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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.

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.

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.

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.

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.

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.

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.

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.

We report the simultaneous implantation of metal ions namely Te4+, Zn2+ and Na+ along with the rare-earth ion Er3+ using a femtosecond laser ablation and deposition process. Planar waveguide structures with 1.3 μm deep uniform diffusion with a maximum refractive index change (Δn max ) of 0.169 was produced in silica. This novel process will be explained using existing models with experimental verification. It has a potential to produce new materials and structures which are otherwise impossible to achieve via conventional glass and thin-film fabrication techniques. The unique possibility of diffusing rare earth ions opens new realm of photonic devices engineering.

This review focuses on the engineering of the structural, thermal, optical and spectroscopic properties of tellurium oxide (TeO2) glasses for their applications in fibre optic and waveguide devices. Unlike silica optical fibres, tellurium oxide glass fibres and light waveguides support propagation of light beyond ∼2 μm, where silica fibres become opaque. Silica fibres also have limited solubility for rare earth oxides due to silica’s structure, which is where tellurium oxide fibres and light waveguides can offer significant opportunities to engineer novel lasers and amplifiers for integrated optics. In this review, we compare the structural properties of TeO2 based glasses, modified by incorporating alkali, alkaline earth, and other oxide compounds. Based on Raman, UV, visible and infrared spectroscopic data, the structural aspects of tellurite glasses are discussed. The effects of compositional modification on the thermal and viscous flow properties are also compared and related with the resistan...

The limited solubility of rare-earths in silica hampers the development of loss-compensated photonic integrated circuits. We report a novel method using femtosecond laser plasma assisted hybrid material integration of rare-earth-doped tellurite with silica, achieving high doping concentration of Er3+ and Yb3+-ions, 1.63 × 1021 atoms.cm−3,without segregation validated by Er3+:4I13/2 lifetime of 9.1 ms. The sequential ablation of two individual rare-earth (Er3+/Yb3+) doped-tellurite glass targets produces an exceptional intermixing of Er3+ and Yb3+-ions extending to the pristine silica with sharp interface. Formation of such homogeneous glass structure with Er3+-Yb3+-ions in a matrix of silica is not possible to realise by conventional methods.

Tellurite based fibers are promising as a nonlinear fiber for supercontinuum source applications in the 2–5 micron wavelength range. These glass fibers possess both a high optical non-linearity as well as low propagation losses if prepared properly. We review recent results.

We report optical guiding and laser action at around 1.9 μm in a Tm3+-doped fluorogermanate glass waveguide fabricated using ultrafast laser inscription. A monolithic laser cavity was constructed by directly butt coupling dielectric mirrors to each facet of the 6.0 mm long Tm3+-doped waveguide. When the waveguide was pumped by a Ti:sapphire laser tuned to 791 nm, laser oscillation was achieved at around 1.91 μm. This waveguide laser exhibited a maximum slope efficiency of 6% and a maximum output power of 32 mW when pumped with 620 mW of incident laser power.

Glasses based on tellurium oxide (TeO 2 ) are well suited to act as host materials for fibre lasers emitting at wavelengths of 2 µm and greater, the spectral region in which optical absorption in silica fibres becomes significant. In particular, tellurite glass has a phonon energy of 600–800 cm−1, significantly less than both silicates and germanates, which enables transmission of wavelengths as long as 5 µm. This low phonon energy also ensures that non-radiative recombination rates are low and the lifetime of excited states of rare earth (RE) dopants are long. Furthermore, tellurite glasses have high refractive indices which both enables high numerical aperture fibres to be fabricated and results in high absorption and emission cross-sections for RE dopants. These high cross-sections coupled with the high solubility of REs in tellurite glass allow lasing to be achieved using only short fibre lengths. Finally, tellurite glass is more stable thermally and chemically than fluoride glass, another fibre laser host material also transparent in this region.

The integration of dissimilar materials such as the glass and semiconductors offers novel opportunities for photonic components engineering. The differing physical and chemical properties of the two types of materials bring about several fabrication challenges. The integration of semiconductor laser sources with silica waveguides [1] and the deposition of GaAs, on glass substrates using pulsed laser deposition (PLD) [2] were experimented with in the past. In this work we report a strategy for fabrication and integration of an Er3+-doped phosphate modified tellurite (PT) glass on a GaAs substrate using PLD under reactive oxygen atmosphere. Reactive ion etching (RIE) process is used to define channel waveguides on the glass-semiconductor integrated thin film.

Preliminary materials results are reported of a study to develop novel fluoride glasses exhibiting maximum phonon energies lower than those of ZBLAN with the objective of realising an efficient optical amplifier for the coveted 1.3 μm wavelength domain. Pertinent material attributes including peak phonon energy, 1 G 4 lifetimes and thermal properties are reported for each glass host.

We report observation of four- and five-photon absorption in the chalcogenide glasses at the telecommunication wavelengths. The nonlinear refractive index is sufficiently large that the optical switching criterion is satisfied.

