Why choose sapphire for optics?
With a Mohs 9 hardness, sapphire is second only to diamond in its protective ability. Using modern finishing processes, sapphire can be fabricated into various configurations such as:
Sapphire windows can include stepped edges, elliptical edge shaping, holes, slots, and wedges for mounting purposes.
Manufactured from optical grade grown sapphire for use in IR laser beamsteering, imaging, and focusing.
Domes are well suited for a wide variety of applications including high speed missile domes and viewports.
Properties of Sapphire
The properties shown in the table below are average values for different orientations, for more detailed property information please contact us.
Vickers Hardness ∥ to c-axis: 1940
Vickers Hardness ⊥ to c-axis: 2200
Tensile Strength: 60,000 psi
Compressive Strength: 300,000 psi
Young’s Modulus: 74 x 106 psi
Poisson Ratio: 0.28
Melting Point: 2050°C
Thermal Conductivity: 32W/Mk (@258°C)
Specific Heat: 1.99 J/cm3°C)
Resistivity: @25°C > 1018 ohm cm
@500°C > 1012 ohm cm
Dielectric Constant: Perpendicular to C axis 9.3 (KHz-I GHz, 25°)
Parallel to C axis 11.5 (KHz-I GHz, 25°)
Dielectric Strength: 480,000 v/cm
Optical Grading of Sapphire
Grade 1 Sapphire
Inclusions, lineage, bubbles and twins are not permitted.
Grade 2 Sapphire
Inclusions, lineage and twins are not permitted. Micro bubbles with a diameter of 10 microns or less are permitted. (Bubbles less than 10 microns are generally not visible with the naked eye).
Grade 3 Sapphire
Inclusions, lineage and twins are not permitted. Uniformly distributed bubbles not larger than 50 microns in diameter and not closer in distance between bubbles than 500 microns are permitted.
Want answers to a specific question, or to learn more about sapphire optics?
The quality of sapphire is determined by how closely the grown crystal matches the ideal structure with respect to the arrangement of atoms within the lattice, dislocations, defects, and stress. The root causes for these problems often originate from insufficient purity of the starting material and the growth process itself.ReAD MORE