High Speed 1225 and 1250 nm VCSELs Based on Low-Temperature Grown Quantum Dots

So far, long wavelength Stranski-Krastanow (SK) quantum dots (QDs) have been failed to provide enough differential gain and temperature stability, required for high speed VCSEL -the fastest modulation bandwidth of a SK QD-VCSEL is only 3 GHz. In contrast, InGaAs quantum dots, grown at low temperatures of ~400 degC (LTQDs), demonstrate the possibility to reach simultaneously long wavelengths and a high QD density with an exciton-like recombination mechanism. LTQDs allow a high modal gain, avoid temperature depletion and gain saturation effects. Thus they are suitable for high-speed vertical-cavity surface-emitting lasers (VCSELs).