Optical mode loss and gain of multiple-layer quantum-dot lasers

Using an electrically pumped multisection technique, we have directly measu red the internal optical mode loss of semiconductor-laser structures contai ning 1, 3, 5, and 7 layers of uncoupled InGaAs quantum dots. The optical lo ss does not increase with the number of dot layers so higher net modal gain can be achieved by using multiple layers. The maximum modal gain obtained from the ground state increases with dot layer number from 10 +/-4 cm(-1) f or a single layer to 49 +/-4 cm(-1) for the 7 layer sample, which is typica l of the threshold gain requirement of a 350 mum long device with uncoated facets. (C) 2001 American Institute of Physics.