Successful DIY CO2 laser, made from scratch!

Pretty cool project!

Just something i'm curious about: Why does this laser require the gas to be refreshed? As I understand most CO2 laser units are sealed, and only require water flow for cooling.

Simply wonderful. This is true DYI, just like those awesome homemade nitrogen lasers... I'd love to have the time to work on one of these projects one day!

Robert

Coooool! I only know one other dude who made a co2 laser, sam g on the laserfaq.

Awesome, now thats a DIY laser!

Enjoyed that CO2 laser very much! Last year I posted your youtube video showing the blue coumarin dye laser. Everyone really enjoyed that. .................................

YouTube - Homemade dye laser using Coumarin

I can see the time and tinkering involved with your
DIY CO2 Laser build...
Nicely done...
You have my attention...

Do You have shares in JB Weld...

Jerry

Benm said:

Pretty cool project!

Just something i'm curious about: Why does this laser require the gas to be refreshed? As I understand most CO2 laser units are sealed, and only require water flow for cooling.

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In theory, it shouldn't. However, a homemade laser leaves much to be desired when compared to the 'real' thing. Gas mix is 'less than optimal'. Cooling is not good enough (notice that my cooling jacket doesn't even extend to the electrodes - for obvious reasons). And most important of all, no system I have made is totally leak free! So if I just sealed my tube off, it would probably be back up to air the very next day. It's seriously hard to make a perfect, leak-free system. 'Real' lasers don't use epoxy the way I am doing. I don't know what they do - I guess the glass is fused directly to the mirrors (Mike - any idea?).

Thanks -
Jarrod

In a tube the glass is sealed everywhere. It goes around the mirrors, which need it the most, and through the arc tube in the middle.

You can sort of see how it works here, the big "bubble" never fills with water.

Benm said:

Why does this laser require the gas to be refreshed?

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It's mostly because of the CO that is created during the lasing process that poisons the lasing process. Sealed tubes have a catalyst in the mix, and the DC current circulates the gas enough so that the catalyst has a chance to work. That spiral tubing helps lengthen the time the catalyst can do it's thing.

I've illustrated the path the gas takes on that sealed tube. Mister Jarrod's tube has no such recirculation built in and probably no catalyst. I can't remember what the catalyst actually is though. The FAQ would know.

Cyparagon said:

It's mostly because of the CO that is created during the lasing process that poisons the lasing process. Sealed tubes have a catalyst in the mix, and the DC current circulates the gas enough so that the catalyst has a chance to work. That spiral tubing helps lengthen the time the catalyst can do it's thing.

I've illustrated the path the gas takes on that sealed tube. Mister Jarrod's tube has no such recirculation built in and probably no catalyst. I can't remember what the catalyst actually is though. The FAQ would know.

Click to expand...

The glasswork in a water cooled laser is really the key to a stable robust system. Getting proper seals and cooling. I've seen large CO2 lasers with platinum electrodes in them, not the main cathode/anode, but along the tube which i always assumed was part of the catalyst to keep the gas mixture fresh. Large CO2 lasers often have to be re-gassed anyway. Maybe more moderns designs have solved this problem?

Your DIY laser is awesome and very inspiring. I am amazed that you are using CO2 generated from sodium carbonate and acetic acid. The impurities in the gas mixture might account for power loss.

You can get good quality CO2, N and He from a welding supply store. With a well calibrated mixture and good quality gasses your laser should really perform! However you might find more weaknesses as the power is increased around cooling and the mirrors.

Very cool and thanks for sharing.

Interesting, i didn't know that as the laser operates the CO2 is broken down to CO,
keep your work area ventilated Jarrod, you don't want that in your blood stream

Jarrod --
Your copper electrodes also contribute to contamination so the flowing gas system makes it work. My tube had side mounted neon sign electrodes with gettering material. That kept the electron flow away from the mirrors and mounts.
If you want a 1" salt crystal, PM me an address.

HMike

That article by C.L. Strong was my bible for the CO2 35 years ago. That was when that SA magazine wasn't so PC.

VERY NICE WORK!!!!! Wow this laser reminds me of the PVC piple laser i built years ago as part of a science fair project in high school. It had the alignment mechanism almost identical to the one you used. My laser used a tube from a quartz heating lamp instead of the neon tube though, and had a PVC pipe cooling jacket. It used an old freon compressor from a car and a grinder motor to make a nice <2 torr vacuum pump. 110V Fridge and AC compressors work but they tend to burn up since the freon is used to cool the motor too.

The gas source was co2 from dry ice, nitrogen from a welding bottle, and helium from a party balloon tank. The hardest parts to find IMHO were the needle valves and the mirrors.

The co2 tubes that are sealed have a small amount of water vapor, free oxygen and some xenon added, this is why their discharge is whitish compared to the purple pink of flowing tubes. Some expensive tubes such as Coherent's have in addition a gold based catalyst that is nano gold on a substrate of zicronium silver aluminum oxide. This same catalyst is applied to the inside of synrad laser tubes too.

^ Good source for needle valves are the surplus parts stores in the Silicon Valley area. They have a lot of bargain basement used semiconductor manufacturing equipment. I spent a lot of time at Intel corp. adjusting gas flows for various processing equipment. Some of it was what is commonly known as world war one nerve gas. We had the Telos gas monitoring stations that would set off an evacuation alarm if there was a gas leak. I "smelled" nerve gas once and the odor was like burned matches and dead fish. Phosphine and Phosporous oxy-chloride(POCL), as well as Arsine and even some Tungsten Hexafluoride(fluorine is nasty). Aaaah the smell of napalm in the morning. ;-) Later on OSHA started to enforce better scrubbers and then we rarely got a whiff. A fellow employee fell to the floor and his legs wouldn't work for half an hour when a stainless line containing Phosphine was severed by mistake. Good times! NOT

Ah, that clarifies things

I have my doubts about the CO though... where does the other oxygen atom go? The only option would be the nitrogen, ending in nitrous oxide. If that actually happens a catalyst could convert them back to nitrogen and co2.

This process would be very similar to an automotive catalytic converter, the active materials being platinum, palladium and rhodium.... expensive stuff
It also needs to be on a substrate and all, making it near impossible to DIY.

Perhaps it would be possible to simply cut a piece from an auto cat and place it somewhere in the gas circulation, but it would need to be fairly hot to work.

From the FAQ

Commercial sealed CO2 lasers have much in common with sealed HeNe lasers. However, you can't just take an axial flow CO2 design, seal it up, and expect the laser to work for more than a few minutes. The discharge process breaks down the CO2 to produce CO and O2 which quickly poison the lasing process. There ARE a number of solutions to this problem including the addition of other gases like H2 or H20 (water vapor) to the gas mix to react with the CO and O2 to regenerate CO2 or the use of a high temperature (300 °C) cathode to act as a catalyst to stimulate recombination.

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