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We have done measurements, where , with a 100 femtosecond pulse
duration, the pulse duration after the objective was about 200 fs. With
a 200 fs input pulse duration, the pulse duration after the objective
was 220 fs. This is explained by the fact that longer pulses have a
smaller spectral bandwidth, and therefore experience less temporal
broadening due to dispersion. A 50 fs pulse would experience even more
stretching. Our experience is that, depending on the optical set-up
used, a laser pulse duration between 200 and 300 femtoseconds is a
reasonable trade-off.

Eric Mottay
Amplitude Systemes

> Search the CONFOCAL archive at
> http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>
> I have another principle question regarding the pulse-streching, it is
> mainly for general interest, but we run a directly coupled 2P laser also.
> There is also glass in the microscope (at least the lens). Are there
> estimates in how far this influences the peaks/pulses?  What one has to
> roughly expect in the sample, e.g. when the pulse had 50 or 100 fs before
> entering the optical system ?
> Arthur
>
> At 03:59 17.03.2004, you wrote:
>
>> Search the CONFOCAL archive at
>> http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>>
>> John Runions wrote:
>>
>> > Ok, I've got to ask.  What is prechirp?  I've never heard the term
>> before
>> >today and I want to be able to use it in conversation at parties.  Over
>> >and out, John.
>>
>> A fibre - like any glass - has dispersion which means that red
>> light travels faster than blue.  A femtosecond pulse has a spread
>> of wavelengths (of a few nm) and since these travel at different
>> speeds the pulse becomes longer by the end of the fibre.  Prechirping
>> means retarding the longer wavelengths so that the shorter ones
>> are in front.  Then they all come together again at the end of the
>> fibre.  Obviously the amount of prechirp has to be carefully matched
>> to both the length of the fibre and the pulse length.  A fiddly
>> business and best avoided if possible!
>>
>>                                                 Guy
>>
>> Assoc. Prof. Guy Cox,                 ooOOOOOOoo
>> E.M. Unit, F09            #       oOOOO  |  |  OOOOo       #
>> University of Sydney     ###    OOO|  |  |  |  |  |OOO    ###
>> NSW 2006, Australia      ###  OOO  |  |  |  |  |  |  OOO  ###
>> Ph:  02 9351 3176        ### OO |  |  |  |  |  |  |  | OO ###
>> Fax: 02 9351 7682       #####   |  |  |  |  |  |  |  |   #####
>>                       ==#####============================#####==
>> http://www.guycox.net   #####                            #####
>> http://www.guycox.com ~~#####~~~~~~~~~~~~~~~~~~~~~~~~~~~~#####~~
>
>
>
> Dr. Arthur Schuessler
> Institute of Botany, FB10, TU Darmstadt
> Schnittspahnstrasse 10
> D-64287 Darmstadt
> GERMANY
>
> Fax: ++49 6151-166049
> e-mail: [log in to unmask]
> http://www.geosiphon.de/
> http://amf-phylogeny.com/
>
>

--
Eric Mottay
General Manager
Amplitude Systemes
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