Abstract
Extraordinary optical transmission spectrum for a two-dimensional metallic hole array (2D-MHA) changes with the hole channel shape. In this paper a new converging-diverging channel (CDC) shape is proposed. A three-dimensional (3D) finite element method is utilized to analyze the transmission characteristics of the 2D-MHA with CDC. The transmission peaks are blue-shifted when the gap at the throat of CDC is reduced. Similar blue-shift in the transmission peaks are observed for a straight channel MHA when the aperture size is reduced. The transmission for the straight channel MHA is not sensitive to the metal film thickness. But, for a CDC MHA the transmission varies with the metal film thickness. Also, the CDC shape gives an extra degree of geometrical variable to 2D-MHA for tuning the transmission peak location with potential applications in nanolithography, imaging and biosensing.
Highlights
The report of extraordinary transmission (EOT) phenomenon through subwavelength metallic hole arrays (MHAs) milled in opaque metal screen [1] generated considerable interest and promoted subwavelength apertures as a core element of new optical devices
It has been shown that the transmission spectrum of metallic hole arrays (MHAs) with converging-diverging channel (CDC) changes with the gap at the throat
It has been shown that the transmittance of MHAs with straight channel does not change much with the thickness of the film
Summary
The report of extraordinary transmission (EOT) phenomenon through subwavelength metallic hole arrays (MHAs) milled in opaque metal screen [1] generated considerable interest and promoted subwavelength apertures as a core element of new optical devices. It was found that when the hole depth is large the SPPs on the two surfaces are uncoupled and the transmission increases exponentially with the decreasing depth [24] It is observed in the THz region that the EOT can be achieved at an array thickness of only one third of the skin depth [25]. In the present study the subwavelength hole having converging diverging channel (CDC) is studied along with the straight channel for transmission properties This proposed CDC shape would still allow similar EOT effects but, would give an extra degree of freedom in a geometric variable to tune the transmission spectrum. A similar study [29] was performed on subwavelength metallic slits having a CDC and it was found that the transmission resonance bands would move close to each other in the spectrum locations when decreasing the throat size of CDC
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