Controlling the spectral width in compound waveguide grating structures

Spectral responses in compound waveguide grating structures composed of two ridges with identical widths in each period are presented. For the proposed structures, we show that the spectral width of the guided-mode resonance (GMR) can be tailored in an independent way without modifying the spectral lineshapes and sideband levels. The method described in this Letter offers a very simple and efficient way to control spectral responses in GMR structures.