Tunable on-chip variable ratio optical coupler comprising phase change material

A variable ratio optical coupler comprising:

• a plurality of waveguides including first, second, and third waveguides arranged in or on a primary substrate, a portion of the second waveguide is arranged proximate to the first waveguide at a first coupling region, and a portion of the third waveguide is-arranged proximate to the first waveguide at a second coupling region;
• phase change material arranged over the first waveguide at the first coupling region and arranged over the first waveguide at the second coupling region;
• a first electrode segment arranged over the phase change material at a first overlap region overlying the first coupling region, the first electrode segment being arranged to receive an electrical signal configured to heat the first electrode segment to permit adjustment of a degree of transition between a crystalline state and an amorphous state of the phase change material at the first coupling region;
• and
• a second electrode segment arranged over the phase change material at a second overlap region overlying the second coupling region, the second electrode segment arranged to receive an electrical signal configured to heat the second electrode segment to permit adjustment of a degree of transition between a crystalline state and an amorphous state of the phase change material at the second coupling region.