Strong high-quality fiber Bragg gratings with photoinduced refractive-index modulation of more than 10-(3) were written in a Corning SMF-28 fiber, a P(2)O5-doped-core fiber and a pure-silica-core fluorine-doped-cladding fiber by third-harmonic radiation (267 nm, 150 fs and 1.2-1.8x1011 W/cm(2)) of a femtosecond Ti:sapphire laser using a phase mask. We compare the 267-nm photosensitivity responses with the results of irradiation by 193-nm ArF and 157-nm F(2) excimer lasers. The dependence of the refractive-index change on the exposure dose and the annealing characteristics of the fabricated gratings are typical for Type-I UV-written fiber gratings.

The authors have studied the influence of chirped laser pulses on the coherent phonon generation in single crystal Te. They have shown that the pulse chirp affects the amplitude of coherent phonons with A 1 symmetry in the case of intense excitation only. By varying the chirp of an intense exciting pulse, the authors demonstrated that negatively chirped pulses are almost twice more effective in the creation of lattice coherence than positively chirped pulses.

Femtosecond laser spectroscopy is used to study the mechanisms of excitation and energy relaxation of charge carriers in a C 6 0 film on a 100-fs scale. The studies cover the laser intensity dependence of absorption. The rise of absorption, peaked at zero delay times, is shown to be replaced by electronic-vibrational relaxation with times TI -1 ps and 7 2 -30 ps. Relaxation mechanisms corresponding to these times are discussed, along with the possible role in kinetics of a spontaneous symmetry breaking of the excited state of C60.