Most of the time, when we think about lasers and light, we imagine them heating things up—not cooling them down. But a recent study shows that certain optical fibers can cool when illuminated with the right kind of laser light. This effect, called anti-Stokes fluorescence cooling, could someday help control heat in high-power lasers and advanced photonic devices.
What Is Anti-Stokes Fluorescence?
When light hits a material, it usually excites electrons, which then release energy as heat. This is known as a Stokes process. Anti-Stokes processes work in reverse. Here, the material absorbs a photon with slightly less energy than usual and then emits a photon with more energy. The extra energy comes from the material’s heat, meaning the material actually loses thermal energy. In other words, it cools down.
For this to happen efficiently, the material has to have very low impurities and lose as little energy as possible through non-radiative processes—ways electrons can lose energy as heat instead of light.
What the Researchers Did
The researchers, including MSE’s Drs. John Ballato and Wade Hawkins, tested seven commercially available silica fibers that were doped with ytterbium (Yb). They shined a laser at about 1040 nm into each fiber and carefully measured the temperature changes. Surprisingly, some of these standard fibers cooled slightly—up to about 0.085°C below room temperature.
This is not a huge amount of cooling, and it is less than what has been seen in specially engineered fibers. But the key point is that these fibers were commercial products, not custom laboratory materials.
Why This Matters
Demonstrating cooling in widely available fibers makes laser-based cooling more practical. If cooling can be built directly into the fibers used in high-power laser systems, those systems could become more stable, efficient, and compact. The technique could also help create “athermal” lasers—lasers that generate little or no excess heat.
What’s Next?
To improve cooling, researchers need fibers with fewer impurities, higher ytterbium concentration without quenching effects, and lower background absorption. If these challenges are solved, laser-driven cooling could eventually become a built-in feature of optical devices.
Read the article here.
Citation: Chen, C.; Balliu, E.; Meehan, B.; Hawkins, T. W.; Ballato, J.; Dragic, P. D.; Boilard, T.; Bernier, M.; Digonnet, M. J. F. Observation of anti-Stokes-fluorescence cooling in commercial Yb-doped silica fibers. Appl. Phys. Lett. 2025, 127
