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Nonlinear selective reflection from the interface YAG window-high density rubidium vapor in the high-temperature cell is studied at the transition 5S$_{1/2}$-5P$_{3/2}$. In the experiment tunable pump and probe lasers are used. The selective reflection spectra for the laser probe beam are investigated at four different rubidium atomic densities and five different pump beam intensities. The estimated dipole-dipole interaction-induced line broadening varies from $13.2$ to $39.6$ GHz, the measured pumped intensities change from $1.2$ to $8.8$ kW$\cdot$cm$^{-2}$. Growth of the pump intensity causes reduction of the magnitude and the width of the recorded selective reflection resonance. We suggest developing all-optical modulators on the basis of nonlinear selective reflection.

Self-focusing of a cw laser beam in rubidium atomic vapor was studied. The beam power and beam spot size at entrance of a glass cell with the rubidium vapor were variable parameters. A steep grow of the threshold power of self-focusing for the small beam radii (< 30 {\mu}m) was observed. Our experimental data are in an agreement with the theoretical results published by Semak and Shneider in 2013. Additional experiments in resonance and transparent media are suggested in order to check and extend our measurements.

We report on the photophysics of a phenyl-substituted PPV both in solution and as a film. For both systems we have studied the decay of the photoluminescence and of the emission anisotropy for a large set of wavelengths spanning the entire photoluminescence spectrum. At long wavelengths the decay behavior is that of an interchain species. At the shortest wavelengths the decay of the photoluminescence from the film is observed to have a long-lived component, in addition to the rapidly decaying component usually associated with energy transfer. We attribute this slow component to emission by isolated intrachain excitons with reduced nonradiative relaxation., Comment: 7 pages, 5 figures

We present a simple method for measuring the gain decay time in a conjugated polymer film by optically exciting the film with two mutually delayed ultrashort pump pulses. When the pump is set at such a power level that amplified spontaneous emission marginally develops along the polymer waveguide, the total output emitted from its edge decays exponentially as a function of the interpulse delay. The corresponding decay time represents the decay time of the gain of the polymer material., Comment: 5 pages, 4 figures

We have experimentally demonstrated the enhancement of coherent Raman scattering in Rb atomic vapor by exciting atomic coherence with fractional stimulated Raman adiabatic passage. Experimental results are in good agreement with numerical simulations. The results support the possibility of increasing the sensitivity of CARS by preparing atomic or molecular coherence using short pulses.

Double dark resonances originate from a coherent perturbation of a system displaying electromagnetically induced transparency. We experimentally show and theoretically confirm that this leads to the possibility of extremely sharp resonances prevailing even in the presence of considerable Doppler broadening. A gas of 87Rb atoms is subjected to a strong drive laser and a weak probe laser and a radio frequency field, where the magnetic coupling between the Zeeman levels leads to nonlinear generation of a comb of sidebands., Comment: 6 pages, 9 figures

We utilize the generation of large atomic coherence to enhance the resonant nonlinear magneto-optic effect by several orders of magnitude, thereby eliminating power broadening and improving the fundamental signal-to-noise ratio. A proof-of-principle experiment is carried out in a dense vapor of Rb atoms. Detailed numerical calculations are in good agreement with the experimental results. Applications such as optical magnetometry or the search for violations of parity and time reversal symmetry are feasible.