High Q-factor multifunctional plasmonic metasurfaces in the mid-infrared

As application scenarios grow in complexity, multifunctional integrated metasurfaces have been proposed as a potential development direction. We propose a multifunctional high Q-factor metasurface-based platform composed by size-scaled metasurface polarization selective absorbers (MPSAs) capable of polarization selective absorption, refractive index sensing and chiral response. By designing a gold step-shaped unit structure that can break the in-plane and out-of-plane symmetry, bound states in the continuums (BICs) with chiral response and a surface lattice resonance (SLR) are realized. The overall absorption amplitude of the quasi-BIC can reach a maximum value of 0.87 and a Q-factor of 153 while the SLR possesses a high Q-factor exceeding 1274 and a maximum absorption amplitude of 0.93. High extinction ratio up to 13 dB between the transverse magnetic and transverse electric polarization can be achieved. For refractive index (RI) sensing, the bulk RI sensitivities of the proposed MPSA for quasi-BIC and SLR are SBIC = 4000 nm/RIU and SSLR = 3740 nm/RIU, which leads to a high figure of merit (FOM) of FOMBIC = 161 /RIU and FOMSLR = 1247 /RIU, respectively. For chiral response, the maximum circular dichroism (CD) for the proposed MPSA is 0.88 by oblique incidence still maintaining a Qfactor exceeding 120, which indicates that it has potential application for chiral sensing. The proposed multifunctional metasurfaces-based platform possesses the potential to promising future applications for polarization manipulation, chiral biosensing, chiral drug analysis and quantum optics.