Extremely fast, high-gain and low-current semiconductor optical amplifier by optical speed-up at transparency

Summary form only given. High-speed semiconductor optical amplifiers (SOAs) are required in many devices for all-optical processing in WDM networks. They can be used as linear devices (optical gates for optical switching for example) or they can be required for their nonlinear properties (to realize complex functions like wavelength conversion). The extremely fast gain recovering in SOAs is required for high-bit-rate applications in future optical systems. The gain recovery time can be only moderately reduced by increasing the conventional SOA length but this also reduces the optical gain bandwidth. The SOA setup proposed in the present paper, called OSAT (optical speed-up at transparency), uses an assist light beam injected at the transparency point of the SOA, which gives rise to higher possible gain and higher speed at a much lower injection current while eliminating relaxation oscillations and dark holes. The principle of the OSAT is based on the carrier dependency of the material gain transparency. We have demonstrated that a number of features makes it very attractive for all-optical processing in WDM networks.