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Strange electric-optical unit (a.u.)

  1. Oct 28, 2007 #1
    Hello to all,
    I'm reading one article about LT (low temperature) GaAs MSM (metal-semiconductor-metal) photo switches that has application in ultrafast sampling.
    Basically, there is one photoswitch in series with hold capacitor. Special test is performed which gives electro-optical signal depending on time. Problem is in the way how plot is given in the terms of units. On x axis is time in ps, but on y axis in signal given in a.u. I know that a.u.means atomic unit, but this is not it, it can't be. I cannot find any other meaning of a.u.
    Do you know what this could mean?

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  3. Oct 28, 2007 #2


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    a.u. can also mean arbitrary units.
    I suspect they are measuring the signal using an instrument where they can't easily relate the absolute value of the signal to the reading; i.e. only the relative value of the signal is important.

    This is quite common in experimental physics; in many experiments it is almost impossible to "calibrate" the instruments which is fine as long as one is only interested in how a signal changes over time.
  4. Oct 28, 2007 #3

    Claude Bile

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    I wouldn't say so much as impossible as irrelevant in a linear system since the absolute readings scale with the power of your source anyway.

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