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If you don't need to change the laser power too quickly, and don't mind
doing it manually, then a half-waveplate and polarizer combination works
very well. Set the polarizer at an angle where you get the best
fluorescence for a given output power of the laser (the intervening
optics are frequently polarization dependent).
Sudipta
Dr. Sudipta Maiti
Dept. of Chemical Sciences
Tata Institute of Fundamental Research
Homi Bhabha Road, Colaba, Mumbai 400005, India
91-22-2278-2716
www.tifr.res.in/~biophotonics


On Wed, 20 Jun 2007, Eduard Korkotian wrote:

> Search the CONFOCAL archive at
> http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>
> Dear List,
>
> Not long time ago we've purchased a 2 photon system from different
> sources:  Mai Tai laser from Spectra Physics, FV 300 from Olympus,
> manipulators and stage set from Luigs & Neumann and optical table from
> Newport.
> Obviously, as our laser and confocal control units are not directly coupled
> we can't shutter and attenuate the light beam using Olympus software.
> Additionally, lasers' shutter and intensity control are not really built
> for such fast adjustments as needed during recordings.
> I think, typical solution for the beam shuttering and attenuation problem
> is either acousto-optical modulator (AOM) or electro-optical modulator (so
> called Pockle cell).  People say, that disadvantage of AOM is some
> significant elongation of laser light pulses and Pockle cell produces high
> voltage fluctuations which may disturb electrophysiology and proper work of
> a sensitive amplifier.
>
> So, I would be really thankful if those of you who faced similar
> difficulties and solved them in some way could share their experience.
>
> Sincerely,
> Ediard Korkotian,  Ph.D,
> Neurobiology, The Weizmann Institute,  Rehovot, Israel.
>