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The pump power dependence of the spatial gating properties of femtosecond optical Kerr gate (OKG) was investigated using coaxial two-color optical Kerr measurements in CS. As the pump power increased, the spatial pattern of the optical Kerr signals changed from a Gaussian spot to a ring form, and then a spot surrounded by a concentric ring, successively. By comparing the experimental data with the calculation results and measuring the pump power dependence of the OKG signal intensity, we demonstrated that the spatial variation of OKG transmittance could be attributed to the non-uniform spatially distributed phase change of the probe beam, due to the transient birefringence effect induced by pump beam with transverse mode of a Gaussian distribution. [ABSTRACT FROM AUTHOR]

Gradient-index modulation prefabrication in the cladding of standard telecom fibers was proposed for femtosecond laser processing of Type II-IR fiber Bragg gratings. The refractive index of the prefabricated region in the cladding had a large gradient across the laser beam, which could act as a cylindrical lens to enhance the focusing of laser beam when writing Type II-IR gratings. With the help of prefabrication, the threshold pulse energy for processing Type II-IR FBGs was lowered from 750 μJ to 520 μJ. The fabricated FBGs showed good thermal stability at temperatures over 900 °C. [ABSTRACT FROM AUTHOR]

Abstract: Microchannels are fabricated inside silicon along the direction of laser beam by a femtosecond laser at 800nm, which is located at the absorption region of silicon. Formation mechanism of the microchannels is attributed to spherical aberration. The element change in surrounding of the microchannel is characterized, and results show that oxygen is incorporated into silicon after irradiation. The origin of the oxygen incorporation and the laser intensity dependence of the amount of oxygen are discussed, respectively. [Copyright &y& Elsevier]

Abstract: Periodic surface nanostructures induced by femtosecond laser pulses on polycrystalline ZnO are presented. By translating the sample line-by-line under appropriate irradiation conditions, grating-like nanostructures with an average period of 160nm are fabricated. The dependence of surface morphologies on the processing parameters, such as laser fluence, pulse number and laser polarization, are studied by scanning electronic microscope (SEM). In addition, photoluminescence (PL) analysis at room-temperature indicates that the PL intensity of the irradiated area increases significantly compared with the un-irradiated area. Using femtosecond laser pulses irradiation to fabricate periodic surface nanostructures on polycrystalline ZnO is efficient, simple and low cost, which shows great potential applications in ZnO-based optoelectronic devices. [Copyright &y& Elsevier]