Thermal tuning of surface plasmon resonance: Ag gratings on barium strontium titanate thin films |
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Authors: | J?Z?Xin K?C?Hui K?Wang H?L?W?Chan D?H?C?Ong Email author" target="_blank">C?W?LeungEmail author |
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Institution: | (1) Department of Applied Physics and Materials Research Centre, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, China;(2) Department of Physics, The Chinese University of Hong Kong, Shatin, Hong Kong, China; |
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Abstract: | Surface plasmon tuning via thermally induced refractive index changes in ferroelectrics is investigated. Epitaxial (Ba0.7Sr0.3)TiO3 (BST) thin films were deposited on MgO (001) substrates by pulsed laser deposition. The refractive index of BST thin films
measured by the prism-coupling technique was found to increase from 2.3932 (TE)/1.9945 (TM) at room temperature to 2.3949
(TE)/1.9965 (TM) at 66°C. Then 30-nm-Ag gratings with periodicity 750 nm and width 300 nm were fabricated on BST by soft ultraviolet
nanoimprint lithography and subsequent lift-off process. The reflection spectra from 500 to 1000 nm with incident angle from
5° to 60° were measured at room temperature and 66°C, with a collimated and p-polarized light incident perpendicularly to the grating direction. Several modes were observed from the spectra. At 66°C,
a red shift of a dip at about 850 nm by 2 nm was obtained at an incident angle of 15°. Calculations confirmed that the observed
modes belong to the (−1), (2), (−2) and (3) surface plasmon modes from the Ag and BST interfaces and localized mode; the red
shift by thermal tuning is also confirmed. The results indicate the feasibility of active modulation in surface plasmon resonance
in solid-state structures. |
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