Optimizing the resolution of nanohole arrays in metal films for refractive-index sensing

We optimized the resolution of nanohole arrays in metal films for refractive-index sensing by increasing the sensitivity with modifications to the hole-array parameters and by increasing the signal to noise ratio of the sensor system. The nanohole-array parameters (including film thickness, periodicity and diameter) were first optimized by finite-difference time-domain simulations, and then the arrays were fabricated and tested, showing good agreement between the two cases (theory and experiment) in terms of optimal parameters. To improve the sensitivity and to reduce the noise, the laser source wavelength was optimized (including the efficiency of the camera for detection) and the intensity was increased. A bulk resolution of 6x10(-7) refractive-index units was demonstrated. Due to the collinear microscope geometry and potential for multiplexing of nanohole arrays, these results are encouraging for future biosensing applications.