Researches on the guide-mode resonance of the planar polymer sub-wavelength grating

In this paper, a planar polymer sub-wavelength grating whose period structure is modulated by different refractive index is proposed. The guided mode resonant of the proposed grating is analyzed with effective medium theory and the eigenvalue equation of the thin film waveguide, and the reflectance properties of the grating are simulated with rigid coupled-wave analysis. The reflectance property shows obvious polarization dependent. The influences of the grating period, thickness and the incident angle on the resonant wavelength are also analyzed. It is shown that the resonant wavelength shows redshift with the increase of grating period, dual resonant peaks occur when the grating thickness is of some certain values, and the resonant peak of normal incidence will split into 2 peaks on the condition that oblique incidence. This planar polymer sub-wavelength grating may find application in filters, polarization elements, reflectors and so on.