Accurate inverse design for high-efficiency and broadband terahertz devices by co-simulation with genetic algorithms

Abstract Terahertz (THz) waves have become a research hotspot in recent years due to their unique advantages, and metasurface-based devices in the terahertz band have outstanding practical applications as the core for the development of terahertz science and technology. However, with the increasing complexity of the metasurface structures, the design methods have become more and more difficult, which hinders the further practical application of terahertz metasurface devices. In this study, we combined MATLAB with the rigorous electromagnetic field simulation software CST (Computer Simulation Technology) to perform a co-simulation method for the design of high-efficiency and broadband THz metasurface devices. In the proposed design method, genetic algorithm (GA) is embedded to realize automatic and inverse design. Aiming to the different requirements of high-efficiency and broadband THz metasurface devices, different objective functions are set to optimize the design of different types of THz metasurface devices. As proofs-of-concept demonstration, three types of high efficiency and broadband THz metasurface devices have been designed by this method, including absorber, polarization convertor and frequency filter. After optimization by GA, we obtained dual metasurface absorber with absorbance of 90% in the range of 0.49 ~ 3.68 THz. The low-pass filter exhibits good filter property, and the polarization converter has a polarization conversion ratio (PCR) greater than 90% in the range of 0.69 ~ 1.52 THz. Based on the rigorous electromagnetic simulation and genetic algorithm, the proposed design method can realize automatic and inverse design with high reliability, compared to the theoretical model based on catenary e-field theory. This study provides an important guiding role and an efficient method for designing and optimizing required metasurface devices with practical applied value.