MICROSPECTROMETER WITH SLAB-WAVE-GUIDE TRANSMISSION GRATINGS

An integrated transmission diffraction grating in a planar optical wav eguide is presented for broadband spectroscopic analysis of liquids an d gases. Silicon oxynitride slab waveguides on silicon substrates with low optical loss in the visible range are combined with a phase trans mission grating exhibiting a blaze effect at 500 nm to achieve high-ef ficiency diffraction and high spectral dispersion. Collimated white li ght propagates through the waveguide and couples into air at a stepped formed planar grating. The beams of each adjacent step interfere cons tructively at the focal line of a cylindrical lens, its focal line pos itioned perpendicular to the waveguide plane. We used a common silicon photodiode array to detect the spectral data. Our approach is to deve lop a compact and economic spectrometer without moving parts that can be applied for UV-visible analysis and near-infrared industrial proces s control as well. (C) 1996 Optical Society of America