Liquid-Core Waveguide Sensors

Abstract

Much of chemistry and biology involves liquid substances. It is, therefore, not surprising that a strong need for instruments that can sense the presence, absence, or properties of liquids and their constituents exists in both of these vast fields. The miniaturization paradigm that has driven many industrial developments, including the area of sensors, provides a strong push to use optical waveguides for implementing sensing functions in compact, robust, and convenient form. The most direct approach is the use of liquid-core waveguides, in which both light and liquids are guided through the same physical space, thus providing the most efficient interaction between the two. Fueled by recent developments of novel types of liquid-core waveguides, these devices are rapidly moving to the forefront of research and development of biological and chemical sensors. Here, we take a closer look at liquid-core waveguides by discussing the physical principles underlying the most important waveguide types, discussing the most popular optical sensing modalities, and reviewing representative examples for liquid-core waveguide-based chemical and biological sensors.