Gentec-EO QE and XLE4 - Manual (Page 30)

QE Series Joulemeter Instruction Manual Version 3.0 April 2014 30
3 DAMAGE TO THE OPTICAL ABSORBER MATERIALS
In any time, the beam’s incident area should not be less than 10% of the detector’s aperture.
Please contact Gentec-EO to make measurements with such smaller beams.
Damage is usually caused by exceeding the manufacturer's
’pecified maximum incident:
- Average Power Density
- Peak Pulse Power Density
- Single Pulse Energy Density
Refer to the QE Series joulemeter specifications pages. This damage can also be caused when
using a detector with a contaminated absorber or attenuator surface.
The quoted damage thresholds in the specifications section refer to a visible alteration of the
absorber surface
10 . In practice a slight alteration will not affect the joulemeter response. Consider
the joulemeter to be damaged and/or out of calibration when large-scale damage is evident or you
can see the metal electrode beneath the coating
11 .
For a QED Attenuator/Diffuser
12 mounted on a QE series joulemeter, consider the detector to be
damaged and/or out of calibration 11 :
- In the presence of an optically eroded front optical component or in the presence of sparking at
the front component, accompanied by a sharp snapping noise: this phenomenon is related to
high single pulse energy density and high peak pulse power density.
- In the presence of shattered or molten optical components: this phenomenon is related to high
average power density.
- In the presence of a damaged absorber (see above).
In the case of a TEMoo (Gaussian) beam, the maximum peak power and energy density can be
calculated using the following equation:
Density (power or energy)

2Io

W
2
Where Io is the total beam power or energy
W is the beam radius at 1/e
2 and 
= 3.1416
10 For QE Series detectors, the use of the appropriate “QE series Test Target " is suggested in order to
insure that the laser beam will not damage the detector’s absorber coating; contact Gentec-EO for
further instructions.
11 Contact Gentec-EO for evaluation, repair, recalibration, or replacement (refer to the WARRANTY
instructions).
12 See optional accessories section.