Wavelength dependent ultrafast gain and phase dynamics in bulk SOAs over wide gain region

Based on the semiclassical density-matrix equations, ultrafast probe gain and phase dynamics in bulk semiconductor optical amplifiers excited by a 200 fs Gaussian pump pulse centered at 1,558 nm are numerically investigated and compared over a wide material gain region (1,460–1,650 nm). It is predicted that the recovery time of phase may be longer or shorter than that of gain depending on probe wavelengths. Besides, as functions of probe wavelength, the dynamic gain range and the dynamic phase range have different shapes. Moreover, the wavelength dependence of phase recovery overshoot is illustrated. At last, the probe chirp dynamics and the wavelength dependence of the chirp characteristics are described. These interesting features result from a restriction of the Kramers–Kronig relations and different ways of the competition or cooperation among the effects of spectral-hole burning, carrier heating and two-photon absorption on subpicosecond timescale over the whole concerned band.