Remarkable transmission characteristics of optical waves through modulated double-layered metallic slit arrays

We reveal the distinct wavelength dependence of not only the transmission power but also the phase change in double-layered metallic slit array systems with gradually modulated slit intervals, which are promising structures for achieving novel optical phased-array functions, through finite-difference time-domain simulations. In spite of the structural modifications, the transmittance of the non-periodic system displays waveguide mode resonance for a conventional constant-period array system. By the resonance effect, maximum phase change is achieved with sufficiently high output powers around the transmission peak wavelength, and further enhanced to values much larger than those estimated simply from the optical path.