Low expansion optical materials, as their name implies, are known for an impressively low coefficient of thermal expansion and are very resistant to high-temperature thermal shock. Typically, low expansion materials have a near zero coefficient of thermal expansion. Ceramic glass substrates are generally engineered to retain their mechanical and optical properties – especially reflected wavefront – even during extreme temperature changes.
The material has very high mechanical strength, high chemical durability/resistance, and superior machinability characteristics. These materials can be available in sizes up to 8 meters in diameter with the bulk of the mirror substrates ranging in the in the 1 – 2 meter range.
Characteristics of low expansion materials include:
- Extremely low coefficient of thermal expansion (CTE)
- Large operating temperature range and shock resistivity
- Extreme hardness, fracture toughness
- Excellent chemical stability
- Non-porous material
- High affinity for coatings
- Few inclusions and bubbles
- Large size capabilities
Low expansion materials are ideal for astronomical telescope mirror substrates, lightweight mirrors & mounts, laser cavities, and precision metrology fixtures. In fact, these materials are the material of choice for all of the world´s segmented telescopes currently in operation.
Based upon customer demand, Sydor Optics offers Low Expansion made from the following substrate materials. Of course, if you don’t see a material you need, please contact a Sales Engineer, who will gladly discuss additional options that may be available.