Enhancing extraordinary transmission of light through a metallic nano slit with a nano cavity antenna

TL;DR

This paper demonstrates that a nano cavity antenna can significantly enhance light transmission through a nano slit in a metal film, with tunable spectrum and substantial transmission improvements, by optimizing the antenna's resonant conditions.

Contribution

It introduces the concept of using a nano cavity antenna to enhance and tune light transmission through nano slits, a novel approach not previously studied.

Findings

Transmission can be enhanced by about 20 times for non-resonant slits.

Transmission can be increased by 124% for resonant slits.

The transmission spectrum can be tuned by adjusting the nano-strip width.

Abstract

The extraordinary transmission of light through a nano slit in a metal film is enhanced by introducing a nano cavity antenna formed by a nearby metallic nano-strip over the slit opening. For a fixed wavelength, the width of the metallic nano-strip should be chosen to make the horizontal metal-insulator-metal waveguide of finite length resonant as a Fabry-Perot cavity. When such a cavity antenna is used to enhance the transmission through a non-resonant nano slit, the slit should be opened at a position with maximal magnetic field in the horizontal resonant cavity. It is shown that an optimized cavity antenna can enhance greatly the transmission of light through a non-resonant nano slit (by about 20 times) or a resonant nano slit (by 124%). The transmission spectrum of the nano slit can also be tuned by adjusting the width of the metallic nano-strip. Such a transmission enhancement with a nano cavity antenna is studied for the first time and the physical mechanism is explained.