Xiaokang Song

Multiple Fano Resonances Control in MIM Side-Coupled Cavities Systems

We theoretically demonstrate a plasmonic waveguide that allows easy control of the fano profile. The proposed structure is analyzed by the coupled-mode theory and demonstrated by the finite-element method. Due to the interaction of the local discrete state and the continuous spectrum caused by the side-coupled cavity and the baffle, respectively, the transmission spectrum exhibits a sharp and asymmetric profile. The profile can be easily tuned by changing the parameters of the structure. Moreover, the compact structure can easily be extended to several complex structures to achieve multiple fano resonances. These characteristics offer flexibility in the design of the device. This nanosensor yields a sensitivity of 1280 nm/RIU and switches with an on/off contrast ratio of about 30 dB. Our structures may have potential applications for nanoscale optical switching, nanosensors, and slow-light devices in highly integrated circuits.

Tunable Electromagnetically Induced Transparency in Plasmonic System and Its Application in Nanosensor and Spectral Splitting

A compact structure is proposed to achieve electromagnetically induced transparency (EIT) response, which consists of a side-coupled cavity and a ring resonator. Novel structures and the transmission characteristics are studied in several different situations. The plasmonic device can be used as a high-sensitivity refractive sensor with a sensitivity of 1200 nm/RIU. In addition, multi-EIT-like peaks appear in the original broadband spectrum by adding another side-coupled cavity or ring resonator, and the physical mechanism is presented. The system paves a new way toward highly integrated optical circuits and networks, particularly for nanosensor, spectral splitter, and nonlinear devices.

Active Control of Slow Light in a Gain-Assisted Plasmon-Induced Transparency Structure

Plasmon-induced transparency (PIT) in a compact plasmonic resonator structure, which consists of a metal– dielectric–metal waveguide with an aperture-coupled square cavity and a slot resonator, is investigated theoretically and numerically. We find the transparency window and the delay of slow light in this structure can be controlled at a fixed wavelength by carefully adjusting the geometrical parameters of the aperture-coupled square cavity. By introducing gain medium into the slot resonator, the transmittance and the group index in transparency window both are dramatically enhanced with optically pumping the medium, and the group delay time can reach to 0.93 ps. In addition, triple PIT effects are also achieved by adding another aperture-coupled cavity and slot cavity, and corresponding slow light also can be dynamically tuned. This study paves a new route toward the realization of highly integrated all-optical circuits and networks, especially for ultrafast switches, optical buffers, lasers, and nanosensors.