Metal chalcogenides are extensively studied as infrared second-order nonlinear optical (NLO) materials. Among the candidates, ones containing cations with lone-pair electrons in the structure have received great interest in view of the lone-pair electrons’ special contribution to the NLO property . Here, we revisit such a sulfide Sb 6 Sb 6 S 17 and study its NLO property , which represents a novel structure-type of NLO material. It exhibits phase-matchable second-harmonic generation activity, and the powder sample shows a laser-induced damage threshold (LIDT) around 3.2 times that of AgGaS 2 when both have the particle sizes of 75–110 μ m. Its optical energy gap is measured to be 1.92 eV and the powder sample has a transparency range from 0.65 to 25 μ m. The electronic structure and optical property calculations are also performed.
The mixed surfactants of dodecyltrimethylammonium bromide (DTAB) and 1-dodecyl-3-methylimidazolium bromide (C 12 mimBr) in aqueous solutions were studied by measurement of electrical conductivity and isothermal titration microcalorimetry (ITC). The critical micelle concentrations (cmc) and the degree of dissociations of counter ions were determined for this system at various surfactant compositions, and the thermodynamic properties of micellization were evaluated. A one-parameter Margules equation was used to fit the cmc values to calculate the mole fraction, the activity coefficients of two surfactant components and the excess properties in mixed micelles.
Xin He,Rongfei Wei,Xiangling Tian,Jianrong Qiu,Mei Zhang,Qingguang Zeng,Junyan Liu
Te-Bi 2 Te 3 alloy thin film has grown on silicon dioxide substrate by thermal evaporation technique. The Bi 2 Te 3 rhombohedral structure enriched Te in the prepared thin film was identified by high solution transmission electron microscopy (HRTEM), X-Ray diffraction (XRD), Raman spectrum and X-ray photoelectron spectroscopy (XPS). Interestingly, the Te-Bi 2 Te 3 alloy thin film presents a changeover from saturable absorption (SA) to reverse saturable absorption (RSA) as continuously increasing the input intensity, which has been investigated using the open-aperture (OA) z-scan measurement under a femtosecond-pulsed laser at 800 nm. A high modulation depth of 48.3% and large saturation intensity of 24.1GW/cm 2 of the thin film were obtained. Moreover, a large nonlinear absorption coefficient β of ∼10 3 cm/GW is increased with the input intensity elevated. The research results demonstrate that the Te-Bi 2 Te 3 alloy thin film could be an emerging optical material for saturable absorber in Q-switched or mode-locking fiber lasers at low incident intensity while serve as optical limiter at high incident intensity.
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