GlossaryVitron – Your Material Specialist

In order to increase translucency optical functional surfaces are coated with layers consisting of materials with adapted refractive indexes which reduce reflection. The higher the medium's refractive index, the more necessary an antireflexion coating to increase light transmisson. There are narrowband and broadband antireflexion coatings. Using multiple layers a translucency of over 99% can be realized in selected wavelength ranges even for materials with high refractive indexes.

CVD zinc sulphide is produced in a CVD-process with zinc vapour and hydrogen sulphide. The polycristalline material consists mainly of the cubic sphalerite. Even small amounts of the hexagonal modification wurtzite and other defects lead to a strong light dispersion in the visible and near infrared area. This is why the yellow material, which is opaque in the visible area, is only used in the middle infrared area (7,5 to 11 m). Is is often referred to as "as grown" or FLIR-material. The FLIR-material can be transferred into the colourless, multispectral zinc sulphide, which is transparent in the visible area as well, using hot isostatic pressing.

Chalcogenide glasses are amorphous solids in which the glass-forming elements (silicon and oxygen in "normal" glass) are contained in the form of germanium, arsenic und the heavy chalcogens sulphur, selenium and tellurium. Due to the heavier elements and the weaker chemical bond translucency shifts from the visible into the infared spectral range. Chalcogenide glasses are semiconductors. Their mechanical rigidity and thermal resistance are smaller than those of glasses for the visible spectral range, but their thermal expansion is considerably stronger.

HIP means hot isostratic pressing, a process which is used for quality improvement of powder metallic products or founding parts. In the process the parts are redensified in special autoclaves at high temperatures and through the high, all side pressure of an inert gas. The pressure can be up to 200MPa and the temperature up to 1400°C. CVD-zinc sulphide can be transferred from the opaque FLIR-quality into the multispectral form by means of an HIP-Process.

IR-materials are needed in the production of optical components (lenses, windows, prisms etc.) used in the infrared spectral range. All these materials are transparent for infrared radiation. Apart from that, this group of materials is characterized by a great variety: ionic mono-crystals (such as sodium chloride), semiconductors in a monocrystalline or polycrystalline form (such as germanium or silicon), polycrystalline II-VI-compounds (such as zinc sulfide or zinc selenide) or chalcogenide glasses, to name just a few.

Glass ceramic is a material which is made from a glass through controlled crystallisation. In the process, the types of crystals determine the desired characteristics of the glass ceramic. The machinable glass ceramic VITRONIT contains 60% of a mica phase in a glassy matrix. Due to the good fissility of the mica crystals VITRONIT can be machined with carbide tools. It is especially suitable for the production of high-precision ceramic components. No firing is required.

Optical components are unmounted lenses, prisms, windows etc.