Carrier heating and spectral hole burning in strained-layer quantum-well laser amplifiers at 1.5 μm

We present the first polarization studies of femtosecond gain dynamics in strained-layer multiple-quantum-well laser amplifiers. We observe a response consistent with spectral hole burning when the diode is biased in the absorbing regime. In the gain regime, we show that the carriers are heated by free-carrier absorption and that there is a measurable delay (∼200 fs) in the thermalization of the hot-carrier distribution. Subsequent cooling to the lattice temperature follows with a time constant of ∼1 ps.