Losses in polycrystalline silicon waveguides

The losses of polycrystalline silicon (polySi) waveguides clad by SiO2 are measured by the cutback technique. We report losses of 34 dB/cm at a wavelength of 1.55 mu m in waveguides fabricated from chemical mechanical polished polySi deposited at 625 degrees C. These losses are two orders of magnitude lower than reported absorption measurements for polySi. Waveguides fabricated from unpolished polySi deposited at 625 degrees C exhibit losses of 77 dB/cm. We find good agreement between calculated and measured losses due to surface scattering. (C) 1996 American Institute of Physics.