Method for producing Ge-core based waveguides

A method for producing a waveguide comprising at least one core and a cladding, the method comprising at least the following steps:

• providing a substrate;
• depositing a germanium-based (Ge-based) layer on the substrate;
• forming the at least one core of the waveguide in the Ge-based layer;
• depositing an encapsulation layer around the at least one core, the encapsulation layer having a germanium content, tGE encapsulation, such that:
• tGE encapsulation≤0.9 tGE core, where tGe core is a germanium content of the at least one core, so as to at least partially form the cladding;
• and
• before the step of depositing the encapsulation layer, depositing by epitaxy a shell around the at least one core, the shell at least partially forming the cladding and having a germanium content, tGe shell, such that:
• tGe shell≤0.9 tGe core, where the depositing by epitaxy is performed at a temperature Tshell epitaxy≤780° C.,
• wherein the encapsulation layer is deposited by epitaxy at a temperature, Tencapsulation epitaxy, such that:
• Tencapsulation epitaxy≥1.08*Tshell epitaxy, and
• wherein tGe shell≈tGe encapsulation.