Enhanced transmissions at infra-red wavelengths are measured through hole arrays made in gold-covered silicon nitride free-standing membranes. The membranes are made by a standard photolithography batch process. They are cheap to fabricate, reproducible and robust. The optical transmission of the membranes are investigated with varying hole size (down to 1μm), period, and thickness. The membranes show enhanced optical transmission. The spectra show good agreement with a very simple mode matching model which can be used for design. Calculations are also shown giving absorption enhancements of 5.7 normalized to the same material on a silicon membrane. Finite difference time domain calculations are also presented to show the spatial distribution of the enhanced field. Field enhancements of 3.3 are calculated. The field enhancements are concentrated in the hole which makes the membranes ideally suited for a microfluidic setup. Hence, this paper shows that through enhanced transmission cheap, disposable membranes in a simplified transmission can be used for measurements for molecular absorption.

Date Published: 4 February 2013
PDF: 9 pages
Proc. SPIE 8631, Quantum Sensing and Nanophotonic Devices X, 86312T (4 February 2013); doi: 10.1117/12.2003037

Published in SPIE Proceedings Vol. 8631:
Quantum Sensing and Nanophotonic Devices X
Manijeh Razeghi, Editor(s)