Correlation of defect centers with photoinduced second-harmonic generation in Er- and Sm-doped aluminosilicate fibers.

The spectral dependence of photoinduced optical losses after chi((2)) writing have been obtained in Sm- and Er-doped fibers. The results show that Sm(2+) and Er(2+) can be a source of photoelectrons during fiber preparation.

Oscillator strengths of UV absorption and luminescence for oxygen-deficient centers in germanosilicate fibers.

The time-resolved measurements of triplet and singlet luminescence from germanium oxygen-deficient centers (GODC's) in germanosilicate fibers excited by short UV laser pulses are used to determine the cross section of UV absorption of GODC's at lambda = 248 nm (sigma = 5 x 10(-18) cm(2)), the oscillator strength of UV absorption (f(abs) = 0.027), and UV luminescence (f(lum) = 0.031). The basis for these measurements is the direct luminescence detection of lifetimes of electronically excited states of GODC's, the saturation of triplet luminescence signals, and the analysis of the rate equations that govern the laser photoexcitation and relaxation processes in GODC's.

Photoinduced second-harmonic generation in fibers doped with rare-earth ions.

Photoinduced second-harmonic generation in silica fibers doped with Er(3+), Sm(3+), and Tb(3+) has been investigated. Er(3+)-doped fibers have been found to tune a chi((2)) grating easily to the mode structure of the laser radiation, whereas Sm(3+)-doped fibers have been found to possess the greatest resistance to chi((2)) grating erasure by radiation at 532 nm. From the beginning of the preparation processes, the third harmonic at 355 nm is registered in all the fibers.