A plasmonic waveguide coupled system that is composed of a square ring cavity and a metal-insulator-metal （MIM） waveguide with two silver baffles is proposed. The transmission and reflection properties of the proposed plasmonic system are investigated numerically using the finite element method. The normalized Hz field distributions are calculated to analyze the transmission mode in the plasmonic system. The extreme destructive interference between light mode and dark mode causes plasmonically induced reflection （PIR） window in the transmission spectrum. The PIR window is fitted using the coupled mode theory. The analytical result agrees with the simulation result approximately. In addition, the PIR window can be controlled by adjusting structural parameters and filling different dielectric into the MIM waveguide and the square ring cavity. The results provide a new approach to designing plasmonic devices.
The coupled resonator-induced transparency （CRIT） phenomenon, which is analogous to electromagnetically induced transparency in atomic systems, can occur in an original integrated optical resonator system due to the coherent interference of the coupled optical resonators. The system was composed of three ring resonators on silicon, each with the same cavity size, and the optical coupling to the input and output ports was achieved using grating with a power coupling efficiency of 36%. A CRIT resonance whose spectrum shows a narrow transparency peak with a low group velocity was demonstrated. The quality factor of the ring resonator can attain a value up to 6x 104, and the harmonic wavelength can be controlled by adjusting the temperature. The through and drop transmission spectra of the resonator are reconciled well with each other and also consistent well with the theoretical analysis.
Preparation and characterization of a liquid level sensor based on macro-bending coupling of fibers are demonstrated in this Letter. The sensitive component can be obtained through a twisting and twining structure of transparent cladding plastic fibers. The difference in light power originating from the surrounding media in the fibers is tested. The light power loss for different tested media and the fiber bending magnitude are investigated. The sensing measurements show that the coupling light power in the passive fiber decreases in accordance with increasing liquid level, whereas it exhibits a steady tendency in the case of the active fiber.
