10-watt diode-pumped red Pr: ZBLAN double-clad fiber laser

Oxxius Pr:ZBLAN red fiber laser sources today

Published in Optics Express in 2025, this paper reports a 10-watt Pr:ZBLAN red fiber laser at 635 nm, a new power record for CW visible fluoride fiber lasers. Using a double-clad 0.8 mol% PrF₃-doped ZBLAN fiber and a high-power fiber-coupled 442 nm GaN laser diode module as the pump source, the laser delivers 9.1 W at 635 nm with 27.0% slope efficiency and single-mode output. In quasi-CW operation, output is further scaled to 10.32 W, crossing the 10-watt threshold for the first time in this class of visible fiber laser.

Beyond the headline power figure, this paper makes two important scientific contributions. First, it provides a systematic temperature-dependent spectroscopic study of Pr³⁺ ions in ZBLAN glass, establishing the material parameters needed to model and predict power scaling behavior. Second, it identifies four-wave mixing as the mechanism responsible for spectral broadening at high intracavity powers and demonstrates that this broadening follows a square root law, providing a predictive framework for future system design.

Why this result matters for instrumentation

A 10-watt single-mode source at 635 nm, pumped by a compact GaN diode module, opens new possibilities for applications that have historically required bulky and expensive dye lasers or DPSS systems: high-throughput flow cytometry, super-resolution microscopy, fluorescence correlation spectroscopy, and optogenetics with red-shifted opsins. The 442 nm GaN pump module used in this experiment is representative of Oxxius’s High-Power Diode Modules, which provide the beam brightness and power stability required to drive this class of visible ZBLAN fiber lasers to watt-class output.

Abstract

We report on a continuous-wave (CW) praseodymium fluoride fiber laser delivering 10-watt level output power in the red spectral range. It employs a double-clad 0.8 mol% PrF₃-doped ZBLAN fiber as a gain medium and a high-power fiber-coupled 442-nm GaN laser diode module as a pump source. The CW Pr-laser delivers 9.1 W at 635 nm with a slope efficiency of 27.0% (versus launched pump power), a laser threshold of 1.32 W, and a single-mode output. In the quasi-continuous-wave regime, its output is further scaled to 10.32 W. The spectrum broadening in this laser is explained by four-wave mixing and is well described by the square root law. This result represents a new milestone in developing visible fluoride fiber lasers. The temperature-dependent spectroscopy of Pr³⁺ ions in the ZBLAN glass is studied, and the limits for further power scaling of red fluoride fiber lasers are discussed.