Fluoride Glass Optical Fibers Research Articles

Beyond near-infrared lossy mode resonances with fluoride glass optical fiber.

The objective of this Letter consists of the exploration of the lossy mode resonance (LMR) phenomenon beyond the near-infrared region and specifically in the short wave infrared region (SWIR) and medium wave infrared region (MWIR). The experimental and theoretical results show for the first time, to the best of our knowledge, not only LMRs in these regions, but also the utilization of fluoride glass optical fiber associated with this phenomenon. The fabricated devices consist of a nanometric thin-film of titanium dioxide used as LMR generating material, which probed extraordinary sensitivities to external refractive index (RI) variations. RI sensitivity was studied in the SWIR and MWIR under different conditions, such as the LMR wavelength range or the order of resonance, showing a tremendous potential for the detection of minute concentrations of gaseous or biological compounds in different media.

Splicing fluoride glass and silica optical fibers

Splicing fluoride glass fibers and silica fibers is a critical point for manufacturing all fibered laser modules. As these materials are extremely different, various problems must be considered: thermal, expansion, mechanical, chemical. Reliability and power handling make priority concerns. We report splices made on a 200/220 multimode silica fiber and a double clad 15/250/290 ZBLAN fiber. Splices are proof tested at 300 g tensile strength. No damage is observed after thermal cycling from -30 °C to 85 °C, at 40 % RH during 24 hours. Typical optical splice loss is about 0.2 dB. They withstand 220 W input power at 976 nm without any damage and drastic temperature increasing.

Fluoride glass Raman fiber laser at 2185 nm

We report on the first Raman laser based on a fluoride glass optical fiber. The Raman fiber laser was pumped by a 9.6 WTm3+:silica CW fiber laser operating at a wavelength of 1940 nm. A maximum output power of 580 mW was measured at 2185.1 nm, corresponding to a frequency shift of 579 cm(-1) (17.37 THz). We observed a threshold power of 3.8 W and a low power slope efficiency of 29% with respect to the launched pump power. Using those results and the known fiber parameters, we estimated a Raman gain peak value of 3.52*10(-14) m/W, which is lower than the previously reported values.

ChemInform Abstract: Rare-Earth Doped Fluoride Glass Fibres

Abstract Fluoride glass optical fibres are characterized by a large optical window covering the range 0.4–5 μm which permits excitation and fluorescence spectroscopy in a much more extended domain than with silica-based fibres. The local ligand field acting on the rareearth ions affects the radiative lifetime, phonon relaxation, excited state absorption, and emission peak broadening. Finally, the fibre structure provides excellent optical confinement for observing laser emission in the visible and mid-IR regions at very low threshold power, permitting laser diode pumping. Multiphonon processes are also observed leading to the up-conversion of IR into the visible or UV and making possible the development of new laser sources for optical recording laser printing, optical amplification, medical and optical sensor applications.

Measurements of brake disc surface temperature and emissivity by two-color pyrometry

Abstract A fiber optic two-color pyrometer was developed for brake disc surface temperature and emissivity measurements. The two-color pyrometer consists of a fluoride glass optical fiber, two HgCdTe detectors equipped with bandwidth filters and a data conditioning and acquisition device. The two-color pyrometer measures the brake disc temperature in the 200–800 °C range with a time resolution of 8 μs. The calibration formula for the signals obtained using a blackbody of known temperature is used to compute the true temperature. The uncertainty estimation for temperature and emissivity was obtained from the calibration results. Tests were carried out on known temperature target and a good correlation was found between results obtained with our two-color pyrometer and those obtained with a commercial two-color pyrometer. Hold braking and deceleration braking tests performed on a braking test bench enabled us to reach the brake disc surface temperature and emissivity during braking. Experimental results show a significant variation of emissivity during braking. Direct measurement of emissivity was carried out on the brake disc after braking and shows the emissivity dependence with the surface quality.

Design and fabrication of Pr3+-doped fluoride glass optical fibres for efficient 1.3 mu m amplifiers

Two novel glass compositions aimed at improving the quantum efficiency and gain of the 1.3 mu m praseodymium-doped fibre amplifier (PDFA) were developed and investigated. The two glasses were compositions based on cadmium halide and gallium fluoride. Both bulk glass samples and core-clad fibre structures were fabricated and studied. A variety of measurements have been carried out in order to assess the potential of these glasses as hosts for PDFA. The results were used to perform a detailed modelling of the projected amplifier characteristics. Both glasses are judged to be promising candidates for the second generation of 1.3 mu m PDFAs.

