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In this paper, we propose and demonstrate a ratiometric fluorescence temperature sensor based on an innovative silica-tellurite composite, which is capable of sensing dynamic human thermal information in real time. The temperature-sensitive upconversion fluorescence emission is generated by a miniaturized tellurite glass tip upon near-infrared excitation and collected by silica optical fiber channels. The ambient temperature information is demodulated via a fluorescence intensity ratio technique. This is the first time that Er3+/Yb3+ co-doped tellurite glass, which has fragile mechanical strength and a distinctive softening temperature, has been successfully extracted into a thin-walled silica tube using a negative pressure method. This provides a robust packaging for tellurite glass, allowing it for reliable thermometry in various complex scenarios. When applied to a human body, the sensitive tip located in the armpit and tongue fossa can continuously and accurately acquire the thermal information with a fast response time within 1 s. With its miniature size, robust packaging, intrinsic safety, fast response, and high reliability, the proposed ratiometric fluorescence sensor holds great potential for real-time human (in vivo/ex vivo) health assessment in clinical medicine, personalized healthcare, human-machine interfaces, and other intricate scenarios.

In this article, we propose and experimentally demonstrate a simple and low-cost fiber-optic sensor for temperature-independent ultraviolet (UV) detection. The sensor utilizes a photosensitive material, i.e., acrylic and hydrogenated epoxy resin, which is tightly wrapped around one end of a multimode optical fiber (MMF) and processed by light curing and heat curing. Upon absorbing UV radiation, the phosphor in the resin compound undergoes population inversion, resulting in the emission band around 480 nm, and the peak intensity of the emission band is positively correlated with the UV excitation intensity. The UV sensing characteristics of the sensor are experimentally investigated by tracking the photoluminescence peak intensity of the output spectrum, demonstrating a fast response of 0.1–0.2 s, high sensitivity of 315.78 (mW/cm2)−1, small absolute error within −0.28 to 0.42 mW/cm2, and good repeatability ( $R > $ 95%) and stability (RSD < 1.3%). In addition, the peak intensity is proved to be insensitive to temperature variation: as temperature varies from −20.5 °C to 56.3 °C, it shows only a small fluctuation, relative standard deviation (RSD) being less than 4.7%, indicating that the photothermal effects have negligible effect on the UV measurement accuracy. With the advantages of simple structure, easy fabrication, low cost, and excellent performance, the proposed sensor is expected to be used for reliable UV detection in practical applications.

We have successfully demonstrated high-resolution mid-infrared image transport by a multi-core fiber made of chalcogenide glasses. The fiber cores are arranged on a triangular lattice and adjacent cores have different core diameters to reduce cross-talk between them. We tested the resolution of the fiber using different fineness patterns and found that it can resolve better than 25 lp/mmat a wavelength of 9.3 μm. This demonstrates the potential of the fiber for high-resolution thermal imaging inside the human body.

We have numerically analyzed the cross-talk in triangular lattice fibers (TLFs) with three sublattices made of chalcogenide glasses for high-resolution mid-IR image transport. The TLFs are composed of cores with three different diameters arranged on triangular sublattices. We determined the core diameters and the core spacing to minimize the cross-talk and to densely align the cores. In addition, we demonstrated that the core density in TLFs with three sublattices is 2.3 times higher than without sublattices.