Triple-wavelength lasing at 1.50 μm, 1.84 μm and 2.08 μm in a Ho3+/Tm3+ co-doped fluorozirconate glass microsphere

Simultaneous 1.50 μm, 1.84 μm and 2.08 μm laser emission is observed in a Ho3+/Tm3+ co-doped ZrF4–BaF2–YF3–AlF3 (ZBYA) fluoride glass microsphere when pumped using a 793 nm laser diode. The ZBYA fluoride glass microsphere was prepared using a CO2 laser heating method and whispering-gallery modes (WGM) were excited when the pump light was coupled using a tapered fiber. The introduction of Ho3+ ions reduced the population of the long-lived Tm3+:3F4 level and removed the 3H4→ 3F4 self-termination effect, resulting in the population of the Ho3+:5I7 level through a resonant energy transfer process. As the 793 nm laser pump power grows, lasing occurs initially at 2.08 μm, followed by the cascade outputs at 1.50 μm and 1.84 μm.