Surface plasmon based sensor with order-of-magnitude higher sensitivity to electric field induced changes in dielectric environment at metal/nematic liquid-crystal interface

• Exceptionally sensitive surface plasmon based electro-optical device for electric field induced changes in the dielectric environment at metal/dielectric interface.
• Direct evidence for the surface topography mediated alignment of liquid crystal molecules on gold surface.
• Surface plasmon polariton mediated diffraction effects.

A highly sensitive surface plasmon based sensor is developed for monitoring changes in the dielectric environment at metal/dielectric interfaces. It consists of high-index prism/30–40 nm gold/nematic liquid crystal (E44)/indium-tin-oxide/glass structure, which enables measurements of surface plasmon resonance (SPR) curves by using the Kretschmann configuration. The baseline sensitivity of the device to changes in the refractive index is evaluated by using Au/air, Au/water, and Au/nematic liquid crystal (E44); the measured baseline sensitivity is in excellent agreement with theoretically predicted optimal sensitivity. The sensitivity of the device to electric field induced changes in the refractive index of the material at the interface, however, is 28-times higher than previously known value for a similar sensor. Effects related to the periodic alignment of the liquid crystal on gold surface and surface plasmon mediated diffraction are investigated.