Guided-mode resonance in tunable orthogonal grating

In this paper, we present a new tunable orthogonal grating consisting of two weakly modulated subwavelength gratings perpendicularly to one another. Using the rigorous coupled-wave analysis (RCWA), we calculate and analyze the characteristics of guided-mode resonance on incident angle for TE/TM polarization. We demonstrate that a wide range tunability of such structure accomplished with only a nanoscale variation of the spacing between the gratings. For a normally incident wave of both TE and TM polarization, the structure turns out the same spectrum and resonance peaks. A gap of reflection peaks is found, and electric field distributions manifest that this gap is due to the interaction between the leaky modes of TE0-TE0, TM0-TM0 or TE0-TM0. We investigate the reflection efficiency of TE/TM polarization as a function of the wavelength with the angle of incidence as a parameter. As incident angle increases, the separation of the resonances increases also. At the same time, some specific wavelengths are maintained.