Effects of a bar on optical transmission through Z-shaped metallic slit arrays

We investigate the effects of a bar on optical transmission through Z-shaped metallic slit arrays by using the finite- difference time domain （FDTD） method. A new hybrid Fabry-Perot （FP） surface plasmon polariton （SPP） mode emerges when changing the geometric parameters of the bar, and this mode can be viewed as a coupling between FP mode and SPP mode. In addition, an obvious dip appears in a featured area when the bar deviates from the central line, and a small displacement of the bar leads to tremendous change of the dip. These behaviors can be attributed to the phase resonance. In short, the structure is very sensitive to the metal bar. Furthermore, it combines photonic device miniaturization with sensitivity, which is useful for making optical switches.

Waveguide resonance of subwavelength metallic slits

The transmission characteristics of a metallic film with subwavelength periodic slits are investigated by using the two-dimensional finite-difference time-domain method （2D-FDTD）. Two models are constructed to show the dependance of the transmission spectrum on the slit structure. A sandwiched structure is used to exhibit the contribution of the metallic wall inside slits to the extraordinary high transmission. And a filled slit structure is employed to reflect the relation between the average refractive index inside the slits and the transmission spectrum of the structure. The transmission characteristics of two structures can be explained well with the waveguide resonance theory.

Plasmonic sensor with variable claddings based on metallic slit arrays

We propose a plasmonic sensor with variable refractive index （RI）, which exhibits high sensitivity and extraordinary optical transmission （EOT）. Its variable RI is attributed to its dielectric layers and metallic slit arrays. According to simulation results, the third resonant wavelength has a wavelength sensitivity of 800 nm/RIU and an ultra-high transmittance of 0.8 by adjusting the RIs of the upper and lower dielectrics, incident light angle, and structural geometric parameters. With its unique features, the proposed structure holds considerable potential for extensive application to metal–dielectric grating sensors operating at visible and near-infrared frequencies.

Effects of interplay between metal subwavelength slits on extraordinary optical transmission

In this paper we study the extraordinary optical transmission of one-dimensional multi-slits in an ideal metal film.The transmissivity is calculated as a function of various structural parameters.The transmissivity oscillates,with the period being just the light wavelength,as a function of the spacing between slits.As the number of slits increases,the transmissivity varies in one of three ways.It can increase,attenuate,or remain basically unchanged,depending on the spacing between slits.Each way is in an oscillatory manner.The slit interaction responsible for the oscillating transmission strength that depends on slit spacing is the subject of more detailed investigation.The interaction most intuitively manifests as a current distribution in the metal surface between slits.We find that this current is attenuated in an oscillating fashion from the slit corners to the center of the region between two adjacent slits,and we present a mathematical expression for its waveform.