Abstract
Enhanced transmissions through a gold film with arrays of subwavelength holes are theoretically studied, employing the rigid full vectorial three dimensional finite difference time domain method. Influence of air-holes shape to the transmission is firstly studied, which confirms two different resonances attributing to the enhanced transmission: the localized waveguide resonance and periodic surface plasmon resonances. For the film coated with dielectric layers, calculated results show that in the wavelength region of interest the localized waveguide resonant mode attributes to sensing rather than the periodic gold-glass surface plasmon mode. Although the detected peak is fairly broad and the shift is not too pronounced, we emphasize the contribution for sensing from the localized waveguide resonant mode, which may opens up new ways to design surface plasmon based sensors.
Highlights
In the recent years, the demonstration of a strong and unexpected enhancement of light transmission through arrays of subwavelength holes has generated numerous experimental and theoretical work [1]-[9]
It has been pointed out [8, 9] that there are two different resonances attributing to the enhanced transmission: (i) localized waveguide resonances where each air hole can be considered as a low-quality-factor resonator, and (ii) well-recognized surface plasmon resonances due to the periodicity
When we further increase the height of the layer, the peak related to the periodic surface plasmon wave hardly shifts while the peak for the localized waveguide mode is strongly sensitive to the refractive index of the layer
Summary
The demonstration of a strong and unexpected enhancement of light transmission through arrays of subwavelength holes has generated numerous experimental and theoretical work [1]-[9]. There has been a growing interest in surface plasmon resonance (SPR) sensing of biochemicals using nanohole arrays [11]-[13]. These SP sensors are based on the enhanced transmission through arrays of nanoholes. It is a general consensus that these sensors are based on SPRs, while the particular nature of the SPR and the mechanism behind the sensing is still a questing open for discussion. We will theoretically study the transmission through arrays of nanoholes and point out the contribution for sensing from the localized waveguide resonant mode utilizing the rigid full-vectorial three-dimensional (3D) finite-difference time-domain (FDTD) method
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