Arrange an asymmetrical metal-dielectric multilayer as a low loss metamaterial

A metal-dielectric (M-D) multilayer has been applied as a subwavelength structure to exhibit the negative index of refraction. Periodic MD multilayer or symmetrical five layered MDMDM multilayer has been arranged to exhibit an equivalent complex refractive index with negative real part. As the extinction coefficient is much smaller than the index of refraction, the wave vector and Poynting vector are in opposite directions. How to reduce the extinction coefficient and raise the transmittance becomes an issue. In this work, the metal films within the multilayer are not arranged with the same thickness as well as dielectric films. The thickness of each layer is tuned to increase the transmittance. The previous example of a five layered MDMDM as a negative index metamaterial at a wavelength of 363.8nm is adopted here to do the improvement of loss. The near field simulation is also adopted here to observe the backward wave propagation as a negative refraction phenomenon.