Experimental technique for quick and efficient lensed fibre to ridge waveguide coupling

The authors describe a fast and efficient technique for lensed fibre to waveguide coupling, based upon imaging the waveguide facets. In this technique, the lensed fibre is scanned across a ridge waveguide facet while the reflected power from the facet is measured through a circulator. The measurements allow for the facet to be imaged and the lensed fibre location that provides optimum coupling can be determined. The technique provides an optimal method of coupling light into micron-scale passive waveguide structures, with an efficiency close to that of the theoretical limit.