Sapphire Windows: What are they and When to Use Them

 You may already have come across the term ‘sapphire’ as a naturally occurring precious stone. If you are thinking that this is what we are talking about then you are not correct. Sapphire can be produced synthetically in laboratories and several optical applications and instruments use them to their advantage. 

But what is sapphire exactly? And why should you care? Sapphire is the second hardest material coming next to diamond in Mohs hardness scale. Meaning it is extremely scratch resistant and have robust mechanical properties. Owing to such properties, sapphire finds extensive use in several applications where there is a need for a tough optical material. 



A sapphire optical window is made of single crystal sapphire with high scratch resistance, thermal robustness, and several other properties. Let’s find out what makes sapphire an ideal choice for optical window material.



What is Sapphire?

Synthetically prepared sapphire uses a single crystal corundum to form. Sapphire, as mentioned, has properties that are very robust and due to this reason it is favored as an optical material at such extreme environmental conditions. 

Sapphires are grown in large round drums that are slightly cylindrical. Cores of certain diameters are drilled from round boules to create sapphire rods. These rods are cut into thin slices, then optically polished to become sapphire windows. 

Compared to glass or plastic, the benefits of sapphire are very simple to grasp. The sapphire window is completely resistant to common scratches. The last thing you need is a scratch at the center of your smartphone camera, so sapphire is very suitable in such cases. 

In case of windows, any scratch will weaken it and it can break with a small impact. Sapphire windows do not form these scratches in the first place and there is no question of it getting broken. 

In scientific terms, sapphire has a high transmittance throughout the visible and mid-infrared spectrum.



Uses of Sapphire Windows 

Although sapphire windows have attracted attention recently due to the application in smartphones, they have actually been used in many industries for a long time. Sapphire is often used in less than ideal environments to protect the finest optical components sealed behind it. Commercial and military aircraft often have sapphire windows for vision protection systems to help pilots maneuver in poor vision conditions. Sapphire is used by submarines due to its resistance under pressure and its impermeability to saline abrasion. Sapphire is also used in many laser and LED applications.



When Not to Use Sapphire

Sapphire, though is an extremely hard substance with robust chemical and mechanical properties, is also quite expensive to manufacture. Its large scale industrial use is thus not quite applicable and different consumer products cannot use it because that would increase the overall cost of the product. 

Apart from being expensive, sapphire is also quite difficult to manufacture using intricate and complicated processes. So, sapphire is not really the ideal choice for use in consumer electronics. The places where sapphire can be and is used are primarily medical, military, and laboratory instruments.

Though some high-end watches and smartphones do use sapphire to protect its internal delicate components, it raises the cost of the product and becomes unaffordable for many. 

So, sapphire optical windows are best suited for use in situations where there is a need to protect other delicate optical instruments from harsh environment. 


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