User:Pranav Rathi/Notebook/OT/2010/09/29/CrystaLaser Vs CompassLaser

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Our new laser looks completely different (Is it good or bad I do not know) in the old objective, and it’s been puzzling us for the last one week. So to search the answer of this question we replaced our beam expender lens system with old telescope; nothing changed. Next I removed the AOM and nothing changed. So the last thing left was the laser itself. So today I captured two movies: In first one we have crystalaser-telescope-old objective (mirrors in the middle) and in second we have compasslaser-telescope-old objective (mirrors in the middle). The difference is obvious; the trap with the new laser (1.9W) looks completely different. I just only see one bright spot at the center, as I go in and out of focus multiple reflections can be seen with diffraction pattern along x-axis of the video frame. I used the lower surface for the video. The trap with the old laser (1 W) looks as usual, 4 lobes can be seen clearly. I used somewhat the same beam expansion with 6-7mm beam diameter at the objective. Why the trap looks different (is it because of mode profile)? Which one is better (it looks like we were trapping the beads lot better with the new laser)? Is it possible that our old laser is multimode even at the low powers and because of that we see four lobes?

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