Optical 1 × 3 power dividers composed of coupled waveguides are analyzed using the implicit finite‐difference method and the low‐loss configuration with reduced size is investigated. First, to check the accuracy of the method, the mismatching loss of the eigenmode of a straight waveguide is evaluated and it is verified that the error does not accumulate with the propagation distance.
Next, the characteristics of 1 × 3 power dividers using coupled waveguides inclined with respect to each other are investigated and the range of the tilt angle and the effects of the angular error upon power distribution are clarified. To widen the tilt angle, which results in reduced‐size dividers, the corner bends with modified refractive‐index distribution are introduced. As a result, the loss of a 3‐degree tilt angle divider is found to be reduced by more than 1.5 dB due to the introduction of the corner bend with modified refractive‐index distribution.