This is the first report of ESR observations of three distinct paramagnetic centers in TeO29 glasses. One center is intrinsic to the glass and the other two are induced by KrFexcimer-laser radiation. The intrinsic center with a broad ESR spectrum is tentatively identified as an oxygen-associated hole center. One radiation-induced center fades slowly at room temperature; its proposed structure is that of an electron trapped in a diffuse orbital associated with a modifier ion. The other radiation-induced center is stable at room temperature and corresponds to the Vo· center observed in crystalline paratellurite.

Trivalent thulium is a 4-level laser system which operates in the 1.47μm spectral region. A tunable amplifier at this wavelength is of great interest since it falls in one of the telecommunication windows. For lasing action to occur the relatively long lived 3F4 lower laser level must be quenched to eliminate the self-terminating behavior of thulium. Rosenblatt et al. co-doped Tm and Th into a ZBLAN host to quench the 3F4 lower laser level.[1] Co-doping with Ho offers the possibility of more efficient laser operation, but it must be established whether Ho can effectively quench the lower level of Tm. This preliminary study indicated appreciable energy transfer occurred from the 3F4 level of Tm to the 5I7 level of Ho which decreased the lower laser level lifetime by as much as two orders of magnitude. The subsequent decay of the Ho ions is an issue requiring further investigation.

Erbium-doped LaF3 transparent gels have been synthesized by the solution synthesis of metal inorganic precursors. The solid solubility of Er3+ can reach 60 mol %, which is almost double the solubility limit of Er3+ in LaF3 synthesized by the Bridgman technique. A quantitative analysis of the absorption and emission spectral data shows that the quantum efficiency of the 1.55 μm emission band is comparable to that of melt grown single crystal. However, the emission spectral width of the 1.55 μm band is found to be 40% greater than that of the melt grown single crystal, which extends the spectral bandwidth to 11 THz. The high solid solubility of Er3+ supports 36 cm−1 single pass optical gain, which is three times higher than that in zirconium barium lanthanum aluminum sodium glass. The high Er3+ concentration and spectral bandwidth enable LaF3:Er amplifiers to be made by a low-temperature solution-based technique.

Intense blue upconversion luminescences were observed in a high-NA silica fiber doped with Tm3+ and 25mol% GeO2 by pumping with a 630-670nm laser. The intensities of two bands due to the 1D2 → 3F4 at 455nm and 1G4 → 3H6 transition at 480nm were changed with the pumping wavelength, power, and the fiber length. These phenomena were ascribed to the population inversion of the3F4 excited state to the ground state and large population of the 3H4, that are the intermediate excited levels for the 3G4 and 1D4 upconversions, respectively. The nonlinear power dependence of the population could be due to the relatively low-phonon-energy, high Tm3+-concentration and high pump-power density in the core of this high-NA fiber. The peak shift of the 480nm-band with the fiber length and a two-photon process of 1.2 µm luminescence band are also discussed.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text John Ballato, Richard E. Riman, and Elias Snitzer, "Highly Efficient 1.3-μm Luminescence from Rare-earth-doped Halides Prepared from Low Temperature Aqueous Solutions," Optics & Photonics News 9(12), 17-18 (1998) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

Summary form only given. Although erbium-doped fiber amplifiers at 1.5 /spl mu/m in silica have been outstandingly successful, other hosts such as fluorides or tellurites have been studied because of their broader gain lines, which could make them advantageous for WDM systems. The use of other hosts doped with other rare earths are being considered for other wavelengths, particularly the near-IR 3- to 5-/spl mu/m region. The choice of a glass host for a given rare earth transition depends on the competition between radiative transition probabilities and the quenching phonon relaxations.

The optical properties of several sulfur-based glasses doped with Pr3+ and Dy3+ have been measured, with emphasis on the 1.3 μm emission quantum efficiency. Glass hosts prepared using conventional methods include As2S3, As2S3 with 1.7 mol% I2, Ge30As10S60, Ge25Ga5S70, and Ge35S56.5I8.5 for Pr3+, and all but the As2S3 based compositions for Dy3+. Data obtained from optical absorption and fluorescence spectra and fluorescence lifetime measurements were used for theoretical predictions of quantum efficiency. These theoretical efficiencies were compared to absolute efficiency measurements using either an integrating sphere based system or a self-calibration technique (Pr3+ only, no As2S3-based glasses). The latter method produced erroneous values for glasses having electronic absorption edges beyond 500 nm, possibly due to a host sensitization phenomenon. A 100 ppm Pr2S3 doped GeGaS glass was the most efficient at 1.3 μm, measuring 93% via the integrating sphere technique. The measured efficiencies for Dy3+ doped glasses at 1.3 μm, the first reported to our knowledge, were less than those theoretically predicted. The most efficient Dy3+ doped sample, a 0.1 wt% Dy2S3 doped GeSI glass, was measured to be 6%.

There exists a tremendous growth in photonic materials and device research as a result of both the explosion in telecommunications as well as the expected traffic requirements needed for interactive video and multimedia services.

A side-pumping technique, using an imbedded v-groove is used to efficiently pump a double-clad Er/Yb doped fibre amplifier operating at 1.5 mu m and pumped at 0.98 mu m. A diode-to-fibre coupling efficiency of 76% was measured for a 100 mu m wide broad stripe laser diode and a fibre with a 50 x 120 mu m first cladding. A maximum output power of 185mW, and separately, a small signal gain of 35dB, are demonstrated.

