Defect Centers in the Silicate Glasses: Basics, Implications, and Mitigation Strategies for the Generation of Visible Light

Abstract Generating and transporting high optical power levels and shorter wavelengths from lasers using silicate glass fiber is desirable for many practical reasons. Silicate glasses do not have a uniform molecular structure, however, which means that the transparency at shorter wavelengths of the fiber is usually limited by the creation of induced absorption from holes and electrons localized in the region close to point defects. This is a particular problem for fiber lasers because of the high intensities associated with the resonance condition and core guidance and, because of the energy level structures of the rare earth ions that are doped into the fiber. Pumping rare earth ions creates efficient pathways for energy transfer from the pump to the host energizing the intrinsic point defects to create color centers. The induced absorption is wavelength dependent and grows stronger with power and exposure time. In this timely review, the fundamentals of color center formation as it relates to the pure, modified, and doped silicate glasses is re‐examined. The primary aim of this review is to extract the key aspects of glass defect science from the vast literature and relate it to the modern problems of high‐power visible light generation and transportation in silicate glass optical fiber.