Why HeNe?

What's the advantage of HeNe lasers these days? Is there anything they can do that diodes can't do better? Or is it just a matter of it being a cool tech? HeNe tubes definitely scream "laser" to me, much more than diodes.

HeNes are superior to laser diodes in just about every way imaginable from a science standpoint (or were it's debatable now as of 2020). But their output power is quite low due to it being a gas (Neon) rather than a solid. They're still very cheap for a lab quality laser, averaging nowadays about a grand or two new for a typical one, compared to a stabilized laser diode which is anywhere from 5-10K and has a potentially worse beam profile/shape. HeNes are also bigger of course too, but they look darn cool. I've worked on one of the largest ones ever put into mass production which was over 2 meters long and weighs over 100 pounds!

In the days of yesteryear before diodes, they were the gold standard for a good quality, long life, basic laser; and were quite inexpensive in their prime, hitting as low as a few hundred dollars a tube at one point. Now they're mostly educational tools I tend to find. The only major thing I still find them used for is for stabilized wavelength laser references in wavemeters and certain equipment, but that's in pretty small numbers. The Iodine stabilized HeNe is actually a standard for defining wavelength, length, and a bunch of other things- It's used as a reference in a lot of important calculations.

For a hobby person, they're the quintessential laser. Great for understanding how a laser works, and good for some more science-y stuff like holograms and such. Cheap ones can be had off surplus for pretty cheap depending on the size you want. usually less than a few hundred dollars. small ones are often under 100, and somewhat more rarely, even as low as 20 some bucks a tube. mostly depends on what you want it for. Power supplies are another matter however, and are growing ever more expensive, due to being in far lower demand and harder to find, and can be anywhere from 50 to several hundred bucks depending on quality and how nice it is etc. I'd say if you look around you could get one for probably less than 100 bucks, maybe less than 200 for a really really nice small one. one time someone scored one on ebay with a supply for 20 bucks. just gotta keep your eye out.

bluestars said:

What's the advantage of HeNe lasers these days? Is there anything they can do that diodes can't do better? Or is it just a matter of it being a cool tech? HeNe tubes definitely scream "laser" to me, much more than diodes.

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my helium Neon at 612 is quite bright 2mw orange and it has such a small dot and i tested it by shining 50 feet at night and it still had better divergance than my cni 561. mine has a perfect round dot. They look amazing.

Thanks for the answers folks! I remember some experiment in my undergrad physics class used a red HeNe laser. They said something similar at the time, but I wasn't sure if diode tech had passed HeNe by yet. Of course, there will always be niches where solid state cannot quite compete.

This is a bit like answering my own question, but I've been reading Sam's FAQ and found this section:

Since a 5 mW laser pointer complete with batteries can conveniently fit on a keychain and generate the same beam power as an AC line operated HeNe laser almost half a meter long, why bother with a HeNe laser at all? There are several reasons:

For many applications including holography and interferometry, the high quality stable beam of a HeNe laser is unmatched (at least at reasonable cost, perhaps at all) by laser diodes (though this is apparently changing at least for some diode lasers. See the section: Holography Using Cheap Diode Lasers. In particular, the coherence length and monochromicity of even a cheap HeNe laser are excellent and the beam profile is circular and nearly ideal Gaussian TEM00 so that simple spherical optics can be used for beam manipulation. Bare edge emitting laser diodes (the only visible type currently available) on the other hand always produce a wedge shaped beam and have some amount of astigmatism. Correcting this to the equivalent quality of a HeNe laser is difficult and expensive.

As noted in the chapter: Diode Lasers, it is all too easy to ruin them in the blink of an eye (actually, the time it takes light to travel a few feet). It would not take very long to get frustrated burning out $50 diodes. So, the HeNe laser tube may be a better way to get started. They are harder to damage through carelessness or design errors. Just don't get the polarity reversed or exceed the tube's rated current for too long - or drop them on the floor! And, take care around the high voltage!

Laser diode modules at a wavelength of 635 nm (close to the 632.8 nm wavelength of red HeNe lasers) may still be somewhat more expensive than surplus HeNe tubes with power supplies. However, with the increasing popularity of DVD players and DVDROM drives, this situation probably won't last long.

However, the market for new HeNe lasers is still in the 100,000 or more units per year. What can you say? If you need a stable, round, astigmatism-free, long lived, visible 1 to 10 mW beam for under $500 (new, remember!), the HeNe laser is still the only choice.

