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.

Time response of optical switching properties of Sb thin films under focused laser pulses

The time response of optical switching properties of Sb thin films under focused laser pulses is investigated. The results show that the response course can be divided into onset, opening, and closing stages. Formulas for their lengths are given. The onset and opening times decrease with increasing pumping light power density. The closing time is about 150 ns. For optical memory, if the power density of the readout and recording lasers changes from 5 x 10(9) to 15 x 10(9) W/m(2), the onset time changes from 2.5 to 0.30 mus, and the opening time is on the nanosecond scale. (C) 2003 Society of Photo-Optical Instrumentation Engineers.

Laser-induced changes on the complex refractive indices of phase-change thin film

The refractive indices of crystalline phase-change films are usually obtained by thermal-induced crystallization. However, this is not accurate, because the crystallization of phase-change film in rewritable optical disks is laser induced. In this study, we use the initializer to crystallize the phase-change films. The dependence of the refractive index n and the extinction coefficient k of the phase-change films on the initialization conditions are studied. Remarkable changes of the refractive indices (especially k) are found when the initialization laser power density is 6.63 mW/mum(2) and the initialization velocity is 4.0 m/s. At the same time, the structure changes of the phase-change films are also studied. This dependence is explained by the structure change of the films. These results are significant in improving the accuracy of optical design and the thermal simulation of phase-change optical disks, as well as in the study of phase-change optical disks at shorter wavelengths. (C) 2003 Society of Photo-Optical Instrumentation Engineers.

Crystallization of amorphous Ge2Sb2Te5 films induced by a single femtosecond laser pulse

Crystallization is achieved in amorphous Ge2Sb2Te5 films upon irradiation with a single femtosecond laser pulse. Transmission electron microscopy images evidence the morphology of the crystallized spot which depends on the fluence of the ferntosecond laser pulse. Fine crystalline grains are induced at low fluence, and the coarse crystalline grains are obtained at high fluence. At the damage fluence, ablation of the films occurs. (C) 2004 Elsevier Ltd. All rights reserved.

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.

Femtosecond laser-induced crystallization in amorphous Ge2Sb2Te5 films

Crystallization in amorphous Ge2Sb2Te5 films by irradiation with femtosecond laser was investigated. The reflectivity and X-ray diffraction measurements confirmed that the crystalline state has been achieved in amorphous Ge2Sb2Te5 films under the irradiation of fermosecond laser with an average power of 65 mW at a frequency of 1000 Hz and a pulsed width of 120 fs. The surface morphology before and after femtosecond laser irradiation was studied by scanning electron microscope; results showed that the surface of films with irradiation of femtosecond laser was composed of some the crystallized micro-region. (C) 2004 Elsevier B.V. All rights reserved.

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.

Ultrafast optical Kerr effect in amorphous Ge10As40S30Se20 film induced by ultrashort laser pulses

The results of the femtosecond optical heterodyne detection of optical Kerr effect at 805 am with the 80 fs ultrafast pulses in amorphous Ge10As40S30Se20 film is reported in this Letter. The film shows an optical nonlinear response of 200 fs under ultrafast 80 fs-pulse excitation, and the values of real and imaginary parts of nonlinear susceptibility chi((3)) were 9.0 x 10(-12) esu and -4.0 x 10(-12) esu respectively. The large third-order nonlinearity and ultrafast response are attributed to the ultrafast distortion of the electron orbits surrounding the average positions of the nucleus of Ge, As, S and Se atoms. This Ge10As40S30Se20 chalcogenide glass would be expected as a promising material for optical switching technique.