Towards a Supercontinuum Generation in an All-Fiberized Holmium-Doped ZBLAN Fiber Amplifier

A supercontinuum (SC) was first generated in a holmium-doped ZBLAN (ZrF
₄
-BaF
₂
-LaF
₃
-AlF
₃
-NaF) fiber amplifier (HDZFA) with a spectral coverage of 2.03-2.9 μm, then was further red-shifted to 3.7 μm by cascading a piece of passive ZBLAN fiber. The amplifier consisted of a 2050-nm pulsed fiber laser and a piece of holmium-doped ZBLAN fiber (HDZF), which was in-band pumped by a 1950-nm continuous wave thulium-doped fiber laser. A fusion splicing was achieved between passive silica fiber and the HDZF. The spectral and power characteristics of the amplifier were carefully investigated. The SC obtained in the amplifier showed a spectrum ranging from 2.03 to 2.9 μm with an output power of 248 mW and a maximal slope efficiency of 43.3%. The spectral broadening in the amplifier was halted by a strong absorption induced by an excited state absorption (ESA) of Ho
³⁺
in the range ~2.7-2.8 μm. An SC with 20-dB spectral coverage of 2.05-3.71 μm was finally obtained by cascading a piece of passive single-mode ZBLAN fiber after the amplifier, with the purpose of overcoming the ESA-induced loss of holmium ions. To the best of our knowledge, this research is the first demonstration of an SC generation in an HDZFA.