THORLABS ERM100, Operation Manual, Page: 17 / 59

© 2018 Thorlabs
3 Operating Instruction
15
3.9 Measurement consideration
The method based on the rotating polarizer does not only take the polarized light into account
for the determination of the ER but also the unpolarized part. Therefore, even if the light with
linear polarization but with a DOP less than 100% enters the rotating polarizer the calculated
ER value depends strongly on the DOP. The following table shows the measured ER value in
relation to the DOP assuming a ideal linear polarization.
DOP [%] 90.0 98.0 99.0 99.8 99.9 99.94 99.98 99.99 99.998
ER [dB] 12.8 20.0 23.0 30.0 33.0 35.0 40.0 43.0 50.0
If the DOP is a problem for the ER measurement a more complex measurement system like
Thorlabs' Polarization Measurement System PAX57xx is required.