Detectivity Optimization of Free Standing Micro Machined Membrane Type Superconductor Bolometers

Mehdi Fardmanesh, Superconductor Electronics Research Laboratory, Sharif University of Technology, Tehran, Iran

Abstract: Superconductor bolometers are most sensitive radiation detectors in the micrometer range wavelengths. In the recent years many works have been focused on development of high sensitive bolometers. Detectivity of a bolometer is the most important figure of merit to determine the sensitivity of the device in comparison to other detectors. In this presentation, optimization of detectivity with respect to geometrical parameters for free standing membrane type High Tc superconductor edge transition sensors is theoretically and experimentally investigated and presented. Using a proposed optimization method the optimal analytical detectivity versus device geometry and modulation frequency is calculated. Specificly, the detectivity versus the free standing substrate thickness and modulation frequency is calculated and presented. Based on the theoretical results optimum device geometry for high detectivity is obtained and several bolometers with different geometries are fabricated. The optical responsivity and voltage noise of the bolometers are measured versus modulation frequencies up to 100KHz. Using the measurement results, the corresponding detectivity of the fabricated devices is obtained versus modulation frequency and device geometry. Finally, the results of analytical, experimental and numerical approaches are compared and analyzed. The talk shall be followed by a comprehensive introduction to the SERL and its research activities at Sharif University of Technology.

 

About the speaker: Mehdi Fardmanesh was born in Tehran, in 1961. He received the B.S. degree in electrical engineering from Tehran Polytechnic University in 1987, and the M.S. and Ph.D. degrees in electrical engineering from Drexel University, Philadelphia, Pennsylvania in 1991, and 1993, respectively, and until 1993, he conducted research on development of thin- and thick-film high-temperature superconducting materials, devices, and development of ultralow-noise cryogenic characterization systems at Ben Franklin Superconductivity Research Center, where he also taught in 1994. From 1994 to 1996, he was with the Departments of Electrical Engineering and Physics, Sharif University of Technology in Tehran. In 1996, he joined EEE Dept. at Bilkent University, in Ankara. In 1998 started his collaboration with ISI-Forschungszentrum Jülich, in Germany. In 2000, he established an international collaboration between Bilkent University and Juelich Research Center, and from 2000 to 2004, he was the Director of the joint project for the development of high-resolution high-Tc SQUID-based magnetic imaging system. In 2001, he also reestablished his activities at Sharif University becoming a faculty member of EE Department where he is also currently the vice chair for research affairs. He set up the Superconductor Electronics Research Laboratory (SERL) at Sharif University in 2003. His research interest has mainly focused on the design, fabrication, and modeling of high-temperature superconductor devices and circuits, and he mainly teaches courses in the field of Electronic Devices and Circuits. He has also recently started his research in the field of bioelectronics such as works on “Design of Artificial Retina and DNA conductivity analysis”.