# supercontinuum white light laser



## AlexGT (Apr 24, 2004)

*Do white lasers exist?/supercontinuum white light laser*

Plase excuse if it's a dumb question, but I was wondering if such lasers exist. 

Thnx!
Alex


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## gwbaltzell (Apr 24, 2004)

*Re: Do white lasers exist?*

I don't think I class this as dumb but it makes me wonder what you'd use it for, other than viewing holograms. I've read about combining the beams of three LASERs to produce white just as your computer screen uses three colors to produce white.


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## xochi (Apr 24, 2004)

*Re: Do white lasers exist?*

Hey AlexGt, 
Something that I've realized is that the only thing dumb about any question are the idiots who act as though you've asked a dumb question.
As far as white lasers are concerned I don't think they are possible because a laser requires very special treatment of light in order to amplify it. Because the different wavelengths of light all respond slightly differently when passed through optics the frequencies that end up "lased" must be targeted when picking the optics , etc to create a laser. Keep in mind also that my understanding of lasers is a faded memory from high school so I could be wrong. I think that attempting to create a full spectrum laser would only result in a massively inneficient power suction machine.


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## BillBill (Apr 24, 2004)

*Re: Do white lasers exist?*

The fact that lasers are monochromatic (i.e. one color and wavelength) allows photons in the laser beam to reinforce each other to travel great distances. The inside of a laser allows only one wavelength and frequency of light to be produced, and in effect, a laser has a single natural frequency.

However, white light consists of many wavelengths and frequencies. It is obvious that multiple wavelengths cannot be produced by a single laser. I'm not sure if one can combine the beams of many different-colored lasers to produce a white beam. The photons of such beams may do all kind of weird things. Fiber optics cannot be used because the exiting beam is no longer collimated. Also, there may not be a use for a multiple wavelength laser. 

"White laser" is an oxymoron. They don't exist (yet).


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## Nitro (Apr 24, 2004)

*Re: Do white lasers exist?*

http://www.cookecorp.com/lasers/


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## gwbaltzell (Apr 24, 2004)

*Re: Do white lasers exist?*

Decided to Google™ it. Results: tunable fiber optic, same question another board, hologram board, a commercial while LASER (RGB)

search was:
"white laser" -printing -labels -printer -paper -tooth
list was just a few of the results

I see Nitro found another commercial unit while I was typing so the short answer is: *Yes*


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## Quazar (Apr 24, 2004)

*Re: Do white lasers exist?*

White lasers are readily available if you want a gas laser. They usually use a mixed gas, Argon(produces green and blue)and Krypton (produces red and yellow)they are available in powers from 300mW to well over 10 watts.Anything over about ! watt usually requires £ phase electricity and water cooling. I have seen white diode systems, but they are usually 3 seperate diodes(green,red and blue)sharing a common case.I hope this helps.


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## AlexGT (Apr 24, 2004)

*Re: Do white lasers exist?*

Thanks for answering the question, do you know of any online videos about lasers cutting metal or other materials? 

Thanks!

Alex


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## BillBill (Apr 25, 2004)

*Re: Do white lasers exist?*

[ QUOTE ]
*BillBill said:*
The fact that lasers are monochromatic (i.e. one color and wavelength) allows photons in the laser beam to reinforce each other to travel great distances. The inside of a laser allows only one wavelength and frequency of light to be produced, and in effect, a laser has a single natural frequency.

However, white light consists of many wavelengths and frequencies. It is obvious that multiple wavelengths cannot be produced by a single laser. I'm not sure if one can combine the beams of many different-colored lasers to produce a white beam. The photons of such beams may do all kind of weird things. Fiber optics cannot be used because the exiting beam is no longer collimated. Also, there may not be a use for a multiple wavelength laser. 

"White laser" is an oxymoron. They don't exist (yet). 

[/ QUOTE ]

Sorry for my ignorance. /ubbthreads/images/graemlins/blush.gif Need to give things more thought. /ubbthreads/images/graemlins/icon23.gif


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## Canuke (Apr 28, 2004)

*Re: Do white lasers exist?*

not just you ,BillBill; I found out about white LED's that way. I also thought they had to be monochrome, but never considered the phosphor angle until I saw one.

And now I stand corrected about white lasers too.


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## Doug Owen (Apr 28, 2004)

*Re: Do white lasers exist?*

No.

There are, as others have pointed out, *multi colored* lasers, but by definition, they are not white.

White is a 'mixture of all colors', right? RGB is a *simulation* of white.

Nor do they constitute a *laser* (singular) but rather three or more different lasers (plural) in the same package.

Laser light has three characteristics, it's monochromatic (all exactly the same color), coherent (all in the same phase), and collimated (all going the same direction). Even ignoring the first aspect, it's clearly not possible for waves of two different periods (different colors) to stay in phase. Even though the RGB laser systems might be collimated (not always a given), it's clearly not possible for them to be coherent. This means they won't exhibit the same interference common to laser optics either.

So, marketing hype aside, no. Them's da rules.

And as others have pointed out, there are no 'dumb questions', only dumb answers.......

