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 P2), 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. [ABSTRACT FROM AUTHOR]