Optical waveguide termination having a doped, light-absorbing slab
An optical waveguide termination includes a light-receiving inlet for receiving light to be terminated, a rib waveguide extending from the inlet, a doped, light-absorbing slab supporting the rib waveguide for absorbing light from the rib waveguide, and a tip at an end of the rib waveguide. The optical waveguide termination exhibits low back-reflection.
1. An optical waveguide termination comprising:
a doped, light-absorbing slab defining a first plane and having a width;
a light-receiving inlet of an input ridge waveguide at a first boundary of the slab;
a rib waveguide lying in a second plane parallel to the first plane and supported by the slab and extending from the inlet to a tip at an end of the rib waveguide, the width of the rib waveguide being less than the width of the slab; and
at least one transition surrounding the rib waveguide and coupling the rib waveguide to the inlet of the input ridge waveguide;
wherein the tip is spaced-apart from the boundaries of the slab to allow light to escape therefrom and into the slab and reduce an amount of back-reflection therefrom.
2. The optical waveguide termination of claim 1 wherein the rib waveguide is also doped.
3. The optical waveguide termination of claim 1 wherein the rib waveguide comprises a curved waveguide section supported by the slab.
4. The optical waveguide termination of claim 3 wherein the curved waveguide section comprises a semicircular or a spiral-shaped waveguide section.
5. The optical waveguide termination of claim 1 wherein the rib waveguide and the slab comprise silicon.
6. The optical waveguide termination of claim 5 wherein the rib waveguide and slab are formed by partially etching a silicon layer.
7. The optical waveguide termination of claim 1 wherein the tip is tapered.