Surface plasmon resonance sensor based on diffraction grating with high sensitivity and high resolution

A surface plasmon resonance (SPR) sensor based on diffraction grating with high sensitivity and high resolution is proposed. The sensitivity of grating coupled SPR sensor based on angular interrogation is enhanced by replacing +1st diffraction order of metallic grating with −1st diffraction order to excite the surface plasmon. To improve the resolution of grating-based SPR sensor, aluminum is used as an SPR-active metal. The reflectivity dip of the Al-based sensor is sharper than an Au-based one, which is the mostly widely used as SPR-active metal. And 3-nm-thick gold film is deposited on the grating surface in order to protect the Al layer from getting oxidized. Numerical simulations show that the sensor not only has high sensitivity and high resolution, but also exhibits good linearity.