Patent ID: 8267583

Claim:
A multi-chip module (MCM), comprising a first substrate having a first surface and a second surface, wherein the first substrate includes an opening that extends through the first substrate, wherein the opening is defined by an edge in the first surface, an edge in the second surface, and a side wall, and wherein, disposed on the first surface, the first substrate includes: a first optical waveguide; a first optical coupler, optically coupled to the first optical waveguide, configured to redirect an optical signal from the first optical waveguide to a first direction, or from the first direction to the first optical waveguide, wherein the first direction is other than in the plane of the first surface; and a second optical coupler, optically coupled to the first optical waveguide, configured to redirect the optical signal from the first optical waveguide to a second direction, or from the second direction to the first optical waveguide, wherein the second direction is other than in the plane of the first surface; wherein an optical path associated with the second direction passes through the opening; and wherein a given optical coupler, which can be either the first optical coupler or the second optical coupler, comprises an element with a spatially varying index of refraction that is provided by alternating layers of material disposed on the first surface.