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

  1. Mar 6, 2008 #1
    Hi:

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


    Thanks,

    Radium
     
  2. jcsd
  3. Mar 6, 2008 #2

    Andy Resnick

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    Yes- a white-light point source will give perfectly spatially coherent light.
     
  4. Mar 7, 2008 #3
    On Mar 5, 7:40=A0pm, "Green Xenon [Radium]" <gluceg...@excite.com>
    wrote:
    > Hi:
    >
    > Is it possible to generate coherent white light? This is sorta like
    > laser light except it gives out all wavelengths of visible light at
    > equal intensities at the same time. Is this possible?
    >
    > Thanks,
    >
    > Radium


    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.
     
  5. Mar 7, 2008 #4
    Green Xenon [Radium] wrote:
    > Hi:
    >
    > Is it possible to generate coherent white light? This is sorta like
    > laser light except it gives out all wavelengths of visible light at
    > equal intensities at the same time. Is this possible?


    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
     
  6. Mar 9, 2008 #5
    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 sorta like
    >laser light except it gives out all wavelengths of visible light at
    >equal intensities at the same time. Is this possible?
    >
    >
    >Thanks,
    >
    >Radium

    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
     
  7. Mar 14, 2008 #6
    Look up "Supercontinuum Generation" in Google.
    I think thats what your looking for ie. "a white laser".
     
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