Optical Transmission Through Multilayered Ultra-Thin Metal Gratings

Optical transmission properties of multilayered ultra-thin metal gratings are numerically studied. The transmission spectrum has a broad stop-band with extremely low transmittance compared to that of a single-layer one for TM polarization. The stop-band is shown to be formed by multiple-interference tunneling and various plasmon resonance processes in ultra-thin-metal and dielectric multilayers. That is on the transmission background of non-apertured metal/dielectric multilayer structures that have low transmission in the long-wavelength range due to destructive multiple-interference tunneling, the transmission is further suppressed in the stop-band by plasmon resonances in the top metal/dielectric layers, e.g., the anti-symmetric bound surface plasmon mode in the ultra-thin metal layer and the gap surface plasmon mode in the metal-sandwiched dielectric layer. High transmission beyond the stop-band is due to coupled gap surface plasmon mode in the entire multilayer structures. Applications of the optical properties of the multilayered ultra-thin metal gratings are suggested for optical filtering (wavelength or polarization selective).