Improved Determination of the Design Parameters and the Strongly Non-Gaussian Field Distribution of Semiconductor Waveguides matched to Single-mode Fibers

Abstract

Integrated spot-size transformers using waveguide tapers have proved to be an advantageous solution for low-loss chip-to-fiber coupling with large alignment tolerances. For an optimized fabrication of such a structure the precise knowledge of the eigenmode field distribution of the large-spot output waveguide is required. A new method is presented for the determination of the intensity distribution based on near-field measurement by transversal scanning combined with a numerical calculation. Although the investigated integrated spot-size transformer on InP has in the vertical direction a strongly non-Gaussian field distribution, a good agreement between the measured and simulated intensity distributions was found.