Optical integrated circuit having passively aligned fibers and method using same

An interconnection assembly comprising first and second optical components having bottom sides that are mounted on the top side of a planar bridging structure,

• each component comprising a silicon substrate having a reference surface on its bottom side and a plurality of optical paths on its top side, said optical paths having central axes that reside in a plane which is positioned above the reference surface by a predetermined distance;
• the planar bridging structure having a reference surface on its top side that engages the reference surfaces of the first and second components and supports them in vertical alignment;
• CHARACTERIZED IN THAT:
• the first optical component comprises an optical integrated circuit having a plurality of passive optical circuits deposited on the top side of the silicon substrate, access to said optical circuits being provided by waveguides, also deposited on the top side of the silicon substrate, that extend from the optical circuit to a side edge of the substrate;
• each component further includes an alignment feature on its bottom side, said alignment feature having a predetermined horizontal relation to the optical paths;
• and
• the planar bridging structure further includes complementary alignment features that engage the alignment features of the first and second components and support them in horizontal alignment.

A method for providing accurate passive alignment between an optical integrated circuit (OIC) and a fiber array, both mounted on a bridging structure, said OIC comprising a silicon substrate having a plurality of longitudinally extending optical waveguides deposited on a top side thereof, said fiber array comprising a silicon substrate having an equal plurality of optical fibers disposed in longitudinally extending troughs on a top side thereof, said bridging structure comprising a planar silicon substrate, the method including the following steps:

• forming an alignment feature on the bottom side of the OIC substrate that establishes the horizontal location of the optical waveguides to within 0.5 microns;
• forming a reference surface on the bottom side of the OIC substrate that is a first predetermined distance below a plane that passes through the central axes of the optical waveguides;
• forming an alignment feature on the bottom side of the fiber array substrate that establishes the horizontal location of the optical fibers to within 0.5 microns;
• forming a reference surface on the bottom side of the fiber array substrate that is a second predetermined distance below a plane that passes through the central axes of the optical fibers, said first and second predetermined distances being equal to each other within 0.5 microns;
• forming alignment features on a top side of the bridging structure substrate that are complementary to the alignment features on the bottom sides of the OIC and the fiber array substrates;
• selecting the optical fibers for disposition in the troughs of the fiber array having outside diameters that are equal to a predetermined diameter .+-.0.3 microns;
• and
• narrowing the selection of optical fibers to ones having an eccentricity which is less than 0.15 microns.