Gentec-EO PH - Manual (Page 16)

Version 2.3
PH Series Instruction Manual Gentec Electro-Optics Inc. All rights reserved
12
4.3 SATURATION
The maximum power varies with wavelength, power density and from one diode to another. When
making measurements near the saturation power, you must verify the saturation effect with a
calibrated Filter.
4.3.1 Procedure with a known transmission value filter
Make the measurement with and without the filter.
Your power ratio should be equal to the transmission value of the filter.
4.3.2 Attenuator calibration procedure
Make sure your stable power source is far below the saturation point.
Make the measurement with and without the filter.
The transmission value is the ratio of the measurement with filter / without filter.
4.4 MEASUREMENT OF THE AVERAGE POWER OF A PULSE LASER BEAM
Conditions to be met:
The repetition rate must be at least 5 times the analog Bandwidth (see table IV).
The peak power must not saturate the detector.
To know if the detector is saturated, use procedure 4.3.1. Be careful when making the attenuator
calibration in pulse mode. The peak power must be in the linear region of the photodiode.
Peak power = Energy per pulse / pulse width. Energy per pulse = Average power / repetition rate.
4.5 WAVELENGTH
The photodiode response varies with wavelength. You may select your wavelength with the
Settings/Wavelength menu of the monitor or enter you wavelength in the Settings/Custom menu of
the monitor.
If you decide to use the photo detector without a Gentec-EO monitor, you will have to use the
sensitivity given by the photo detector calibration certificate to calculate the power on you laser beam.
If your wavelength is not given by the calibration certificate, you will have to make a linear
interpolation between two of the available calibration values. Fig. 1-4, Fig. 1-5 and Fig. 1-6 shows
the typical spectral response.
Linear interpolation formula:
Slope Sens y Sensitivit
LOW desired
*
_ _

 
  
Sensitivity
desired_

: The sensitivity at the desired wavelength.
LOW DESIRED
     
) (
) (
_ _
LOW HIGH
LOW HIGH
Sens Sens
Slope
 
 


