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Abstract: Trefoil and quatrefoil channels between air holes of two microstructure fibers can strongly confine light field and act as highly nonlinear waveguides. Polarization-dependent blue-shifted emissions of femtosecond Ti:sapphire laser pulses were carried out in these channels. The spectra bandwidth of blue-shifted emissions in a trefoil channel is narrower than 10nm and can be tuned slightly by altering the polarization state of pump light. Polarization-dependent blue-shifted emissions from a quatrefoil channel lie in a hollow beam having potential use in optical tweezers. [Copyright &y& Elsevier]

Abstract: The characteristics of harmonic radiation due to electron oscillation driven by an intense femtosecond laser pulse are analyzed considering a single electron model. An interesting modulated structure of the spectrum is observed and analyzed for different polarization. Higher order harmonic radiations are possible for a sufficiently intense driving laser pulse. We have shown that for a realistic pulsed photon beam, the spectrum of the radiation is red shifted as well as broadened because of changes in the longitudinal velocity of the electrons during the laser pulse. These effects are more pronounced at higher laser intensities giving rise to higher order harmonics that eventually leads to a continuous spectrum. Numerical simulations have further shown that by increasing the laser pulse width broadening of the high harmonic radiations can be limited. [Copyright &y& Elsevier]

Abstract: The spectral properties in different concentration of Yb ions (0.5–5mol%)-doped silica glasses are explored in this paper. The glasses are prepared by traditional melting method. The absorption spectra and the fluorescent lifetime (τ f) are measured at room temperature and low temperature (18K). The stimulated cross-section (σ emi) and potential laser properties (β min, I sat, I min) are calculated based on the absorption spectra. The absorption cross-section (σ abs) are in the range 1.08×10−20– 1.18×10−20 cm2 in different glasses, the fluorescence lifetime (τ f) change from 1.9 to 1.2ms with the increase of Yb3+ concentration. The potential laser properties indicate that lead silica glass is a good host for highly Yb ion doping glass. [Copyright &y& Elsevier]

Abstract: Using three-dimensional classical ensembles, we have investigated the enhancement of double ionization of perpendicularly aligned H 2 molecules by a 800nm laser pulse with intensity ranging from 1×1014 W/cm2 to 6×1014 W/cm2. The simulated results show that double ionization probability of H 2 strongly depends on R and reaches a maximum at an intensity independent critical distance R C ≈5a.u. Furthermore, the enhancement of double ionization is more pronounced in the cases of weaker or stronger fields. These results, a well indication of the influence of molecular structures and laser–molecule interactions on double ionization of diatomic molecules, are analyzed in detail and qualitatively explained based on the field-induced barrier suppression model and back analysis. [Copyright &y& Elsevier]

Abstract: Anatase phase TiO2 films have been grown on fused silica substrate by pulsed laser deposition technique at substrate temperature of 750°C under the oxygen pressure of 5Pa. From the transmission spectra, the optical band gap and linear refractive index of the TiO2 films were determined. The third-order optical nonlinearities of the films were measured by Z-scan method using a femtosecond laser (50fs) at the wavelength of 800nm. The real and imaginary parts of third-order nonlinear susceptibility χ (3) were determined to be −7.1×10−11esu and −4.42×10−12esu, respectively. The figure of merit, T, defined by , was calculated to be 0.8, which meets the requirement of all-optical switching devices. The results show that the anatase TiO2 films have great potential applications for nonlinear optical devices. [Copyright &y& Elsevier]