User:Andy Maloney/Notebook/Lab Notebook of Andy Maloney/2009/07/03/1064 laser tweezers

Alignment

Yesterday Anthony and I were working on the 1064 laser tweezers. I had to leave the room for a bit and unfortunately Ant moved some knobs that brought the laser beam out of alignment. It's okay as realignment is trivial and doesn't take that long to do.

I would like to point out that putting a laser beam through a microscope is a bit trickier than just sending it straight down a path on an optical table. However, it is still trivial to do so. The goal is to send the beam in a straight line through the microscope. There are lots of people that are rather fervent about the procedure of doing this and they think that their way is the best/only way to do it. I'm sorry but not only do I not give a rat's ass about your method, neither should anyone care about how I did it. A straight line is defined by two points. I don't care one iota if those two points are your finger tip and you anus. It doesn't matter!

Enough ranting. Here's what I did so I don't forget because I think it is quite clever.

• Mounted an iris on the cage system from Thorlabs that is mounted under the sample stage (add picture).
• I then used my condenser adapter to mount another iris on the rack and pinon mounted on the Olympus condenser arm.
• Next, I used the camera on my phone to visualize the infrared beam on the cage iris. I moved the bottom mirror on the periscope to align the beam through the iris. Thank goodness I have a cheap camera on my phone.
• I then used my camera to look at the beam on the iris connected to the condenser arm. Initial attempts to look at the beam required me to open the iris on the cage system but after several iterations of moving the mirrors, I was able to keep the cage iris almost completely closed. I say almost completely closed because it's best to keep the iris size just a little bit under the size of the laser beam. That way you can see where the laser is with respect to the open iris. I moved the top mirror for alignment to the condenser iris.
• Once I was satisfied with the alignment between the two irises, I then proceeded to repeat my above steps except this time I moved the iris on the condenser arm up and down. After a few iterations of moving the periscope mirrors, the beam follows the center of the iris all the way up the condenser arm.

Remember now, no one should care about what I used to define the beam path. All that matters is that I was able to measure from 2 stable points thus defining my laser path. I liked my method and I'll have to remember how to do it because it only took me 30 minutes to do it.

I wonder if there are small SM1 threaded cheap cameras one can mount onto my condenser adapter. I'll have to look into this.

Trapping

Well, after fussing with the beam and ensuring that it was straight, I went ahead and tried to tweeze with it without any steering optics. Koch and I did it and the beam tweezed very well. We were able to get very large clumps of beads.

To do

• Determine the size of the beam before the steering optics.
• Make a Sketchup of the system.
• Put in the steering optics.
• Calibrate...maybe. I'd really like to have Ant around for calibration and the DNA stuff so I may want to wait.
• Post a movie of the tweezers.
• Learn how to use Larry's awesome LabVIEW program entitled "2 and 1/4 attempt at a super kick ass camera application that is superior to anything on this planet...and...your mother sucks.vi". Or whatever he called it.