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Treatment of fractures remains challenging and carries a high economical burden to both patients and society. In order to prevent some of the complications, the use of bone adhesives has been proposed, but up to date, bone adhesives are not part of the current clinical practice. Early results of use of bone cements and bone glues are promising, focusing in the areas of highly fragmented fractures, fixation of long bone fractures, filling bone voids and defects, promoting osseointegration, preventing non-union while maintaining the reduction of fracture fixation. This review aims to describe the state-of-the-art of the development, properties and use of adhesives in fracture treatment.

Need: Dental enamel is an acellular and avascular mineralised tissue, containing more than 95% calcium phosphate mineral. Although, the underlying softer dentine is connected with the microvasculature via the soft tissue and, therefore, possesses intrinsic regenerative capacity for mineralisation, the superficial enamel lacks regenerative potential. Consequently, the oral acid induced erosive damage on enamel is irreversible, and leads to lesion formation, which if unattended, may lead to hypersensitivity and feeling of pain. Advanced stage of eroded enamel with symptoms of hypersensitivity might lead to tooth loss in adults. Traditional clinical strategies for the repair of acid-eroded enamel include the use of off-shelf toothpastes and BIS-GMA polymeric materials; the latter is structurally incompatible with natural enamel due to mismatched thermal expansion coefficient and mechanical properties. As a result this type of bonding leads to failure of restored enamel area in a challenging oral environment [1]. Modern toothpastes only provide temporary symptomatic relief from hypersensitivity. Till date, no long-term or permanent solution for treating early stages of acid erosion is on offer. Associated with acid erosion is also erosive wear which affects especially the ageing population and leads to lingual tooth thinning and weakening. Rebuilding the entire damaged tissue region remains a challenge.

Raman spectroscopy was used to differentiate between mucosally healed (or quiescent) and inflamed colon tissue, as assessed endoscopically, in patients with ulcerative colitis. From the analysis of the Raman spectra of 60 biopsy tissue samples, clear differences were identified between the spectra of the quiescent and inflamed tissue. Three carotenoid peaks were found to be approximately twice as intense in the inflamed tissue. Two phospholipid peaks were found to be significantly lower in the inflamed tissue. Using multivariate statistical analysis, we show that these five peaks can be used to discriminate between endoscopically quiescent and inflamed tissue. We also correlated the Raman data with a histological assessment of the tissue. Four of the five peaks were found to be significantly different between the spectra of histologically healed (or quiescent) and histologically inflamed tissue. These findings indicate the ability of Raman spectroscopy to accurately classify colon tissue as either quiescent or inflamed, irrespective of whether an endoscopic or histological grading scheme is followed. We thus demonstrate that Raman spectroscopy could potentially be used as an early diagnosis tool for assessing the presence of mucosal healing or inflammation in patients with ulcerative colitis.

We demonstrate the control of CdS and Mn2+-doped-CdS Q-dots in a silicate glass for magneto-optical applications. The microstructural properties of Q-dot glasses were investigated by X-Ray diffraction (XRD), Field Emission Transmission Electron Microscopy (FETEM) and the optical properties by UV–Visible–NIR and Photoluminescence (PL) spectroscopic techniques, respectively. The FETEM of the CdS QD–glass heat treated at 600oC reveals that the size of CdS and Mn2+-doped CdS Q-dots are in the range of 4-5 nm and 5-6 nm, respectively. The observed size distributions of Q-dots were in reasonable agreement with the data, derived from X-ray line broadening and estimated average Bohr radii using the UV–visible absorption data. Photoluminescence characteristics were investigated at room temperature by exciting the CdS and Mn2+-doped-CdS Q-dot glasses with a 420 nm excitation source, which yielded broad emission spectra in the visible and near-IR range (450-800 nm). We observed a red shift in the emission peak with increase in the Q-dot size, controlled by heat treatment temperature range (550-600oC). The room-temperature magneto-optical Faraday rotation measurements on Q-dots glasses were carried out using magnetic field strength up to 360 mT, and observed an increase in the value of Verdet constant, from 6.2 to 12.0°/T-cm, when comparing undoped CdS-Q-dot glass with Mn2+-doped CdS glass. The demonstration of enhanced Verdet constant in Q-dot silicate glasses with sub-Tesla field paves the path for engineering range magneto-optical devices for photonics, spintronics and sensors applications, in which the polarization of photons may be controlled with low-intensity magnetic field in optical waveguides.

