Recent content by kubikat

Here is the link to where I posted my thesis paper + the manual. https://sites.google.com/site/anyakash87/physics/optical-tweezers It is written specifically for our equipment, so I don't know if it would be much help. Also it is written for college sophomores/juniors with no experience...

Ah I was meaning to thank everyone who helped me build mine. That was extremely nice and finally allowed me to graduate :D @hopeful: If you are an undergrad, I can probably help you out. I have written a manual on how to build a tweezer. But if you are a grad/have some optics experience...

Oh and the cluster of the particles on the bottom is where a beam used to be before I moved it. I can also use the beam to grab particles one by one and arrange them in shapes.

Hi Andy! Thank you a lot for your pictures. They were really helpful, since now I had a better idea of what I was looking for, looking at the beam. I finally got trapping! It was really really exciting. The trap was very strong and kept literally sucking in the particles from within of like...

Oh okay, so that's just diffraction? I do send a beam through a small circular lens that I put into the diode module for collimation. Where shall I keep the telescope then? At the position that gives me a more pronounced diffraction pattern (far away from the laser) or near the laser where I get...

Also I am sorry the pictures of the beam are so huge. I tried making them smaller on the host website and then add them in here again. but they wouldn't change

And here is the beam pattern that I see when beam comes out of the laser and hits the first lens after the focal point (this one is when the path length of the beam is rather short). I am not sure why I get the rings. Here is how the beam profile changes as it travels longer distances. At...

Here is the image of my whole setup. I am using a diode laser. 100x oil immersion objective and the telescope lenses I currently use are 50mm and 250mm focal length. And here is where I am trying to trap them. I am planning on making sort of a flow cell once I can actually trap something...

My setup is very simple ( it is inexpensive for one and then my professor wants me to set it up and write a manual so students in the advanced physics course would be able to set it up themselves --- so it has to be simple). It is all in one plane - horizontal. I personally think that the...

And I did figure out the mirror had nothing to do with the pattern :D it was all in the path length difference... Thank you ! I still don't know why the path length difference matters so much but it's nice to narrow it down :)

Oh yes and the pattern was viewed after the focus (it might have been there before, just was too tiny to see)

Andy, that's strange that we can see the beam then. Maybe our diode is not 780 nm after all :/ That's what the specs say though... (By the way I did not find out that I can see the beam until one day I forgot to put the safety glasses on...) I always wore the glasses and used to use cheap cell...

Yea, I look at the beam when it hits a white piece of paper. It is red. Since I turn the power down to 2-3 mW it shouldn't be harmful right. Usually when I am working at the high powers I use glasses.

Thank you both again very very much. I didn't expect to receive that much useful information and advice! I think my mirror is the front surface. I have seen both front surface ones and non front surface ones and and the ones I tried look like front surface. Is there a way to check it? The...

The beam is an 80 mw diode laser... pretty cheap one. I think the diode only cost $30... It is supposed to give out an elliptical beam. I have it collimated and the beam looks pretty circular (to within you can't tell that it's not circular) and about 1.5-2 mm in diameter. I was going to use 2...