Ultraviolet nanolaser of inverted hexagonal ZnO pyramid resonating in helical whispering-gallery-like mode.

ZnO nanocavities have advantage to working as optoelectrical nanodevices integrated on chip at high temperature owing to high exciton binding energy. In this work, a single inverted hexagonal ZnO pyramid (HZOP) nanolaser is fabricated successfully by reducing the defect with chemical vapor deposition (CVD). The optical leakage of HZOP is conquered by the inverted configuration to increase the refractive index contrast between ZnO pyramid and surrounding media. Helical whispering-gallery-like mode is proposed to dominate the lasing of HZOP nanolaser. All of the lasing peaks are found to exist at wavelength longer to the fluorescence emission of ZnO, which is ascribed to the large loss represented by the large imaginary part of ZnO refractive index at shorter wavelength. The threshold and linewidth are measured to be 5.27 mJ/cm2 and 0.27 nm, respectively. HZOP nanolaser is a new ultraviolet coherent light source to be integrated on chip at room temperature or higher temperature.

The Dissociation of Exciton During the Lasing of a Single CsPbBr3 Microplate.

In this work, the lasing of a single CsPbBr3 microplate (MP) fabricated with chemical vapor deposition (CVD) is investigated from the viewpoint of exciton dissociation characterized with steady-state photoluminescence (PL) and time-resolved photoluminescence (TRPL). It is confirmed that the lasing performance is disturbed by the dissociation of excitons. The increase of lasing threshold with temperature originates from the dissociation of free excitons (FEs) to localized carriers (LCs), and the lasing failure is mostly ascribed to the dissociation of FEs to free carriers (FCs). The working temperature of micro/nanolasers based on metal halide perovskites (MHPs) could be raised up to the temperature determined by exciton binding energy while the laser heating effect is dealt with well. These findings advance our understanding on the photophysics of the lasing behaviors of micro/nanocavities based on MHPs and help us promote their performance by having better thermal management.

Temperature-Dependent Lasing of CsPbI3 Triangular Pyramid.

In this work, the lasing performance of a microsized single-crystal CsPbI3 triangular pyramid (MSCTP) is evaluated by measuring the lasing threshold at low temperature. The MSCTPs of well-defined facets are synthesized on a Si/SiO2 substrate with chemical vapor deposition. The MSCTP shows a spontaneous emission around 719 nm at room temperature and a stimulated emission resonant in a single Fabry-Perot mode within 148-223 K. The lasing threshold varies from 21.56 to 53.15 µJ/cm2 and presents a temperature dependence in an empirical exponential function with a characteristic temperature of 72.73 K. The temperature dependence of lasing behavior is ascribed to the competition between the exciton binding energy and thermal disturbance energy of CsPbI3. The results of this work provide us a perspective to engineer and optimize optoelectrical devices based on perovskite materials and a microsized optical cavity to investigate the light-matter interaction in quantum optics.