mcdanlj
August 23, 2020, 10:14pm
2
The most likely thing is that the tube has shifted into TEM01. This means that the tube is dead. Which chiller do you have? Have you always kept the tube temperature within limits ? If so, I’d say go back to Orion and let them know that the tube died a premature death despite proper care.
Just yesterday we had this post in which two people report a similar problem with new tubes.
This looks to me like the tube is operating in TEM01 — that can look like two dots or like a circle. You can search this site for TEM01 to get more pictures to compare, if you like.
If the tube was delivered like that, I hope the seller will replace it. The cheapest lasers arriving with tubes that run in TEM01 has been reported to be a problem in the past. The fix is only to replace the tube, sadly. …
Looks to me like the tube is on its way out.
This is typical of a tube that has shifted to a higher-order transverse mode . TEM01 is the most common mode to shift to; it’s sometimes called the “donut mode” and in theory is donut-shaped but in practice seems commonly to look like the two dots you see here. [Edit: TEM₀₁* (donut) is different from TEM₀₁, which looks like two dots.]
Poor cooling control can lead to this happening earlier, but as far as I can tell it’s a common failure mode for even…