Broadband mid-infrared amplified spontaneous emission from Er/Dy co-doped fluoride fiber with a simple diode-pumped...

Er³⁺/Dy³⁺ co-doped double-clad ZBLAN optical fiber has been used to obtain amplified spontaneous emission (ASE) broadband light sources cladding-pumped by 980-nm multimode laser diode (LD) sources. It has been demonstrated that mid-infrared broadband emission extending from 2515 to 3735 nm was obtained by energy transfer between Er³⁺ and Dy³⁺. We experimentally investigated the optimum design of Er³⁺/Dy³⁺ co-doped ZBLAN fiber in terms of ion concentration, fiber length, pumping configuration, and pumping power. The ASE output power was more than 2.5 mW when the LD pump power was set at 5 W. To assess its potential for gas sensing applications, the fabricated ASE light source was used to successfully detect methane gas with concentrations at 1% and 5%. The simple and stable construction of our ASE light source is suitable for practical purposes.