Effects of Dielectric Environment on Phase Resonance in Compound Grating

Effects of dielectric environment on phase resonance in compound grating are investigated theoretically and numerically. Transmission characteristics can be effectively tailored by changing the dielectric environment. When the dielectric constants between the two slits are slightly different, the transmission spectra show obvious dips for all modes, and values of the dips are near to zero, and photon forbidden band gaps emerge with larger difference of dielectric environment. The corresponding physical mechanisms are discussed by means of effective refractive index and effective length based on F-P-like and phase resonant mechanisms. In addition, the electric field for the peak at the shorter wavelength of the dip is mainly concentrated on the slit filled with smaller dielectric constant, while the electric field located on the slit filled with larger dielectric constant for the peak at the longer wavelength of the dip. By selecting a proper dielectric environment, the channel selecting device can be constructed by using the dielectric compound grating