Enhancing angular sensitivity of plasmonic nanostructures using mode transition in hexagonal gold nanohole arrays

• Published in: Sensors and actuators. B, Chemical Vol. 241; pp. 800 - 805
• Main Authors: Lin, En-Hung, Tsai, Wan-Shao, Lee, Kuang-Li, Lee, Ming-Chang M., Wei, Pei-Kuen
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 31-03-2017; Elsevier Science Ltd
• Subjects: Angular sensitivity; Arrays; Biosensors; Dispersion; Dispersion curve analysis; Gold; Gold nanohole array; Mathematical analysis; Mode transition; Nanostructure; Nanostructured materials; Plasmonics; Plasmons; Sensitivity; Sensitivity enhancement; Sensor arrays; Sensors; SPR biosensor; Angular sensitivity; Mode transition; SPR biosensor; Gold nanohole array
• ISSN: 0925-4005; 1873-3077
• DOI: 10.1016/j.snb.2016.10.149

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•A large-area hexagonal gold nanohole array based sensor with an angular sensitivity up to 440°/RIU was presented.•A flat dispersion curve occurred at large incident angle due to surface to cavity mode transition increased the angular sensitivity.•The FDTD calculations verified the flat band was due to plasmonic field redistributed from SPR mode to cavity mode in the nanohole.•The angular sensitivity of the (±1,∓1) mode near the flat band was 6.2 times higher than SPR mode near 0° incidence.
We presented a surface plasmon resonance (SPR) sensor with an angular sensitivity up to 440 deg/RIU by using (±1,∓1) mode on a hexagonal gold nanohole array. The large-area gold nanohole arrays were fabricated by thermal-annealing template-stripping method with 180-nm-hole diameter and 600-nm period. A flat dispersion curve deviated from Bragg condition for (±1,∓1) mode occurred when incident angle was larger than 20°. The finite-difference time-domain calculations verified that plasmonic mode changed from surface plasmon mode to cavity mode in nanoholes. Such mode transition resulted in the large change of dispersion curve. The angular sensitivity of the (±1,∓1) mode near the transition band was 6.2 times higher than surface plasmon mode under Bragg condition and 4.5 times higher than prism-based SPR sensors at 850nm wavelength. Biosensing experiments for antigen-antibody interactions verified the surface binding sensitivity was higher than prism-based SPR machine.