Is there such a thing as in-phase and coherent white light?

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Discussion Overview

The discussion centers around the possibility of generating coherent white light, akin to laser light but encompassing all visible wavelengths at equal intensities simultaneously. Participants explore theoretical and practical aspects of this concept, including potential methods and limitations.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants propose that a white-light point source can produce perfectly spatially coherent light.
  • One participant discusses the potential of high-speed pulsed lasers, like the Ti:sapphire laser, to generate very short pulses that could approximate white light, suggesting that such a device could emit a spectrum with many narrow band peaks.
  • Another participant suggests mixing light from three lasers to achieve the perception of white light, based on the eye's sensitivity to red, green, and blue wavelengths.
  • A different viewpoint argues against the possibility of coherent white light, stating that if every frequency were in phase only with itself, it would not possess the qualities expected of coherent light.
  • One participant mentions "Supercontinuum Generation" as a potential method for achieving a "white laser," implying a connection to the original question.

Areas of Agreement / Disagreement

Participants express differing opinions on the feasibility of generating coherent white light, with no consensus reached on the topic. Multiple competing views remain regarding the methods and definitions involved.

Contextual Notes

Some claims depend on specific definitions of coherence and the nature of light sources, while the discussion includes unresolved technical details about the generation of coherent light across all visible wavelengths.

Green Xenon [Radium]
Hi:

Is it possible to generate coherent white light? This is sort of like
laser light except it gives out all wavelengths of visible light at
equal intensities at the same time. Is this possible?Thanks,

Radium
 
Science news on Phys.org
Yes- a white-light point source will give perfectly spatially coherent light.
 
On Mar 5, 7:40=A0pm, "Green Xenon [Radium]" <gluceg...@excite.com>
wrote:
> Hi:
>
> Is it possible to generate coherent white light? This is sort of like
> laser light except it gives out all wavelengths of visible light at
> equal intensities at the same time. Is this possible?
>
> Thanks,
>
> Radium[/color]

It is possible, in principle, in a sense. There are high speed pulsed
lasers available now, such as the Ti:sapphire laser. This laser
generates very short pulses of light, about 10E-15 seconds long or
less, and thus has a spectral width of about 10E15 Hz. The output
from these lasers is a very brief burst of EM radiation, just a few
cycles long, that repeats at about 80 MHz. If a similar device could
be built that would emit something closer to a train of delta
functions, then the emitted spectrum could approximate white light.
If such an output was analyzed with a spectrometer, one would find
many many narrow band peaks spaced at 1/(the pulse repetition rate).
The number of these peaks would be inversely proportional to the width
of the individual delta function pulses.

This beam could be considered coherent since the EM waveform repeats
periodically. If the repetition rate was 300 mHz, then the
fundamental waveform would repeat every meter or so, thus you could
get interference between beams that differed in path length by n
meters, where n is any integer.

I know of no devices that can do quite this at present.

Rich L.
 
Green Xenon [Radium] wrote:
> Hi:
>
> Is it possible to generate coherent white light? This is sort of like
> laser light except it gives out all wavelengths of visible light at
> equal intensities at the same time. Is this possible?[/color]

Since the eye only perceives red, green and blue that's all you need.
So, yes - just mix the light from three lasers.

FFF
Dirk

http://www.transcendence.me.uk/ - Transcendence UK
Remote Viewing classes in London
 
Last edited by a moderator:
On Thu, 6 Mar 2008 01:40:24 +0000 (UTC), "Green Xenon [Radium]"
<glucegen1@excite.com> wrote:

>Hi:
>
>Is it possible to generate coherent white light? This is sort of like
>laser light except it gives out all wavelengths of visible light at
>equal intensities at the same time. Is this possible?
>
>
>Thanks,
>
>Radium[/color]
No. Assume the contrary. Then every frequency in each zero bandwidth
bin in the continuum would be "in phase", but only with itself, and
the zero bandwidth would equate to zero energy.
It doesn't seem such light would have any of the qualities expected of
coherent light.
Just an amateur opinion.
John Polasek
 
Look up "Supercontinuum Generation" in Google.
I think that's what your looking for ie. "a white laser".
 

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