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The optical properties of praseodymium doped glasses have attracted considerable attention recently for their potential application as a 1.3 micron optical amplifier. As a result novel glass compositions are being developed and known glass forming systems are being revisited in the quest for a low-phonon energy glass which may lead to an efficient amplifier. We report here on our spectroscopic evaluation of a series of low-phonon-energy glasses based on halides and sulphides. These results, though driven by the desire for a practical amplifier, provide insight into the application of these glasses not only for telecommunications applications, but also an understanding of the overall optical properties of a low-phonon-energy glass. Using Raman spectroscopy. the vibrational characteristics of the glass host are determined. These results are confirmed through infrared measurements and with phonon sideband measurements. In this way, the non-radiative properties of the rare earth doped glass can be predicted. Absorption measurements across the visible and infrared allow evaluation of the intrinsic loss of these glasses when in fibre form, as well as providing an indication of glass purity. Fluorescence of Pr3+-doped glasses, through excitation of the 3P0, 1D2 and 1G4 levels, is measured along with the fluorescence lifetimes. These radiative properties arc compared to those predicted by a Judd-Ofelt analysis, which has been performed on all glasses. In this way, this work provides an overall spectroscopic evaluation of the optical properties of low-phonon-energy glasses, leading the way towards a practical device.

We report on recent progress towards the application of both mixed cadmium halides and sulphide-based glasses as host materials for a Pr3+-doped 1.3 micron optical fiber amplifier. Both of these materials offer the potential for higher gains than can be currently achieved in a Pr3+-doped ZBLAN fiber. Fundamental glass properties, including optical and thermal characteristics, are compared. Losses of these glasses in fiber form have been estimated and spectroscopic measurements are summarized. From these studies we show that quantum efficiencies over an order of magnitude higher than those demonstrated with Pr3+-doped ZBLAN amplifiers are in principle obtainable. Measured efficiencies of 11% and 52% for the Cd halide and Ga sulphide, respectively, are achieved, while 25% and 80% are predicted. Numerical modelling allows comparison of the expected amplifier performance. Thermal analysis has identified the challenges which remain for the drawing of single mode fibers and the results of preliminary fiber drawing trials are described. The relative merits of each of the various glasses are considered and the challenges before a practical amplifier is achieved are outlined.

The co-reduction of rutile (TiO 2 ), boron oxide (B 2 O 3 ), and silica (SiO 2 ) with carbon were carried out in order to form TiN, TiC, BN, B 4 C or SiC dispersion in a titanium boride matrix. The reduction reaction was studied between 1473 and 1823K. The effect of processing parameters such as the composition, partial pressure of gas, and heating rate on the formation of a composite microstructure are discussed. The reactivity of carbon appeared to bo one of the most significant factors in determining the microstructures formed. The governing reaction mechanism to illustrate the above microstructural features are explained. The results are discussed by constructing the phase equilibrium diagram based on the calculated values of the Gibbs free energy of formation (ΔG°) of the phases under consideration. The reduction steps are briefly discussed in the light of development of composite microstructure. The main aim of developing a composite microstructure via in-situ reduction technique is to reduce the mixing cost and health risk associated with ceramic whisker and ultra fine powder handling.

Using experimental measurements of cross-sections and a 1G4 lifetime of 315µs, we have characterised the expected performance of a Pr3+-doped mixed halide fibre amplifier for operation at 1.3µm. Our model predicts a small-signal gain of 20dB for 75mW of pump.

The results of an experimental and theoretical study to compare the attributes of Pr3+-doped sulphide, chloride, mixed halide, fluoride and chlorotellurite glasses for 1.3µm fibre amplifiers are presented. Quantum efficiencies based on measured and calculated radiative and nonradiative rates are presented for each glass together with its 1.3µm fluorescence spectrum and an estimate of its loss.

