Based on nine up-to-date types of semiconductor-optical-amplifier (SOA) samples, we devised a power-consumption model of SOA-based all-optical gates as a tool to develop faster and more efficient OTDM systems for bitrates from 10 to 160 Gb/s and those over 160 Gb/s. The conventional effect of a continuous wave (cw) holding beam was included in the model. Furthermore, in this work we defined three step-wise quantum conversion efficiencies eta(1), eta(2), and eta(3) from current-injected carriers through photons. The dependence of each of the three efficiencies on the SOA-structure was studied. The total efficiency eta(T) observed for the nine SOAs ranged widely from 0.07 to 0.46. The validity of the power-consumption model was verified by systematically measuring the effective carrier recovery rate. According to our model, the power consumption of the best existing SOA-based gate for 160-Gb/s signals is 750 mW, and this increases at a rate approximately proportional to (bitrate)(2), and decreases proportionally to (1/etaT)(2).

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We have directly measured, under operating conditions, the distributions of carrier densities and temperatures in a gain-clamped semiconductor optical amplifier designed for operation at 1.55 μm. As expected, longitudinal spatial hole burning is much smaller than in conventional semiconductor optical amplifiers and the effects of gain clamping are clearly evidenced. The amplifier nevertheless shows a sizeable temperature increase for both the lattice and the carriers at high currents, which are attributed to contributions of Auger recombination, intervalence band absorption, and Joule and recombination heating.

Two photon absorption accompanied by a 25-ps-delayed nonlinear response was observed in nonlinear photonic crystal/quantum dot waveguides. Criterion for preventing such a delay time is studied for applications in ultrafast all-optical gates.