Why do you need low amplitude oscillation in SNOM?

In summary, the tapered optical fibre collects light from the evanescent field and needs to oscillate while scanning a sample surface in order to lock-in detect the feedback signal. This is achieved through the use of a lock-in amplifier, which is a common technique for measuring small signals. The probe itself is a thin pipe and the oscillation helps to measure transverse forces, improving the resolution of the measurement.
  • #1
philip041
107
0
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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  • #2
I would guess that the oscillation is simply to be able to lock-in detect the feedback signal.
 
  • #3
I looked up lock-in detect but I don;t understand what you mean?
 
  • #4
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)
 
  • #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.
 
  • #6
I'm not sure but the reason it actually oscillates is to meaure transverse forces?
 

Related to Why do you need low amplitude oscillation in SNOM?

1. Why is low amplitude oscillation necessary in SNOM?

Low amplitude oscillation is necessary in SNOM (Scanning Near-field Optical Microscopy) because it allows for more precise and accurate measurements of the sample's surface. This is because the near-field signal is highly sensitive to changes in the tip-sample distance, and by using a low amplitude oscillation, the tip is able to scan the surface at a constant distance, resulting in a more reliable measurement.

2. How does low amplitude oscillation affect the resolution of SNOM?

Low amplitude oscillation is crucial for achieving high resolution in SNOM. By keeping the tip at a constant distance from the sample, it eliminates any potential blurring or distortion that may occur with larger oscillations. This leads to sharper and more detailed images of the sample's surface.

3. Can high amplitude oscillation be used in SNOM?

No, high amplitude oscillation is not suitable for use in SNOM. This is because it can cause damage to the sample's surface and it can also result in inaccurate measurements due to the tip-sample distance constantly changing. Low amplitude oscillation is necessary for obtaining reliable and precise data.

4. Is low amplitude oscillation the only factor that affects SNOM measurements?

No, there are other factors that can also affect SNOM measurements, such as the composition and properties of the sample, the type of tip used, and the environment in which the measurement is conducted. However, low amplitude oscillation is a critical factor that must be carefully controlled in order to obtain accurate and meaningful data.

5. Are there any disadvantages to using low amplitude oscillation in SNOM?

One potential disadvantage of using low amplitude oscillation in SNOM is that it can increase the measurement time. This is because the tip must scan the surface at a slower speed in order to maintain a constant distance. However, the benefits of using low amplitude oscillation, such as improved resolution and accuracy, outweigh this potential drawback.

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