The growth of a two-photon-resonant photoinduced second-harmonic signal at 660 nm in Er3+-doped GeO2-Al2O3-SiO2 single-mode optical fibers pumped by a Nd:YAG laser at 1.319 µm is reported. Defect states in the band gap are optically excited through a resonant two-photon absorption process connecting the 4I15/2-4F9/2 energy levels of the erbium ions present in the fiber core. As a result a periodic X(2) grating is formed, and efficient second-harmonic generation takes place. For erbium-free GeO2-doped silica test fibers no second-harmonic signal has been detected, even after hours of seeded preparation process.
© 1994 Optical Society of America
J. Miguel Hickmann, E. A. Gouveia, A. S. Gouveia-Neto, D. C. Dini, and S. Celaschi, "Two-photon-resonant photoinduced second-harmonic generation in Er3+-doped germano-aluminosilicate optical fibers pumped at 1.319 µm," Opt. Lett. 19, 1726-1728 (1994)