The BE38 series of beamexpanders is designed for use with high power/large beam diameter CO2
lasers of up to 3kW power CW. These Galilean beamexpanders use two ZnSe lens elements made
from lasergrade ZnSe and treated with ultra-low absorption anti-reflection coatings for maximum
power handling capacity. BE38 series beamexpanders use an actuated-slide focus mechanism to
reduce beam wander during focusing. The units are water cooled. Use of these beamexpanders can
improve system performance by reduction of the beam far-field divergence and by providing control
of the ongoing beam parameters. Technical specifications
Dimensions : See Figure 67.41.
Type : Fully corrected Galilean type, ZnSe lenses.
Construction : Aluminium alloy, black anodised. The lenses are mounted
using indium wire to aid heat transfer.
Cooling : Water cooled via 8/6 size fittings.
Focus range : From infinity down to 2.8 metres. Calibrated.
Output clear aperture : 57mm diameter.
Input clear aperture : 38mm diameter.
Fitting : Via 70.0mm x 1.5 pitch connector ring.
Beam wander during focusing : 2 arc minutes over full range.
BE38 series beamexpanders are made to order. Any reasonable magnification
can be constructed within the range x 1.15 to x 1.75. Standard
designs are listed in Table 67.42. All models are externally identical
except for the engraved model number. Associated equipment
The BE38 series incorporate the larger ‘38’ size of coupling ring with a female 70.0 dia. x 1.5 pitch
thread. They may be fitted directly to:
LPG piping (section 61.0).
LAU38 lateral adjustment unit (section 72.1). Focus control
The actuated-slide mechanism causes the output lens to be linearly repositioned when the focus
control ring is rotated. This reduces the beam wander that can occur with rotary focus mechanisms.
The geometrical focus position is calibrated from 2.8 metres to infinity. Please note that the
downstream beam waist position will, in general, be different from the geometrical focus setting.
This is described in more detail in Section 67.0 and in Technical Clarification Document 4. The
geometrical focus is calibrated for a plane wave input. Technical assistance
ULO Optics have developed computer software to allow computation of the ideal beamexpander
magnification and focus setting for specified ongoing beam requirements. The program input
requires reasonably accurate specification of the laser beam diameter and far-field divergence.
Assistance in selection of beamexpanders and calculations of expected beam performance is
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