Optical properties of phosphate glasses co-doped with Yb^(3+) and silver nanoparticles

We report the fabrication and spectroscopic characterization of Yb^3＋-doped phosphate glass, also containing silver nitrate. Scanning electron microscopy（SEM） provides the evidence of the formation of silver nano-particles（SNPs）, which are formed as a consequence of melting and thermal decomposition of Ag NO3. Absorption spectra of the samples in the visible-to-near-infrared spectral range reveal the presence of bands centered at 410 nm associated with the SNP-plasmon resonance, and at 976 nm due to the Yb^3＋. Under 916-nm laser-diode pumping, the effect of the SNP reflects that： i） the fluorescence in the 950-nm–1150-nm spectral range is strongly enhanced（～ 30 times）, while the fluorescence decay time associated with the ^2F5/2→^2F7/2transition of Yb^3＋ increases 25%, and ii） the basic lasing properties（saturation pumping intensity, the emission and absorption cross sections） are substantially improved.

Spectral analysis of short-wavelength emission by up-conversion in a Tm3+:ZBLAN dual-diode-pumped optical fiber

The fluorescence evolution along Tm3+-doped Zr F4–Ba F2–La F3–Al F3–Na F(ZBLAN) optical fibers, as well as amplified spontaneous emission in the UV-IR region with emphasis on 350 nm, 365 nm, and 450 nm, is studied,estimating optimal fiber lengths for amplification within the region. The fibers were diode-pumped with single and double lines(687 and/or 645 nm). Double-line pumping presents a quite superior efficiency for producing UV-blue signals with the benefit of requiring very short fibers, around 20 cm, compared to single-line pumping requiring more than 50 cm. A virtual cycle in which the pumps enhance each other’s absorption is the key to these systems.

Optical trapping with structured light: a review

Optical trapping describes the interaction between light and matter to manipulate micro-objects through momentum transfer.In the case of 3D trapping with a single beam,this is termed optical tweezers.Optical tweezers are a powerful and noninvasive tool for manipulating small objects,and have become indispensable in many fields,including physics,biology,soft condensed matter,among others.In the early days,optical trapping was typically accomplished with a single Gaussian beam.In recent years,we have witnessed rapid progress in the use of structured light beams with customized phase,amplitude,and polarization in optical trapping.Unusual beam properties,such as phase singularities on-axis and propagation invariant nature,have opened up novel capabilities to the study of micromanipulation in liquid,air,and vacuum.We summarize the recent advances in the field of optical trapping using structured light beams.

A novel and stretchable carbon-nanotube/Ni@TiO_(2):W photocatalytic composite for the complete removal of diclofenac drug from the drinking water

We present the structural,morphological and photocatalytic properties of stretchable composites made with carbon nanotubes (CNTs),silicon rubber and Ni@TiO_(2):W nanoparticles(TiWNi NPs) with average size of 37±2 nm.Microscopy images showed that the TiWNi NPs decorated the surface of the CNT fibers,which are oriented in a preferential direction.TiWNi NPs presented a mixture of anatase/rutile phases with cubic structure.The performance of the TiWNi powders and stretchable composites was evaluated for the photocatalytic degradation of diclofenac (DCF) anti-inflammatory drug under ultraviolet-visible light.The results revealed that the maximum DCF degradation percentages were 34.6%,91.9%,97.1%,98.5%and 100%for the CNT composite (stretched at 0%),TiWNi powders,CNT+TiWNi(stretched at 0%),CNT+TiWNi (stretched at 50%) and CNT+TiWNi (stretched at 100%),respectively.Thus,stretching the CNT+TiWNi composites was a good strategy to enhance the DCF degradation percentage from 97.1%to 100%,since stretching created additional defects (oxygen vacancies) that acted as electron sink,delaying the electron-hole recombination,and favors the DCF degradation.Raman/absorbance measurements confirmed the presence of such defects.Moreover,the reactive oxygen species (ROS) were determined by the scavenger’s experiments and found that the main ROS were the·OH and O_(2)-radicals,which attacked the DCF molecules,causing their degradation.The results of this investigation confirmed that the stretchable CNT/TiWNi-based composites are a viable alternative to remove pharmaceutical contaminants from water and can be manually separated from the decontaminated water,which is unviable using photocatalytic powders.

Free-space local nonseparability dynamics of vector modes

One of the most prominent features of quantum entanglement is its invariability under local unitary transformations,which implies that the degree of entanglement or nonseparability remains constant during free-space propagation,true for both quantum and classically entangled modes.Here we demonstrate an exception to this rule using a carefully engineered vectorial light field,and we study its nonseparability dynamics upon free-space propagation.We show that the local nonseparability between the spatial and polarization degrees of freedom dramatically decays to zero while preserving the purity of the state and hence the global nonseparability.We show this by numerical simulations and corroborate it experimentally.Our results evince novel properties of classically entangled modes and point to the need for new measures of nonseparability for such vectorial fields,while paving the way for novel applications for customized structured light.