Windows plays an important role in optical systems in terms of optimizing transmission and reducing reflection, as well as protecting the optical and electronic systems from environmental conditions.
When environmental conditions are severe, optical windows must improve their performance, which means choosing products with exceptional robustness. It is here that a sapphire window comes into play.
Why Sapphire Window?
Sapphire (Al203) is an exceptionally hard crystal material coming only after diamond in the Mohs hardness scale. Optical materials made from sapphire are renowned for their high performance and durability, outstanding elements such as fused silica and quartz.
Sapphire is a very popular material because:
- High mechanical resistance compared to other optical equipment
- Extreme surface hardness and structural integrity
- Excellent protection against abrasion and scratches
- Ultra-wide light transmits light from UV to mid-IR
- Can withstand temperatures up to 2030 degrees Celsius
- Chemically non-reactive and resistant to almost all chemicals except hot caustics
- High thermal conductivity
What is Sapphire Window used for?
Due to their high strength, sapphire optical windows can be made much thinner than other optical windows, which improves their transmissive performance. Sapphire optical windows have a wide wavelength range of 0.15 to 5.5 µm and are UV darkening resistant.
Applications where high temperature, high pressure, high thermal loads, abrasion and corrosive atmospheres and low friction should all be considered, sapphire windows are an ideal choice for such situations. Submersible ROVs, oil and gas analysis, barcode scanner and IR analysis all use sapphire windows.
Industrial, military and defense, space, medical and research sectors will attract sapphire windows for their performance and reliability in key applications.
Properties of Sapphire Windows
Sapphire is stronger and more expensive than modern glass. But what is the long-term cost of replacing fused silica windows every month? There may be glass optics that degrade over time due to harsh conditions. This is the perfect time for a sapphire window. Al2O3 (sapphire) has a Mohs hardness of 9. It is less hard than diamond and is the second hardest material for optical processing.
The price is a little higher than glass, but over time you can save money.
Transmission from UV to Mid-IR. No solid optical material covers the same spectrum as sapphire window. Example: Common glass allows generally between 375 nm and 2900 nm. Sapphires, on the other hand has a transmission range from 190nm up to 5000nm. It goes deep into the ultraviolet and mid-infrared! Sometimes you may need sapphires for heavy duty applications, but there are customers who need a little more modification. In this case, we recommend a white AR coating only on the inside and off the bare sapphire on the outside to prevent abrasion. One side AR layer can result in total bounces of up to over 92%.
Mechanical properties. Sapphire is strong and resilient. Glass begins to melt at 1400°C. Sapphire also has a positive effect on temperature. In fact, sapphire windows can be used for most applications up to 1800°C or slightly higher, near 3275°F.
But there is more! Sapphire Windows is also suitable for all kinds of products. It is also an excellent thermal conductor.
So you see now why a sapphire window is an excellent choice for many applications. Due to its robust mechanical and optical properties, sapphire is an excellent use at several different situations. It also has robust chemical properties and is non-reactive to most chemicals including several acids.