Characteristics of tapered rib-waveguides for high power semiconductor optical sources

Properties of passive tapered rib waveguides with a large output aperture have been measured as a function of both rib-height and taper angle in the context of high power semiconductor optical sources. It is observed that the near-field (intensity) distribution at the output aperture can be much narrower than that expected from just the fundamental mode of the waveguide at that plane. A theoretical model of the structure, based on the step-transition approximation, has been developed to analyse experimentally measured near-field profiles. The experimental and theoretical results are found to be in good agreement over a wide range of taper angles and other waveguide parameters. Also presented are the corresponding far-field patterns which are so pertinent to high power device design