For the first time, Fiber Bragg grating (FBG) structures have been inscribed in single-core passive germanate and three-core passive and active tellurite glass fibers using 800 nm femtosecond (fs) laser and phase mask technique. With fs peak power intensity in the order of 10(11)W/cm(2), the FBG spectra with 2nd and 3rd order resonances at 1540 and 1033 nm in the germanate glass fiber and 2nd order resonances at approximately 1694 and approximately 1677 nm with strengths up to 14 dB in all three cores in the tellurite fiber were observed. Thermal responsivities of the FBGs made in these mid-IR glass fibers were characterized, showing average temperature responsivity approximately 20 pm/ degrees C. Strain responsivities of the FBGs in germanate glass fiber were measured to be 1.219 pm/microepsilon.

We report spectroscopic and bulk laser performance characteristics for Tm(3+)-doped tellurite glasses when used as gain media operating around 1.9 microm. Two glass hosts studied are TZN and TZNG and their performances have been compared. In each case, well-characterized cw laser performance was obtained and this has been related to detailed spectroscopic measurements of the important lasing parameters of the laser transitions around 1900 nm when pumped at 793 nm. The maximum output power achieved was 124 mW from the TZNG sample with an associated slope efficiency of 28 % with a tuning range of 135 nm. Efficiency and loss analyses yielded a calculated maximum attainable efficiency of 48 % in Tm(3+):TZN compared to 28 % for the TZNG host.

Laser emission in the range of 1.88-1.99 μm from a Tm3+-doped tellurite fiber is demonstrated when pumped with a diode-pumped Er3+/Yb3+-doped silica fiber laser operating at 1.57-1.61 μm. This pump source excites the Tm3+ ions directly into the F43 upper laser level and yields an output power of 280 mW with a slope efficiency of 76% in a 99%-12% laser cavity arrangement and a 32 cm long fiber. This result is very close to the Stokes efficiency limit of ~80%. This is, to the authors' knowledge, the first demonstration of high efficiency lasing in a tellurite fiber at wavelengths longer than 1.56 μm.

The infrared emission spectra and decay lifetimes of Tm(3+)-doped and Tm(3+)-Ho(3+), Tm(3+)-Yb(3+) co-doped tellurite fibres were measured using 808 nm and 978 nm diode laser pump sources in the range 1.35 mum to 2.2 mum. The spectra were compared with varying fibre lengths and core diameters. Tm(3+)-doped fibre shows strong emission at ~1.8 mum and when co-doped with Ho(3+), energy transfer results in strong Ho(3+) fluorescence at ~2.0 mum. These fibres show promise for compact mid-IR fibre laser sources.

By directly writing waveguides inside bulk erbium-doped oxyfluoride silicate glass using a focused femtosecond pulse train, we demonstrate the potential for the fabrication of especially broadband, compact telecommunications optical amplifiers operating in the c-band (1529–1561nm). Characterization results include coupling losses to single-mode fiber, waveguide losses, and gain measurements. Clear relationships between the fabrication pulse energy and the waveguide losses and coupling losses are also established.

We report gain measurements in Tm(3+)/Yb(3+)-codoped tellurite glass fibers in the 1460-1530-nm region using a conventional 980-nm pumping scheme. The gain spectrum is dependent on the geometry of the fiber and the length owing to the superfluorescence upconversion pump scheme.

Using reactive pulsed laser deposition, a thin film of erbium-doped oxyfluoride-silicate glass is deposited onto a fused silica substrate. Rib waveguides are fabricated from this film using reactive ion etching. The fabrication and characterisation of these waveguides are summarised. As a result of various characterisation experiments described here, it is concluded that close to stoichiometric transfer of material from the bulk to the film has been achieved. It is concluded, however, that strong quenching mechanisms are present in the film, significantly affecting the magnitude of the 4I13/2→4I15/2 transition fluorescence lifetime.

The visible and near infrared emission spectra of Er(3+)-Tm3(3+)-codoped tellurite glasses and fibres were measured with the excitation of an 800 nm laser. A broad emission extending from 1.35 mum to 1.6 mum with a full width at half-maximum (FWHM) of ~160 nm was recorded in a 24 cm long 0.2 wt% Er(2)O(3) and 1.0 wt% Tm(2)O(3) codoped tellurite fibre. Energy transfer between Er(3+) and Tm(3+) play important roles in the luminescence mechanism. These results indicate that Er(3+)-Tm(3+) codoped tellurite fibre could be a promising material for broadband light source and broadband amplifier for the wavelength-division-multiplexing (WDM) transmission systems.

