Aside from the popular comparison between Germanium and silicon windows, Zinc Selenide and Zinc Sulfide are two other compounds serving as base for optical windows, which happen to be often debated. So let us take a closer look into their properties before we jump to other major issues associated to optical products.
Zinc Selenide is a compound with a solid state and yellowish shade, that is extremely difficult to find in nature, and whose main resources reside inside the Stilleite, a mineral. Some of its main features are the capacity of acting as a semiconductor and the band gap set around 2.70 eV when enjoying a 25-Celsius degree temperature.
Its name is often replaced with the short form of ZnSe and whenever combined with chromium, we are talking about ZnSe:Cr, a compound successfully used as gain medium infrared laser and emitting around the threshold of 2.4 µm. When used as optical material for controlling infrared fascicles, it has surprising effects as it transmits any wavelength in between 0.45 and 21.5 µm. Specialists consider it a good resource for creating diode lasers or light emitting diodes and the light that it generates has a blue shade.
As opposed to our first topic of discussion for today, Zinc Sulfide, which is also an inorganic material, is much easier to find in nature. In fact, this is the natural form that Zinc takes and it has some quite interesting physical properties! When extracted from the mineral called Sphalerite, it looks all black and dirty, full of impurities. However, by the end of its processing, it will turn out as a white or transparent material.
Obviously, the white form goes for creating pigments while the transparent one, which is the result of synthetic processing, serves as base for infrared and visible optical windows! Adding to these two its semiconductor, optical and luminescent properties and we’ve got quite a versatile compound to work with.
Again, with our point of interest being the optical applications, we need to specify that windows made from it can transmit any wavelength, from the visible ones to those of only 12 µm! So far, we understood how both materials can deal with the infrared spectrum – IR – and how they have decent semiconductor properties.
ZnSe is known in particular for its utility in building laser systems based on carbon dioxide, since it has an impressive thermal shock resistance and a low coefficient of absorption. Even so, harsh environments are not necessarily the best place to introduce them, which is why you should think twice before determining whether they fit to your needs.
Speaking of potential needs, while we have initially suggested that these two materials are often used for making optical windows, they are also useful in creating prisms, ATR prisms, positive lenses, beam splitters and many other related products. When you are not sure of your needs, options or choices, asking for consultancy, a free quotation or even witness samples is the right way to proceed. Asking for valuable extra information is no reason to be ashamed of!