Single-mode laser is realized in a cesium lead halide perovskite submicron sphere at room temperature. All-inorganic cesium lead halide (CsPbX3, X = Cl, Br, I) microspheres with tunable sizes (0.2–10 μm) are first fabricated by a dual-source chemical vapor deposition method. Due to smooth surface and regular geometry structure of microspheres, whispering gallery resonant modes make a single-mode laser realized in a submicron sphere. Surprisingly, a single-mode laser with a very narrow line width (∼0.09 nm) was achieved successfully in the CsPbX3 spherical cavity at low threshold (∼0.42 μJ cm–2) with a high cavity quality factor (∼6100), which are the best specifications of lasing modes in all natural nano/microcavities ever reported. By modulating the halide composition and sizes of the microspheres, the wavelength of a single-mode laser can be continuously tuned from red to violet (425–715 nm). This work illustrates that the well-controlled synthesis of metal cesium lead halide perovskite nano/microspher...

Single-Mode Lasers Based on Cesium Lead Halide Perovskite Submicron Spheres.

In the last two decades, pulsed-laser ablation has received attention from researchers in microand nanotechnology. During the development of laser ablation in materials processing, several media, such as vacuum, air, gases and liquids, have been used to improve the quality and quantity of laser machining and production of nanoparticles. The laser-ablation environment is important in order to control the average size and chemical compositions of nanoparticles. Conducting the laser-ablation process in liquid environments has become of increasing relevance for the production of precise and pure micromachining and nanomaterials. In addition, deionised water has been found to be the optimal environment to produce nanoparticles for bioapplications.

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Laser Ablation in Different Environments and Generation of Nanoparticles

Lasing operation in the CsPbBr3 perovskite micron hemisphere cavity grown by chemical vapor deposition

We developed a prototype holographic data storage drive and verified the feasibility of using it for archival purposes. Holograms recorded on a recording medium become distorted as a result of photopolymerization and changes in ambient temperature. For stable reproduction, wavefront compensation technology was incorporated in the drive. The hologram distortion was optically compensated by controlling the wavefront of the laser beam. We also applied this method to the wavelength adjustment in data reproduction and confirmed that it expanded the wavelength shift margin. We configured the drive for 8K UHDTV playback and successfully reproduced compressed 8K UHDTV video stream data recorded on a holographic disc in real time.

Prototype holographic data storage drive with wavefront compensation for playback of 8K video data

Toward achieving an efficient micro-optical temperature sensor in a wide visible spectral range, Sm3+:ZnO micro-spheres are fabricated by the laser ablation technique. Visible range whispering gallery mode resonances are observed and are found to be lasing above low optical threshold with a quality factor of the order of 103. A temperature-induced change in whispering gallery modes is observed with a sensitivity of 0.04 nm/°C from the micro-sphere of diameter 10.5 μm. Using these results, cost-effective and bio-compatible miniature temperature sensors that operate in the visible spectral range could be devised.

Biocompatible miniature temperature sensor based on whispering gallery modes of Sm3+ activated ZnO optical micro-resonators

Highly crystalline and smooth 1% Ho3+ doped ZnO microspheres with diameters ranging from 0.5 to 15 μm were synthesized using laser ablation technique. Near band edge whispering gallery mode (WGM) resonances from Ho:ZnO microspheres with a single oscillation route in the UV range are observed with 355 nm excitation. Apart from the significantly enhanced visible WGM resonances associated with intrinsic oxygen vacancy defects by Ho3+ doping, the visible range WGM resonances associated with the Ho3+ 5F5 → 5I8 emission at 629–690 nm are also observed with a 488 nm excitation. The WGMs of Ho3+ f-f emission possess lower threshold and high Q-factor values.

Room temperature WGM resonances in the red spectral range from Ho3+ activated ZnO micro-spherical cavities

We have succeeded in growing the ZnO spherical microcrystals by a simple laser ablation in air, and we have obtained ultraviolet (UV) whispering-gallery-mode (WGM) lasing from the sphere under pulsed laser excitation. In this growth technique, a solid ZnO target is rapidly heated by laserinduced plasma, and melted target is splashed from the irradiated spot as droplets. Then, the droplets are crystallized into spherical shapes by the surface tension during the dropping process. This rapid melting and solidifying process may be effective for doping impurities into ZnO. In this study, we fabricated P-, Sb-, and Mg-doped ZnO microspheres, and investigated their structures and optical properties. A blue-shift of UV WGM lasing from Mg-doped ZnO microsphere was obtained, indicating that the band-gap engineering of ZnO microsphere grown by the simple ablation technique was achieved.

