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Optical Trapping - Real Laser Tractor Beams

LarryDFW

LarryDFW

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"Optical Trapping" experiments capture smoke particles in the laser beam at or near the focal point of the beam.
When the dielectric smoke particles drift outside the focal point,
diffraction of the laser beam creates an opposing force & pushes them back toward the focal point.
This is a diagram showing the basics:
250px-Optical_Trap_Ray_Optics_Explanation.jpg


I set up my Red OC in a draft-free area with a new single lens I assembled.

Set the focus at about 3/8" on a black felt tip marker to generate plenty of smoke particles.

The results were fascinating.

Initially, I got 5 or 6 red balls captured in the beam + or - 1/8" around the focal point.

They danced apart ...

then crashed together into larger balls ...

and then finally combined into one large ball over several seconds.

I plan on more experimentation with some different lens assemblies.

Edit: Photo in post #12.

Low Q has posted some videos on YouTube of his results:

YouTube - Optical trapping !! 16x DVD laser makes a glowing dot in thin air!!

YouTube - Optical Trapping part 2 !! 16x DVD laser makes a lit red dot in thin air. Part 2

YouTube - Optical Trapping Part 3 !! Close Up Video - Now 1min 30sec video

LarryDFW

P.S. Be careful to keep the smoke away from the lens surface. I aimed my laser slightly above horizontal.
 
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Re: Optical Trapping Fun

Jeff;

Thanks, I caught it right after I posted.

Have you played with this phenomenon ??

High-Tech Laser Capture Beams

LarryDFW
 
I dont have a red laser currently, but by the end of the week my parts should be here to do my loc build. The first experiment im going to try is this!!
 
I have a 20x LOC. What exactly do you recommend to reproduce these results?
 
wow interesting :gj:
now let's wait until my LPC sled arrive...

is it possible to do it with other colours? (green, violet)
 
wait. This is the most awesome thing I've ever seen. HOW ARE YOU DOING THIS?!

:drool::drool::drool::drool::drool::drool::drool::drool::drool:

you just focus a red beam and put smoke on it?
 
I saw something like this posted a year or so ago but I forgot about it. Thanks for the reminder -- facinating to watch.

HMike
 
HOLY CRAP I JUST TRIED IT AND IT LOOKS SO KICK ASS!!
k so all you do is take a red laser, pretty high powered, (i used my dilda)
then, take a sharpy (which i find easier to use) and focus the laser on the tip of the marker.
dont hold the marker over the laser for long and just take the laser out of the way of the laser and boom! you see a tiny little particle. it takes a little practice and the laser has to be perfectly still and in an area with no drafts.

Also to answer 3zulis question
i just tried it with my phr labby, and it worked a few times but its a little bit more tough.


thanks Larry for such a great find!
 
It works with a green laser too, but I have not tried it with 405nm. I haven't captured any video of it with a green laser, and I do not have a green laser at the moment. The power was about 50mW, but i'll assume it works better with little more power - 100 to 150mW. More power just makes a geyser out of the melted plastic crater in my "Jumbo Highlighter", and just blows away the particles. The particles must be quite small I guess because it does not disturb or block the beam. Maybe just a few molecules in size. Soon I will recieve a new 405nm laser. My present 405nm laser died when I got too close to my TV screen. I heard a few sparks between the laser and the screen, and there it died - RIP...
 
Hemlock_Mike said:
I saw something like this posted a year or so ago but I forgot about it. Thanks for the reminder -- facinating to watch.

HMike
Click to expand...

Yeah, we talked about it in the Science & Lasers section.

We should post more in that section... I'll get some time to do it on January :)
 
Here's one photo showing four separate optical traps:
optrap.jpg

They eventually merge into one brighter particle after a few seconds.

The laser can be moved around with the particles fixed in the "tractor beam".

LOC laser with Hi-Power lens assembly.

LarryDFW
 
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I have tried this before as well. The key is NO DRAFT. If you are in a bathroom you need to put like a towell at the crack under the door.
 
Just tried it with my 12X... the tape burns way too vigorously for it to work.. I'll try with my PHR a little later...
 
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