Gaoyan Duan

Spectral Splitting Based on Electromagnetically Induced Transparency in Plasmonic Waveguide Resonator System

Spectral splitting is numerically investigated based on the electromagnetically induced transparency (EIT) in a nanoscale plasmonic waveguide resonator system, which consists of a square ring resonator coupled with a stub-shaped metal-insulator-metal (MIM) waveguide. Simulation results show that the transparency window can be easily tuned by changing the geometrical parameters of the structure and the material filled in the resonators. By adding another stub or (and) square ring resonator, multi-EIT-like peaks appear in the broadband transmission spectrum, and the physical mechanism is presented. Our compact plasmonic structure may have potential applications for nanoscale optical switching, nanosensor, nanolaser, and slow-light devices in highly integrated optical circuits.

A Refractive Index Nanosensor Based on Fano Resonance in the Plasmonic Waveguide System

A novel and compact refractive index sensor based on Fano resonance in the plasmonic waveguide system, which comprises with a stub and groove resonator coupled with a metal-insulator-metal waveguide, is proposed and investigated by the finite-element method. Due to the interaction of the narrow discrete resonance and a broad spectrum caused by the stub resonator and the groove, respectively, the transmission spectrum exhibits a sharp asymmetrical profile. Simulation results show that the Fano resonance can be easily tuned by changing the parameters of the structure. These characteristics offer flexibility to design the devices. This nanosensor yields a sensitivity of ~1260 nm/RIU and a figure of merit of ~2.3 × 104. This letter is significant for design and application of the sensitive nanoscale refractive index sensor.

Sharp Asymmetric Line Shapes in a Plasmonic Waveguide System and its Application in Nanosensor

A sharp and asymmetric line shape is numerically predicted in a novel and compact plasmonic waveguide system. This system consists of a groove and a ring resonator coupled with a metal-insulator-metal waveguide. Due to the interaction of the narrow discrete resonance and a broad spectrum caused by the ring resonator and the groove, respectively, the transmission spectrum exhibits a sharp asymmetrical profile. Simulation results show that the spectral line shape can be easily tuned by changing the parameters of the structure. The physical features contribute to a highly efficient plasmonic nanosensor for refractive index sensing with the sensitivity of 1160 nm/RIU and a figure of merit of 3200. This plasmonic structure with such high figure of merits may find important applications in the on-chip nanosensors.

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.

Polarization Splitter with Optical Bistability in Metal Gap Waveguide Nanocavities

A polarization splitter is proposed and numerically investigated. It is composed of two same structures with different arrangement, which is a kind of metal-dielectric nanocavity filling a piece of nonlinear optical material into metal gap waveguides for each. This device with optical bistability based on surface plasmon provides a new way to manipulate light by tuning the incident light intensity and will be essential for the coming optical information processes.

Fano resonances based on multimode and degenerate mode interference in plasmonic resonator system

In this paper, three Fano resonances based on three different physical mechanisms are theoretically and numerically investigated in a plasmonic resonator system, comprised of two circular cavities. And the multimode interference coupled mode theory (MICMT) including coupling phases is proposed to explain the Fano resonances in plasmonic resonator system. According to MICMT, one of the Fano resonances originates from the interference between different resonant modes of one resonator, the other is induced by the interference between the resonant modes of different resonators. Mode degeneracy is removed when the symmetry of the system is broken, thereby emerging the third kind of Fano resonance which is called degenerate interference Fano resonance, and the degenerate interference coupled mode theory (DICMT) is proposed to explain this kind of Fano resonance. The sensitivity and FOM* (figure of merit) of these Fano resonances can be as high as 840 nm/RIU and 100, respectively. These are useful for fundamental study and applications in sensors, splitters and slow-light devices.

A band-pass plasmonic filter with dual-square ring resonator

In this paper, we show the simulation of a plasmonic band-pass filter which consists of two surface plasmon polaritons (SPPs) waveguides and a resonator in metal–insulator–metal (MIM) structure. The resonator is formed by two square rings and a patch between them. The patch is a tiny rectangle cavity in order to transfer the SPPs from one ring to the other. The finite element method (FEM) method is employed in simulation. The results show that the dual-ring resonator performs better than a single ring does. The 3 dB bandwidth near the peak wavelength λ = 1054 nm is merely 31.7 nm. The resonant wavelength can be shifted by changing the side length of the square ring. This narrow band-pass filter is easy to fabricate and has potential applications in future integrated optical circuits.

A Novel Optical Temperature Sensor Based on Surface Plasmon Polariton Resonator

In this letter, we present a novel optical temperature sensor based on a nanoscale surface plasmon polariton (SPP) resonator. A bimetal layer is applied in the structure to detect the changes in temperature. The resonance wavelength of the SPP resonator shifts with the deformation of the bimetal layer. The effect of temperature on the refractive index of the material is also discussed. The finite element method is employed to numerically calculate the reflectance spectra. To the best of our knowledge, it is the first design of an SPP temperature sensor based on thermal deformation, and this structure may be applied in the future integrated optical circuit.

An optical pressure sensor based on π-shaped surface plasmon polariton resonator

We propose a metal–insulator–metal (MIM) structure which consists of a π-shaped resonator and a surface plasmon polariton (SPP) waveguide. The finite element method (FEM) is employed in the simulation. The results show that this structure forms an optical pressure sensor. The transmission spectra have a redshift with increasing pressure, and the relation between the wavelength shift and the pressure is linear. The nanoscale pressure sensor shows a high sensitivity and may have potential applications in biological and biomedical engineering.