Efficient coupling of a semiconductor laser to an optical fiber by means of an adiabatic tapered waveguide on silicon

In optical communications, injection lasers need to be efficiently coupled to optical fibers. In integrated optics, it is also important to efficiently couple waveguides to both lasers and fibers. In integrated optics on silicon, low loss waveguides with loose modes1–3 that are well matched to optical fibers and a tight mode waveguide,4 with moderately efficient butt coupling to a laser, have been developed. We report an efficient adiabatic tapered transition between the tight mode and loose mode waveguides and use it to demonstrate efficient coupling from a laser to a fiber.