Best sources for lasers

These are all of the old posts from the first two years of the forum. They are locked.
Updated: 2005-03-28 by HoloM (the god)
Dale Wood

Best sources for lasers

Post by Dale Wood »

Colin,
Thanks so much for your effort in this endeavor!
I have, for many years, always wanted to experiment with holography as a hobby but only recently had the money and time to pursue this. Only just now started construction on my little lab.
Of course there is much written material on the subject but I was shocked at the lack of forums! Frank's was fine but he is obviously a very busy man...never could get a response about purchasing one of his diode drivers.

If anyone has the time, here are some questions:

1) Best source for decent lasers? Has anyone bought from laser amazers.com? Their prices seem, well... amazing.
2) If you're interested in red diode lasers in the 25 to 50mw range what tech specs should you look for? 635 or 650nm? What make diode has proved the most reliable?
3) I am surprized to discover that my budget will probably allow the purchase of one additional laser...it will probably be a green DPSS.(Should I expect a shorter coherence length?) Still, I have to admit an interest with the air-cooled 50mw blue argon currently offered by L.A. I would greatly appreciate info from anyone with recent experiance with this type laser; particularly regarding the availability and pricing of film.

Once again, thanks to you and to all who have answered questions on both Frank's and Yahoo's site.
Colin Kaminski

Best sources for lasers

Post by Colin Kaminski »

I wonder what the coherence length is on the 50mw Argon laser? I have been looking for a argon laser. The fan would cause some problems, but if you put the laser in a separate room from the holography table you could make it work. This would be tough to do with a inner-tube suspended table because of the change in height.
Martin Mueller

Best sources for lasers

Post by Martin Mueller »

...and where to get a single-frequency DPSS?
Colin Kaminski

Best sources for lasers

Post by Colin Kaminski »

There are a large number of single frequency DPSS lasers available. I am not sure if they are required for holography. I am doing some tests. I'll let you know what I find. I think a 100mw single frequency DPSS laser could be constructed for $1000.

The Holography Marketplace offeres many suppliers for those with unlimited budgets.
Martin

Best sources for lasers

Post by Martin »

Thanks. Note, there is a Chinese company selling a 20mW single-frequency for $1000.

With regards to green DPSS pointers I am skeptical. Three years ago I tested one of Casix' 10mW pointers. Unfortunately, it did not work - coherence length was shorter than 1mm.


Colin Kaminski

Best sources for lasers

Post by Colin Kaminski »

It would not be too hard to build a 100mw DPSS ring laser with a faraday rotator to insure single direction operation. It would take some fiddling and about $1000 in parts.

See: Solid State Laser Engineering by W. Koechner


Dale Wood

Best sources for lasers

Post by Dale Wood »

Thanks guys.

Hadn't thought about fan problems. Duh.

Coherence length of 1mm? Great! Finally I can make holos of spider mites!!

All joking aside, in reading about the problems people are experiencing with their diodes over 25mw, I probably should stick with a used HeNe until someone comes up with a reliable alternative. There must be some company out there willing to compete with Samurai Lasers! 4000 euros is a lot to gamble on a product people are unfamiliar with. Seriously, not all of us have the time to learn, and experiment with, both holography and electronics.

Colin Kaminski

Best sources for lasers

Post by Colin Kaminski »

The best solution I have used is a constant current driver on a mitsubishi 35mw diode. Which is as simple as a 2 batteries and two resistors. Mount the diode into a housing and make no effort to heatsink it. It takes about 15 minutes to stabilize but works well most of the time. The advantage to HeNe is the coherence length is over 2 meters! I used to equalize my path lengths but now it is common for me to have path length differences of over .5 meter. My tests show that the coherence length of the diode is either 0 while mode hopping or greater than 2 meters and never in-between. You could have 30mw of power with long coherence lengths for less than $100.

Tom and Jonathan have reported sucess with listening to the photodiode with an amplifier to detect stability. Also people have been using a piece of plate glass to divert a 8% beam to an interferometer.

Take a look at:

http://home.pacbell.net/colinsk/holo/

This shows the heatsink/peltier method I am testing (As well assome other drawings people have asked me for). When I get perfect results I will publish all of the information needed to duplicate my system.




Tom B.

Best sources for lasers

Post by Tom B. »

On your Peltier heatsink drawing I noticed a pair of 6/32
stainless screws connecting the heatsink to the
cold side - have you considered substituting nylon
screws to break the thermal short-circuit? Nylon
would also be good here because it would be hard
to tighten them enough to crush the Peltier.
Colin Kaminski

Best sources for lasers

Post by Colin Kaminski »

I was unable to get enough force on nylon screws. I am looking into other ways to have less of a "cold bridge" from my mounting.
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