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app:irsnom [2018/02/02 16:23] pklapetek |
app:irsnom [2018/09/05 16:05] (current) pklapetek |
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| Using FDTD we can simulate the performance of different probes manufactured for infrared SNOM measurements. | Using FDTD we can simulate the performance of different probes manufactured for infrared SNOM measurements. | ||
| - | /TODO: update this and add the last datasets/ | + | First aspect to handle if we want to work in mid-infrared are the optical parameters. |
| + | Using databases as [[http://refractiveindex.info|Refractiveindex.INFO]] we can get the right values of the optical constants for wide range of wavelengths. If we want to use the dispersive metal models, like those discussed in [[fdtd:materials|Media]] section, we need to adapt also their parameters. Below we can see and example of how the literature parameters fitted for 400-800 nm wavelength range might deviate from experimental data if we are in infrared region. | ||
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| + | {{ :app:firesult_visible_extended.png?500 |}} | ||
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| + | The solution is to fit a suitable dielectic function model to the database data and use this in the calculation. For metals in infrared a Drude model is typically recommended. This can be handled via the PLRC and ADE algorithm, for example by setting the strength of critical points to zero in any of the Drude+CP algorithms. The dielectric function fitted to a particular wavelength range, here around 10 microns, looks already much better: | ||
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| + | {{ :app:fitresult_eps1_8to12.png?500 |}} | ||
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| + | As an example, typical fit results for this material and wavelength region were (in the GSvit input format including the dispersive model type) | ||
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| + | ''5 1 0 1.232e+16 5.58e+13 0 -1.09115 4.20737e15 2.35409e15 0 -1.18299 3.88123e15 0.452005e15 | ||
| + | ''. | ||
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| + | Note that in fact only Drude terms are used in this case, as the weights of the CP terms were here set to zero. | ||
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| + | //To be completed.// | ||
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app/irsnom.1517585016.txt.gz · Last modified: 2018/02/02 16:23 by pklapetek
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