Temperature Sensitivity of Nanohole Array Sensors

Small, sensitive temperature sensors are required to develop chip-scale calorimeters for pharmaceutical and related industries. Laser illuminated nanohole array apertures (NHA) that produce extraordinary optical transmission (EOT) perform as temperature sensors and may be suitable for micro-calorimetry. We investigated NHA sensors by an experimental parametric study to determine the most sensitive configuration. Temperature sensitivity of EOT is discussed, and the results suggest that nanohole arrays enable thermal measurements with microscale spatial resolution. The sensing chip is a glass substrate with 105nm thick gold surface, illuminated with a helium–neon laser. 15 different designs were milled in a formation of 3×5 matrix. Each row has a different array size (3×3, 5×5 and 10×10) and each column has a different pitch size varying from 250nm to 450nm in 50nm increments. The aperture size was fixed at 150 nm, thus the overall size of the array varies from 0.65μm×0.65μm to 4.20μm×4.20μm. The highest sensitivity was achieved with 350nm and 400nm pitch sensors and a 10×10 array (up to8% intensity gain per 0.10°C). These conditions correspond to a predicted peak wavelength region with high transmission gradients, due to the transmission maxima, causing higher sensitivity. This behavior was consistent in all array sizes. Results also showed that even the smallest sensors are sensitive to temperature changes, and they suggest a means for designing future NHA sensors to accommodate different light sources and fluids.