Crazy and idiot idea : Replace co2 with HeNe to build a POWERFUL hene laser?

[Axxel]

Dear friends.

I have 2 co2 80W tubes out of order. I got a crazy idea. I have a friend that made neon signs so I hope he can be competent to help me doing this.

I want to refill the co2 tubes but with HeNe mixture. For the moment I don't sudied proportions, pressure, which type for mirrors I have to replace and electrical power supply...

Imagine like 10W of pure red visible laser

I just want to know if this is teorically possible? If someone has already attempted to making it?

If nobody has tried and if you think it is theorically possible, I'LL TRY TO MAKE IT!!!

Regards

 

[bostjan]

It'd probably be easier to just build a HeNe from scratch. The optics, electronics, etc., will all be very different between the two, so, by the time you replace everything except the glass tube, I doubt it'd be worth the trouble. I've never personally seen a HeNe in the >50 mW power level range, and there's probably some reason why.

 

[CurtisOliver]

Sure you can have a 10000mW HeNe, if you rate it like the Chinese. On a serious note. No you can't be expecting to transform a CO2 tube into a HeNe without a great deal of patience and determination or any concept of efficiency. Making your own HeNe would be the most effective way. Like bostjan also said, 50mW is some of the most powerful HeNe's that have been seen. CO2 tubes are best for one thing, CO2 lasers.

 

[Sowee7]

It'd probably be easier to just build a HeNe from scratch. The optics, electronics, etc., will all be very different between the two, so, by the time you replace everything except the glass tube, I doubt it'd be worth the trouble. I've never personally seen a HeNe in the >50 mW power level range, and there's probably some reason why.

the highest power hene ever produced was a 2m long one, it lased about 150mw of 632.8nm red

 

[lasingfox]

one, you'd need an entirely different power supply if you were to do that. two, you'd need a precise gas ratio of about 7:1 HeNe, pure and expensive isotopes of both helium and neon and like said above, a ton of patience. you'd need to smash the outer envelope and water cooling jacket to install a new cathode, getter, and even if you decided to do that, the bore diameter is likely too big to begin with... Then add a new outer envelope, buy custom mirrors to seal and align them. now after all that trouble, you'll probably get results a modern 6-10 inch tube would easily outperform. in all honestly, it'd be easier to start with just a glass pipe than a chinesium CO2 laser. Its not impossible just the construction of CO2 lasers are optimized for CO2 lasers..

 

[Photonjunky]

the highest power hene ever produced was a 2m long one, it lased about 150mw of 632.8nm red

You're referring here to the Spectra-Physics Model 125...I've had a couple of these. With a new tube, and RF stabilization, I got a max of 130mW of 6328, 15mW of 6118 orange, and 2-3mW of 5943 yellow. The rear reflector on the 125 is a broadband-coated Littrow prism, to allow for color selection.
Even with all the high-power diodes available now, I still miss the 125...

 

[lasingfox]

You're referring here to the Spectra-Physics Model 125...I've had a couple of these. With a new tube, and RF stabilization, I got a max of 130mW of 6328, 15mW of 6118 orange, and 2-3mW of 5943 yellow. The rear reflector on the 125 is a broadband-coated Littrow prism, to allow for color selection.
Even with all the high-power diodes available now, I still miss the 125...

how'd you manage to get 594? I've only been able to barely squeeze out 604 but not anything stable.. I believe the prism is only coated for 632.8 and 612 and my OC really only does 632.8.. i have to use a second krypton ion OC on the output to get anything else

 

[Sowee7]

You're referring here to the Spectra-Physics Model 125...I've had a couple of these. With a new tube, and RF stabilization, I got a max of 130mW of 6328, 15mW of 6118 orange, and 2-3mW of 5943 yellow. The rear reflector on the 125 is a broadband-coated Littrow prism, to allow for color selection.
Even with all the high-power diodes available now, I still miss the 125...

