Sill Optics has introduced its Series Alpha (Absorption Low Plus High Aperture) range of fused silica beam expanders for high power lasers emitting from 1,030nm to 1,090nm. The beam expanders are available with a range of expansion factors from 0.8x to 3.0x. The company states that its beam expanders are well suited to very large incident beams of up to 24mm for the 1.1x version and 16mm for the 3x version. All beam expanders are highly corrected two-lens systems to keep the number of surfaces in the laser system to a minimum.
The lenses are made of fused silica to increase their damage threshold and are combined with low absorption coatings to minimise thermal lensing (which would lead to a focal shift and possibly cause unstable operation). The combination of fused silica lenses and this special low-absorption coating is already well proven with lasers in the several kilowatt laser power segments.
The Series Alpha allows easy adjustment of the output beam divergence. The design is of Galilean type, meaning that there is no internal focus and the system length is short compared to a Kepler type system.