Yellow whispering-gallery-mode lasing from amorphous fluoride microspheres

Abhishek Sureshkumar; Jonathan Demaimay; Georges Perin; Christelle Velly; Héléne Ollivier; Yannick Dumeige; Alain Braud; Patrice Camy; Stéphane Trebaol; Pavel Loiko

arXiv · 2604.08269

Yellow whispering-gallery-mode lasing from amorphous fluoride microspheres

Abhishek Sureshkumar·Jonathan Demaimay·Georges Perin·Christelle Velly·Héléne Ollivier·Yannick Dumeige·Alain Braud·Patrice Camy·Stéphane Trebaol·Pavel Loiko

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Abstract

Compact, low-noise coherent light sources in the visible remain challenging due to limited gain platforms and inefficient pumping. We report a new route to visible microlasing based on direct, one-photon blue pumping and an amorphous fluoride gain material platform. Dysprosium doped fluoride microspheres are fabricated via plasma-torch-induced, pressureless amorphization of single crystals, enabling compositions beyond conventional glass-forming limits while ensuring ultrasmooth morphology, low phonon energy, and homogeneous dopant distribution. We demonstrate the first fiber-coupled whispering-gallery-mode lasing from an amorphous fluoride microsphere in the yellow (573 nm), with an ultralow threshold of $190 \mu$W despite spin-forbidden Dy$^{3+}$ transitions. Lasing is evidenced by characteristic light-light curve indicating a low spontaneous emission factor, narrow-linewidth emission, and relaxation oscillations yielding a loaded quality factor of $Q = 3.5 \times 10^6$. This platform is readily extendable to other rare-earth emitters, enabling entire visible spectral coverage beyond the limitations of upconversion pumping, with prospects for color-tunable and white-light emission. Finally, fiber-based amplification of the WGM signal demonstrates a pathway toward compact, fiber-integrated visible microlasers with controllable noise and linewidth.

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Abhishek Sureshkumar, Jonathan Demaimay, Georges Perin, Christelle Velly, Héléne Ollivier, Yannick Dumeige, Alain Braud, Patrice Camy, Stéphane Trebaol, Pavel Loiko. 2026-04-09. Yellow whispering-gallery-mode lasing from amorphous fluoride microspheres. https://arxiv.org/abs/2604.08269

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