Ion Laser Question

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JohnFP

Ion Laser Question

Post by JohnFP »

This is really strange. Last week I was using my 514 line. I tuned it for max power (mirrors) and did not touct the already tuned etalon for 488. Interferometer was great. Then a couple of days ago I decided to go back to 488. I left the etalon alone and peaked for 488 and I got a non Tem00 mode at peak power (thumbscrew tuning not power dial on power supply). The beam had a black spot in the center of it. When I detuned on of the mirrors slightly the black spot went away. Fringes were great with the black spot and without.

Anyone see this before or know why it happened? I have never seen this before in tuning the mirrors for max power.
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