Silicon nitride waveguide router enabling directional power transmission

A passive guided-wave router featuring directional power transmission among three different input/output ports has been proposed and demonstrated, taking advantage of appropriately disposed straight and bent waveguides in silicon nitride. The proposed router consists of a straight waveguide and a curved waveguide of the same width, which are brought together with a small offset between them and are interconnected together to another curved waveguide of an enlarged width. Due to the passively directional steering of excited guided modes induced by the device configuration, a three-port guided wave router is demonstrated where a signal input from Port I passes to Port II, but a signal fed from Port II is directed to Port III instead of Port I, providing a good contrast level of 14 dB at λ=1546 nm for forward and backward transmissions. Insertion losses of 4.6 dB and 1.2 dB were respectively obtained for the routes from Port I to Port II and from Port II to Port III. Due to the absence of active control and the use of conventional linear materials, the proposed passive router featuring a compact configuration will play a pivotal role in creating fully functional on-chip photonic circuits.