Abstract
The optical transmission properties of squarely-modulated metallic gratings has been widely investigated. This study used rigorous-coupled wave analysis (RCWA) to re-examine in detail the band structure of a laminated metal film with squarely-modulated metallic gratings located at the top. The top structure was shown to modify the long-range surface plasmon polariton modes (LRSPP) at both interfaces of the thin metal film. When the thickness of the intact metal film was altered, the coupling between the two interfaces presented intriguing behavior. If the thickness of the metallic film was 30nm, the field achieved strong coupling similar to that of a two-level system. When the thickness was decreased to 10nm, the band branch possessing negative group velocity was dominant. Our results also verify that the first-order Fourier expansion of the gratings determined the energy position of bands at k||=0, whereas the second-order term caused band gap opening. Introducing an asymmetrical component to the grating profile intensified the opening effect at k||=0 due to an increase in the amplitude of the second-order Fourier component.
Highlights
The extraordinary transmission (EOT) effect has attracted considerable attention over the past two decades.[1]
Groups 1 and 3 results are associated with coupling between gratings and the longrange surface plasmon polariton modes (LRSPP) mode at the lower Ag film/glass interface, whereas group 2 results are from coupling between gratings and the LRSPP mode at the upper Ag grating/air interface
This paper presents reflection diagrams of squarely-modulated metallic gratings on a thin metal film substrate
Summary
The extraordinary transmission (EOT) effect has attracted considerable attention over the past two decades.[1]. The second-order term breaks the mirror symmetry of the first-order gratings, such that the two types of standing wave revealed different portions of the asymmetrical profile of the optical refractive index, the degeneracy of the two splits up.[25] The second component makes it possible to tune the gap.[25,26,27] This study deals with the process of band folding by a grating structure and the coupling between the two interfaces of continuous films of various thickness. When the thickness of the continuous film was reduced to zero, the discrete metallic stripes presented smaller corner field intensity comparing to that observed in LRSPP-assisted modes (i.e. when the continuous film is 50nm thick) This is a clear indication that these experiments involving surface enhancement did not have a favorable effect on the structure of the discrete stripes. The insight provided by band diagrams and field distributions could facilitate the development of more effective devices using alternative approaches to design
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
