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Supercontinuum (SC) generation from alkali antimony zinc borate glasses was investigated using a femtosecond laser. The optical bandgap values were determined for all the glass samples. An enhancement in the generated SC is seen from sodium-doped glass although it possesses the least bandgap among the glass samples. The physical parameters of the glasses such as density, molar volume, refractive index, oxide ion polarizability, and optical basicity have been analyzed and discussed. The smaller values of the metallization criterion indicate the tendency of the glass samples to exhibit metallic behavior, which, in turn, affects the non-linear optical properties of the glasses. The shift in the binding energies of metal cations and oxygen anions was observed using XPS analysis, which gives an understanding about the extent of overlapping of valence orbitals in the glass system. The observations from the physical and structural investigations provide an insight into the anomaly in the enhanced SC generation from the low bandgap sodium-doped glass. [ABSTRACT FROM AUTHOR]

A clear visualization of the physical processes of spatially confined ns laser induced atmospheric air plasma within a rectangular glass cavity using optical imaging is presented. The occurrence of various processes starting from the early plasma and shock wave expansion dynamics to shock reflection at the cavity boundaries and compression of the plasma due to reflected shockwaves is studied using defocused shadowgraphy and self-emission imaging techniques. Experimentally, we evidenced that the counter propagating reflected primary shockwaves interact with the expanding plasma generating a secondary shockwave which compresses the plasma core, modifying the plasma morphology resulting in enhanced plasma parameters. The numerical simulations performed via the two-dimensional hydrodynamic (2D-HD) FLASH codes, revealed that the number density increases up to a maximum of 3.6 times compared to the unconfined plasma. The input laser pulse energy and the aspect ratio of the cavity is observed to play a dominant role in the confinement and compression of the plasma. [ABSTRACT FROM AUTHOR]

The studies on the effect of input laser intensity, through the variation of laser focusing geometry, on radio frequency (RF) emissions, over 30-1000MHz from nanosecond (ns) and picosecond (ps) laser induced breakdown (LIB) of atmospheric air are presented. The RF emissions from the ns and ps LIB were observed to be decreasing and increasing, respectively, when traversed from tight to loose focusing conditions. The angular and radial intensities of the RF emissions from the ns and ps LIB are found to be consistent with sin²θ/r² dependence of the electric dipole radiation. The normalized RF emissions were observed to vary with incident laser intensity (Iλ²), indicating the increase in the induced dipole moment at moderate input laser intensities and the damping of radiation due to higher recombination rate of plasma at higher input laser intensities. [ABSTRACT FROM AUTHOR]

Optical limiting performance and third-order nonlinearity χ(3) are investigated in 5,10,15,20-(tetratolyl) porphyrinato phosphorus (V) dichloride ([(TTP)PVCl2]+). Heavy atom effect exerted by the two axial chlorides is found to result in low fluorescence yield (∅fl), shorter lifetimes of S1,T1 and faster intersystem crossing (ISC), leading to larger excited state absorption (ESA) from T1→Tn. This phenomenon is found to lower the limiting threshold by 30 times and increase the second hyperpolarizability by one and three orders in ps and ns time regimes, respectively. [Copyright &y& Elsevier]