Test station to characterize the emission of a LiDAR.

A test station setup devised to measure the emission characteristics and beam propagation parameters of a light detection and ranging (LiDAR) system is presented. The main blocks of the station to measure the accessible emission, wavelength peak and FWHM, pulse duration, pulse repetition rate, horizontal and vertical angular resolution, field of view, beam propagation factor M 2, beam waist size, waist location, and divergence are described. The performance of this test station was demonstrated using a commercial spinning LiDAR, a Velodyne VLP-16, which successfully enables these measurements for a laser beam with a wavelength of 913 nm.

Resonance energy transfer in self-organized organic/inorganic dendrite structures.

Hybrid materials formed by semiconductor quantum dots and J-aggregates of cyanine dyes provide a unique combination of enhanced absorption in inorganic constituents with large oscillator strength and extremely narrow exciton bands of the organic component. The optical properties of dendrite structures with fractal dimension 1.7-1.8, formed from J-aggregates integrated with CdTe quantum dots (QDs), have been investigated by photoluminescence spectroscopy and fluorescence lifetime imaging microscopy. Our results demonstrate that (i) J-aggregates are coupled to QDs by Förster-type resonant energy transfer and (ii) there are energy fluxes from the periphery to the centre of the structure, where the QD density is higher than in the periphery of the dendrite. Such an anisotropic energy transport can be only observed when dendrites are formed from QDs integrated with J-aggregates. These QD/J-aggregate hybrid systems can have applications in light harvesting systems and optical sensors with extended absorption spectra.

Exact solution for square-wave grating covered with graphene: surface plasmon-polaritons in the terahertz range.

We provide an analytical solution to the problem of scattering of electromagnetic radiation by a square-wave grating with a flat graphene sheet on top. We show that for deep groves there is a strong plasmonic response, with light absorption in the graphene sheet reaching more than 45% due to the excitation of surface plasmon-polaritons. The case of a grating with a graphene sheet presenting an induced periodic modulation of the conductivity is also discussed.

Light scattering by a medium with a spatially modulated optical conductivity: the case of graphene.

We describe light scattering from a graphene sheet having a modulated optical conductivity. We show that such modulation enables the excitation of surface plasmon polaritons by an electromagnetic wave impinging at normal incidence. The resulting surface plasmon polaritons are responsible for a substantial increase of electromagnetic radiation absorption by the graphene sheet. The origin of the modulation can be due either to a periodic strain field or to adatoms (or absorbed molecules) with a modulated adsorption profile.

Resonant Raman scattering in ZnO:Mn and ZnO:Mn:Al thin films grown by RF sputtering.

Raman spectroscopy results obtained under visible (non-resonant) and UV (resonant) excitation for nanocrystalline ZnO, ZnO:Mn and ZnO:Mn:Al thin films grown by radio frequency magnetron sputtering are presented and compared. The origin of the multiple longitudinal optical (LO) phonon Raman peaks, strongly enhanced under resonance conditions, and the effects of the dopants on them are discussed in the framework of the 'cascade' model. It is suggested that the observed suppression of the higher-order LO phonon lines for ZnO:Mn:Al is caused by the dissociation of excitons in the heavily n-type doped material. On the basis of the cascade model interpretation of the higher-order Raman peaks in the resonant spectra, the LO phonon frequencies for wavevectors away from the Γ point are evaluated and compared to previously published phonon dispersion curves.

Nanoscale colour control: W-O graded coatings deposited by magnetron sputtering.

A new design of decorative tungsten oxide coatings is presented. The coatings were deposited with a graded refractive index by magnetron sputtering from a tungsten target and pulsing the reactive gas. The controlled injection of the reactive gas can produce a concentration profile gradient from pure tungsten to tungsten trioxide, determining the final apparent colour of the coating. A dynamic sputtering model was built to simulate the growth of the coating during the reactive gas pulsing which was validated by direct measurement of the gradient of the oxygen content in the deposited coatings. Finally, these results were used for an optical model allowing the optical properties of the deposited tungsten oxide layer to be described, again validated by experimental analysis. This procedure allows the deposition of coatings with the desired colour by using the models to finding the optimal oxygen pulse parameters. This proposed method can be easily applied to almost any metal/metal oxide system.