Doug Owen


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## INRETECH (Apr 28, 2004)

*Re: Do white lasers exist?*

A laser is a very very narrow band amplifier, which means it is monochromatic

There are some lasers that have several lines, but a White Laser would be impossible - since White light is a very wide spectrum of frequencies (wavelengths)


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## MicroE (Apr 29, 2004)

*Re: Do white lasers exist?*

When I took my first optics course all holograms were monochoromatic. It was impossible to make a white light hologram. Then somebody did it. Now they are everywhere. A white light laser is only impossible until somebody makes one.


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## gwbaltzell (Apr 29, 2004)

*Re: Do white lasers exist?*

Well, going by the rules, there currently is no such thing as a white LED or fluorescent lamp and that computer screen your looking at can't produce white! White, like color, is a perception. And blue and yellow do not make green. We simply perceive it as green. The right mix of two colors or preferable three causes the perception of white. Now, because of phasing, I don't know if a white LASER could be used to produce a hologram (without sequencing the colors), but it I think it still qualifies as white and a *L*ight *A*mplification by *S*timulated *E*mission of *R*adiation. Coherence is a property of many LASERs, not the definition.

BTW - most LASER diodes have very poor coherence. Both spacial and temporal.
And I still don't know what white LASERs would be good for except light shows and viewing color holograms.


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## UVLaser (Apr 30, 2004)

*Re: Do white lasers exist?*

White lasers would be good in flash lights, if you want a narrow beam. But if you don't want a narrow beam put a lens in front of it.(I don't remember what the lens name is, its the type of lens that widens the beam. Can any one help me?.

Hope that helps

~Michael~


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## zumlin (Apr 30, 2004)

*Re: Do white lasers exist?*

Lexan Diffusion Film (LDF)??


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## kakcoo (Apr 30, 2004)

*Re: Do white lasers exist?*

[ QUOTE ]
*Doug Owen said:*
No.

There are, as others have pointed out, *multi colored* lasers, but by definition, they are not white.

White is a 'mixture of all colors', right? RGB is a *simulation* of white.

Nor do they constitute a *laser* (singular) but rather three or more different lasers (plural) in the same package.

Laser light has three characteristics, it's monochromatic (all exactly the same color), coherent (all in the same phase), and collimated (all going the same direction). Even ignoring the first aspect, it's clearly not possible for waves of two different periods (different colors) to stay in phase. Even though the RGB laser systems might be collimated (not always a given), it's clearly not possible for them to be coherent. This means they won't exhibit the same interference common to laser optics either.

So, marketing hype aside, no. Them's da rules.

And as others have pointed out, there are no 'dumb questions', only dumb answers.......

Doug Owen 

[/ QUOTE ]

White is a mixture of Red, Green and Blue. RGB is not a simulation of white. If you mix Cyan, Magenta and Yellow, you get black. So Cyan, Magenta, Yellow, Red, Green and blue is all the colors there is. So if you mix Black and white you get Grey. So in other words; Grey is a mixture of all colors. The sun is white because of the different gases in it. (same princip as the gas laser) If you use a glass prism and split the light you will see a Red, a Green and a blue dot. So there is no simulation. You get real white light /ubbthreads/images/graemlins/thumbsup.gif


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## gwbaltzell (Apr 30, 2004)

*Re: Do white lasers exist?*

UVLaser

I think what you're thinking of is concave lens, also called diverging lens. And by the time you get the beam spread out you'll find that the impressive dot of light is not so impressive anymore. I know I've seen the numbers before, can't think of where at the moment. But, right now anyway, a LASER would make a terrible flashlight! But the optics would be really easy to calculate!


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## Doug Owen (Apr 30, 2004)

*Re: Do white lasers exist?*

[ QUOTE ]
*kakcoo said:*
White is a mixture of Red, Green and Blue. RGB is not a simulation of white. If you mix Cyan, Magenta and Yellow, you get black. So Cyan, Magenta, Yellow, Red, Green and blue is all the colors there is. So if you mix Black and white you get Grey. So in other words; Grey is a mixture of all colors. The sun is white because of the different gases in it. (same princip as the gas laser) If you use a glass prism and split the light you will see a Red, a Green and a blue dot. So there is no simulation. You get real white light /ubbthreads/images/graemlins/thumbsup.gif 

[/ QUOTE ]

No, white is *all* colors. Some energy at every wavelength, not just 3 different ones that you see and call white. The 'pass it through the prism and see three dots' test proves it. Very different results than from sunlight or an incandesent lamp, right?

I'm sure you've seen or heard of the spectrum? Red, Orange, yellow, green, blue, indego and violet? That's only the visable part of course. Understand that there are in infinite number of identifiable colors between say green and blue.

It's a quantum thing, ya know.

Bottom line is there's no more a white laser than there is a bell that rings at all frequencies at the same time. Yes, you can use several to get a chord, but that's still only several frequencies (not all).

Fun stuff, but getting dangerously close to estimating the number of dancing angels on the standard pin......

Doug Owen


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## gwbaltzell (Apr 30, 2004)

*Re: Do white lasers exist?*

Dictionary white light. Perception of white is white. Can you, by just looking, tell the difference between green and blue and yellow mixed together?

