Coherence creation in an optically thick medium by matched propagation of a chirped laser pulse pair

We consider the simultaneous propagation of a pair of Raman-resonant, frequency-modulated (chirped) laser pulses in an optically thick medium, modeled by an ensemble of $\Lambda$-atoms. A self-organization ('matching`) effect is shown for the chirped pulse pair, which leads to a quasi-lossless propagation. Furthermore, we demonstrate that a well-defined coherent superposition of the atomic ground states and, correspondingly, a coherence is robustly created in the medium that can be controlled by amplitudes of the laser pulses. The proposed scheme can be applied to substantially increase the efficiency of the optical wave mixing processes, as well as in other nonlinear processes where the initial preparation of a spatially extended medium in a coherent superposition state is required

Pattern forming instability induced by light in pure and dye-doped nematic liquid crystals

We study theoretically the instabilities induced by a linearly polarized ordinary light wave incident at a small oblique angle on a thin layer of homeotropically oriented nematic liquid crystal with special emphasis on the dye-doped case. The spatially periodic Hopf bifurcation that occurs as the secondary instability after the stationary Freedericksz transition is analyzed.Comment: 8 pages, 7 figures, LaTeX, accepted to Phys. Rev.

Organic dye for dye-sensitized solar cell

Organic dye for a dye-sensitized solar cell (DSSC) comprising at least one electron-acceptor unit and at least one π-conjugated unit. Said organic dye is particularly useful in a dye-sensitized photoelectric transformation element which, in its turn, can be used in a dye-sensitized solar cell (DSSC)

Compacting of fly dusts from cupola and electric arc furnace

Recycling and utilization of dust waste is important not only from the point of view of its usage as an alternative source of raw materials, but regarding the environmental problems also. Dust emissions arise from thermal and chemical or physical processes and mechanical actions. Two kinds of fl y dusts from cupola furnaces (hot and cold blast cupola furnace) and fl y dust from electric arc furnace were used by experiments. They were pelletized only with addition of water and briquetted with diff erent addition of water glass, bentonite and cement. Quality of briquettes was tested by compression – strength test and by break down test in green state, after drying and afterstoring (1 month)

Structure-properties relationships in triarylamine-based donor-acceptor molecules containing naphtyl groups as donor material for organic solar cells

The effects of replacing the phenyl rings of triphenylamine (TPA) by naphtyl groups are analysed on a series of push-pull molecules containing a 2-thienyl-dicyanovinyl acceptor group. UV-Vis absorption spectroscopy and cyclic voltammetry show that the introduction of one or two naphtyl groups in the structure has limited effects on the optical properties and energy levels of the molecule. On the other hand, the evaluation of the compounds as donor material in bi-layer solar cells with C60 as acceptor shows that the number and mode of linkage of the naphtyl groups exert a marked influence on the power conversion efficiency (PCE) of the cell. Two naphtyl groups lead to a decrease of PCE with respect to TPA, while a single naphtyl group produces opposite effects depending on the linking mode. Compared to TPA, an alpha-naphtyl group leads to a small decrease of PCE while in contrast a beta-naphtyl leads to a ~35% increase of PCE due to improved short-circuit current density (Jsc) and fill-factor. The determination of the hole-mobility of these two donors by the space-charge-limited current method shows that these effects are correlated with the higher hole-mobility of the β-naphtyl compound

Organic dye for dye-sensitized solar cells

Organic dye for a dye-sensitized solar cell (DSSC) comprising at least one electron-acceptor unit and at least one π-conjugated unit. Said organic dye is particularly useful in a dye-sensitized photoelectric transformation element which, in its turn, can be used in a dye-sensitized solar cell (DSSC)

Organic dye for dye-sensitized solar cells

Organic dye for a dye-sensitized solar cell (DSSC) comprising at least one electron-acceptor unit and at least one π-conjugated unit. Said organic dye is particularly useful in a dye-sensitized photoelectric transformation element which, in its turn, can be used in a dye-sensitized solar cell (DSSC)

Kompaktiranje lebdeće prašine iz kupolne i elektrolučne peći

Recycling and utilization of dust waste is important not only from the point of view of its usage as an alternative source of raw materials, but regarding the environmental problems also. Dust emissions arise from thermal and chemical or physical processes and mechanical actions. Two kinds of fl y dusts from cupola furnaces (hot and cold blast cupola furnace) and fl y dust from electric arc furnace were used by experiments. They were pelletized only with addition of water and briquetted with different addition of water glass, bentonite and cement. Quality of briquettes was tested by compression – strength test and by break down test in green state, after drying and after storing (1 month).Recikliranje i iskorištavanje otpadne prašine važno je zbog aspekta njezine uporabe kao alternativnog izvora sirovina, ali također i s obzirom na ekološke probleme. Emisija prašina nastaje iz termičkih, kemijskih ili fi zikalnih procesa te mehaničkih aktivnosti. U eksperimentalnom dijelu korištene su dvije vrste lebdeće prašine iz kupolne peći (s predgrijanim i hladnim zrakom) te elektrolučne peći. Prašina je peletizirana samo uz dodatak vode i briketirana s različitim dodatkom vodenog stakla, bentonita i cementa. Kvaliteta briketa je određena ispitivanjem tlačne čvrstoće u sirovom stanju, nakon sušenja i nakon skladištenja (1 mjesec)

Miniaturization of molecular conjugated systems for organic solar cells: towards pigmy donors

Organic solar cells with short-circuit current densities and conversion efficiencies of ca. 7.0 mA cm(-2) and 2.0%, respectively, have been fabricated with a very small molecular donor based on substituted triarylamines