Quasi-3D Perfect Absorber Based on the Self-Similar Parasitic Elements as an Optical Sensor with Tunable Attributes for Near-Infrared Application

Abstract

We have designed a novel self-similar plasmonic perfect absorber with a quasi-three-dimensional (3D) shape based on parasitic elements, which is useful as a refractive index sensor for near-infrared applications. In order to achieve tunable attributes, we have applied the liquid crystal medium to provide a tunable structure which can be considered to control the absorption parameter and resonances. In fact, we have proposed a self-similar structure to obtain a multi-band structure in the range of 800–1600 nm with an absorption value up to 99.8%. The basic model is a single cross element, while each quarter is filled up by L-shaped elements by forming a tapered shape like a pyramidal in which the elements are arranged from large to small with various heights and lengths which creates a ziggurat form. So this structure can provide a quad-band absorber which we have implemented as a refractive index sensor with a much higher figure of merit (FOM) in comparison to the flat formations. For the final structure, the maximum values of the FOM and sensitivity (S) are 24,560 RIU−1 and 660 nm RIU−1, respectively.