Other than diamond windows, sapphire windows and sapphire flat stock can outperform all other optical, and in many cases nonoptical, materials. A sapphire window exhibits exceptional performance in a number of applications that require extreme mechanical, optical, thermal and chemical robustness.

Square Sapphire Glass Windows

Why are sapphire windows such high performers?

  • Sapphire windows and flat stock are incredibly hard, strong and wear resistant:
    A sapphire window can be exposed to extreme abradants such as sand and particulates with minimal effect on the clarity of the window. This makes sapphire windows the ideal material for a variety of applications such as: Aerospace windows, downhole and drilling vision systems, inspection windows, watch crystals and gun sights.
  • Sapphire windows can take pressure like no other clear material, making sapphire windows the go-to transparent material for high-pressure vessels, deep sea windows and sight glasses. Combined with the exceptional thermal and chemical performance of sapphire, a sapphire window is the ideal transparency for pressurized in-process, deep sea and equipment sensors.
  • Sapphire flats and wear parts are used in applications in which wear is a problem. Systems like canning machines, slide plates, V-blocks, flat bearings and pushers utilize sapphire flats and blocks to extend the lifetime of the equipment and reduce downtime.




Sapphire windows transmit light from below 190nm to over 5 microns:

  • A sapphire optical window is the ideal window material for many UV and IR applications because it can transmit so far into the UV and IR bands. With its thermal and chemical robustness, a sapphire window can be exposed to extreme plasmas and temperatures, far greater than any other material, and continue to transmit high powered UV, visible and IR for years with no degradation. These properties make it an ideal material for UV/VIS/IR sensors, IR surveillance and recon and broad band inspection equipment (especially when abradants are involved).
  • Sapphire windows are the ideal material for pyrometry. They transmit a wide range of wavelengths while safely isolating hot zones up to 2000C from external room temperature observation; making sapphire windows the ideal sight window for furnaces and high temperature processing equipment.
  • Medical and dental tools that require UV sterilization and curing and IR thermal processing are typical applications where sapphire windows and transparent tools excel.

Round Sapphire Glass Windows

Sapphire is highly robust at extreme temperatures:

  • A supported sapphire window can be taken to 1950C with no change to its shape and minimal reduction to mechanical performance. Sapphire windows are the perfect material for high temperature combustion chambers, gas processing and lamp shields.
  • Sapphire flats are ideal for furniture, boats and standoffs in high temperature furnace systems. Sapphire flats remain flat and dimensionally "perfect" up to 1700C. Because of sapphire's extreme chemical resistance many materials will not stick to sapphire in spite of high temperatures.
  • Sapphire windows and flats maintain the highest temperature rating of all optical materials in both oxidizing and inert atmospheres.
  • Sapphire windows can withstand considerably higher temperatures than the closest runner up material, fused silica, with zero degradation. Fused silica will degrade and devitrify over time at temperatures almost half the maximum operating temperature of sapphire.

And finally, Sapphire windows and sapphire flats are incredibly chemical and plasma resistant:

  • Due to the extreme chemical resistance of sapphire tubes and rods at high temperatures, a sapphire tube is the ideal choice for plasma chambers and sapphire lamp applications.
  • Only hot caustic salts can etch sapphire rods and sapphire tubes. All other solvents, acids and caustics have no effect on sapphire, including molten metals. This property allows for safe, chemically pure chemical handling and processing.
  • Sapphire rods and tubes are so chemically and bio-inert, they are the perfect materials for medical, pharmaceutical, semiconductor and other applications where maintaining purity and health is critical.

Rayotek has been fabricating micro to large sapphire windows, sight glasses and flats for over 25 years. Although sapphire is often more costly than glass and other transparent materials, its exceptional properties can ultimately save money and reduce critical down time, often eliminating the need for PM periodic replacements.

