Abstract
Yttria–alumina–silica (YAS) glass microspheres doped with Nd3+ ions were excited with a 532 nm continuous laser in order to study the dependency of the wavelength of the whispering gallery mode (WGM) peaks on the temperature of the sample. This was possible due to a previous calibration of the 808 nm and 890 nm emission bands of the Nd:YAS glass sample for different temperatures using the fluorescence intensity ratio (FIR) technique. A maximum sensitivity of 15 × 10−6 K−1 and a temperature resolution limit of 0.2 K were obtained for the microsphere sensor. Moreover, laser emission at 1064 nm was observed by continuous pumping at 532 nm, and a power threshold of 100 mW was determined. Upconversion emissions of Nd3+ were also studied by exciting the sample at 808 nm.
Highlights
Active ions present luminescent properties that provide information regarding the characteristics of the host material lattice
The excitation was carried out in the center of the microsphere and the detection was located near its surface; sharp peaks appear superimposed on the typical Nd3+ emission spectrum due to the whispering gallery mode (WGM) resonances
The fluorescence intensity ratio (FIR) technique was employed on the 808 nm and 890 nm emissions of the YAS: Nd3+ doped bulk glass to obtain a temperature calibration with the intensity ratios
Summary
Active ions present luminescent properties that provide information regarding the characteristics of the host material lattice. Trivalent lanthanide ions are widely used, because they present various fluorescent transitions throughout the UV to mid-IR electromagnetic range and they can be employed in different dielectric media such as inorganic glasses and crystals, or even in intracellular medium [3,4]. Yttria–alumina–silica (YAS) glass microspheres have an interesting application for in situ cancer radiotherapy, in which they are used as carriers of yttrium isotope [5]. This is possible due to the excellent chemical durability of YAS glasses. The structure of YAS glasses make them favorable to be used as laser gain media for high concentrations of rare-earth dopant [6], and in all-fiber mode [7]
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