30 April 2012 Surface plasmon coupled emission in highly directional and sensitive plasmonic devices
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Abstract
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 Alq3/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 mm2 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-1 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.
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Nan-Fu Chiu, Shih-Lin Lai, Jiun-Haw Lee, Chii-Wann Lin, "Surface plasmon coupled emission in highly directional and sensitive plasmonic devices", Proc. SPIE 8424, Nanophotonics IV, 84240A (30 April 2012); doi: 10.1117/12.922685; https://doi.org/10.1117/12.922685
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