At&t Bell Laboratories

Mark E Kuznetsov

Charles H Henry

Leonard G Cohen

Rudolf F Kazarinov

The present invention relates to a new tunable filter which, when used as an intracavity mode selecting filter in a semiconductor laser structure, provides a large tuning range. The disclosed filter is, in one embodiment, a two branch asymmetric Y-branch tunable filter where the ends of the two branches terminate at a common plane. In another embodiment, the invention is realized by using a cascade of two or more Y-branches to place several asymmetrical Y-branch filters in parallel.

Asymmetric Y-branch optical device

We describe an interferometric, channel-dropping, optical filter that includes a pair of planar waveguides. The two waveguides are spaced apart by a distance which is periodically varied along the longitudinal axis of the filter in order to effect a periodic optical coupling between them. There are at least three coupling locations, each associated with a coupling constant. The two waveguides have nominally equal effective refractive indices. In preferred embodiments of the invention, the coupling constants decrease symmetrically from the center of the filter toward the ends.

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East Brunswick, NJ, United States of America

Mark E Kuznetsov