Mechanism of opposite-side resonance in gap surface plasmon based on the design of metallic rods with phase gradient array

Cheng-Chung Lin^1*, Wei-Chen Chiu¹, Yu-Ping Kuang², Ta-Jen Yen²

¹Chemical Systems Research Division, National Chung-Shan Institute of Science and Technology, Taoyuan, Taiwan
²Department of Materials Science and Engineering, National Tsing Hua University, Hsinchu, Taiwan

* Presenter:Cheng-Chung Lin, email:dannycclin@gmail.com

In the previous studies of gap surface plasmon, resonance based on the interpretation of general Snell’s law in the formal side incidence along the forward phase gradient, with reflected wave parallel to the incident wave (normal mode), had been well demonstrated and explained. However, it has been found recently from experiment that a nearly same-scaled reflection from the opposite-side incidence along the inverse phase gradient, in which the reflected wave is also parallel to the incident wave, occurs as well. In this paper, we provide a reasonable explanation of the occurrence of such an opposite-side resonance (inversion mode). This inversion mode is due to a coincident inversion of gradient metallic rod arrangement of gap surface plasmon that can also be considered as a regular resonance based on the general Snell’s law. Such an inversion mode has been verified by simulation as well.

Keywords: gap surface plasmon, phase gradient array, inversion mode