Realization of ultrafast all-optical switching with switching gain in a single semiconductor waveguide.

In this Letter, we report for the first time to our knowledge that all-optical switching gain can be achieved with a dual-wavelength control versus pump beam scheme in a single semiconductor waveguide structure. That means a weak optical beam can switch a strong optical beam. Moreover, a high switching speed of 10-100  Gb/s can be achieved. The all-optical switching is simulated numerically via a multilevel multielectron (MLME) FDTD program capable of modeling complex semiconductor band properties. It is shown that a weak control/input-signal beam at a longer wavelength is able to switch the transmission of a strong pump/output-signal beam at a shorter wavelength. A 50 Gbps and 0.5 pJ per bit switching operation with switching gain of around 10 is shown for a 40 μm-long waveguide with pump beam power around 20 mW based on bulk InGaAsP material and a 300  nm×300  nm waveguide (the control beam power is 1/10 of that for the pump).