Ultrafast all-optical wavelength and polarization independent demultiplexer

Abstract

Recent developments in all-optical switching devices based on the interferometric principle are very promising for optical communication systems, especially those based on optical time division multiplexing system (OTDM), where a user is allowed to transmit or receive a data in a assigned time slot within a given time frame. One such device based on a Sagnac interferometer is called a Terahertz Optical Asymmetric Demultiplexer (the TOAD). Another device based on a Mach-Zehnder interferometer is a Symmetric Mach-Zehnder (SMZ). Both devices utilize large optical nonlinearities in the resonance regime of the semiconductor, therefore it is possible to operate these devices with a very small optical control pulse energy. The currently demonstrated TOAD can be switched with 0.8 pJ, and the SMZ with 11 pJ. We still can reduce the control pulse energy by optimizing and employing other nonlinear optical materials. The most critical problem associated with a slow recovery time of the resonance nonlinearities has been solved by a special geometrical location of a nonlinear optical element in the Sagnac interferometer, and two control pulses to do independent on and off switching operation for the Mach-Zehnder. We demonstrated a 10 ps switching window by counter-propagating the control and data pulses in the Mach-Zehnder interferometer using 0.65 pJ of control pulse energy. This device is advantageous in its superior rejection capability of the control signal. In terms of the possibility of integration, this device is expected to be a much simpler design than the previously demonstrated systems. Also the utilized optical nonlinear elements are semiconductor optical amplifiers, the data signal can be larger than the input. This may facilitate cascadability and fan-out capability.