Sapphire is best suited for scratch resistance application with better transmission over the wide range spectrum. It can be made much thinner than BK7 windows.
Synthetic sapphire is an anisotropic crystalline material composed of single crystal aluminum oxide (Al2O3). Safetyrich works with only high quality, optical grade sapphire. It is 99.999% pure. The various properties of sapphire are a function of the direction within the crystal with respect to the optic axis. It has an extremely wide transmission spectrum (150 nm to 6.0 µm). Its high melting point, good thermal conductivity and low thermal expansion provide excellent performance in high temperature environments. The extreme hardness of sapphire makes it difficult to polish using standard techniques. High optical quality finishes on sapphire are not always possible.

Optical property
Crystal Class	Trigonal
Density at 20°C ,g/cm3	3.88
Thermal Conductivity  W/(mk)at 300K Parallel Perpendicular	35.1 33.0
Thermal Expansion 1K at 293K Parallel Perpendicular	5.6X10-6 5.0X10-6
Reflection loss,% for tow surfaces at 4 µm	12
Apparent Elastic Limit.MPa	275
Dielectric Constant for 103-1090Hz at 298K Parallel to C-axis Perpendicular to C-axis	11.5 9.5
Melting Point,K	2300
Specific Heat,cal/(gK)at 298K	0.18
Mohs Hardness	9
Knoop Hardness,kg/mm2	1370
Young's Modulus,GPa	335
Shear Modulus,Gpa	148
Bluk Modulus,GPa at 273K	240
Poisson's Ratio	0.25
Bandgap,eV	9.9
Water Solubility	None

	Sapphire Biconvex lens
		Material Sapphire General Precise Dimension Tolerance +/-0.1mm +/-0.05mm Claer Aperture 80% 90% Deviation 3min 1min Surface Faltness 1/4L@ 633nm 1/8L@633nm Surface Quality 40-20 10-5
	Sapphie Rectangular Prism
		Material Sapphire General Precise Dimension Tolerance +/-0.1mm +/-0.05mm Claer Aperture 80% 90% Surface Faltness 1/4L@ 633nm 1/8L@633nm Surface Quality 40-20 10-5