Mode matched Y-junction

A splitter for splitting an input beam of light into first and second portions comprising:

• an input port for launching the input beam of light;
• an input waveguide including a longitudinal axis, capable of providing adiabatic expansion of the input beam of light from an input end proximate the input port to an output end, which has a width that supports a fundamental mode and a second order mode;
• first and second output waveguides extending from the output end of the input waveguide on either side of the longitudinal axis, and separated by a gap;
• and
• first and second output ports for outputting the first and second portions, respectively;
• wherein each of the first and second output waveguides includes:
• an initial section, including an initial width smaller than the input end of the input waveguide, whereby the initial sections and the gap form a single waveguide capable of supporting a super mode of the input beam of light, which spans the initial sections of the first and second output waveguides and the gap;
• a mode splitting section extending from the initial section at an acute angle to the longitudinal axis for splitting the super mode of the input beam of light into first and second portions;
• and
• a final expansion section extending from the mode splitting section, at least one of the final expansion sections including an expanding width expanding to a same width as the input end of the input waveguide.