impedance mismatches, compact antenna size, inter-element electromagnetic couplings, and bandwidth.
Intellectual Merits: The program is focused on challenges associated with system-level integration of antenna coupled metal-insulator-insulator-metal diodes for high performance THz/infrared imaging. Metal-insulator-insulator-metal diodes offering sensitive detection of radiation up to 30THz will advance the synthesis of ultrathin dielectric materials and nanofabrication. The critical goals of high resolution and high responsivity will be achieved through novel approaches in antenna miniaturization, non-uniform array layouts, and compact impedance matching networks. Ultra-wideband imaging and energy harvesting will be accomplished with novel broadband arrays and computational electromagnetics modeling.
Broader Impacts: The outcomes will impact a broad range of applications including environmental, biomedical, material science, homeland security, and renewable energy. The effort is well aligned with synergistic research in the area of medical THz imaging and infrared renewable energy at both universities. The industry partnership will allow to broadly disseminate research results beyond the academic community. The project will provide a system level design opportunity to graduate students, impact the curriculum at both universities, and leverage ongoing programs to attract underrepresented students to engineering.
One of the key goals is to design and fabricate a femtosecond-fast rectifying tunnel diode coupled to an impedance-matched antenna to form a high-efficiency rectenna. The incidental electromagnetic radiation is captured by the antenna, which is subsequently rectified by the integrated metal-dual insulator-metal (MIIM) diode to generate a DC output. Due to the unique resistive switching behavior and the ultrafast response time of the MIM/MIIM diodes, they are well-suited for detection of ultra-high frequency THz/IR radiations. Particularly, nano-junction MIM/MIIM diodes allow direct detection of electromagnetic radiation up to 30THz, which is above the cutoff frequencies of semiconductor-based counterparts (e.g. Schottky diodes). The proposed extended-hemispherical lens backed slot antenna arrays are attractive for imaging systems at THz frequencies due to the elimination of substrate modes and ease of fabrication. Pixels of a focal plane array (FPA) imaging system are formed by antenna elements integrated with direct detectors such as bolometers or zero-bias diodes. The extended-hemispherical lens operates as a beam-forming tool when pixels are placed at the focal surface of the lens. A miniaturized array design can be developed by incorporating metamaterial inspired antenna loading techniques that enable significant antenna miniaturization at THz and millimeter wave frequencies. Another resolution limitation of the extended-hemispherical lens backed FPAs can be attributed to internal lens reflections due to off-axis, from focal surfaces, pixels. To solve this issue, we have proposed to construct the off-axis pixels from antennas with beam-tilted patterns. A pixel with a beam-tilted pattern can be constructed by utilizing multiple antennas and a compact phase shifting feed network. Therefore, miniaturized antennas are an important design consideration in developing high resolution FPAs.
