Dual-mode surface-plasmon-resonance sensors using angular interrogation

Surface-plasmon-resonance (SPR) sensors are widely used in biological, chemical, medical, and environmental sensing. SPR sensors supporting two surface-plasmon modes can differentiate surface binding interactions from bulk index changes at a single sensing location. We present a new approach to dual-mode SPR sensing that offers improved differentiation between surface and bulk effects. By using an angular interrogation, both long- and short-range surface plasmons are simultaneously excited at the same location and wavelength but at different angles. Initial experiments indicate that angular interrogation offers at least a factor of 3.6 improvement in surface and bulk cross-sensitivity compared to wavelength-interrogated dual-mode SPR sensors.