纳米粒子表面等离激元效应仿真说明

/cn/fdtd/sp_single_device_on_a_substrate.html

/cn/fdtd/sp.html

进入上面的网页下载仿真程序。

按照下面的仿真方法得到下面的图片。然后改变纳米粒子直径（宽、长），得到不同纳米粒子参数下的散射截面图。

Simulation setup

The file mie_example_3d.fsp contains an example of the Mie problem in 3D, using a total-field scattered-field source(TFSF) that surrounds a gold particle. There are two analysis groups, each of which consist of a box of power monitors: one in the total field region and one in the scattered field region. These analysis groups can be used to calculate the absorption and scattering cross sections, as well as the angular distribution of scattered radiation. In addition, 3 frequency profile monitors are added in the total field region to calculate the electric field enhancement. The total scattered field source covers a wavelength range of 300 to 600 nm.

The gold material is a copy of the "Au (Gold) - Johnson and Christy" material that is contained in the default material database. Since the default number of coefficients is not sufficient to provide a good fit to the sampled data over the source bandwidth, the maximum coefficients is set to 10. The theoretical Mie scattering cross sections (absorption and scattering) have been calculated for both the material fit and the sampled data and are stored in the

files mie_au_jc_fdtd.txt and mie_au_jc_raw.txt, respectivelty.

With the default settings (simulation span is 1x1x1 um3 and a mesh accuracy of 3, plus an override region of 5nm at the sphere) the simulation will require about 234 MB of memory.

Once the simulation is finished, mie_analysis_3d.lsf will perform the following analysis.

Absorption and Scattering cross sections

The absorption cross section (the rate at which energy is removed from the incident plane wave by absorption)is calculated by an analysis group located inside the TFSF source. The analysis group calculates the net power flow into the particle and hence the absorption cross section using the optical theorem. Similarly, the scattering cross section is calculated by an analysis group located outside the TFSF source. This group measures the net power scattered from the particle.

The above plots compare the FDTD results with the results from theory which were computed using the Gold data from the material fit. In the script file, change the name of the file from which to plot the theoretical results from mie_au_jc_fdtd.txt to mie_au_jc_raw.txt to compare the FDTD results with the results from theory that were computed using the raw Gold data. Running the script file results in the following two plots for the cross sections.

Higher accuracy results

The default settings for this simulation are designed to give reasonably accurate results while minimizing the simulation time. If higher accuracy is desired, make the following modifications. These modifications will increase the memory requirements to around 1.7 GB.