Power in 514, 488 without etalon and etalon tuning

[JohnFP]

Ok, I just did some tests and this is what I found.

THis is on a SPectra Physics 165 Argon Ion Laser.

At 20 amps without etalon
514 output was 40mW
488 output was 320mW

At 25 amps without etalon
514 output was 280mW
488 output was 520mW

At 30 amps without etalon
514 output was 400mW
488 output was 660mW

When I tried to go above 32 - 33 amps the meter did not register any additional output power for the 514 line and only a small increase for the 488 line. I am using the internal meter built into the power supply with the detector being built into the head. This meter may be faulty at higher powers. I was using the 1 watt setting on the meter and now that I think about it I should have checked the 5 watt setting just for ha ha's.

When I put in the etalon the output was exactly the same at flash point for the 488 line but what was weird is that if I kept the etalon the same then tuned the laser to 514 I could see both lines, the 514 and the 488 by eye and a nice separation with my handy dandy diffraction "cool" glasses. When I detuned the etalon to get just the 514 line I could not reach the power or find a flash point as I did with the 488 line. Not sure if I did not try hard enough or if the etalon is tuned (the air space between the windows) is specifically for the 488 line.

So at 30 amps the laser still did not output more power at the 514 line then at the 488 line. But I do have a hypothesis. If the person using the laser before me used the 514 line all the time and at high power it may be possible the the back prism/mirror assembly has a burn in spot precisely at that tuning. Thus when you move to another line the prism refracts the 488 line to a differnt place on the mirror that is not burnt in thus more power. I shure would like to get some data with a new back and front mirror and prism. What was proposed before about the 514 having higher gain at the higher amperage may still be correct but I cannot tell.

Right now the power I am getting out of the 488 line is very addequate and I do not need the 514 line yet but it may be soon that I need to get my mirror recoated. I will have to do more testing.

After I got maximum power without the etalon in the 488 I put the etalon in and peaked it to the flash point. This gave same power as without the etalon. I then introduced the Michaelson Interferometer I built on a rail with a path difference of about 4 feet and tuned the etalon to the most contrasty fringes. It was off the flash point by about 40% to the next bright output. The fringes locked right in and were a stable as could be. I even bumped the table and blew on the laser and they did not budge so I am confident this is the way to tune an etalon.

WIth the etalon in and running at 22 amps I am getting about 210mW. This is where I will stay until more is needed.

Peace to all!