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Methylammonium lead bromide perovskite (MAPbBr3)-embedded nano- and micro-fibers are successfully fabricated by using the uniaxial electrospinning technique. Through the study of solidification and coordination between perovskite with hybrid polymers, polymethyl methacrylate, and polyacrylonitrile, the bamboo-like perovskite-embedded polymer nano/microfibers are unpredictably formed. Encapsulated in polymer, the passive perovskite-embedded polymer fibers exhibit a long-term fluorescence performance when simultaneously exposed to both water immersion and short-wavelength laser irradiation. Notably, due to the efficient gain media, the perovskite-rich region of the electrospun fiber can act as an optical microcavity. Multi-mode and single-mode lasing behaviors can be achieved via different cavity lengths. The mechanism of a microlaser within this perovskite fiber is confirmed through a Fabry–Pérot cavity, which provides an opportunity for optical components in lasers.

The surface plasmon effect can be used to confine electromagnetic fields to a small footprint measuring tens of nanometers. The resultant resonant cavities function as optimal coherent light sources with subwavelength scale configurations. The plasmonic laser sources based on nanoshell structures, in particular, have demonstrated the potential for use in the detection of subcellular mesoscopic molecular structures. However, this structure has a high plasmon dephasing rate, which can increase the threshold of the device, making it difficult to achieve electrically excited structures, thereby rendering them unsuitable as an active component for integration into optoelectronic circuits. A different approach to confining electromagnetic fields involves using a propagating surface plasmon laser structured on a planar layered semiconductor–insulator–metal. This design enables the surface plasmon to propagate along the direction of the nanowire and offers the potential to achieve electrically driven structures by injecting current into the semiconductor nanowire. Consequently, this structure is more effective in guiding energy into integrated optoelectronic circuits compared to the isotropic radiation of nanoshell structures. However, this design also necessitates a supporting substrate, resulting in the actual device volume exceeding the nanoscale and, in some cases, even larger than the size of a cell. This limitation hinders the application of integrated optoelectronic circuits at the micro/nanoscale for bio-applications. To address these challenges, we developed a substrate-free surface plasmon polariton laser. We demonstrated that allowing direct contact between the film and the air significantly reduced the laser threshold. Furthermore, the device maintained its operational capability across different surfaces.

This study aims to enhance the optical and thermal properties of cesium-based perovskite nanocrystals (NCs) through surface passivation with organic sulfonate (or sulfonic acid) ligands. Four different phenylated ligands, including sodium β-styrenesulfonate (SbSS), sodium benzenesulfonate (SBS), sodium p-toluenesulfonate (SPTS), and 4-dodecylbenzenesulfonic acid (DBSA), were employed to modify blue-emitting CsPbBr1.5Cl1.5 perovskite NCs, resulting in improved size uniformity and surface functionalization. Transmission electron microscopy and X-ray photoelectron spectroscopy confirmed the successful anchoring of sulfonate or sulfonic acid ligands on the surface of perovskite NCs. Moreover, the photoluminescence quantum yield increased from 32% of the original perovskite NCs to 63% of the SPTS-modified ones due to effective surface passivation. Time-resolved photoluminescence decay measurements revealed extended PL lifetimes for ligand-modified NCs, indicative of reduced nonradiative recombination. Thermal stability studies demonstrated that the SPTS-modified NCs retained nearly 80% of the initial PL intensity when heated at 60 °C for 10 min, surpassing the performance of the original NCs. These findings emphasize the optical and thermal stability enhancement of cesium-based perovskite NCs through surface passivation with suitable sulfonate ligands.

The Rabi-splitting energy represents the strength of light–matter interaction. This quantity is a good benchmark for evaluating the performance of light-modulation devices. Herein, we adopt ZnO microrods as microcavities for whispering gallery modes and propose a convenient method for estimating the light–matter coupling strength based on the shifts of resonant modes in temperature-dependent photoluminescence spectra from 295 to 77 K. Both temperature-dependent index dispersion and Rabi splitting can be extracted. Additionally, the Rabi-splitting energy of bulk ZnO at 0 K is estimated to be about 289 meV.

In this study, we utilized a dielectric Bragg reflector (DBR) as a mirror and positioned a wide-spectrum FAMACsPb(BrI)3 halide perovskite film between two DBRs to construct a vertical-cavity surface-emitting laser (VCSEL) structure. The top and bottom DBRs were connected using optical adhesive, allowing us to control the cavity length by applying external force. Through this approach, we achieved operation at the desired wavelength. Due to the exceptional optical gain provided by FAMACsPb(BrI)3, we successfully observed multimode and lasing phenomena at room temperature under continuous-wave (CW) laser excitation. The outcomes of this study provide valuable insights for the application of novel VCSEL structures and highlight the potential of using FAMACsPb(BrI)3 halide perovskites in optical gain. This work holds significant implications for the fields of optical communication and laser technology.

