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Author Topic: Can I make myself a white laser?  (Read 12619 times)

Offline Geezer

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Re: Can I make myself a white laser?
« Reply #25 on: 17/07/2012 00:45:07 »
Thanks! I'm not sure my Mickey and Donald calculator will let me calculate the energy in a photon with a wavelength of one Planck :)
 

Offline yor_on

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Re: Can I make myself a white laser?
« Reply #26 on: 17/07/2012 23:38:29 »
It's weird, to me a light quanta is a 'energy' (and a momentum). And the question I'm wondering about is if those energies are continuous or if they come in steps. And I don't know? I would, and will, assume that it (a light quanta's energy) can have any value, just because it's 'energy', although when we involve matter emitting radiation they will have defined energies?

It's weird, and I don't know if my assumption is right. The light quanta's we observe is as far as I know always produced in interactions with matter, without matter no interactions.
« Last Edit: 17/07/2012 23:42:42 by yor_on »
 

Offline Geezer

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Re: Can I make myself a white laser?
« Reply #27 on: 18/07/2012 01:04:53 »

The light quanta's we observe is as far as I know always produced in interactions with matter, without matter no interactions.


Not necessarily. Radio waves are a form of "light" that is produced without interaction with matter. You can even receive light with a very small antenna. I don't think there is a fundamental reason that makes it impossible to produce light of an arbitrary wavelength with an antenna.
 

Offline yor_on

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Re: Can I make myself a white laser?
« Reply #28 on: 18/07/2012 01:39:30 »
Not sure I follow there Geezer?

Are you thinking of the question itself?
If 'energy' is 'quantified' and then using radio waves to consider it?
 

Offline JP

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Re: Can I make myself a white laser?
« Reply #29 on: 18/07/2012 02:21:36 »
Geezer, do you mean that radio waves don't come from atomic transitions?  As far as I know, you have to have a moving current to produce them (and indeed all EM radiation should have moving charges as a source).

Yor_on, photons are defined as having one particular energy and momentum (and spin/polarization).  The field emitted by a moving electron doesn't have to only consist of one photon, however.  A photon oscillating on an antenna doesn't have to emit only one energy of photons: it can emit a spectrum of them. 
 

Offline yor_on

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Re: Can I make myself a white laser?
« Reply #30 on: 18/07/2012 02:48:06 »
Yes JP :)
What I'm thinking of here is actually what 'fields' might be, and using radiation as a base. Then it becomes interesting if the 'fields' flicker, sort of, energy wise :) The quantums may be quantums, or light quanta', but the 'energy' they contain, can it be a smooth phenomena in itself? Meaning that its 'energy' doesn't come in steps until it 'interacts' with matter, if that now makes sense?

A weird question I guess :) but it's in some way about dimensions we can measure in and, what 'degrees of freedom' something can have? As if you consider 'energy' as a smooth field permeating everything, quantizing in interactions.
 

Offline Geezer

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Re: Can I make myself a white laser?
« Reply #31 on: 18/07/2012 03:51:46 »
Not sure I follow there Geezer?

Are you thinking of the question itself?
If 'energy' is 'quantified' and then using radio waves to consider it?

Radio signals can be of any arbitrary frequency, but I think light sources are limited in the specific frequencies that they produce (that may be baloney!). So, I was suggesting that it should be possible to produce light of any frequency with an antenna.
 

Offline Geezer

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Re: Can I make myself a white laser?
« Reply #32 on: 18/07/2012 03:58:15 »

Geezer, do you mean that radio waves don't come from atomic transitions?  As far as I know, you have to have a moving current to produce them (and indeed all EM radiation should have moving charges as a source).


Electron current is certainly required in an antenna, but I don't think the frequency of the current is a function of atomic transitions - or is it?
 

Offline yor_on

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Re: Can I make myself a white laser?
« Reply #33 on: 18/07/2012 11:54:07 »

Radio signals can be of any arbitrary frequency, but I think light sources are limited in the specific frequencies that they produce (that may be baloney!). So, I was suggesting that it should be possible to produce light of any frequency with an antenna.

