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I agree with John. For point detectors, the red end of the spectrum
currently suffers from a lack of sensitivity. GAsP detectors don't play
well in that range so you're stuck with red-extended conventional PMTs
(multi-alkali typically). Hamamatsu -20 series work OK out to 850nm, but
only compared to a conventional PMT. For this application EMCCD or the like
would be more sensitive.

Craig

On Thu, Apr 9, 2015 at 8:52 AM, John Oreopoulos <[log in to unmask]
> wrote:

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>
> Stan,
>
> To your comment about PMTs not being sensitive in the IR, I would point
> out that NIR spinning disk confocal microscopy with a CCD/EMCCD detector
> (which does have better IR light sensitivity) is possible, and I created a
> short account of that with an example in a book chapter I was invited to
> write recently:
>
> http://www.sciencedirect.com/science/article/pii/B9780124201385000094
>
> It was a goal of ours at Spectral to do a comparison of this to 2-photon
> laser scanning confocal at some point, but getting access to the right
> equipment/samples/facilities proved difficult and the project was
> abandoned. I am not aware of any detailed comparisons like the ones Vitaly
> has asked for.
>
> John Oreopoulos
> Staff Scientist
> Spectral Applied Research Inc.
> A Division of Andor Technology
> Richmond Hill, Ontario
> Canada
> www.spectral.ca
>
>
>
> On 2015-04-09, at 10:35 AM, Stanislav Vitha wrote:
>
> > *****
> > To join, leave or search the confocal microscopy listserv, go to:
> > http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
> > Post images on http://www.imgur.com and include the link in your
> posting.
> > *****
> >
> > My guess (without much practical experience) is that the near IR confocal
> > will have issues in terms of detector sensitivity if you are using a
> point
> > scanner and PMTs; Most PMTs have pretty low QE in near-IR, with just few
> > exceptions. APD or camera-based detection may work better.
> >
> > Whether the lower sensitivity on the detection side is offset by improved
> > excitation (1-p versus 2-P) is an interesting question.
> >
> >
> > Stan Vitha
> > Microscopy and Imaging Center
> > Texas A&M University
> >
> >
> >
> >
>