Experimental investigation of resonant-grating filter lineshapes in comparison with theoretical models

Resonant-grating lineshapes are compared with results from a previously derived approximate coupled-mode analysis [J. Opt. Soc. Am. A 14, 629 (1997)] and to rigorous coupled-wave analysis. Tunability in resonant position (wavelength and angle) and lineshape is achieved by a novel method involving immersion of a bare resonant-grating structure in various liquids, each with a different refractive index. A comparison is made of different filter features-resonant position, efficiency, and angular width-in the experimental results and the theoretical models. The use of coupled-mode theory allows an intuitive picture to be associated with the observed trends in filter characteristic versus refractive index. This investigation reinforces the idea that the use of coupled-mode theory for resonant-grating analysis can simplify filter design. (C) 1998 Optical Society of America.