This research paper aims to compare the performance of various clustering and classification algorithms which are applied on the same educational dataset. Educational Data Mining (EDM) uses these algorithms to explore educational statistics to discover patterns and predictions in data that illustrate learner’s performance. Various design challenges such as accuracy, objective and functionality, and overheads when the data set is extremely large, etc., have been highlighted. The algorithms discussed here can be classified as centroid-based clustering, graph-based clustering, and various supervised classification algorithms. Further, after comparison of these algorithms, this paper aims at using the cited literature survey to determine the most suited algorithm according to the need of EDM clustering or classification. The regular search is on to understand students better and to know the patterns in which they learn to make it more efficient for them. Nowadays, many educational institutions have educational databases that can be utilized in various ways to make it effective for students but are unutilized. Powerful tools are required to get benefits from these educational databases. EDM is one of those emerging tools that analyzes the data collected from learning and teaching and then applies the techniques from machine learning and data mining for predicting student’s future behavior by learning detailed information such as student’s grades, knowledge, achievements, motivation, and attitude.

This chapter provides a review of laser sources based on a tellurium oxide (TeO2) glass hosts reported to date, whether in the form of bulk glass, fibre or microspheres. The majority of laser sources reported using tellurite glass as host material are based on rare-earth ion (Nd3+, Er3+, Tm3+ and Ho3+) dopants; however, there are also reports on supercontinuum generation and Raman lasing in highly nonlinear tellurite glass fibres. All of the tellurite glass-based lasers discussed in this chapter operate in the infrared spectral region with laser wavelengths around 1 μm, 1.5 μm, 1.9 μm and 2.1 μm for Nd3+, Er3+, Tm3+ and Ho3+ doping, respectively, while supercontinuum and Raman laser sources emit in the ranges 0.8–4.9 μm and 1.5–2.65 μm, respectively. The maximum optical output power reported to date from a tellurite glass laser is 1.12 W using cladding pumped fibre. Lasers operating in continuous wave, Q-switched and mode-locked regimes have also been demonstrated using rare-earth-doped tellurite glass hosts. The future prospects for lasers based on tellurite glasses are also discussed.

This review article focuses on the suitability of Er3+-doped tellurium oxide glass for optical amplification in fiber, waveguides and as a component for optical integration to meet the emerging demand for broadband and fiber-to-home networks. The importance of the glass structure, in the context of Er3+-ion spectroscopy, is emphasized for dissolving large concentrations of dopant ions. The spectroscopic methodologies involved in maximizing the gain per unit length of Er3+-doped fiber is explained. In Part II of this study, a review of how the fiber gain data was then employed to engineer amplification in waveguides, which can be integrated with semiconductor pump sources, is presented.

Germanium oxide (GeO 2 ) and tellurium oxide (TeO 2 ) based glasses are classed as the heavy metal oxide glasses, with phonon energies ranging between 740 cm −1 and 880 cm −1 . These two types of glasses exhibit unique combinations of optical and spectroscopic properties, together with their attractive environmental resistance and mechanical properties. Engineering such a combination of structural, optical and spectroscopic properties is only feasible as a result of structural variability in these two types of glasses, since more than one structural units (TeO 4 bi-pyramid, TeO 3 trigonal pyramid, and TeO 3+ δ polyhedra) in tellurite and (GeO 4 tetrahedron, GeO 3 octahedron) in GeO 2 based glasses may exist, depending on composition. The presence of multiple structural moities creates a range of dipole environments which is ideal for engineering broad spectral bandwidth rare-earth ion doped photonic device materials, suitable for laser and amplifier devices. Tellurite glasses were discovered in 1952, but remained virtually unknown to materials and device engineers until 1994 when unusual spectroscopic, nonlinear and dispersion properties of alkali and alkaline earth modified tellurite glasses and fibres were reported. Detailed spectroscopic analysis of Pr 3+ , Nd 3+ , Er 3+ , and Tm 3+ doped tellurite glasses revealed its potential for laser and amplifier devices for optical communication wavelengths. This review summarises the thermal and viscosity properties of tellurite and germanate glasses for fibre fabrication and compares the linear loss for near and mid-IR device engineering. The aspects of glass preform fabrication for fibre engineering is discussed by emphasising the raw materials processing with casting of preforms and fibre fabrication. The spectroscopic properties of tellurite and germanate glasses have been analysed with special emphasis on oscillator strength and radiative rate characteristics for visible, near IR and mid-IR emission. The review also compares the latest results in the engineering of lasers and amplifiers, based on fibres for optical communication and mid-IR. The achievements in the areas of near-IR waveguide and mid-IR bulk glass, fibre, and waveguide lasers are discussed. The latest landmark results in mode-locked 2 μm bulk glass lasers sets the precedence for engineering nonlinear and other laser devices for accessing the inaccessible parts of the mid-IR spectrum and discovering new applications for the future.

