Le Journal de Physique IV 03 (1993) C5-31-C5-38
Optical amplification and its saturation in semiconductor quantum wellsJ. BUTTY1, G. BONGIOVANNI2 and J.L. STAEHLI1
1 Institut de Physique Appliquée, Ecole Polytechnique Fédérale, PH-Ecublens, 1015 Lausanne, Switzerland
2 Dipartimento di Scienze Fisiche, Università degli Studi di Cagliari, via Ospedale 72, 09124 Cagliari, Italy
We present an investigation of the optical gain and its saturation of the electronhole plasma confined in GaAs/(Ga,Al)As quantum wells. For such investigations the variable stripe length method is a simple but quite powerful tool. The spacial longitudinal variation of luminous and electron-hole pair densities in narrow stripes of various lengths has been investigated theoretically and experimentally. For this also the spectra of spontaneous luminescence (emitted in a direction perpendicular to the stripe) have been recorded at different places on the stripe. The experimental results are compared with the predictions of a theoretical model of the optical quantum well amplifier. We find that saturation is caused by carrier depopulation through stimulated electron-hole recombination, and by the loss of light travelling in the direction of the stripe due to scattering and/or reabsorption. However, we do not find evidence of intra band saturation, ie. of a non thermal electron or hole distribution.
© EDP Sciences 1993