Bioresorbable optical fiber Bragg gratings

We demonstrate, for the first time, an inscription and wet dissolution study of Bragg gratings in a bioresorbable calcium-phosphate glass optical fiber. Bragg gratings, with average refractive index changes of 5.8 × 10^−4, were inscribed using 193 nm excimer laser radiation. Results on the dissolution of the irradiated fiber in simulated physiological conditions are presented after immersing a tilted Bragg grating in a phosphate buffered saline solution for 56 h; selective chemical etching effects are also reported. The investigations performed pave the way toward the use of such phosphate glass fiber Bragg gratings for the development of soluble photonic sensing probes for the efficient in vivo monitoring of vital mechanical or chemical parameters

Concentration quenching in an Er-doped phosphate glass for compact optical lasers and amplifiers

In this paper, highly (up to 5.25 mol% Er2O3) Er-doped phosphate bulk glasses were synthesized by conventional melt-quenching method and their physical, thermal and spectroscopic properties are reported. The influence of Er3+ doping concentration on emission spectra and lifetimes was investigated in order to study the concentration quenching effect on luminescence performance and therefore to evaluate the most suitable rare earth content for developing compact fibre laser and optical amplifier operating at 1.55 μm. A radiative lifetime and a quenching concentration equal to τ0 = 7.05 ms and N0 = 9.92 × 1020 ions/cm3 were respectively calculated by fitting the fluorescence lifetime experimental data with Auzel's limited diffusion model

Nd³⁺ doped phosphate glass waveguides for pulsed laser applications

Two phosphate glass compositions were designed and fabricated with the aim of realizing core/clad waveguides for high power pulsed laser applications. Preforms and waveguides (rods and fibers) manufacturing by preform drawing is reported

Design, processing and characterization of custom phosphate glasses for photonic and biomedical applications

Phosphate glasses (PGs) are promising host materials for the development of compact fiber amplifiers and lasers thanks to their good chemical durability, easy processing, outstanding optical properties, no clustering effect and very high solubility of rare-earth (RE) ions. Furthermore, some particular calcium-phosphate glasses exhibit unique dissolution properties in aqueous media with degradation rates that can be tailored by properly designing the glass composition. This feature makes them attractive biomaterials and allows the engineering of novel biomedical devices for deep-tissue diagnosis and therapy. In this work we will report the ongoing activities and the recent results obtained by our research group on the design, processing and characterization of novel custom phosphate glasses for both photonic and biomedical applications

Highly doped phosphate glass fibers for compact lasers and amplifiers: A review

In recent years, the exploitation of compact laser sources and amplifiers in fiber form has found extensive applications in industrial and scientific fields. The fiber format offers compactness, high beam quality through single-mode regime and excellent heat dissipation, thus leading to high laser reliability and long-term stability. The realization of devices based on this technology requires an active medium with high optical gain over a short length to increase efficiency while mitigating nonlinear optical effects. Multicomponent phosphate glasses meet these requirements thanks to the high solubility of rare-earth ions in their glass matrix, alongside with high emission cross-sections, chemical stability and high optical damage threshold. In this paper, we review recent advances in the field thanks to the combination of highly-doped phosphate glasses and innovative fiber drawing techniques. We also present the main performance achievements and outlook both in continuous wave (CW) and pulsed mode regimes

Novel biocompatible and resorbable UVtransparent phosphate glass based optical fiber

In this paper the first glass based resorbable optical fiber is manufactured and characterized, showing values of attenuation loss from one to two orders of magnitude lower than the polymeric based bioresorbable devices reported in literature. The fiber behaves as a singlemode waveguide at the lower limit of the first biological window (1300 nm) and as a multi-mode waveguide in the visible region (630 nm). Highly transparent calcium-phosphate glasses (PGs) are proposed as a new class of materials for biomedical optics, managing to combine for the first time in a vitreous material solubility in aqueous media, transparency in the near UV region, low intrinsic attenuation loss and thermal stability during fiber drawing. In-vitro tests in physiological conditions show dissolution kinetics of glass fibers in about a month

Core/clad tellurite glass pairs for mid infrared supercontinuum generation in high numerical aperture step index optical fiber

We report on the design and fabrication of two tellurite glass compositions as core and cladding glasses for a high numerical aperture optical fiber for mid-infrared supercontinuum generation. Preform and fiber fabrications are also reporte

Er-doped phosphate glasses for near infrared laser sources

Eye-safe lasers operating at the wavelength of 1550 nm are of great interest for the development of coherent sources for remote sensing, such as LIDARs or range finding systems. The most efficient activator ion commonly employed for this emission wavelength is Er3+, while inorganic glasses are suitable host materials because of their low cost, high versatility and the possibility they offer of obtaining the active cavity in the form of an optical fibre. Among the possible host glasses, silica is the most popular choice thanks to its high thermal stability and good mechanical properties. However, its reduced solubility for rare earth ions does not allow the implementation of compact optical devices, while on the contrary phosphate glasses represent an interesting alternative. This work reviews the design, fabrication and characterization of a series of Er-doped phosphate glasses suitable for the realization of eye-safe laser sources. The glasses were doped with increasing Er3+ ion amounts, namely 0.02, 1, 2, 6 and 10 mol%. A series of phosphate glasses with increasing Er3+ ion concentration (Table 1) was prepared by mixing powdered chemicals with 99+% purity. The batched chemicals were melt quenched at temperature above 1300 °C under a dry air flux and finally casted onto pre-heated brass moulds. The physical, thermal and optical properties of the glasses were thoroughly evaluated. All the prepared glasses were homogeneous and highly stable: average values of 486 ± 3 °C and 982 ± 3 °C were measured for glass transition (Tg) and crystallization (Tx) temperatures, respectively. The term ΔT = Tx−Tg is commonly used as an estimate of the glass stability and the obtained value of ΔT = 496 ± 6 °C demonstrates the ability to draw crystal free optical fibres. Prism coupling technique was used to measure the refractive index of the manufactured glasses (Fig. 1) at five different wavelengths. Emission spectra were measured by exciting the glass samples with a laser diode operating at the wavelength of 976 nm, using a lock-in and a chopper to improve S/N ratio. Lifetime values up to 7 ms were measured at the wavelength of 1550 nm for the Er3+:4I13/2 excited state level. The results of the full characterization of the prepared samples will be presented, together with the selection of the best candidate for the fabrication of the active medium of the eye-safe optical fibre laser

Femtosecond Laser Written Plane-by-Plane Bragg Grating Sensors in Bioresorbable Phosphate Optical Fibres

We report on the realization of different types of optical sensors in a bioresorbable phosphate glass optical fiber using a femtosecond laser operating at 517 nm. We inscribed fiber Bragg grating-based optical filters such as uniform Bragg gratings, chirped gratings, and Fabry–Perot cavities, using the plane-by-plane direct write inscription. The gratings were characterized in reflection and tested as sensors for temperature and relative humidity. We studied the stability and resilience of the gratings when inserted in high humidity environments (>95%) for 52 h and observed the evolution of the grating characteristics during this period