To overcome the effect of analyte thickness and limitation of single wavelength sensing, we propose an ultra-sensitive stereo metamaterial biosensor with double resonance frequencies based on coupling electric resonance and magnetic resonance. The electromagnetic analysis demonstrates that the double resonance coupling, induced by the structural the stereo double-layer design, can significantly improve sensitive biosensing at the terahertz frequency. The results show that by changing the size of the structure, each resonance frequency can be independently tuned in the range of 0.5-1.8 THz and the maximum refractive index sensitivity is 930.4 GHz/RIU. These results have significant effects on the detection of samples with different frequency points. Our ultra-sensitive stereo metamaterial structure has unparalleled potential and application in biomolecule detection and differentiation.

A novel tunable plasmonic demultiplexer is proposed and numerically investigated by finite element method (FEM). It consists of two half-nanodisk cavities and two sets of E7 liquid crystal arrays which are side-coupled to three metal-dielectric-metal (MDM) waveguides. The demultiplexer can split the input lights into two parts corresponding to port1 (1310 nm) and port2 (1550 nm). The Q-factors of port1 and port2 are 54.6 and 36, and the crosstalk values are −20.7 dB and −29.9 dB, respectively. Obviously, both channels have high Q-factors and low crosstalk value. Moreover, the E7 liquid crystal arrays play a key role in the whole structure, which makes the output power adjustable proportionally by adjusting the applied voltage. This novel feature greatly enriches the function of our demultiplexer. Using the electronical tunable birefringence characteristic of liquid crystal and its arrays structure paves a new way to realize practical on-chip plasmonic system, which can be widely used not only in demultiplexers but also in nanosensors, optical splitters, filters, optical switches, nonlinear photonic and slow-light devices.