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The resonance fluorescence spectra of N two-level quantum systems located around the spherical nanoantenna
Full text linkModification of the resonance fluorescence spec-trum of a two-level atom driving by a lasermonochromatic field in the close proximity of aplasmonic nanostructure (metal sphere) is studiedin detail. It is shown that one can control thisspectrum varying four key parameters: distancebetween the atom and the nanosphere, atom’s lo-cation around the nanosphere, the radius of thenanosphere, and polarization of the incident ra-diation. These parameters affect the local fieldenchancement, transition frequency shift and themodification of the radiative decay rate of the atominteracting with the nanosphere, which lead tomodification of the resonance fluorescence spec-trum of the atom (frequency shift of the satellitelines in the Mollow-type triplet, widths of the lines,the spectrum intensity) by contrast with that onein free space. The permittivity of the metal thenanosphere is made of is also an additional param-eter, which defines the nonradiative decay. The lat-ter in combination with other parameters allows tocontinuously control the transition from resonancefluorescence enhancement to its quenching. Thecalculation results are generalized to the case ofN two-level atoms, distributed around the nanopar-ticle in the close proximity of its surface. Thecalculations were performed for different positionsof the detector relative to the system nanoparticle-atom(s)
Construction of microfluidic biochips with enhanced functionalities using 3D femtosecond laser direct writing
Full text linkThe extreme nonlinear interaction betweenfemtosecond laser pulses and large-band-gapmaterials has enabled three-dimensional (3D)microfabrication inside transparent materials. In thepast decade, this technique has been used forcreating a variety of functional components in glassmaterials, including microoptics, microfluidics,microelectronics, micromechanics, etc. Using thesebuilding blocks, femtosecond laser microfabricationalso allows for construction of highly integratedmicrodevices. Here, we provide an overview of ourlatest progress made along this direction, includingfocal spot engineering and nanofluidic fabrication.In particular, we show that 3D micro-/nano-fluidiccomponents with arbitrary geometries can bedirectly formed inside glass. This opens uppromising prospects for a broad spectrum ofapplications based on compact and complex 3Dmicrofluidic networks. Our work shows that thistechnique holds promise for fabricating 3D hybridmicro-systems, such as Lab-on-a-chip devices andMicro Total Analysis Systems in the future
Modeling of non-equilibrium effects in silicon irradiated by pulsed laser
Full text linkIn this paper, we use the methods of mathematical modeling to investigate the action of laser pulse (picosecond) with a wave length of λL=0.53μm and the photon energy exceeding the band gap of silicon ħω>Eg on silicon target. The main feature of these regimes of laser irradiation is strong non-equilibrium of heating and melting processes, which is manifested in a large temperature difference between the carriers and the lattice
A Study on the Vibration Characteristics of CFRP Composite Materials using Time-Average ESPI
Full text linkThe ESPI (Electronic Speckle PatternInterferometry) is a real-time, full-field, nondestructiveoptical measurement technique. In thisstudy, ESPI was proposed for the purpose ofvibration analysis for new and composite materials.Composite materials have various complicatedcharacteristics according to the materials,orientations, and the stacking sequences of the plyand boundary conditions. Therefore, it is difficult toanalyze composite materials. For efficient use ofcomposite materials in engineering applications thedynamic behavior (i.e., natural frequencies andnodal patterns) should be known. With the use ofTime-Average ESPI, one could easily analyzevibration characteristics of composite material byreal time. We manufactured two kinds of laminatedcomposites (i.e., symmetry and asymmetry) whichwere composed of CFRP(Carbon Fiber ReinforcedPlastics) and the shape of the test piece was ofrectangular form
Progress in the fabrication of rare earth doped optical fiber by standard and Sol-Gel derived granulated oxides
No full textWe produced active optical fibers by the doped granulate silica-method. The granulates were derived from the sol-gel technology. We determined volume percentage and distribution of chemical elements in the fabricated glasses fiber by the analytical technique of Energy-Dispersive X-ray (EDX), Scanning Electron Microscopy (SEM), Electron Probe Microanalysis (EPMA) and the degree of crystallization by X-Ray Diffraction analysis (XRD). Furthermore we measured fluctuations of the Refractive Index Profile (RIP) and scattering losses of the fiber core. It was observed from the RIP measurement that the average index difference with respect to the undoped silica was 5.3*10-3, and thus the optical fiber has a numerical aperture of 0.12. XRD measurements and investigations with SEM showed that the manufactured optical fiber has an amorphous structure. The dopant and co-dopant elements in the core region were uniformly distributed. Although we found strong isolated scattering centers in the fabricated fiber, the loss of the fibers was determined to be 0.35- 3dB/m for selected fiber pieces. Here we present our progress of improving the optical quality of fibers produced from granulates.
