Broadband optical waveguide couplers with arbitrary coupling ratios designed using a genetic algorithm.

In this work, we present a generalized design of broadband optical waveguide couplers with arbitrary coupling ratios on the silicon-on-insulator platform. The device is segmented into 34 short sections, where the propagation constant and the coupling coefficient of each section are viewed as variables during the optimization process. The optimal variable combination is determined by a genetic algorithm. We can achieve a performance superior to that of other design methods with fewer degrees of freedom. For 75%/25%, 50%/50%, 25%/75%, and 0%/100% couplers, the device lengths are 34 μm and the ±2% bandwidths are all in excess of 100 nm at the central wavelength of 1580 nm.