;In the era of information explosion, optical communication is desired to replace electronic transmission because of the increase of the data-carrying capacity nowadays; however, it is not mature enough. And therefore researches, which are related with optical transmission and optical signal modulation devices, such as directional couplers, would give great support in the future.
The function of the optical directional coupler is not only the switch, the selective device of frequency and polarization, but also the amplitude divider. Moreover, the directional coupler, which is based on electro-optic (EO) crystal, can achieve a fast modulator by modulating the applied voltage.
In this study, the electro-optically switched directional couplers in APPLN (aperiodically poled lithium niobate) were designed by the AOS (aperiodic optical superlattice) technique with the aid of the simulated annealing (SA) optimization method. The split ratio based on the design can be manipulated by applying voltage along the crystal z axis and performances, which are compared with the periodical designs in the previous literatures, can be even improved.
The optimized APPLN structures can increase the tolerance for fabrication and working voltage, which allows the possibility of output performances being more flexible. Based on this advantage, we could further apply designs to practical applications, such as voltage circuit breaker, 1 × 4 signal router, integrated light source, and logic gates (NAND, AND, XOR, XNOR, NOR, OR). In the future, we expect to realize the optimized device to be a highly competitive device.