20 μm Nd^3+/Ho^3+-doped tungsten tellurite fiber laser

Abstract

Tellurite glass has emerged as a promising ~2.0 μm laser material owing to its excellent features of supporting efficient mid-infrared emission and easy fiber-pulling over the commonly investigated glasses. In this paper, we report an efficient ~2.0 μm laser output from a new-type of Nd3+/Ho3+ co-doped tungsten tellurite fiber laser by using an ultra-short length fiber of 5 cm upon a 795 nm laser diode. The tellurite fibers have been fabricated by a suction technique with the core and cladding diameters of 32 and 125 μm, respectively. The propagation loss of the fiber is measured to be 4.44 dB/m at 1310 nm by using the cutback method. The large energy transfer coefficient from Nd3+ to Ho3+ (3.8 × 10−40 cm6·s–1) and high gain coefficient of Ho3+: 5I7 → 5I8 transition (1.2 cm–1) have confirmed the success of using Nd3+ as sensitizer to realize the ~2.0 μm laser emission of Ho3+. The maximum output power of the laser is obtained to be 12 mW at a center wavelength of 2052 nm with a slope efficiency of 11.2%. The laser threshold is as low as 38 mW, which is around one order of magnitude lower than the previously reported Tm3+/Yb3+ doped tellurite fiber lasers with the similar pump scheme and fiber geometry. The results indicate that the Nd3+/Ho3+ co-doped tungsten tellurite glass fiber laser is a promising laser medium candidate for achieving the ultra-compact and efficient ~2.0 μm laser.