Speaker: Jose Isaac Santos Batista, Dr. Magda El-Shenawee, Department of Electrical Engineering
Date: Wednesday, April 28, 2021, 4:00 PM – 5:00 PM
Title: Three-Dimensional Modeling of Terahertz Photoconductive Antennas Using COMSOL Multiphysics Package
Abstract: The purpose of this work is to understand the physics and engineering design aspects of terahertz signal generation of photoconductive antennas (PCA) on semiconductor substrates. The COMSOL Multiphysics package based on the finite element method is used to model the PCA emitter using four modules: the frequency domain RF module to model the laser excitation, the semiconductor module to calculate the photocurrent, the heat transfer in solids module to study the temperature variation on the device, and the transient RF module to calculate the THz radiated electric field pulse. Solving this 3D model is computationally intensive due to the multi-scale difference between the nanometer thicknesses of some of the materials compared to the micrometer size of the antenna electrodes. The symmetry of the configuration was exploited by applying the perfect electric and magnetic boundary conditions to reduce the computational domain to only one quarter of the device in the RF module. The largest case required solving more than 0.313 billion unknowns at the cost of ~ 3.3 TB RAM and ~ 25 hours CPU time, which was solved at the XSEDE supercomputer. In the temperature calculations, a larger computational domain was required to avoid false rise in temperature even though simulating only the active area of the antenna provided accurate results for the optical and electrical responses. The simulations performed at the high memory nodes at AHPCC helped to identify the required memory and solution time and with the extra-large memory nodes at XSEDE, the calculation of the largest case was achieved.
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