OPHIR BeamSquared, User Manual

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Attenuation 2.4.1
Distortions caused by insufficient or improper attenuation may be the largest source of error when measuring
beam propagation characteristics of high power lasers.
Beams < 1 Watt 2.4.1.1
Beams with very low power sources can be attenuated with Neutral Density (ND) filters. However, power
densities that exceed 5W/cm
2
can cause thermal lensing in the dark glass filter optic, distorting the beam.
Front surface beam splitter(s) should be used to sample beams with power density exceeding 5W/cm
2
.
Exceeding power density levels can also distort the beam. Distortion can occur at power densities as low as
5W/cm
2
.
Beams < 400 Watts 2.4.1.2
Beams with power from 1 to 400 Watts may be safely sampled with our LBS-300s family of beam attenuation
products. The LBS-300s is available for UV, Visible, and NIR lasers.
Beams < 2000 Watts 2.4.1.3
Beams with power from 400 to 2000 Watts require additional attenuation optics. This can be accomplished
with two LBS-300s systems, or by adding additional beam splitters to the LBS-300s system.
Do not exceed 2MW/cm
2
or 50 Joules/cm
2
(10 nanosecond pulse width). This fluence will damage most beam
sampling/splitting optics.
Beams > 2000 Watts 2.4.1.4
Beams with power greater than 2000 Watts require custom, cooled beam sampling optics. Alternatively Ophir-
Spiricon's BeamWatch line of laser beam diagnostic products does not require any beam attenuation.
Beam Alignment and Setup for Auto Mode 2.5
The following procedure should only be performed after attenuation of the laser beam. Failure to do
so may damage the camera. Refer to section 2.4.
For BeamSquared to operate correctly, the beam must enter the instrument through the center of the input
aperture and align along the instrument’s optical axis so that the beam does not appreciably "walk across" the
active area of the camera sensor. Improper alignment can add extra time to a BeamSquared measurement.
If the aperture needs to move to accommodate the beam location, additional calibrations will be needed which
slows the measurement.
Using two external turning mirrors makes it much easier to direct the beam into the optical train along its
optical axis as shown in the figure below. This axis runs perpendicular to the instrument’s long axis.