Optical waveguides having flattened high order modes

A waveguide for guiding a field-flattening preferred mode at a preferred mode effective index, comprising:

• a plurality of field-flattening regions, wherein each field-flattening region of said plurality of field-flattening regions comprises a field-flattening region inner boundary, a field-flattening region outer boundary and a field-flattening region refractive index, wherein said field-flattening region refractive index does not vary substantially within said each field-flattening region of said plurality of field-flattening regions, and said field-flattening region refractive index is substantially equal to a preferred mode effective index, to thus induce the field associated with the field-flattening preferred mode to not vary substantially with position within said each field-flattening region;
• one or more stitching regions, wherein a stitching region of said one or more stitching regions is located between neighboring said each field-flattening region, wherein each said stitching region comprises a stitching region inner boundary, a stitching region outer boundary, and a stitching region refractive index structure, wherein said stitching region refractive index structure comprises means for inducing the field of said preferred mode to vary substantially with position within said stitching region and means for inducing the gradient of the field of said field-flattening preferred mode to be zero or nearly zero at said stitching region inner boundary and at said stitching region outer boundary;
• one or more terminating regions, wherein each terminating region of said one or more terminating regions comprises a terminating region inner boundary, a terminating region outer boundary, and a terminating region refractive index structure, wherein said terminating region inner boundary is in contact with one said field-flattening region outer boundary;
• and
• a cladding region comprising a cladding region inner boundary and a substantially homogeneous cladding refractive index, wherein said cladding region surrounds all said plurality of field-flattening regions, surrounds all said one or more stitching regions, and surrounds all said one or more terminating regions, wherein said cladding region inner boundary is in contact with said terminating region outer boundary of all of said one or more terminating regions, wherein each said terminating region refractive index structure of said one or more terminating regions comprises means for inducing the field of said field-flattening preferred mode to transition from the field at said terminating region inner boundary to a decaying field in said cladding region.