Abstract
We propose and demonstrate a spatial-mode multi/demultiplexer based on a tapered hollow waveguide with lateral optical confinement. The fabricated device shows vertical radiation spots for different transverse-modes traveling along a tapered hollow waveguide. Both multiplexing and demultiplexing functions are presented, exhibiting a potential of spatial-mode multiplexing/demultiplexing hollow waveguide devices in compact fashion. (C) 2015 The Japan Society of Applied Physics