Numerical Analysis of the Effect from the Si Substrate Thinning and Its Back Silica on Stress Birefringence of Silicon Waveguide

The relationship between stress distribution of silica on silica waveguide and Si substrate thickness or thickness of silica at the back of Si during sintering has been analyzed theoretically using a finite element method.At the same time,the stress birefringence of waveguide has been also analyzed by the full-vector finite difference beam propagation method.The results showed that the stresses between horizontal direction and perpendicular direction become equal gradually with decreasing of the Si thickness,and the birefringence index is less than 10-4.The birefringence index increases slightly due to the silica at the back of Si,and the increasing quantity becomes weaker with increasing of silica thickness.