Unidirectional Coupler Optimization Of Surface Plasmon Polaritons Based On Genetic Algorithm Method

Surface plasmon polaritons(SPPs)are electromagnetic waves in infrared or visible light,propagating along the metal-dielectric or metal-air interface,and excited by the external electromagnetic fields.SPPs have a wide range of applications in subwavelength optics such as biochemical sensing and photonic integrated circuits,because of its ability to control and constrain light at subwavelength scales.SPPs unidirectional couplers are basic elements in optical systems and will be widely used in integrated photonic circuits in the future.Therefore,SPPs unidirectional couplers have been an important research aspect in surface plasmon.Many researchers have proposed several designs of SPPs unidirectional couplers,such as groove-type and slit-type.However,the performance of these designed SPPs unidirectional couplers still has great potential to improve.Therefore,optimization algorithms are required to optimize the structural parameters of SPPs unidirectional couplers and improve its performance.This study presents the use of co-simulation method of genetic algorithm and COMSOL in MATLAB environment to optimize optimize the geometric parameters of quasi-periodic and aperiodic surface plasmon polaritons slit unidirectional coupler.The extinction ratio of all the surface plasmon polaritons slit unidirectional couplers is greater than 60 dB under arbitrary initial structure parameters with genetic algorithm options of generations of 40.Therefore,the co-simulation method of genetic algorithm with COMSOL not only greatly speeds up the process to find the optimal parameters,but also does not depend on the initial structure parameters.Moreover,this method can also be applied to optimization of other photonic devices,such as the perfect mirror,the anti-reflective film of photovoltaic cell surface.Even with little knowledge of optimization,photonic devices with good performance can be obtained with this method.