摘要： 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 ?lled 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 ?gure of merit (FOM) in comparison to the ?at formations. For the ?nal structure, the maximum values of the FOM and sensitivity (S) are 24,560 RIU?1 and 660 nm RIU?1, respectively.