The gain spectra in Er3+ doped and Er3+/Ce3+ codoped tellurite glass fibres have been compared at 980 nm pump wavelength. The observed gain at 1.53 µm increased from 16 to 31 dB in a 12 cm long Er3+/Ce3+ codoped fibre, and the gain changed less than 2 dB with a 20 dB variation in signal power.

A new GeS2-based chalcohalide glass was synthesized by the melt-quenching technique for nonlinear optical applications. A large glass-forming region was defined, and a wide infrared transmission was measured. Marked optical third-order nonlinearity was measured (n2≈7.5×10-5 cm2/GW), making this glass one of the best candidates for ultrafast nonlinear optical applications. All-optical switching in the second telecommunication window (λ=1.31 μm) by control of the optical pulse intensity in a twin-core-fiber directional coupler was numerically modeled, and a crossover length of 9.25 mm was calculated.

Calcium-calcium fluoride melt was used to remove phosphorus from the ferro-chrome alloy (64.5 wt% Cr, 0.15 wt% P) during electro slag refining process. The effect of atmosphere and deoxidisers, viz. Al, Fe–Mo and misch metal were also studied during dephosphorisation reaction. The thermodynamic properties of Ca–CaF2 melt is calculated from a known phase diagram and these results are discussed in relation with the dephosphorisation reaction.

Separation and purification of critical metal ions such as rare-earth elements (REEs), scandium and niobium from their minerals is difficult and often determines if extraction is economically and environmentally feasible. Solvent extraction is a commonly used metal-ion separation process, usually favored because of its simplicity, speed and wide scope, which is why it is often employed for separating trace metals from their minerals. However, the types of solvents widely used for the recovery of metal ions have adverse environmental impact. Alternatives to solvent extraction have been explored and advances in separation technologies have shown commercial establishment of liquid membranes as an alternative to conventional solvent extraction for the recovery of metals and other valuable materials. Liquid membrane transport incorporates solvent extraction and membrane separation in one continuously operating system. Both methods conventionally use solvents that are harmful to the environment, however, the introduction of ionic liquids (ILs) over the last decade is set to minimize the environmental impact of both solvent extraction and liquid membrane separation processes. ILs are a family of organic molten salts with low or negligible vapour pressure which may be formed below 100 °C. Such liquids are also highly thermally stable and less toxic. Their ionic structure makes them thermodynamically favorable solvents for the extraction of metallic ions. The main aim of this article is to review the current achievements in the separation of REE, scandium, niobium and vanadium from their minerals, using ILs in either solvent extraction or liquid membrane processes. The mechanism of separation using ILs is discussed and the engineering constraints to their application are identified.

Critical-size long bone defects represent one of the major causes of fracture non-union and remain a significant challenge in orthopaedic surgery. Two-stage procedures such as a Masquelet technique demonstrate high level of success however their main disadvantage is the need for a second surgery, which is required to remove the non-resorbable cement spacer and to place the bone graft into the biological chamber formed by the 'induced membrane'. Recent research efforts have therefore been dedicated towards the design, fabrication and testing of resorbable implants that could mimic the biological functions of the cement spacer and the induced membrane. Amongst the various manufacturing techniques used to fabricate these implants, three-dimensional (3D) printing and electrospinning methods have gained a significant momentum due their high-level controllability, scalable processing and relatively low cost. This review aims to present recent advances in the evaluation of electrospun and 3D printed polymeric materials for critical-size, long bone defect reconstruction, emphasizing both their beneficial properties and current limitations. Furthermore, we present and discuss current state-of-the art techniques required for characterisation of the materials' physical, mechanical and biological characteristics. These represent the essential first steps towards the development of personalised implants for single-surgery, large defect reconstruction in weight-bearing bones.

