Coupling waveguide structure design and optimization of optical directional full couplers weighted by hamming function

The coupling waveguide structure design and optimization of optical directional full couplers ( ODFCs) based on hamming weightings is investigated. The validity of approximation theory of optical directional full couplers becomes questionable when the coupling length is not enough long so the beam propagation method ( BMP) is used. We propose a new design and numerically show that some optical properties of the optimized one are better than the optimized coupler with hamming function weighting. The objective of the work includes two parts : the fist part defines theory ranges and processing tolerance of optical directional full couplers. The second part is optimization waveguide structure of optical directional full couplers for low crosstalk, broad bandwidth and short coupler length. Definitely is hamming function ( HF) weighting which proposed can obtain a better result after the structural design.