True mid-infrared Pr3+ absorption cross-section in a selenide-chalcogenide host-glass

The mid-infrared (MIR) spans the 3-25 m wavelength range. Rare-earth-ion doped selenide-chalcogenide glasses are being developed for direct-emission MIR fibre lasers. The true Pr3+ absorption cross-section in the 3.5-6 µm wavelength region of a Pr3+-doped (500 ppmw of Pr3+ i.e. 9.47 x 1019 Pr3+ ions cm-3) GeAsGaSe host-glass is presented, after numerically removing the underlying, extrinsic vibrational absorption due to [H-Se-] contamination of the host-glass

True mid-infrared Pr3+ absorption cross-section in a selenide-chalcogenide host-glass

The mid-infrared (MIR) spans the 3-25 m wavelength range. Rare-earth-ion doped selenide-chalcogenide glasses are being developed for direct-emission MIR fibre lasers. The true Pr3+ absorption cross-section in the 3.5-6 µm wavelength region of a Pr3+-doped (500 ppmw of Pr3+ i.e. 9.47 x 1019 Pr3+ ions cm-3) GeAsGaSe host-glass is presented, after numerically removing the underlying, extrinsic vibrational absorption due to [H-Se-] contamination of the host-glass

Promising emission behavior in Pr 3+ /In selenide-chalcogenide-glass small-core step index fiber (SIF)

Selenide-chalcogenide glass, small-core, step-index fiber (SIF), core-doped with Pr3+: 9.51 × 1024 ions m−3 (500 ppmw) is fabricated for the first time with indium to help solubilize Pr3+. Core diameters of 20 or 40 μm are confirmed using scanning electron microscopy and near-field imaging; fibre numerical aperture is ∼0.4. Optical loss is ≥ 4.9 dB m−1 across the 3–9 μm mid-infrared (MIR) spectral range. On pumping at 1.55 μm or 2.013 μm, the SIFs give broad MIR emission across 3.5–6 μm assigned to 3H6 → 3H5 and 3H5 → 3H4. The Pr3+ emission-lifetime at 4.7 μm decreases from bulk-glass (10.1 ± 0.3 ms), to intermediately processed fiber (8.10 ± 0.5 ms) to SIF (7.1 ± 0.5 ms) induced by the processing. On end-pumping SIFs at 2.013 μm, the output pump-power and emission intensity at 4.7 μm became sub-linear and super-linear, respectively, suggesting MIR excited-state saturation is occurring

Determining the continuous thermo-optic coefficients of chalcogenide glass thin films in the MIR region using FTIR transmission spectra

A new method (FTIR continuous dn / dT method, n is refractive index and T temperature) for measuring the continuous thermo-optic coefficients of thin transparent films in the mid-infrared (MIR) spectral region is introduced. The technique is based on Fourier transform infrared (FTIR) transmission spectra measured at different temperatures. It is shown that this method can successfully determine the thermo-optic coefficient of chalcogenide glass thin films (of batch compositions Ge20Sb10Se70 at. % (atomic %) and Ge16As24Se15.5Te44.5 at. %) over the wavelength range from 2 to 25 µm. The measurement precision error is less than ±11.5 ppm / ºC over the wavelength range from 6 to 20 µm. The precision is much better than that provided by the prism minimum deviation method or an improved Swanepoel method

Characterising refractive index dispersion in chalcogenide glasses

Much effort has been devoted to the study of glasses that contain the chalcogen elements (sulfur, selenium and tellurium) for photonics’ applications out to MIR wavelengths. In this paper we describe some techniques for determining the refractive index dispersion characteristics of these glasses. Knowledge of material dispersion is critical in delivering step-index fibres including with high numerical aperture for mid-infrared supercontinuum generation

Vibrational Biospectroscopy: An Alternative Approach to Endometrial Cancer Diagnosis and Screening

Endometrial cancer (EC) is the sixth most common cancer and the fourth leading cause of death among women worldwide. Early detection and treatment are associated with a favourable prognosis and reduction in mortality. Unlike other common cancers, however, screening strategies lack the required sensitivity, specificity and accuracy to be successfully implemented in clinical practice and current diagnostic approaches are invasive, costly and time consuming. Such limitations highlight the unmet need to develop diagnostic and screening alternatives for EC, which should be accurate, rapid, minimally invasive and cost-effective. Vibrational spectroscopic techniques, Mid-Infrared Absorption Spectroscopy and Raman, exploit the atomic vibrational absorption induced by interaction of light and a biological sample, to generate a unique spectral response: a “biochemical fingerprint”. These are non-destructive techniques and, combined with multivariate statistical analysis, have been shown over the last decade to provide discrimination between cancerous and healthy samples, demonstrating a promising role in both cancer screening and diagnosis. The aim of this review is to collate available evidence, in order to provide insight into the present status of the application of vibrational biospectroscopy in endometrial cancer diagnosis and screening, and to assess future prospects

Determining the refractive index dispersion and thickness of hot-pressed chalcogenide thin films from an improved Swanepoel method

The well-known method presented by Swanepoel can be used to determine the refractive index dispersion of thin films in the near-infrared region from wavelength values at maxima and minima, only, of the transmission interference fringes. In order to extend this method into the mid-infrared (MIR) spectral region (our measurements are over the wavelength range from 2 to 25 μm), the method is improved by using a two-term Sellmeier model instead of the Cauchy model as the dispersive equation. Chalcogenide thin films of nominal batch composition As40Se60 (atomic %) and Ge16As24Se15.5Te44.5 (atomic %) are prepared by a hot-pressing technique. The refractive index dispersion of the chalcogenide thin films is determined by the improved method with a standard deviation of less than 0.0027. The accuracy of the method is shown to be better than 0.4% at a wavelength of 3.1 μm by comparison with a benchmark refractive index value obtained from prism measurements on Ge16As24Se15.5Te44.5 material taken from the same batch

Numerical modelling of Tb3+ doped selenide-chalcogenide multimode fibre based spontaneous emission sources

A model is developed of a terbium (III) ion doped selenide chalcogenide glass fibre source that provides spontaneous emission within the mid-infrared (MIR) wavelength range. Three numerical algorithms are used to calculate the solution and compare their properties

Experimental photoluminescence and lifetimes at wavelengths including beyond 7 microns in Sm3+-doped selenide-chalcogenide glass fibers

1000 ppmw Sm3+-doped Ge19.4Sb9.7Se67.9Ga3 atomic % chalcogenide bulk glass and unstructured fiber are prepared. Near- and mid-infrared absorption spectra of the bulk glass reveal Sm3+ electronic absorption bands, and extrinsic vibrational absorption bands, due to host impurities. Fiber photoluminescence, centred at 3.75 μm and 7.25 μm, is measured when pumping at either 1300 or 1470 nm. Pumping at 1470 nm enables the photoluminescent lifetime at 7.3 μm to be measured for the first time which was ~100 μm. This is the longest to date, experimentally observed lifetime in the 6.5-9 μm wavelength-range of a lanthanide-doped chalcogenide glass fiber