US Patent 11016253 Adiabatic waveguide couplers with ultra-low back-reflection

An optical coupler comprises an adiabatic waveguide structure having a proximal end and a distal end, with the adiabatic waveguide structure comprising: a first waveguide comprising an input section at the proximal end; a first coupling section contiguous with the input section and extending toward the distal end; and a first laterally displaced section contiguous with the first coupling section. The first waveguide narrows along the first coupling section, from the input section to the first laterally displaced section. A second waveguide is separate from the first waveguide and comprises a second laterally displaced section adjacent to the proximal end; a second coupling section contiguous with the second laterally displaced section and extending toward the distal end; and an output section contiguous with the second coupling section. The second waveguide widens along the second coupling section, from the second laterally displaced section to the output section.