The definition and difference between sapphire windows, sapphire optical windows and sapphire protective windows?
A window is a parallel plane plate, usually used as a protective window for electronic sensors or external environmental detectors without changing the magnification of the systems. The substrate materials of windows include various kinds of sapphire, optical glass, K9, ultraviolet fused silica, infrared fused silica, calcium fluoride (CaF2), magnesium fluoride (MgF2), zinc selenide (ZnSe), germanium (Ge), silicon (Si) and other crystals, and provides anti-reflection coating, high-reflection coating, spectroscopic film, metal coating and other optical coatings. Broadband anti-reflection coating can be used in ultraviolet, visible, near infrared and mid-infrared bands. The window made of single crystal sapphire is called a sapphire window.
Sapphire window is a common term that covers both optical and protective sapphire windows.
Sapphire optical windows refers to sapphire windows used for optical applications, which generally refers to imaging, detection, scanning, and so on. Because sapphire has good light transmission in the full spectrum from ultraviolet to near-infrared, sapphire optical windows can reduce the amount of glass used in optical instruments and greatly reduce the weight of equipment, which makes it ideal for a wide range of applications in aerospace and other fields. However, the transmittance of sapphire material is only between 82-85%. In order to improve or prevent the transmittance on specific bands, it is often necessary to carry out specific coating treatment for sapphire optical windows, such as AR coating, AF coating, etc.. In the context of high-intensity laser applications, there is a higher demand for sapphire coating technology, which represents a significant research area in China now.
In order to meet the higher requirements of sapphire optical windows, higher demands are placed on the processing of sapphire optical windows. First of all, to ensure the consistency of the spectral transmission, it is necessary to ensure the parallelism of the sapphire window (that is, the consistency of the two sides to solve the optical path problem); Secondly, there are also strict requirements for the flatness (surface forming) of each plane, which must be within the nanometre range, optically known as the wavelength, and it is generally required to be within 1/4 of the wavelength.
A sapphire protective window is a window used to protect users or items in containers by virtue of the pressure resistance, scratch resistance and high temperature resistance of sapphire. Due to the extremely high hardness of sapphire, it has stronger pressure resistance and scratch resistance than other glass products, which is why protective windows made of sapphire are often used in deep water, oil fields, flammable and explosive occasions, high-pressure vessels, vacuum vessels and other fields. At the same time, sapphire can withstand a high temperature of 2030 degrees Celsius, so it is often used in high-temperature containers as well.
As can be observed from the aforementioned information, the term “sapphire windows” is a common name, whereas “sapphire optical windows” and “sapphire protective windows” are specific names for sapphire used in different occasions.
