Leaky Waveguide Devices as Simple Sensitive Optical Detectors for use in μTAS Applications.

Leaky Waveguide Devices (LWD) are a class of optical waveguide where light is partially confined by reflection mechanisms other than total internal reflection (TIR). Since TIR is not used, the restriction that the waveguide must have a higher refractive index than the surrounding medium can be relaxed. It is then possible to provide lossy waveguiding in channels containing aqueous solutions. Since these reflection mechanisms always provide less than 100% reflectivity, light is gradually lost from the waveguide either by absorption or by radiative loss. Although this means that LWD cannot by used for long-distance light transmission, the typical propagation distances of a few millimetres to a few centimetres is sufficient for most μTAS sensing applications. A novel laminar-flow waveguide cytometer is described which uses Leaky Wave propagation to excite fluorescence.