Deep wet etching of fused silica glass for hollow capillary optical leaky waveguides in microfluidic devices

We report on a technology for the fabrication of hollow capillary optical l eaky waveguides in fused silica glass. The fabrication process is based on lithography, wet chemical etching and aligned direct bonding. We have devel oped a single-layer photoresist soft mask which allows for channel etch dep ths up tu 33 mum in fused silica glass. To our knowledge, such etch depths have never been achieved before in fused silica glass with single-layer sof t etch masks. Aligned direct g lass-glass bonding is used for the first tim e to obtain channels with almost circular profiles with diameters between 1 6 and 66 mum. Capillary optical leaky waveguides embedded into microfluidic devices can be used, for example, for capillary electrophoresis and hyper Rayleigh scattering.