We report on photoluminescence and ultraviolet laser emission from ZnO pellets and thin films of ZnO. Laser emission from disordered polycrystalline thin films and pellets was observed in all directions. ZnO films were deposited on glass substrate at room temperature in various ambient gas pressures of oxygen using the pulsed laser deposition technique. The dependence of laser emission on the size of nanocrystallites observed at different pressures of ambient gas is discussed. Photoluminescence spectra depend on the stoichiometry and the microstructure of the film.

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We report the synthesis of aluminum nanoparticles using pulsed laser ablation in water confined plasma. Nanoparticles have spherical shape and size distribution depends on laser fluence. Strong blue photoluminescence peaks at 405 nm (3.06 eV) and 430 nm (2.89 eV) due to oxygen deficient defects (F, F+, and F++ centers) is reported with different UV excitations. A comparative study of plasma in deionized water and air ambient reveals enhanced line broadening and higher electron density in water confined plasma compared to that in air, in agreement with radiative recombination model. The temporal dependence of spectral radiant energy density of plasma is also discussed.

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We report time-resolved imaging of a laser-ablated carbon plasma plume to investigate the expansion dynamics of C(2) and CN in an ambient atmosphere of nitrogen gas at various pressures. An attempt is made to locate C(2) and CN species in the carbon plasma plume and correlate them with the results of spectroscopic observations. The ablated C(2) and CN species decelerate due to collisions with nitrogen gas and are localized in the slower part (approximately 300 ns) of the expanding plume. Further expansion (<700 ns) of the plasma reveals the concentration of C(2) species on the periphery of the plume, whereas CN dominates at the core of the plume. However, at times greater than 700 ns, the collisions and recombination processes dominate in the plume and C(2) expands slower than CN. The plume dynamics is studied in terms of shock-wave and drag models.

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Laser-produced carbon plasma expanding in vacuum, a low pressure ambient gas (5 mTorr and 100 mTorr) and a nonuniform magnetic field is studied using fast photography. The temporal behavior of various plasma parameters, like velocity, electron density, electron temperature and intensity, is reported. In 5 mTorr air, the plasma breaks into slow and fast components. In the magnetic field, oscillations are observed in the plasma parameters.

We report laser-induced breakdown studies of laboratory air using 0.266, 0.355, 0.532, and 1.06 μm radiation for focal spot varying from 30 to 100 μm. The breakdown intensities were measured for two pulse widths for all four wavelengths. We observe a t−0.5p dependence of pulse width on threshold field at 0.532, 0.355, and 0.266 μm while for 1.06 μm the pulse width dependence of t−0.35p is observed.