Experimental studies of the multimode spectral emission in quantum dot lasers

We investigate the electroluminescence spectra of edge-emitting lasers havi ng self-assembled quantum dots as the active medium. A broad laser emission is observed with a modulation of intensity corresponding to single or bunc hes (supermodes) of Fabry-Perot modes. The variation of the laser spectra w ith magnetic field shows that the supermodes originate from laser cavity ef fects and are not related directly to the electronic properties of the quan tum dots. Measurements taken on devices of different cavity height, length, and lateral width indicate that the important parameter controlling the la ser multimode emission is the cavity height, effectively the substrate thic kness. In particular, the period of the supermodes is inversely proportiona l to this thickness, indicating that the modulation of the laser emission i ntensity is due to the leakage of modes into the transparent substrate. (C) 2000 American Institute of Physics. [S0021-8979(00)00204-8].