HEM® Sapphire
- HEMEX® is the Highest Grade of HEM Sapphire Produced with Optical Homogeneity Measured as Low as 0.02 P-V
- Transmitted Wave Front (TWE) of 1/10 Wave Peak-to-Valley or Better
- Absorption <100 ppm at 1064nm
- Sapphire Optics Up to 22” in Diameter, Various Thickness Available
- Purity of 99.996% or Better, (View: GDMS Purity Analysis of HEM Sapphire)
- Low Damage, Super-Polished Optics Available
New for aerospace and defense applications: Large-format, high-quality HEM-grown sapphire boules.
Most widely used synthetic sapphire in optical applications.
Our superior optical quality sapphire is available in large A-plane sapphire window sizes up to 22” in diameter, available in various thicknesses. HEM Sapphire M-, C-, and r-plane windows are available up to 9” in diameter available with various thicknesses.
Exhibits the unique capability of having a broad transmission range from 250 nm to 5.5µm.
HEM Sapphire transmission and homogeneity are the highest in the industry and this material is the most widely used for sapphire reconnaissance windows, sapphire domes, and sapphire lenses. Sapphire window performance is only as good as the bulk sapphire material it is made from. HEM Sapphire properties are proven to combine high optical transmission, low transmitted wavefront distortion, and outstanding mechanical-strength properties at high and low temperatures. Data shows that the homogeneity for all grades of HEM Sapphire is in the 0.1 ppm range, with the highest grades better than 0.05 ppm. HEM Sapphire windows are currently performing in uncompromising environments in aerospace, High Power Lasers (HEL), and astronomy applications.
Produced by Crystal Systems in proprietary HEM growth systems and processes.
We grow the crystal while engineering both the furnace and process technologies, something the Company has focused on for more than 50+ years. Our sapphire processing “know-how” is applied to our customer’s unique requirements so that maximum performance is achieved in the final sapphire product.
HEM Sapphire is the #1 leading sapphire material for highly sophisticated optical applications that require reliability, strength and a wide range of light transmittance.
HEM Sapphire transmits light over a broad wavelength range spanning from 250nm to 5.5µm.
Performance Characteristics
- <100 ppm Absorption @1064nm
- Low dn/dt Over a Wide Range of Wavelengths, (Window Temperature Gradient Does not Cause Image Blur or Bore Sight Error)
- High Mechanical Strength for High-pressure and Shock-loading Applications
- Refractory Temperature Tolerance to Within a Few Hundred Degrees to its 2040°C Melting Point
- Chemical Resistivity Stable in Many Acid Environments at High Temperatures
- An Attractive Choice for Laser Host Applications and Use at Cryogenic Temperatures Because of High Thermal Conductivity
- High Resistance to Solarization Radiation Effects
- Hardness – Excellent Rain Erosion Resistance and Low Frictional Coefficient
- High Dielectric Constant (9.39 from 1.0 MHz to 8.5 GHz)
Optical Applications / Current Applications
Thanks to a robust dedication to material R&D, Crystal Systems is committed to supporting customers with new sapphire solutions to address their unique needs.
Large A-Plane HEM Sapphire windows are currently operating on the most advanced aerospace platforms. These 22” diameter sapphire aerospace windows are flight and performance-proven with wavefront values as low as 1/10 wave, high optical transmittance, strength, and durability. Large-sized HEM Sapphire windows are replacing ALON windows because of superior performance, lower cost, and immediate availability. Flight safety testing has proven that HEM Sapphire windows are fit for pressurized applications where the HEM Sapphire window is the only barrier between the flight crew and the outside environment.
In fact, Crystal Systems’ sapphire has achieved a Technology Readiness Level of 9 (TRL-9), which means the material has been thoroughly proven in the most demanding aerospace applications, from deep-sea to space. C-plane HEM Sapphire windows are distinguished for being one of the largest and highest quality non-birefringent sapphire optics available in the industry. This non-birefringent material excels for use in laser windows, High Energy Lasers (HEL), and laser mirrors because of hardness (9 on the Mohs scale), and high laser damage threshold (LDT). Sapphire is also increasingly viewed as a window material upgrade from Zinc Sulfide (ZnS) and Magnesium Fluoride (MgF2) for airborne applications. It is well known that HEM Sapphire is commercially available unlike other “promising” specialty optical materials such as ALON and Spinel which are more expensive and unable to deliver on promised performance.
HEM Sapphire is used in many mechanical applications because of its large size, strength, abrasion resistance and chemical stability.
Performance Characteristics
- Melting Point of 2040 C
- Hardness of 9 on the Mohs Scale
- Inert to Chemicals at High Temperatures
- Low Coefficient of Thermal Expansion
- High Compressive Strength
- High Flexural Strength at Elevated Temperatures
HEM Sapphire has undergone extensive compressive and tensile strength testing at many different temperatures in order to understand its intrinsic failure modes and suitability for different applications.
HEM Sapphire is used in high operating temperatures above 1,200 degrees Celsius. It is critical to leverage sapphire’s intrinsic strength by using proper optical fabrication processes. Low damage operations result in high-strength sapphire parts.
Moreover, sapphire’s anisotropic nature requires that crystallographic orientations be optimized for the direction of forces and temperatures to which the component will be subjected. We have done the mechanical testing and analysis and will guide our customers with this knowledge.
Sapphire is increasingly taking the place of glass as sapphire easily outperforms glass in mechanical applications. Even the most engineered glass types cannot compete with HEM Sapphire. Crystal Systems’ experience spanning more than 50+ years is focused not only on crystal growth but also on engineering furnace designs and adopting new processing techniques to meet ever-stringent customer demands.
Mechanical Applications / Current Applications
Crystal Systems’ unique HEM growth processes and extensive fabrication capabilities are fueling the replacement of less optimized crystal and glass materials with HEM Sapphire.
Mechanical HEM Sapphire applications include; sapphire wafer carriers, sapphire dental brackets, sapphire fire windows, sapphire view ports, sapphire nozzles, sapphire bearings, sapphire blades, sapphire tubes, sapphire jewel bearings and sapphire transparent armor to name just a few. HEM Sapphire will safely operate where other structural materials will fail. The current and emerging engineering applications for mechanical Sapphire rely on consistent mechanical strength, purity and orientation homogeneity.
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