Narrowband spectroscopy on subwavelength hole arrays in thin gold fi?lms using high-speed spectrum scanning

Abstract

Generally spectroscopy is conducted using a broadband incident light spectrum. In this study we present and evaluate a novel technique using an acousto-optic tuneable filter to filter out narrowband spectra and conduct spectroscopy measurements using these narrowbanded spectra one at a time. By scanning through the entire spectrum at high speed a full spectroscopy spectrum can be measured. This method provides a solution to increase the intensity relative to the entire spectrum of otherwise weakly present wavelengths, resulting in a better noise to signal ratio. The transmission spectroscopy is conducted on sub-wavelength hole arrays in a thin gold film. Exotic optical phenomena like extraordinary optical transmission are expected for these type of samples. However the results do not show the expected anomalies in the transmission graph. Comparing our results with transmission measurements from earlier conducted research on the same samples using a more established spectroscopy method shows a deviating outcome. Positive results are found for the measured values at the borders of the spectrum, where due to the increased relative intensity the measurements show a much clearer graph.