Abstract: A photonic coupler including a substrate, first and second waveguides disposed along a longitudinal direction of the substrate for propagation of respective first and second optical signals along the longitudinal direction, and a coupling region between the first and second waveguides and including a medium of a refractive index different from the first and second waveguides. The coupling region has a width extending from the first waveguide to the second waveguide and a breadth extending laterally to form an angle to the longitudinal direction for frustrated total internal reflection of the first optical signal at an interface between the coupling region and the first waveguide.