Note: at any picture you can click and magnify to 1024 x 768 pix
I have only few of this plastic cells, but some of this was destroyed due to
"aggressive" solvent which was sometimes use for disolving dyes. I got this
cells from medical laboratory in town's hospital for "free"...
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| This is relative cheap plastic
cell for fluorescence probe, but have two "clear" and two "fuzzy"
windows. At next picture you can found explanation why this cell is not
so good for use as laser dye cell... |
Two "fuzzy" window is not main
problem with this cell, but curved inner edges (red rings). Usually,
lasing action occur near glass surface (or plastic in this case), and
if inner edges are not very sharp, then output "diffuse" and occur as line
instead rounded spot. I was try put mirror behind cell, but not help at
all - output spot on target (paper or wall) looks like coma or line. |
So, after disappointing with this cells, I was try to found at internet who sell "right" quartz cells.
At some page found it, but with "astronomical" price for my budget (read: empty wallet). Only
choice is build my "own" cell. But there also many problems with founding right materials for this
purpose. Firstly, can't found enough thick plastic, so I was glued two thinner plastic together (this
is also big mistake, because at this place dye leak). Secondly, glass windows was glued
with silicone sealant, which do it's job (glue) moderately good between two glasses, but between
glass and plastic sealant not endure solvent and resulted as leaking dye. See pictures:
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| How looks this "miserable
cell"... |
Screw is something like stopper... |
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| Different angle of view... |
Different angle of view (back
side)... |
Now, you can see how dye was leak (Mostly, Rhodamine 6G was "painted" this cell)
This is last time that I will make something like this "leaky" cell...
But, however, it is not so "black" with this dye cell. This cell was work moderately well.
Few next pictures represent how it work. And my apologize for few blurry pictures,
because in this time I make this picture "from hand" without tripod (and with my old film
camera), so result is "out of focus" or "stressed pictures". Now I have good digital camera
and you can see better pictures above (pictures of plastic and "my" dye cell).
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| Upper left is N2 laser in
"sandwich" between dumper (behind) and peaker (above) capacitors. White
cube is spark gap with screw for adjusting repetition rate. Next to N2
laser is little cylindrical lens puled from laser photocopier machine
and with too long focus - about 25 cm. Bottom right is whole setup with
angled dye cell between two mirrors. |
Sorry for this really blurry
picture. There is focused line from N2 laser. Left to dye cell is OC
(output coupler) which is another wrong choice, because it is actually
"beam splitter" with 70% reflectance (too much - more laser light was
suppressed than transmitted), and it is not concave mirrors, so it
represent "unstable resonator" which is "nightmare" for adjusting. (reason
why you can't see laser beam is that I was not "smoke"
into laser head this time) :o) |
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| Less blurry picture. Left to dye
cell is aluminum first surface mirror. Now explanation why dye cell is
angled. If you carefully look at picture, you can see a pair of
reflected laser beams from glass surfaces (and then from rear mirror).
In case that dye cell is not angled at all, this "unexpected"
reflections make another "nightmare" for mirror alignment and "ghost"
output spots. One more things - because OC mirror have too much
reflectance, and if you carefully look brightness of laser beam between HR
mirror and dye cell, and output beam, you can see that output beam is
less bright. This is because duration of laser pulse is too short, and
laser beam only few times passes through dye cell. Higher reflectance
of OC mirror is welcome in case that dye have very low gain, but there
is Rhodamine 6G, which have enough high gain that produce laser beam
without any mirrors as "superradiant" laser. (Later was remove OC
mirror, and got better results with only rear mirror, but with two mirrors,
laser looks better...) :o) |
Another, really blurry picture
which represent (near) rounded spot. Note: behind this spot is another
oval spot which is actually reflectance on desk surface of spot from wall. |