Given the ubiquity of glass formulations that are functionalized with silver compounds, the electronic interaction between isolated silver cations and the glass network deserves more attention. Here, we report the structural origin of the optical properties that result from silver doping in fluorophosphate (PF) and sulfophosphate (PS) glasses. To achieve this, solid-state nuclear magnetic resonance (NMR) spectroscopy and density functional theory (DFT) are combined with optical spectroscopic analysis and physical property measurements. Comparing the 31 P NMR, 27 Al 1d NMR, and 27 Al multi-quantum magic-angle spinning NMR of doped glasses and glasses with large amounts of Ag + added, we deduce silver's bonding preference in these mixed-anion aluminophosphate glasses. We show that such understanding provides an explanation for the large Stokes shift observed for Ag + in PF and PS glasses, which is related to absorption by the ionic Ag + ••• − O−P species and transfer of the excitation energy within more covalently bonded Ag 2 O-like clusters. This is corroborated by DFT calculations, which show that the Ag + ••• − O−P and Ag + ••• − O−S bonds in corresponding crystals are mostly ionic. The introduction of more silver ions into the crystal structure results in more covalent bonding between Ag + and the phosphate matrix.

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We propose and demonstrate a novel dual-frequency Brillouin fiber laser used for microwave generation. Based on this configuration, temperature sensing has been realized. The dual-frequency Brillouin lasing is generated independently from two pieces of fiber cascaded within one ring resonator. Microwave generation is acquired as the beat signal of the dual-frequency Brillouin fiber laser, with the beat frequency being linearly proportional to the temperature difference of the two fiber sections. In the experiment, the temperature coefficient of frequency shift is 1.015 ± 0.001 MHz °C−1. The temperature can be precisely measured by acquiring the frequency of the microwave generator, and this new configuration provides a promising application for temperature sensing.

Pressure-assisted melt filling (PAMF) of prefabricated micro-capillaries has been proven an effective way of fabricating hybrid optical fiber (HOF) from unusual combinations of materials. Here, we extend the applicability of PAMF to multi-anionic fluoride-sulfophosphate (FPS) glasses. FPS glasses provide extended transmission windows and high solubility for various transition metal (TM) and rare earth (RE) ion species. Using PAMF for fabricating FPS/silica HOFs can therefore act as a platform for a broad variety of optically active fiber devices. For the present demonstration purposes, we selected Cr 3+-and Mn 2+-doped FPS. For both glasses, we demonstrate how the spectral characteristics of the bulk material persist also in the HOF. Using a double-core fiber structure in which waveguiding is conducted in a primary GeO 2-SiO 2 core, mode coupling to the secondary FPS-filled core allows one to exploit the optical activity of the doped FPS glass even when the intrinsic optical loss is high.