The excess optical attenuation at wavelengths around 1550nm induced by sub-amorphous dose ion implantation of silicon-on-insulator rib waveguides was quantified. Optical attenuation was related to the introduction of lattice defects such as the Si divacancy. After 2.8MeV Si+ implantation at a dose of 2.5 x 1014/cm2, the attenuation was greater than 1000dB/cm. Using positron annihilation spectroscopy to determine the vacancy-type defect concentration, it was demonstrated that the absorption component of the excess attenuation could be predicted using a simple analytical expression. Additional losses were suggested to result from a defect induced change in the real part of the refractive index of the Si waveguide. A processing strategy for ensuring that the absorption component dominates the excess attenuation was described, and it was shown that selective implantation of a relatively low dose of inert ions was an efficient method for the reduction of optical cross talk in Si photonic circuits.

Optical Attenuation in Defect-Engineered Silicon Rib Waveguides. P.J.Foster, J.K.Doylend, P.Mascher, A.P.Knights, P.G.Coleman: Journal of Applied Physics, 2006, 99[7], 073101 (7pp)