NWs dispersed on SiO 2 generally exhibit much weaker luminescence (up to 10-3 times)

Optically bright lead halide perovskite nanocrystals of different morphologies ranging from nanocubes to flat nanoplatelets to elongated nanowires have been reported. The morphology of the nanocrystals is expected to affect various properties such as the band edge energy and the electron–hole exchange interaction. However, aside from nanocubes, the investigation of optical properties in the lead halide perovskite nanocrystals of different morphologies at the single emitter level has been lacking. We have performed optical spectroscopy in single CsPbBr3 nanoplatelets and observed single photon emission without blinking. Furthermore, the photoluminescence emission exhibits excitonic fine structure peaks similar to what has been previously observed in nanocubes. Our work stimulates further investigations into the excitonic and quantum optics properties when the lateral size and morphology can be further controlled in lead halide perovskite nanocrystals.

Quantum dots enable strong carrier confinement and exhibit a delta-function like density of states, offering significant improvements to laser performance and high-temperature stability when used as a gain medium. However, quantum dot lasers have been limited to photonic cavities that are diffraction-limited and further miniaturization to meet the demands of nanophotonic-electronic integration applications is challenging based on existing designs. Here we introduce the first quantum dot-based plasmonic laser to reduce the cross-sectional area of nanowire quantum dot lasers below the cutoff limit of photonic modes while maintaining the length in the order of the lasing wavelength. Metal organic chemical vapor deposition grown GaAs-AlGaAs core-shell nanowires containing InGaAs quantum dot stacks are placed directly on a silver film, and lasing was observed from single nanowires originating from the InGaAs quantum dot emission into the low-loss higher order plasmonic mode. Lasing threshold pump fluences as low as ∼120 μJ/cm(2) was observed at 7 K, and lasing was observed up to 125 K. Temperature stability from the quantum dot gain, leading to a high characteristic temperature was demonstrated. These results indicate that high-performance, miniaturized quantum dot lasers can be realized with plasmonics.

All-inorganic metal halides perovskites (CsPbX3, X = Br or Cl) show strong excitonic and spin-orbital coupling effects, underpinning spin-selective excitonic transitions and therefore exhibiting great promise for spintronics and quantum-optics applications. Here we report spin-dependent optical nonlinearities in CsPbX3 single crystals by using ultrafast pump-probe spectroscopy. Many-body interactions between spin-polarized excitons act like a pseudo-magnetic field and thus lift the degeneracy of spin states resulting in a photoinduced circular dichroism. Such spontaneous spin splitting between “spin-up” and “spin-down” excitons can be several tens of milli-electron volts under intense excitations. The exciton spin relaxation time is ~20 picoseconds at very low pump fluence, the longest reported in the metal halides perovskites family at room temperature. The dominant spin-flip mechanism is attributed to the electron-hole exchange interactions. Our results provide essential understandings towards realizing practical spintronics applications of perovskite semiconductors.

Optically active perovskite nanocrystals have shown considerable promise for a myriad of applications, such as single photon source, light-emitting diodes and nanophotonics. Coupling those nanocrystals to photonic micro-and nanostructures will offer additional degrees of freedom to manipulate their optical properties. Herein, we demonstrate the coupling of perovskite nanocrystals to a mechanically robust, poly(methyl-methacrylate) (PMMA)-encapsulated silicon nitride nanobeam photonic crystal cavity at room temperature. As determined from the time-resolved photoluminescence decay measurements, we observed enhanced spontaneous emission from the perovskite nanocrystals by a factor of 1.4, consistent with finite difference time domain simulation. In addition, by varying the concentration of the perovskite nanocrystal in the PMMA layer, the effective index of the layer can be modified, allowing us to tune the cavity mode resonance. Our results show that solution-processable perovskite nanocrystals hold a promising prospect for applications such as on-chip light sources, optoelectronic devices and photonic integrated circuits.