The radiation resistance of rare-earth doped optical fibers is critical to applications in space-based environments such as laser radars, optical communications, and laser altimeters. Usually, doping various elements, such as aluminum (Al), phosphorus (P), and boron (B), is necessary to fine-tune the structural, electronic, and optical properties, but often results in degraded radiation resistance. Thus, achieving both excellent optical and radiation properties remain a challenge. Here, we theoretically investigate and compare the electronic, structural, and optical properties of [BPO4]° and [AlPO4]° units in silica glass. We prove that both [BPO4]° and [AlPO4]° units are stable in the SiO2 matrix. As the radiation resistance of [SiO4/2]° is excellent, inferring from the material's structure, the SiO2-BPO4 and SiO2-AlPO4 should have good radiation resistance. From the calculation, the SiO2-BPO4 is structurally and electronically similar to the SiO2-AlPO4. Importantly, the refractive index of SiO2-BPO4 is lower than SiO2-AlPO4, achieving refractive index tuning while maintaining its radiation resistance. Our results provide some guidance for the design of BPO4-based radiation-resistant active fibers.

We are grateful to Ballato et al. [Opt. Mater. Express 13, 2338 (2023)10.1364/OME.491887] for their comment on our recently published paper. The optical model and simulation of optical fiber materials are important to design new materials systems and to further improve the fiber laser performance. However, accurate calculation of the non-crystal fiber materials is still challenging, both from the methodology and from the needed calculating resources. The recently published paper [Opt. Mater. Express 13, 935 (2023)10.1364/OME.485138] has sparked interest, which gives us the opportunity to explain the difference between the modeled data and the well-established experimental results.