Owing to rare earth (RE) doped active fibers are crucial in space-based applications, such as space laser communication, laser radar, and space waste disposal. However, the space radiation environment can lead to a sharp increase in the optical loss of RE doped active fibers, and a sharp decrease in the output laser slope efficiency or gain performance. Therefore, it is very important to improve the radiation-resistance property of RE doped silica fiber.

Recently, a research team from Shanghai Institute of Optics and Fine Mechanics of the Chinese Academy of Sciences, has prepared a radiation-resistant Er-doped silica glass and optical fiber by co-doping with Ge ions and investigated the related radiation resistance mechanism. The research results have been published in Optical Materials Express 3 June, 2021. It was selected by the Editor-in-Chief as Editor's pick (Editor's Picks serve to highlight articles with excellent (Editor's Picks serve to highlight articles with excellent scientific quality and are representative of the work taking place in a specific field).

In this report, researchers briefly introduce the space radiation environment the application requirements, and the challenges of active fibers in space. On the one hand, they systematically introduced the latest research progress of radiation-resistant active fibers in SIOM; on the other hand, they suggested the potential issues that require further investigation.

The research team prepared Ge ion co-doping silica glasses and fibers, the radiation induced color centers were identified by induced absorption and electron paramagnetic resonance spectroscopy. The researchers proposed the formation and conversion process of Al and Ge related color centers and the radiation-resistance mechanism of Ge co-doping. The results of online X-ray radiation experiments show that Ge co-doping can significantly improve the gain performance of Er-doped fiber amplifier (EDFA) after radiation.

This work provides a necessary reference for the optimization and design of radiation hardening Er-doped silica fiber core glass composition for future space EDFA applications.

The research was supported by the National Key R&D Program of China, the National Natural Science Foundation of China, and the Shanghai Yangfan Program.

Model for the formation of the Al- and Ge-related defects caused by radiation. (Image by SIOM)