Why HeNe?

Cyparagon · Nov 3, 2016

Here's one of my 1mW GreeNes

Benm · Nov 4, 2016

Enlarged like that it looks all over the place indeed. I wonder what the beam actually looks like to the naked eye though. It might not even be noticable at first glance since the failure is fairly elegant, not 'splitting in half' like TEM01 on diode lasers.

ultimatekaiser · Nov 4, 2016

That's because of what's causing the modes. It's not multimode like a DPSS laser because of the lack of internal surfaces. The mode hopping in this case is generally from distance. The bore is typically widened and the distancing between mirrors is lengthened relative to their curvatures in these lasers, causing the beam to not be aperture limited. So it maintains a circular shape, causing a symmetrical multi-reflection instead. It's easily observed and played with when you have an external mirror tube.

Benm · Nov 5, 2016

Aperture limiting certainly helps when it comes to output beam looks.

I think i've played with an external-mirror HeNe only once, and on that the adjustment seemed to be 'on or off', where getting it to lase at all was finicky enough.

I supposed that was far beyond the days of the HeNe lasers though as a diode powered pointer was used to get the course adjustment right

ultimatekaiser · Nov 5, 2016

haha yeah you can use another laser as a guide, or if you're really good you can do it without. there's a few tricks that can be done to do it manually if you're clever

Benm · Nov 6, 2016

I'm sure there are, i was just surprised how difficult aligning those external mirrors actually was. The again this was just playing with the thing and a big 'whoohoo' moment when you tuned the mirrors just so a laser beam came out

ultimatekaiser · Nov 6, 2016

Yes the mounts are very very very sturdy and precise. Usually 80 to 100 something threads per inch... And something like a quarter of a turn is the entire range of lasing! If you just randomly fumbled around for a beam your chances of finding it without knowing what you're doing would be probably greater trying to win the lottery!

n2stuff · Dec 27, 2016

Here's my green He-Ne pointer mode hopping.....

Benm · Dec 27, 2016

That almost seems to be giving a class on exotic atomic shell desnsities in the process

Then again, getting the green line to lase on a HeNe is much more difficult that getting the 'default' 633 nm line.

I'm not sure they even sell those kits anymore with the populatiry of laser diodes, but somehow i'd like to have one of them just to see if can still make it work, despite the rather low ouput power (1 mW for the win on that).

n2stuff · Dec 27, 2016

Benm said:
That almost seems to be giving a class on exotic atomic shell desnsities in the process

Then again, getting the green line to lase on a HeNe is much more difficult that getting the 'default' 633 nm line.

I'm not sure they even sell those kits anymore with the populatiry of laser diodes, but somehow i'd like to have one of them just to see if can still make it work, despite the rather low ouput power (1 mW for the win on that).

Ther wasn't a diode when Metrologic build the pointer. I bought their "Build a Laser kit" back in 88' a red 1/2Mw and still have it today. The green laser pointer was around 800-900 bucks at the time I bought my kit. I can posts some pictures later if you want.

ultimatekaiser · Dec 30, 2016

n2stuff said:
Ther wasn't a diode when Metrologic build the pointer. I bought their "Build a Laser kit" back in 88' a red 1/2Mw and still have it today. The green laser pointer was around 800-900 bucks at the time I bought my kit. I can posts some pictures later if you want.

yup. DPSS has come along way. I have one of the first major lab lasers that was a simple green back in the early 90s. did 150mW when new, and was $xx,xxx.xx dollars back then, and is huge. now you can buy the same thing for a few grand if that, and is far more stable and simple, and fits in the palm of your hand. It's quite impressive.

I think I remember seeing HeNe kits a long time ago, they were quite interesting, though of course, the tube is already made, as it takes huge effort to make one. even a small one is hundreds of dollars even today. let alone back in the 70s and 80s in their prime.

QiQi · Dec 27, 2017

n2stuff said:
Ther wasn't a diode when Metrologic build the pointer. I bought their "Build a Laser kit" back in 88' a red 1/2Mw and still have it today. The green laser pointer was around 800-900 bucks at the time I bought my kit. I can posts some pictures later if you want.

wow 1988
that is ancient
i did not know people were already buying lasers back then :wtf:

n2stuff · Dec 27, 2017

QiQi said:
wow 1988
that is ancient
i did not know people were already buying lasers back then :wtf:

Gass lasers have been around since the early 60's when they were invented. Kids today. LOL

diachi · Dec 28, 2017

n2stuff said:
Gass lasers have been around since the early 60's when they were invented. Kids today. LOL

:crackup:

I've got a HeNe that was built in 1983! Still works too. Probably the oldest laser I've had so far.

Some folk have lasers dating all the way back to the 60s in their collections. One guy has a vintage laser "museum" of sorts.

ultimatekaiser · Dec 29, 2017

lol yeah. my oldest one is from '68 I think if I remember correctly. It's incredibly old-so old in fact it has a filament in it instead of a cold cathode.

diachi · Dec 29, 2017

The guy with the laser museum (Bob Hess) contacted me earlier to share a link to his website which contains pictures of the collection. He said that he recently added laser number 400 to the collection.

I had seen the site before but it was invite only at the time, didn't know that it had been made publicly available.

https://sites.google.com/site/vintagelaserarchive/

Why HeNe?

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