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

[Low-Q]

Maybe a silly question: does it work if the laser is aimed downward onto the plastic, instead of upward?  Both videos show it being upward, at least that's what they appear to show.

It works in any position, but the vapour from th plastic is hot, and rises - then covers the lens. However, the main reason at the time I made the video, was that the focusing lens inside the laser wasn't fixed at the moment - they fell out if I turned the laser upside down

 

[Switch]

Wow that's really amazing!! I've burned lots of stuff with my lasers and this is like nothing I've ever seen before.I've been a member for a year now, and if this has been posted before I surely missed it.

Well the first thing that comes to my mind is that the people making the 3D scanner could use this instead of a high power YAG laser. :-/

I'm gonna go and try to make this happen now.

Another question though: While the dot is there, would quickly turning the laser off and then on again make it dissapear or would it just reappear when you turn the laser on again?

 

[diachi]

Who is FrothyChimp ?

br.

Low-Q

He is a very knowledgeable member here. He has a really good understanding of physics and would most likely know an explanation for this.

-Adam

 

[ElektroFreak]

Recently there have been developments in lighting involving the use of lasers to generate plasma points in mid air. This technology is being used to generate free-floating 3D holograms (kinda like Star-Wars), and in drawing devices to allow a person to "draw" in mid air with plasma. Here's an example: http://gizmodo.com/gadgets/small-ba...ions-in-mid+air-using-plasma-balls-289337.php

If I had to guess, I'd say you're witnessing this type of phenomenon with your laser, which is causing a small point of plasma to appear for a few moments..

 

[Switch]

That's not exactly news....But doing it with a CW ~150mW red laser? If that is what it is, the smoke's composition must be helping a lot.

 

[ElektroFreak]

That's not exactly news....But doing it with a CW ~150mW red laser? [highlight]If that is what it is, the smoke's composition must be helping a lot.[/highlight]

Didn't say it was news (man I wish people would read stuff fully before criticizing).. but it's the only explanation I could think of. I'd say the highlighted portion above is key..

 

[Low-Q]

Wow that's really amazing!! I've burned lots of stuff with my lasers and this is like nothing I've ever seen before.I've been a member for a year now, and if this has been posted before I surely missed it.

Well the first thing that comes to my mind is that the people making the 3D scanner could use this instead of a high power YAG laser. :-/

I'm gonna go and try to make this happen now.

Another question though: While the dot is there, would quickly turning the laser off and then on again make it dissapear or would it just reappear when you turn the laser on again?

Hi!
If I turn the laser quickly off-on the point dissappear. 2 minutes is for now the longest time to keep the dot shining, but then the laser get a little bit hot (not much), so I had to turn it off - just to be safe.

Br.

Low-Q

 

[Hemlock_Mike]

Making those plasma balls takes power. I've done it using a single pulse from a NdYAG and a close focus lens.

Mike

 

[Low-Q]

Making those plasma balls takes power.  I've done it using a single pulse from a NdYAG and a close focus lens.  

Mike

I bet, but maybe it's easier to make plasma balls with less power if the air is saturated with vapour first - something denser than air which absorbs more energy from the laser. Like a catalyst (?). Strange that the balls I make lights red (Or green if I do it with my green laser). Shouldn't it be more white if the heat is so intense?

br.

Low-Q

 

[ElektroFreak]

Does it only produce the floating spot when you're burning that highlighter?

 

[Low-Q]

Does it only produce the floating spot when you're burning that highlighter?

Yes. It will not work if I don't burn this pen.

Low-Q

 

[ElektroFreak]

[quote author=ElektroFreak link=1229287299/20#25 date=1229383413]Does it only produce the floating spot when you're burning that highlighter?

Yes. It will not work if I don't burn this pen.

Low-Q
[/quote]

Then that makes me think it's even more likely that something in the highlighter's smoke is forming that small point of plasma. Definitely pretty interesting at such low powers..

 

[Benm]

Making those plasma balls takes power.  I've done it using a single pulse from a NdYAG and a close focus lens.  

Mike

I bet you are just breaking down air with those... I've seen it demonstrated a couple of times, spark just appears in mid air. This also makes a bluish spark from an IR laser, and doesnt require burning anything first.

The video is quite remarkable, i've never seen anything like that happen. Does it always happen, or is it something you have to try many times before getting this effect?

 

[Xplorer877]

Hi. I have a 635nm laser from a 16x DVD burner. When I focus this laser on a plastic piece, a red lit small dot remains in thin air for as long as the laser is activated - somtimes shorter time. So I wonder if someone knows what is happening. Is it plasma from platic vapour, or what is it?

I'm not allowed to post links here yet, but on youtube you can paste in these two lines at "YouTube dot com slash" to find the videos:

watch?v=9AzdMJSvuUU&NR=1

and

watch?v=ig_L3PnSuo0

br.

Low-Q

635nm? :-? How do you know it's 635nm? Which DVD burners containing 635nm diodes? I've never heard of that.

 

[Low-Q]

[quote author=Hemlock Mike link=1229287299/20#23 date=1229380068]Making those plasma balls takes power.  I've done it using a single pulse from a NdYAG and a close focus lens.  

Mike

I bet you are just breaking down air with those... I've seen it demonstrated a couple of times, spark just appears in mid air. This also makes a bluish spark from an IR laser, and doesnt require burning anything first.

The video is quite remarkable, i've never seen anything like that happen. Does it always happen, or is it something you have to try many times before getting this effect?[/quote]
Hi,

Often it takes only one attemt. I'll guess it takes 2 - 3 attempts in average to make a stable dot - for minutes.

Low-Q

 

[Low-Q]

[quote author=Low-Q link=1229287299/0#0 date=1229287299]Hi. I have a 635nm laser from a 16x DVD burner. When I focus this laser on a plastic piece, a red lit small dot remains in thin air for as long as the laser is activated - somtimes shorter time. So I wonder if someone knows what is happening. Is it plasma from platic vapour, or what is it?

I'm not allowed to post links here yet, but on youtube you can paste in these two lines at "YouTube dot com slash" to find the videos:

watch?v=9AzdMJSvuUU&NR=1

and

watch?v=ig_L3PnSuo0

br.

Low-Q

635nm? :-? How do you know it's 635nm? Which DVD burners containing 635nm diodes? I've never heard of that.
[/quote]Maybe I have to rethink about that... I assumed DVD lasers was 635nm - that is what I have heard. Actually both 650nm and 635nm. The red light is also orange red light - not that deep red light you get from 650 - 670nm lasers. I have to check, but as I remember I had a 635nm laser pointer once which had the same kind of "orangeish" red light.

Low-Q