A page from nist.gov.

And how long have you been seeing angels dancing on the head of a pin? /ubbthreads/images/graemlins/grin.gif


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## Doug Owen (Apr 30, 2004)

*Re: Do white lasers exist?*

[ QUOTE ]
*gwbaltzell said:*
Dictionary white light. Perception of white is white. Can you, by just looking, tell the difference between green and blue and yellow mixed together?

A page from nist.gov.

And how long have you been seeing angels dancing on the head of a pin? /ubbthreads/images/graemlins/grin.gif 

[/ QUOTE ]

Naw, we're a techie bunch. I don't just get to use my (color blind in fact) eyes to 'see' what's going on. Understood and accepted *instrumentation* will quickly separate real white light from pseudo white light.

In Science, perception is never taken at face value as reality. The observer is always assumed biased until proven otherwise. 

Perception is *not* reality. Even at NIST.

For instance, run the (supposed) white light through a diffraction grating, what do you get? A collection of colors, with many missing, right? Clearly not all.

Photons as waves, gotta love it.

And I don't actually see dancing angels (at least since I joined 'the group'), but for those who don't know/understand/tollerate my sort of humor the source is historic. "The Church" amused themselves through the dark ages with just such discussions as 'how many angels can dance on the head of a pin?'. Musta been kinda slow then, funny though there seems to have been at least a few souls in need of salvation?

Doug Owen


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## gwbaltzell (Apr 30, 2004)

*Re: Do white lasers exist?*

My point was that white light, in reality, is only a perception. Yes, the traditional fusion generator in the sky provides us with a continuous spectrum. And all incandescent sources, from fire to heated platinum, are continuous. But if we're going have that as a criteria for the word "white" then what word are we going to use for all non-incandescent visible electromagnetic radiation that stimlulates human retinal cones the same way. BTW we can't use the word light either, because it refers to all electromagnetic radiation from radio waves to gama rays.

And "The Church" also amused itself with such delights as the Inquisition. And among so many things convicted Galileo of hearsy for publicly saying the Earth orbited the Sun. A fact they were well aware of but thought public knowledge would undermine their power.

Color blind? No, you just perceive different! /ubbthreads/images/graemlins/yellowlaugh.gif Yes, I know first hand why traffic lights are that shade of green.


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## Doug Owen (Apr 30, 2004)

*Re: Do white lasers exist?*

[ QUOTE ]
*gwbaltzell said:*

Color blind? No, you just perceive different! /ubbthreads/images/graemlins/yellowlaugh.gif Yes, I know first hand why traffic lights are that shade of green. 

[/ QUOTE ]

What green? You mean the pale one at the bottom? That I can see. Gets to be fun in those places that put 'em sideways.....

Yup, at least some of them church types got a bit carried away later on, but I was talking about the dark ages....you know when folks didn't really get out of the house for a few hundred years?

Fun stuff, anyway.

Doug Owen


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## gwbaltzell (Apr 30, 2004)

*Re: Do white lasers exist?*

[ QUOTE ]
*Doug Owen said:*
Yup, at least some of them church types got a bit carried away later on, but I was talking about the dark ages....you know when folks didn't really get out of the house for a few hundred years?

Fun stuff, anyway.

Doug Owen 

[/ QUOTE ]

Oops, you're right. Don't know what this period just after the middle ages is called. Old age? /ubbthreads/images/graemlins/icon3.gif


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## HarryN (Apr 30, 2004)

*Re: Do white lasers exist?*

I will never be mistaken for someone that actually understands (or can really see) color, but I have attended enough LED conferences to have learned something from osmosis.

As my wife (the artistic side of our family) points out, the color perception from "reflection" and "emission" are quite different for similar color mixing. 

The CIE diagram is very useful for understanding the brain's perception of the effect of mixing colors "emitted" by light sources. 

The color wheels we all grew up with are to help us understand the brain's perception of mixing reflected colors, such as paints and dyes.

The two effects are similar, but not identical. The PC and printer industry spent a lot of effort to try to make things that "look one way" on your screen" to "print the same way" on paper. 

Just to make it all a little more exciting, you will notice that there are two generations of the CIE diagram - one from 1936 and a more recent one (I hope these dates are right). Both diagrams are still in use today, because they each have specific value for specific tasks. I have seen the 1936 version referenced on some Lumileds data sheets, although I am not entirely sure why they chose one vs. the other.

The other interesting aspect of the CIE is that it was developed using "average perception of color from a specific group" - I think it was age 20'ish western europeans. 

As you might expect, not everyone in the world is 20 and western european, so there are differences due to genetics and age which affect color perception. The camera film guys (whoops - gave away my age) know this very well, and have different films for different target audiences. I do not yet own a digital camera (waiting for 10 megapixel to be cheap) but this allows even more personal adjustment of color taste.

The light bulb mfg's know this just as well, and they carefully tune their product offerings for different tastes (just look at the selection of fluorescent bulbs at a large hardware store)

I have seen an article where a single laser diode emitted multiple wavelenths (in the IR telecom range) It was produced by putting multiple quantum wells (one for each wavelength) into one device. This is not "white" but the concept of one laser device producing multiple wavelenghts is feasible.

