Scattering properties of ZrF-based glasses preparedby the gas film levitation techniqueA. Lopez***, P. Baniel*, P. Gall***, J. Granier***Alcatel Aisthom Recherche, Route de Nozay, 91460 Marcoussis, France**CEA/DTA/CEREM/DEM, Section d'Etude de la Solidification et de la Cristallogenese,38041 Grenoble, France***Centre d'Electronique de Montpellier, U.S.T.L., FranceABSTRACT

New multicomponent PbF2–InF3–GaF3 bulk glasses have been investigated. They show lower phonon energy (540 cm−1) in comparison with 580 cm−1 for ZBLAN. Large PbF2 concentration provided glasses with high refractive index up to 1.582 and the viscosity curves revealed an excellent thermal compatibility with ZBLAYN glass. A multimode fiber with a numerical aperture of 0.51, a loss of 0.85 dB/m at 1.3 μm was fabricated using the rotational casting method.

An accurate technique was implemented to measure spectral hole burning in rare-earth amplifiers at room temperature, showing that thulium-doped fiber amplifiers exhibit hole depths four times lower than those of C -band erbium-doped fiber amplifiers.

Using high resolution laser spectroscopy, we studied the broadening of the 1.5µm transition in different glassy hosts. The distribution of erbium in the matrix is investigated and the gain spectral hole burning comportment is discussed.

It is shown that, used in conjunction with 1550-nm pumping, 1047-nm pumping is more suitable to operate the TDFA in the short wavelength band while 1400-nm pumping is more efficient for the long wavelength band.

A new pumping scheme (1.2 /spl mu/m+1.4 /spl mu/m) is demonstrated for the gain-shifted TDFA, leading to record efficiency of 48% using one single pump dual-wavelength laser. This pumping scheme was implemented with a dual wavelength Raman fiber laser, giving 48% optical efficiency.

We present a spectroscopic background in order to optimize Tm doped S-band Optical fluoride fiber amplifiers.We measure the excited state absorption spectra between 1 and 1.5 μm and discussed the choice of amplifier pump wavelengths.

With 1064 nm pumping, 5 dB extra gain is exhibited, and with a two-wavelengths pumping, 5 nm gain broadening and 16 nm gain shifting are experimentally shown for the thulium doped fluoride fiber amplifier.

A lumped optical fibre amplifier exploiting the full spectrum of optical fibres and delivering a record bandwidth of 17.7 THz (between /spl lambda/=1297 nm and /spl lambda/=1605 nm) has been achieved using a combination of erbium-doped, thulium-doped and Raman fibres.

Radioluminescence, cathodoluminescence, and thermoluminescence of Zr-Ba-La-Al-Na (ZBLAN) fluoride glass reveal different aspects of the intrinsic imperfections and impurities which control the emission. Except for weak low-temperature thermoluminescence signals which could be attributed to rare-earth impurities, the majority of the emission bands were common to all samples. These are considered to arise from intrinsic electron-hole recombination processes, either during relaxed exciton emission or at intrinsic defect sites in the glass network. Deconvolution of the spectra indicates that six emission bands occur in all the samples. Production of crystallite inclusions or intrinsic defects enhance the signal intensities. The luminescence is shown to be a useful probe of the quality of the ZBLAN glass, both in the preform stage, and after fiber drawing, even when working with the very high grade material produced by gas film levitation growth.

Fluoride glasses for optical fibre applications were prepared using a containerless processing technique (the gas film levitation technique) to prevent the contamination of the glass melts by the crucible. Bulk glass samples of high optical quality were obtained by starting directly from a powder mixture of the different fluoride precursors. Differential scanning calorimetry, laser scanning tomography and light scattering measurements were used to measure the properties of the levitated glasses as compared to crucible-made glasses prepared in the same conditions. The bulk levitated glasses had an extended thermal stability range along with improved optical properties over the crucible-made glasses.