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BaTiO3 ferroelectric nanoparticles have provided benefits to numerous liquid crystal applications, while the chemistry of these nanocolloids was not fully understood. In this paper, infrared absorption spectra reveal that ferroelectric BaTiO3 nanocolloids are more than BaTiO3 nanoparticles in heptane with an oleic acid surfactant as previously believed. It is shown that ball-milling plays a bigger role than just a top-down approach for creating nanoparticles; it also is a means of mechanochemical synthesis. This paper demonstrates that mechanochemical synthesis is responsible for converting a large amount of the oleic acid to a metal carboxylate compound. This suggests that one cannot treat the oleic acid as a mere surfactant when considering new methods/recipes to improve fabrication processes for creating highly ferroelectric nanoparticles or when exploring the various effects that the organic additives may have on liquid crystal systems. [ABSTRACT FROM AUTHOR]

Metal-dielectric nanolaminates represent a class of hyperbolic metamaterials with uniaxial permittivity tensor. In this study, we critically compare permittivity extraction of nanolaminate samples using two techniques: polarized reflectometry vs. spectroscopic anisotropic ellipsometry. Both Au/MgF2 and Ag/MgF2 metal-dielectric stacks are examined. We demonstrate the applicability of the treatment of the multilayered material as a uniaxial medium and compare the derived optical parameters to those expected from the effective medium approximation. We also experimentally compare the effect of varying the material outer layer on the homogenization of the composite. Additionally, we introduce a simple empirical method of extracting the epsilon-near-zero point of the nanolaminates from normal incidence reflectance. The results of this study are useful in accurate determination of the hyperbolic material permittivity and in the ability to tune its optical properties. [ABSTRACT FROM AUTHOR]

Small clusters of cesium-lead-iodide perovskites (CLIPs) have been prepared in the Na-X zeolite matrix and studied by means of spectroscopy and quantum chemical modeling. Regularity of pores in single crystals of zeolite assures the formation of clusters of a certain size. By the first-principles quantum chemical calculations, we have determined that clusters Cs 4 PbI 6 , Cs 5 Pb 2 I 9 , and probably Cs 7 Pb 5 I 16 with a size of 0.74, 1.29, and 1.36 nm, respectively, have elevated stability compared to other species, and they fit into the pores of Na-X zeolite. Electronic energy spectra of these clusters have been calculated and compared with experimentally measured ones., Competing Interests: The authors declare no competing financial interest., (© 2021 The Authors. Published by American Chemical Society.)

We report, to the best of our knowledge, the first super-octave femtosecond polycrystalline Cr:ZnS laser at the central wavelength 2.4 µm. The laser is based on a non-polarizing astigmatic X-folded resonator with normal incidence mounting of the gain element. The chromatic dispersion of the resonator is controlled with a set of dispersive mirrors within one third of an optical octave over 2.05-2.6 µm range. The resonator's optics is highly reflective in the range 1.8-2.9 µm. The components of the oscillator's output spectrum at the wavelengths 1.6 µm and 3.2 µm are detected at -60 dB with respect to the main peak. Average power of few-cycle Kerr-lens mode-locked laser is 1.4 W at the pulse repetition frequency 79 MHz. That corresponds to 22% conversion of cw radiation of Er-doped fiber laser, which we used for optical pumping of the Cr:ZnS oscillator.

Experimental and computational studies of resonant Raman spectra of truly monosized (CdSe) 33 and (CdSe) 34 nanoclusters have been performed. First-principles calculations of vibrations are performed to account for the peculiarity of the spectrum and resonant Raman selection rules. The calculation method is based on the analysis of the spatial distribution of the electron density in the ground and excited states and the corresponding displacement of atoms after the electronic transition. The calculated vibrational density of states and resonant Raman spectra of CdSe nanoclusters in a core-cage arrangement are distinctively different from those of small nanocrystals in the bulk fragment model and reasonably agree with the experimentally observed spectral features. The agreement can be considered as experimental evidence for the shell structure of "magic" CdSe nanoclusters. The resonant conditions for the Raman measurements and two different kinds of samples stabilized with decylamine in toluene and with cysteine in water ensure the reliability of our measurements and the minor influence of the stabilizer.

We report, to the best of our knowledge, the first fully referenced Cr:ZnS optical frequency comb. The comb features few cycle output pulses with 3.25 W average power at 80 MHz repetition rate, spectrum spanning 60 THz in the middle-IR range 1.79-2.86 µm, and a small footprint (0.1 m 2 ), The spectral components used for the measurement of the comb's carrier envelope offset frequency were obtained directly inside the polycrystalline Cr:ZnS laser medium via intrinsic nonlinear interferometry. Using this scheme we stabilized the offset frequency of the comb with the residual phase noise of 75 mrads.

Spontaneous emission of Eu(3+) ions is studied in thin organic films deposited onto several different substrates. It has been demonstrated that the presence of a metallic surface in close vicinity to emitting Eu(3+) ions causes modifications of their spontaneous emission spectra, in particular, the change in the relative strengths of magnetic-dipole and electric-dipole transitions. The character and the magnitude of the effect depend on the polarization and the observation angle. The experimental data are discussed in terms of modification of transition probabilities and account for the interference between directly emitted and reflected light waves.