How to calculate an estimate of power density for laser illumination ?

Posted by lechristophe on
URL: http://confocal-microscopy-list.275.s1.nabble.com/How-to-calculate-an-estimate-of-power-density-for-laser-illumination-tp7580574.html

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Dear microscopists,

I'm sure this is quite a stupid question. I keep seeing laser power
expressed as W/cm2 or kW/cm2 in super-resolution articles. I have a laser
for which I know the power out of the coupling fiber (let's say 50 mW),
that I use to illuminate the full field of a 100X, NA 1.49 objective
(similar to a TIRF laser setup, but not inclined). How can I estimate the
power density on the sample, assuming that there is no power loss in the
objective? It looks like I need to know the field of view area, but I'm not
sure what surface is actually illuminated : it is at least as large as the
ocular field of view, but could it be larger?

Thanks for your help,

Christophe