For light incident on metallic nanoparticles, resonant interactions with the electronic charge density
near the surface, called surface plasmon polaritons, play an important role in determining the
efficiency with which incident light is absorbed and scattered. In this example, we determine, for a
silver nanowire with a diameter of 50 nm, the freqeuncy dependence of the surface plasmon polariton
resonance and calculate the
scattering, extinction and absorption cross sections as a function of wavelength near this
resonance.
|
|
|
|
"Our experience using parallel FDTD Solutions on a dual quad core Xeon Processor workstation has been
fantastic! It greatly helped us in decreasing processing time for our plasmon-enhanced fluorescence
calculations and hence greatly increased our computational throughput. We are extremely satisfied
with the parallel version of FDTD Solutions and would recommend it to the scientific community at large.
M. Chowdhury, University of Maryland
|
|
|
Step 1: Construct the nanoparticle project in the layout editor and simulate
|
 |
The layout editor shows the position of the simulation objects. Different classes of
objects (physical primitives, radiation sources, monitors) are color coded for easy identification.
Objects can be moved and resized easily with the mouse.
- blue region denotes silver nanoparticle
- orange regions show the extents of the computation area, bounded by absorbing (PML) boundary conditions
- yellow lines show transmission monitors
- the shaded region shows the total-field scattered-field (TFSF) source
- window at the bottom shows the script window, where customized commands and analysis can be performed
|
Step 2: Gain understanding - watch the movie
|
|
Movies showing the simulation dynamics are easily created, and provide information that
facilitates understanding of device behavior.
- for broadband excitation, the source frequency is chirped
- watch the movie: note the inner region contains the total field (incident+scattered); the outer region contains only the scattered field
- note during the middle of the movie scattering occurs but at the start and end very little scattering happens
|
Step 3: Measure the time response
|
|
Integrated analysis routines facilitate data analysis and visualization. Choose from drop-down menus
which monitor you wish to analyze, and the field component of interest.
- by selecting the time monitor and the magnetic field component in the z-direction from pull-down
menus, a plot of the time signal is easily produced
- note the strong scattering that occurs during the middle of the time pulse, as observed previously
within the movie
|
Step 4: Measuring the scattering, absorption, and extinction cross sections
|
|
The built-in scripting environment can be used to perform parameter sweeps, customize analysis, or
automate both simulation and analysis to optimize device performance. Easily define
new functions to avoid having to export simulation data for post-processing.
- define functions that sum power flowing out the scattered region as a function
of frequency; do the same with the total field
- appropriate scaling produces the scattering and absorption cross
section for the silver nanoparticle
|
|
- using the newly created scattering and absorption cross-section functions, generate a plot of the
extinction cross section by entering a single line into the scripting window
|
Step 5: Determining the field profiles on and off resonance
|
|
Use frequency-domain monitors to record the steady-state / continuous-wave response of interest.
Multiple steady- state responses can be determined in a single simulation, saving time over
frequency-based solution techniques.
- set an frequency-domain are monitor to the peak of the cross section curves, and generate a plot of
the steady-state radiation distribution around 340nm
- note the strong field enhancement along the edge of the silver nanoparticle
|
|
- set another frequency-domain area monitor off resonance, and compare the differences in the
field profiles between on- and off-resonance excitation
- both field profile plots can be constructed from the simulation data of a single simulation, saving
time
|
Home
Applications library
