Inscription of sub-wavelength gratings with different periods based on asymmetric metal-cladding dielectric waveguide structure

Abstract

A method of fabricating sub-wavelength gratings with different periods by employing an asymmetric metal-cladding dielectric waveguide structure is proposed. Theoretical analyses of the dispersion curves of the waveguide modes and the period dependences of the sub-wavelength gratings fabricated by this method are presented herein. The results of simulations performed using the finite element method to determine the distributions of the interference fields of the waveguide modes are also discussed. The sub-wavelength gratings with various different periods can been produced using this method by changing the thickness and refractive index of the photoresist, as well as which of the waveguide modes is excited and employed. The proposed nanolithography method of fabricating sub-wavelength gratings is advantageous because of its low cost, its simplicity, and, in particular, its ability to produce gratings with various periods.