Now to do this in the visible range - quite a bit more challenging - the material science is not very happy in this range.


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## gwbaltzell (Apr 30, 2004)

*Re: Do white lasers exist?*

[ QUOTE ]
*HarryN said:*
I will never be mistaken for someone that actually understands (or can really see) color, but I have attended enough LED conferences to have learned something from osmosis.

[/ QUOTE ]

I'm beginning to wonder how many of us they are on this board. Mine is the most common. I still see the trafic light as green. About 9-12% of the male population have some variation of this genetic trait.

[ QUOTE ]
*HarryN said:*
Just to make it all a little more exciting, you will notice that there are two generations of the CIE diagram - one from 1936 and a more recent one (I hope these dates are right). Both diagrams are still in use today, because they each have specific value for specific tasks. I have seen the 1936 version referenced on some Lumileds data sheets, although I am not entirely sure why they chose one vs. the other.

The other interesting aspect of the CIE is that it was developed using "average perception of color from a specific group" - I think it was age 20'ish western europeans. 

[/ QUOTE ] 

It was based on two works:
Wright, W. D. (1928). A re-determination of the trichromatic coefficients of the spectral colours. Transactions of the Optical Society, 30, 141-164.
Guild, J. (1931). The colorimetric properties of the spectrum. Philosophical Transactions of the Royal Society of London, A230, 149-187.
and the prior:
CIE. (1926). Commission Internationale de l'Eclairage Proceedings, 1924. Cambridge: Cambridge University Press.


There have been many attempts to fix the numbers but never another massive study of a large sample of people.

CIE - Commission Internationale de l'Eclairage
CIE 1931 is the most commonly used reference.


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## Doug Owen (Apr 30, 2004)

*Re: Do white lasers exist?*

[ QUOTE ]
*gwbaltzell said:*

I'm beginning to wonder how many of us they are on this board. Mine is the most common. I still see the trafic light as green. About 9-12% of the male population have some variation of this genetic trait.



[/ QUOTE ]

Yup, it's a funny one all right. I understand the same deal, about one in ten *males* are red/green color blind. I've been told that the 'gene for normal color vision' is in the missing leg in the Y chromosome, women have two chances to get it, men only one. Makes some sense to me.

Then again, I know from personal experience that there's also a very strong correlation between color blindness and being very good looking.......

Doug Owen


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## Doug Owen (Apr 30, 2004)

*Re: Do white lasers exist?*

[ QUOTE ]
*gwbaltzell said:*

I'm beginning to wonder how many of us they are on this board. Mine is the most common. I still see the trafic light as green. About 9-12% of the male population have some variation of this genetic trait.



[/ QUOTE ]

Yup, it's a funny one all right. I understand the same deal, about one in ten *males* are red/green color blind. I've been told that the 'gene for normal color vision' is in the missing leg in the Y chromosome, women have two chances to get it, men only one. Makes some sense to me.

Then again, I know from personal experience that there's also a very strong correlation between color blindness and being very good looking.......

Doug Owen


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## Justintoxicated (Apr 30, 2004)

*Re: Do white lasers exist?*

the color blindenss gene is only found in X chromosomes, so since female is XX, if one X is dominate (not colorblind) and the other is recesive (colorblind) she will not be colorblind. In order for a women to be colorblind she has to get 2 bad X genes! But males are XY, so we either get it or we don't...and I do not know the ratio of X recessive (colorblind allel) is to the dominant one, because a women must also be the carier. It jsut gets me that women have been blamed for the sex of their children throughout history, when it actually is dependent on the MAN!


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## lasercrazy (Apr 30, 2004)

*Re: Do white lasers exist?*

Hmm that's odd, I can see green and red just fine. /ubbthreads/images/graemlins/thinking.gif /ubbthreads/images/graemlins/icon3.gif


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## gwbaltzell (Apr 30, 2004)

*Re: Do white lasers exist?*

Are you sure you can see red and green. I didn't know I was color blind until I went for my physical for the Draft (yeah, I'm old!) at age 18. Never had much trouble except I had to be in a good light to read resistors! I've just thrown together a web page that shows you a small portion of one type of test. *You cannot determine for sure if you are or are not color blind from this page!* 
Sample test.

BTW - would someone who's been tested (or female) please let me know if they can see all of these images properly.


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## Doug Owen (Apr 30, 2004)

*Re: Do white lasers exist?*

I recall that test as well. Over a hundred in the set as I recall?

I was about 16 before I was discovered to be color blind (rather than just stupid....) as well.

FWIW I can't see any numbers on the last 4.

Doug Owen


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## BB (Apr 30, 2004)

*Re: Do white lasers exist?*

The last four I can see 2,5,6,7 on a laptop with a back lit LCD set to 16 bit color. The numbers are not "obvious" but I can see them.

