User:Andy Maloney/Notebook/Lab Notebook of Andy Maloney/2009/07/01/1064 optical tweezers

Periscope
It was nice to figure out what a periscope is and how it works. Unfortunately when I tried to apply it to the infrared laser, I just couldn't get it to work. I spent late nights trying to get the thing to work and I just kept screwing it up. I finally decided to get the periscope I built aligned with the HeNe laser and then transfer it to the infrared laser.

I found that you don't have to have the beam directly in the center of the mirrors to get it to work, contrary to what I was told. Also, you align the periscope in the same manner you would any mirror arrangement. Moving the mirrors with respect to each other (up and down) steers the beam up/down or left/right.

I have noticed that the mirror mounts we have, drift. We may want to get some locking mirror mounts. Also, the rotation stage I am using is not necessary. I just realized this and I will remove it since it has been a constant source of irritation because it is not all that stable.

Through the microscope
After getting the periscope aligned, the next stage was to send it through the microscope such that it went straight up. I put the 1064 nm dichroic mirror in the spot that Olympus makes thus making my ability to steer the beam and fine tune the mirror's position impossible. Such is life.

I used an RMS to SM1 adapter that Thorlabs sells (we should get one) and a frosted glass 1064 nm mirror to get the laser beam centered somewhat. Since two points make a straight line, I also used a set of irises. One in the spot where the mirror was and another directly above it where the condenser is housed. I just fussed with the periscope till the beam went through both. After writing this, I think I should do a better job of aligning it since I have the capability to do so. At any rate, it works.

Steering optics
I've decided to mount the steering optics to the underside of the threaded breadboard we got from Thorlabs. This seems reasonable to me but not to others. I've been told that it will act as an antenna for motion and ultimately cause measurements to be imprecise. I'm still not convinced of this so I will continue forward with my design.