A study on thermal-stress-reliability of Si-based PLC substrate

Planar lightwave technology is rapidly advancing and promises excellent performance as economical opto-electro-devices. To confirm its feasibility, it is very important to estimate its mechanical reliability especially against the thermal stresses caused by the difference of the thermal expansion coefficients of Silicon and silica glass. This paper examines the thermal strain and stress distribution on silicon-based Planar-Lightwave-Circuits (PLC) substrates and the stress concentration on silicon terrace structures prepared for mounting active optical devices. Experimental data on the fracture strength of silicon obtained by three-point-bending tests are given. Finally, the thermal-stress-reliability of PLC substrates based on probabilistic analysis is calculated and it is confirmed that the PLC substrate, even its present form, is reliable enough for a new family of optical components.