Ultra low expansion glass

Ultra low expansion glass (ULE) is a registered trademark of Corning Incorporated.

ULE has a very low coefficient of thermal expansion and contains as components silica and less than 10% titanium dioxide.

There are many applications for ULE, but by far the most common is for mirrors and lenses for telescopes in both space and terrestrial settings.

This type of material is needed for this application because the mirrors on telescopes, especially very large, high-precision units, cannot bend or lose their shape even slightly.

[3] ULE has a high resistance to weathering because of its hardness, and is also unaffected by nearly all chemical agents.

Hubble Space Telescope mirror made out of ULE glass.
Diagram of process of making ULE glass.