Observation of low optical overlap mode propagation in nanoscale indium phosphide membrane waveguides

The authors have developed a nanoscale, rib-loaded waveguide that propagates a low optical overlap mode (LOOM) in which less than 1% of the modal field energy resides in the semiconductor material. Because of the small modal fill factor, the potential for extremely low waveguide propagation loss, on the order of 0.001 dB or less, is predicted. Elevated membrane waveguides, 50 nm thick with a 50 nm thick rib, have been fabricated in InP using a multistep microelectromechanical release process. Both transverse electric and transverse magnetic LOOM propagations have been observed and measurements are compared to theoretical predictions.