Optical coupling between a self-assembled microsphere grating and a rib waveguide

We report the fabrication of a linear array of self-assembled polystyrene microspheres side-coupled to a rib waveguide. The optical coupling between the lateral evanescent field and the periodically perturbed effective refractive index alongside the waveguide results in a transmission stopband at the Bragg wavelength. The observed transmission spectrum shows a notch centered at λ = 1590nm, which is in close agreement with theory. The coupling coefficient, K, and the spectral response are derived for variable cladding medium index using perturbation theory. Structures of this type are expected to find application in wavelength selection, optical sensing, and optical delays