THORLABS PM200 Operation Manual page 20

PM200
Also, beside the default flat top beam profile, where the power is distributed
evenly over the beam area, 2 more typical cases are also considered:
Gaussian: In case, the beam shape has one significant peak, the power density
around the peak is much higher than on the periphery. In order to consider that,
the calculated average power density value is doubled.
Hotspot: Some lasers have a beam profile shaped like a donut, or 2 or more
significant peaks appear in the profile. The power density in these hot spots is
much higher than the average across the entire beam diameter. The calculated
average power density value is tripled.
Note
Power density is always displayed in W/cm², energy density in J/cm². Density is
measured correctly only if the connected sensor is calibrated. In case a
customer made sensor is used, please make sure that the correct calibration
coefficient is entered.
Min, Max and Ratio
These subpanels show the minimum, maximum value, and the ratio out of both
numerically, in addition to the green and red markers on the power bar:
These values will update permanently. The "Reset Min / Max" button will reset
the displays to zero and restart the measurement sampling.
The ratio value will show "nan" ("No A Number") when a negative reading occurs.
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