A 5-$\mu$m-Thick SOI Waveguide With Low Birefringence and Low Roughness and Optical Interconnection Using High Numerical Aperture Fiber

A 5-m-thick silicon-on-insulator waveguide possessing low birefringence of and 9-nm lithography roughness is investigated using arrayed waveguide grating and an atomic force microscope. Instead of complex processing using a 3-D mode size converter, the high numerical aperture fiber is utilized as the bridge between the corresponding waveguide and single-mode fiber (SMF-28) to obtain a competitive coupling loss of 0.4 dB.