Design and Optimization of Microbolometer Multilayer Optical Cavity

E.S. Awada, N.F. Al-Khallia, M.R. Abdel-Rahmanb, N.A. Debbara, M.A. Alduraibic,d aElectrical Engineering Department, College of Engineering, King Saud University, Riyadh 11421, KSA bPrince Sultan Advanced Technologies Research Institute (PSATRI), College of Engineering, King Saud University, Riyadh 11421, KSA cPhysics and Astronomy Department, College of Science, King Saud University, Riyadh 11451, KSA dNational Center for Applied Physics, King Abdulaziz City for Science and Technology, KACST, P.O. Box 6086, Riyadh 11442, KSA

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Microbolometers are the most widely used detectors in long-wave infrared uncooled thermal imagers. An optical cavity is required within a microbolometer structure to increase its optical absorption. In this work we present a detailed study on the design and optimization of a microbolometer optical cavity using Essential-Macleod package. In the simulations, the cavity is considered as thin film multi-layers that form: cascaded Fabry-Perot optical cavities. In the design phase, the structures of layers are selected, which includes selection of materials and initial thickness. The absorbing layers are chosen to be made of vanadium-pentoxide (V2O5) and titanium (Ti). In the optimization phase, the designed layer thicknesses are varied to maximize optical absorption within the absorbing layers. The simulations show that Ti layer absorption dominates over the V2O5 layer. Also, the optimization proves that the thickness of cavity's air-gap is not equal simply to quarter-wavelength, because of the presence of a complex cascaded Fabry-Perot structure. The optimized air-gap thickness is found to be ≈ 3.5 μm at wavelength of 10.6 μm.

DOI: 10.12693/APhysPolA.127.1295 PACS numbers: 85.60.Bt, 42.25.Bs