Two-photon absorption coefficient measurements in hydrogen-loaded germanosilicate optical fiber

Two-photon absorption (TPA) coefficients of hydrogen-loaded germanosilicate fiber are measured in the range of 440-500 nm with a tunable dye laser pum ped by a frequency-tripled e-switched YAG laser. The fiber is standard tele communication fiber loaded with 100-atm hydrogen. The measured TPA coeffici ents had a maximum value of 3 x 10(-4) cm/MW at 480 nm. The wavelength of 4 80 nm corresponds to twice the absorption wavelength of germanium-related o xygen-deficient centers (GODCs). The maximum TPA coefficient was two times that of non-loaded fibers. The mechanism of the increase by hydrogen loadin g is discussed with two different models, which involve parity change in el ectronic states of a GODC induced by a hydrogen molecule and absorption by combination of a hydrogen molecule and a GODC in the excited triplet state. (C) 1999 Elsevier Science B.V. All rights reserved.