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Acousto-optic effect reversable?

Discussion in 'Electronic Design' started by Jamie M, Dec 30, 2012.

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  1. Jamie M

    Jamie M Guest


    Are there any acousto optic effects that are reversible? Like instead
    of using the acoustic waves to diffract light, light could generate an
    acoustic wave? Or at least light in the crystal could
    effect an existing acoustic wave, which could be detected in the RF
    acoustic driver electronics? This is related to an AOTF, acousto-optic
    tunable filter:

    I'm looking for a device where light of varying frequency can generate
    a proportional electrical signal, either through plasmonics or
    mechanical phonon vibrations etc.

  2. Robert Macy

    Robert Macy Guest

    Back in the 80's there was a company in either Santa Clara, or
    Sunnyvale, CA [Exact name and location memory fails me, do remember
    the people were super sharp there and the principle engineer leading
    the effort was French] that made a voltage measuring instrument using
    laser light and acoustic information to infer the voltage on chips. A
    very interesting non-contact form of probing/measuring voltage IN
    atmosphere. Again from memory, the principle was based upon piezo
    effect being generated by the incidence of the laser light, but was
    not specifically a thermally related transfer.

    Another form of light to acoustic energy transfer was used to create a
    'very large' NonDestructive Testing Instrument [developed by Honeywell
    here in AZ] to inspect Beoing aricraft. The principle was to place the
    laser source near the ariplane, 'bang' the skin of the aircraft with a
    laser pulse [creating acoustic effect] and then use the same laser to
    see what happens to the skin of the aircraft. They also used the laser
    to simply 'size' the aircraft. The idea [as my understanding goes] was
    to data log the 'new' airplane then compare each data set taken during
    maintenance to that original data set. The idea was that the fuselage
    would change measurable amounts and the skin's acoustic transmission
    characteristics would change measurable amounts if the fuselage
    developed corrosion in the skin materials or developed cracks around
    rivets. [Footnote: I haven't seen the product on the market and
    assume the false positives were never resolvable, so they gave up] I
    know this isn't quite what you asked for [your question was more about
    converting light wavelength directly to acoustic energy]. In this case
    the transfer from light to acoustic was thermal. The prinicple is used
    in quite a few instruments. Probably find examples using google.
  3. Jamie M

    Jamie M Guest


    Thanks, what could be a way to convert the phonons / mechanical
    vibrations into an electrical signal to determine the spectrum of the
    light source? Also in this case the light source is very low power,
    like a sensitive CCD is required to detect the light source.

    I would like to somehow measure the phonon vibrations in the crystal,
    as well as put a reference vibration in the crystal, and read it out
    electrically or optically by measuring the crystal's vibration maybe.

    The potential application could be for a low cost miniature
    optical spectrometer, to replace the grating and CCD with a single
    crystal instead, and hopefully keep good sensitivity at the same time.

  4. Jamie M

    Jamie M Guest


    I was thinking maybe the phonon energy could be magnified locally in a
    crystal if it the crystal's geometry was shaped to focus the phonon
    waves to a given location, to create the highest pressure waves at one
    focal point, for more effective gain in the opto-acoustic conversion.
    Also if there is a different layer type the phonon waves might impact
    against and be absorbed, or turned into surface plasmons, then maybe
    that could be used to generate an electrical signal.

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