Tunable optical filtration using liquid nanofluids

Abstract

Optical filters are used in a wide range of applications - optical communications, electronics, optical sensors, lighting, photography and many more. In this article we report recent modelling and design work which indicates that mixtures of nanoparticles in liquids can be used as a feasible alternative to conventional thin film optical filters. The major motivation for creating liquid filters is that they can be pumped in and out of a system to meet transient needs in an application. To demonstrate the versatility of this new class of filters, we present (by comparison with conventional thin film filters) the design of nanofluids for use as long pass, short pass, and band pass optical filters using a simple Monte Carlo optimization process. For each of these types of filters we achieve < 15% mean squared deviation of transmitance from conventional filters. This analysis also revealed that nanofluid-based filters can potentially be fabricated at low cost. This is due to the fact that only extremely low particle concentrations, < 0.01% by volume, are required for effective optical filtration. Thus, this study gives a first look at how nanofluids can be used to create spectrally selective filters over any optical wavelength