m cannell  says:

     Dear Steve

     I was suspicious of the use of an AOM in the 510. Our experience
of
     AOM's with femtosecond lasers has been difficult since the AOM
uses diffraction    and the  band width of the pulse is quite large.
This leads to marked changes   in the beam  profile with the
wavelengths spread across the beam. This is of course   not such
     a problem with the narrow bandwith associated with 1P laser lines.
I   don't know  if the 510 has a way of overcoming this but if it
hasn't then the  pulse shape may be quite different due to the loss of
wavelength components as the  rear  aperture is over-filled... We have
since given up using AOM for
beam  intensity  control and now use a Pockel cell which works really
well. A simple  fix might be  to remove the AOM from the 2P path, but
I'm guessing here...

     My 2c worth.

     Mark Cannell

     Steve Potter wrote:

     > Steve Potter  says:
     >
     > Dear Vera,
     > You hit a nerve.
     > We have had the fiber-delivered coherent/Ziess 510 for a while.
I   have not
     > really used it since the original Vitesse laser (on loan) was
replaced with
     > a tunable Mira900.  When we had the Vitesse, it was
_very_stable.  I dont
     > think there were any temp problems with the pre-chirper.
     >
     > But since we got the tunable laser installed, we have had no end
of  problems
     > getting the Group Dispersion Compensator (GDC) and the
Acousto-optic
     > modulator (AOM) within it aligned at different wavelengths.  It
seems the
     > AOM that Ziess fit into it has a very small acceptance aperture.
 I have to
     > say the system is
     > definitely no longer a 'turn-key' system (as it was with the
Vitesse), and
     > we are seriously considering using mirrors instead.
     > Keep in mind that all this is what I have heard from other users
in  the lab,
     > primarily Mary Dickinson ([log in to unmask]) and Yan Wu
     > ([log in to unmask]),
     > since I have not really used the scope (I like my old
Sarastro...).       Please
     > contact them for more details.
     >
     > I should note that mirrors can be just as sensitive to temp
fluctuations.
     > I have the ones on the scope I put together on very solid
mounts,   and
     > covered to reduce thermal transients, dust, bumping, and eye
hazards.
     >
     > Political note:  Coherent has had their top techs in the lab
almost  every
     > other week fixing and adjusting things to make this system work.

     Special
     > kudos to
     > Briggs Atherton, Bill Kapinski, and Ron Brady.  While Ziess
sales   reps are
     > often here too, the techs that actually know about the AOM and
can   fix these
     > problems have only been to the lab for the original
installation.  A  number
     > of times, Zeiss invited potential customers by to demo the
system,  an
     > couldnt get it to work properly in 2-photon mode.  Embarrassing
for  all.
     > We are all hoping they get their act together.
     >
     > Also, at present, due to high-order non-linearities in the
fiber,   not much
     > power can be put through it ( will solve this soon, but until
then, if you need lots of power,  mirrors
     > are the way to go.
     >
     > Steve Potter
     > [log in to unmask]
     >
     > >Vera Chlumecky  says:
     > >
     > >
     > >WE are in process of purchasing a new confocal + 2-photon
system.
     > >Requirements of our users call for the purchase of upright and
inverted
     > >microscopes that are freely interchangeable. The coherent
femtosecond Ti:S
     > >laser will then require fiber delivery using the GDC-XW-Zeiss
kit  to ensure
     > >adjustable dispersion compensation and pulse duration at the
fiber  output.
     > >It has become to our attention that the fiber delivery is
extremely
     > >sensitive to temperature flactuation and will require
continuous  rather
     > >demanding adjustments. This does not seem to be the case with
direct mount
     > >of the laser. Could you share the experience with the fiber
delivery, use
     > >of interchangeable microscopes or does anyone have such a
set-up  installed.
     > >Is than the direct mount not less problems and more suitable
for a
     > >multiuser facility. Thanks,
     > >
     > >
     >
     >

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______________________________________________________________________
     ____


______________________________________________________________________
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     MPLSM-USERS, the Multiphoton Microscopy Mailing List
     Steve M. Potter, PhD, Administrator
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send the message body "info mplsm-users"   to  Member blurbs:
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