Chalcogenide Glasses

Chalcogenide glasses are formed by the addition of elements such as Ge, As, Sb, or Ga to chalcogen elements S, Se, and Te. In general they are transparent fromthe visible up to the infrared and they are low-phonon-energy materials. Since chalcogenide-glass fibers transmit in the IR, there are numerous potential applications in the civil, medical, and military areas. Chalcogenide glasses are sensitive to the absorption of electromagnetic radiation and show a variety of photoinduced effects as a result of illumination. These effects can be used to fabricate diffractive, wavguide and fiber structures.

Imaging ellipsometry mapping of photo-induced refractive index in As2S3 films (Literature, 2013)

$Refractive index map of a As2S3 film.$

Refractive index map of a As2S3 film.

Photoinduced diffraction grating formation in amorphous As₂S₃ thin films has been studied using imaging ellipsometry. We first have applied the nanofilm_ep3se imaging spectroscopic ellipsometer to obtain mapping of diffraction gratings in amorphous As₂S₃ thin films based on different photoinduced phenomena, namely photodarkening and photoinduced changes of refractive index.

The profile and absolute value of refractive index in gratings were studied as a function of exposure. It is shown that underexposure led to the formation of a sinusoidal profile of the refractive index. The proper exposure produced results close to the cycloidal profile. Overexposure led to the same cycloidal profile but with reduced amplitude of refractive index variation in comparison with that obtained under proper exposure.

Reference:

C. Rölinga, P. Thiesen, A. Meshalkinb, E. Achimovab, V. Abashkinb, A. Prisacarb, G. Triduhb (2013) Imaging ellipsometry mapping of photo-induced refractive index in As2S3 films. Journal of Non-Crystalline Solids 365, 93–98.

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Spectroscopic imaging ellipsometry on arsenic sulphide fibers – optical properties of cross sections with a lateral resolution down to 1 µm (Poster, 2011)

Spectroscopic imaging ellipsometry on arsenic sulphide fibers Accurion

Optical fiber typically consists of a transparent core surrounded by a transparent cladding material with a lower index of refraction to keep light within the core by total internal reflection. In this case, the fiber acts as a waveguide. The defining characteristics of optical fibers are the refractive index profiles in the diameter of the fiber. The difference in the refractive index between core and cladding is less than one percent. Glass optical fibers are mainly made from silica, but some other materials like chalcogenide glasses are used for longer-wavelength infrared or other specialized applications.

The cross section of three different arsenic sulphide fibers with different core diameters and different core/clad ratios were characterized. Ellipsometric contrast micrographs were recorded; wavelength spectra between 360 and 1000 nm at different regions of interest (ROI) and maps with a lateral resolution of 1 µm of Delta and Psi were measured. The optical dispersion of the samples was described by a layer stack including an arsenic sulphide substrate a roughness layer and air as ambient. The optical dispersion of As₂S₃ was expressed by a Tauc-Lorentz function and the roughness layer by an effective medium approach (host: As₂S₃, guest air, Bruggemann). For the transformation of Delta and Psi maps to maps of thickness of roughness layers and maps of refractive index, the Tauc-Lorentz function was substituted by n and k as fitting parameters.

Reference:

Thiesen PH., Röling C.(2011) Spectroscopic Imaging ellipsometry on arsenic sulphide fibers with a lateral resolution down to one micrometer. DPG-conference, Dresden, Germany

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Spectroscopic imaging ellipsometry on arsenic sulphide fibers – optical properties of cross sections with a lateral resolution down to 1 µm (Poster, 2011)

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