Ultraviolet transparent silicon oxynitride waveguides for biochemical microsystems

The UV wavelength region is of great interest in absorption spectroscopy, w hich is employed for chemical analysis, since many organic compounds absorb in only this region. Germanium-doped silica, which is often preferred as t he waveguide core material in optical devices for telecommunication, cannot accommodate guidance below 400 nm, owing to the presence of UV-absorbing c enters. We show that silicon oxynitride (SiOxNy) waveguides exhibit very go od UV performance. The propagation loss for 24-mum-wide SiOxNy waveguides w as found to be similar to1.0 dB/cm in the wavelength range 220-550 nm. The applicability of these waveguides was demonstrated in a biochemical microsy stem consisting of multimode buried-channel SiOxNy waveguides that were mon olithically integrated with microfluidic channels. Absorption measurements of a beta -blocking agent, propranolol, at 212-215 nm were performed. The d etection Limit was reached at a concentration of 13 muM, with an optical pa th length of 500 mum (signal/noise ratio, 2). (C) 2001 Optical Society of A merica.