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Lorentz-Drude Model and Surface Plasma Wave
Metallic photonic materials demonstrate unique properties due to the existence of metals on electromagnetic surface waves known as surface plasmons. Surface plasmons are set to become part of the photonics revolution in which the interaction between light and matter is controlled by producing patterned structures that are periodic on the scale of the wavelength of light.
Surface plasmons open up a wealth of new possibilities for photonics because they allow the concentration and propagation of light below the usual resolution limit, thus opening up such possibilities as sub-wavelength optical components. OptiFDTD was the first software that employed the Lorentz_Drude model for the surface Plasmon and metallic layout simulation.
The Frequency domain Lorentz_Drude model is discussed in reference [1]. Figure 1 is the permittivity [1] for the noble metal gold and silver, as we can see they are very dispersive. OptiFDTD uses the time domain Lorentz_Drude model [2] (Please provide the link for our paper). Figure 2 shows the OptiFDTD simulated surface wave propagating along a Silver surface.
Figure 1 Permittivity of Gold and Silver [1]
Figure 2 OptiFDTD simulated Surface Plasmon wave propagates along the silver surface
Example 1: Beaming light from metallic aperture
Original reference:
OptiFDTD simulation results can be compared with reference [3]:
Figure 3 Bull’s eye structure of Ag film [3]
Layout in OptiFDTD
Figure 4 Side view of the layout.
Simulation results
Wave propagation effect can be observed in the simulator as shown in figure 5
Figure 5 Beam propagation through the holes
ower transmission spectrum can be detected (See figure 6). Figure 7 is the optical image from the OptiFDTD for this bull’s eyes Ag film.
Figure 6 Power transmission for normal incident wave
Figure 7 Optical images of the layout.
Example 2: Nano-scale image
In this example, a subwavelength imaging system layout using metallic nano-rods is simulated. The point sources under the nano rods compose a letter λ shape. The OptiFDTD simulation shows the silver nano-rods work as a mirror to successfully read the shape λ. The original concept can be found in reference 4.
Figure 8 Nano-rod image system [4]
