The spontaneous and stimulated emissions of strongly excited GaAs/(Ga,Al)As quantum wells are investigated in the one-dimensional optical amplifier geometry, using the variable-stripe-length method. The optical amplification and its saturation are studied by monitoring the spectra of spontaneous and amplified luminescence as a function of the position on the stripe. The deduced experimental spatial dependences of carrier and luminous densities are found to agree in a semiquantitative way with the numerical solutions of the amplifier equation, obtained by assuming steady state and thermal carrier distributions. Saturation of optical amplification is caused by two effects: (1) carrier depopulation through stimulated recombination of electron-hole pairs, and (2) loss of light caused by scattering at sample defects and by imperfect wave guiding.
Jean Louis Staehli,
"Optical amplification and its saturation in semiconductor quantum wells," Optical Engineering 34(7), (1 July 1995). http://dx.doi.org/10.1117/12.200612