High numerical aperture heavy metal fluoride glass combinations for single-mode optical fibres

The core-cladding composition difference is a crucial element in the design of high numerical apertures for single-mode fluoride glass optical fibres. The larger the numerical aperture, the more light that can be launched into the fibre core. Starting with well known stable glass compositions containing zirconium fluoride, PbF2, LiF and GaF3 have been introduced into the core and cladding respectively to increase the difference in refractive index, Δn, and thus increase the numerical aperture, while still maintaining a high degree of stability. A refractive index difference, Δn, of 0.06 and numerical aperture of 0.41 was obtained for compositions (ZrF4-BaF2-LaF3-AlF3-LiF-PbF2 (ZBLALiPb3) for the core and ZrF4-BaF2-LaF3-AlF3-NaF-GaF3 (ZBLNGa13) for the cladding), where the difference in the glass transition temperature, Tg, was only 4°C. The relationship between the differences in refractive index, Δn, and glass transition temperature, ΔTg, with compositional changes of the glass host are discussed.

Superfluorescent fiber source at 3.9 μm in the attenuation minimum of the atmospheric window 3–5 μm

Superfluorescence has been demonstrated for the first time at 3.9μm in holmium-doped fluoride glass optical fiber. Fluorescence measurements were possible at room temperature while pumping around 650 nm. Cooled to 173 K superfluorescence was obtained.

Active fluoride glass optical waveguides for laser sources

Abstract Fluoride glasses involved in the realization of laser sources are described. Observed lasing wavelengths, which range from the blue to the mid infrared in fluoride glass optical fibers are reviewed. Also, recent results on planar waveguides, including fabrication and optical properties, are presented.

BIG fluoride glass optical fibers with improved NA

Abstract A low refractive index fluoride glass based on barium, indium and gallium has been synthesized. By addition of aluminum, sodium and potassium fluorides to the base glass (BIGaZYbTZr), an index as low as 1.482 is obtained. The glass physical parameters are given and are found to be fully compatible with those of the base glass. A preform suitable for fiber drawing and exhibiting a theoretical numerical aperture of 0.26 is obtained. Optical losses are measured for the best fiber.

Characterization of fluoride glasses for single-mode optical fibers with large refractive index difference

Abstract In order to obtain fluoride glass optical fibers with large refractive index difference between the core and the cladding, refractive indices and viscosities of PbF2-doped core glasses and HfF4-incorporated cladding glasses were systematically investigated. From the point of view of viscosity matching, it was found that the 9 mol% PbF2-doped core glass containing 14 mol% NaF was the most adequate choice in combination with the 43 mol% HfF4-incorporated cladding glass containing 22 mol% NaF. Using a casting method, single-mode fluoride glass fibers with relative refractive index difference of 2.9% were successfully fabricated.

Gain saturation characteristics of Raman amplification in silica and fluoride glass optical fibers

Raman amplification in silica and fluoride glass fibers is studied experimentally and theoretically. Two tunable dye lasers are employed to provide pump and signal light. In an 80 m long silica glass fiber, a small-signal gain of 39 dB has been achieved at a pump wavelength of 580 nm. The gain bandwidth is 127 cm -1 in small-signal amplification and 250 cm -1 in saturated amplification. In an 18 m long fluoride glass fiber, a small-signal gain of 9.3 dB has been obtained. The measured Raman-gain coefficient at 580 nm is (2±0.5) × 10 -11 cm/W in the fluoride glass fiber.

