Photodarkening in Pr 3+ -doped silicate glasses and fibers

Visible laser of Pr3+ ions doped in fluoride glass fibers has found numerous applications in display techniques, visible light communication and scientific research. Unfortunately, the poor mechanical strength, degraded chemical stability and high cost limit the further development of fluoride glasses in practice. Instead, oxide glass is good host candidate for fiber lasers due to its advantages of mature processing technique, stable chemical properties, high mechanical strength and low cost. But it is difficult to achieve laser output at visible wavelengths in Pr3+ doped oxide glass fiber because of photodarkening after exposure to 488 nm laser. In this work, we study such photodarkening effect and relevant mechanisms in Pr3+ doped silicate glasses and fibers by using X-ray and 488 nm laser as irradiation sources, respectively. Results indicate that due to relatively low energy of Pr3+: 4f5d, electrons of Pr3+ ions will be trapped to form defect (trapped hole center) through excited state absorption under exposure to both 488 nm laser and X-ray radiation.