Integration of glass thin films with semiconductors promises new opportunities for novel photonic and optoelectronic devices due to the contribution of several synergetic properties. In this paper, we report the demonstration of the integration of Er3+-ion doped phosphate modified tellurite (PT) glass thin film waveguides with III-V semiconductor substrates. The thin films were deposited using the technique of pulsed laser deposition (PLD) and exhibit a refractive index which is very close to that of the bulk glass target used in the deposition process. Optical confinement and propagation loss measurements for the thin films deposited on GaAs substrates, with different thicknesses of silica buffer layers, is presented and shows good agreement with finite element models. Channel waveguide patterning was carried out using ultra-fast laser micromachining, and a range of optical characterization measurements are reported on confirming the high quality of the glass thin films and waveguides formed on silica and GaAs with silica buffer layers.

Absorption and fluorescence spectra and fluorescence lifetime measurements are presented for Ce3+:Er3+:Yb3+:YVO4 crystals and compared to the corresponding data for Er3+:Yb3+:YVO4 crystals. These results show that doping with Ce3+ ions reduces the lifetime of the 4I11/2 state of Er3+ and thereby both suppresses upconversion from this state and improves the energy transfer efficiency from Yb3+ to Er3+. Lasing from this material is also demonstrated for this first time, both in quasi-continuous wave (QCW) and Q-switched modes. To obtain laser action at ~ 1.5 μm, the Ce3+:Er3+:Yb3+:YVO4 crystals were pumped by laser diodes operating at ~ 0.98 μm. For QCW operation, a slope efficiency of 2.6% and a threshold of 12 W were obtained. Q-switched pulses of 27 μJ energy and 52 μs pulse to pulse duration were also measured.

Yb 3+ -Tb 3+ and Yb 3+ -Tm 3+ -Tb 3+ doped fluoro-germanate glass samples were fabricated in bulk and fibre form. Bright up-conversion has been obtained by exciting the samples with a 975 nm laser source, and the power dependence of the up-conversion intensities with respect to the excitation power has been characterised. Two mechanisms must be taken into account to explain the population of the 5 D 4 level of the terbium ions in these experiments; namely multi excited state absorption (MESA) and cooperative up-conversion (CU). While in the Yb 3+ -Tm 3+ -Tb 3+ samples both MESA and CU contribute simultaneously to the 5 D 4 :Tb 3+ population, in the Yb 3+ -Tb 3+ case a pure CU mechanism is responsible for the 5 D 4 :Tb 3+ population. In the fibre geometry, the re-absorption effect has been observed. The detrimental role of the re-absorption has been explained by characterising the up-conversion spectrum at different fibre lengths.

Phospho-tellurite glass thin films have been deposited on silica substrates using an ArF laser (λ = 193 nm, τ = 20 ns) at a laser fluence of 3.2 J/cm2 and for various oxygen pressures, substrate temperatures and target-to-substrate distances. The measured propagation losses of the phospho-tellurite glass thin films are in the range of 0.13–0.75 dB/cm, whilst the refractive indices of the glass thin films were in the range of 1.623–1.649 which is very close to that of the target glass, showing nearly stoichiometric transfer of the material from target to substrate. The results show significant promise for integrated active optical device applications using pulsed laser deposition (PLD) of this erbium doped phospho-tellurite glass material.

Short pulsed (ns) excimer laser was employed as a technique for the deposition of more than 2 μm thick glassy films from phosphorous pentoxide and tungsten lanthanum modified tellurite bulk glasses. High quality glass thin films with measured propagation loss less than 0.15, 0.71 and 2.3 dB.cm−1 were obtained after optimization of deposition parameters for silica, siloxane and semiconductor substrates. The optical, spectroscopic and microstructural properties of deposited thin films were compared with bulk glass materials for demonstrating the differences in the properties, which must be optimized for device engineering. Channel waveguides were fabricated after using reactive ion etching technique, up to 2 μm thickness by using CHF3 and Ar gas mixture.

We report on the performance around 1970 nm of a thulium-doped TZNG bulk glass laser pumped by a semiconductor disk laser (SDL) emitting at 1211 nm. A pump-limited maximum output power of 60 mW at 1946 nm was obtained with a measured slope efficiency of 22.4%. The tuning range of 115 nm extended from 1850 nm to 2040 nm. Comparison with a previously reported performance when pumped at 793 nm with Ti:sapphire laser is discussed highlighting the competitiveness of pumping at 1211 nm.

