Watt-level visible laser in double-clad Pr3+-doped fluoride fiber pumped by a GaN diode
Oxxius GaN-pumped visible fiber laser sources today
Published in Optics Letters in 2020, this paper demonstrates a watt-level Pr:ZBLAN red fiber laser at 634.5 nm delivering 1.07 W of output power with 20.7% slope efficiency — pumped by a multimode 443 nm GaN diode. The double-clad ZBLAN fiber architecture, with a 5.5 µm single-mode core and a D-shaped inner cladding optimized for efficient pump coupling, enables high-brightness red emission that would otherwise require a dye laser or a complex DPSS system.
This result is significant on two levels. First, it demonstrates that watt-class visible output is achievable from a compact, all-fiber geometry using a low-cost GaN diode as the sole pump source — a key step toward practical, instrument-integrable visible fiber lasers. Second, the 634.5 nm wavelength is directly relevant to life science applications: it falls within the optimal excitation range for several deep-red fluorophores including Cy5, Alexa Fluor 647, and related probes widely used in single-molecule imaging, super-resolution microscopy, and flow cytometry.
From pump to performance: the role of Oxxius GaN diodes
The 443 nm GaN pump diode used in this experiment is representative of the high-brightness blue diode modules that Oxxius develops and manufactures for exactly this class of application — pumping Pr³⁺-doped fluoride fiber lasers across their visible emission lines at 521 nm, 604 nm, 635 nm, 698 nm, and 717 nm. The LBX-443 and related high-power diode modules in the Oxxius product line provide the beam quality, power stability, and spectral control required to reach threshold efficiently in these demanding fiber laser geometries.
Abstract
We report on a red praseodymium fiber laser delivering 1.07 W at 634.5 nm with a slope efficiency of 20.7% (versus the incident pump), a laser threshold of 0.55 W, and a single-mode output ( in the quasi-continuous-wave regime. It is based on a 0.6 mol.% -doped ZBLAN double-clad fiber with a 5.5 µm core, a double D-shaped (diameters, 115/125 µm) inner cladding, and a length of 5.0 m. The fiber is pumped by a multimode 443 nm GaN diode. The laser design is optimized using a numerical model. The proposed concept is suitable for the development of diode-pumped high brightness watt-level visible praseodymium fiber lasers.