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Dear Eduard

A couple of years ago we were doing 2 photon photolysis (with confocal 
Ca^2+ imaging and patch clamp). Since we had an open optical bench we 
just put a polarizing filter (photography supply) in the beam path. By 
rotating the filter we could adjust the power.

Later, my former mentor upgraded the system. He used a Sutter Lambda 
10-2 filter wheel (or similar if I recall correctly). It contains 10 
slots for 1" filters, the maximal switching time between adjacent 
filters was 50 ms. The slots where filled with different strengths of OD 
filters incl. totally closed and totally open. With computer control he 
could run a protocol for the filter wheel and generate series of 2P 
pulses of different power.

Hope this helps.

Cheers

Franco

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.

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