Proceedings Article | 1 May 2012
Proc. SPIE. 8424, Nanophotonics IV
KEYWORDS: Gold, Plasmonics, Nanostructures, Refractive index, Surface plasmons, Sensors, Metals, Dielectrics, Interfaces, Absorption
We demonstrate the surface plasmon grating coupled emission (SPGCE) from excited organic layer on metal grating in
organic/metal structure. The emissions correspond to the resonant condition of SPPs modes on the Alq<sub>3</sub>/Au interface and
grating couple to the Au/air interface for the emission of light. In our experiments, we used different pitch sizes to
control plasmonics band-gap which produced highly directional SPGCE with enhanced intensity. In our experiments,
four different pitches, including 400 nm, 500 nm, 600 nm and 800 nm, were adopted for the one-dimensional lamellar
grating devices. They were grating devices with 1-D pattern an exposure area of 1.2×1.2 mm<sup>2</sup> fabricated by
Electron-Beam Lithography system. The experimeantal and theoretical results showed that SPGCE at different pitch can
match a linear shifting of momentum (ΔK) of about 4.8 μm<sup>-1</sup> per 100 nm pitch size with 4 times enhanced intensity. We
have to modify our experimental design of decreasing Au thin film thickness, it became more pronounced in the 20 nm
Au film at the pitch of 600 nm structure. In this study, the emission filtering is enabled by evanescent wave coupling
across the upper layer metal film. In this way, we can probe the response of the SPGCE system when the two modes are
brought into resonance. In our experiments, we used different pitch sizes to control plasmonic band-gap which produced
highly directional SPGCE with enhanced intensity. Based on our calculation, SPGCE showed a color change from
yellowish green to orange at a certain viewing angle, while the concentration of contacting glucose was increased from
10 to 40%, corresponding to the refractive index change from 1.3484 to 1.3968. This indicated a potential application of
low-cost, integrated, and disposable refractive-index sensor. It is proposed for the development of novel bio-devices,
which is expected to improve the capability of electroluminescent bio-plasmonic devices in the future.
