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My experience with diode lasers is limited, but at the very least, maybe I can
provide some food for thought.
Light output from diode lasers is highly divergent compared to an argon ion
laser and it may be multimodal as well. I expect that your problems might
arise because of the beam characteristics of (most) diode lasers.
Here is an excerpt from "Sam's Laser FAQ", my favorite laser resource:
"Unlike the helium-neon and other common gas lasers (as well as most other
types of lasers), the raw output beam from an edge emitting (also called Fabry
Perot or FP) laser diode (the most common and until recently, only
commercially available types) is highly divergent and suffers from two
asymmetries: astigmatism and an elliptical beam profile. The beam is also
inherently linearly polarized. These all follow directly from the shape of the
emitting aperture of the edge emitting laser diode end facet which is highly
elongated rather than circular."
In comparison, most argon ion lasers have only slightly divergent beams and
the output is singlemode. If you are unsure of the mode of your beam, acquire
a mode-cup (I believe coherent sells one). This can be used to spread your
beam onto a wall, then the mode of the beam will be easily recognized
(multimode beams have a speckled appearrance).
More info on diode lasers, their beam characteristics and corrections for
inherent asymmetries can be found at the following link:
http://members.misty.com/don/laserdio.htm#diobcc
Good luck!
Mike
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>Quoting [log in to unmask]:
>
>> The problem is noise, both very high frequency (within each scan line) and
>> very low (between scans). A power meter at the laser head shows steady
>> output, but the images tell a different story entirely.
>
>This is exactly the story I heard from Colin Sheppard's lab some
>time ago but since I didn't have direct experience I didn't want to
>say too much on hearsay.
>
>>Somehow going
>> through two fibers, an AOTF and a scan system does not agree with this
laser.
>> I think they are using the wrong type of fiber, but they won't admit it
and
>> try the upgrade.
>
>Well, Colin's group weren't using any fibres or AOTFs and the message
>I got was that it seemed to be an inherent characteristic of the
>laser. There must be some serious laser jocks out there who can
>help on this one.
>
>If you have a 4 line Argon laser and a 408nm violet diode you
>should have all bases pretty well covered without needing HeCd and
>at no greater cost. Do be aware that on a machine like the Leica
>which has a laser power control as well as an AOTF you must be
>running the laser at full power to get the 457nm line.
>
>The other thing I've heard is that all violet diode lasers are
>not created equal ... does anyone have practical experience with
>these?
>
> Guy
>
>
>--
>Associate Professor Guy Cox
>Electron Microscope Unit, F09
>University of Sydney NSW 2006
>+61 2 9351 3176
>
>Until 25th July:
>Instituto Gulbenkian de Ciencia, PT-2780-156, Oeiras, Portugal.
>+351 21 446 4638 (office) or +351 91 401 5726 (mobile)
>Fax: +351 21 440 7970
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
Michael C. Adams
Microscopy & Imaging Manager 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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