User:Andy Maloney/Notebook/Lab Notebook of Andy Maloney/2009/07/08/1064 Optical tweezers

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Dichroic cube

Today I aligned the 690 mirror in the cube attached to the condenser. I did so by taking the cube off and aligning it with a HeNe. Yesterday proved to me that trying to align the mirror with the 1064 laser would be too difficult. Just in case you were wondering, I do get a reflection off of the 690 mirror at 1064 but, there are a lot of ghost images due to reflections. We will need to get a 2 inch diameter 1064 dichroic in the near future.\


Koch said that it is a good idea to get the QPD setup such that the beam hitting it is almost filling the active area. Again this is proving to be much more difficult than I would have thought primarily due to the limited supply of 1064 lenses we have. I guess in the short run, using a non coated lens will do just fine.

One thing I have noticed is that there are a lot of spherical aberrations coming from the lens used to image the laser on the QPD.

  • Koch Question: Do spherical aberrations matter?

Trying to get this thing to work has resulted in my realizing that we need a long pass filter before the lens. Also, I cannot put the lens anywhere in the path of the condenser light otherwise it screws things up. The reason we need a long pass filter is so that the lens does not end up imaging the condenser light.

If we want to setup the QPD such that the laser light almost completely fills the active region, then we are going to need to get a negative lens coated for 1064.

I went ahead and setup the negative lens/positive lens system. The negative lens is coated for the visible and the positive lens is coated for infrared.

The QPD is also setup to start taking data.


I've noticed that the breadboard the translators are on wobbles quite a great deal. I will need to figure out some way of stabilizing this.

Things to get

Koch, let me know which of these things you think are appropriate.

Other thoughts

  • So I think when you wanted a shutter to turn the laser off, it was meant to stop tweezing and not to block the entire beam path at the laser. If that's the case, I would suggest us using the manual shutter I got previously. I can put it in the steering optics somehow I think. Alternatively, we could use a piece of metal that sits on the cage system like this but, without the hole. If that doesn't seem good, then we can get a flip mount and put something opaque in it.