Recently, Prof. Qing Zhang’s research group from the College of Engineering, Peking University, made new progresses on the exciton polariton (EP) and continuous-wave (CW) pumped green halide perovskite semiconductor microlaser. Related works have been published online in Nano Letters (Nano Lett. 2020, 20, 1023−1032; Nano Lett. DOI: 10.1021/acs.nanolett.0c02462).
With the rapid development of 5G wireless communication, on-chip optical interconnection, and consumer electronics, the demands for miniaturized and low energy-consumption lasers are extensively increased. However, the high defect density of gain materials, limited gain volume, and local heating effect restrict the realization of current-driven micro/nano-lasers. EP lasing, accomplished free from the population inversion, provides a solution for this goal. Metal halide perovskite semiconductors have emerged as great candidates for EP devices for their stable excitons at room temperature because of the large binding energies.
Fig. a. left: schematic diagram of EP propagating in one-dimensional CsPbBr3 nanowire; right: distal PL spectrum measured by spatial-resolved photoluminescence spectroscopy and corresponding dispersion curve of EP. b. CW pumped microlaser in CsPbBr3 nanoribbon-sapphire configuration.
Zhang's group demonstrates that light propagates as EPs in CsPbBr3 nanowires near exciton resonance at room temperature. The occurrence of EPs enhances the group refractive index (ng) by three times and optical absorption coefficient by five times compared with bulk counterparts (Nano Lett. 2020, 20, 1023−1032). With the decrease of temperature, the group index increases and reaches 43.7 at 78 K; this significantly increases the mode confinement factor, reduces the optical losses, and thus lowers the lasing threshold. They realized CW pumped green microlasers by using ultrathin CsPbBr3 nanoribbons on sapphire substrate. The threshold is as low as 0.13 kW cm-2 and 2.6 kW cm-2 at 7.8 K and 78 K, respectively (Nano Lett. DOI: 10.1021/acs.nanolett.0c02462). These works elucidate the light propagating behaviors and laser mechanisms in one-dimensional CsPbBr3, which provides new insights for the realization of electrically pumped lasers.
These works were supported by the Natural Science Foundation of China and the Ministry of Science and Technology.