Re: polarized vs unpolarized lasers

Posted by Sudipta Maiti on
URL: http://confocal-microscopy-list.275.s1.nabble.com/Re-Recommendations-for-commercial-multi-photon-system-purchase-tp3499069p3623534.html

Ususally the polarization changes pretty fast, certainly it does for my
unpolarized (randomly polarized) HeNe, so that I do not see any problems
in the image. I also
looked at the output fluorescence emission  at a 10 microsecond level
through a polarizer, and
saw no fluctuations. Of course, pixel residence times are somewhat smaller
than 10 microseconds.
Sudipta
  On Thu, 10 Sep 2009, Aryeh Weiss wrote:

> Our Nikon rep has recommended to a C1 user to replace a failing 543nm HeNe
> laser with an unpolarized 2mW laser. This C1 has no AOTF, and combines three
> beams into a fiber which feeds the scanhead.
>
> I was under the impression that using an unpolarized laser is a bad idea
> because I recall that in an unpolarized HeNe, two orthogonal polarization
> modes lase together, but they drift across the bandwidth of the cavity as the
> laser warms up. This results in a slowly varying change in the relative
> polariation of the beam over time. In a system where reflections from
> dielectric surfaces can be dependent on polarization, this should be a
> problem. If the fiber is polarization preserving, it should be a big problem.
>
> So -- does anyone out there know if my understanding is correct? Is anyone
> using unpolarized HeNe lasers with no problem? I assume that Nikon would not
> be offering that laser if there was such a problem inherent to it, but
> still...
>
> --aryeh
>

--
Sudipta Maiti
Dept. of Chemical Sciences
Tata Institute of Fundamental Research
Homi Bhabha Road, Colaba, Mumbai 400005, India
91-22-2278-2716
www.tifr.res.in/~biophotonics