A grating-coupled waveguide (GCW) and a method are described herein that can be used to detect the presence of a biological substance (e.g., cell, drug, chemical compound) in a sensing region of the GCW. The GCW includes a substrate, a diffraction grating and a waveguide film that has a higher index...http://www.google.com.au/patents/US6985664?utm_source=gb-gplus-sharePatent US6985664 - Substrate index modification for increasing the sensitivity of grating-coupled waveguides