Synthetic sapphire is a single crystal form of corundum, aka, pure single crystal aluminum oxide, A12O3.  The combination of its unique properties make sapphire a preferred material for extreme mechanical, chemical & optical applications. Unlike glass, sapphire cannot be molded.  Sapphire can be grown into near net shapes such as tubes and rod, then ground and polished if necessary.
Industries Served Applications
Aerospace Windows, ball bearings, sensors
Medical Dental tool tips, endoscopy, camera lens cover
Oil & Gas Sight window without housing, gauges, diffusion plates
Military Windows, viewports, sensors, range finders
Research Containment tubes, cuvettes, lenses
Semiconductor Plasma tubes, lamps, lasers
Common Grades Description & Common Applications
  There are numerous sapphire growth methods & grades. Generally, the higher the grade the better the transmission in the UV and IR, and the less light scatter and lattice distortion.  The best grades, in particular, UV grade will not solarize.
Verneuil Original & simplest growth method, lowest cost, excellent for mechanical applications & situations where optical clarity is not critical. Good for lower quality watch crystals & observation ports
EFG (Stepanov) Edge defined growth method (to be exact, Edge-Defined Film-Fed Growth) for near net growth of tubes & large sheets. Better quality than Verneuil, but not  as pure & defect free as Kyropoulos or CZ. Excellent for most window applications including scanner windows & viewports and lower cost than Kyropoulos & HEM
Kyropoulos & CZ Excellent optical properties, ideal method for most optical applications except long exposure high UV & extreme power threshold requirements. Also preferred for high purity applications like semiconductor, LED fabrication & high purity chemistry
HEM The best quality sapphire, but difficult to acquire & considerably more costly compared to other grades. Quality compared to Kyropoulos usually not significant enough to justify cost for most applications. Best for extreme power & UV applications & for when zero fluorescence &/or high power threshold is required
Orientation Definition & Common Applications   
C-Axis Also known as the "optical axis". The only orientation that has almost zero birefringence for signals parallel to the C-axis. Used for optimal optical, mechanical, thermal & electrical performance.  In a rod or tube the typical C-axis orientation is along its length, in a window perpendicular to the face.
Random Parts are manufactured with no tracking of the crystal orientation.  Lower cost &  great for applications where orientation will not impact performance
Other  90 Degree (to C-axis), M-Plane, A-Plane, R-Plane
  Click for Orientation Definitions & Drawing
Properties Important Properties of Sapphire
  Thermal, physical/mechanical, optical, electrical & chemical
  Click for Sapphire Properties Data Sheet
Transmission & Other Curves Definition
  The overall transmission of sapphire is determined by purity. All quality sapphire materials transmit about the same in the visible wavelengths while higher purity creates better transmission in the UV and IR.  For all optical materials, including sapphire, the thinner the material the deeper it transmits into the UV and IR
  Click for Sapphire Optical & Thermal Properties Graph
  Click for Transparent Materials Transmissions Curves Graph
Surface Finish Description     
Polished Clear. Has little to no distortion & light scattering (depending on level of polishing). Ideal for optical applications, high purity semiconductor, chemical & vacuum processing
Fine Ground Frosted.  Ground surface roughness can be fine tuned for diffuser & low stiction applications. Tends to have micro-cracks that can trap water, gas & other impurities
As Grown Clear but not mechanically polished. Some optical distortion due to growth process but no micro cracks. Excellent for high vacuum systems such as plasma chambers & chemical processing where purity is critical but optical clarity is not
  Click for Surface Finish Photos
Surface Quality Definition & Rating
  The scratch-dig rating of surface quality is a qualitative rating based on comparing the actual surface to a scratch-dig standard. Pass or fail is somewhat subjective without clear dimensions to measure
80-50 Commercial quality such as car windshield and commercial windows
60-40 Good polish, good for commercial lenses and optics. Good for optics where light scatter is not a problem
40-20 Superior polish, good for higher performance optics and lower powered lasers. Reduced light scatter over 60-40
20-10 High Precision polish, extreme optics & good laser power threshold for medium powered lasers. Very little light scatter
 10-5 Highest surface quality, highest laser power threshold and lowest vulnerability to solarization. Exceptional optics with near-zero light scatter
  Click for Quality Scratch-Dig Definitions
Why Sapphire?  
  One of the hardest materials available
  Superior IR & UV transmission compared to other optical materials
  Highly scratch & abradant resistant
  Highly chemical resistant
  Maximum temperature rating of almost 2000C
  Excellent dielectric & loss tangent performance
Why Rayotek?  
  Onsite engineers & master optician
  25+ years of expertise in sapphire & exotic materials manufacturing
  ISO 9001:2008 Certified
  ITAR Registered
  State-of-the-art manufacturing equipment & measurement capabilities
  Cost saving overseas sourcing (for non-ITAR applications only)
  US Manufacturing at Rayotek's  30,000 SqFt facility +  partnerships in the U.S., China, Europe & Russia
Sapphire Services  
  Fire Polishing
  Laser Engraving
  Screen Printing



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