Guiding light in fluids

In contrast to conventional waveguides with high-refractive-index core, we describe a concept for guiding light within a low-refractive-index medium surrounded by a medium with higher refractive index. This concept is especially compatible with fluidic sensors because the channel itself can be used as the core of the waveguide and thereby enabling a strong light-analyte interaction over an extended distance. The concept is based on antiresonant modes, and experiments have shown that these modes can be excited by collimating excitation light under an appropriate angle onto the waveguide structure.