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One practical reason not to use wavelengths as high as 988 nm is that
you get absorption by water (humidity) and thus have to "flood" your
laser system with dehumidified nitrogen.

regards
Chris

Jason Goh wrote:

>Search the CONFOCAL archive at
>http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>
>Hi all,
>
>At the moment I'm designing a variant on a two-photon fluorescence microscope and as an optical engineer, have a question on a practical aspect of the operation.
>
>I'll be using fluorescein (FITC - excitation peak 494nm) as my fluorophore which would suggest a two-photon excitation wavelength of 988nm.  In the literature, I've not seen anyone use an excitation wavelength this high - mainly seems to be <800nm.  Is there any practical reason for this?  Is it due to decreased laser efficiency outside the optimum running wavelength (approx. 800nm).  I would have thought it was always best to operate at the excitation peak of the fluorophore to get more emission for the same amount of incident power...
>
>Thanks in advance for your help,
>Jason
>
>----------------------------------------------------------
>Dr Jason Goh
>School of Electrical & Electronic Eng.
>University of Nottingham
>TEL:  +44 (0) 115 951 5556
>FAX:  +44 (0) 115 951 5616
>
>
>
>

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Abteilung für Allgemeine Zoologie
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