BE25 Series Heavy Duty, Medium Beam Diameter
The BE25 series of beam expanders is designed for use with CO2 lasers of up to 2kW CW power. The
units are water cooled and incorporate an actuated-slide focusing mechanism to reduce beamwander
during focusing. By reducing beam divergence and allowing the user control over the
ongoing beam characteristics, these industrial laser beam expanders can improve system
performance, especially in large moving-optics systems.
Dimensions : See Figure 67.31.
Type : Fully corrected Galilean type, with ZnSe lenses.
Construction : Aluminium alloy, black anodised. Lenses mounted using
indium wire to aid heat transfer.
Cooling : Water (or air) cooled, via 8/6 size fittings.
Focus range : From infinity down to 2.8 metres. Calibrated.
Beam wander during focusing : 2 minutes of arc over full range.
Output clear aperture : 35mm diameter.
Input clear aperture : See Table 67.32.
Fitting : Via standard 52.0 dia x 1.5 pitch coupling ring.
Table 67.32 describes the model designations, magnification and input clear aperture of 5 standard
models. All models are externally identical except for the engraved model number.
The BE25 series use a standard Umicore Laser Optics rotating coupling ring. The units may be affixed
OPG piping (section 61.0).
LAU25/LAM25 lateral adjustment units (sections 72.1, 72.2).
The actuated-slide mechanism drives the output lens in a linear motion, reducing beam wander that
can occur in rotary mechanisms. The geometrical focus setting is calibrated from 2.8m to infinity.
Please note that the downstream beam waist position will depend upon the laser beam characteristics
as well as the focus setting. (See Section 67.0, Technical Clarification Doc. 4 and “Technical
assistance” below.) Geometrical focus is calibrated for a plane wave input.
ULO Optics have developed computer software to define the ideal beam expander size,
magnification and focus setting for applications. With input laser beam parameters, diameter and far-field
divergence, achievable beam conditions can be calculated upon installation of a beamexpander. Often this
is a fairly simple case of requiring a beam as “parallel” as possible over a long cutting bed with moving optics.
Occasionally the problems are more complex. Free assistance with these matters is available to purchasers,
or potential purchasers, of ULO Optics beam expanders.
Sometimes the expanded laser beam does not perform according to preliminary calculations. In such
cases, the laser far-field divergence was under estimated by the manufacturer, who may have
measured only in the ‘near-field’. Accurate measurements of true far-field divergence can be
obtained using a calibrated beamexpander and these results used in accurate predictions of
downstream beam performance (see Technical Clarification Document 4, section 7).
The specific applications for the BE25 series beamexpanders are too numerous to list. In general,
they are used by many system integrators in moving-optics cutting systems, long-bed anilox
processing and a variety of systems where a controlled beam and increased focused energy density