-Bill


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## gwbaltzell (Apr 30, 2004)

*Re: Do white lasers exist?*

Thanks, I wanted to make sure I hadn't modified the colors. I've clarified on the page that the 12 is just an example of what to look for. Everyone should be able to see it. And FWIW I can only really see one of the plates and only part of another knowing whats there. Don't recall for sure but I think these are only for M-cones (green) that are shifted toward red. The next most common is L-cones (red) that are shifted to green. This is why in the US the red traffic signal is more orange. One of the reasons why when we talk color we are talking perception. If we need to be exact we need to talk wavelength (or frequency). Also contributes to white being hard to pin down.


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## lasercrazy (May 1, 2004)

*Re: Do white lasers exist?*

I was able to read all those numbers easily. /ubbthreads/images/graemlins/smile.gif


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## hungryforlasers (May 22, 2004)

*Re: Do white lasers exist?*

If i took a red laser, a green laser, and a blue laser and went into a foggy chamber and had them intersect and observed the intersecting part. Would i see white light? /ubbthreads/images/graemlins/thinking.gif


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## PhotonWrangler (May 22, 2004)

*Re: Do white lasers exist?*

I saw a laser light Christmas show at a mall last year. They were using separate RGB lasers for the animations, and occasionally the beams would intersect and produce something resembling white light with some color fringing due to small registration errors. Since a laser is a semi-monochromatic resonant cavity, I think that this is the closest that one can get to a white laser.


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## Empath (May 22, 2004)

*Re: Do white lasers exist?*

The beam itself is invisible, even at a point of intersection. What you're seeing is the reflection off particles in it's path. It's not necessary to talk of points of intersection; just mix the colors at the point of convergence. In other words, aim the lasers at the same target, and you won't be depending on light reflected off particles at an intersection.


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## hungryforlasers (May 22, 2004)

*Re: Do white lasers exist?*

i didnt think of that...


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## PhotonWrangler (May 22, 2004)

*Re: Do white lasers exist?*

[ QUOTE ]
*Empath said:*
The beam itself is invisible, even at a point of intersection. What you're seeing is the reflection off particles in it's path. It's not necessary to talk of points of intersection; just mix the colors at the point of convergence. In other words, aim the lasers at the same target, and you won't be depending on light reflected off particles at an intersection. 

[/ QUOTE ]

That's actually what I meant - sorry for not being clear. The "white" light that I observed appeared on the target surface - a white projection screen. The RGB lasers were actually not bright enough to to see the beams themselves against the mall's fluorescent lighting.


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## PhotonWrangler (May 22, 2004)

*Re: Do white lasers exist?*

Went back and looked at some of the older posts regarding green traffic lights and "that shade" of green. I remember that traffic lights used to have a "true green" color to them, but newer ones have a slightly aqua tint to them. The LED green lights seem to hit somewhere between the original incandescent green and the newer incandescent aqua-green.

It seems to me that the lamps with the slight aqua tint appear brighter than their "Kelly Green" counterparts, so they can be seen a little farther away. I'm assuming that this is why this specific color has been chosen...?


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## BB (May 23, 2004)

*Re: Do white lasers exist?*

The reason for the blue tint (on some older LED traffic lights you can see a mix of green and blue LEDs) is because of somewhat common (usually) male red/green color blindness. The blue helps them differentiate between the red and the green signals.

-Bill


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## gwbaltzell (May 23, 2004)

*Re: Do white lasers exist?*

Signals in the US have been blue-green for as long as I've been driving at least (nearly 40 years). It was two years after I started driving that I found out I was "color blind" which is a bad term. And the red is actually a orangish red for exactly the same reason. The most common "color blindness" is having the M (green) cones peak shifted toward red. The second most common is those with L (red) cones shifted toward green. Next comes those with reduced M cone sensitivity and then reduced L cone sensitivity. Total "color blindness" is truly rare. For the first two classes of people (mostly male) its mostly an issue of solving "color puzzles" set for us by those with "normal vision". And if you haven't guessed, I chafe at those who call this a genetic defect. I think that, at least the first two classes, is no more a defect than having red hair!

Your noticing the LEDs difference may have more to due with the better adherence to the color standard. You are right that this color is near the peak of rod based (night) vision, but this has nothing to due with the use in traffic signals. If it did the green should mean stop!

BTW - overdriving Nichia blue-green at 20 mA (rated for 10 with a max of 30) shifts the color toward the peak rod sensitivity of 507 nm.


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## PhotonWrangler (May 23, 2004)

*Re: Do white lasers exist?*

Thanks for the explanations guys. I hadn't thought of color-blindness (how about "chromatically displaced sensitivity?) as a reason for this choice of color, but it makes sense.

I still notice to this day that there is an occasional "true green" filter in a traffic light, usually the older ones that don't get a lot of maintenance. Most of the ones that I've seen in recent decades are the "Kentucky Bluegrass" color. /ubbthreads/images/graemlins/smile.gif


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## gwbaltzell (May 25, 2004)

*Re: Do white lasers exist?*

Here's a chart of colors using CIE x,y notation. I haven't actual looked at these ranges on a chart but this reminds me that in Japan the green light is much more blue. Even to us who "perceive different"!


