New designs for an efficient N X N passive integrated optical star coupler are proposed in this letter. New concepts, namely, grating degeneration and sandwich structures, are presented as solutions to the dynamic range limitation problem encountered by holographic fiber star couplers. The techniques and their combinations can significantly reduce the number of gratings required by the coupler. For instance, the number of superimposed gratings is decreased from 120 to no more than 4 for a 16 X 16 coupler. This reduction makes it possible to build holographic N X N star couplers with recording materials of a moderate modulation index.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Atomic and Molecular Physics, and Optics
- Electrical and Electronic Engineering