Reflective beam expanders from Optical Surfaces are aspheric mirror-based

Vacuum-compatible reflective beam expanders are aspheric mirror-based devices that offer either beam expansion or reduction capabilities. Incorporating high-precision off-axis mirrors, they provide unobstructed output and efficient transmission. Manufactured to λ/5 surface accuracy, they can be used without the need for internal re-alignment.
Optical Surfaces
Kenley, Surrey, England
www.optisurf.com