Altechna VBE 1X-4X User manual

Variable Beam
Expander
1X-4X
User Manual
2020 version v.1.00

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Contents
1. Introduction 3
2. Applications 4
3. Technical information 4
4. Alignment 5
5. Usage 9

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Variable Beam Expander (VBE)
October 2020
Copyright © 2020 Altechna, UAB. All rights reserved.
No part of this manual, including the products and soware described in it, may be reproduced, transmitted,
transcribed, stored in a retrieval system, or translated into any language in any form or by any means, except
documentation kept by the purchaser for backup purpose, without the express written permission of UAB
Altechna (hereinaer Altechna).
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writing by Altechna.
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Altechna provides this manual “as is” without warranty of any kind, either express or implied, including but
not limited to the implied warranties or conditions of merchantability for a particular purpose. In no event
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and the like), even if Altechna has been advised of the possibility of such damages arising from any defect or
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Specifications and information contained in this manual are furnished for informational use only and are
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including the products and soware described in it.
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1. Introduction
Variable Beam Expanders are ideal for the systems where dierent magnifications and precise control of laser
beam divergence/focusing is required. Standard Variable Laser Beam Expander models with expansion rates of
1X-4X will be reviewed in this manual. The beam expander incorporates zooming and focusing compensation,
which is realized by rotating external parts of the beam expander. There are two set screws to lock magnification
and focusing position once desired beam size is reached.
Features:
yDiraction limited performance
ySuitable for usage with ultrafast picosecond and femtosecond lasers
yConvenient magnification control and focusing compensation
yCustom wavelength available

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2. Applications
yLaser beam size control
yControl of focusing parameters (Numerical Aperture)
3. Technical information
yExpansion ratio: 1x-4x
yInput aperture: 11 mm
yExit aperture: 19 mm
yLens material: UVFS
yTotal transmission: >97%
yWavefront distortion: <λ/4 @ 632.8 nm
yLIDT: >10 J/cm² @ 1064 nm, 10 ns, 10 Hz
yHousing dimensions: Ø41.5 x 120-136.7 mm
yMounting thread: SM1
Magnification
Wavelength 1x 2x 3x 4x
1550 Ø8 Ø7 Ø5 Ø4
1342 Ø8 Ø7 Ø5 Ø4
1140 Ø7 Ø7 Ø5 Ø4
1020-1070 Ø7 Ø7 Ø5 Ø4
800 Ø7 Ø7 Ø5 Ø4
633 Ø6 Ø6.5 Ø5 Ø4
515-532 Ø6 Ø6.5 Ø4 Ø3
343-355 Ø4 Ø5.5 Ø3 Ø3
Table 1. Max input beam diameter (mm) ensuring diraction limited performance.

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4. Alignment
To obtain optimal performance it is highly recommended to align the VBE with input laser beam.
VBE alignment procedure:
1. Install camera ~1200 mm from the laser output, center it and set current beam position as a reference
point by placing crosshair over the center (fig. 1):
Figure 1. Setting beam position.
2. Place 4 axis mount at ~100 mm distance from the laser.
3. Align the mount with the beam.
4. Place the VBE into the 4-axis mount and unlock expansion and focusing cylinders with 1.3 mm hex (fig. 2):
Figure 2. Unlocking expansion and focusing regulators.

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5. Set VBE expansion scale to “x4” and focusing scale cylinder most counter-clockwise so that sliding
cylinder at the output of VBE was most outwards, it should correspond to ~260° mark on the scale (fig. 3):
Figure 3. Setting the focusing most outwards.
6. Aer VBE placement into optical beam path laser beam will be decentered on the screen. By adjusting
tilt (θx; θy) get the laser beam spot back to the center of the camera where crosshair was placed for
reference (fig. 4):
Figure 4. Centering laser beam spot.

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7. Set VBE expansion scale to “x1”and focusing scale to number “0°” (fig. 5):
Figure 5. Setting VBE expansion and focusing.
8. Aer magnification and focusing are changed, the laser beam spot will be decentered on the screen again.
9. Set current beam position as a reference point by placing crosshair over the center (fig. 6):
à
Figure 6. Setting laser beam position.
10. Set VBE expansion scale back to “x4” and focusing most counter-clockwise, it should correspond to
~260° mark on the scale (fig. 7):

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Figure 7. Setting expansion and focusing.
11. The laser beam spot will be moved from the crosshair again. By adjusting tilt (θx; θy) get the laser beam
spot back to the crosshair (fig. 8):
Figure 8. Centering laser beam sport with crosshair.
12. The VBE is aligned.
5. Usage
To set desired magnification on Variable laser beam expander three adjustment steps must be performed:
Adjustment procedure:
1. Unlock expansion and focusing cylinders with 1.3 mm hex.

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Figure 7. Setting expansion and focusing.
11. The laser beam spot will be moved from the crosshair again. By adjusting tilt (θx; θy) get the laser beam
spot back to the crosshair (fig. 8):
Figure 8. Centering laser beam sport with crosshair.
12. The VBE is aligned.
5. Usage
To set desired magnification on Variable laser beam expander three adjustment steps must be performed:
Adjustment procedure:
1. Unlock expansion and focusing cylinders with 1.3 mm hex.
2. Expansion cylinder should be rotated so that desired magnification value on the scale is aligned with
reference mark.
3. Focusing cylinder should be rotated to match the angle on focusing scale as per graph below. Please
note, that collimation curves are dierent for dierent wavelengths (fig. 9).
0°
50°
100°
150°
200°
250°
1x 1.5x 2x 2.5x 3x 3.5x 4x
Focusing (Scale denomination)
Expansion ratio (times)
Collimation curves
355 nm
532 nm
633 nm
800 nm
1064 nm
1140 nm
1342 nm
1550 nm
Figure 9. Collimation curves.
Note: Above graph is based on simulation with the following input the following input beam diameters: Ø3 mm
@ 355 nm, Ø3.8 mm @ 532 nm, Ø4 mm @ 633 nm, Ø4 mm @ 800 nm, Ø4 mm @ 1064 nm, Ø4 mm @ 1342 nm,
Ø4 mm @ 1550 nm.
In real applications focusing scale might require be even somewhat different fine-tuning to obtain best
collimation of the beam. The reason lays in laser beam characterization parameters (diameter, divergence and
M²) which are unique to every laser source. As a result, VBE, adjusted to collimate one laser beam might not
show the same performance with another laser of the same type.
4. Depending on input beam diameter, collimation might require slightly shied setting than indicated on
the curves above. Please refer to the graph below for comparison of collimation curves for Ø2 mm; Ø4 mm
and Ø6 mm beams (fig. 10).

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Expansion ratio (times)
Collimation curves
0°
40°
80°
120°
160°
200°
240°
1x 1.5x 2x 2.5x 3x 3.5x 4x
Focusing (scale denomination)
Ø2 mm beam
Ø4 mm beam
Ø6 mm beam
Figure 10. Collimation curves.
5. Depending on input beam divergence, collimation might require extra tuning, especially on the lower
expansion end. Please refer to the graph below for comparison of collimation curves for Ø2 mm beam with
Ø4 mm and Ø6 mm beams (fig. 11).
Expansion ratio (times)
Collimation curves
0°
60°
120°
180°
240°
1x 2x 3x 4x
Focisung (scale domomination)
Ø2 mm collimated beam
(geometric optics approximation)
Ø2 mm beam, full-angle
divergence 1 mrad (paraxial approx.)
Ø2 mm beam, full-angle
divergence 2 mrad (paraxial approx.)
Figure 11. Collimation curves.