Is this possible? (~100w spotlight white laser)

[Glaserfan]

Hello all!

Another crazy idea of mine(though I have a feeling it has been tried already)..

How about using a large lens(which I have many of in the form of large CRT projection lenses) in front of a 100w spotlight to create a laser? Basically the large lens focuses the spotlight's output down to a tiny spot(just like burning an ant with a magnifying glass). Then at the focal point place an expander lens, then a collimating lens to create a nearly 100 watt white laser beam..

I am guessing it will need glass optics and a heatsinked module.

What do you guys think? Will this work or not? Here is a quick diagram thrown together in paint..though I should have done it in a black background..

EDIT: My idea is to house this whole thing so the only light escaping the housing would be from the module's aperture.

 

[Benm]

Re: Is this possible? (~100w spotlight white laser

It is not possible to create a beam with good divergence or width from a light source as large as a lightbulb filament (or even LED die). It is possible to focus the light down to a tiny spot at a give distance and burn something, as is easily demonstrated with a halogen bulb and lens.

Obviously it would also lack coherence and monochromaticity and not be a laser at all.

 

[Glaserfan]

Re: Is this possible? (~100w spotlight white laser

Rats... all i was hoping to do is collimate the light into a beam- color wouldnt matter just a very powerful beam. I did get the idea from how a green laser works.. the module from it produces a beam out of an led flashlight fairly well...

 

[GooeyGus]

Re: Is this possible? (~100w spotlight white laser

Rats... all i was hoping to do is collimate the light into a beam- color wouldnt matter just a very powerful beam. I did get the idea from how a green laser works.. the module from it produces a beam out of an led flashlight fairly well...

Hmmm? Kind of confused on what you mean by this. The IR diode from a green laser is still coherent light, as is the light emitted by the crystals after they are pumped.

 

[pwnstar]

Re: Is this possible? (~100w spotlight white laser

As I don't completely understand why it wont work; I do completely understand no, it wont work.

 

[lazerguy]

Re: Is this possible? (~100w spotlight white laser

A laser is coherent (all light waves goes in pace with each other) and monochromatic (one color, one wavelength) while white light is a mixture of all wavelengths. So even if it would work to collimate the beam like a laser, it would not be a laser. Just a very powerful beam of white light. It would be fun if it would work though.

 

[Switch]

Re: Is this possible? (~100w spotlight white laser

Here is a quick diagram of why it won't work ;D

Even if you did have a small emitter with coherent white light, because the lens has different diffraction indexes for different wavelengths, you couldn't collimate them all at once.

Here's an experiment: try to focus an image of a bulb or hallogen bulb or neon sign or whatever with a large lens on a white surface.You're gonna get an image of the filament or bulb itself and NOT a tiny pinpoint spot of light.

 

[Glaserfan]

Re: Is this possible? (~100w spotlight white laser

Hmm.. I understand this now... BUT, what if I put a color filter in front of the spotlight? And perhaps mask the front of the bulb so that the only light coming out is straight from the parabolic refector. I'd lose some power, but might get monochromatic, fairly coherent light anyhow...

Remember I am not going straight from the bulb to the expander.. I am trying to place the expander right at the focal point of the large lens..

I may just try this anyhow to see what happens, I understand what the problems are here, and am in no posistion to doubt anyones input(whish is why I asked).. but I am the type that tries anything. If I fail, hey at least I tried LOL. If this thing can somewhat work, even not perfect, and even at perhaps 70w(after filter) of say green light, it'll still be one powerful ass beam of one sort or another.

 

[GooeyGus]

Re: Is this possible? (~100w spotlight white laser

I don't think anyone is saying that it wont be strong, and that it wont be a beam of light, it just wont be a laser

It the same principle as frying ants with a magnifying glass under the sun. Powerful? Yes. Laser? No.

 

[Benm]

Re: Is this possible? (~100w spotlight white laser

Exactly, you would basically end up building a spot/searchlight.

Even if we forget about monochromaticity and coherence for a while, just looking at the size of the light emitter demonstrates the problem: In a laser diode, the light emitting area is in the order of the wavelegnth, a bit under 1 micrometre for a red laser.

