Using the methods covered in this course, you can simulate devices used in a broad range
of areas including nanophotonics, sensing, display, photonic integrated circuits, defect
detection, and metamaterials.
Here are some practical examples of what can be simulated,
and in the following slides we’ll briefly touch on each of these examples and talk about
the types of results that we can collect for each one.
Photonic integrated circuit technology is a growing application area.
On-chip photonic components such as waveguides, couplers, ring resonators, modulators, and
detectors can be characterized using FDTD Solutions, and the S-parameters of these components
which characterize transmission and reflection of the component can then be exported to a
circuit-level simulation software like INTERCONNECT where the system-level design can take place.
The Bragg waveguide is one example of a photonic integrated circuit component that can be used
a wavelength selective mirror or filter.
The Bragg waveguide shown here is a silicon waveguide with 40 nm periodic etching.
We can use FDTD Solutions to simulate a unit cell of the waveguide with periodic boundaries
to characterize the bandwidth of the device.
It’s also possible to account for smoothing of the waveguide corrugation due to the lithography
fabrication step by generating the structure shape given the fabrication process parameters,
or by importing the shape of the fabricated structure from an SEM image.
Here we can see the simulated operating bandwidth of the device matches well with the measured
CMOS image sensors used to detect light have pixel sizes on the micron scale.
This is a cross section of one pixel of a CMOS image sensor where you can see that the
structure is made up of many components including microlenses, color filters, metal vias and
The materials of the structure are dispersive, requiring good material fits for broadband
We are able to simulate optical collection efficiency for different incident angles of
light, as well as quantities like the cross talk and point spread function which characterize
light incident on one pixel which gets detected by neighboring pixels.
In the online Knowledge base examples we also show how to optimize the radius of curvature
and position of microlenses.
OLEDs used for displays such as cell phone screens are composed of a multi-layered thin
film structure where spontaneous emission occurs in an active layer sandwiched by a
cathode and anode.
The structure of the layers and any micro pattering added into the structure like the
photonic crystal lattice structure shown here can have a large influence on the emission
efficiency and the angular emission pattern by scattering light at the layer interfaces.
Using FDTD Solutions, we can simulate the light extraction efficiency and emission pattern
from the device for different designs.
We can also simulate thin conductive films like graphene.
In this graphene switch example, a strip of graphene acts as a waveguide.
A bias voltage can be applied along one portion of the waveguide which sets the conductivity
of the graphene to act as a switch.
Here you can see the fields along the waveguide in the on an off state of the switch.
Other active devices like electro-optic modulators and thermal tuning of waveguides can also
be simulated using FDTD Solutions in conjunction with the charge transport and heat transport
solvers in DEVICE.
Another common application is the simulation of plasmonic effects.
One example of a plasmonic device is a plasmonic lens such as this bullseye aperture.
Here, a thin silver film is etched with a pattern of concentric circles with a hole
in the center.
The circular grating pattern of the etching enhances transmission through the central
hole in the film as it generates surface plasmon modes, and we can simulate the angular distribution
and enhancement of the light transmitted through the lens due to the applied patterning.
Optical inspection is commonly used to detect defects on wafers by illuminating and analyzing
the reflected scattering from a surface.
We can use simulations to characterize the scattering for different illumination and
collection modes of the system to optimize parameters of the imaging system to maximize
the measured intensity of scattering from a defect.
The final example here is a microbolometer which is used for thermal imaging where the
pixels each have a periodic array of structures that absorb power at a specific wavelength
range, and each pixel also has a thermistor which has a resistance that changes with temperature.
We can use FDTD Solutions to design the structure geometry to achieve the desired absorption
Here we can see a plot of the absorption spectrum versus the radius of the absorbing periodic
In conjunction with DEVICE, we can also simulate the transient and steady-state temperature
distribution and electro-thermal effects, and here we have the simulated temperature
profile and transient temperature plot.
Example files for each of these devices can also be found in the Knowledge Base and links
to these examples are in the related links section below.