Near-infrared (NIR) solid-state micro/nanolasers are important building blocks for true integration of optoelectronic circuitry. Although significant progress has been made in III-V nanowire lasers with achieving NIR lasing at room temperature, challenges remain including low quantum efficiencies and high Auger losses. Importantly, the obstacles toward integrating one-dimensional nanowires on the planar ubiquitous Si platform need to be effectively tackled. Here we demonstrate a new family of planar room-temperature NIR nanolasers based on organic-inorganic perovskite CH3NH3PbI(3-a)X(a) (X = I, Br, Cl) nanoplatelets. Their large exciton binding energies, long diffusion lengths, and naturally formed high-quality planar whispering-gallery mode cavities ensure adequate gain and efficient optical feedback for low-threshold optically pumped in-plane lasing. We show that these remarkable wavelength tunable whispering-gallery nanolasers can be easily integrated onto conductive platforms (Si, Au, indium tin oxide, and so forth). Our findings open up a new class of wavelength tunable planar nanomaterials potentially suitable for on-chip integration.

Semiconductor nanowires have received considerable attention in the past decade driven by both unprecedented physics derived from the quantum size effect and strong isotropy and advanced applications as potential building blocks for nanoscale electronics and optoelectronic devices. Recently, organic-inorganic hybrid perovskites have been shown to exhibit high optical absorption coefficient, optimal direct band gap, and long electron/hole diffusion lengths, leading to high-performance photovoltaic devices. Herein, we present the vapor phase synthesis free-standing CH3NH3PbI3, CH3NH3PbBr3, and CH3NH3PbIxCl3(-x) perovskite nanowires with high crystallinity. These rectangular cross-sectional perovskite nanowires have good optical properties and long electron hole diffusion length, which ensure adequate gain and efficient optical feedback. Indeed, we have demonstrated optical-pumped room-temperature CH3NH3PbI3 nanowire lasers with near-infrared wavelength of 777 nm, low threshold of 11 μJ/cm(2), and a quality factor as high as 405. Our research advocates the promise of optoelectronic devices based on organic-inorganic perovskite nanowires.

High-index dielectric and semiconductor nanoparticles supporting strong electric and magnetic resonances have drawn significant attention in recent years. However, until now, there have been no experimental reports of lasing action from such nanostructures. Here, we demonstrate directional lasing, with a low threshold and high quality factor, in active dielectric nanoantenna arrays achieved through a leaky resonance excited in coupled gallium arsenide (GaAs) nanopillars. The leaky resonance is formed by partially breaking a bound state in the continuum generated by the collective, vertical electric dipole resonances excited in the nanopillars for subdiffractive arrays. We control the directionality of the emitted light while maintaining a high quality factor (Q = 2,750). The lasing directivity and wavelength can be tuned via the nanoantenna array geometry and by modifying the gain spectrum of GaAs with temperature. The obtained results provide guidelines for achieving surface-emitting laser devices based on active dielectric nanoantennas that are compact and highly transparent.

