Widely tunable directional coupler filters with 1D photonic crystal

We present two concept examples for adding a wide range tunability to Si/SiO₂ devices involving a photonic crystal element. They are based on a directional coupler filter of two different geometries, where one of the arms is a Bragg reflection waveguide (BRW) used for the bandwidth improvement. The tuning relies on changing the properties of the BRW core. As an illustration we consider the smectic A* liquid crystal as the core material and show that ca 100 nm tuning range is achievable by the core index variations of 0.006 under applying electric field of 5 V/μm.