High performance visible generation of Ho3+-doped all-fiber lasers

Direct generation of visible frequency from a compact all-fiber laser while preserving high output characteristics has been a subject of research in laser technology. We investigated the high output performance of all-fiber lasers based on Ho3+-doped ZBLAN fluoride glass fiber especially operating in the deep-red band by pumping at 640 nm. Remarkably, we achieved a maximum continuous-wave output power of 271 mW at 750 nm with a slope efficiency of 45.1%, which represents, to our knowledge, the highest direct output power recorded in an all-fiber laser with a core diameter of less than 10 mu m in the deep-red band. Additionally, we successfully developed a 1.2 mu m all-fiber laser pumped by a 640 nm laser. We extensively investigated the correlation between these two-laser generation processes and their performances at 750 nm and 1.2 mu m wavelengths. By increasing the pumping rate, we observed an efficient recycling of population through a highly excited state absorption process, which effectively returned the population to the upper laser level of the deep-red transition. Moreover, we determined the optimized conditions for such lasers, identified the processes responsible for populating the excited state energy levels, and established the corresponding spectroscopic parameters. (c) 2023 Chinese Laser Press