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arXiv · 2611.08805

Laser-Direct-Written polymer WGM microring laser integrated on a fiber tip for refractive index sensing

Mobin Yaghoobi·Seyedeh Mahshad Hosseini·Leila Hajshahvaladi·Gholam-Mohammad Parsanasab·Mohammad Ismail Zibaii
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Abstract

Whispering-gallery-mode (WGM) microlasers are promising for refractometric sensing, but their practical implementation can be limited by the need for stable resonator-coupler alignment. Here, we demonstrate a Rhodamine B-doped polymer WGM microring laser directly fabricated on an optical-fiber tip, eliminating the external resonator-fiber coupling interface at the sensing head. Micro-droplet coating and UV laser direct writing are combined for fabrication, while finite-difference time-domain simulations guide the microring laser design. The microlasers operate in air and water with thresholds of 0.224 uJ and 0.458 uJ, respectively. Refractometric measurements in aqueous glucose solutions yield a bulk refractive index sensitivity of 364.95 nm/RIU and a detection limit of 2.47 x 10^(-4) RIU. Water-induced polymer changes and photobleaching are also investigated. This fiber-tip architecture provides a basis for probe-based refractometric sensing in environmental and biochemical applications.

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Mobin Yaghoobi, Seyedeh Mahshad Hosseini, Leila Hajshahvaladi, Gholam-Mohammad Parsanasab, Mohammad Ismail Zibaii. 2026-11-05. Laser-Direct-Written polymer WGM microring laser integrated on a fiber tip for refractive index sensing. https://arxiv.org/abs/2611.08805

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