My laser makes a red lit dot in thin air...

[Low-Q]

I just tried this with a few different plastics, and a LOC red runnning at about 420ma, and was unable to replicate it. Do you need the lights off to be able to see it? Around what temperature was it when you tried it ?

Hi,

It is visible indoor, at normal room temperature with all the lights turned on - no problem. You need to burn the plastic and then remove it gently. I use black plastic "Jumbo Highlighter" pen. The material is quite soft and "fat", and it feels like nylon, and it doesnt decompose in acetone.
The focus length I use is approx 1 inch. I have also 3,35V on the laser - and I don't know what the current is. That should be possible to find out. And I recently found out that It makes a hole in a black CD case in just one second - at focal distance (1 inch). At 2mm beam diameter it takes approx 15 seconds to make a hole in that CD-case. So maybe you got a clue what the optical power is.

Edit: It worked for a short moment on black CD case plastic, but not as well as that highlighter pen.

Br.

Low-Q

 

[dar303]

Mixedgas over att PL has been kind enough to write an explanation for us:

"yeah I can explain it. Its optical trapping of dust particles at the beam waist. The high electromagnetic field at the crossover point causes very tiny charged dust particles to be pushed into the core of the beam.

no plasma, just dust scattering the light.

Its a well known thing. Usually doesn't occur in air like that, but I've seen laser beams at 2-3 watts drag in dog hairs on my projector into the center of the beam.

There is a very tiny ceramic dust, carbon soot, or something else reinforcing the plastic, and its drawn into the beam after the combustion and held there,

1. hard to reproduce
2. wont happen with just any laser
3. right place at the right time with the right material sort of thing.
4. usually needs more then 1 beam.
5.remember the light field just flows around objects any shorter then say a wavelength, hence the trapping.
6. works best with lower powers.

This is mundane in the scientific community, its used all the time to trap bacteria and other small objects in front of microscope objectives.

google "optical trapping""

 

[Low-Q]

Cool effect, I'll have to give it a try.  Does it work with the carbon from a pencil?  Chunk of tire rubber?  It sounds likt the lenses you are using allow a very small focal point, smaller than the typical plastic lens variety, I wonder is the multi-element glass aixiz variety is adequate?

The graphite you find in pencils doesn't even make smoke. Nothing, and absolutely nothing happens. However, carbone lumps from my wood-burning stove glows bright white (2500 - 3000K) and makes almost no smoke - and it is not good for making shiny red balls. Honestly, the highlighter pen is the only material I have had greatest success with till now - it smells hot motor oil from the vapour...I tested just now. Syntethic black rubber works in fact great too. The black insolation on wires just makes small geysers blowing hot insolation vapour into the lens. Not good for shiny balls.

Is this the lens you are thinking of?
http://www.aixiz.com/shop/product_info.php?cPath=1_31&products_id=34

Br.

Low-Q

 

[Elektrotechniker]

holy...

 

[Low-Q]

Mixedgas over att PL has been kind enough to write an explanation for us:

"yeah I can explain it. Its optical trapping of dust particles at the beam waist. The high electromagnetic field at the crossover point causes very tiny charged dust particles to be pushed into the core of the beam.

no plasma, just dust scattering the light.

Its a well known thing. Usually doesn't occur in air like that, but I've seen laser beams at 2-3 watts drag in dog hairs on my projector into the center of the beam.

There is a very tiny ceramic dust, carbon soot, or something else reinforcing the plastic, and its drawn into the beam after the combustion and held there,

1. hard to reproduce
2. wont happen with just any laser
3. right place at the right time with the right material sort of thing.
4. usually needs more then 1 beam.
5.remember the light field just flows around objects any shorter then say a wavelength, hence the trapping.
6. works best with lower powers.

This is mundane in the scientific community, its used all the time to trap bacteria and other small objects in front of microscope objectives.

google "optical trapping""

Thank you very much for this information Nice to have an explanation to this. Maybe if I reduce the power a bit, the trapped dust will last longer?
What about trapping the bacterias? Wouldn't they simply turn into dust in no time?
Last, but not least: I have been very lucky to be able to reproduce this with ease

From Wikipedia: http://en.wikipedia.org/wiki/Optical_trapping

Br.

Low-Q

 

[artix]

WOW! I just tried that with a sharpie! It is awesome!!!!!!

*uploading video*

 

[artix]

[media]http://ca.youtube.com/watch?v=R6gkXkHzIsM[/media]
http://ca.youtube.com/watch?v=R6gkXkHzIsM

 

[Things]

I just did it too!. Those people trying, focus your laser down to a small point, as close to the lense as you can, sit the laser on a table (The heat rising from your hand makes the effect die quicker), and use the tip of a dark coloured texta/marker. They arent as big looking as they are in the video, but once youve got one, you wont miss it!

Make sure to do it in a room with minimal airflow too.

 

[disma]

I was able to do it with an open can doing about 235mw, and an aixiz module with the plastic lens.

Whats strange is I couldn't do it with my 1w laser at exactly 998mw. :-?

 

[artix]

I was able to do it with an open can doing about 235mw, and an aixiz module with the plastic lens.  

Whats strange is I couldn't do it with my 1w laser at exactly 998mw.  :-?

Is that a sharpie? Try it without the cap on.

 

[Xplorer877]

I did it too!!! ;D I used my open can laser about 220mW glass optic and a blue sharpie. It only lasted about 1 second. I could see from the smoke that the air in my house was not very static. I didn't know that focused laser light generates magnetic fields. :-?

 

[Low-Q]

I was able to do it with an open can doing about 235mw, and an aixiz module with the plastic lens.  

Whats strange is I couldn't do it with my 1w laser at exactly 998mw.  :-?

I guess that too much power will burn away the particles the beam is supposed to trap. However you can try to focus the beam at longer distance, then the energy density isn't that high. Maybe you are able to make a levitating red dot at 2 - 3 feet distance?

Low-Q

 

[sad_sagi]

oh wow... it works ;D
my dilda (See sig) at about 200mw will do it. im looking at it through my cell phone so i wont blind myself and it did it the first try... freaky

 

[disma]

ok, so now has anyone tried to see what effect a magnet would have on it while its suspended there in the beam? :-? Also, Im gonna have to see if my small sheet of magnetic film will detect the beam, its gonna be hard to not hit the film with the laser.

 

[kernelpanic]

ok, so now has anyone try to see what effect a magnet would have on it while its suspended there in the beam?  :-? Also, Im gonna have to see if my small sheet of magnetic film will detect the beam, its gonna be hard to not hit the film with the laser.

Yeah. No effect. I tried rare-earth magnets pulled from PHR sleds. At first it seemed like moving a magnetic fied killed the effect. But upon repetition, it's obvious that air currents were the culprit. BTW- I found that my 405nm @ 130mA works WAY better than 650 @ 420mA. The phenomenon is much easier to reproduce! Also the blu-ray doesn't seem to care what you burn. I easily get it to 'grab' particles of wood smoke from my desk. The phenomenon also lasts longer with the blu-ray for some reason... Green would probably be the bomb also. But I don't have a green burner to try.  :'(

Honestly, everyone- Try This. It's a really neat and fun science experiment to do! I will say though that the things people are burning to get this effect(plastics) release some very toxic fumes. The criteria for what can be 'grabbed' by this method is the size of the particle. Surely there is something safer to burn than cyanoacrylics, or whatever highlighters are made from?

Just a thought...

cheers,
kernelpanic

 

[artix]

Hey disma!

Can it be that you just can't see it? Try it through your IR camera.