Optically pumped lasing in a rolled-up dot-in-a-well (DWELL) microtube via the support of Au pad

We report the observation of optically pumped continuous wave lasing in a self-rolled-up InGaAs/GaAs quantum dot microtube at room temperature. Single layer of InAs quantum dots (~ 2.6 ML coverage) in a GaAs well sandwiched by two AlGaAs barriers are incorporated into the tube wall as the gain media. As-fabricated microtube is supported by a 300-nm-thick Au pad, aiming to separate the tube from GaAs substrate and thus to decrease the substrate loss, which finally enables lasing with ultralow threshold power (~ 4 µW) from an microtube ring resonator.