Silver plasmon resonance effects in AgPO3/silica photonic bandgap fiber

Towards a Glass New World: The Role of Ion-Exchange in Modern Technology

Glasses, in their different forms and compositions, have special properties that are not found in other materials. The combination of transparency and hardness at room temperature, combined with a suitable mechanical strength and excellent chemical durability, makes this material indispensable for many applications in different technological fields (as, for instance, the optical fibres which constitute the physical carrier for high-speed communication networks as well as the transducer for a wide range of high-performance sensors). For its part, ion-exchange from molten salts is a well-established, low-cost technology capable of modifying the chemical-physical properties of glass. The synergy between ion-exchange and glass has always been a happy marriage, from its ancient historical background for the realisation of wonderful artefacts, to the discovery of novel and fascinating solutions for modern technology (e.g., integrated optics). Getting inspiration from some hot topics related to the application context of this technique, the goal of this critical review is to show how ion-exchange in glass, far from being an obsolete process, can still have an important impact in everyday life, both at a merely commercial level as well as at that of frontier research.

Highly luminescent and ultrastable cesium lead bromide perovskite patterns generated in phosphate glass matrices

Owing to their exceptional optoelectronic properties, all-inorganic lead halide perovskites offer enormous potential for next generation photonic, light-emitting, and optoelectronic devices. However, their usage is significantly limited by their poor stability upon moisture exposure and lead toxicity issues. Moreover, many of the aforementioned applications rely on the development of confined perovskite patterns of various shapes and periodicities. Here we report a simple and low-temperature method enabling the controlled incorporation of photoluminescent all-inorganic metal halide PNCs into a silver phosphate glass (AgPO3) matrix which is transparent in most of the visible range. The developed fabrication protocol is based on a simple melting encapsulation process in which pre-synthesized perovskite crystals are inserted in the glass matrix, following the initial glass quenching. Using this novel approach, two types of composite perovskite glasses are prepared, one that hosts perovskite isles and the second in which a thin perovskite layer is embedded beneath the glass surface. Both types of composite glasses exhibit remarkable photoluminescence stability when compared to the ambient air-exposed perovskite crystals. More importantly, by means of a simple and fast cw-laser processing technique, we demonstrate the development of encapsulated dotted perovskite micropatterns within the composite perovskite glass. The ability of the proposed system to resolve stability and lead toxicity issues, coupled with the facile formation of highly luminescent perovskite patterns pave the way towards the broad exploitation of perovskite crystals in photonic applications.

Guiding light in a water core all-solid cladding photonic band gap fiber - an innovative platform for fiber-based optofluidics

We present a single-channel photonic band gap fiber design allowing for guiding light inside a water core, which is surrounded by solid microstructured cladding, consisting of an array of high refractive index strands in silica. We address all relevant properties and show that the microstructure substantially reduces loss. We also introduce a ray reflection model, matching numerical modelling and allowing for time-effective large-scale parameter sweeps. Our single channel fiber concept is particularly valuable for applications demanding fast and reliable injection of liquids into the core, with potential impact in fields such as optofluidics, spectroscopy or bioanalytics.

Measurement of the Verdet Constant of Polarization-Maintaining Air-Core Photonic Bandgap Fiber

We propose a method based on the white-light interference technique for measuring the Verdet constant of a polarization-maintaining air-core photonic bandgap fiber (PM-PBF). The experimental results show that the Verdet constant of the PM-PBF is ~3.3 mrad/T/m for the broadband light with a spectral width of ~38 nm and a mean wavelength of ~1550 nm, which is ~124 times less than that of a conventional stress-induced birefringent fibers called PANDA fibers (~0.41 rad/T/m for the same broad-spectrum light). The results indicate that the nonreciprocal error induced by the Faraday effect in a fiber optic gyroscope (FOG) made of the PM-PBF is theoretically ~25 times less than that of a conventional FOG made of the PANDA fiber when other conditions, such as the fiber twist, fiber coil area, and so on, are the same.

