Abstract
Surface plasmon polaritons are electromagnetic surface waves, which, due to their nanoscale nature, are efficiently used for modifying an output of optical field through a metallic nanoslit, e.g., extraordinary optical transmission and beaming of light. Herein, the phenomenon of optical beaming by employing a regular array of semicylinder-shaped grooves around a nanoslit has been investigated based on numerical simulations. By analyzing the behavior of Poynting vectors in near surroundings of the slit, we have successfully demonstrated that grooves which are embedded on the layer at the exit side of the slit produce enhanced directionality of the output light than the unembedded ones. In case of semicylinder-shaped grooves, the calculated intensity of the output beam was 1.5-times, at near and far distances, higher than that of the grating grooves. Our analysis shows that positioning of the groove right at the exit of the slit is crucial for the enhancement of the beaming effect. This is due to the conversion of surface plasmon polaritons into a freely propagating field and the possible excitation of localized surface plasmons because of the presence of nanogroove. Furthermore, the proposed geometries are made of Aluminum, which is a plasmonic material and commonly applied for the fabrication of optical nanostructures. Manipulating of light (beaming, focusing/guiding, and splitting) by nanoslit can be beneficial to several applications such as nano-resolution optical imaging, sensors, and plasmonic circuits.
Highlights
Surface plasmon polaritons are electromagnetic surface waves, which, due to their nanoscale nature, are efficiently used for modifying an output of optical field through a metallic nanoslit, e.g., extraordinary optical transmission and beaming of light
Surface plasmon polaritons (SPPs) are electromagnetic surface waves that propagate at a metal and a dielectric interface
It has been reported that SPPs can mediate the optical transmission through a nanoslit that is perforated in a metallic sheet[13]
Summary
Surface plasmon polaritons are electromagnetic surface waves, which, due to their nanoscale nature, are efficiently used for modifying an output of optical field through a metallic nanoslit, e.g., extraordinary optical transmission and beaming of light. This study employs numerical simulations based on finite element method to further probe into the phenomenon of light beaming with a nanoslit surrounded by a regular array of parallel 1D nanostructures of a semicylinder shape. This study highlights a significant beaming effect of semicylinder-shaped grooves patterned around a nanoslit It throws more insight into the contribution of both SPPs and localized surface plasmons in the enhancement of light transmission through a slit. The investigation further contributes to the creating of awareness on the significant influence of groove position around the slit on optical beaming This kind of study of light directionality could be beneficial to several applications such as nano-resolution optical imaging, sensors, and plasmonic circuits. Unlike the other commonly used plasmonic materials, e.g., Ag and Au30,31 etc., Al is less reactive with the environment and commonly applied for fabrication of nanostructures[32,33]
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