Optical amplification ranging from 1600 to over 1680 nm in thulium-doped fluorotellurite glass fibers with a terbium-doped cladding

We demonstrated optical amplification ranging from 1600 to over 1680 nm in Tm3+-doped fluorotellurite fibers (FTFs) with a Tb3+-doped cladding by using a 1212 nm fiber laser as the pump source. The FTFs based on TeO2-BaF2- Y2O3 glasses were fabricated by using a rod-in-tube method. The doping concentration of Tm3+ ions in the core was about 4000 ppm and that of Tb3+ ions in the fiber cladding was about 10,000 ppm. By introducing the Tb3+ ions into the cladding, the emission in the long-wavelength region (>1750 nm) originating from the transition F-3(4)-> H-3(6) of Tm3+ ions was suppressed efficiently by broadband absorption (1700-2100 nm) originating from the transitions F-7(6)-> F-7(0,1,2) of the Tb3+ ions in the cladding. As a result, a positive net gain ranging from 1600 to over 1680 nm was achieved in a 1.5 m long Tm3+-doped FTF as the launched power of the 1212 nm laser was about 3 W. The gain value at 1675 nm was about 19.7 dB for an input signal power of similar to 0 dBm (or 1 mW). The gain was gradually reduced for shorter wavelengths, but it was still above 10 dB at similar to 1644 nm. Our results show that Tm3+-doped FTFs with a Tb3+-doped cladding are promising gain media for constructing fiber amplifiers and lasers in the wavelength region of 1600-1700 nm. (c) 2025 Optica Publishing Group. All rights, including for text and data mining (TDM), Artificial Intelligence (AI) training, and similar technologies, are reserved.