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The green HeNe I won from eBay has a unique cylindrical TEM[sub]10[/sub] mode:

It is rated at .5mW and I measured a phenomenally stable 1.3mW after warm up. The divergence is terrible... somewhere between 2.5 and 3.5mRad. A disassembly attempt ended in frustration as the tube is embedded in the covering and the case is used for grounding. Any attempt to extract the tube might result in cracking it :-/. But for those of you that haven't seen a green HeNe tube lasing, it has the identicle distinctive orange/red glow of a regular tube... but with a green beam.
My large argon has a strange set of optics that wastes ~3% of just the green output out of the back which I used for another green source. So here are (from left to right) HeNe (543nm), Argon (514.9nm), and DPSS (532nm). I think the only one I'm missing is copper vapor
The color difference is not as apparent here, but the HeNe has a veritably yellower hue to it. 543 is to 532 as 635 is to 660.


And just DPSS with HeNe:


It is rated at .5mW and I measured a phenomenally stable 1.3mW after warm up. The divergence is terrible... somewhere between 2.5 and 3.5mRad. A disassembly attempt ended in frustration as the tube is embedded in the covering and the case is used for grounding. Any attempt to extract the tube might result in cracking it :-/. But for those of you that haven't seen a green HeNe tube lasing, it has the identicle distinctive orange/red glow of a regular tube... but with a green beam.
My large argon has a strange set of optics that wastes ~3% of just the green output out of the back which I used for another green source. So here are (from left to right) HeNe (543nm), Argon (514.9nm), and DPSS (532nm). I think the only one I'm missing is copper vapor

The color difference is not as apparent here, but the HeNe has a veritably yellower hue to it. 543 is to 532 as 635 is to 660.


And just DPSS with HeNe:
