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Tunable Helium Neon Laser

lasingfox

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hey hey,

I recently picked up a tunable HeNe from a friend and I just wanted to share. Currently, it doesn't lase, and has all sorts of problems, but, I am working on fixing it. I'll updated this if I get any coherent photons out of it :) I'm hoping to get 594nm, 604nm, 612nm and 632.8nm. That's what this laser originally output so ideally, i'd be able to get all of them back. tunabl.jpgtunablbrewst.jpg
 



Encap

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Potential problems include loss of helium as this can permeate the glass, along with air ingress, and failure in the ageing high voltage power supply among others.

Some great imfo on He/Ne lasers and repairing them on Sam's site : http://donklipstein.com/laserchn.htm#chnvchn

Good luck with it.
 

lasingfox

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Potential problems include loss of helium as this can permeate the glass, along with air ingress, and failure in the ageing high voltage power supply among others.

Some great imfo on He/Ne lasers and repairing them on Sam's site : http://donklipstein.com/laserchn.htm#chnvchn

Good luck with it.
the previous owner had the brick let out the magic smoke before he could get it lasing. he replaced the brick and that's about where I am now, haha. i'm planning on giving it a good helium soak along with some other tubes I have laying around and then hopefully get some pretty coherent photons.
 

Anthony P

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Have you tried adjusting the wavelength selector?
 

lasingfox

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Have you tried adjusting the wavelength selector?
yup. I swept through the entire range. I also tried using another hene for alignment but i got nothing out of the tunable. i also cleaned the tuning prism and brewster so there should be no issues there.
 

lasingfox

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I got it more or less aligned! only lases at 632.8 which could be a number of things. I've been running it all day to try and clean up the gas but it's probably also low on helium and im only running it at 4.5mA instead of its suggested 5.25mA. still this is good progress! now i can soak it safely while monitoring the power.tunable copy.jpg
 

ultimatekaiser

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It appears to be missing the dust cover. (Or maybe your model just doesn’t have one) they get dusty pretty easy, And the tiniest bit of dust or scratching can really mess these up. The become misaligned pretty easily too. The color looks good so I’ll be willing to bet that it probably is either very old, dirty, or more likely that the alignment has simply drifted. (Or some combination thereof) if you can’t get it aligned then I can do it for you. :) I actually need to get a replacement tube for mine. Mine is leaky.

Edit: i’d be more than willing to bet that the low current will cost you a bunch of lines. It really needs to be run it about 5.5mA to get everything. I used to service these along time ago. They honestly were never the greatest lasers, but theyre pretty neat and unique.

edit 2: Also don’t try to helium soak this tube. 1. You don’t know for sure that it needs it and it probably doesn’t based on what ive read. 2. It’s very imprecise and these tubes have to be at exactly the right pressure to function right. 3. Helium neon lasers use helium 3 not helium 4, which is what you would end up ordering. He3 is much more efficient, And creating a mix of the two gases would actually probably rob it of power rather than give it more.
 
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lasingfox

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It appears to be missing the dust cover. (Or maybe your model just doesn’t have one) they get dusty pretty easy, And the tiniest bit of dust or scratching can really mess these up. The become misaligned pretty easily too. The color looks good so I’ll be willing to bet that it probably is either very old, dirty, or more likely that the alignment has simply drifted. (Or some combination thereof) if you can’t get it aligned then I can do it for you. :) I actually need to get a replacement tube for mine. Mine is leaky.
oh it has a dust cover. i just removed it so I could rotate the tuning prism without putting stress on the brewster. I cleaned everything and then popped the cover back on. I also got it pretty much aligned and even got a tiny amount of 612nm! I'm waiting on my LPM to arrive and then i'm gonna give it a good helium soak because I'm only getting maybe 200-800uW of 632.8nm (just compared it with other hene's I know the rough power of).

oworange.jpg
 

ultimatekaiser

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I’m actually wondering if you bought Sam‘s old weak tube. he had one up for sale recently that was pretty we and only did red in a tiny bit of orange.
 

lasingfox

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nope, I got this one from a friend. he recently bought another tunable so I traded him an argon ion for it. but the catch was, I had to fix it up. the psu blew up so he had to remove the tube and put a new one (which misaligned everything more). this brick maxes at 4.85mA but, I have a 5.5mA one that should be here sometime next week which I hope isn't dead already.
 

ultimatekaiser

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Yeah I would definitely run it it it’s rated current first. They scale pretty well with current. If it was low pressure it would drop out pretty fast because there wouldn’t be enough buffer gas to keep it going. As the tube warms up it would create a negative resistance and I would basically start to flicker like a relaxation oscillator or just go out entirely as the dropout current climbs. You’re already running it undercurrent current so if it’s not going out I highly doubt pressure is a problem.

helium soaking likely wont help, and any helium you buy would be the wrong isotope anyway. If you need me to put the tube to the test I can actually test it with dedicated mirrors if it comes down to it.
 

lasingfox

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Yeah I would definitely run it it it’s rated current first. They scale pretty well with current. If it was low pressure it would drop out pretty fast because there wouldn’t be enough buffer gas to keep it going. As the tube warms up it would create a negative resistance and I would basically start to flicker like a relaxation oscillator or just go out entirely as the dropout current climbs. You’re already running it undercurrent current so if it’s not going out I highly doubt pressure is a problem.
that would make a lot of sense, haha. I'll keep that in mind. thank you. i've definitely had my fair share of oscillating tubes.. it's the worse noise to hear when you go to fire up a tube that just came in. but, i'll let you know when the brick comes in and how it likes the right current. :)
 

ultimatekaiser

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Absolutely. It’s been along time since I’ve seen someone post in the gas section. I’ve been pretty lonely over here! I just randomly logged in today and saw you’d shown up with a gem. I’m happy to help make sure that it ends up nice and happy.

I should probably email REO about getting a replacement tube for mine.
 

lasingfox

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heh, gas lasers are the best! they are way more interesting and educational than diodes. plus the lower powers and exotic wavelengths make them perfect for viewing in person. i think i only own a couple diodes and an opsl.
 

ultimatekaiser

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also can you give me some sources for this? I've found a bunch of conflicting info on the helium isotope to soak hene's in
No sources needed. I’ve done it. So I’m speaking from experience. I’m basically the HeNe guru of the forum.

and I do agree gas lasers are definitely my favorites for their cool factor and history. I don’t have much in the way of single diode lasers. A few...plenty of dpss ones tho. As for opsl heads I have a stack of sapphire lasers, and a few genesis and obis lasers too. Definitely some of the nicest lasers that you can buy at the moment for many applications.
 




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