Abstract
We propose a new method to design 3-branch optical power dividers. According to the scalar Helmholtz equation, if a complex field distribution is given, then one corresponding refractive index distribution is determined uniquely. On the basis of this relationship, we first make up an ideal field which ensures smooth power division in the branching region, and next derive the refractive index distribution from this ideal field. Since the derived refractive index distribution has non-zero imaginary part and a complicated profile, it is almost impossible to fabricate the index distribution as derived. We discretize the real part into several levels and set imaginary part zero from a practical point of view. Three-branch waveguides designed by this procedure accomplish very low loss and equal division.
