WITHDRAWN: All-optical switching using a new photonic crystal directional coupler

Abstract

In this paper all-optical switching in a new proposed photonic crystal directional coupler is performed and analyzed. The structure of the switch consists of a directional coupler and a separate path for a control signal called “control waveguide”. In contrast to the former reported structures in which the directional couplers are made by removing a row of rods entirely, the directional coupler in our optical switch is constructed by two reduced-radius line-defect waveguides separated by the control waveguide. Furthermore, in our structure the background material has the nonlinear Kerr property. Therefore, in this switch, no frequency overlap occurs between the control waveguide mode and the directional coupler modes. It is shown that such a condition provides a very good isolation between the control and the probe signals at the output ports. In the control waveguide, nonlinear Kerr effect provides the required refractive index change by the presence of a high power control (pump) signal. Even and odd modes of the coupler are investigated by applying the distribution of the refractive index change in the nonlinear region of a super-cell. Finally, all-optical switching of the 1.55 μm probe signal using a control signal at the wavelength of 1.3 μm, is simulated using the finite-difference time-domain method, where both signals are desirable in optical communication systems. A very high extinction ratio of 67 dB is achieved and the temporal characteristics of the switch are demonstrated.