Fabrication, Characterization and Loss Analysis of Silicon Nanowaveguides

Low loss silicon waveguides are the key to the realization of high performance photonic integrated circuits. In this paper, fabrication, characterization and loss analysis of silicon nanowaveguides are presented. Silicon nanowaveguides are fabricated on silicon-on-insulator (SOI) wafers with 0.13 mu m complementary metal-oxide-semiconductor (CMOS) technology. To reduce the propagation loss, both photolithography and etching processes are optimized to make the waveguide sidewalls smooth. Propagation losses of 2.4 +/- 0.2 and 0.59 +/- 0.32 dB/cm are obtained at 1550 nm wavelength for TE and TM modes, respectively. A theoretical method is used to estimate the propagation losses for TE and TM modes. Scattering losses from both sidewalls and top/bottom surface are considered. The calculated results show that loss comes from sidewall roughness is the main source of propagation loss for TE mode while for TM mode, losses from both sidewall and top/bottom surface contribute comparably to the total propagation loss. The theoretically estimated propagation loss agrees well with the measured results.