Room‐temperature lasing operation of a quantum‐dot vertical‐cavity surface‐emitting laser

Self‐assembled growth of quantum dots by molecular‐beam epitaxy is used to form the active region of a vertical‐cavity surface‐emitting laser (VCSEL). Ten layers of InGaAs quantum dots are stacked in order to increase the gain. This quantum‐dot VCSEL has a continuous‐wave operating current of 32 mA at room temperature. Emission spectra at various current injections demonstrate that the lasing action is associated with a higher‐order transition in the quantum dots.