Naked Science Forum
Non Life Sciences => Technology => Topic started by: shockwavemikey65 on 26/07/2009 06:21:03
-
As we can now produce almost any light color for laser beams. Why have I not seen any white lasers or black lasers or even brown lasers?? Is it even possible to produce these colors in a laser diode?
blue [ Invalid Attachment ]
green [ Invalid Attachment ]
red [ Invalid Attachment ]
purple [ Invalid Attachment ]
orange [ Invalid Attachment ]
yellow [ Invalid Attachment ]
-
How on earth can you have a black laser!? [???]
-
Specifically designed laser diodes produce light at one wavelength only; that is one colour only. The spectrum is very narrow. LEDs are similar but the construction is simpler and the spectrum is wider, but is still quite narrow and just one colour. Other colours can be created by using two or more LEDs of different wavelengths or by using a phosphor to absorb the monochromatic light and re-emit it over a different wavelength band (like in a fluorescent tube).
The lasers you are referring to are high powered (pumped) lasers and the wavelength of light produced depends on their construction and the materials used. These lasers can also produce a single colour and each laser will only work in a very narrow wavelength band. It is a prime feature of all lasers that they can only be designed for one wavelength (or colour). I would suppose you could have different coloured lasers (say R, G and B) accurately aligned to each other to give the impression of a single beam that could produce any colour by changing the relative intensity of the lasers.
What we observe as a colour is because the human eye has receptors that respond to different wavelengths. A TV only uses Red, Green and Blue but gives the impression that you can see Orange, Yellow and Violet too. This is because the receptors' bands overlap quite a lot so that light at a wavelength between Red and Green stimulates Red and Green receptors and the brain interprets this in the same way as if it were a single wavelength between Red and Green. What we see as a spectrum of colours is made up of the colours R, G and B.
As Chemistry4me implied, you can't have black as black is the absence of light. Well I suppose you could switch the light source off and, if there were no other light sources, you would have black. But you cannot have a beam which somehow negates the presence of other light sources in the way you mean.
-
Arguably, brown white and black are not colours. What wavelengths do they correspond to?
You can get a laser in any colour of the rainbow, brown black and white don't apear in the rainbow or the laser manufacturer's catalogue.
Technically, with a sufficiently short pulse, you could get something that aproximates to white light .
-
Ultraviolet light (invisible to humans) is sometimes referred to as "black light (http://en.wikipedia.org/wiki/Black_light)".
Ultraviolet lasers exist.
-
As we can now produce almost any light color for laser beams. Why have I not seen any white lasers or black lasers or even brown lasers?? Is it even possible to produce these colors in a laser diode?
About the black laser, you could replace the "photons" with the "darkons" [;D]
Of course it's impossible, black is the absence of light (the fact UV or others radiations are non-visible, don't make them a "black beam").
-
As we can now produce almost any light color for laser beams. Why have I not seen any white lasers or black lasers or even brown lasers?? Is it even possible to produce these colors in a laser diode?
Guys, about black lasers or "darkons", [:D]...
Is it possible to create a laser that will produce a destructive interference wave pattern, so that it will dim out another laser?
-
I have already produced a black laser.
Trouble is, when I took it to the patent office, no bugger could see it, so they told me to take my black light and shove it where the sun don't shine!
I did, now I can't bloody see it myself!
-
So that's your dark secret! I should have seen it coming!
-
And I should have seen that coming, but with all this black light around, I can't see a bleeding thing!
-
Guys, about black lasers or "darkons", [:D]...
Is it possible to create a laser that will produce a destructive interference wave pattern, so that it will dim out another laser?
It will dim it in some regions of space but it will brighten it in other regions; energy remain conserved.
-
So.. What would happen if you point a ultraviolet laser at a andersite crystal? ???
-
What is andersite ?
-
Is it even possible to produce these colors in a laser diode?
A laser beam is defined as being a single wavelength coherent light. So a laser can produce pure "rainbow" colors, but not "mixed" colors like brown, cyan or magenta.
In practice, lasers do not produce exactly one wavelength - they typically produce several closely-spaced wavelengths, which are a submultiple of the length of the laser cavity. But these wavelengths are still so close together that the human eye cannot distinguish them.
Where high spectral purity is important (eg long-distance telecommunications), you can couple a second cavity so that the selected wavelength is enhanced, and the unwanted wavelengths suppressed.
I work a lot with infra-red lasers, and these are not visible to the naked eye, nor would an ultraviolet laser be visible in a dark room. So in principle, these could be called "black" lasers, ie the absence of visible light.
I have visited an IMAX laser theater, where they mix light from red, green and blue lasers to produce a full range of visible colors, including white and brown.
Is it possible to create a laser that will produce a destructive interference wave pattern, so that it will dim out another laser?
Yes, two lasers of the same wavelength will interfere constructively and destructively in different places.
Even one laser (like a common laser pointer) will interfere with itself - that speckled effect when you shine it on a painted wall is the interference effects of the laser beam interacting with itself to produce destructive interference on your eyeball. Fortunately, it is only destructive to the light, not your eyeball.
What is andersite ?
Typo: It is a mineral https://en.wikipedia.org/wiki/Andesite
What would happen if you point a ultraviolet laser at a andersite crystal?
This article will probably tell you, but it is behind a paywall:
http://www.sciencedirect.com/science/article/pii/0019103578901264?via%3Dihub
-
What is andersite ?
Is a rock produce after the extraction of radioactive elements like uranium. You can find online. Andersonite, wrong name, my bad! It glows under "black" light, so i was thinking what would happen passing a laser through the crystal rock. Only normal refraction? Nothing peculiar? That was my question.
evan_au thanks!
-
The Spectra Physics lasers with which I used to work could be made to produce a range of colours by adjusting the angle of the external mirrors.
-
A far infra-red laser is also invisible to the human eye, but can be seen by the camera of your mobile phone.