Investigation of subwavelength grating structure for enhanced surface plasmon resonance detection.

A metallic subwavelength grating structure built on a thin gold film is studied for surface plasmon resonance (SPR) detection of refractive index variations of biological buffer solutions. By employing finite element analysis as a numerical method, characteristics of the angle interrogated SPR sensor were calculated and discussed in a broad operating wavelength varying from visible to near-infrared (NIR). The effects of grating structural parameters such as grating depth, grating period, and grating fill factor in different operating wavelengths have been evaluated on the sensor performance parameters of sensitivity, full width at half-minimum, minimum reflectance at resonance, and resonance angle. Numerical results indicate that adjusting grating geometrical parameters can enhance the performance parameters of the sensor especially in the NIR wavelengths. The enhanced sensor performance parameters for optimizing grating geometry have been explored in detail for visible and NIR wavelengths of 633 and 984 nm, respectively. These findings are important for developing localized surface plasmon sensors with enhanced performance.