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Fabrication of P-, Sb-, and Mg-doped ZnO spherical microcrystals by laser ablation in air

We succeeded in synthesizing antimony (Sb)-doped zinc oxide (ZnO) microspheres by ablating a sintered ZnO target containing Sb in air. The structural properties of the microspheres were investigated by Raman scattering studies. The Zn–Sb related local vibrational mode (LVM) was detected around 238 cm−1. Room-temperature photoluminescence (PL) properties of the microspheres were investigated under cw and pulsed laser excitations, and ultraviolet (UV) emission and whispering-gallery-mode (WGM) lasing were observed from the microspheres. Furthermore, a p–n heterojunction was formed between a single Sb-doped ZnO microsphere and an n-Al-doped ZnO thin film, and a good rectifying property with a turn-on voltage of approximately 1.8 V was observed in the current–voltage (I–V) characteristics across the junction.

https://iopscience.iop.org/article/10.7567/JJAP.55.08RE07/pdf

Synthesis and characterization of Sb-doped ZnO microspheres by pulsed laser ablation

The electron binding energies of the ligand-protected gold/silver-based cluster anions, [Au25(SR)18]−, [XAg24(SR′)18]2– (X = Ag+, Au+, Pd0, or Pt0), and [PdAu24(C≡CR″)18]2– having icosahedral M13 superatomic cores, were reexamined by gas-phase photoelectron spectroscopy (PES) on a significantly intensified mass-selected ion beam. Laser fluence-dependent PE spectra and pump–probe PES revealed that the previous PE spectra were contaminated by PE signals due to the two-photon electron detachment via long-lived photoexcited states. Although the adiabatic electron affinities (AEAs) of the corresponding oxidized forms were found to be 1–2 eV larger than those previously reported, the effects of doping and ligation were not qualitatively affected. (1) The AEA of the Ag13 superatom (∼4 eV) was not appreciably affected by doping a Au atom at the center but was reduced by ∼2 eV by doping Pd or Pt, and (2) the AEA of PdAu12 protected by Au2(C≡CR″)3 units was much larger than that of PdAg12 protected by Ag2(SR′)3 units.

Electron Affinities of Ligated Icosahedral M13 Superatoms Revisited by Gas-Phase Anion Photoelectron Spectroscopy

Recently, laminated rubber bearings are widely used as seismic isolators for road bridges. Although many studies have been conducted on the dynamic model of High Damping Rubber (HDR) bearings, few models can reflect phenomena such as the dependency of experienced shear strain on initial history. To develop a model that can represent the dependency of the experienced shear strain of HDR and a dynamic loading test was conducted using HDR specimens. The hysteresis characteristics of HDR was measured by applying a horizontal vibration using a hybrid actuator under a constant vertical load. Based on the cyclic shear test, the mechanical properties of HDR were calculated such as absorbed energy, hysteresis loop area, equivalent stiffness, equivalent damping ratio. Dynamic analysis was also performed from the experimental results. The dynamic model applied in program analysis is a bilinear type double-target model. This model can express the nonlinear characteristics related to the initial history of HDR bearings. The parameters required for dynamic analysis were determined from the experimental results. Through this dynamic analysis, the effectiveness of the bilinear type double target model was verified. In this research, a high damping rubber specimen was used.

https://iopscience.iop.org/article/10.1088/1742-6596/1687/1/012019/pdf

Yuki Fujiwara

Papers

Room temperature WGM resonances in the red spectral range from Ho3+ activated ZnO micro-spherical cavities

Fabrication of P-, Sb-, and Mg-doped ZnO spherical microcrystals by laser ablation in air

Synthesis and characterization of Sb-doped ZnO microspheres by pulsed laser ablation

Electron Affinities of Ligated Icosahedral M13 Superatoms Revisited by Gas-Phase Anion Photoelectron Spectroscopy

Evaluation of mechanical properties considering hysteresis characteristic of high damping rubber bearing