Observation of radiation-induced absorption of self-trapped holes in Ge-doped silica fiber in near infrared range at reduced temperature

摘要

Short-lived radiation-induced absorption (RIA) of light peaking at wavelengths 1700 nm has been revealed in a gamma-irradiated (= 1 kGy) heavily (50 mol% GeO2) Ge-doped silica optical fiber (Ge-doped fiber) at low temperatures (= -30 degrees C). This RIA is found to closely resemble in properties the known RIA due to inherent self-trapped holes (STHs) in undoped-silica-core optical fibers (same spectral range, low thermostability, nonmonotonic evolution with dose, shift of the peak wavelength with temperature, Arrhenius dependence on temperature, growth of the activation energy in the course of irradiation and recovery). The STH-like RIA is found not to occur in more lightly Ge-doped fibers and in a Bi-codoped Ge-doped fiber with the same (50 mol%) GeO2 concentration. A possible microscopic structure of the STH in heavily Ge-doped fibers is discussed.