Soft pneumatic actuators have been explored for endoscopic applications, but challenges in fabricating complex geometry with desirable dimensions and compliance remain. The addition of an endoscopic camera or tool channel is generally not possible without significant change in the diameter of the actuator. Radial expansion and ballooning of actuator walls during bending is undesirable for endoscopic applications. The inclusion of strain limiting methods like, wound fibre, mesh, or multi-material molding have been explored, but the integration of these design approaches with endoscopic requirements drastically increases fabrication complexity, precluding reliable translation into functional endoscopes. For the first time in soft robotics, we present a multi-channel, single material elastomeric actuator with a fully corrugated design (inspired by origami); offering specific functionality for endoscopic applications. The features introduced in this design include i) fabrication of multi-channel monolithic structure of 8.5 mm diameter, ii) incorporation of the benefits of corrugated design in a single material (i.e., limited radial expansion and improved bending efficiency), iii) design scalability (length and diameter), and iv) incorporation of a central hollow channel for the inclusion of an endoscopic camera. Two variants of the actuator are fabricated which have different corrugated or origami length, i.e., 30 mm and 40 mm respectively). Each of the three actuator channels is evaluated under varying volumetric (0.5 mls-1 and 1.5 mls-1 feed rate) and pressurized control to achieve a similar bending profile with the maximum bending angle of 150°. With the intended use for single use upper gastrointestinal endoscopic application, it is desirable to have linear relationships between actuation and angular position in soft pneumatic actuators with high bending response at low pressures; this is where the origami actuator offers contribution. The soft pneumatic actuator has been demonstrated to achieve a maximum bending angle of 200° when integrated with manually driven endoscope. The simple 3-step fabrication technique produces a complex origami pattern in a soft robotic structure, which promotes low pressure bending through the opening of the corrugation while retaining a small diameter and a central lumen, required for successful endoscope integration.

We demonstrate simultaneous implantation of Tellurium, Zinc, Sodium and Erbium ions in silica glass via fs-PLD. 1.3μm deep uniform diffusion with Δn max of 0.169 was produced. Process is explained using existing models with experimental verification.

Tellurite glass fibre has great potential for use in near and mid infrared (mid-IR) optics. The high nonlinearity and its excellent transmission properties in the infrared make it an ideal candidate for many linear and nonlinear optical devices (Abedin, 2006). These can be devices for chemical sensing, nonlinear optical signal processing, Raman amplification or mid-IR continuum generation. Tellurite glasses are also an excellent host for rare earth ions with their low phonon energy. In this paper we report on the fabrication and characterisation of a multiple core tellurite glass fibre. Multiple core fibres can offer new device designs such as arrayed fibre lasers and amplifiers, chemical sensors and bend sensors (Flockhart et al., 2003).

Molybdenum disulphide (M0S2) has layered structure and is classed as a transition metal-disulphide (TMD) material. Recently it has drawn significant attention for exploring optoelectronic and photonic properties on sub-nanometre scale, with a potential for accessing quantum interactions [1]. The electronic structure and stoichiometry of TMDs make them distinguishable from the metallic graphene, as the TMDs depict a clear bandgap, as in compound semiconductors [2], which is quite attractive for device engineering and applications in photovoltaic, energy storage, and bandgap engineered light-sources [3]. In this research, the fabrication of undoped and Yb3+-ion doped MoS 2 nanometre (nm)-scale thin films are discussed using femto-second pulsed laser deposition (fs-PLD) and the structural and spectroscopic properties of fs-PLD are compared with liquid-phase epitaxy grown undoped MoS2 films. Such a comparative analysis may offer materials fabrication platform in future for engineering optoelectronic and photonic devices on silica glass and silicon platforms.

We demonstrate laser action from a waveguide fabricated in an Er:Yb-doped silicate glass using femtosecond laser inscription. Single-mode waveguides were fabricated exhibiting a total background insertion loss excluding absorption of only 1.2 dB. Textbook threshold characteristics are observed for both 980 nm excitation and dual wavelength excitation.

We present recent results on the material, spectroscopic and laser properties of a range of Tm3+, Tm3+-Ho3+ and Dy3+ doped tellurium oxide (TeO2) based glasses in the 2-4 μm wavelength region.

We report for the first time, net gain from a channel waveguide fabricated in Er:Yb doped oxyfluoride silicate glass using femtosecond waveguide inscription. Waveguides were fabricated using the multi-scan technique to control the waveguide cross-section.