Even a very compact lightbulb has a filament that is at least a few mm in size, i.e. serveral thousand times larger than the laser. This would result in a divergence or beamsize difference of the same magnitude.

It can still look very good though, just look at what they do in disco lightshows based on (rather powerful) halogen bulbs and color filters.

 

[Switch]

Re: Is this possible? (~100w spotlight white laser

Btw, I think 100W is power consumption not output.And you're not going to get 70% of green light out of white.Besides, the green part in white light is many wavelengths too, not only a single line like say 532nm :.If you were to separate a single line you could probably end up with less than 5% (or even less,just guessing) the rest being filtered away.You could try it , and even if you had some good optics, you would end up with a HUGE beam diameter and a bigass 10mRads or so.Fine if you want to illuminate something far away or flashblind someone, but forget about burning anything farther away than a few cm. :-/

 

[Glaserfan]

Re: Is this possible? (~100w spotlight white laser

Understood.. Wel it was a neat idea anyhow.. but now I see why it doesn't work all that well..

I may still try it and try to make it a focusable setup like a red burner.. even if I could get it to burn a few feet away, I bet it'd have enough power to do some serious burning...

My red burner w/ AixiZ module doesnt have any sort of impressive beam as far as I am concerned,(but of course tho it's fat it still is a laser beam when at infinite focus), BUT it still does what I want it to do because I can focus it down at any certain point within it's reach..

Now I am sure by what you guys are saying that I'll have a terrible quality beam(the shape of the reflection from the spotlight), but that tiny focal point, at a distance I am sure will exceed the reach of the large lens itself, is my main goal. Even with the heat waste and maybe only 50w of power at the "beams" focal point, that far exceeds the power of ANY of our DIY burners..

Sometime when I try I will post the results. I hope to at least end up being able to focus all that light(as much of it as possible) down to a tiny spot close to that of my red burner's. At least I know what to expect now though and it won't be a huge dissapointment when most of what I get is light spatter

 

[Switch]

Re: Is this possible? (~100w spotlight white laser

If you want to see potential results go check out the WL Torch.It's a 100W incandescent bulb(I think) or the Mac Light(?) on candle power forums(? again) which is the same as the WL Torch. It can set newspaper on fire pretty quickly with that diverging "beam". You could probably get way better results if you focus it so that it has a narrow waist a foot away, but don't think you will ever get close to a spot as tiny as you can with a laser.Still energy density is going to be bigger than most handheld lasers, so you're probably gonna get that "magnifying glass with sun included" effect if that's what you're looking for.I still don't think it's 50W of actual power output though, and doesn't matter if it's at the focal point or not, total power is the same anywhere(leaving atmospheric junk aside)."Power density" is the notion you're looking for.

Oh don't forget, 10 minute battery life

 

[Glaserfan]

Re: Is this possible? (~100w spotlight white laser

Cool I'll check that out. Power density is my main goal, basically a "super burner". A nice bright whitish beam(even if fat) would have been nice, but oh well lol. As long as I get something with somewhat flexible focus that can do some decent frying I'll be happy. ;D It would be nice to get some distance out of it too, but that doen't seem to be an option here. I was hoping for about a ten foot focal range..

It'll be fun to build and try anyhow

Too bad I won't have a meter to test the output... it'd be intersting to know what the actual input to ouput ratio is on this rig. Hell even if I only get 20w focused on a 1.5mm dot I am sure it'll be fun I plan on trying this with glass lenses of course.. I think acrylic might just melt LOL. I'd rather not waste my good modules..

 

[Switch]

Re: Is this possible? (~100w spotlight white laser

You're gonna need some bigass glass lenses , not laser collimating lenses And 1.5mm dot....dream on ;D Anyway, I don't think measuring a flashlight with a power meter would be acurate. :

 

[n-sane]

Re: Is this possible? (~100w spotlight white laser

White light won't ever travel like a laser unfortunately because it contains all primary colours (hence several wavelengths); since different wavelengths travel faster then others, your beam will always diverge. It'd be a very very small flashlight basically... focused one @ that. You could do somewhat of the same thing with the sun