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Studies the nonlinear gain dynamics in semiconductor quantum-dot (QD) optical amplifiers and their application to optical communication devices. Evaluation of optical nonlinearity in QD using four-wave-mixing methods and nonlinear pulse transmission measurements; Spontaneous emission spectra of QD optical amplifier.

Wavelength conversion using nondegenerate four-wave mixing in quantum-dot optical amplifiers is investigated. From the detuning frequency dependence of χ[sup (3)], derived from the conversion efficiency, we consider that, within the range of detuning in the experiment, spectral-hole burning and carrier heating are responsible, and that their time constants, i.e., carrier relaxation time to the ground state and the phonon scattering time, are in the range of 60-140 and 200-400 fs, respectively. This indicates that the carrier supply to the ground level via relaxation from the higher levels is very fast and that a broad conversion bandwidth comparable to that of quantum-well devices is ensured. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]