提出将均质多层膜系设计中的缓冲层概念引入到反射导模共振(GMR)滤光片的设计中,通过严格的耦合波理论精确计算,研究了加入缓冲层对改善导模共振滤光片反射峰边带截止深度及截止宽度的作用。双层导模共振滤光片结构中,入射光为TE偏振光时,设计增加97.5 nm缓冲层后,能够明显地展宽反射光谱范围。由原来的192.4 nm展宽到345.6 nm,并且在650～1250 nm波长范围内的边带截止度均比不含缓冲层结构的要深。入射光为TM偏振光,以类似TE结构的滤光片在布儒斯特角入射时,在700～1300 nm波长范围内,较不含缓冲层的结构,也能够获得更宽的截止带反射光谱和更深的截止度。在提出的膜系结构中,经过优化膜系、选择合适的光栅参数等,可以使反射光谱具有更好的截止特性,同时保证设计的共振峰位置不变。

Guided-mode resonance (GMR) reflection filter is presented by adding a buffer layer which is used in design of homogeneous thin-film reflection filters. We use the rigorous coupled-wave theory for studying the improvement of buffer layer to cut-off properties of reflection spectra. For the double layers structures under a TE-polarized plane wave illumination, the width of reflection spectra is broadened obviously from 192.4 nm to 345.6 nm by adding a buffer layer 97.5 nm, and the reflected sideband depressed more than the structure without buffer layer in the wavelength range of 650～1250 nm. Analogously,the similar structure under a TM-polarized plane wave illumination at the Brewster angle can obtain wider cut-off spectral range and lower reflectance than the one without buffer layer in the range of 700～1300 nm. By optimizing the structures and choosing the compatible parameters of grating, we can get better cut-off properties of reflection spectra and hold the line on the resonant wavelength.