Some comments from the poor side of town (ie, those of us who cannot
afford to replace their lasers every year).

I have argon-ion lasers that have been working over 2000 hours, and
still as strong as new. On the confocal (Biorad-1024) I use a 100mW
laser at  1/2 its max tube current, and after 1500 hours it is as new
(our microscope is not that heavily used since I am the only operator at
present). By "as new" I mean that when the output was measured at the
original tube current, it was the same as the day we installed the
system. Doing multilabel work (especially triple labeling) is harder,
but not impossible. I find that 514nm works for FITC, CY3 (or TRITC),
and texas red, but it takes effort to balance the channels (in my next
life I want 12 bits/channel...).

The tube is guaranteed for 5000 hours or one year, but I have a laser
that was made in 1983 and still working (I dont know how many hours, but
I inherited it in 1988...). I have heard that part of the problem with
argon-krypton lasers is that they are mixed gas. I also heard that once
upon a time Meridian offered as a second laser a krypton only laser. Is
this true? Does such a beast exist?

It would seem to make sense to get a two laser system -- argon-ion plus
HeNe. However, a 543nm HeNe may still excite FITC a bit. I see this with
a 545nm narrow band excitation filter in conventional fluorescence.
There are also yellow HeNe lasers, which might be a good choice.

I wonder if reducing tube current is really a good thing to do to extend
laser life. Thermal cycling can sometimes be worse than steady
operation. Has anyone compared tube life with and without the automatic
reduction to standby? Also, what does this do to the power stability?

Since the lasers  are often under light control, it might be agood idea
to check mirror allignment. Otherwise, tube current will rise to
compensate for the misallignment, and the laser will run hotter.

--aryeh
--
Aryeh Weiss                          | email: [log in to unmask]
Department of Electronics            | URL:
http://optics.jct.ac.il/~aryeh
Jerusalem College of Technology      | phone: 972-2-6751146
POB 16031                            | FAX:   972-2-6751275
Jerusalem, Israel                    | ham radio: 4X1PB/KA1PB