http://confocal-microscopy-list.275.s1.nabble.com/Suitable-laser-for-2-photon-brain-imaging-tp7588232p7588244.html
this topic of in vivo 2P imaging. I am also currently considering Chameleon
> *****
> To join, leave or search the confocal microscopy listserv, go to:
>
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> *****
>
> A prism compressor should offset the loss of power due to dispersion
> through the optics. For example, if you send a 140 fs pulse through a
> standard scan lens, tube lens and objective, the pulse will spread out to
> about 500 fs due to group velocity dispersion (although this will vary
> significantly depending on the objective, tube lens, and scan lens - see
> the following paper:
https://goo.gl/SsQYvQ). The contribution of water
> and
> tissue is practically non-existent (for example 2mm of water will cause a
> 140 fs pulse to spread out to 140.0035 fs according to this paper:
>
https://goo.gl/5NhHxF).
>
> Since the 140 fs pulse has spread out to a 500 fs pulse, the effective
> power density relative to the original pulse is 140/500 = 28%. Therefore,
> in a very simplified scenario, if you start with a 4W 140 fs pulse, after
> all the optics, you now have the equivalent power density of a 1W 140 fs
> pulse (4W * 0.28), but still with all the heating of a 4W beam. By using a
> prism compressor, assuming it is optimally tuned, you will get a 140 fs
> pulse at the sample. With this simplified scenario, a 1W 140 fs laser with
> a prism compressor is equivalent to a 4W 140 fs laser without a prism
> compressor, but with 1/4 the heating so all in all the laser with the
> compressor is theoretically the superior setup (as long as the compressor
> is used correctly). There are many papers that show reality diverges
> somewhat from theory, but that is to be expected with the optical
> complexity of biological samples paired with the non-linearity of 2P
> excitation.
>
> As far as FLIM goes, either laser will work equally well. Even a 500 fs
> pulse is effectively instantaneous for a FLIM detector (which usually have
> temporal resolutions down to about 100 ps in ideal conditions), so both
> will look identical to a FLIM system.
>
> Hope this helps,
> Ben Smith
>
>
>
>
>
> On Fri, May 11, 2018 at 9:24 AM, Craig Brideau <
[hidden email]>
> 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.
> > *****
> >
> > Hi Hana, this depends heavily on what fluorophore you are using, whether
> > the sample is 'live' or not, etc. What is your situation?
> >
> > Craig
> >
> > On Fri, May 11, 2018 at 5:24 AM Hana Uhlirova <
[hidden email]>
> > 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.
> > > *****
> > >
> > > Hello list, I'd like to know your opinions about the laser type
> suitable
> > > for 2-photon in vivo brain imaging. We are considering the Chameleon
> > Ultra
> > > family from Coherent (Ultra, Ultra I and Ultra II) and Chameleon
> Vision.
> > > With Vision we would get the dispersion pre-compensation but the peak
> > power
> > > is only 2.5 W as is for the Ultra. Ultra I has peak power of 2.9 W and
> > > Ultra II 3.5 W. In my old lab we used to have the Ultra II which I
> think
> > is
> > > the most common choice.
> > > My questions:
> > > 1. Does anyone use Ultra or Ultra I for multi-photon in vivo brain
> > imaging
> > > and is the laser power sufficient?
> > > 2. Does someone use the dispersion pre-compensation of Vision I? If so,
> > in
> > > which microscope and does it provide a significant improvement over a
> > > non-compensated beam?
> > > 3. What are the implications of the laser choice on fluorescence
> lifetime
> > > imaging?
> > >
> > > Thank you very much for your opinions and suggestions.
> > >
> > > Hana Uhlirova
> > > Institute of Scientific Instruments of the CAS
> > > Czech Republic
> > >
> >
>
>
>
> --
> Benjamin E. Smith, Ph. D.
> Imaging Specialist, Vision Science
> University of California, Berkeley
> 195 Life Sciences Addition
> Berkeley, CA 94720-3200
> Tel (510) 642-9712
> Fax (510) 643-6791
> e-mail:
[hidden email]
>
http://vision.berkeley.edu/?page_id=5635 <
http://vision.berkeley.edu/>
>