Watt-Level High-Efficiency Deep-Red Ho3+:ZBLAN Fiber Laser

Abstract

To date, Ho <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped fluoride fibers have been investigated as a viable route for deep-red fiber lasers. However, high output performance deep-red fiber lasers around 750 nm have been proven challenging to achieve due to limitations in both the excitation source and pumping mechanism. In this study, we use a home-made 640 nm pump source to develop a deep-red laser with a high pumping rate, and obtain a compact watt-level high efficiency deep-red laser output. Population inversion is achieved by strong excited state absorption in a Ho <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped ZBLAN fiber. We realize a maximum 1.46 W deep-red fiber laser operating at 752.6 nm, and its slope efficiency is as high as 53%. The improved rate equations are used to describe the quasi-four-level system, and the experimental results agree well with the simulations. Moreover, with the development of blazed grating, we demonstrate a tunable deep-red fiber laser with a tuning range of 13.7 nm, from 746.5 to 760.2 nm, which is the widest tuning range of Ho <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> -doped fiber laser at deep-red wavelengths.