Can someone Explain GDD and how it is adjusted?

[Michael Moore]

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I'm a new member to the confocal listserv

Can someone explain GDD in regards to multiphoton imaging?
And how is GDD adjusted.

We currently have a Coherent chameleon vision II that has GDD.

I have been told conflicting instructions on how the GDD is adjusted or
used for imaging.

Maybe I just don't understand how GDD works.

for one, is GDD adjusted for each objective used?  is it independent of the
objective?

Thanks to all who reply.

Mike

[Michael Giacomelli]

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Hi Mike,

GDD is the group delay dispersion, the difference in time between different
wavelengths of light when passing through a system.  It represents the
tendency of shorter wavelength components of a pulse to travel at a
different speed through glass than longer wavelengths.  Its is the temporal
analog of chromatic aberration if you are familiar with that concept.

The GDD depends on:

1)  The amount and type of glass in the system (and therefore on the
objectives used)
2)  The wavelength of light (typical glasses have lower GDD as one
approaches 1.3 um).
3)  The length of the pulse of your laser (short pulses are very sensitive
to GDD)

In your case, your chameleon has a relatively long pulse length (140 fs),
and will therefore not be very sensitive to even relatively large amounts
of GDD.  Personally, I do not bother compensating GDD on our Chameleon
because I found that it had a very minor effect on image contrast (although
I am using scan optics that are optimized for low GDD).

However, since you have GDD correction built in, you might as well use it.
Take a slide filled with the fluorophore of your choice and use your
preferred objective + wavelength.  Then adjust GDD until the image
brightness is maximized.  I recommend using low power and concentrated
fluorophore to minimize photobleaching.  You can repeat this for each
objective and wavelength if you are determined, but the difference will
likely be insignificant unless you are using very widely spaced wavelengths
or extremely dispersive objectives.

Hope that helps,
Mike


On Wed, Nov 12, 2014 at 3:44 PM, Michael Moore <[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.
> *****
>
> I'm a new member to the confocal listserv
>
> Can someone explain GDD in regards to multiphoton imaging?
> And how is GDD adjusted.
>
> We currently have a Coherent chameleon vision II that has GDD.
>
> I have been told conflicting instructions on how the GDD is adjusted or
> used for imaging.
>
> Maybe I just don't understand how GDD works.
>
> for one, is GDD adjusted for each objective used?  is it independent of the
> objective?
>
> Thanks to all who reply.
>
> Mike
>

[Craig Brideau]

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That is a question requiring a fairly detailed answer. I have a short paper
on it I wrote for Photonics West 2009 that I've passed along. Hopefully
that will get you started, and I recommend you skim my references.

Craig Brideau

On Wed, Nov 12, 2014 at 1:44 PM, Michael Moore <[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.
> *****
>
> I'm a new member to the confocal listserv
>
> Can someone explain GDD in regards to multiphoton imaging?
> And how is GDD adjusted.
>
> We currently have a Coherent chameleon vision II that has GDD.
>
> I have been told conflicting instructions on how the GDD is adjusted or
> used for imaging.
>
> Maybe I just don't understand how GDD works.
>
> for one, is GDD adjusted for each objective used?  is it independent of the
> objective?
>
> Thanks to all who reply.
>
> Mike
>

[Craig Brideau]

*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
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*****

Note that short pulses can also increase photodamage, so you may have to
find a balance between pulse-width, power, signal, and damage.

