Sapphire Windows and Sapphire Waveplates are made from single crystal Sapphire. The single crystal form of Al2O3, called Sapphire, is one of the hardest materials and ranks a 9 on the Mohs scale. Sapphire is the second hardest crystal next to diamonds and because of its structural strength, sapphire optical windows can be made much thinner than other common dielectric optical windows with improved transmittance as a result. A Sapphire Optical Window is useful over a wide wavelength range, 0.15 to 5.5µm, and is resistant to UV radiation darkening.
Sapphire windows and sapphire waveplates are environmental stable and have resistance to common chemical acids and alkalis due to sapphire’s high dielectric constant. Other properties that make sapphire unique are high compressive strength, high melting point, high thermal stability and high thermal conductivity.
The birefringent nature of Sapphire makes it ideal as material for high quality environmentally stable waveplates that operate from UV into the mid IR. When making sapphire waveplates the crystal is typically grown at a crystal orientation that maximizes the birefringence. Sapphire windows on the other hand are normally grown at a crystal orientation that minimizes the birefringence.
Sapphire optical windows are ideal for applications where high pressure, high temperature, high thermal loads, vacuum, scratch/wear resistance, low friction, corrosive atmospheres are a consideration. Sapphire windows and sapphire waveplates are often used in research, medical, space, military applications due to its superior performance.