A review is given on the recent progress in the epitaxy of 1.55 µm QD/QDash laser material and its application in lasers and semiconductor optical amplifiers. By choosing different growth modes by using either As4 or As2, the shape of InAs islands grown on AlGaInAs surfaces can be strongly influenced from dash-like to dot-like geometries. This shape change is accompanied by a strong reduction of the size fluctuation, which increases significantly the modal gain of lasers. This has a large impact on the response time of lasers allowing record values of the modulation speed of InP based QD lasers of 15 GBit/s. On the other hand dash-like structures allow ultra-high speed responses in optical amplifiers due to their local relaxation but remaining coupling to continuum states. By two-photon absorption phenomena instantaneous gain can be obtained on the sub-ps time scale.