Beam Expanders for CO₂ Lasers

Beam expanders have two main purposes in the laser industry.

• Increased power density in the focal point
• Beam guidance over long distances

Beam expanders often consist of two lenses that are built according to the Galileo principle and therefore do not generate an intermediate focus. These systems are suited for typical medium power levels of up to 100 W. There are different designs:

 

Fixed Expanders

Fixed expanders are inexpensive systems in which the focussing range cannot be readjusted. Compensating for the divergence/convergence of the incident beam is not possible.

Variable Expanders

With variable expanders, the spacing between the lenses can be modified to compensate for the divergence of the incident beam. The total length can vary by ± 3 mm.

Zoom Expanders

In zoom expanders an infinitely variable magnification level can be set ranging from 2 to 8 times the original size. Due to the high variability, these expanders are quite common in the laboratory.

The expanders are variable. That is to say, compensating for divergence/convergence is possible.

When used in reverse, beam expanders can reduce the beam diameter.