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Comparison of the roughness of superpolished optics

Superpolishing offers significantly superior performance in applications that benefit from very low surface roughness.

Achieving a Scratch-Dig of 5-2, a surface roughness of less than 0.5 A, and zero defects at 300x magnification, most superpolished optics are supplied with polished or acid-etched outside diameters and bevels, adding to the level of cleanliness and durability of the components.

Superpolished materials include N-BK7, calcium fluoride, crystal quarz, fused silica, sapphire, silicon carbide, YAG, Nd:YAG, and ZERODUR.

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Sapphire Polishing

Sapphire is a unique material well suited for many ultraprecision optical applications. It is transparent from the lower UV (142 nm) through the mid-infrared (6.5 µm). Its high tensile strength makes it well suited to many high g-force environments.

In addition, sapphire is very tolerant of high radiation environments, such as space-based applications. Due to its high mechanical strength, sapphire is a very difficult material to polish. Our unique superpolishing processes allow us to polish sapphire components to better than 1 Å surface roughness.

Silicon Carbide Polishing

Silicon carbide (SiC) is often used in the optics industry to replace components previously manufactured out of beryllium. The material offers a viable alternative with low weight, high specific stiffness, high thermal conductivity, and excellent dimensional stability. We have developed expertise in polishing silicon carbide mirrors and can polish CVD SILICON CARBIDE™ and lightweight versions of this material.

We also offer customer-supplied substrate polishing services. Additionally, we offer SiC cladding with IBS coatings to ensure the finest possible final surface finish. Lastly, we also supply optical coatings on the finished mirror.

Comparison of three superpolish providers

G&HCompetitor ACompetitor B
Surface Roughness (RMS)<0.5Å <1Å <0.5Å
Scratch Dig<5-210-5Not specified
Inspection Magnification for defects300x20x>100x
Surface Accuracy<lambda/50<lambda/10<lambda/20
ShapesFlat, curved, multiple surfacesFlatFlat, curved, multiple surfaces
MaterialsSi, SiC, sapphire, ZERODUR, BK7, fused silica, crystal quartz, YAG , CaF2, quartz, YAG, LuAg and others.Fused silica FS, BK7, ZERODUR and others

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