Investigation and simulation of photonic crystal directional coupler switch

The photonic crystal optical switch is one of the most important applications of photonic crystals in telecommunication networks. Switching is a main process in digital computers and signal processing systems. The growth of optical signal processing systems draws particular attention to the design of ultra-fast optical switches. In this reported work, first a directional coupler switch based on photonic crystals is designed and the linear state has been analysed and simulated. Then, the principles of nonlinear optics are used to perform optical switching at a wavelength of 1550 nm by COMSOL Multiphysics in micron dimension. The dielectric rods of this photonic crystal lattice are made of AlGaAs. The central row is an important factor for attaining the required power in nonlinear switching performance. Finally, the radius of rods in the central nonlinear row is changed several times and the results are compared with each other. In this switch, the output power ratio, called the extinction ratio, and the required refractive index change for the nonlinear status are taken into account. The former is for the evaluation of directional coupler efficiency and the latter is generally an important factor in optical nonlinear switches.