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## Quazar (May 26, 2004)

*Re: Do white lasers exist?*

White light laser with pictures.

http://www.lilaser.net/argon-krypton-medium.htm


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## bindibadgi (May 27, 2004)

*Re: Do white lasers exist?*

Very interesting thread guys. I like lasers. I studied physics at university for five years, and did as much with lasers as I could.

Because an ideal laser causes a coherent beam, it is actually impossible for it to be anything but purely monochromatic (ie a single line in the spectrum). However, there is no such thing as an ideal laser, so they all have a bit of spectral spread. That said, you can't spread it very far (at all!) before you destroy the coherence, and it simply becomes a VERY dim and pretty pathetic beam.

You can, however, as someone said, combine gases in the chamber of a gas laser so that they form 'white' light when pumped. Yes, you can buy them. I think that that is all we should care about actally - it looks white, so I think it's safe to call it white.

BTW, a laser isn't really light amplification by stumulated emission of radiation. It is actually an oscillator.

I don't think anybody would have got much funding to develop a LOSER though. I've always found that amusing.


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## BB (May 30, 2004)

*Re: Do white lasers exist?*

[ QUOTE ]
*gwbaltzell said:*
Your noticing the LEDs difference may have more to due with the better adherence to the color standard. You are right that this color is near the peak of rod based (night) vision, but this has nothing to due with the use in traffic signals. If it did the green should mean stop!

[/ QUOTE ]

I was on our honey-moon in main land China (PRC) sitting in a restaurant in a small town looking out the window at the only traffic light in town... After a while I noticed that it cycled Green-Red-Yellow-Green-Red-Yellow-... Puzzled me for awhile (there was virtually no car/truck traffic)--then I remembered a news clip I read years before about the Communist Party deciding that "Red" should not mean stop--but go!... So they resequenced all (many or some???) of the traffic lights in the country.

Our trip was was back in 1985--and I kind of remember that in large cities that the lights followed the more normal Red=Stop and Green=go convention. As near as I can tell, this was only done during the cultural revolution--I guess the city we were in was so small nobody cared enough to change it back (one of the reasons I was confused was because nobody seemed to be paying any attention to the traffic signal at all).

Red Light 

[ QUOTE ]
In Shanghai during the Cultural Revolution, the Red Guards found it unacceptable that red should mean 'stop'. They wanted the system of traffic lights changed to make red signify 'go'. Chou En-lai was allegedly willing to go along with the proposal, until his driver told him that red lights were easier to notice in the dark and in bad weather.
...
In Sao Paulo, also recently, I was surprised when my otherwise law-abiding host failed to stop at red. He explained that it was more dangerous to stop: given that the driver behind him would certainly assume that he wasn't going to stop, the risk of being hit from behind if he did was considerable. 

[/ QUOTE ]

I also noticed when traveling (~15 years ago) in Brazil the above behavior regarding red lights--The driver explained that during the day everyone followed the law--However, at night, traffic was light so that everyone just ran the red lights--but strangely enough, everyone stopped at green lights as there may be somebody running the red from another direction!

-Bill


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## PhotonWrangler (May 30, 2004)

*Re: Do white lasers exist?*

[ QUOTE ]
*bindibadgi said:*
BTW, a laser isn't really light amplification by stumulated emission of radiation. It is actually an oscillator.

I don't think anybody would have got much funding to develop a LOSER though. I've always found that amusing. 

[/ QUOTE ]

Funny! /ubbthreads/images/graemlins/yellowlaugh.gif

Yes, it is technically an oscillator with a carefully tuned resonant cavity.

Semiconductor lasers do something interesting - below lasing threshold, they act just like a regular non-coherent LED. Bring the current up to lasing threshold, and they start to become monochromatic but with lots of sidebands at adjacent frequencies. Increase the current further towards their operating limit and they become more monochromatic.

This phenomenon has aleays posed a problem when directly AM-modulating the current of the LD. The diode produces "chirp" (excessive sideband junk) because it's bouncing between it's ideal operating point and a lower, less monochromatic point, which then causes pulse dispersion at the receiving end. That's why they developed a very fast, lithium-niobate shutter that can optically modulate a CW output beam downstream of the laser itself, rather than messing with the LD's current directly. It works well and allows for pretty decent, low-distortion AM modulation of a laser (once the crystal's own artifacts are subtracted out).


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## star882 (May 30, 2004)

*Re: Do white lasers exist?*

"Semiconductor lasers do something interesting - below lasing threshold, they act just like a regular non-coherent LED. Bring the current up to lasing threshold, and they start to become monochromatic but with lots of sidebands at adjacent frequencies. Increase the current further towards their operating limit and they become more monochromatic."
Well, I have tried to develop a device to send an analog video signal over a laser beam several years back, and failed.
Ah, well, looks like I should try again with digital (extremely easy to get 115kbps, 10Mbps is easy enough, and 1Gbps just takes some high-speed design).
BTW, here's some information on how regular diode lasers work: http://britneyspears.ac/physics/fplasers/fplasers.htm (which is also linked to on Craig's laser page).