Pulsed laser deposition (PLD) technique has been employed to fabricate glassy films based on the Er 3+ doped oxyfluoride lead-silicate glasses. Glassy films have been produced at temperatures between 300 and 400 °C with O 2 pressures ranging from 25 to 175 mTorr. The film microstructure appears to be determined mainly by substrate temperature. The film refractive index increases with higher temperatures and lower O 2 pressures. The photoluminescence intensity of Er 3+ ions and lifetime are very much dependent on the film microstructure and defects. Fewer fabrication defects and less porous films produce stronger fluorescence intensity and longer lifetime of Er 3+ ions. At an optimized temperature and O 2 pressure, the Er photoluminescence properties of the film can be reproduced and are very close to those of target glass. Consequently the work reported here suggested a good candidate for further investigation as a thin film material for EDWA.

Judd-Ofelt analysis is performed on measurements of bulk samples of Tm3+- and Ho3+-doped tellurite glass from which the host-dependent Judd-Ofelt intensity parameters are extracted. These have then been used to calculate the radiative rates and branching ratios in this particular material system. A rate-equation approach is then used to model an experimentally realized ~2.1 μm Tm3+/Ho3+ codoped tellurite fiber laser and extract values of the energy transfer and upconversion rate parameters in TeO2-ZnO-Na2O (TZN) glass. Excellent agreement is found between simulated and experimental data, which indicates the validity of the approach.

A rate equation approach is used to model an experimentally realized ~ 2 mum Tm3+-doped tellurite fiber laser utilizing an in-band pumping scheme (3H6 rarr 3F4) . Excellent agreement between the theoretically predicted and experimentally measured slope efficiency is obtained. It is shown that in order to achieve agreement between the predicted and measured thresholds it is important to include cross-relaxation mechanisms with the 3H4 level, even with the in-band pumping scheme. By fitting the results of the model with level lifetime measurements and the threshold pump powers we have extracted the cross-relaxation parameters of Tm-doped tellurite glass.

The spectroscopic properties of Sm 3+ -ions in tellurite, fluorophosphate, and fluorine-modified silicate glasses are examined under the excitations at 488 nm (Ar + ion laser) and 1060 nm laser. The effect of dopant ion and glass–host interaction, branching ratio of transitions and line shapes of emission lines in the visible region are discussed in view of the ionicity and covalency of hosts. The lifetimes of metastable levels are also reported and the results are explained for designing the visible and UV laser hosts.

We present, for the first time, laser emission in the range 1.910–1.994 μm in Tm3+/Yb3+-doped tellurite fibre when pumped using an Yb3+-doped double-clad silica fibre laser operating at 1.088 μm. With this pump scheme there was strong pump excited state absorption (ESA) which caused upconversion emission at 800 nm and 480 nm due to the Tm3+: 3H4 → 3H6 and Tm3+: 1G4 → 3H6 transitions, respectively. This strong ESA limited the maximum slope efficiency to 10% with respect to absorbed pump power, and the maximum output power to 67 mW. This is however the highest output power which has been achieved in a tellurite fibre laser so far. The lowest observed threshold was 114 mW for a 22 cm long fibre and a 90% reflective output coupler. Further power scaling was limited due to thermal damage at the pump end of the fibre. The optimum fibre length for this arrangement was around 16 cm but lasing was achieved in lengths ranging from

We report the results of emission and amplification in Tm 3+ - and Er 3+ -fibers for signal gain in the 1460–1600 nm region, which covers a large part of S-, C- and L-bands of silica fiber optical communication networks. The paper explains the mechanism for alleviating the pump-excited absorption in Er 3+ -doped and Tm 3+ -doped tellurite fibers for maximizing the pump inversion efficiency at 980 nm using the co-dopants and via the structural modification of TeO 2 glass by incorporating a high phonon energy oxide namely, B 2 O 3 . The spectroscopic data and gain bandwidth of Er-doped fibers are reported in the C- and L-bands. To date the measured maximum relative gain in short fibers of 5–10 cm in length in C- and L-bands are: 30 dB and 15 dB, respectively. By comparison the internal gain in a 20 cm long Tm/Yb ion co-doped fiber pumped with a 980 nm source was 7 dB.

The paper explains the significance of rare-earth (RE) ion-glass host interaction for engineering waveguide devices, which can potentially bring together short fibre or planar waveguides with a single pump source and filters together for designing a fully integrated photonic structure. In this paper we review and exemplify new results in the light of the ion-host interactions in Sm3+-, Er3+-, Tm3+- and Ho3+-doped tellurium and fluorosilicate oxide hosts for photoluminescence analysis at visible, near-IR, and mid-IR wavelengths. The emphasis in this paper is to exploit currently available fibre-pigtailed 980 nm and multimode high-wattage 800 nm pumps for both up and down conversion schemes. Potential applications of these integrated devices are also explained.

