Thermal Stress Birefringence in Buried-Core Waveguides With Over-Etch

Thermal stress birefringence in buried-core waveguides is studied analytically and numerically to determine the role of cladding and core composition, core aspect ratio and over-etch depth. An analytical expression is derived for the over-etch depth required for stress birefringence compensation. Analytical expressions for the core stress are given for over-etched rectangular buried-core waveguides. The range of upper cladding thermal expansion coefficient over which stress birefringence compensation can be obtained through over-etching is established.