Angiogenesis is a vital requirement for the formation of healthy tissue and bone; this currently is one of the greatest challenges in the field of tissue engineering. A promising strategy to achieve formation of suitable, intrinsic vasculature is the use of biodegradable microfluidic networks [1]. Pre-seeding the microfluidic medical devices with angiogenic growth factors, stem cells, collagen, specific proteins and bone cells will allow for successful soft tissue and bone regeneration. Biodegradable scaffolds may be constructed by a numbering up operation where several layers of microfluidic medical devices are compiled together via a multi-scale design; thus enabling scaffolds to be moulded into specific shapes and sizes depending upon the patients requirements. The micro-channels would support better cell proliferation aiding in enhanced attachment between implants and biological material while the enhanced capillary forces will allow for the circulation of the nutritional components which are necessary for the growth of cells.

In this work, we aim to investigate the effect of Fe2+/Fe3+ doping on the laser sintering of calcium phosphate minerals for the fabrication of bone scaffolds. The laser-matter mechanisms and the biological response are discussed.

We present the results of optical characterisation experiments conducted on erbium doped waveguide amplifiers (EDWAs) fabricated in novel erbium doped bulk glasses using femtosecond pulses to modify the refractive index of the glass.

An IR femtosecond pulsed laser was used for micropatterning of biomineral containing chitosan membranes, aiming to enhance bone mineralization and angiogenesis. Pre and post irradiation materials have been characterized with XRD, SEM and spectroscopic techniques.

Acid erosion and wear of natural enamel leading to sensitivity of teeth is a common condition amongst large population worldwide. It is a lifestyle related condition, resulting from the progressive loss of mineral phase from enamel surface. Unlike bone, the dental enamel is a dead tissue and cannot regenerate itself and it must be restored for preventing exposure of softer dentinal tubules and nerves [1], which is the root cause of pain. At present there is no long-term treatment except the daily use of brand tooth pastes, regular use of which provide some protection. Consequently, the dental condition globally is on rise.

The dissolution and chemical properties of vanadium, zirconium, and niobium in rutile lattice are analyzed by comparing the octahedral site preference energies, with respect to Ti4+ ion in solvent phase. The oxides are often present in rutile lattice and interfere in achieving the quality of pigment grade TiO2 due to favourable Gibbs energy for dissolution in the solvent rutile matrix. Binary mixtures of V2O5 – TiO2; Nb2O5 – TiO2 and ZrO2 – TiO2 with compositions of 80, 85, 90, 95 and 97 wt% TiO2 were made, pelletized and sintered at 1100 oC for 24 hours. The solid-solution mixtures were then cooled and leached in 2M NaOH for 3 hours at 60 oC. Phase and lattice parameter characterizations, and microstructural and compositional analyses were then carried out using X-ray diffraction and SEM/EDX, respectively. The leachates were analysed by Atomic Absorption Spectroscopy, using which the solute dissolution model for oxides were investigated.

The large area deposition and synthesis of 10 mm × 10 mm atomically thin Yb³⁺‐doped MoS₂ films by femtosecond pulsed laser deposition on a silica glass optical platform for device applications are demonstrated for the first time. The presence of Yb³⁺‐ion doping is confirmed using photoluminescence (PL), X‐ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The Yb³⁺‐doped MoS₂ films, when excited with a 976 nm laser, exhibit room temperature PL with a peak at 1002 nm. The XPS and Raman spectroscopic analyses of the Yb³⁺‐doped and undoped films show that the deposited films are a mixture of 2H‐ and 1T‐MoS₂ after postdeposition annealing at 500 °C. The density functional theory analysis shows that the 1T phase is metastable by +77 kJ (≈0.8 eV) mol‐1, when compared with the 2H state at 0 K. Ultrafast transient nonlinear optical spectroscopic measurements prove that the saturable absorption of undoped MoS₂ is significantly modified after Yb³⁺‐ion doping, by displaying dopant‐host structure charge transfer. The complex transient absorption line shape shows a combination of bleach (negative) signals at the A (670 nm) and B (630 nm) exciton energies, and a strong induced absorption below the A exciton level. The results presented herein provide critical insight in designing novel rare‐earth‐ion doped 2D materials and devices.