Help with ruby laser mirrors

[Laser-meow]

I know that's probably not the right section or forum but I desperately need help to understand what's wrong with my ruby laser mirrors. I bought them on ebay several years ago when I tried to build my first ruby laser, which never worked. I don't know if the problem is with mirrors. The HR looks good, while the OC, when light passes throught it, produces two output beams, like the two faces of the mirror are not parallels. In years I couldn't figure out if this is normal or maybe a construction defect. I hope someone can help me!

In the first photo you can see the normal HR mirror, the second one is the "strange" OC with double image.

 

[RedCowboy]

It's just a guess but it looks like that multiple image is caused by the AR coating, maybe it's coated inside and out and you're getting reflections between the inside and outside.

 

[paul1598419]

One of the most difficult things to find are mirrors to match a Cr doped Sapphire crystal cut to a rod for use in a ruby laser. One must also make the length the mirrors are separated an exact integer number of the 694.3nm output of this laser. I don't have an immediate explanation of why you are getting two beams, but it is likely you aren't operating in TEM00 mode.

 

[Cyparagon]

Credit goes to Eidetic (from the infamous laser discord) for supplying the following:

It's typical for them to be wedged like that, to prevent lasing off the second surface.

 

[Laser-meow]

Thanks guys, I'm so happy that this maybe normal, thus probably it never lased for poor design of pulse forming network and lamps arrangement, I'll try again in the future!