Innovation in integrated photonics and associated fields is imperative with looming bottlenecks in the existing internet infrastructure due to rapidly increasing demand, across society and industry, for greater bandwidth and data access. A priority in this field is the development of a monolithic photonic integrated circuit (PIC), simplifying the design, manufacture and material requirements of current devices, with reduced cost, power and footprints. Furthermore, an improved efficiency and performance is highly sought after as this market anticipates explosive growth. Typically the key components are often made through disparate methods, and then packaged together for a final device. This creates an exciting opportunity for a novel platform technology to overcome such limitations and enhance existing capabilities while opening up new frontiers in device design and complexity.

This book covers various technological aspects of sustainable energy ecosystems and processes that improve energy efficiency, and reduce and sequestrate carbon dioxide (CO2) and other greenhouse emissions. Papers emphasize the need for sustainable technologies in extractive metallurgy, materials processing and manufacturing industries with reduced energy consumption and CO2 emission. Industrial energy efficient technologies include innovative ore beneficiation, smelting technologies, recycling, and waste heat recovery. The book also contains contributions from all areas of non-nuclear and non-traditional energy sources, including renewable energy sources such as solar, wind, and biomass. Papers from the following symposia are presented in the book: Energy Technologies and Carbon Dioxide Management Recycling and Sustainability Update Magnetic Materials for Energy Applications V Sustainable Energy and Layered Double Hydroxides

The Er 3+ –Eu 3+ -codoped tellurite fibre was pumped at 800 nm (CW) using a Ti–sapphire tunable laser source. The emission spectra at 592 and 613 nm, both attributed to Eu 3+ transitions from 5 D 0 → 7 F 1 and 5 D 0 → 7 F 2 , respectively, were recorded at room temperature. Although the upconversion fluorescence from the Er 3+ : 4 S 3/2 level is well known, the observed efficient energy transfer from the Er 3+ :( 2 H 11/2 , 4 S 3/2 ) levels to the Eu 3+ :( 5 D 1 , 5 D 0 ) levels is not known in the literature. The calculated energy transfer efficiency is approximately 20%. The observed visible emissions point out that the Er 3+ –Eu 3+ -codoped tellurite fibre is a potential host material for designing a 589 nm laser for satellite communication and a compact 613 nm fibre laser for medical applications.

The tellurium oxide (TeO2) glasses are unique for their exceptionally large solubility for rare-earth metal ions. The paper discusses various structural, thermal, and spectroscopic properties, essential for fibre and waveguide design. Low-loss fibre fabrication requires an understanding of a relationship between the glass structure, thermal properties, e.f the glass transition, crystallisation, and melting temperatures, and the viscous relaxation. We discuss the properties of tellurium oxide glasses modified by the addition of sodium and zinc oxides, and their vibrational properties are characterised by Raman and infrared spectroscopy. The Raman spectra of these glasses show a range of structural units, namely TeO3, TeO3+°, and TeO4. The processes of tellurite glass preform and fibre fabrication are described in detail. The spectroscopic properties of rare-earth metal ion dopants (Er3+, Tm3+, and Nd3+) are specially discussed for designing broadband fibre and waveguide amplifiers, covering nearly 400 nm wavelength for both coarse (C-) and dense (D-) wavelength division multiplexing (WDM) systems. We demonstrate the usefulness of such fibres in designing ultra-short fibre waveguide amplifiers, which are capable of yielding large gain, e.g. in Er3+-ion doped tellurite fibres larger than 30 dB internal (or relative) gain in the small-signal regime is possible in the C-band region.

Tellurium oxide glass hosts have exceptionally large solubility for RE-ions. In this paper, the relationship between the host glass composition and spectroscopic properties of Er 3+ -doped and Tm 3+ -doped tellurite glasses and fibres has been examined in detail. In particular, the effect of compositional modification on the line-shapes of the transitions: 4 I 13/2 → 4 I 15/2 in Er 3+ -doped and 3 H 4 → 3 F 4 in Tm 3+ -doped tellurite glasses is analysed and discussed. The presence of co-dopants, namely Tb 3+ and Ho 3+ ions in Tm 3+ -doped glasses on the lifetimes of the upper ( 3 H 4 ) and the lower ( 3 F 4 ) levels have also been discussed for shortening the lifetime of the transition between the 3 F 4 level and the ground state in thulium. The spectroscopic properties of Nd 3+ -doped glasses for designing amplifiers operating in the 1330- to 1370-nm region has also been explained for demonstrating a continuous gain spectrum from 1310- to 1610-nm. The fibre loss measurements demonstrate that the Er-doped fibres have less than 880 dB km –1 attenuation in the 1200- to 1400-nm range. An explanation is given to determine the suitability of such RE-doped tellurite fibres for designing broadband amplifiers.

