Bend loss of step‐index slab waveguides with a trench section

An optical waveguide bend with a trench section whose refractive index is smaller than that in the cladding is investigated to reduce bend loss. The appropriate location and width of the trench are determined using the beam propagation method. It is found that the attenuation constant shows a minimum value when the trench is made around the radiation point where the field becomes radiative.