Low temperature conductivity and ion dynamics in silver iodide-silver metaphosphate glasses

Silver iodide-silver metaphosphate glasses xAgI·(1 - x)AgPO₃ (x = 0.3, 0.4, and 0.5) have been prepared using the usual melt quenching method. Differential scanning calorimetry has been used to determine the glass transition temperature of the samples. Impedance spectroscopy spanning wide temperature (20 K to 200 K) and frequency (10^-1 Hz to 10⁶ Hz) ranges has been employed to investigate the ion dynamics. At high temperatures, below the glass transition temperature and down to around 120 K, the dynamics show the usual behavior of dc and dispersed conductivity due to the random and correlated motion of the ions. The dc conductivity of the glasses varies dramatically and it increases with the AgI content as expected. At the lowest temperatures investigated, however, the conductivity of the glasses was indistinguishable. Hence, the low temperature dynamics are identical irrespective of the amount of AgI and the structure of the glass. In addition, a nearly constant loss behavior, independent of the temperature and composition, was attained at the lowest temperatures.

Octave-spanning supercontinuum generation in hybrid silver metaphosphate/silica step-index fibers

We reveal the potential of step-index fibers consisting of a metaphosphate glass core and a silica cladding as an ultrafast octave-spanning supercontinuum source. The hybrid waveguide was fabricated by pressure-assisted melt filling and possesses a sophisticated dispersion behavior with two zero-dispersion points in the proximity of the Erbium laser bands. The fiber generates an octave-spanning supercontinuum from 0.7 to 2.4 μm if pumped at 1.56 μm with 30 fs pulses and energies as low as 300 pJ. Numerical simulations reveal soliton fission and double dispersive wave generation as the dominant broadening effect. This study highlights phosphate glasses as a promising new candidate for the next generation of broadband photonic devices, as they allow for high rare earth-doping levels and dispersion posttuning via plasmonic nanoparticle growth.

Silver iodide phosphate glass microsphere resonator integrated on an optical fiber taper

In this Letter, we demonstrate the fabrication and characterization of a robust and functional whispering gallery mode (WGM) resonating system based on a silver iodide phosphate glass microsphere melted on an optical fiber taper. The fabrication process is presented, together with spectral characterization of the device. The effect of the thermal annealing of the soft glass resonator on the whispering gallery modes' excitation and Q-factor is shown and discussed.

Silver metaphosphate glass wires inside silica fibers--a new approach for hybrid optical fibers

Phosphate glasses represent promising candidates for next-generation photonic devices due to their unique characteristics, such as vastly tunable optical properties, and high rare earth solubility. Here we show that silver metaphosphate wires with bulk optical properties and diameters as small as 2 µm can be integrated into silica fibers using pressure-assisted melt filling. By analyzing two types of hybrid metaphosphate-silica fibers, we show that the filled metaphosphate glass has only negligible higher attenuation and a refractive index that is identical to the bulk material. The presented results pave the way towards new fiber-type optical devices relying on metaphosphate glasses, which are promising materials for applications in nonlinear optics, sensing and spectral filtering.

Vibrational spectroscopic and bond valence study of structure and bonding in Al2O3-containing AgI–AgPO3 glasses

We present a detailed investigation of the effects of synthesis conditions on glasses xAgI–(1 − x)AgPO₃ with 0 ≤ x ≤ 0.4.

Multi-channel SPR biosensor based on PCF for multi-analyte sensing applications

This paper presents a theoretical investigation of a novel holey fiber (Photonic Crystal Fiber (PCF)) multi-channel biosensor based on surface plasmon resonance (SPR). The large gold coated micro fluidic channels and elliptical air hole design of our proposed biosensor aided by a high refractive index over layer in two channels enables operation in two modes; multi analyte sensing and self-referencing mode. Loss spectra, dispersion and detection capability of our proposed biosensor for the two fundamental modes (HE(11)(x) and HE(11)(y)) have been elucidated using a Finite Element Method (FEM) and Perfectly Matching Layers (PML).

Optical Spectra Tuning of All-Glass Photonic Bandgap Fiber Infiltrated with Silver Fast-Ion-Conducting Glasses

Silver iodide metaphosphate glasses of the xAgI + (1-x)AgPO₃ family are embedded inside the air capillaries of a commercial silica photonic crystal fiber (PCF) by means of vacuum-assisted infiltration technique. In this paper, we report on tuning the photonic bandgap (PBG) guidance characteristics of the fabricated all-glass photonic bandgap fibers, by varying the composition of the fast-ion-conducting phosphate glass infiltration medium. Doping AgPO₃ metaphosphate glass with AgI significantly alters the PBG guidance patterns in the examined range between 350 and 1750 nm, as it leads to the introduction of numerous additional transmission stop-bands, while affecting scattering dependant losses. The effect of phosphate glass cooling method during sample fabrication on the transmission behavior of the xAgI + (1-x)AgPO₃/PCFs is also considered.