Pyrometric Monitoring of Gas-Assisted Cutting of Steel Using Fiber Laser
Full text linkMeasurements of the temperature in zone of action of laser radiation on the molten metal have been performed. The results are reported for different speed of cutting of mild-steel plate of 3 mm-thick with high-power fiber laser; oxygen was used as an assisted gas. Researches demonstrate that fluctuations of local temperature are related to unequal radiation absorption that associates with local deformations of surface of melt. Thus noise spectrum of those fluctuations reflects turbulent surface deformation caused by gas jet and capillary waves. The standard temperature deviation does not exceed 10 K on the frequency of 7 KHz and above, and power law of spectrum of density of fluctuations of local temperature is about “-2.8” in range of capillary turbulence. Thus we can distinguish radiation pulsation due to laser cutting from other processes of radiation affection to the sample, including unwanted, degrading the quality of technological operations. The results of investigation can be useful for monitoring laser cutting process
Powder technology and innovative fiber design enabling a new generation of high-power single-mode-fiber laser sources
Full text linkBy simultaneously providing ultra large mode effective area (ULMA) and close to diffraction limited laser beams, Yb-doped double-clad photonic crystal fibers have become key components for power scaling in fiber laser systems. Despite their advantages, such fibers suffer from some drawbacks among which tremendous fabrication complexity and arising costs, high bending losses and poor integrability. In this paper, we show how the REPUSIL technique, which is an alternate synthesis method to produce high-quality doped-silica, enables the design of a new generation of ULMA rare-earth-doped fibers. Some examples of innovative fiber designs will be shown and commented together with a first experimental demonstration of all-solid Yb-doped double-cladding fiber fabrication. The thermal effects, which play a major role at high power laser level and drastically compromise the single-mode regime, are also investigated. The very first experimental results for the fiber and laser characterization are given
Dressing and Feeding the Family, or Cakes and Garments for the Gods?
Full text linkIn the built environment of a past society it is often difficult to distinguish between sacred and profane objects and places. We struggle with the difficult tasks of recovering and understanding the behaviours that took place in domestic and public units. Baking, spinning and weaving can be traced very well in the archaeological record from artifacts such as ovens, spindle whorls, loom weights and other remnants representing a loom. Traces of weaving and baking are often found in domestic context. Weaving and backing for a temple and especially weaving clothes and backing bread for a deity are well-known phenomena in the ancient Near East. But in the archaeology of the Southern Levant weaving and baking in association with a temple or a shrine seems to be overlooked.Khirbet al Mudayna, Tell Deir Alla and Tell es-Saidiyeh, situated in Transjordan, with their huge and concentrated numbers of Iron Age loom weights and distinctive architecture, indicate production for others than the direct inhabitants, suggesting specialization and trade. But who were these others. By comparing the features of the three sites an answer to the above question can be indicated
L2 accent and pronunciation research: acquisition, teaching, attitudes
Full text linkThis thematic issue brings together a selection of papers presented at the international conference L2 accent and pronunciation research: acquisition, teaching, attitudes held at the University of Venice Ca’ Foscari in November 2023. Four articles are dedicated to the topic of phonological acquisition (both in perception and production) related to specific L2/L3 features (prominence in German, linking of contiguous vowels in Spanish, the labiovelar approximant, the alveolar trill and unreduced vowels in Polish). Three papers focus on attitudes, i.e. on the perception and evaluation of L2 Icelandic (with an English, Danish, Tagalog, Lithuanian or Polish accent), of L2 Spanish (produced by Italian university students), and of English as an international language (EIL) in the multicultural context of a secondary school in Tanzania. The final contribution deals with the teaching of L2 English pronunciation to very young Brazilian children. A common thread running through most of the contributions is the goal of intelligibility, rather than nativeness, in L2 pronunciation
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