Method of fabricating molds for forming waveguides and related systems and methods using the waveguides

A method for forming a mold for casting, the method comprising:

• providing a substrate comprising a layer of single crystalline material;
• forming a first etch mask layer on the substrate, the first etch mask layer comprising a plurality of first holes and a plurality of second holes, the plurality of first holes aligned with a crystal axis of the single crystalline material;
• forming a second etch mask layer on the first etch mask layer, the second etch mask layer exposing the plurality of second holes while extending over the plurality of first holes;
• etching the substrate through the plurality of second holes of the first and second etch mask layers to form a plurality of second openings corresponding to the plurality of second holes;
• forming a third etch mask layer on the substrate, the third etch mask layer exposing the plurality of first holes while extending over the plurality of second openings;
• and
• etching the substrate through the third etch mask layer to form a plurality of first openings corresponding to the plurality of first holes.

A method for forming a mold for casting, comprising:

• providing a substrate comprising a layer of single crystalline material and a second etch mask layer on the single crystalline material;
• forming a first etch mask layer on the second etch mask layer, the first etch mask layer comprising a plurality of first holes and a plurality of second holes, the plurality of first holes aligned with a crystal axis of the single crystalline material;
• etching the substrate through the first etch mask layer to a depth to form a plurality of first openings corresponding to the plurality of first holes and a plurality of second openings corresponding to the plurality of second holes, wherein the depth is less than thickness of the first etch mask layer;
• forming a third etch mask layer on the substrate, the third etch mask layer exposing the plurality of first openings while extending over the plurality of second openings;
• etching the second etch mask layer through the third etch mask layer until the plurality of first openings extend to the layer of crystalline material;
• removing the first etch mask layer and the third etch mask layer;
• etching the substrate through the second etch mask layer;
• further etching the substrate through the second etch mask layer until the plurality of second openings reach a desired depth in the layer of crystalline material;
• and
• removing the second etch mask layer.