We report on the spectroscopic characterization, continuous-wave and continuous wave mode-locked laser performance of bulk Tm(3+):GPNG fluorogermanate and Tm(3+)-Ho(3+):TZN tellurite glass lasers around 2 μm. A slope efficiency of up to 50% and 190 mW of output power were achieved from the Tm(3+):GPNG laser at 1944 nm during continuous wave operation. The Tm(3+)-Ho(3+):TZN laser produced a 26% slope efficiency with a maximum output power of 74 mW at 2012 nm. The Tm(3+):GPNG produced near-transform-limited pulses of 410 fs duration centered at 1997 nm with up to 84 mW of average output power and repetition frequency of 222 MHz when was passively modelocked using an ion-implanted InGaAsSb-based quantum well SESAM. Using the same SESAM, the Tm(3+)-Ho(3+):TZN laser generated 630-fs pulses with 38 mW of average output power at 2012 nm. Data analysis of pulses at different intracavity pulse energies provided an estimation of n(2) at 2012 nm of 2.9 × 10(-15) cm(2)/W for the Tm(3+)-Ho(3+):TZN.

Multiple scattering of light in several materials can lead to diffusion and localization of photons resulting in random lasing and it has attracted much interest recently [1,2]. In a low dimensional scattering medium with gain, random lasers can operate with low threshold and higher efficiency. In this work we report the fabrication and operation of a 2-dimensional, tunable random laser requiring very low threshold pump power. Nanoporous glass thin films of high refractive index (∼2) were grown using ultrafast laser ablation of tellurite glass doped with Er3+ ions. The films were characterized for their thickness, effective refractive index, porosity and, scattering strength. The lasing characteristics of the films were carried out using a continuous wave pump laser at 980 nm Low threshold random lasers were obtained with wide tunability in the wavelength region of 1512-1612 nm in a stable and easily reproducible planar slab waveguide structure. The tunability was obtained by varying the angle of collection of laser output from the film surface. Figures la shows the transmittance spectra of the film used for laser experiments and lb show the spectrum of the laser obtained at an angle of collection of 43°. The lasing at various other wavelengths was obtained by the use of films doped with other rare earth ions as well.

The electronic states in trivalent rare-earth ions offer an excellent opportunity for designing efficient fibre and bulk lasers for atmospheric remote sensing and LIDAR technology. The first part of this review article focuses on engineering passive fibres for 2-5 μm transmission. The fabrication of single-mode tungsten tellurite optical fibres from high purity bulk glass rods is described. Fibres with a numerical aperture of 0.1 and core diameter of 10±2 μm have been drawn using suction and rod-in-tube techniques of fibre preform fabrication. Losses of 2.3 dBm -1 at 974 nm have been measured. These fibres are of interest for use as passive transmission fibre or active fibres for lasing in the 2-5 μm spectral region. The use of heavy metal oxides in the fabrication of glass leads to extended infrared transmission. In the 2 nd part of the review we compare the slope efficiencies of Tm 3+ and Tm 3+ /Ho 3+ doped glasses and fibres for 1950-2080 nm lasers using a range of pumping schemes in tellurite and germanium oxide hosts. We also explain the importance of choosing 1950-2080 nm tunable lasers as a pump source for stimulated emission at longer wavelengths.

We report guiding, lasing action and performance characterization at around 1.9 µm from an ultrafast laser inscribed channel waveguide in a Tm3+-doped fluorogermanate glass.

We report on the first demonstration of an optical waveguide amplifier in phospho-tellurite glass providing net gain at 1.5 μm. The device was fabricated using a high repetition rate femtosecond laser and exhibited internal gain across 100-nm bandwidth covering the entire C + L telecom bands.

Recent work in the area of Tm 3+ and Ho 3+ -doped tellurite fibre and bulk glass lasers operating close to 2 μm is re- viewed. Spectroscopic properties of these doped glasses are dis- cussed as well as the relevant pump schemes and energy trans- fer processes involved. Results of continuous wave (CW) and Q-switched Tm 3+ and Ho 3+ -doped tellurite fibre lasers are then presented and discussed. Finally, the results of tellurite bulk glass laser experiments conducted to date are reported.

In this study, we report the fabrication and engineering of an infrared fibre evanescent wave spectroscopic (FEWS) sensor using GeTeSe chalcogenide fibres, which manifests high temperature durability (glass transformation temperature at 260°C) and extended infrared transmission from 1.5 to 18 μm. We also report the methodologies adopted for the fabrication of fibres, including the purification of starting chemicals for high spectral purity, glass melting, quenching and annealing, fabrication of fibre performs. The designed FEWS sensor consists of a 40 cm unstructured GeTeSe fibre coupled with a Fourier transform infrared (FTIR) spectrometer and a Mercury-Cadmium-Tellurium (MCT) infrared detector, and the active sensing length of the fibre is 3 cm. In this paper, we demonstrate the sensing results with various analytes and investigate the sensitivity of this sensor.

The authors report supercontinuum generation in an ultrafast laser inscribed chalcogenide glass waveguide. The waveguides were fabricated using a Yb:glass cavity-dumped femtosecond oscillator with 600- kHz repetition rate. The waveguides were pumped using an optical parametric amplifier tuned to 1500 nm with a bandwidth of 100 nm. The broadest resulting supercontinuum spanned 600 nm (at -15 dB points) from 1320 to 1920 nm. The supercontinuum was generated in the normal dispersion regime, enhancing stability, and exhibits a smooth spectral shape.