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app:ters [2018/01/31 08:28] pklapetek |
app:ters [2018/02/01 12:09] pklapetek |
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| ===== TERS field enhancement ===== | ===== TERS field enhancement ===== | ||
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| + | Tip Enhanced Raman Microscopy is, besides [[app:sers|SERS]] another approach how to locally enhance the Raman scattering signal. | ||
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| + | There are the few different effects that we can observe when illuminating a nanoscale metallic structure. First of all, we can observe effect of spectral properties of the particular metal from which the structure is formed. Even the simplest possible quantity observed on metals in everyday life - its excellent reflectivity - is material dependent and the different appearance of different metals is its consequence. This can be handled via FDTD easily as there are many different algorithms enabling us to parametrize the spectral dependence of optical properties of metal and use them in the calculation. These algorithms also hide fact that the propagation of light through metal described only by its complex permittivity can’t be handled easily via conventional grid spacing and time steps. An example of calculated metal reflectivity via FDTD for different metals and algorithms is shown in section [[fdtd:materials|Media]]. | ||
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| + | The second remarkeable effects is the antenna effect. When we prepare a structure with size that is comparable to the wavelength of the illuminating light, we form an antenna similarily like e.g. in radio communications. This leads to significant local enhancement of the electromagnetic field around the antenna due to resonance effects. Here we meet the enhancement, which is so important for TERS probes, for the first time. | ||
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| + | The different spectral properties of different metals also cause differences of behavior of the nano-objects, so both these effects act together. In Fig. 2, an example of isolated nano-antenna is given and results of local field enhancement at antenna apex for three different antenna lengths and three different metals is given. | ||
app/ters.txt · Last modified: 2018/02/02 10:32 by pklapetek
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