Uncooled Silicon Germanium Oxide Microbolometers with Metasurface for Multispectral Infrared Imaging

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Abstract Title: Uncooled Silicon Germanium Oxide Microbolometers with Metasurface for Multispectral Infrared ImagingAbstract:Many studies have shown that color imagery leads to faster and more accurate scene understanding, reaction time and object identification than intensity-based false color or grayscale imagery. Capturing the spectral distribution (color) in the infrared provides more information, improving contrast and object-identification, which provides better situational awareness than conventional night vision imagery. However, the current cooled multicolor infrared technology requires an expensive cryogenic cooling system for operation, while uncooled multicolor technology is complex and expensive. To address this issue, the research project will integrate metasurfaces onto uncooled infrared (IR) microbolometers in a novel architecture. The metasurface selective absorption will be combined with the Fabry-Pérot resonant cavity in a pixel with multiple stacked microbolometers, to provide high IR absorption in different spectral windows while maintaining a fill factor over 90%. This will allow attributes of incident radiation beyond its intensity, including its spectral distribution, to be resolved. The metasurfaces will allow the electrical and thermal performance of the microbolometer to be partially decoupled from its radiative properties. The resulting technology will lead to low cost, portable uncooled multiband IR detectors with a broad range of applications such as automotive safety, healthcare, surveillance, and landmine detection. The project will provide comprehensive educational training to graduate, undergraduate and high school students, and curriculum development. The outreach effort will be focused on guest lectures at Lincoln University, a regional HBCU, and recruiting students from underrepresented groups in STEM education. In addition, the project will also further scientific education by advancing integrated, multidiplinary, multicampus postgraduate training.The research goal of this project is to establish the design and microfabrication frameworks for uncooled IR microbolometers by integrating a thermally isolated dual-level pixel architecture, a metasurface with engineered radiative properties, and an amorphous Si-Ge-O based sensing layer. This will create an uncooled multiband infrared (IR) microbolometer where the images from different bands are fused into a single multicolor image with high resolution. The multiband operation is accomplished by synthesizing metasurfaces to determine the absorption/transmission/reflection properties of the two microbolometers. The research project focuses on measuring the spectral content in the long wave IR range. The amplitude of the incident radiation is divided into two bands corresponding to the two microbolometers. This will allow the temperature of a radiating surface to be determined without knowing its temperature beforehand. The combination of Fabry-Pérot cavity and surface resonances provides multiple degrees of freedom for designing the spectral response of the pixel so the fill factor does not need to be sacrificed. The use of the metasurfaces as an absorber allows further exploration of the thermal characteristics of microbolometer design for improved performance. Rigorous coupled electromagnetic and thermal models will be built to predict the performance of the devices. These devices will be fabricated and characterized to identify sources of noise and optimize for noise reduction. The research objective is to generate knowledge about the electromagnetic/thermal and noise effects of integrating the metasurface and microboleter, elucidate the interaction between the Fabry-Pérot and metasurface resonance, and establish fabrication principles for the two-band microbolometer. This will provide better detection technology that will enable a future generation of smaller, lighter, low cost multicolor thermal imaging systems that consume less power and operates at ambient temperature.