Yes, that's the one I'm referring to, I forgot the name

 

[Mattronium]

I'll just agree with what most other comments are saying.
From a practical perspective essentially everything would have to be swapped for it to work, and at that point you are just building a HeNe from scratch. And on the aspect of power differential between HeNe and CO2, the difference in power is related to different efficiencies roughly 30% vs 0.1%. DIY HeNe lasers can be made, but aren't easy and aren't a practically way to get more power.

For anyone curious, Sam''s laser FAQ is an obligatory resource: https://www.repairfaq.org/sam/laserchn.htm#chntoc

 

[WizardG]

Sam (hallowed be his name) says NO.

Sam's Laser FAQ - Helium-Neon Lasers

 

[kecked]

Also getting your hands on the isotope mix at todays prices for helium3 would be really expensive. Even neon 22 is sky high. If you want you could put a 633 diode on one end and fake it. Conversion isn’t happening. The gain in hene is really low.

 

[vk2fro]

You won't get anywhere near 10W out of a 80W CO2 tube. It may produce 80W when filled with CO2 mix, but when filled with HeNe mix you'll get milliwatts, mabye 10's at most. This is assuming the fill is the correct mix, correct pressure, mirrors aligned perfectly, correct mirrors of course, correct power supply and ballast resistor and the moon is in the correct phase and the right number of birds are chirping in the back yard when you turn it on

CO2 is orders of magnitudes more effecient than HeNe, thats why you can get 80W out of a relatively short tube.

 

[LSRFAQ]

Depopulation of the lasing state is by bore wall collisions. The larger the bore, the less collisions. Beyond 1.5 mm, forget it.
The world record HENE has a very wide, parallel wall, rectangular bore. 350 mW for a one meter tube, 750 for two in a Vee.
Beam shape is a badly botched nose job, and divergence is horrible, M^2 parameter is like 4 or 6.

If you want to learn, find a copy of Dr. Silfvast's "Laser Fundamentals" It will take you through the design of a HENE with ninth grade math.

Steve "I repump them" Roberts.

PS: Lecture Bottle of Neon 20, = 450$ Lecture Bottle of required HE Isotope = 2000$ last year when I bought them. Lecture Bottle of He Isotope contains a whopping 5 Liters of gas if allowed to expand to Atmospheric Pressure. Todays prices, easily double or triple, if you can find it. The main gas isotope separation plants are in Ukraine these days.

 

[Eidetical]

"Beyond 1.5 mm, forget it." The RF excited He-Ne lasers of the early '60s had bore diameters larger than 1.5mm. That's where all those spatial mode pictures in early books about lasers came from.

 

[Why_you]

Yes, sure you can use larger bore diameters but thats just ineffcient as hell.

The RF excited lasers that you mentioned had large bores, not because they wanted that, but because manufacturing a perfectly straight meter long capillary was practically impossible for them. So it was a simple case of "throw enough sh*t at the wall and some of it will stick":
You use a crapton of RF to get an incredibly lousy output. Something like 1 mW for that construction, and if you break it down to "volume of bore/active part vs output" it gets worse by orders of magnitude.

Also, he explicitly mentioned modern proof of concept (more like "we still had some grant money") HeNe with rectangular bores: I have one of those papers open atm, they used a 18x3 mm2 bore with a 1 m discharge length to get a whopping 85 mW. Compare that volume to that of a SP-125 that can supposedly reach 160 mW and you realise pretty quickly that it's a case of "just because you technically could doesn't mean you should". Ghastly efficiency, laughable tube lifetime and a beam profile that could be a Jackson Pollock painting.

The only way i'd ever see a CO2 laser filled with a HeNe mix produce anything above 1 mW is with RF excitation and a flow design (which will be ungodly expensive)

 

[Eidetical]

"Something like 1 mW for that construction". More like 20mW, but you mention lots of good reasons they went to smaller bores like Steve says really fast. Yet those large-bore RF-excited He-Ne lasers were good enough to make the first holograms!