COUPLING EFFICIENCY IN ION-EXCHANGED HOMOGENEOUS REFRACTING WAVE-GUIDE LENSES IN GLASS

The power transmission coefficient of the lowest-order transverse elec tric modes of homogeneous refracting waveguide lenses in glass is anal yzed on the basis of the measured near-field intensity distribution of the modes in both waveguiding lens regions. The low-index lens region was a K+-Na+ ion-exchanged waveguide and the high-index region was ma de by Ag+-Na+ ion-exchange. A single lens with propagation losses less than 0.15 dB can be fabricated using a metal mask in addition to the ''ionic'' mask for the second ion-exchange step.