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www.advancedsciencenews.com www.small-methods.com an inorganic or organic cation (Cs + , CH 3 NH 3 + , NH 2 CHNH 2 + , etc.), M is a divalent metallic cation (Pb 2+ , Sn 2+ , Mn 2+ , Fe 2+ , etc.), and X is halogen anion (I − , Br − , Cl − ). [28][29][30] Since 2009, perovskites have gained worldwide attention due to their unprecedented success in photovoltaics. [31][32][33][34][35][36] The power conversion of solution-processed CH 3 NH 3 PbX 3 (MAPbX 3 ) perovskite solar cells has increased from 3.8% to 22.1% within a few years. [37][38][39][40][41][42] Although there is still some debate, it is widely accepted that the high power conversion efficiency of MAPbX 3 is attributed to the high absorption coefficient (≈10 4 cm −1 ), balanced and long diffusion length (≈100 nm to 100 µm), low density of defect states (10 9 -10 10 cm −3 ) and bipolar carrier-transport property. [31,33,34] As a direct-bandgap semiconductor, perovskites also show wide-band tunable emission color and high quantum yield, holding important potential applications in light sources, for example. [40,[43][44][45] Prior to the rapidly developing studies in solar cells, perovskites have been studied as light-emittingdiode (LED) devices for a long time. [46][47][48] In particular, recent studies on photophysical properties, structure engineering, and device development have led to the rapid progress of coherent and incoherent perovskite photonic sources. [44,[49][50][51][52][53][54][55] For example, several groups have demonstrated perovskite LEDs with external quantum efficiency of ≈8-12% using solutionprocessed and thermally evaporated quasi-two-dimensional perovskite thin films, etc. [44,51] Furthermore, perovskite nanostructures including NWs, NPs, and quantum dots (QDs) are also attracting more and more attention for exploring nanophotonic and quantum devices, including single-photon sources, optical detectors, transistors, optical sensors, etc. [56][57][58][59] In a nutshell, despite the Pb toxicity and poor stability, perovskites have been attracting more and more attention in divergent research areas. These fundamental studies on and applications of perovskite photonic sources could extensively push forward our present energy and communication technology.With high absorption coefficient and low density of defects, perovskites are excellent gain materials for the development of high-performance lasing devices. More interestingly, thanks to the long-distance ambipolar carrier-transport properties, perovskites could greatly raise the possibility of realizing electrically driven microlasers and nanolasers. In 2014, Xing et al. demonstrated the first amplification of spontaneous emission (ASE) of CH 3 NH 3 PbX 3 perovskite thin film, which had been solution processed at low temperature. [60] Through embedding CH 3 NH 3 PbI 3−x Cl x perovskite thin films into a distributed Bragg reflector Fabry-Pérot (F-P) cavity, Deschler et al. demonstrated room-temperature perovskite lasing. [49] Beyond these thin films, perovskite nanostructures including NP...

Solid-state room-temperature lasing with tunability in a wide range of wavelengths is desirable for many applications. To achieve this, besides an efficient gain material with a tunable emission wavelength, a high quality-factor optical cavity is essential. Here, we combine a film of colloidal CdSe/CdZnS core−shell nanoplatelets with square arrays of nanocylinders made of titanium dioxide to achieve optically pumped lasing at visible wavelengths and room temperature. The all-dielectric arrays support bound states in the continuum (BICs), which result from lattice-mediated Mie resonances and boast infinite quality factors in theory. In particular, we demonstrate lasing from a BIC that originates from out-of-plane magnetic dipoles oscillating in phase. By adjusting the diameter of the cylinders, we tune the lasing wavelength across the gain bandwidth of the nanoplatelets. The spectral tunability of both the cavity resonance and nanoplatelet gain, together with efficient light confinement in BICs, promises low-threshold lasing with wide selectivity in wavelengths.

Resonant metasurfaces are an attractive platform for enhancing the non-linear optical processes, such as second harmonic generation (SHG), since they can generate very large local electromagnetic fields while relaxing the phase-matching requirements. Here, we take this platform a step closer to the practical applications by demonstrating visible range, continuous wave (CW) SHG. We do so by combining the attractive material properties of gallium phosphide with engineered, high quality-factor photonic modes enabled by bound states in the continuum. For the optimum case, we obtain efficiencies around 5e-5 % W −1 when the system is pumped at 1200 nm wavelength

In the growing list of 2D semiconductors as potential successors to silicon in future devices, metal-halide perovskites have recently joined the family. Unlike other conversional 2D covalent semiconductors such as graphene, transition metal dichalcogenides, black phosphorus, etc., 2D perovskites are ionic materials, affording many distinct properties of their own, including high photoluminescence quantum efficiency, balanced large exciton binding energy and oscillator strength, and long carrier diffusion length. These unique properties make 2D perovskites potential candidates for optoelectronic and photonic devices such as solar cells, light-emitting diodes, photodetectors, nanolasers, waveguides, modulators, and so on, which represent a relatively new but exciting and rapidly expanding area of research. In this Review, the recent advances in emerging 2D metal-halide perovskites and their applications in the fields of optoelectronics and photonics are summarized and insights into the future direction of these fields are offered.