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## Doug Owen (May 31, 2004)

*Re: Do white lasers exist?*

[ QUOTE ]
*bindibadgi said:*

Because an ideal laser causes a coherent beam, it is actually impossible for it to be anything but purely monochromatic (ie a single line in the spectrum). 

You can, however, as someone said, combine gases in the chamber of a gas laser so that they form 'white' light when pumped. Yes, you can buy them. I think that that is all we should care about actally - it looks white, so I think it's safe to call it white.



[/ QUOTE ]

I still maintain that we *know* it's not really white, that is made of all colors, we have well characterized instrumentation to tell us so.

The 'it looks white, so it is' logic also leads us to the 'truth' that there is a Rock and Roll band in the radio on the kitchen table.......

Doug Owen


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## WildRice (May 31, 2004)

*Re: Do white lasers exist?*

[ QUOTE ]
*bindibadgi said:*


BTW, a laser isn't really light amplification by stumulated emission of radiation. It is actually an oscillator.

I don't think anybody would have got much funding to develop a LOSER though. I've always found that amusing. 

[/ QUOTE ]

Actually, it IS an oscillator, that causes Stimulated emission. All conventional LASERs generate laser radiation in the same way (gas(CO2),solid(Nd:YAG),and diode).
1. energy in introduced into the lasing medium
2. energy is absorbed by the atoms, and they jump to an excited and unstable state
3. the atom drops to its stable state and gives off energy in the form of a free photon of light (sparatic emission)
4. some of the photons oscillate between the two reflective surfaces.
5. when one of the photons hits an atom that is in the excited state, it forces that atom to give off its energy, in the same direction and in phase (stimulated emission)
6. one mirror is semi reflective (CO2 and YAG about 18-26% reflective, HeNe about 92-96%) and the reciprical of that is allowed to leave in the form of a LASER beam.
7. When there are more atoms being struck by lasing photons than by naturally dropping to their stable state, it is called population inversion.

At this point a beam is exiting the laser.

just thought I would toss that in.

Jeff


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## bindibadgi (May 31, 2004)

*Re: Do white lasers exist?*

[ QUOTE ]
*Doug Owen said:*
I still maintain that we *know* it's not really white, that is made of all colors, we have well characterized instrumentation to tell us so.

The 'it looks white, so it is' logic also leads us to the 'truth' that there is a Rock and Roll band in the radio on the kitchen table.......

Doug Owen 

[/ QUOTE ]

I thought there was ... /ubbthreads/images/graemlins/naughty.gif


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## Doug Owen (May 31, 2004)

*Re: Do white lasers exist?*

[ QUOTE ]
*
The 'it looks white, so it is' logic also leads us to the 'truth' that there is a Rock and Roll band in the radio on the kitchen table.......





[/ QUOTE ]
bindibadgi said:*

I thought there was ... 

[/ QUOTE ]

Utter nonsense! Just how do you explain the Western accent on a Sony radio made in Japan???

Doug Owen


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## bindibadgi (Jun 1, 2004)

*Re: Do white lasers exist?*

A kidnapping?


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## Lasernerd (Jun 2, 2004)

*Re: Do white lasers exist? *DELETED**

Post deleted by Lasernerd


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## Quazar (Jun 2, 2004)

*Re: Do white lasers exist?*

Lasernerd, your link doesn't appear to work.


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## Doug Owen (Jun 2, 2004)

*Re: Do white lasers exist?*

[ QUOTE ]
*bindibadgi said:*
A kidnapping? 

[/ QUOTE ]

Or abject lesson in why you should decline a companion's invitation to go to 'this little karioki place I know' when drinking in Tokyo......

Point well taken, anyway.

Doug Owen


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## Lasernerd (Jun 2, 2004)

*Re: Do white lasers exist?*

its a new site for me just click photos
I will be adding many more lasers in action later.
A 200mw Coherent DPSS 532 15,000$ laser guts and repair! /ubbthreads/images/graemlins/buttrock.gif


http://home.comcast.net/~keslaser/wsb/html/view.cgi-image.html--graphic.html


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## Quazar (Jun 2, 2004)

*Re: Do white lasers exist?*

Nice one Lasernerd, I see that I was visitor No2. Looking better than my site, which is why I scrapped it, new one out soon.


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## Lasernerd (Jun 2, 2004)

*Re: Do white lasers exist?*

yah my old

www.homestead.com/KESlasers is getting old.


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## comozo (Aug 31, 2007)

with photo

http://optics.org/cws/article/research/31010


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## Illum (Sep 1, 2007)

erm...reading a "sign in required" sign


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## allthatwhichis (Sep 1, 2007)

Yea, F that. I'd rather not register for something so someone can make money off my info just to read an article...  I think I have seen another article on it somewhere else though. 

Is this the solid state white light laser?

New avatar Illum?


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## stephenmadpotato (Sep 1, 2007)

Interesting eh? Can't find the wavelength for those? anyone know?


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## comozo (Sep 1, 2007)

allthatwhichis said:


> Yea, F that. I'd rather not register for something so someone can make money off my info just to read an article...  I think I have seen another article on it somewhere else though.
> 
> Is this the solid state white light laser?
> 
> New avatar Illum?



