Two-dimensional extreme skin depthengineering for CMOS photonics

Extreme skin depth engineering (e-skid) can be applied to integrated photonics to manipulate the evanescent field of a waveguide. Here we demonstrate that e-skid can be implemented in two directions in order to deterministically engineer the evanescent wave allowing for dense integration with enhanced functionalities. In particular, by increasing the skin depth, we enable the creation of two-dimensional (2D) e-skid directional couplers with large gaps and operational bandwidth. Here we experimentally validate 2D e-skid for integrated photonics in a complementary metal–oxide semiconductor (CMOS) photonics foundry and demonstrate strong coupling with a gap of 1.44 µm.