User:Linh N Le/Notebook/2009/06/25: Difference between revisions
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***[[User:Steven J. Koch|Steve Koch]] 23:12, 25 June 2009 (EDT): Good point -- I thought I knew, but did some poking around and realized I know even less about lasers than I thought. I had been told previously that the beam waist is usually at the output coupling mirror, but now I'm not sure. See: [http://en.wikipedia.org/wiki/Optical_cavity optical cavity configurations]. Then this picture confused me: [http://an.hitchcock.org/repairfaq/sam/rayleigh.gif beam diagram]. In any case, I think the practical answer is that once we beam expand, the imaged (virtual) beam waist is very far back in space -- many meters, I'd guess ... and thus it doesn't matter much. | ***[[User:Steven J. Koch|Steve Koch]] 23:12, 25 June 2009 (EDT): Good point -- I thought I knew, but did some poking around and realized I know even less about lasers than I thought. I had been told previously that the beam waist is usually at the output coupling mirror, but now I'm not sure. See: [http://en.wikipedia.org/wiki/Optical_cavity optical cavity configurations]. Then this picture confused me: [http://an.hitchcock.org/repairfaq/sam/rayleigh.gif beam diagram]. In any case, I think the practical answer is that once we beam expand, the imaged (virtual) beam waist is very far back in space -- many meters, I'd guess ... and thus it doesn't matter much. | ||
**** [[User:Andy Maloney|Andy Maloney]] 00:00, 26 June 2009 (EDT): I agree with Koch about not really caring about the waist directly from the laser. However, if you really want to do it then I'd suggest kicking it 80's razor blade style. This is where you put a razor blade some distance from the laser and move it across the beam. At 86% and 33% of the total power of the beam, you have your 1/e<sup>2</sup> values thus giving you the beam diameter. Do it again farther downstream and you can calculate the beam divergence. | **** [[User:Andy Maloney|Andy Maloney]] 00:00, 26 June 2009 (EDT): I agree with Koch about not really caring about the waist directly from the laser. However, if you really want to do it then I'd suggest kicking it 80's razor blade style. This is where you put a razor blade some distance from the laser and move it across the beam. At 86% and 33% of the total power of the beam, you have your 1/e<sup>2</sup> values thus giving you the beam diameter. Do it again farther downstream and you can calculate the beam divergence. | ||
**** [[User:Steven J. Koch|Steve Koch]] 00:28, 26 June 2009 (EDT): Yeah that's a good idea. Linh was really good at the beam chopper, which is similar. We probably picked the wrong thing to try first, though I was interested in the 2-D picture. It'd be worth doing either of these things, except that I think days count a lot now. You agree? | |||
Revision as of 21:28, 25 June 2009
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To Do
11-6 Laser + new lab
Laser Images
Analysis
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