Craig

On Wed, Nov 12, 2014 at 2:21 PM, Michael Giacomelli <[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 Mike,
>
> GDD is the group delay dispersion, the difference in time between different
> wavelengths of light when passing through a system.  It represents the
> tendency of shorter wavelength components of a pulse to travel at a
> different speed through glass than longer wavelengths.  Its is the temporal
> analog of chromatic aberration if you are familiar with that concept.
>
> The GDD depends on:
>
> 1)  The amount and type of glass in the system (and therefore on the
> objectives used)
> 2)  The wavelength of light (typical glasses have lower GDD as one
> approaches 1.3 um).
> 3)  The length of the pulse of your laser (short pulses are very sensitive
> to GDD)
>
> In your case, your chameleon has a relatively long pulse length (140 fs),
> and will therefore not be very sensitive to even relatively large amounts
> of GDD.  Personally, I do not bother compensating GDD on our Chameleon
> because I found that it had a very minor effect on image contrast (although
> I am using scan optics that are optimized for low GDD).
>
> However, since you have GDD correction built in, you might as well use it.
> Take a slide filled with the fluorophore of your choice and use your
> preferred objective + wavelength.  Then adjust GDD until the image
> brightness is maximized.  I recommend using low power and concentrated
> fluorophore to minimize photobleaching.  You can repeat this for each
> objective and wavelength if you are determined, but the difference will
> likely be insignificant unless you are using very widely spaced wavelengths
> or extremely dispersive objectives.
>
> Hope that helps,
> Mike
>
>
> On Wed, Nov 12, 2014 at 3:44 PM, Michael Moore <[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.
> > *****
> >
> > I'm a new member to the confocal listserv
> >
> > Can someone explain GDD in regards to multiphoton imaging?
> > And how is GDD adjusted.
> >
> > We currently have a Coherent chameleon vision II that has GDD.
> >
> > I have been told conflicting instructions on how the GDD is adjusted or
> > used for imaging.
> >
> > Maybe I just don't understand how GDD works.
> >
> > for one, is GDD adjusted for each objective used?  is it independent of
> the
> > objective?
> >
> > Thanks to all who reply.
> >
> > Mike
> >
>

[Mark Cannell-2]

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*****

Hi

Have a read of this, I think it gives a relatively easy to understand description of the problem and its solution:
Soeller, C. & Cannell, M.B., 1996. Construction of a two-photon microscope and optimisation of illumination pulse duration. Pflügers Archiv : European journal of physiology, 432(3), pp.555–561.

HTH

Cheers



On 12/11/2014, at 8:44 pm, Michael Moore <[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.
> *****
>
> I'm a new member to the confocal listserv
>
> Can someone explain GDD in regards to multiphoton imaging?
> And how is GDD adjusted.
>
> We currently have a Coherent chameleon vision II that has GDD.
>
> I have been told conflicting instructions on how the GDD is adjusted or
> used for imaging.
>
> Maybe I just don't understand how GDD works.
>
> for one, is GDD adjusted for each objective used?  is it independent of the
> objective?
>
> Thanks to all who reply.
>
> Mike

Mark  B. Cannell Ph.D. FRSNZ
Professor of Cardiac Cell Biology
School of Physiology &  Pharmacology
Medical Sciences Building
University of Bristol
Bristol
BS8 1TD UK

[hidden email]

[Craig Brideau]

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*****

Really good early work. I basically redesigned the prisms but used the same
compressor design as Soeller. The key change I made for my own work was to
use a higher-index glass so the prisms didn't have to be so far apart to
achieve a given -GVD. The trick was to balance out the Abbe value for the
bandwidth of the laser so I induced mainly second order but not much third
order dispersion.

Craig


On Wed, Nov 12, 2014 at 4:06 PM, Mark Cannell <[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
>
> Have a read of this, I think it gives a relatively easy to understand
> description of the problem and its solution:
> Soeller, C. & Cannell, M.B., 1996. Construction of a two-photon microscope
> and optimisation of illumination pulse duration. Pflügers Archiv : European
> journal of physiology, 432(3), pp.555–561.
>
> HTH
>
> Cheers
>
>
>
> On 12/11/2014, at 8:44 pm, Michael Moore <[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.
> > *****
> >
> > I'm a new member to the confocal listserv
> >
> > Can someone explain GDD in regards to multiphoton imaging?
> > And how is GDD adjusted.
> >
> > We currently have a Coherent chameleon vision II that has GDD.
> >
> > I have been told conflicting instructions on how the GDD is adjusted or
> > used for imaging.
> >
> > Maybe I just don't understand how GDD works.
> >
> > for one, is GDD adjusted for each objective used?  is it independent of
> the
> > objective?
> >
> > Thanks to all who reply.
> >
> > Mike
>
> Mark  B. Cannell Ph.D. FRSNZ
> Professor of Cardiac Cell Biology
> School of Physiology &  Pharmacology
> Medical Sciences Building
> University of Bristol
> Bristol
> BS8 1TD UK
>
> [hidden email]
>

[Debora Keller]

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*****

Hi,

Following up on the effect of pulse-width and photo-toxicity, I would also have a look at the
following paper from the Beaurepaire lab:

Débarre D, Olivier N, Supatto W, Beaurepaire E (2014) Mitigating Phototoxicity during
Multiphoton Microscopy of Live Drosophila Embryos in the 1.0–1.2 µm Wavelength Range.
PLoS ONE 9(8): e104250. doi:10.1371/journal.pone.0104250

Principles should be applicable to other organisms (me thinks)

Debbi