There are two common types of fixed beam expander: Keplerian and Galilean.
Basic Keplerian beam expanders are assembled using two converging lenses and benefit from real intermediate focus, where pinhole can be placed for spatial filtering, thus providing better beam wave front at the output, however the focus can cause air breakdown at high power densities. Basic Galilean beam expanders are assembled using one diverging and one converging lenses, so there is no focal point inside the beam expander, thus it can be used for high powers. For low expansion ratios (1.3 - 20 times) the Galilean beam expander is preferred due to its simplicity and small size.
We offer beam expanders made from two, three, or more spherical lens made from BK7, FS, UVFS or other glasses which suit high power applications. Beam expander for any wavelength between 266 - 2000 nm is available on request.