Efficient yellow Dy: ZBLAN fiber laser with high-brightness diode-pumping at 450 nm

Oxxius yellow laser sources today

Published in EPJ Web of Conferences in 2024, this paper reports a Dy:ZBLAN yellow fiber laser at 575 nm achieving 109 mW of CW output with a record-high overall optical efficiency of 13.9% — pumped by two 450 nm GaN blue laser diodes in a single-clad geometry. The 19.6% slope efficiency and low threshold of 218 mW represent state-of-the-art performance for dysprosium-doped fluoride fiber lasers, enabled by the high brightness of the GaN pump diodes used.

The 575 nm yellow wavelength is one of the hardest to reach with compact solid-state laser sources. It falls in a spectral gap between the standard DPSS lines at 561 nm and 589 nm (sodium), where neither frequency-doubled Nd:YAG nor conventional diode lasers can emit directly. Dy:ZBLAN fiber lasers address this gap by exploiting the ⁴F₉/₂ → ⁶H₁₃/₂ transition of dysprosium, which produces broadband emission centered around 575 nm when pumped in the blue. The excellent beam quality demonstrated here (M² ~1.5) makes this source suitable for free-space coupling into microscopy and spectroscopy instruments.

The role of high-brightness GaN pump diodes

The performance demonstrated in this paper is directly enabled by the high spatial brightness of the 450 nm GaN pump diodes — a critical parameter for single-clad fiber laser geometries where pump coupling efficiency into a small core determines both threshold and slope efficiency. Oxxius develops and manufactures high-brightness blue diode modules in this wavelength range, including the LBX-450 series, which provides the beam quality and power stability required to drive this class of visible ZBLAN fiber lasers efficiently.

Abstract

We report on a low-threshold efficient yellow Dy-fiber laser with good beam quality featuring high-brightness pumping. It employs a single-clad 0.2 mol% Dy:ZBLAN fiber pumped by two 450-nm blue GaN laser diodes. The continuous-wave Dy-fiber laser delivers a maximum output power of 109 mW at 575 nm with a laser threshold of 218 mW, a slope efficiency of 19.6%, and beam quality factors M²_x,y∼ 1.5. The overall optical efficiency versus incident pump power is 13.9%, being record-high, to the best of our knowledge, for this type of laser. The laser performance is simulated based on the spectroscopic data, being in good agreement with the experiment.