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Optical trapping! ball oflight stuck mid-air!

creanzworld17

creanzworld17

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What is exactly going on here? Scientifically speaking. I can do it over and over, but i have no clue what is initially going on. Im pretty sure it is optical trapping. Ive read about OT with microscopes using optical tweezers. It is cool though to watch. Here are a few pics of it.


The red ball is floating. It looks like it is on another surface, but its not. And ignore the 6v. Its just propping up the module. The power supply is a 7.2v rechargeable batt pack.
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Optical trapping is based around an interesting property of light. Namely, there is something called the wave-particle duality which applies to, among other things, light. It basically states that light can be represented as having both "wavelike" phenomena and "particlelike" phenomena. For example, diffraction patterns are basically a wave phenomena, but if you were able to control the light such that only a few photons were to be incident onto a surface, you would see that the diffraction pattern turns into a bunch of tiny single photons. (Fun fact: the eye can see down to something like 6 photons).

Anyways, when representing light as a particle (photon), it becomes apparent that these particles have momentum. And because they have momentum, they have some kind of energy. And because they have an energy associated with them, they can impart that energy onto other particles, yielding a force.

So, if you have a tiny little object like a microscopic piece of burned sharpie, the force vector from the surrounding light tries to push this particle into an equilibrium position, which is right in the center of the beam. A while back, someone posted a diagram of how the force vectors look; it would be helpful in visualizing what's going on.
 
For some reason this works extremely well with sharpies, numerous forum members have reported to get similar results. At first i was amazed it actually worked, but for some reason the sharpies seem to release particles that are small enough to be trapped yet big enough to produce a visible reflection.

There is even a video of someone moving the laser around keeping the particle trapped in the beam.
 
jwc said:
Optical trapping is based around an interesting property of light. Namely, there is something called the wave-particle duality which applies to, among other things, light. It basically states that light can be represented as having both "wavelike" phenomena and "particlelike" phenomena. For example, diffraction patterns are basically a wave phenomena, but if you were able to control the light such that only a few photons were to be incident onto a surface, you would see that the diffraction pattern turns into a bunch of tiny single photons. (Fun fact: the eye can see down to something like 6 photons).

Anyways, when representing light as a particle (photon), it becomes apparent that these particles have momentum. And because they have momentum, they have some kind of energy. And because they have an energy associated with them, they can impart that energy onto other particles, yielding a force.

So, if you have a tiny little object like a microscopic piece of burned sharpie, the force vector from the surrounding light tries to push this particle into an equilibrium position, which is right in the center of the beam. A while back, someone posted a diagram of how the force vectors look; it would be helpful in visualizing what's going on.
Click to expand...
Alright, thanks for that. It made a little bit more sense now.
Benm said:
For some reason this works extremely well with sharpies, numerous forum members have reported to get similar results. At first i was amazed it actually worked, but for some reason the sharpies seem to release particles that are small enough to be trapped yet big enough to produce a visible reflection.

There is even a video of someone moving the laser around keeping the particle trapped in the beam.
Click to expand...

Yeah i have a video of it, and i am moving it around with the particle trapped. If you move to too fast, it obviously dissipates into thin air. I tried with my blue ray at 100mw's, but not as successful as the red LD, probably needs more power too. I'll try with the IR as well.
 
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Dang. Good camera quality? What are you using? Mine is a 10mp...and compared to that pic, it feels wimpy now. Lol.
Yeah good shot though. I got a few of the 2x or 3x particles, but they don't last long at all.
 
I have a Panasonic DMC-FZ35 (12.1MP, 18x optical zoom). The trick is to get the focus right. My camera supports manual focus, so I did a very rough adjustment to bring the dots into focus; clearly, I could have done much better (I also should have played around with the exposure time a bit).
 
:tinfoil: Really odd. Whats the power of modules your using? *searches for closest sharpie*
 
i am using the Aixiz module, with a 20x LD, with an output of 400ma. I then focus it as close as it can get (with this lens, it is about 1")
 
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