Numerical analysis of spectrally tunable and polarization independent dual band plasmonic perfect absorber

Purpose: The aim of the study is to design perfect absorber devices with spectrally tunable, near-unity absorption, multi -band, polarization insensitive for mid-infrared spectroscopy.Theory and Methods: Numerical analysis of the structure are carried out with the help of the Lumerical FDTD software. FDTD Solutions has an interface that allows making 3D designs. With this program, reflection and transmission characteristics of the designed the perfect absorber nanoantenna arrays in frequency and time domain are obtained and the absorption characteristic is determined based on these results. Electric and magnetic field distributions at determined resonance frequencies of the created structures can be obtained with field monitors placed in desired areas of the structure.Results: The proposed perfect absorber structure absorbs the incident laser beam over 98% in lower frequency mode and over 99% in higher frequency mode. The structure is also polarization insensitive and spectrally tunable.Conclusion: In this study, a novel plasmonic perfect absorber that can be used in mid-infrared spectroscopy applications is presented. It is observed that the resonance response of perfect absorber is highly dependent on geometric parameters and thus the resonance frequency can be easily tuned by changing the geometry of the structure. Thanks to the tunable spectral response, high electric and magnetic field gains, and the structure being polarization independent, the proposed plasmonic perfect absorber can be used in mid-infrared spectroscopy applications.