The sol-gel synthesis of fluoride materials provides a viable and low-cost method for achieving planar and bulk devices for integrated photonic applications. This paper describes these prospects and methods for the experimental development of patterned and waveguiding films. The sol-gel synthesis from both metal-organic and inorganic precursor systems is discussed in relation to their potential for passive and active device applications.

Praseodymium- and dysprosium-doped lanthanum halide powders have been synthesized by a sol-gel-reactive-atmosphere approach. Emission at 1.3 microm from a sol-gel-derived material was observed for the first time to our knowledge. Measured lifetimes corresponded to radiative quantum efficiencies of approximately 8% for Pr(3+):LaF(3), 72% for Pr(3+):LaCl(3), and 78% for Dy(3+):LaCl(3) . The spectroscopic properties of these hosts are shown to be comparable with those of melt-grown single-crystal analogs, verifying the ability of inexpensive and low-temperature solution-based methodologies to produce low-phonon-energy materials.

Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text C. J. Koester and E. Snitzer, "Amplification in a Fiber Laser," in Optical Amplifiers and Their Applications, M. Zervas, A. Willner, and S. Sasaki, eds., Vol. 16 of OSA Trends in Optics and Photonics Series (Optica Publishing Group, 1997), paper RP1. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

This review paper introduces fluoride materials, their conventional processing and how sol-gel processing can be used both to simplify processing and to improve properties. A multistep process incorporating sol-gel synthesis and a reactive treatment is used to prepare a monolithic fluoride glass. The first step is synthesizing a porous, atomically homogeneous hydrous oxide gel containing zirconium, barium, lanthanum, aluminum and possibly sodium as components (ZBLA or ZBLAN). The second step is a relatively low-temperature reactive treatment of the gel with a fluorinating agent to achieve a porous, noncrystalline fluoride. Subsequently, amorphous fluoride powders are melt-quenched to high-quality glasses or fiber preforms. Alternatively, thin films are viscous sintered to near-theoretical density. Active optics are achievable through rare-earth doping of the sol prior to gelation or thin film deposition The present status and future challenges in the preparation of optical-quality fluoride glasses via this method will be presented.

This paper describes ZBLA fluoride glass thin films produced via an inexpensive, low-temperature reactive atmosphere sol-gel approach. Luminescence from erbium at 1.55 μm has been observed in x-ray-amorphous doped films deposited on calcium fluoride, polyimide, sapphire, and silicon substrates. Fluorescence studies of the erbium 4S3/2 → 4I13/2 transition, a characteristic emission for a reduced phonon energy host, were conducted for both sol-gel-derived films and conventionally prepared glass rods. The peak intensity observed from the sol-gel films was blue-shifted by 16 nm with a FWHM value approximately half that measured for the melt-quenched rods. Excitation studies indicate that, unlike conventionally prepared glasses, sol-gel materials suffer from nonradiative relaxation of the 4S3/2 excited state to the 4I9/2 level, where subsequent radiative emission to the 4I15/2 ground state occurs. The proposed source of the quenching mechanism are remnant species inherent to the sol-gel process. While this causes the luminescence behavior of rare-earth-doped sol-gel-derived fluoride materials to be similar to oxide hosts, these remnant species modify the branching ratios, resultantly leading to a novel 824 nm emission when excited at 488 nm.

Summary form only given. By tilting the Bragg grating relative to the fiber axis it ejects light from the fiber. The dependence on tilt angle of the attenuation, ejection line width, and center wavelength are described. Recent materials and laser device work for Tm-doped Si-Ge-Al cores is presented.

Two formulations based on perfluorinated polymer were prepared for use as UV-curable optical cladding for silica fibers. In the first formulation an adhesion promoting agent based on fluoroacrylate resin was synthesized and mixed with the experimental product Defensa 7702++ in order to promote wetting and chemical adhesion to the silica fibers. In the second formulation, wetting and physical adhesion between the liquid coating and the silica fibers were achieved by increasing the viscosity of the starting coating by addition of unsaturated perfluorinated polymer into Defensa. Both formulations were used as primary coatings on dual coated silica optical fibers. The mechanical behavior of the formulations was characterized by the strip test, the pull-out test and zero stress aging in 90 degrees Celsius pH 7 buffer. The results show that both formulations exhibit better wetting-adhesion characteristics than unmodified starting coating and that the strength degradation during zero- stress aging was lower for the fiber coated with the formulation of higher viscosity.

A new process for making fluoride glasses via the sol-gel route was investigated using Eu3+ fluorescence spectroscopy as a probe of the process. Both Eu3+ doped alkoxide ZBLA and zirconium fluoride gels and inorganic zirconium fluoride gels were synthesized and fluorinated with HF gas between 100 and 800°C. All gels showed changes in Eu3+ site symmetry upon drying and fluorination. The alkoxide gels darkened due to the incomplete combustion of alkoxy ligands and quenched fluorescence and decreased lifetimes. The inorganic gels were free of this problem and exhibited increasing lifetimes with increasing fluorination temperature and upper level Eu3+5DJ fluorescence never before seen in sol-gel derived materials. Thus, fluorination of inorganic gels can produce low phonon energy hosts, while transparent sol-gel fluoride glasses equivalent to conventionally prepared glasses can only be prepared by melting the fluorinated alkoxide derived gel in an oxidizing atmosphere.