Cut the negativity. I've yet to be solicited by any company. Go ahead and sign up.


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## Illum (Sep 1, 2007)

allthatwhichis said:


> New avatar Illum?



yeah, cut from bart's "LOL" gif


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## LightForce (Sep 2, 2007)

This is microfibre laser with pulse operation. Very high power (maybe few kW) femtosecond pulses of 1064 nm laser are leaded through a few meters long optical fibre with microstructure, which causes frequency conversion from deep UV to the mid infrared. Light is continuous spectra and... coherent. 

It's not a SF, its true

D.


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## chuck (Sep 4, 2007)

Continuous spectrum AND coherent?! How is that possible?!

I'm really curious about this, as I thought this type of thing was impossible. Coherence requires the photons to move in lockstep, so how can photons of ALL frequencies in the visible spectrum move in lockstep?

I've got to be missing something.

-- Chuck Knight


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## LightForce (Sep 4, 2007)

These are femtosecond pulses, and after light frequency conversion in the microfibre only one wavelength is emitted at a given time. This wavelenght changes nonlinearly all the time and creates countinuous spectrum in the longer time period.

If there is only one wavelenght at a given time, it will be a coherent light.


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## badhorsey (Sep 4, 2007)

So... it's a persistence of vision trick rather than true white light?


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## Thujone (Sep 4, 2007)

badhorsey said:


> So... it's a persistence of vision trick



Isn't that basically true of most things?


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## Corona (Sep 4, 2007)

*Re: Do white lasers exist?/supercontinuum white light laser*

There's no theoretical difference between this thing and a multiline laser (such as argon); all the emissions are coherent because they are _stimulated emissions_. 

Coherence has nothing to do with monochromacity; coherent means the light output quanta are in phase. If all the emission components in the output spectra are excited by the same source, and there are no phase shifting optics in the emission path to affect one wavelength over another, the output will be coherent not only on a per-wavelength basis, but wholly coherent!

Pretty cool device BTW


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## Heruursciences (Sep 11, 2007)

*Re: Do white lasers exist?*

I actually have several dozen Optical Fiber Optical Parametric Oscillator (OFOPO) core fiber assemblies that go to similar white light lasers. 

Each one is a semi-rigid optical fiber that is somewhat florescent under UV light. The core is doped with some type of rare earth flourosilicate glass. They were originally pumped with high energy q-switched lasers or mega pulse lasers like Ti-sapphire. 

What happens inside is that the laser makes several standing wave patterns in the fiber this creates a virtual periodic poling effect. Then simple nonlinear effects causes harmonics and sub harmonics to be generated. Adding a selective cavity that gives feedback allows the fiber to upconvert the light into the visible range, though the most efficient tuning wavelength is allways going to be the second harmonic. Using modified broadband optics will yield a true white light LASER device. In practice, however these almost always use a prism or grating to give a TUNABLE laser source. It is a Dial a color- Any COLOR laser 

You can replicate the physics with sound instead of light by using a piece of PVC tubing, a speaker, signal generator w/ amp, microphone and an oscilloscope. Attach the speaker to one end of the PVC pipe, and a piece of PVC cap with a small hole drilled in for the microphone. Hook the signal generator to the amp then the amp to the speaker. Pick a feaquency in the center of the speaker's dynamic range, say 800HZ or so. Then attach the microphone to the o scope in AF setting. Increace the volume and at some point you will see harmonics at 1600 and 400Hz, keep increasing power and you will get more harmonics and sub harmonics. In the end if you have a high wattage speaker and a small diameter long PVC pipe you'll get virtually white noise out. If you want to make it tunable drill small holes at even intervals along the pipe, the more holes open will favor shorter frequencies, the less holes will favor longer ones.

Have fun Chris


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## npkeith (Sep 13, 2007)

*Re: Do white lasers exist?*



> White is a mixture of Red, Green and Blue.


 
No, it isn't, it is all visible colors blended together - use a prism to refract true white light (use the sun for example) and you get a spectrum (rainbow). If white were truely a blend of only red, green and blue, that is all you would see- red, green and blue. Instead you see red, orange, yellow, green, blue, indigo, and violet.


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## allthatwhichis (Sep 13, 2007)

Well, a "white laser" is actually the combination of a red, a green, and a blue laser, but natural white light contains all wavelengths. Our eyes only have red, green, and blue receptors. Not sure where I was going with this...


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## steve-o2 (Sep 18, 2007)

Here's a nice one.
Only $55,000




http://www.fianium.com/products/optical.htm


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## RDZombie (Sep 18, 2007)

steve-o2 said:


> Here's a nice one.
> Only $55,000
> 
> 
> ...



good lord i want one... only 55k hu?


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## allthatwhichis (Sep 18, 2007)

steve-o2 said:


> Here's a nice one.
> Only $55,000
> 
> 
> ...


 
That's the one... Hey Steve, welcome aboard... :welcome:


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## Heruursciences (Sep 19, 2007)

Just an interesting tidbit, did you notice in the pic showing it running that the 532nm line is the strongest?


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