I see :)

Yeah, you got a point there. So maybe 'energy' is a smooth phenomena?
It's been bothering me for some while, dimensions. Also called degrees of freedom. Actually I like 'degrees of freedom' better as a description than dimensions as it takes away a little of the mystery/fog a 'dimension' begets when people throw it around in SF etc :)

And then we have 'energy', as an expression of transformations. Not to be touched or hold in your hand otherwise, except when used as a description of something transforming as I think of it, but I'm not sure..

If we consider the Higgs field the Higgs boson is a 'excitation' of that field as I understands it. And if you then assume that the field as such is everywhere, always there, with our arrow allowing for interactions to happen at the proper 'energies'?

Just put it together, 'dimensions' or degrees of freedom and 'fields'. But it's important to me to remember that you need a arrow of time for a excitation to be defined.
 

Offline JP

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Re: Can I make myself a white laser?
« Reply #34 on: 18/07/2012 12:16:11 »

Geezer, do you mean that radio waves don't come from atomic transitions?  As far as I know, you have to have a moving current to produce them (and indeed all EM radiation should have moving charges as a source).


Electron current is certainly required in an antenna, but I don't think the frequency of the current is a function of atomic transitions - or is it?

Yes.  That's what I mean.  Moving electrons generate EM radiation.  Moving can include atomic transitions, but it can also include free electrons flowing (as in radio antenna).
 

Offline JP

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Re: Can I make myself a white laser?
« Reply #35 on: 18/07/2012 12:18:00 »

Radio signals can be of any arbitrary frequency, but I think light sources are limited in the specific frequencies that they produce (that may be baloney!). So, I was suggesting that it should be possible to produce light of any frequency with an antenna.

I see :)

Yeah, you got a point there. So maybe 'energy' is a smooth phenomena?
It's been bothering me for some while, dimensions. Also called degrees of freedom. Actually I like 'degrees of freedom' better as a description than dimensions as it takes away a little of the mystery/fog a 'dimension' begets when people throw it around in SF etc :)

And then we have 'energy', as an expression of transformations. Not to be touched or hold in your hand otherwise, except when used as a description of something transforming as I think of it, but I'm not sure..

If we consider the Higgs field the Higgs boson is a 'excitation' of that field as I understands it. And if you then assume that the field as such is everywhere, always there, with our arrow allowing for interactions to happen at the proper 'energies'?

Just put it together, 'dimensions' or degrees of freedom and 'fields'. But it's important to me to remember that you need a arrow of time for a excitation to be defined.
Not sure I follow there Geezer?

Are you thinking of the question itself?
If 'energy' is 'quantified' and then using radio waves to consider it?

Radio signals can be of any arbitrary frequency, but I think light sources are limited in the specific frequencies that they produce (that may be baloney!). So, I was suggesting that it should be possible to produce light of any frequency with an antenna.

That's baloney!  :)

Thermal radiation includes light that has a broad spectrum because electrons can move in other ways than atomic transitions (or other quantized phenomena). 
 

Offline JP

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Re: Can I make myself a white laser?
« Reply #36 on: 18/07/2012 12:18:33 »
Quote
Radio signals can be of any arbitrary frequency, but I think light sources are limited in the specific frequencies that they produce (that may be baloney!). So, I was suggesting that it should be possible to produce light of any frequency with an antenna.

That's baloney!  :)

Thermal radiation includes light that has a broad spectrum because electrons can move in other ways than atomic transitions (or other quantized phenomena). 
 

Offline yor_on

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Re: Can I make myself a white laser?
« Reply #37 on: 18/07/2012 12:22:40 »
What I was thinking of there was Geezers thought about frequencies and that they can be split infinitely? This is a very weird thought JP :) but ...

The point to me is what those 'degrees of freedom' implies. If you imagine a 'field' that only exist to us at some 'energy' of interaction, but still is there, what is its degree of freedom? One can define it such as we have four dimensions. Three that is the room and one that is the arrow, but a field seems somehow to have another degree of freedom to me, now ignoring our arrow? Because if you do ignore it then this field is static, still existing. Add a arrow and some rules and you get a orderly procession.

Like all 'energy' there is actually has a life of its own :) if you see how I think, and that's indeed a pretty weird thought.
 

Offline yor_on

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Re: Can I make myself a white laser?
« Reply #38 on: 18/07/2012 12:43:58 »
Maybe a better question would be, ignoring a arrow, how many degrees of freedom can exist? As I think only one, and that one is what I call 'static'.
 

