Re: pre-chirping (what diagnostics to use)

Posted by Shalin Mehta on
URL: http://confocal-microscopy-list.275.s1.nabble.com/Re-pre-chirping-what-diagnostics-to-use-tp590162.html

Search the CONFOCAL archive at http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal Dear Jerry and others,

 What diagnostics do you use for tuning of two photon laser or OPO? Is laser spectrum analyzer enough?

We have a shared two photon (MIRA 900F Femtosecond configuration) and OPO from Coherent. One of the main user is very afraid of tuning it - so he always has a service engineer tune it to 830nm and longest possible pulse (since he does spectroscopy). There are two more of us who will benefit by tuning it for two-photon and SHG (different wavelengths and shortest possible pulse).
How is the 'reproducibility' of laser beam profile when working with these lasers? One of the main concern that other user has is that - if you cannot come back to exactly 830 nm after tuning to say 740 nm, the custom optical setup will go out of alignment.

Thanks
Regards
Shalin

On 8/30/07, Mark Cannell <[hidden email]> wrote:

Search the CONFOCAL archive at
http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal

Hi Gerry

The typical path using 2 prisms is via a small mirror into the first
prism (we set this at minimum at minimum deviation but this can be
changed to alter chirp). Then to the second prism (at minimum devation
to produce a collimated horizontally spread spectrum), and then two
mirrors to reflect the light back and displace the beam vertically which
then passes back through the second and first prisms respectively. After
the beam has left the first prism, note the beam has been displaced
vertically is and thereby separated from the input beam.

BUT are you sure you need to do this? If the input pulse is ~120 fs the
pulse broadening is quite minor. We used a pair of gold mirrors to to
return and displace the beam but if you have 1" fs mirrors they would
work as well.

For typical prism spacing see:

Soeller, C. & Cannell, M.B. (1996) Construction of a two-photon
microscope and optimisation of  illumination pulse width. _Pflugers
Archiv_ 432: 555-561.

Cheers Mark

Jerry Sedgewick wrote:
> Search the CONFOCAL archive at
> http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>
> I am interested in setting up pre-chirping in the laser path going to
> a custom built multiphoton. I have been searching in vain for exact

> information on the components. I bought the prisms, but I am uncertain
> about the first mirror that directs the laser to the prisms (and then
> allows the returning, reflected laser to pass through), and the second
> mirror. My guess is that the first mirror must be a linear polarizer,
> or a polarizer that separates the s and p polarization. The second
> mirror must be a grating of some sort that re-polarizes the laser so
> that it passes through the first mirror.
>
> Rather than guessing, it would make my day if I could get specifics on
> the mirrors.
>
> Thanks!
>
> Jerry Sedgewick

--
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Shalin Mehta, Graduate student
Graduate Programme in Bioengineering, NUS, Singapore
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