Spectral optimization of a pulsed HF chemical laser for efficient energy delivery through a low-loss fluoride glass optical fiber

Pulsed HF chemical lasers oscillating in the midinfrared region of the spectrum where water can strongly absorb are suitable for the organic tissue ablation. For such a medical application, a flexible energy delivery system using an optical fiber is indispensable. The fluoride glass optical fiber may be used for low-loss optical energy delivery of the pulsed HF laser. Using an intracavity CO2 absorption cell, we have optimized pulsed multiline HF chemical laser spectrum for low-loss energy delivery through a fluoride glass optical fiber whose transmission loss is theoretically estimated to be minimum around 2.5 μm. The fractional output energy of P1-0(3) and P1-0(4) lines, which are sitting in the lowest loss spectral region of the practical fluoride glass fiber, exceeded half the multiline output energy using a line selective intracavity CO2 gas cell. The P1-0(4) line extracted from the resonator with a diffraction grating was successfully delivered through a 3-m-long commercial fluoride glass fiber (core/cladding diameter=450/500 μm). The delivered energy of 11.9 mJ was achieved with the corresponding energy fluence of 12 J/cm2 and peak intensity of 22 MW/cm2 at the exit core surface without optical damage.

Current status of infrared fiber optics for medical laser power delivery.

There are a host of fiber-optic delivery devices available for use with the Er:YAG, HF, CO, and CO2 lasers at 2.9, 2.8, 5.3, and 10.6 microns wavelengths, respectively. While many of these fibers are not as convenient to use as conventional silica fibers, they offer the ability to deliver infrared laser energy for a wide variety of medical applications. The fundamental attributes of fluoride glass, chalcogenide glass, single-crystal sapphire, and polycrystalline silver halide optical fibers are reviewed and their practical properties tabulated.

Rare-earth doped fluoride glass fibres

Fluoride glass optical fibres are characterized by a large optical window covering the range 0.4–5 μm which permits excitation and fluorescence spectroscopy in a much more extended domain than with silica-based fibres. The local ligand field acting on the rareearth ions affects the radiative lifetime, phonon relaxation, excited state absorption, and emission peak broadening. Finally, the fibre structure provides excellent optical confinement for observing laser emission in the visible and mid-IR regions at very low threshold power, permitting laser diode pumping. Multiphonon processes are also observed leading to the up-conversion of IR into the visible or UV and making possible the development of new laser sources for optical recording laser printing, optical amplification, medical and optical sensor applications.

Fusion Splicing of Heavy Metal Fluoride Glass Optical Fibers

Fusion Splicing of Heavy Metal Fluoride Glass Optical Fibers

Detection of Propane by IR-ATR in a Teflon®-Clad Fluoride Glass Optical Fiber

The detection of propane with the use of ATR spectroscopy at 3.3 µm, as the gas diffuses through the Teflon® cladding of a fluoride optical fiber, is reported. A theoretical expression for the time-dependent absorbance of the fiber sensor as a function of diffusion coefficient and cladding dimensions is developed. The experimental data fitted to the model give a diffusion coefficient of 8.85 × 10−14 m2 s−1 for propane in Teflon®. The potential of the technique for remote or distributed sensing of hydrocarbons is discussed.

Raman microscope analysis of gaseous and solid inclusions in fluoride glass optical fibres

Raman microscopy has been used as a non-destructive technique for analysing gaseous or solid inclusions in optical fibres or preforms. Two alternative Raman geometries using 90° and 180° scattering were evaluated, and the latter found to be more effective for these samples. Examples of glass inclusion analysis are provided by the identification of 10 µm LaF3 microcrystals, oxygen in 4 µm diameter bubbles and the differentiation of carbon allotropes in fluoride glass fibres.

Fusion splicing of heavy metal fluoride glass optical fibres

Heavy metal fluoride (HMF) glass optical fibres were spliced by fusing the two ends of fibres using a DC arc. An average optical loss of 0.08 dB per splice and strengths of up to 600 M Pa were achieved for fusion splices using an inert gas purge during splicing. Estimates are made to determine the feasibility of achieving a splice loss of 0.005dB for singlemode (HMF) fibres.

Fabrication of Oxide Glass Coated Fluoride Glass Optical Fibers for Durability and Strength Improvement

AbstractThe crystallization of fluoride glass being in contact with oxide glass is investigated using thermal analyses to perform oxide glass coating for durability and strength improvement. The chemical reaction does not occur in the fiber drawing temperature range and begin at the melting temperature of fluoride glasses. The crystallization of fluoride glass is suppressed by contact with oxide glass. Smooth contact between fluoride and oxide glasses is confirmed.