Two-dimensional performance of uniform irradiation with the use of an edge-softened lens array and spectral dispersion

A lens array composed of edge-softened elements is used to improve on-target irradiation uniformity in the Shenguang II Laser Facility, with which a Fresnel pattern of suppressed diffraction peaks is obtained. Additional uniformity can be reached by reducing short-wavelength interference speckles inside the pattern when the technique of smoothing by spectral dispersion is also used. Two-dimensional performance of irradiation is simulated and the results indicate that a pattern of steeper edges and a flat top can be achieved with this joint technique. (c) 2007 Optical Society of America.

Magnetic field modulated direct overwrite with pulsed laser irradiation for TbFeCo magneto-optical disks

WE have designed a dual-beam magneto-optical (MO) storage system to test the dynamic storage properties of MO disks. The characteristics of this dual-beam system are demonstrated. Magnetic field modulated direct overwrite, which is a promising technique for highspeed MO storage, is realized on TbFeCo MO disks with this dual-beam MO system. The effect of light intensity, magnetic field intensity, and linear velocity of the disk and the modulating frequency variation on carrier-to-noise ratio is investigated. (C) 1997 Society of Photo-Optical Instrumentation Engineers.

Femtosecond laser pulse irradiation of Sb-rich AgInSbTe films: Scanning electron microscopy and atomic force microscopy investigations

The single-layer and multilayer Sb-rich AgInSbTe films were irradiated by a single femtosecond laser pulse with the duration of 120 fs. The morphological feature resulting from the laser irradiation have been investigated by scanning electron microscopy and atom force microscopy. For the single-layer film, the center of the irradiated spot is a dark depression and the border is a bright protrusion; however, for the multilayer film, the center morphology changes from a depression to a protrusion as the energy increases. The crystallization threshold fluence of the single-layer and the multilayer films is 46.36 mJ/cm(2), 63.74 mJ/cm(2), respectively.

Morphological characteristics of amorphous Ge2Sb2Te5 films after a single femtosecond laser pulse irradiation

The morphology of materials resulting from laser irradiation of the single-layer and the multilayer amorphous Ge2Sb2Te5 films using 120 fs pulses at 800 nm was observed using scanning electron microscopy and atomic force microscopy. For the single-layer film, the center of the irradiated spot is depression and the border is protrusion, however, for the multilayer film, the center morphology changes from a depression to a protrusion as the increase of the energy. The crystallization threshold fluence of the single-layer and the multilayer film is 22 and 23 mJ/cm(2), respectively. (c) 2005 Elsevier B.V. All rights reserved.

Self-formation of quasiperiodic void structure in CaF2 induced by femtosecond laser irradiation

We report the self-formation of quasiperiodic void structure with the length of several hundred micrometers inside the CaF2 crystal. The quasiperiodical voids along the propagation direction of the laser beam were formed spontaneously after the irradiation of a single femtosecond laser beam which was focused at a fixed point inside the crystal sample. The length of the void array varied with the focal depth beneath the sample surface. The possible mechanism of the self-formed void structure was discussed. (c) 2007 American Institute of Physics.

Upconversion luminescence of Ce3+ doped BK7 glass by femtosecond laser irradiation

Near-infrared to visible upconversion luminescence was observed in a multicomponent silicate (BK7) glass containing Ce3+ ions under focused infrared femtosecond laser irradiation. The emission spectra show that the upconversion luminescence comes from the 4f-5d transition of the Ce3+ ions. The relationship between the intensity of the Ce3+ emission and the pump power reveals that a three-photon absorption predominates in the conversion process from the near-infrared into the blue luminescence. The analysis of the upconversion mechanism suggests that the upconversion luminescence may come from a three-photon simultaneous absorption that leads to a population of the 5d level in which the characteristic luminescence occurs.

Three-photon-excited upconversion luminescence of niobium ions doped silicate glass by a femtosecond laser irradiation

We report on the bluish green upconversion luminescence of niobium ions doped silicate glass by a femtosecond laser irradiation. The dependence of the fluorescence intensity on the pump power density of laser indicates that the conversion of infrared irradiation to visible emission is dominated by three-photon excitation process. We suggest that the charge transfer from O-2-to Nb5+ can efficiently contribute to the bluish green emission. The results indicate that transition metal ions without d electrons play an important role in fields of optics when embedded into silicate glass matrix. (C) 2008 Optical Society of America.

Valence state change and refractive index change induced by femtosecond laser irradiation in Sm3+ doped fluoroaluminate glass

We report femtosecond laser induced valence state and refractive index change in transparent Sin(3+)-doped fluoroaluminate glass. The effect of annealing on the induced changes was studied and the thermal stability of these changes was discussed. The results show that the femtosecond laser induced valence state change is more stable than the induced refractive index change. The observed phenomenon could be applied to design the thermally erasable or stable storage medium. (c) 2007 Elsevier B.V. All rights reserved.