Selecting the Right Beam Expander

Hi, I'm Monica, an Optical Engineer here at Edmund Optics. Today I'm going to talk about the different types of beam expanders we offer and provide you with information that will help you choose a beam expander, or even make your own custom design. First of all, we offer two main types of beam expanders from our catalog: fixed power and zoom expanders. Fixed power beam expanders have one setting, such as 3x, 5x or 10x expansion power, but do include a focus adjustment for divergence correction and collimation. We offer a unique form of these fixed beam expanders for use with our laser diodes, in which the beam expander fits directly onto the face of the laser diode with a dovetail adapter and therefore requires little to no alignment. Zoom beam expanders have a range of expansion power, such as 1-3x, or 2-8x as seen with our line of zoom beam expanders. These have a focusing knob, like the fixed power beam expanders, as well as a knob that allows for the range of zooms. Both types of beam expanders can be used to increase beam size or can be reversed to reduce the beam size by the same factor it is expanded in normal use. Also, both types of beam expanders have a limit on how large the incoming beam can be determined by the clear aperture of the system. As with most of our optical components, we offer several coating options for beam expanders, from laser specific beam expanders, like our CO2 or Helium Neon beam expanders, to broadband or visible as in our fixed power laser beam expanders. If you are interested in building your own beam expander, one of the best designs for laser expansion is the Galilean design. This design utilizes two lenses, one positive and one negative at a distance equal to the sum of their focal length as you see here. Keep in mind the focal length of a negative lens is a negative number. The magnification of the beam is given by the negative ratio of the two focal lengths, so it is a positive number as seen here. If this set up is reversed, the beam size can be reduced, as you can see here. And the magnification can be calculated using this equation. Keep in mind that using a beam expander or beam minimizer changes the divergence properties of the beam. As the beam is expanded, the divergence is reduced. And as the beam is minimized, the divergence increases. I hope this answers your questions about different types of beam expanders we offer, as well as how you can build your own. For more information on beam expanders, check out our beam expanders application note on our website.