Tellurite glass as a solid-state mid-infrared laser host material

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.Department of Applied Physic

Tellurite glass as a solid-state mid-infrared laser host material

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White light induced covalent modification of graphene using phenazine dye

Herein, we report a novel strategy for a covalent modification of graphene nanoplatelets with photoactive dyes. Functionalization of the graphene surface was carried out using white light to photochemically generate phenazine radicals and the reaction progress was followed up spectrophotometrically. Characterization of the modified material was carried out by FTIR, XRD, UV-vis absorption, fluorescence, Raman spectroscopy and SEM imaging. This hybrid material has improved solubility, shows an optical band gap of 1.95 eV and is highly emissive in the visible wavelength region

Tm³⁺ Tellurite-Modified-Silica Glass Thin Films Fabricated Using Ultrafast Laser Plasma Doping

Thin glass films have been produced by implanting Tm³⁺ doped and Tm³⁺/Er³⁺ codoped tellurite glasses into silica substrates using ultrafast laser plasma doping for the first time. The resulting glass films had thicknesses of up to 2 µm, refractive indices of 1.5 – 1.65 and exhibited photoluminscence in the 1.5 – 2.1 µm wavelength region when excited with 808 nm and 976 nm laser diodes. The OH⁻ content of the silica glass substrate was also found to have an effect on the Tm³⁺: ³F₄ photoluminescence lifetime in the modified thin glass film layer, with the high OH⁻ containing substrate exhibiting a shorter lifetime. Through optimisation of the femtosecond laser ablation parameters, we have produced crack-free thin films of Tm³⁺ doped tellurite-modified silica glass layers with good thickness uniformities of ±10 nm, and the refractive index of the modified layer is up to 13% higher than the bare substrate material

Role of Yb3+ ions on enhanced ~2.9 μm emission from Ho3+ ions in low phonon oxide glass system

The foremost limitation of an oxide based crystal or glass host to demonstrate mid- infrared emissions is its high phonon energy. It is very difficult to obtain radiative mid-infrared emissions from these hosts which normally relax non-radiatively between closely spaced energy levels of dopant rare earth ions. In this study, an intense mid-infrared emission around 2.9 μm has been perceived from Ho3+ ions in Yb3+/Ho3+ co-doped oxide based tellurite glass system. This emission intensity has increased many folds upon Yb3+: 985 nm excitation compared to direct Ho3+ excitations due to efficient excited state resonant energy transfer through Yb3+: 2F5/2 → Ho3+: 5I5 levels. The effective bandwidth (FWHM) and cross-section (σem) of measured emission at 2.9 μm are assessed to be 180 nm and 9.1 × 10−21 cm2 respectively which are comparable to other crystal/glass hosts and even better than ZBLAN fluoride glass host. Hence, this Ho3+/Yb3+ co-doped oxide glass system has immense potential for the development of solid state mid-infrared laser sources operating at 2.9 μm region

Lasers utilising tellurite glass-based gain media

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

Mid-IR (3-4 μm) fluorescence and ASE studies in Dy doped tellurite and germanate glasses and a fs laser inscribed waveguide

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

Formation of tellurite-modified-silica glass thin films containing rare earth ions using ultrafast laser plasma doping

Ultrafast pulsed lasers with pulse durations of 40-100 fs are used to deposit rare earth doped tellurite glass onto silica glass substrates in a pulsed laser deposition (PLD) chamber. Under certain conditions, the tellurite glass plasma mixes with the silica glass network producing a thin glass film of tellurite-modified-silica which produces some unique physical, and when doped with rare earth ions, spectroscopic properties. Layers of tellurite-modified-silica glass up to 2 µm thick have been produced with refractive indices of around 1.65, compared to 1.46 and 2.0 for the silica substrate and tellurite target glasses, respectively. Electron microscopy of the thin films shows a sharp and well defined boundary between the modified layer and the pristine substrate, and X-ray spectroscopy (EDX) confirms that the constituent ions of the target glass are uniformly distributed within the substrate silica glass network. Rare earth ions can be doped into these layers in concentrations which are higher than would be possible in pure silica glass without clustering, and Er3+ for example exhibits unusually long 1535 nm fluorescence lifetimes in these thin films. Tm3+ ions have also been doped into these layers, yielding longer wavelength fluorescence, up to around 2000 nm. By codoping Tm3+ and Er3+ ions, broadened fluorescence bands are possible which are of interest for broadband optical amplification. Additionally, codoping with Yb3+ allows efficient excitation using a convenient ~980 nm laser diode source. This technique of producing thin films is also being used to integrate dissimilar materials such as semiconductors, polymers and glass. In this presentation, we will describe the fabrication of rare earth doped tellurite-modified-silica thin films; the physical characterisation of the films including thickness, refractive index and surface roughness; and the optical properties such as transmission and fluorescence

Glass Thin Films for Planar Optical Components Fabricated using Ultrafast Laser Plasma Doping

Ultrafast pulsed lasers with pulse durations of 40-100 fs are used to deposit rare earth doped tellurite glass onto silica glass substrates in a pulsed laser deposition (PLD) chamber. Under certain conditions, the tellurite glass plasma mixes with the silica glass network producing a thin glass film of tellurite-modified-silica which produces some unique physical, and when doped with rare earth ions, spectroscopic properties. Layers of tellurite-modified-silica glass up to 2 µm thick have been produced with refractive indices of around 1.65, compared to 1.46 and 2.0 for the silica substrate and tellurite target glasses, respectively. Rare earth ions can be doped into these layers in concentrations which are higher than would be possible in pure silica glass without clustering, and Er³⁺ for example exhibits unusually long 1.535 µm fluorescence lifetimes in these thin films. Tm³⁺ ions have also been doped into these layers, yielding fluorescence with wavelength up to around 2 µm