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Physical properties of chalcogenide glass, including broadband infrared
transparency, high refractive index, low glass transition temperature,
and nonlinear properties, make them attractive candidates for advanced
mid-infrared (3 to 12 μm) optical designs. Efforts focused at
developing new chalcogenide glass formulations and processing methods
requ...
Context in source publication
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... wavelength region is near the absorption band gaps of IG glasses, resulting very blunt critical angle knees that are difficult to interpret. The refractive indices and compositions by molar percentage of each glass are summarized in Table 3 for each glass family. The indices reported here are expected to have a resolution of 1x10 -4 and accuracy of ±1x10 -3 . ...Similar publications
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Citations
... al., Carlie et. al. [32][33][34]. In the present study, ten measurements are performed on each sample with an error of ± 0.0005. ...
The manufacturing of low loss chalcogenide glasses (ChGs) for optoelectronic applications is ultimately defined by the concentration of impurities present in starting materials or imparted via processing. We describe a rapid method for purifying metallic starting materials in As2Se3 glass where oxide reduction is correlated to optical and physical properties. Specifically, As-O reduction enhances the glass’ dual-band optical transparency proportional to the extent (13-fold reduction) of oxide reduction, and is accompanied by a change in density and hardness associated with changes in matrix bonding. A significant modification of the glass’ index and LWIR Abbe number is reported highlighting the significant impact purification has on material dispersion control required in optical designs.
... The properties of mid-infrared (MIR) transparency, high refractive index, low phonon energy, high optical non-linearity [2], and an ability to dope them with rare-earth element ions [3][4][5][6][7], make chalcogenide glasses attractive candidates for use in planar photonic integrated circuits [8,9], narrow-and broad-band fiber-based luminescence [10][11][12] and laser sources [13,14] and amplifiers [15][16][17] operating at MIR wavelengths (3-50 μm). Although much research effort has been paid to the development and characterization of chalcogenide glasses for photonics, relatively few refractive index dispersion and thermo-optic coefficient data are presently available at MIR wavelengths, see for example [18][19][20][21][22][23][24] with the notable exception of the few chalcogenide glasses used commercially in optics [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39]. ...
... % of the nominally batched compositions for these glasses [43,45]. Techniques commonly used for the refractive index measurement include the modeling of transmission or reflection spectroscopic data [46][47][48][49], spectroscopic ellipsometry [18,20,22], prism coupling [19,50], grating coupling [51], and the measurement of the minimum deviation angle of light passing through a prism [24,52]. Several of these techniques require intensive sample preparation, are time consuming, and are costly to conduct. ...
Chalcogenide glasses have attracted much attention for the realization of photonic components owing to their outstanding optical properties in the mid-infrared (MIR) region. However, relatively few refractive index dispersion data are presently available for these glasses at MIR wavelengths. This paper presents a mini review of methods we have both used and developed to determine the refractive indices and thermo-optic coefficients of chalcogenide glasses at MIR wavelengths, and is supported by new results. The mini review should be useful to both new and established researchers in the chalcogenide glass field and fields of MIR optics, fiber-optics and waveguides. Three groups of methods are distinguished: (1) spectroscopic ellipsometry, (2) prism-based methods, and (3) methods using Fourier transform infrared (FTIR) transmission data. The mini review is supported by a brief discussion of refractive index models. Keywords: Refractive index dispersion, Thermo-optic coefficient, Chalcogenide glass
... Refractive index was measured before and after heat treatment on glass/glass-ceramic samples, using a Metricon Inc. prism coupler (2010 Metricon Corporation, Pennington, NJ, USA) modified to measure the index of bulk and thin film samples in the infrared. Specifics on the system modification and basic principles of its use and measurements on other chalcogenide glasses can be found in works by Carlie et al., Qiao et al., and Gleason et al. [29][30][31] Ten measurements were performed on each sample with an error of ± 0.0005 for measurements at λ = 4.515 μm. Two different prisms were used depending on the index of the sample. ...
Melt size‐dependent physical property variation is examined in a multicomponent GeSe2‐As2Se3‐PbSe chalcogenide glass developed for gradient refractive index applications. The impact of melting conditions on small (40 g) prototype laboratory‐scale melts extended to commercially‐relevant melt sizes (1.325 kg) have been studied and the role of thermal history variation on physical and optical property evolution in parent glass, the glass’ crystallization behavior and postheat‐treated glass ceramics, is quantified. As‐melted glass morphology, optical homogeneity and heat treatment‐induced microstructure following a fixed, two‐step nucleation and growth protocol exhibit marked variation with melt size. These attributes are shown to impact crystallization behavior (growth rates, resulting crystalline phase formation) and induced effective refractive index change, neff, in the resulting optical nanocomposite. The magnitude of these changes is discussed based on thermal history related melt conditions.
... Once a GRIN element is created its resulting index profile must be validated with sub-μm spatial accuracy in order to ensure that the method used to create the GRIN was correct. Traditional, absolute refractive index measurement methods include prism coupling [30][31][32][33], spectroscopic ellipsometry [34,35], minimum deviation [36], and Sagnac interferometry [37]. These techniques are often not suitable for measuring fine gradients in refractive index, since they typically measure over spatial areas in the mm to cm range. ...
