Single Trench SiON Waveguide TE-TM Mode Converter

A TE-TM mode converter fabricated in a single trench SiON waveguide is described. The device has the advantage that only single masking and etching process is needed to fabricate it. We discuss the design of the mode converter from the view point of fabrication tolerance. The single trench structure is fabricated using the reactive ion-etch lag phenomenon. A 97% TE-TM mode conversion (extinction ratio=15 dB) is demonstrated at a wavelength of 1.27μm . An excess loss is measured to be 0.8 dB.