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There will be quite a bit of power loss through the objective, depending on
your magnification and numerical aperture.  You really should measure the
power after the objective, if possible.

Craig


On Fri, Jun 28, 2013 at 6:07 AM, Christophe Leterrier <
[log in to unmask]> wrote:

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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
>