title: Analysis of mode size transformation with a tapered directional coupler.
abstract: A simple tapered directional coupler with a five-layered structure is employed for mode conversion between a single-order and higher-order modes. We investigate coupling from higher-order modes to a single-order field theoretically and experimentally. As a result, we confirm that the first two modes in the tapered waveguide are coupled with a single-order mode in another waveguide by computer simulation using the beam propagation method. Furthermore, we fabricated the actual device and observed the streak patterns of the first three modes.
authors.affiliation: Faculty of Photonics Science, Chitose Institute of Science and Technology, 758-65 Bibi, Chitose, Hokkaido 066-8655, Japan. hiroshi@mail.chitose.ac.jp
authors.forename: H
authors.initials: H
authors.lastname: Komatsugawa
authors.forename: M
authors.initials: M
authors.lastname: Kamata
authors.forename: K
authors.initials: K
authors.lastname: Sasaki