1.55-μm-light absorption induced by pulsed-X-ray radiation in pure-silica-core fiber: Effects of light power and temperature

Abstract

Pure-silica-core F-doped-silica cladding fiber (“pure silica fiber”, PSF) is subjected to eight pulsed-X-ray irradiations (pulse duration of 20 ns, mean photon energy of ~5 MeV). In each pulse, the probe light power at the wavelength λ = 1.55 μm is either 10 mW, or 33–40 μW, the irradiation temperature being also varied among pulses from −80 to +85 °C. Post-pulse decay of radiation-induced absorption (RIA) in the PSF is measured at λ = 1.55 μm in the subsecond scale and, in four typical cases, is approximated in the framework of the second-order-kinetic model to separate RIA due to inherent and strain-assisted self-trapped holes (STHs). Post-pulse RIA time evolution is found to be qualitatively different at the different probe light powers. At the 33–40-μW power, RIA is virtually wholly described by inherent STHs with some admixture of strain-assisted ones only at the highest temperature of +85 °C. At the 10-mW power, the RIA temporal run is found to be composed of two clear-cut successive domains due to inherent and strain-assisted STHs regardless of temperature. An enhanced probe light power and enhanced temperature are found to have a similar influence on the STHs of the two classes: they partly suppress the inherent STHs and promote the occurrence of the strain-assisted ones. A physical mechanism is proposed for the latter effect. Basic principles for selecting the best-suited probe light power at λ = 1.55 μm with regard to the application specifications are proposed.