EMBOSSABLE GRATING COUPLERS FOR PLANAR WAVE-GUIDE OPTICAL SENSORS

Planar optical waveguides are an attractive tool for use in analytical chemistry and spectroscopy. Although similar to fiber optics, planar waveguides have been slow to be commercially accepted due to the diffi culty of coupling light into the guide. Generally, prism coupling is t he method of choice in the laboratory, as efficiencies approaching 80% can be reached. However, prisms are impractical for routine use for s everal reasons: expensive positioning equipment is required, coupled p ower is sensitive to environmental fluctuations, and prism coupling pr ohibits the fabrication of a truly planar device. The use of thin grat ings on the surface of the waveguide allows for a two-dimensional stru cture to be maintained, while providing enough efficiency to be useful as a sensor. Our research efforts focus on developing a technique to make inexpensive, reproducible gratings that are easy to fabricate. By chemically modifying the surface of a commercial grating with a suita ble release agent, it is possible to emboss replica gratings onto a va riety of waveguide types. The fabrication of embossed gratings will be described, and their performance on glass, ion-diffused, polymer, and semiconductor waveguides will be presented.