Why do you need low amplitude oscillation in SNOM?

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    Amplitude Oscillation
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Discussion Overview

The discussion revolves around the necessity of low amplitude oscillation in Scanning Near-field Optical Microscopy (SNOM). Participants explore the relationship between the oscillation of a tapered optical fiber and its ability to collect light from evanescent fields while scanning a sample surface.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification, Debate/contested

Main Points Raised

  • One participant questions the need for oscillation in the context of a tapered optical fiber collecting light from evanescent fields.
  • Another suggests that oscillation is necessary for lock-in detection of the feedback signal.
  • A participant seeks clarification on the concept of lock-in detection and its relevance to the discussion.
  • There is a mention of lock-in amplifiers as a technique for measuring small signals amidst noise, indicating its commonality in the field.
  • One participant expresses confusion about the vibrating probe and its role, questioning how the thinness of the probe improves resolution.
  • Another participant proposes that oscillation may be related to measuring transverse forces.

Areas of Agreement / Disagreement

The discussion contains multiple competing views and remains unresolved regarding the specific reasons for the need for low amplitude oscillation in SNOM.

Contextual Notes

Participants express uncertainty about the principles of lock-in detection and the mechanics of the vibrating probe, indicating a need for further clarification on these topics.

philip041
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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?

Cheers!

philip
 
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I would guess that the oscillation is simply to be able to lock-in detect the feedback signal.
 
I looked up lock-in detect but I don;t understand what you mean?
 
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)
 
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.
 
I'm not sure but the reason it actually oscillates is to meaure transverse forces?
 

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