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Yeah that's generally still gist of it. I think that was written a number of years ago but it still holds somewhat true. Helium neon lasers just offer a lot of bang for their buck. In fact they're one of the oldest surviving lasers still in service today, and the main reason for that is just not there so versatile vs their cost. Diodes have definitely in recent years supplanted them quite a lot in common tasks, and production of henes is starting to stagnate a lot as DPSS and OPSL technology grows ever cheaper and more advanced. Lasers are a huge, huge market now that is all their own-and grown to be a large aspect of the things that drive modern life. I actually have some of the oldest surviving helium neon laser models around, dating back to the 60s.

ultimatekaiser said:

In fact they're one of the oldest surviving lasers still in service today

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Wouldn't HeNes actually be the oldest surviving laser technology since ruby lasers fell out of service a number of years ago?

I'm not positive, but it could well be true. They are definitely the oldest gas laser technology, as well as the first fully CW laser. The first HeNe was developed at Bell labs in late 1960, and was IR at the 1153 line, then quickly red was discovered shortly thereafter. I think one of its creators died recently. (September I think)

Ruby is indeed the oldest, demonstrated in 1960 and is still used today, but not really in any major quantity. They fell out of production a few years ago. They're still great for large holograms and stress analysis, as well as for tattoo removal and sometimes UV generation. But they are pretty inefficient overall on large-scale, so they're definitely not very popular anymore...which is a shame.

bluestars said:

What's the advantage of HeNe lasers these days? Is there anything they can do that diodes can't do better? Or is it just a matter of it being a cool tech? HeNe tubes definitely scream "laser" to me, much more than diodes.

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HeNe tubes where THE laser for ages - afforable, reliable, continous output.

And they certainly do some things diode lasers usually do not, such as producing a very reliable and reproducible output wavelength. The output pattern is also near perfectly gaussian which is important for some applications.

The downside is that they are enourmous in size for a given output power. Tubes about a foot long produce something in the order of 1 mW of laser light output. If you wanted something like 100 mW output power you'd end up with a tube you could not lift without equipment. The power requirement would probably be problematic if you only have domestic mains available too.

Speaking to HeNe costs, I actually got a complete Gammex green HeNe for $45 a few weeks ago. I think there's a complete red Gammex HeNe on eBay right now at a similar price, all you have to do is rip out the unnecessary optical array.

Sta said:

Speaking to HeNe costs, I actually got a complete Gammex green HeNe for $45 a few weeks ago. I think there's a complete red Gammex HeNe on eBay right now at a similar price, all you have to do is rip out the unnecessary optical array.

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I bought it. This hobby...

Benm said:

The output pattern is also near perfectly gaussian which is important for some applications.

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FYI, doesn't apply to all of them. Some are multimode.

Power output (and mode) is the result of a lot of different things.

diachi said:

FYI, doesn't apply to all of them. Some are multimode.

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Is this actually common?

I've never seen a multimode one, but they again i've only seen low power ones (1 mW or so) which all seem to have good beam specs. If there is anything to identify multimode ones before purchase it would be nice to know.

Benm said:

Is this actually common?

I've never seen a multimode one, but they again i've only seen low power ones (1 mW or so) which all seem to have good beam specs. If there is anything to identify multimode ones before purchase it would be nice to know.

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My 594 (HeNe ofc) looks kinda TM33 when spread out, and it's probably <3mw at best. I'd post a photo, but the pattern gets washed out.

Benm said:

Is this actually common?

I've never seen a multimode one, but they again i've only seen low power ones (1 mW or so) which all seem to have good beam specs. If there is anything to identify multimode ones before purchase it would be nice to know.

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You probably won't be able to tell from the beam right out of the aperture, but if you expand it you'll see it isn't a Gaussian beam. Still going to be a reasonable quality beam when compared to diode.

Best example I could find - there were some threads before but the pictures have all disappeared. https://mi-lasers.com/wp-content/uploads/multimodeOUTPUT.jpg

As for identifying them? Find the model number, dig up a spec sheet. That's the only way I can think to check.

Benm said:

Is this actually common?

I've never seen a multimode one, but they again i've only seen low power ones (1 mW or so) which all seem to have good beam specs. If there is anything to identify multimode ones before purchase it would be nice to know.

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Heres a video I took of a hene Mode hopping.