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

A Si3N4 core waveguide, matched to a laser mode, is adiabatically tapered into a SiO2:P core waveguide, matched to a fiber mode. When used to couple the light from a semiconductor laser into an optical fiber, a loss of 3.1 dB is obtained, compared to a loss of 4.5 dB obtained with a lensed fiber.