Photorefractive screening-photovoltaic solitons are observed in lithium niobate. Two-dimensional bright circular solitons are formed thanks to a strong static bias field, externally applied, opposite to the photovoltaic internal field. The dynamics of the soliton formation is monitored and compared to a time-dependent numerical model allowing determination of the photovoltaic field. Efficient single mode waveguides are shown to be memorized by the soliton beam for a long time. (C) 2004 American Institute of Physics

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The light emission properties of the complex formed from deoxyribonucleic acid (DNA)-cetyltrimethylammonium chloride (CTMA) surfactant doped with different concentrations of Rhodamine 610 (Rh610) dye and dissolved in butanol are investigated and discussed. The results are compared to those obtained when only the Rh610 dye is dissolved in butanol, at the same concentrations. The light emission is excited in the investigated samples by the nanosecond pulses of a frequency-doubled Nd:YAG laser, at a wavelength of 532 nm. We have demonstrated the lasing effect in the investigated complex and we have studied its efficiency and coherence properties. The lasing properties of the Rh610 dye are favourably influenced by the presence of the DNA-CTMA complex in the investigated compound. It leads to an increase in the lasing efficiency and in the slope efficiency. Also the temporal coherence of the emitted light is larger and the emission can be tuned to shorter wavelengths.