Microminiature optical waveguide structure and method for fabrication

A method for forming microminiature optical waveguides on the surface of a substrate, comprising the steps of:

• starting with a substrate material that a molten waveguide material will wet;
• covering said substrate with a layer of material that the molten waveguide material cannot wet;
• depositing a layer of material that the molten waveguide material will wet and patterning to form a pedestal along a desired surface-contact path for a waveguide;
• depositing a waveguide material comprising at least one of polymer or doped silica;
• depositing a resist material and removing unwanted excess to form pattern masks;
• etching said waveguide material to form waveguide precursors and removing said masks;
• and
• applying heat to reflow said waveguide precursors into near-circular cross-section waveguides that sit atop said pedestals, wherein said waveguide material naturally forms nearly circular cross sections due to surface tension effects, and after cooling, said waveguides will maintain said round shape.

A method for manufacturing low-cost, nearly circular cross section waveguides, the method comprising the steps of:

• starting with a substrate material that a waveguide material will wet;
• depositing a layer of waveguide material comprising at least one of polymer or doped silica;
• depositing a resist and patterning it into a set of masks that extend along surface paths where waveguides are desired, and patterning said waveguide material such that portions of said waveguide layer that were not protected by said masks are etched away;
• removing said masks and exposing a set of waveguide precursors;
• using said waveguide precursors as masks while etching troughs in said substrate to form a trenched substrate, wherein such etch is allowed to eat away at said substrate itself for a predetermined amount of time to undercut said substrate from beneath said waveguide precursors;
• heating to reflow said waveguide precursors into near-circular cross-section waveguides that sit atop said pedestals, wherein said waveguide material forms nearly circular cross sections due to surface tension effects;
• and
• cooling said waveguides to harden them so that they can maintain said rounded shape.

A method for fabricating circular cross section waveguides and ball lenses on substrates, comprising the steps of:

• applying a set of masks on a substrate to define an ultimate location for a corresponding set of waveguides;
• etching the substrate down to form a pattern of pedestals, wherein the height and surface dimensions of said pedestals are independently controlled by photolithography and etching;
• removing the masks and attaching a layer of waveguide material by anodic or thermal bonding, or by using an adhesive;
• applying a mask to the top surface of said waveguide material and etching away unwanted waveguide material to leave a plurality of voids;
• and
• removing said masks and reflowing the remaining waveguide material to form a plurality of nearly circular cross section waveguides or ball lenses, wherein said waveguides or ball lenses self-align to said pedestals during the heat of reflow.

A method for fabricating ball lenses and waveguides on substrates, comprising the steps of:

• starting with a wettable substrate;
• applying a coat of non-wettable material to said substrate:
• applying a pattern of masks and etching the non-wettable material coat;
• removing said masks and leaving a patterned non-wettable material that will define an ultimate routing of a waveguide;
• applying a waveguide material layer;
• applying a pattern of masks on said waveguide material layer;
• etching away the waveguide material not protected by said masks to leave a waveguide precursor after said masks are washed away;
• and
• reflowing said waveguide precursors to form circular cross section waveguides or ball lenses.