正交双光栅结构的导模共振光谱特性

Guided-Mode Resonance Spectral Characteristics in Tunable Orthogonal Grating

将两个弱调制导模共振光栅相互垂直放置构成新型正交光栅结构。应用严格耦合波理论计算了横电/横磁（TE/TM）偏振光入射时的光谱特性,并分析了该结构的导模共振现象。研究表明,当改变两光栅间隔距离时,正交光栅结构呈现出较大的光谱可调范围（共振峰间距由0~62.7 nm连续可调）;当分别以TE/TM偏振光正入射时,两种偏振光对应的共振波长位置保持不变、光谱曲线相同,相当于平行双光栅结构对应光谱的叠加。TE/TM偏振光倾斜入射时反射峰发生分裂,同时在入射面为P1面时582.3 nm和590.8 nm共振波长位置处,及入射面为P2面时590.8 nm和612.4 nm共振波长位置处呈现出峰位随入射角的增加保持不变的特性。

A new tunable orthogonal grating consisting of two weakly modulated subwavelength gratings perpendicularly to each other is presented.Using the rigorous coupled-wave analysis（RCWA）,the spectra are calculated and the characteristics of guided-mode resonance for transverse electric（TE） and transverse magnetic（TM） polarized light is analyzed.It is demonstrated that a wide-range tunability of such structure is obtained via varying the spacing between the gratings（the distance between the two resonant wavelengths is continuously tunable from 0 to 62.7 nm）.For the normally incident waves of both TE and TM polarized light,the structure turns out to have the same spectrum and resonance peaks,and it is the same as the overlay result of parallel double grating.For the obliquely incidence of TE/TM polarized light,the separation of the resonant peaks appears.At the same time,some specific wavelengths are maintained with the increase of the incident angle,such as the resonance peaks of 582.3 nm and 590.8 nm for incident plane P1,and those of 590.8 nm and 612.4 nm for P2.