Erbium-doped all-fiber green up-conversion amplified emission in silica-based fiber system

All-fiber 546-nm-wavelength green up-conversion amplified emission using an erbium-doped silica fiber at room temperature is demonstrated. Silica fiber is known for its high phonon energy and high nonradiative relaxation rate that prevents up-conversion lasing. In this study, we design an all-fiber system without using a free-space device to generate amplified emission. We use a 975nm high power diode pump laser, a 25-m-long double-cladding erbium-doped silica fiber, and two specially designed fiber-type end-face reflectors to generate 270 μW, 546nm green amplified emission. It was found that the high power density inside the double-cladding fiber makes up-conversion lasing possible by overcoming the population inversion.