Optical properties of pseudomorphic Si1-xGex for Si-based waveguides at the lambda = 1300-nm and 1550-nm telecommunications wavelength bands

The index of refraction for pseudomorphic Si1-xGe4, layers grown on Si has been measured at wavelengths lambda = 1310 nm and lambda = 1550 nm, The ref ractive index values were obtained from waveguide mode profile measurements on a series of SiSi1-xGexSi waveguides with Ge concentrations between x = 0.01 and x = 0.1, The index of refraction n, is significantly larger for li ght polarized parallel to the growth direction than for light polarized in the plane of the epilayer. This birefringence is consistent with the anisot ropic index change predicted using photoelastic theory given the biaxial st rain present in the pseudomorphic Si1-xGex layers. At all wavelengths and p olarizations, n varies linearly with the Ge concentration. The pseudomor-ph ic Si1-xGex waveguides layer are stable against lattice relaxation during s hort anneals at 950 degrees C, but exhibit partial relaxation after anneali ng at 1200 degrees C.