Effect of P/Al ratio on the X-ray induced darkening in Dy-doped silica glasses at visible wavelengths

In this work, we study the mechanisms of X-ray induced darkening in the Dy/Al/P co-doped silica glasses at visible wavelengths and explore the role of P/Al ratio played in the enhancement of irradiation resistance. The absorption, emission spectra and lifetime, Raman, and electron paramagnetic resonance spectra of pristine and irradiated Dy-silica glasses as a function of P/Al ratio were measured and analyzed. The Si-related defects (Si-E ' and non-bridge oxygen hole center), Al-related defects (Al-E ' and Al-related oxygen hole center), P-related defects (P-OHC and P-2), and Dy2+ ions were studied and analyzed. Results demonstrate that increasing P/Al is efficient to suppress the photodarkening in Dy-silica glasses at visible wavelengths. Results imply that Dy-silica glasses with P/Al > 1 may be a promising candidate for efficient visible fiber lasers operated at around 575 nm wavelength.