The present investigation discusses the advantage of using RE-ion-doped (Nd3+, Tm3+, and Er3+) TeO2 glasses for developing fiber and planar broadband amplifiers and lasers. The spectroscopy of RE-ion-doped fibers and glasses is discussed along with the thermal properties of glass hosts. The results of emission from the 3H4 level in single-mode Tm3+-doped tellurite fiber show that the emission band overlaps with Er3+ emission from the 4I13/2 level and Nd3+ emission from the 4F3/2 level in silicate and tellurite glasses, thereby enabling the development of amplifiers and lasers between 1350 and 1650 nm. Recent results using Z-scan measurements of nonlinear refractive index and absorption demonstrate that the third-order nonlinearity in undoped TeO2 glasses is of the order of 2 × 10−15 to 3 × 10−15 cm2·W−1 between 1300 and 1550 nm. These results are briefly discussed in view of an amplifier operation combined with ultrafast all-optical switching.

Tungsten–tellurite glass is proposed as a host for broadband erbium-doped fibre amplifiers (EDFA). The spectroscopic properties of Er 3+ -doped tungsten–tellurite glass are described, and a broad 1.5 μm emission spectrum of 85 nm FWHM is demonstrated. The suitability of tungsten–tellurite glass as a host for EDFA and its advantages over tellurite are discussed.

A comparative study of the spectroscopic properties at 1.5 μm of erbiumdoped fluoride and tellurite glasses has been performed. Emission in the third telecommunications window has been observed upon excitation at 514.5 nm and the lifetime of the 4I13/2 level has been measured. Infrared-to-visible upconversion emission upon continuous-wave laser excitation at 976 nm has been detected in the different hosts. The upconversion results in green and red emissions, whose intensity has a quadratic dependence on the excitation power. Lifetime measurements have been performed in order to clarify the contributions of excited-state absorption and energy transfer to the upconversion process.

We have demonstrated a high-performance Er3+/Ce3+ codoped tellurite fiber amplifier and tunable fiber laser using a dual-pumping scheme. The short 22-cm Er3+/Ce3+ ion codoped fiber exhibits a net gain of 28 dB at 1558 nm, a wide positive net gain bandwidth of 122 nm, and a noise figure of 4.1 dB. Finally, a widely tunable Er3+ /Ce3+ codoped tellurite fiber ring laser with a tuning range of 83 nm is demonstrated.

We demonstrate the simultaneous growth of multiple optically functional crystalline structures through a complex implantation and diffusion process. This includes ZnTe, ZnO and as-yet undefined silica crystallites doped with Er 3+ or Tm 3+ which are each characterized optically and structurally.

7 pags. ; 3 figs. ; 1 tab. ; OCIS codes: (130.3120) Integrated optics devices; (140.3390) Laser materials processing; (130.2755) Glass waveguides; (160.2750) Glass and other amorphous materials; (320.7130) Ultrafast processes in condensed matter, including semiconductors., We report on a strong cross migration of ions in a Tellurite (Te) based glass to form waveguides using a high repetition rate femtosecond laser. The tellurite glass matrix was modified using oxides of P, Na and Zn elements of which Te and Na ions play an important role to form waveguides upon laser irradiation. Tellurium was observed to migrate causing a positive index change zone whereas sodium cross migrates to the tellurium deficient zone forming a relatively low index change region. We have used micro-Raman analysis to scan across the waveguide cross-section to understand the state of the glass network and the relation between ion migration and glass densification for waveguiding. We have found that there is an increase in TeO3 units and reduction of TeO4 units in the Te rich zones enabling densification. This work will help guide the new commercial glass manufacturing industries that aim at producing mid-infrared transparent glasses like tellurite, tellurides and chalcogenides for the production of waveguide based devices. © 2014 Optical Society of America., This work was partially supported by the Spanish Ministry of Economy & Competitiveness (TEC2011- 22422 & TEC2012-38901-C02-01) & Spanish Ministerio de Educacion y Ciencia (MAT2010-16161). TTF acknowledges the support of the JAE-CSIC Program co-funded by the European Social Fund.

High-refractive index chalcogenide and heavy-metal oxide glasses have been developed recently for their application as all-optical switching devices in telecommunication networks. Depending upon the nature of electromagnetic phenomena, the switching speed may vary between milliseconds in a rare-earth doped glass and femtoseconds for surface plasmon relaxation in a nano-scale dispersion of metal particles in glasses.

Fluoroaluminate glass was investigated for a Pr 3+ -doped fibre laser at 589 nm using the ( 3 P 1 + 3 P 0 )→ 3 H 6 transition. Enhanced emission at 589 nm was obtained by thermally populating the 3 P 1 level. Results indicate that lasing at 589 nm is possible in fluoroaluminate glass at elevated temperatures.

