Gas-Induced Confinement-Deconfinement Interplay in Organic-Inorganic Hybrid Perovskite Thin Film Results in Systematic Band Modulation.

Gas-induced growth of organic-inorganic hybrid perovskites, especially methylammonium lead iodide (MAPbI), has shown interesting properties and applications in the area of optoelectronics. In this report, we introduce a method of gas-induced band gap engineering of thin films of MAPbI due to systematic dimensional confinement-deconfinement along the crystallographic axis of growing MAPbI. Interestingly, such a restricted growth phenomenon was observed when the hexylammonium lead iodide (two-dimensional hybrid perovskite) film was exposed to methylamine gas instead of the conventional PbI film-methylamine gas precursor pair.

Single-mode light guiding in diamond waveguides directly written by a focused proton beam.

Ion-implanted waveguides were directly written in bulk single-crystal diamond by scanning a focused 2 MeV proton beam. By controlling the fluence and the lateral size of the proton beam, a bright and near-circular single-mode profile was observed. Propagation loss and effective refractive index of the guided mode were measured by the Fabry-Pérot technique, confirming single-mode guiding.

Molecular Organization Induced Anisotropic Properties of Perylene - Silica Hybrid Nanoparticles.

Optically active silica nanoparticles are interesting owing to high stability and easy accessibility. Unlike previous reports on dye loaded silica particles, here we address an important question on how optical properties are dependent on the aggregation-induced segregation of perylene molecules inside and outside the silica nanoparticles. Three differentially functionalized fluorescent perylene - silica hybrid nanoparticles are prepared from appropriate ratios of perylene derivatives and tetraethyl orthosilicate (TEOS) and investigated the structure property correlation (P-ST, P-NP and P-SF).

Magnetic annihilation of the dark mode in a strongly coupled bright-dark terahertz metamaterial.

Dark mode in metamaterials has become a vital component in determining the merit of the Fano type of interference in the system. Its strength dictates the enhancement and suppression in the amplitude and Q-factors of resulting resonance features. In this work, we experimentally probe the effect of strong near-field coupling on the strength of the dark mode in a concentrically aligned bright resonator and a dark split ring resonator (SRR) system exhibiting the classical analog of the electromagnetically induced transparency effect.

High-resolution 3D imaging and quantification of gold nanoparticles in a whole cell using scanning transmission ion microscopy.

Increasing interest in the use of nanoparticles (NPs) to elucidate the function of nanometer-sized assemblies of macromolecules and organelles within cells, and to develop biomedical applications such as drug delivery, labeling, diagnostic sensing, and heat treatment of cancer cells has prompted investigations into novel techniques that can image NPs within whole cells and tissue at high resolution. Using fast ions focused to nanodimensions, we show that gold NPs (AuNPs) inside whole cells can be imaged at high resolution, and the precise location of the particles and the number of particles can be quantified. High-resolution density information of the cell can be generated using scanning transmission ion microscopy, enhanced contrast for AuNPs can be achieved using forward scattering transmission ion microscopy, and depth information can be generated from elastically backscattered ions (Rutherford backscattering spectrometry).

Proton beam writing of Nd:GGG crystals as new waveguide laser sources.

Focused proton beam writing has been utilized to fabricate optical channel waveguides in Nd:GGG crystals. The 1 MeV proton beam irradiation creates a local modified region with positive refractive index changes at the end of the proton trajectory, in which the channel waveguide could confine the light field in a symmetric way. Room-temperature laser emission has been achieved at 1063.

Thermal optimization and erasing of Nd:YAG proton beam written waveguides.

We report on how the optical and structural properties of Nd:YAG proton beam written waveguides are modified when they experienced annealing treatments from 50 °C to 950 °C. The microstructural changes caused in the vicinity of the nuclear damage region were found to be stable up to 700 °C, so that higher annealing temperatures lead to a complete waveguide erasing. Before this "erasing" temperature, the partial thermal-induced defect recombination reduces the propagation losses, reaching its minimum value (below 1 dB/cm) after a 400 °C thermal annealing.