VERY SHORT INTRACAVITY DIRECTIONAL COUPLER FOR HIGH-SPEED COMMUNICATION

We propose a novel intracavity modulator/switch that consists of a dir ectional-coupler located inside a Fabry-Perot cavity. The back mirror of the cavity has a unit reflectivity so that both input and output si gnals are at the same side. In this way we obtain a two-port, single s ide element, with coupling length of 83.5 mum, which is the shortest m odulation coupler proposed so far. The upper frequency limit due to ph oton lifetime is 275 GHz, which is well over the bandwidth constraints of microwave lumped structures. A unified approach for the analysis o f this device and other similar structures is presented and discussed.