A Nd3+-doped 1.3 μm fiber amplifier has the potential to be an efficient, high-gain device. A major problem to overcome is the long wavelength of the gain spectrum. In the majority of Nd3+-doped glasses the gain is shifted out of the second telecom window as a result of long-wavelength emission and signal excited-state absorption (ESA). In this article we present new fluoroaluminate glasses developed as hosts for the 1.3 μm Nd3+-doped fiber amplifier. Nd3+ emission peaks below 1320 nm were demonstrated in bulk glasses. Gain in the 1310–1320 nm region was measured in unclad fibers, with evidence of significantly reduced ESA. Another serious problem in amplifier design lies in overcoming the competing amplified spontaneous emission (ASE) at 1050 nm. We discuss ASE filtering using in-fiber Bragg gratings and present results supporting its feasibility. The article also examines thermal and viscous properties of matched core and cladding glasses in relation to preform and fiber fabrication.

The Boson peak in the Raman spectra of glasses is an ubiquitous feature. We show that doping a series of fluoride, tellurite and sulfide glass compositions with rare-earth ions, such as Pr 3+ , Dy 3+ , Nd 3+ , Ce 3+ , at concentrations between 1000 and 10,000 ppm, increases the amplitude of the Boson peak as compared to the respective undoped glasses. Further addition of rare-earth ions results in saturation and even reduction of the Boson peak ascribed to clustering of dopants and/or devitrification of glass host. Prolonged irradiation of photorefractive sulfide glasses with near-bandgap laser light also results in an increase of the Boson peak. A model is suggested for changes in the intensity and position of the Boson peak with glass composition, doping level, and after prolonged irradiation of photorefractive glasses. We propose that the presence of non-bridging anion atoms, such as F, O or S, (or anion atoms having strained bonds with increased polarizability), determines the Boson peak, as well as the solubility of rare-earth ions in glasses.

We demonstrate laser action from a waveguide fabricated in an Er:Yb-doped silicate glass using femtosecond laser inscription. Waveguides were fabricated using a diode-pumped Yb:glass oscillator at a 600-kHz repetition rate. The multiscan technique was used to control the waveguide cross section. Textbook threshold characteristics are observed for both 980 nm and dual-wavelength excitation.

A channel waveguide is fabricated inside an erbium-doped oxyfluoride silicate glass sample using femtosecond pulses in the low repetition rate regime. The waveguide cross section is controlled using the multiscan fabrication technique. The 1.85-cm-long waveguide exhibits a total background insertion loss of 4.3 dB when coupled to Corning SMF-28 fibers. Under the maximum available pump power, the device exhibits an internal gain of 1.7 dB at 1537 nm.

The wavelength range between 3 - 4 μm is a highly sensitive window for environmental monitoring, bio medical application and spectroscopy. Glasses though can offer high bandwidths are often difficult to maneuver in mid IR wavelengths due to its high phonon energies. Tellurite glass have low phonon energies with high transparency up to 6 - 7 μm. We present the successful production of channel waveguides in a rare-earth doped tellurite glass obtaining active operation within the 3 - 4 μm wavelength window.

We present the fluorescence spectroscopy of a range of Dy3+ doped tellurite (TeO2) and germanate (GeO2) glasses and compare with Dy3+ doped ZBLAN glass. When excited using an 808 nm laser diode, Dy3+ ions emit radiation at around 3 μm from the 6H13/2→ 6H15/2 (3500 cm -1) energy level transition, which has been exploited in Dy 3+ doped fluoride fibre lasers. When Dy3+ is doped into TeO2 and GeO2 based glasses, the fluorescence from the 6H13/2→ 6H15/2 transition is shown to be broader and red-shifted compared to that in ZBLAN glass. Mid-IR ASE from a fs laser inscribed Dy3+ doped tellurite glass waveguide is also presented. The results of Dy3+ mid-IR fluorescence spectroscopy and the potential of oxide glasses as mid-IR sources are discussed. © 2013 Astro Ltd.

Chromium is mainly used for the production of stainless steel, in electroplating, as pigments and in leather and refractory industries. The natural resource of chromium is the chromite ore, which is a spinel (Fe2+, Mg)[Cr,Al,Fe3+]2O4, and is often present with gangue minerals such silicates. Traditionally chromium chemical extraction has been carried out with alkali and CaO roasting, which led to major environmental issues due to CaCrO4/Na2CrO4 release.

The low phonon energy of germanium sulphide glasses makes them ideal candidates as hosts for 1.3µm fibre amplifier applications. However, the GeS2 glass host suffers from a major drawback of poor rare-earth ion solubility. In an efficient device, the solubility of Pr ions has to be enhanced, without adversely affecting either the thermal or the spectroscopic properties of the glass. In the present investigation, we report the synthesis and optical properties of modified GeS2-based chalcohalide glasses with excellent thermal characteristics suitable for drawing low-loss optical fibres.

