Perovskite-quantum-dot plasmonic nanolasers
with ultralow thresholds

Yu-Jung Lu

To date, the size of conventional lasers, which is usually larger than half of their wavelength due to the diffraction limit, hinders their applications in on-chip integration and ultracompact optoelectronic devices. The miniaturization of optoelectronic components has gradually become an important research topic, especially for nanolasers. How can the size of lasers be reduced? How can the power consumption of laser operations be reduced? How can a laser with a new working mechanism be developed to overcome the diffraction limit? These questions have become the key challenges for nanolaser research. Recently, Prof. Yu-Jung Lu, an assistant research fellow at the Research Center for Applied Sciences at Academia Sinica, and her collaborative research teams have published an article on continuous-wave nanolasing from an inorganic lead-halide perovskite (CsPbBr₃) quantum dot in a gap-plasmon nanocavity with an ultralow threshold at 120 K. This research provides an approach for realizing on-chip electrically driven lasing and integration into plasmonic circuitry for information processing. This work was published in ACS Nano as a selected cover issue in 2020.

The nanocavity is designed as a sandwich structure in which a single highly emissive perovskite quantum dot is located between a silver nanocube and a gold substrate, as shown in Fig. 2a. A thin layer of Al₂O₃ was deposited between the perovskite quantum dot and the gold substrate to avoid PL quenching. This was the first continuous wave operation of a perovskite nanolaser at a wavelength of 534 nm with an ultralow lasing threshold of 1.9 W cm^-2 at 120 K (see Fig. 2b, d), and it had a temporal coherence feature for measuring the second-order correlation function (see Fig. 2f). More significantly, it set a state-of-the-art record for the ultrasmall localized mode volume (~0.002 λ³), which was two orders of magnitude smaller than the optical diffraction limit.

Fig. 2: a-e Schematic, lasing signatures, and the lasing mechanism of a single perovskite quantum dot (PQD) in a gap plasmon nanocavity at 120 K. f The temporal coherence signature of the PQD nanolasing under 120 K was determined