Progress in semiconductor quantum dots-based continuous-wave laser

Continuous-wave (CW) operated laser is a key component for photonic chips. It has been highly desired to develop low-threshold, high-efficiency, long-term operational, low-cost and easily integratable CW laser. As excellent optical gain materials, quantum dots (QDs) have been intensively investigated for on-chip CW lasers owing to their high photoluminescence quantum yields, tunable emission wavelengths and easy integration. Base on the difference of preparation processes, QDs can be classified into epitaxial QDs and solution- processed colloidal QDs (CQDs). In this mini-review, we summarize the research progresses of epitaxial III-V semiconductor QD and solution-processed CQD-based CW lasers. The challenges associated with the realization of CQD CW lasers are discussed in detail. In particular, the emerging perovskite-based CW lasers are highlighted. Finally, a short perspective of QD-based CW lasers is presented.