A terahertz quadband metasurface absorber with enhanced sensitivity for biosensing applications

Abstract

In this paper, a compact quadband terahertz (THz) metasurface biosensor resonating at four distinct frequencies 1.08, 2.07, 3.01, and 4.09 THz is proposed. The designed unit cell ensures strong field confinement by the utilization of four resonant structures, namely a square ring, a modified square ring, a circular ring and a cross connected quad split ring, hence achieving very high sensing performance for various biological samples. Sensitivities as high as 0.759, 1.338, 1.989, and 2.35 THz RIU⁻¹ along with corresponding figure of merit values of 28.111, 49.556, 66.3, and 39.831 RIU⁻¹ for different resonant modes highlight the device capability. Additionally, absorption is very high, up to 99.79%, and the structure exhibits stable behavior for incident angles of up to 70°. The biosensor also offers distinct responses for healthy, malignant, and infected samples, proving its suitability for multi-disease sensing. Due to the multi-resonant behavior, high absorption, and excellent sensing, the proposed metasurface biosensor is suitable for THz biomedical sensing applications.