What diagnostics do you use for tuning of two photon laser or
OPO? Is laser spectrum analyzer enough?
The laser spectrum analyser should get you back exactly to your
wavelength, and give a pretty good idea of the pulse length.
Lastek in Australia make a software system which works with a
spectrum analyser to give you pulse length and it seems pretty
good provided it is carefully calibrated. (It's probably sold
under
some other name in the States).
But if you have users who want to know the pulse length
precisely
it's really worthwhile buying an autocorrelator.
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).
830 is quite OK for SHG (brings the harmonic to 415 which is within
the range of conventional interference filters (they start to
absorb a lot
at anythong shorter). But it's a bit limiting for 2P.
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.
In the early days one make of Ti-S laser was notorious for
beam
wander as you tuned it but even so it should go back when you
returned it to the original wavelength. Nowadays they seem
really
stable, and I don't think your Mira should be a problem
there. The
only thing I find with a Mira is that it's best to let it
warm up for
half an hour before doing any tweaking of the alignments (and
often
that way you find you didn't really need to do any tweaking
anyway).
Guy