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Why do you need low amplitude oscillation in SNOM?

  1. Feb 13, 2009 #1
    Am I right in saying that a tapered optical fibre 'collects' light from evanscent field. Why would this mean it needs to oscillate as it scans a sample surface?


  2. jcsd
  3. Feb 13, 2009 #2


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    I would guess that the oscillation is simply to be able to lock-in detect the feedback signal.
  4. Feb 14, 2009 #3
    I looked up lock-in detect but I don;t understand what you mean?
  5. Feb 14, 2009 #4


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    Do you know what a lock-in amplifier is?

    Lock-in detection is -in this context- basically a technique for measuring small signals (it is to some extent THE technique because it is extremely common)
  6. Feb 16, 2009 #5
    Ah sorry. I looked up lock-in amplifier, i can see how the principle of extracting a signal from a lot of noise would be useful but I don;t get the vibrating probe thing?

    Also the probe is essentially a really thin pipe? Why How does this improve resolution?

    Come to think of it I have too many questions.. No worries.
  7. Feb 18, 2009 #6
    I'm not sure but the reason it actually oscillates is to meaure transverse forces?
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