18 May 2009 Observation of plasmon-induced optical field enhancement near a pair of partially metal covered dielectric spheres manipulated by optical tweezers
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Abstract
Optical tweezers technique combined with local confocal luminescence spectroscopy is suggested as a tool for investigation of local optical fields. Utilizing this method plasmon-enhanced optical fields inside a pair of dielectric 2 μm spheres partially covered by 70 nm silver nanoparticles are visualized via field enhanced luminescence of rhodamine dye solution. Positions of the particles are controlled with submicrometer accuracy by two optical traps formed by strongly focused laser beams with λ=980nm. A supplementary beam from CW laser with λ=532nm provided for luminescence excitation is also focused into the sample cavity just to the trapping area. In order to obtain spatial filtering of the signal and separate luminescence signal from an area near the spheres pin-hole based confocal system is designed. The focal volume available for luminescence signal collection turns out to be approximately 3μm x 3 μm x 5 μm. Since optical field is enhanced in the region near plasmon-active 2 μm spheres the enhancement of luminescence intensity is observed. Collective plasmonic effects in two-particle measurements are also considered.
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Alexander G. Zhdanov, Andrey A. Fedyanin, Satish Rao, Mark Kreuzer, Stefan Ballint, Dmitri Petrov, "Observation of plasmon-induced optical field enhancement near a pair of partially metal covered dielectric spheres manipulated by optical tweezers", Proc. SPIE 7356, Optical Sensors 2009, 735620 (18 May 2009); doi: 10.1117/12.820784; https://doi.org/10.1117/12.820784
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