Frequency doubling in Ga:La:S optical glass with microcrystals

Second harmonic generation in gallium-lanthanum-sulphide (Ga:La:S) and GeS2+Ga:La:S glasses is investigated. It is shown that microcrystals of Ga:La:S and of alpha-phase of gallium-sulphide (alpha-Ga2S3), whose presence in the glass matrix is revealed by x-ray diffraction analysis, are responsible for the frequency doubling process

Phase-change chalcogenide glass metamaterial

Combining metamaterials with functional media brings a new dimension to their performance. Here we demonstrate substantial resonance frequency tuning in a photonic metamaterial hybridized with an electrically/optically switchable chalcogenide glass. The transition between amorphous and crystalline forms brings about a 10% shift in the near-infrared resonance wavelength of an asymmetric split-ring array, providing transmission modulation functionality with a contrast ratio of 4:1 in a device of sub-wavelength thickness.Comment: 3 pages, 3 figure

Fabrication and aero dynamic levitation of chalcogenide glass spheres

Spheres of gallium-lanthanum sulphide (GLS) and gallium lanthanum sulphite (GLSO) have been produced by laser irradiation on a copper hearth. Although similar fabrication techniques have been applied to oxide glasses, the technique has been overlooked for the production of chalcogenide glasses due to the perceived problem of the volatility of the chalcogens. In this work, glass microspheres of GLS/GLSO have been fabricated by laser irradiation of micron size irregular shaped glass particles on a Cu plate. In this material we found that evaporation of sulphur was not substantial as it appears to be more strongly chemically bound [1]. In addition to this method we have also established that it is possible to form larger spheres (mm diameter) of GLSO by aerodynamic levitation and laser heating using a CO2 laser (10.6 µm wavelength). Our studies involve overheating and supercooling of liquids and melts, outgassing analysis, high temperature resistivity measurements, and crystallization/structural studies [1-3]. In both fabrication methods the glasses could be melted and re-vitrified with low sulphur mass loss. We conclude that the production of glass spheres by laser irradiation[4] from irregular shaped starting material on a substrate using the wetting principle has substantial benefits for making microspheres and nanospheres

Spectroscopic and thermal properties of GeS2-based chalcohalide glasses

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

High speed chalcogenide glass electrochemical metallization cells with various active metals

We fabricated electrochemical metallization (ECM) cells using a GaLaSO solid electrolyte, a InSnO inactive electrode and active electrodes consisting of various metals (Cu, Ag, Fe, Cu, Mo, Al). Devices with Ag and Cu active metals showed consistent and repeatable resistive switching behaviour, and had a retention of 3 and >43 days, respectively; both had switching speeds of < 5 ns. Devices with Cr and Fe active metals displayed incomplete or intermittent resistive switching, and devices with Mo and Al active electrodes displayed no resistive switching ability. Deeper penetration of the active metal into the GaLaSO layer resulted in greater resistive switching ability of the cell. The off-state resistivity was greater for more reactive active metals which may be due to a thicker intermediate layer

Structural and spectral characterisation of Er3+ and Nd3+ doped Ga-La-S-Se glasses

In this work, the spectroscopy of Er3+ and Nd3+ doped Se-GLS glasses was studied. A structural comparison between doped and non-doped samples was done to assess the differences between the glasses. For this comparison, Raman spectroscopy and thermal analysis were employed. The spectral properties of the samples were studied in order to identify the mechanisms responsible for quenching the fluorescence lifetime of the dopants. In particular, cross-relaxation and concentration quenching were observed in Nd3+ doped samples, whilst co-operative upconversion, radiation trapping and concentration quenching were observed in Er3+ doped samples. The results obtained demonstrated the fundamental role of the phonon energy in the mechanism of fluorescence. The low phonon energy of chalcogenides decreased the rate of non-radiative processes promoting co-operative upconversion. This effect could be exploited to design new lasers and sensitizers for solar energy harvesters

Concentration dependence of the fluorescence decay profile in transition metal doped chalcogenide glass

Abstract In this paper we present the fluorescence decay profiles of vanadium and titanium doped gallium lanthanum sulphide (GLS) glass at various doping concentrations between 0.01 and 1% (molar). We demonstrate that below a critical doping concentration the fluorescence decay profile can be fitted with the stretched exponential function: exp [-(t/τ) β ], where τ is the fluorescence lifetime and β is the stretch factor. At low concentrations the lifetime for vanadium and titanium doped GLS was 30 μs and 67 μs respectively. We validate the use of the stretched exponential model and discuss the possible microscopic phenomenon it arises from. We also demonstrate that above a critical doping concentration of around 0.1% (molar) the fluorescence decay profile can be fitted with the double exponential function: a*exp-(t/τ 1 )+ b*exp-(t/τ 2 ), where τ 1 and τ 2 are characteristic fast and slow components of the fluorescence decay profile, for vanadium the fast and slow components are 5 μs and 30 μs respectively and for titanium they are 15 μs and 67 μs respectively. We also show that the fluorescence lifetime of vanadium and titanium at low concentrations in the oxide rich host gallium lanthanum oxy-sulphide (GLSO) is 43 μs and 97 μs respectively, which is longer than that in GLS. From this we deduce that vanadium and titanium fluorescing ions preferentially substitute into high efficiency oxide sites until at a critical concentration they become saturated and low efficiency sulphide sites start to be filled

Engineering of composite metallic microfibers towards development of plasmonic devices for sensing applications

The paper discusses the analysis of tapered hybrid composite microfibers based on a metal-core and dielectric-cladding composite material system. Its advantages over the pure metal tips conventionally used, are the inherent enhanced environmental robustness due to inert borosilicate cladding and the capability of multiple excitation of the tapered nanowire through the length of the fiber due to the enabled total internal reflection at the borosilicate/air interface. Simulations through finite element method (FEM) have demonstrated an improved field enhancement at the tapered region of such microfibers. Furthermore, experimental results on tapering in copper based microfibers together with light coupling and propagation studies will be demonstrated revealing the potential for the development of plasmonic devices for sensing applications

Chalcogenide glasses for photonics device applications

Chalcogenides are compounds formed predominately from one or more of the chalcogen elements; sulphur, selenium and tellurium. Although first studied over fifty years ago, interest in chalcogenide glasses has, over the past few years, increased significantly as glasses, crystals and alloys find new life in a wide range of photonic devices. This chapter begins with an overview of chalcogenide glass compositions, their purification, synthesis and fabrication. Focussing on more novel gallium lanthanum sulphide based chalcogenides, as well as reviewing more established materials such as arsenic trisulphide based glasses we then explore the purification and synthesis of these materials, along with their basic optical and thermal properties. Next the fabrication of these versatile glasses into a variety of forms; including thin films, microspheres and optical fibers is explained. This chapter ends with an overview of representative applications of these exciting optoelectronic materials