An investigation is presented of thermal and optical properties of core and cladding cadmium halide glasses as related to the design of Pr 3+ -doped 1.3 μm fibre amplifier. The core glass is a pure halide composition, while the cladding glass contains phosphate. Thermal and optical properties of core and cladding glasses were measured, including: the characteristic temperatures and time-temperature-transformation curves, viscosity, expansion coefficient, refractive index, infrared cut-off, Raman spectra, and Pr 3+ metastable lifetimes. The variation of the cladding glass properties with phosphate content was measured. It is shown that phosphate chains in the glass structure improve glass stability.

Phosphate glasses can dissolve high concentrations of rare earths and have excellent spectroscopic properties making them useful solid-state laser materials. Solid-state lasers doped with different rare-earth ions find applications in a wide range of LIDAR (Light Detection and Ranging) and sensing applications; phosphate glasses are useful host materials for many applications in the visible and near-infrared spectral regions. For example, trivalent erbium (Er 3+ ) doped phosphate glasses operate at the eye-safe wavelength of 1.54 μm and are used for range finding and sensing applications. Tm 3+ doped solid-state lasers operating at ~ 2 μm can be used for wind-shear and turbulence monitoring. Similarly, Nd-doped metaphosphate glasses are the preferred gain medium for high-peak-power lasers used for fusion energy research because they can store optical energy at greater densities than other glass-types and can be fabricated in large sizes with high rare-earth ion concentration. This paper discusses issues affecting glass quality, with particular focus on defect formation, especially crystallisation. Avoiding crystallisation during processing is essential to form high quality laser cavities. The work presented explores some of the factors controlling these defects including contamination during melting. The crystallisation behaviour of the glass was investigated for several different phosphate glass compositions and different melting conditions, including melting duration, temperature and crucible material.

We present the fabrication and characterisation of Dy 3+ -doped tellurite glasses and waveguides for applications in the mid -IR. The low phonon energy and large rare -earth ion solubility of tellurite glasses, as well as having infrared transmission ranges up to >5 µm, make them promising candidates for new mid -IR solid -state laser host mate rials. This paper presents recent achievements in the fabrication of tellurite glasses, glass characterisation and rare -earth ion spectroscopy which is compared to other glass hosts relevant to the mid -IR such as fluoride glasses. When excited with an 808 nm laser diode source, Dy 3+ doped tellurite bulk glasses exhibited very broad fluorescence from the 6 H 13/2 - 6 H 15/2 transition which extends from 3 µm to 3.6 µm FWHM compared to 2.9 µm to 3.1 µm in Dy 3+ doped ZBLAN glass. This broad and red -shifted fluores cence band in tellurite glass may find use in LIDAR and sensing applications as it coincides with an atmospheric transmission band, compared to the ~3 µm emission of Dy

Optical and spectroscopic data and calculations in support of an efficient 1.3 µm amplifier in Pr3+-doped cadmium mixed halide glass host are presented. We find that the dominant parameter affecting the amplifier gain is the lifetime (325 µm) of the Pr3+-1G4 state. The long lifetime is the direct consequence of a decreased multiphonon decay rate in this low-phonon-energy glass host. We predict gain in excess of 30 dB for 100 mW pumping in low loss fibres, and for background loss of 1 dB/m, gain figures are as high as 15-20 dB.

Thermally stable ZrF4-based glasses with Pr3+ :1G4 →3H5 fluorescence lifetimes longer than that of conventional ZBLAN glass have been developed. In addition to lifetime measurements the transmission characteristics, absorption spectra, 1.3 μm emission spectra and refractive indices of these novel glasses were determined. Fourier transform infrared reflectance and phonon sideband spectra suggest that the prolonged lifetimes are due to a reduction in the phonon energy in the vicinity of Pr3+ ions and a decrease in the electron-phonon coupling strength.

A large numerical aperture core-cladding structure is required for drawing single-mode fibers for the fabrication of Pr-doped 1.3 μm optical fibre amplifiers. Geometrical restrictions on fibres and hence on preforms are important for confining the optical pump power into a small core volume (3–5 μm diameter) in order to promote efficient amplification at 1.3 μm. Cadmium mixed halide glasses exhibiting lower phonon energies than the standard fluorozirconate compositions have been designed, and their optical and thermal properties are reported. The refractive indices of core and cladding glasses have been measured as a function of wavelength in the visible region and their values have been extrapolated to the signal and pump wavelengths. The mismatch stresses in the core-cladding structure at room temperature have been estimated from the measured expansion coefficient data.