Offline JP

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Re: Can I make myself a white laser?
« Reply #39 on: 18/07/2012 14:05:09 »
For a single photon you have: momentum and spin as free variables.  (Momentum determines energy since E2=p2 for massless particles.)  A general field can always be decomposed into photons, and I believe the number of degrees of freedom you have will be roughly proportional to the number of photons making up that field (multiplied by 4, since you can specify 3 momentum components over space and spin/polarization).

Dealing with photons without understanding the fundamentals is overly confusing, however.

The same principle holds for sound.  A single frequency of sound technically goes on forever and has only one degree of freedom: frequency.  A general sound wave has much more variation over space and time than a single note.  It turns out (http://en.wikipedia.org/wiki/Fourier_analysis) that you can write any general sound wave as the sum of a bunch of single-frequency waves.  If you want to create a general sound wave, you can specify how it varies over space and time, or you can alternatively tell me how much of each frequency component to add together.  Both are legitimate and equivalent ways of writing the wave.  The same holds true for photons/light: you can specify the wave or you can specify how much of different quantum photon states to add together to generate that wave.
 

Offline Geezer

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Re: Can I make myself a white laser?
« Reply #40 on: 18/07/2012 16:57:58 »
What was the question again?  :)
 

Offline yor_on

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Re: Can I make myself a white laser?
« Reply #41 on: 18/07/2012 17:24:02 »
That is assuming 'virtuality' too JP? How would you handle it if you decided it was indeterministic instead? To me the difference is one between something 'there' as a 'particle' versus something representing a probability. If I want it to be 'virtual' I assume that I also have to allow it a 'time', even if unmeasurable?
=

A field defined by Higgs is not there at all, if we by that mean that it is measurable by us, well, as long as you don't see inertia/gravity as that field? As far as I understand inertia/gravity then should be a result of it, if one trust Higgs fields. And, if you can't measure it, still expecting it to exist, do you define that as photons? Seems a big difference between measurable photons and this to me. I'm not saying it isn't bosons though.
« Last Edit: 18/07/2012 17:30:53 by yor_on »
 

Offline yor_on

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Re: Can I make myself a white laser?
« Reply #42 on: 18/07/2012 18:27:21 »
It is tricky.

I throw a ball at some other person. I feel a force pushing me backwards as I throw, I see the ball travel and then get caught by the other person, that now will feel a force transmitted as he catches it. But what transmitted that force? Photons? Is all fields then consisting of photons?

Then we have the definition of something, easily able to superimpose, as being 'scalar', now having definite positions in SpaceTime, and they should need too, shouldn't they? If we assume the 'force carriers' to consist of photons making up a field?

I'm not sure I understand what a field is.
 

Offline yor_on

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Re: Can I make myself a white laser?
« Reply #43 on: 18/07/2012 18:35:31 »
And to up it, it must also be observer  dependent if relativity is correct. And that should mean that what you and I measure will differ, so to summarize, a scalar, but observer dependent 'field'. This is assuming that LorentzFitzGerald contractions exist naturally. That time dilations exist we already know and their complementary should be a LorentzFitzGerald contraction. I would be surprised if it wasn't.
« Last Edit: 18/07/2012 18:38:33 by yor_on »
 

Offline evan_au

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Re: Can I make myself a white laser?
« Reply #44 on: 20/07/2012 13:26:32 »
If you wanted to make a projection TV, you could modulate the output of red, green and blue light sources and project it in a raster pattern, forming a TV image. These light sources could be lasers.

By combining all three colours in different combinations, you can generate most of the colours that the human eye can see, including white (just like a normal TV).

But the sum of 3 coherent lasers of different wavelengths is not coherent white light, so it's not really a "white laser".
 

Offline JP

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Re: Can I make myself a white laser?
« Reply #45 on: 20/07/2012 14:46:22 »
I don't know if anyone has commercialized laser displays, but various organizations have worked on the technology.  The idea works exactly as you say: red, green and blue lasers are combined and scanned across a display, where the amount of each at each pixel determines the color seen.  (http://en.wikipedia.org/wiki/Laser_video_display)
 

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Re: Can I make myself a white laser?
« Reply #45 on: 20/07/2012 14:46:22 »

 

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