We measure spectrally and spatially resolved high-order harmonics generated in argon using chirped multi-cycle laser pulses. Using a stable, high-repetition rate laser we observe detailed interference structures in the far-field. The structures are of two kinds; off-axis interference from the long trajectory only and on-axis interference including the short and long trajectories. The former is readily visible in the far-field spectrum, modulating both the spectral and spatial profile. To access the latter, we vary the chirp of the fundamental, imparting different phases on the different trajectories, thereby changing their relative phase. Using this method together with an analytical model, we are able to explain the on-axis behaviour and access the dipole phase parameters for the short (a s ) and long (a l ) trajectories. The extracted results compare very well with phase parameters calculated by solving the time-dependent Schrödinger equation. Going beyond the analytical model, we are also able to successfully reproduce the off-axis interference structure.

Magnetically doped semiconducting topological insulators J. Appl. Phys. 112, 063912 (2012) Effect of the thickness of the MoO3 layers on optical properties of MoO3/Ag/MoO3 multilayer structures J. Appl. Phys. 112, 063505 (2012) Local conductivity and the role of vacancies around twin walls of (001)−BiFeO3 thin films We report on systematic study of photoluminescence properties of nanocrystalline titanium dioxide films consisting of predominantly anatase nanoparticles with diameters larger than 13 nm. We measured photoluminescence under two selected excitation wavelengths ͑325 nm/442 nm, i.e., above/below band gap excitation͒, under different values of ambient air pressure ͑5-10 5 Pa͒, and in the temperature interval 10-300 K. On basis of our results, we are able to distinguish two different processes leading to photoluminescence: the exciton recombination and the recombination of carriers in the energy states related to the surface of nanocrystals. We propose microscopic models describing well the effects of temperature and ambient conditions on photoluminescence of nanocrystalline titanium dioxide films.

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Plasmon-induced near-infrared electrochromism based on transparent conducting nanoparticles: Approximate performance limits Appl. Phys. Lett. 101, 071903 (2012) Quantum mechanical study of plasmonic coupling in sodium nanoring dimers Appl. Phys. Lett. 101, 061906 (2012) Strong two-photon fluorescence enhanced jointly by dipolar and quadrupolar modes of a single plasmonic nanostructure Appl.