Silicon Photonics: Fundamentals and Devices

11.5 Some Useful Planar Devices

In this section we shall mention some basic devices which are used in communication and networks and which form the basic building blocks for more complex passive and active light waveguide components.

11.5.1 Splitters

Splitters are passive waveguides that are used in branching networks for integrated optics. These networks divide optical power among two or more outputs or combine power from two or more inputs. An important commonly used branching network is the waveguide Y-structure 5, shown in Figure 11.6 which can be used as a symmetric power divider or combiner.

Figure 11.6 Schematic diagram of a splitter or Y-coupler.

The Y-structures are combined to yield 1 × N splitters. A 1 × 4 splitter is shown in Figure 11.7 using three Y-structures.

Figure 11.7 1 × 4 splitter using three Y-structures.

11.5.2 Directional Coupler

The dual-channel directional coupler is an important component that may work as both a passive and an active component in lightwave circuits. As shown already in Figure 11.2, it consists basically of parallel-channel optical waveguides sufficiently closely spaced so that optical energy can be transferred from one channel to the other. This energy transfer takes place by a process of synchronous coherent coupling between the overlapping ...