Reversibly tunable plasmonic bandgap by responsive hydrogel grating

• Published in: Optics express Vol. 24; no. 3; pp. 2457 - 2465
• Main Authors: Sharma, Nityanand, Petri, Christian, Jonas, Ulrich, Dostalek, Jakub
• Format: Journal Article
• Language: English
• Published: United States 08.02.2016
• ISSN: 1094-4087; 1094-4087
• DOI: 10.1364/OE.24.002457

Reversible actuating of surface plasmon propagation by responsive hydrogel grating is reported. Thermo-responsive poly(N-isopropylacrylamide)-based (pNIPAAm) hydrogel nanostructure was designed and tethered to a gold surface in order to switch on and off Bragg scattering of surface plasmons which is associated with an occurrence of a bandgap in their dispersion relation. pNIPAAm-based grating with a period around 280 nm was prepared by using photo-crosslinkable terpolymer and laser interference lithography and it was brought in contact with water. The temperature induced swelling and collapse of pNIPAAm hydrogel grating strongly modulates its refractive index (Δn~0.1) which leads to the reversible opening and closing of a plasmonic bandgap. The experiments demonstrate partial opening of a bandgap with the width of 12 nm at wavelength around 800 nm where SPR exhibited the spectral width of about 75 nm.