Low loss integrated-optical rib-waveguides in SOI

Low-loss integrated-optical rib-waveguides in SOI (silicon-on-insulator) were fabricated and characterized. Using ⟨100⟩ silicon, an oxygen dose of 1.8×10¹⁸ cm ^-2 was implanted at an energy of 200 keV at a temperature of 600°C±20°C. After the implantation an annealing step at 1300°C for 6 h in an Ar/O₂ atmosphere was performed, resulting in a 400-nm thick layer of SiO₂ buried under 200 nm of silicon. The lateral confinement of the waveguide is achieved by anisotropically etching a rib of 2.2-μm of depth and a width between 2 μm and 12 μm. The waveguides were investigated at a wavelength of 1.3 μm and 1.55 μm for TE- and TM-polarization, respectively. In the vertical direction one mode could be observed, whereas horizontally single mode behavior was found only for a rib width below 10 μm, independent of the wavelength. In addition, a waveguide with a width of 7 μm was characterized by measuring the near-field intensity distribution and comparing it to a theoretical analysis of the waveguide