Study of four-wave mixing in semiconductor optical amplifiers

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This study was started as the International Scientific Research: Joint Research and shifted to the Grant-in Aid for Scientific Research (B) because of the category change. Professor G; Guekos's research group of ETH and Professor H. Kawaguchi's research group of Yamagata University carried out this joint research with closed relation including mutual exchange young researchers.We have investigated mainly the following four topics to create new optical nonlinear functions based on four-wave mixing in semiconductor optical amplifiers (SOAs).(1) SOAs with multiple quantum well active layers corresponding to different band gaps are suitable for amplification of short optical pulses because of their wide gain spectrum. Uniformity of gain saturation in wide spectrum and ultra fast gain dynamics are important issues which should be investigated. We have measured the gain dynamics of such SOA by using the pump-probe method. The gain bandwidth is 100 nm. We found that the wavelength dependence … More of gain saturation characteristics is low. The saturation tendency is the same as SOAs with bulk active layers in which the larger saturation output is obtained at longer wavelength.(2) We analyzed numerically all-optical demultiplexing characteristics based on four-wave mixing (FWM) in SOAs by the finite-difference beam propagation method. We have obtained an optimum input pump pulsewidth. We have also analyzed all-optical demultiplexing characteristics for multichannel probe signals.(3) We precisely measured the deformation in the waveforms of optical pulses which propagated in a SOA using the cross-correlation technique. We found that the output pulse became asymmetric such that its leading edge was sharp compared with the trailing edge. The experimental results well agreed with the simulations by the beam propagation method.(4) We generated short optical pulses from a hybrid modelocked laser diode. The optical pulses were compressed to 450 fs pulse width (auto-correlation width) using an optical fiber with zero dispersion at 1.3 μm. Less