Robust single-mode lasers based on hexagonal CdS microflakes

Single-mode micro/nanolasers have been of considerable interest for their potential applications in optical communication and high-resolution spectroscopy. However, constrained by large radiation loss and insufficient gain in microcavities, realizing high-performance single-mode micro/nanolasers is still challenging. In this work, single-mode whispering-gallery-mode lasing is demonstrated from single-crystal CdS microflakes with a sharp linewidth (∼0.12 nm) and a high quality factor (Q ∼ 4200) at room temperature. Such lasers are superior to previous CdS lasers in these lasing parameters. Through time-resolved photoluminescence measurements, electron–hole plasma recombination is established to be the lasing mechanism. The radiative recombination rate of CdS microflakes is enhanced by a factor of ∼4.7 due to the Purcell effect. These CdS microflake single-mode lasers can be potentially useful in optoelectronic devices.