Random lasing emission was investigated from different ZnO nanostructures: a transition from nanowalls to nanoflakes; prepared on seeded glass substrate using simple chemical bath deposition method. The transition geometry of ZnO nanostructures were achieved simply by tuning the equimolar concentration of the chemical bath solution, zinc nitrate hexahydrate, and hexamethylenetetramine from 0.15 M, 0.20 M to 0.25 M. This leads to the changes in particle size of nanostructures from 168.47 nm to 365.91 nm, and finally to 534.07 nm. The population decreased from 131 nanostructures to 100, and finally to 26 nanostructures based on a surface area of 2.8 µm × 2.5 µm, and accordingly enhanced crystallite size was observed as 90.21 nm, 98.04 nm to 110.79 nm for the nanowalls to nanoflakes respectively. These physical variations of the scattering medium affect random lasing emission threshold whereby the threshold excitation power density was reduced from 40 kW/cm2 to 17.14 kW/cm2, and finally to 14.29 kW/cm2 when the structure was in the form of nanoflakes. The emission wavelength from the structures shows a Stokes shift pattern and self-reliant while maintaining a stable emission at 379.7 nm (0.15 M), 382.7 nm (0.20 M), and 387.2 nm (0.25 M). This work demonstrates that by simply tuning the chemical bath solution molarities, changes in nanostructures from nanowalls to nanoflakes were obtained, and upon optical pumping, nanoflakes showed the lowest threshold for random lasing to occur indicating the best structure for ZnO random lasers.

We study Raman spectra of ZnO nanoparticles of 5–12 nm size in the whole range of the first-order phonon bands. We apply the 3D phonon confinement model (PCM) for the interpretation of the observed Raman spectra. It is found that PCM is well applicable to the acoustic modes as well as to the optical ones, despite the fact that PCM has been thought not to be suitable for acoustic phonons. We show that the asymptotic behavior of PCM for the small-size limit is more consistent with the observation than that of the elastic sphere model (ESM). Furthermore, PCM gives detailed information on the complex size-dependent shapes of the phonon bands.

Random lasing from a solid-state gain medium prepared on photonic crystal fibre (PCF) is observed for the first time. Vertically aligned ZnO microrods were prepared on PCF using a simple technique of chemical bath deposition (CBD). A low lasing threshold of 12.2 mJ/cm2 was observed in sample with longer zinc oxide (ZnO) rod length. The variation in morphology and population density did not affect the lasing threshold significantly. Further investigation of the effect of fiber length revealed that a shorter fiber had a lower threshold and showed quenching of the spontaneous emission revealing better lasing output. Simulations based on the morphology of the gain medium revealed light confinement in the structure, validating the origin of the lasing emission. Overall, this study shows the potential of utilising optical fiber as random lasers with a sustainable solid state gain medium. [ABSTRACT FROM AUTHOR]

A study reports about the room-temperature ultraviolet stimulated emission and lasing from optically pumped high-quality ZnO nanowires. Details of the characteristic cavity length that is determined by the Fourier transform of the lasing spectrum are discussed.

Plasma-assisted molecular-beam epitaxy is employed to recognize heteroepitaxial growth of m-plane (1010) InN film on (100)-[gamma]-LiAl[O.sub.2] (LAO) substrate. The structural anisotropy of the m-plane InN epitaxied on LAO is attributed to the [I.sub.1] type base-plane stacking faults according to the modified Williamson-Hall and transmission electron microscopy (TEM) analyses.

High-quality coalescence overgrowth of patterned-grown GaN nanocolumns on c-plane sapphire substrate with metal organic chemical vapor deposition is demonstrated. The atomic force microscopy (AFM) and depth-dependent x-ray diffraction measurements near the surface of the overgrown layer showed that the dislocation density is reduced to one order of magnitude lower than that of the control sample and two to three orders of magnitude lower than those of ordinary GaN templates for fabricating light-emitting diodes.

Self-assembled secondary ZnO nanoparticles, recognized with the agglomeration of crystalline subcrystals are successfully synthesized by a simple sol-gel method. From TEM analyses, the artificial clusters behave like a single crystal structure, owing to the subcrystals coagulating as the same crystal orientation with adjacent ones through the sintering process.

