Gentec-EO QE and XLE4 - Manual (Page 34)

QE Series Joulemeter Instruction Manual Version 3.0 April 2014 34
5 APPENDIX A
5.1 QED/12/25/50/65/95
Attenuator/Diffuser Calibration Procedure
Introduction;
These “Attenuator/Diffusers” must be user calibrated. The calibration procedure is relatively simple. First
make measurement without the attenuator, then with the attenuator. The ratio of these measurements will
be your correction. This procedure is suitable at any wavelength.
When using an oscilloscope;
Divide the joulemeter voltage output by the calibration sensitivity we provide to calculate the energy
reading (see joulemeter manual).
To use this procedure at a wavelength other than the wavelength stated on the calibration certificate, you
must first manually adjust the sensitivity value (of the cal. certificate) with the wavelength correction
multiplier from the Personal Wavelength Correction certificate. Use this wavelength-adjusted sensitivity to
calculate the energy readings used in the procedure that follows.
When using a Gentec-EO Monitor:
The Attenuator setting in the Measure mode must not be check marked. That is, it must be off, otherwise
you cannot access the wavelength menu window. You need this window to input the wavelength that you
are calibrating at (see monitor manual). The Attenuator setting should also be checked off if you are
redoing a calibration at the same wavelength as stated on joulemeter calibration certificate.
Procedure:
Step 1: Setup your joulemeter to measure the energy of your pulsed laser. If you are working at a
wavelength other than the calibrated wavelength, adjust the sensitivity of your joulemeter for that
wavelength; see When using an oscilloscope or When using a Gentec-EO MAESTRO, above. Make sure
that the energy level is below the detector’s damage threshold and your laser still has good stability.
Step 2: Apply energy for a few minutes to warm up the detector. This will reduce any thermal bias.
Step 3: Measure the energy level without the attenuator. To reduce random uncertainty, you should
average a number of shots. We recommend at least one hundred shots. This should reduce random
errors by a f
actor of 10. (Square root of “n” assuming Gaussian distribution).
Step 4: Install the attenuator. Without changing the laser settings, measure the energy level by
averaging the same number of shots. All laser settings must be the same as Step 3 (including beam size