Published online by Cambridge University Press: 15 February 2011
Ge-associated defect centers induced by 5 eV (∼ 245 nm) photons of various intensities in Ge-doped silica were studied using electron spin resonance (ESR). We found that Ge E' centers observed in Bragg grating Ge-doped silica core fibers are induced and bleached by one- and two-photon absorption processes, respectively. The observation that Ge E's are the only paramagnetic centers induced by low intensity 5 eV photons supports the proposal that the Ge E' center is responsible for the photoinduced structures observed in both Bragg grating and second-harmonic-generation (SHG) fibers.