ROLE OF PLASMA COOLING, HEATING, AND MEMORY EFFECTS IN SUBPICOSECOND PULSE-PROPAGATION IN SEMICONDUCTOR AMPLIFIERS

Based on a microscopic theory of a two-band semiconductor light amplif ier, we show that plasma heating, cooling, and ultrafast memory effect s all act in concert to produce strong distortion of subpicosecond pul ses propagating in semiconductor amplifiers. Plasma heating, spectral hole burning, and carrier density depletion are responsible for satura tion of the gain seen by a propagating intense femtosecond pulse in th e amplifier. Plasma cooling replenishes the carrier population on the trailing edge of the pulse, leading to pulse broadening as a consequen ce of gain regeneration. The inclusion of memory effects in the descri ption of dephasing processes goes beyond the usual Markov assumption o f constant dephasing rates; it significantly affects the dynamical pul se reshaping processes.