Coherent optical generation of nonequilibrium electrons studied via band-to-acceptor luminescence in GaAs

Nonequilibrium electrons generated by coherent optical excitation of GaAs are studied in a wide range of carrier density. The electron distribution is monitored via spectrally resolved band-to-acceptor luminescence after continuous-wave, picosecond, or femtosecond laser excitation. Our data demonstrate that the coherent coupling between the laser radiation and the interband polarization and its dephasing strongly influence the initial carrier distribution. The energetic width of carrier generation is broadened due to rapid phase-breaking scattering events during carrier generation. Theoretical results from a Monte Carlo solution of the semiconductor Bloch equations including on the same kinetic level coherent and incoherent phenomena show that the broadening of the electron distribution is introduced mainly in the generation process whereas the recombination of electrons with bound holes makes a minor contribution. The theoretical results are in quantitative agreement with the experimental data.