... X-ray diffraction (XRD) measurements were performed on a PANalytical Empyrean, Xray diffraction system with 1.8kW, λ CuKα = 0.15418 nm, and 40 mA, on bulk samples at RT to confirm lack of crystallinity in the as-melted glass. The refractive index was measured using a Metricon prism coupler that has been modified for use in the IR, and has be described elsewhere [30][31][32][33]44]. Measurements were made at 4.515 μm and 30°C. ...
Thermally-induced nucleation and growth of secondary crystalline phases in a parent glass matrix results in the formation of a glass ceramic. Localized, spatial control of the number density and size of the crystal phases formed can yield ‘effective’ properties defined approximately by the local volume fraction of each phase present. With spatial control of crystal phase formation, the resulting optical nanocomposite exhibits gradients in physical properties including gradient refractive index (GRIN) profiles. Micro-structural changes quantified via Raman spectroscopy and X-ray diffraction have been correlated to calculated and measured refractive index modification verifying formation of an effective refractive index, neff, with the formation of nanocrystal phases created through thermal heat treatment in a multi-component chalcogenide glass. These findings have been used to define experimental laser irradiation conditions required to induce the conversion from glass to glass ceramic, verified using simulations to model the thermal profiles needed to substantiate the gradient in nanocrystal formation. Pre-nucleated glass underwent spatially varying nanocrystal growth using bandgap laser heating, where the laser beam’s thermal profile yielded a gradient in both resulting crystal phase formation and refractive index. The changes in the nanocomposite’s micro-Raman signature have been quantified and correlated to crystal phases formed, the material’s index change and the resulting GRIN profile. A flat, three-dimensional (3D) GRIN nanocomposite focusing element created through use of this approach, is demonstrated.
... This last configuration gives the opportunity of measuring the refractive index at any wavelength over the spectral range of the SC laser source, and of facilitating optical alignment due to the superposition of all the spectral content into a single beam. These features are advantageous compared to that of other prism coupling systems using several laser sources at different wavelengths to cover the mid-infrared [18]. The experimental set-up was calibrated by using a sapphire sample and its accuracy and precision were verified by analyzing a fused silica window. ...
The intensity of the absorption bands due to the hydroxyl (OH) vibrations in the spectrum of tellurite glasses was decreased by using tellurium tetrachloride (TeCl4) as a dehydrating additive. This additive is incorporated with the initial reagents of the glass. During synthesis, it reacts with the OH groups present in the glass melt by releasing gaseous hydrochloric acid. The low chloride content remaining in the different glasses after their synthesis negligibly modifies their thermal properties, their stability against crystallization, and their refractive index. Its low impact on the refractive index of the glasses was assessed in the mid-infrared thanks to an enhanced prism coupling system using a supercontinuum laser as light source.
... Depending on the glass composition, the TO coefficients of ChGs span a wide range from a few tenths to over 100 ppm/K -1 [189]. Though not themselves ChGs, the IR-transparent crystals of silicon and germanium have been extensively studied, and will have to substitute for discussion of the actual ChGs, for which very little data exists [190]. Fig. 10. ...
... Details of this system have been reported previously. 13,14 In this system, the plano-plano sample is held in physical contact with a Ge prism, and the prism-sample combination is rotated to determine the critical angle for each laser wavelength. The critical angle measurement is then used to directly determine the sample refractive index. ...
The structural and optical properties of AsSe chalcogenide glass, starting with As40Se60, were studied as a function of Ge or Se additions. These elements provide broad glass forming options when combined with the host matrix to allow for compositional tuning of properties. Optimization of glass composition has been shown to produce bulk glasses with a thermoptic coefficient (dn/dT) equal to zero, as well as a composition which could demonstrate a net zero change in index after precision glass molding (PGM). The bulk glass density, coefficient of thermal expansion (CTE), refractive index, and dn/dT were measured for all bulk compositions, as was the refractive index after PGM. For the bulk glasses examined, both the refractive index (measured at discrete laser wavelengths from 3.4 to10.6 μm) and dn/dT were observed to decrease as the molecular percentage of either Ge or Se is increased. Compared to the starting glass’ network, additions of either Ge or Se lead to a deviation from the “optimally constrained” binary glass’ average coordination number = 2.4. Additions of Se or Ge serve to decrease or increase the average coordination number (CN) of the glass, respectively, while also changing the network’s polarizability. After a representative PGM process, glasses exhibited an “index drop” consistent with that seen for oxide glasses.1 Based on our evaluation, both the Gecontaining and Ge-free tielines show potential for developing unique compositions with either a zero dn/dT for the unmolded, bulk glass, as well as the potential for a glass that demonstrates a net zero “index drop” after molding. Such correlation of glass chemistry, network, physical and optical properties will enable the tailoring of novel compositions suitable for prototyping towards targeted molding behavior and final properties.
Chalcogenide fibers are natural candidates for infrared supercontinuum sources. In this chapter, we describe mid-IR supercontinuum generation using step-index fibers, tapered fibers, suspended-core fibers, and photonic crystal fibers, double-clad fibers, polarization-maintaining fibers, and cascaded fibers. We also discuss how computer simulations contribute to our understanding of mid-IR supercontinuum generation. We describe the impact of nonlinearity and dispersion, loss, materials, damage threshold, fabrication, and output power on chalcogenide fibers that are used for mid-IR supercontinuum generation. It is the combination of wide transmission range, strong nonlinear properties, high optical damage threshold, and environmental stability that makes chalcogenide fibers an excellent system for fiber-based mid-IR supercontinuum laser sources.
