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Hi Ernst,

You could start by checking the output of the new laser to make sure that it
is Gaussian (just project it on to a wall) and use a mode-cup to make sure it
is singlemode otput.  If all this is as it should be, then you can assume that
the problem is with the coupling, the coupling optics, or the fiber itself.
If this is a Point-Source fiber, I would expect the optics to be okay (they're
encased pretty tightly).  You can get some beam distortion if you are not
exactly hitting the center of the fiber (hitting the cladding sometimes causes
distortions or vignetting).  You can also check the tip of the fiber under
slight magnification for burns or scratches. But if you are sure that the
fiber has been handled with care then you can most likely rule out fiber
damage as well.

If the laser beam quality is as expected (gaussian, singlemode), I would
suspect the laser-fiber coupling alignment.

Best of luck!

Mike

>===== Original Message From [log in to unmask] =====
>Search the CONFOCAL archive at
>http://listserv.acsu.buffalo.edu/cgi-bin/wa?S1=confocal
>
>Dear confocalists:
>
>
>After replacing our laser on an MRC1000 and realigning our fiber
>coupling on the input, we observe the following:
>
>1) the beam leaving the fiber is much more divergent than before.
>
>2) In the center of the beam there is a black shadow, shaped like the
>number 8, but with three black circles (not only two, as in 8).
>
>3) Output power is only 25 % of input, although better alignment may
>still improve this.
>
>
>Is this due to bad alignment? Or due to dirt? Or is something broken??
>
>Any suggestion would be greatly appreciated!!!
>
>With best wishes
>
>
>Ernst
>
>
>
>--
>Ernst Niggli
>Department of Physiology
>University of Bern
>Buehlplatz 5
>CH-3012 Bern / Switzerland
>
>E-mail: [log in to unmask]
>
>WWW:
>http://beam.to/Ernst_Niggli
>http://beam.to/calcium_quark

>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Michael C. Adams
Research Technician for Dr. Clare Waterman-Storer
Laboratory of Cell Motility Studies
Department of Cell Biology
The Scripps Research Institute
10550 North Torrey Pines Road, CB 163
La Jolla, CA 92037

TEL 858.784.9244
FAX 858.784.7521
EMAIL [log in to unmask]
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