Ultra narrowband perfect absorber for refractive index sensing applications in mid-infrared region.

In this study, a novel narrowband perfect absorber (NPA) with dual band resonance frequencies is presented. The proposed NPA absorbs over 99% of the incident laser beam in both resonance modes and it indicates high quality factor (Q = 135.2) resonance which is the highest for a perfect absorber performing in the mid-infrared region. In this work, the charge and current distributions for the corresponding resonance modes are investigated. The absorbance spectrum of the electric and magnetic field distributions is also obtained for the corresponding resonance modes. Furthermore, the detecting performance of the NPA is analyzed by covering the proposed device with a cladding layer. The figure of merit (FOM) and refractive index sensitivity (RIS) of the structure are calculated. Due to its high quality factor, enhanced electric and magnetic field responses, near unity absorbance for both resonance modes and tunable detecting characteristics the proposed NPA can be used in spectroscopy applications. [ABSTRACT FROM AUTHOR]