Two-stage expanded beam optical coupling

A method for fabricating a silicon-based photonic chip that comprises an interface for optically coupling the photonic chip to an optical fiber or an optical fiber assembly, wherein the method comprises:

• fabricating a single-mode waveguide configured to guide light and to provide a first light beam;
• fabricating a first optical element, wherein the first optical element is configured to expand the first light beam in a first direction that is in-plane relative to the photonic chip and to confine the first light beam in a direction that is perpendicular to the plane of the photonic chip, thereby providing an expanded light beam;
• and
• fabricating a second optical element, wherein the second optical element is configured to deflect the expanded light beam and to further expand the expanded light beam in a second direction that is perpendicular to the first direction, thereby providing an output light beam out of the photonic chip having a beam dimension in the first direction that is the same as a beam dimension in the first direction of the expanded light beam provided by the first optical element.