My DIY orange laser

Here I'd like to share my experience of building a real orange laser! this is a pulsed laser, that uses pure neon as a lasing medium. As far as we know, pure neon can lase only at one IR line in CW mode, mixing it with helium is needed to get visible output. Red he-ne lasers are the most widespread, he-ne of other colours are much more rare, their gain and output power are low. But everything changes when you apply high voltage very short pulses to the tube with pure neon. It begins to lase at various wavelengthes including red (626 nm), orange (614, 594 nm) and green (540 nm)!! Moreover, lasing is superradiant without any mirrors, because gain is extremely high! On the other hand, output pulses are very short (approximately 1 ns), pulse energy is quite low too. Anyway, the simplicity of the laser motivated me to try to make one. I had a broken LE Nitrogen laser tube and brought it to the local neon sign shop. I asked the glassblower to fill it with pure neon at the pressure of 1 Torr or somewhat lower. The appendix on the tube is the getter, to burn the crud out from the gas. Then I installed this rebuilt tube into the nitrogen laser frame, removed the mirrors and attached it to the nitrogen laser supply. And it works! The lasing line is 614 nm, as it is the strongest one according to russian literature. When I split the beam with the diffraction grating I didn't find any other lines. Lasing is superrardiant, adding mirrors doesn't affect performance. The high voltage pulse should be shorter, on the PSU with "fresher" thyratron lasing was more stable and brighter.

Here is the video from youtube: https://youtu.be/42HIzaLnx40

According to the same literature it is worth trying to fill with neon old long (at least 1 meter) He-Ne tube as it can give good lasing at green 540 nm line. Only after building this unit I found Mark Csele's article about building a neon laser from small he-ne tube.

And here are some photos of my setup.

Very nice, I left a message for your at the youtube link: https://youtu.be/42HIzaLnx40 - can you respond to me there? Thanks!

Neat, I've always wanted to do this! I don't have anyone around me that I know of that has an appropriate vacuum for it though.

Awesome! Thanks for coming back with more! Cool looking tube.

very interesting indeed, great job Mr. Scientist :beer:

Thanks for sharing. You are undoubtedly several cuts above your regular "I'm 'building' a laser... by soldering a pre-made circuit to a diode"

That sounds like it would be hard on the electrodes. Would you expect more than a few hours of continuous operation, or is this just for fun? Is the idea for the sputtering to be contained in that remote (blackened) tube?

Are you rounding off the colors, or is the green for example actually ~3nm difference from the standard 543nm HeNe? Have you seen the other colors in this project, or are they theoretical from the literature?

That sounds like it would be hard on the electrodes. Would you expect more than a few hours of continuous operation, or is this just for fun? Is the idea for the sputtering to be contained in that remote (blackened) tube?

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At the moment it is just for fun. This tube is only for "proof of concept" and is not for regular operation. Output power is very low (possibly 0.05 mW average) and I'm not sure it can have any applications. Any coaxial nitrogen or he-ne tube is not optimal for proper work as a neon laser, because major part of the gas discharge goes past the bore and glows inefficiently without lasing. I am going to try a straight tube with hollow cathode, it should work better. The getter tube with some metal sputtered on its walls should help this unit work for some time. In case of tube contamination I can reactivate the getter and make neon pure again.

Are you rounding off the colors, or is the green for example actually ~3nm difference from the standard 543nm HeNe?

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No. Neon atom in pulsed mode has somewhat other lasing transitions than in CW mode. Some of them may match together, I don't have reliable source of information on ALL possible CW helium-neon lines except well-known 543 nm, 632.8 nm, 1.15 um and 3.39 um. In pulsed mode lasing was reported on the following lines: 626.6 nm, 614.3 nm, 594.5 nm and 540.0 nm in visible and on a bunch of IR lines. The output wavelength and its power strongly depends on tube geometry (length, diameter), type of the cathode (cold hollow one or hot, like in argon ion tubes), neon pressure (it varies between 0.1 and 1 Torr for visible lines and between 2 and 5 Torr for IR lines, optimal pressure also depends on the size of the tube). First three lines can lase simultaneously in short and narrow tubes, but both 626 and 594 nm lines are usually so weak that can be detected only by a good spectrophotometer with a photomultiplier. The 614 nm line is dominant and can be seen visually. The 540 nm line appears in bigger tubes (for example 120 cm long and with 5 mm inner diameter) but other lines don't lase according to my russian book about pulsed gas lasers.

Have you seen the other colors in this project, or are they theoretical from the literature?

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No, I didn't see them, I saw only 614 nm in my experiment with this tube. Its bore size is 3 mm inner diameter and 30 cm length.

In my next experiment I'll ask the glassblower to make a bigger tube with a hollow cold cathode, I hope that will give me some green light.

I am curious if you work with lasers or electronics as a technician, or perhaps are an engineer? I am very impressed.

This is just my hobby, I spend 146% of my free time on it and sometimes repair lasers for my University, where I used to study. I have already changed a couple of jobs and now I'm studying CNC lathe machining. Also I used to work as an electric motor refurbisher.

When I come to Odessa later this year I would like the opportunity to meet, if you are interested.

Any time -- welcome. Just inform please in advance about your visit.

OK, I don't know when yet myself, but it won't be any time soon, hopefully this summer or fall. Need to come to start work on finishing the interior of my new apartment there, you might recognize this building:

http://i853.photobucket.com/albums/ab95/LaserProject/Screen Shot 2016-12-26 at 8.09.30 PM.png

Laserbuilder said:

This is just my hobby, I spend 146% of my free time on it and sometimes repair lasers for my University, where I used to study. I have already changed a couple of jobs and now I'm studying CNC lathe machining. Also I used to work as an electric motor refurbisher.

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So would you be able to CNC something from autodesk inventor for me? Just wondering because if you start making hosts you could make some really beautiful ones and make some money too

I am only getting started with it and my skill is quite poor yet. But in a couple of months I think it will be much easier for me.

Laserbuilder said:

I am only getting started with it and my skill is quite poor yet. But in a couple of months I think it will be much easier for me.

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I know there is a high demand here on LPF for really beautiful and functional hosts. I know that eagamus guy (i hope i spelled that right) and jrob have made quite some good extra cash by selling hosts and assemblies they've made/modified for lasers. I think they have all the necessary equipment though like metal lathes and precision metal working tools.

Very good Laserbuilder. I can see that you are going to be a member that everyone looks forward to you posting new stuff. :beer: