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We studied the photoluminescence (PL) from black silicon that was fabricated using an 800 nm, 250 kHz femtosecond laser in air. By changing the scan velocity and the fluence of the femtosecond laser, the formation of the PL band between the orange (600 nm) and red bands (near 680 nm) could be controlled. The red band PL from the photoinduced microstructures on the black silicon was observed even without annealing due to the thermal accumulation of high-repetition rate femtosecond laser pulses. The orange band PL was easily quenched under 532 nm cw laser irradiation, whereas the red band PL was more stable; this can be attributed to 'defect luminescence' and 'quantum confinement', respectively. [ABSTRACT FROM AUTHOR]

Here, the authors demonstrate a unique technique to form dense dislocations locally inside a single crystal with a rocksalt-type structure using femtosecond laser irradiation for the first time, to our knowledge. Cross-shaped patterns of micrometer size, originating from densely introduced dislocations, are formed around the focal point. The authors controlled three-dimensional propagation of dislocations by adjusting the pulse energy of femtosecond laser and numerical aperture of objective lens. [ABSTRACT FROM AUTHOR]

We report the observation of space-selective oxidation of Mn[sup 2+] to Mn[sup 3+] in a transparent and colorless Mn and Fe ions codoped silicate glass at room temperature by using an 800-nm-femtosecond laser. Difference absorption spectrum of the glass after and before the irradiation of the focused infrared femtosecond pulsed laser showed that a portion of Mn[sup 2+] ions near the focused part of the laser beam inside the glass were oxidized to Mn[sup 3+] ions after the laser irradiation. Mn[sup 3+] ions were stable at the temperatures below 300 °C. It is suggested that Mn[sup 2+] ions act as hole trapping centers while Fe[sup 3+] ions as well as active sites in the glass matrix act as electron trapping centers. A promising application was demonstrated for the fabrication of three-dimensional colored image inside a transparent material. © 2001 American Institute of Physics. [ABSTRACT FROM AUTHOR]