We achieved direct visualization of the piezoelectric potentials in a single bent ZnO microwire (MW) using focused synchrotron radiation (soft x-ray) scanning photoelectron spectro-microscopy. Using radial-line scan across the bent section of ZnO MW, the characteristic core-level shifts were directly related to the spatial distribution of piezoelectric potentials perpendicular to the ZnO polar direction. Using piezoelectric modeling in ZnO, we delineated the band structure distortion and carrier concentration change from tensile to compressed sides by combining the spatial resolved cathodoluminescence characteristics in an individual microwire. This spectro-microscopic technique allows imaging and identification of the electric-mechanical couplings in piezoelectric micro-/nano-wire systems. [ABSTRACT FROM AUTHOR]

In this article, we present a new paradigmfor organometallic hybrid perovskite solar cell using NiO inorganic metal oxide nanocrystalline as p-type electrode material and realized the first mesoscopic NiO/perovskite/ [6,6]-phenyl C61-butyric acidmethyl ester (PC61BM) heterojunction photovoltaic device. The photo-induced transient absorption spectroscopy results verified that the architecture is an effective p-type sensitized junction, which is the first inorganic p-type, metal oxide contact material for perovskite-based solar cell. Power conversion efficiency of 9.51% was achieved under AM 1.5 G illumination, which significantly surpassed the reported conventional p-type dye-sensitized solar cells. The replacement of the organic hole transport materials by a p-type metal oxide has the advantages to provide robust device architecture for further development of all-inorganic perovskite-based thin-film solar cells and tandem photovoltaics. [ABSTRACT FROM AUTHOR]

Uniform hexagonal prismatic zinc oxide rods were grown over the entire alumina substrate at 550 °C using a two-step oxygen injection process, whether the substrates were coated with a catalyst or not. X-ray diffraction showed that all of the depositions exhibited a preferred orientation in the (002) plane. The influence of oxygen concentration was investigated by changing the oxygen flow rate. Oxygen concentration affected the size of ZnO nanorods, especially the diameter. The ZnO nanorods were further checked using high-resolution transmission electron microscopy, photoluminescence, Raman spectroscopy, and room-temperature ultraviolet lasing. The results showed that the rods were single crystals and had excellent optical properties. By observing the growth process, we found that the diameter increased slowly, but the longitudinal growth rate was very high. The growth of ZnO nanorods revealed that the uniform hexagonal prismatic ZnO nanorods were synthesized through vapor deposition growth and a self-catalyzed vapor-liquid-solid (VLS) process. [ABSTRACT FROM AUTHOR]

High-phase-purity zinc-blende (zb) InN thin film has been grown by plasma-assisted molecular-beam epitaxy on r-plane sapphire substrate pretreated with nitridation. X-ray diffraction analysis shows that the phase of the InN films changes from wurtzite (w) InN to a mixture of w-InN and zb-InN, to zb-InN with increasing nitridation time. High-resolution transmission electron microscopy reveals an ultrathin crystallized interlayer produced by substrate nitridation, which plays an important role in controlling the InN phase. Photoluminescence emission of zb-InN measured at 20 K shows a peak at a very low energy, 0.636 eV, and an absorption edge at ∼0.62 eV is observed at 2 K, which is the lowest bandgap reported to date among the III-nitride semiconductors. [ABSTRACT FROM AUTHOR]

We report a simple method for fabricating heterostructured ZnMgO nanowires by annealing the preformed ZnO/MgO core-shell structure. Photoluminescence from the alloy nanowires shows strong near-band-edge (NBE) emission, reflecting good material quality. A blueshift of the NBE emission at room temperature after the annealing treatment is attributed to the diffusion of Mg from the shell into the core ZnO of the nanowires to form a ternary ZnMgO alloy. Band gap engineering and stimulated emissions of ZnMgO nanowires with different Mg doping concentrations are also demonstrated. [ABSTRACT FROM AUTHOR]

ZnO quantum dots (QDs) of controlled sizes have been fabricated by a simple sol-gel method. The blueshift of room-temperature photoluminescence measurement from free exciton transition are observed decreasing with the QD size that is ascribed to the quantum confinement effect. From the resonant Raman scattering, the coupling strength between electron and longitudinal optical phonon, deduced from the ratio of the second- to the first-order Raman scattering intensity, diminishes with reducing the ZnO QD diameter. The size dependence of electron-phonon coupling is principally a result of the Fröhlich interaction. [ABSTRACT FROM AUTHOR]

Both band gap engineering and spatial confinement of optical phonon were observed depending upon the size of ZnO quantum dots at room temperature. Size-dependent blueshifts of photoluminescence and absorption spectra reveal the quantum confinement effect. The measured Raman spectral shift and asymmetry for the E2(high) mode caused by localization of optical phonons agree well with that calculated by using the modified spatial correlation model. [ABSTRACT FROM AUTHOR]