It is possible to increase the radiative decay rate by modifying the environment of the emitting dipoles with the addition of microscopic patterning. Increasing the radiative decay rate can allow for a higher electrical excitation rate. It will also increase the internal quantum efficiency because radiative decay processes can compete more efficiently with non-radiative processes. By relating the radiative decay rate to the power radiated by a dipole source, we can study this effect using FDTD Solutions.
Finally, it should be noted that introducing patterning may have effects on the electrical properties of the device. Modeling these effects is beyond the scope of FDTD Solutions.
Lastly, a parallel FDTDmethod was also used to model another interesting coordinate transformation baseddevice, an optical black hole, which can be characterised as an omnidirectional broad-band absorber.
Designing OLED/LED devices requires a combination of nanoscale and macroscale optics. The individual pixels often have sub-wavelength features such as thin dispersive layers scattering structures that require electromagnetic field solvers, while the emission from the macroscopic device requires a ray-based tool. For these applications, one can calculate the angular distribution of a pixel with the Stack Optical Solver or FDTD Solutions, and then load the result into a ray tracing tool in the form of ray sets.
Cole, "Electromagnetic Imaging of Two-Dimensional Geometries by Multipulse Interference Using the Inverse FDTD Method," Advances in Optical Technologies, vol.
Microscopic optical effects: This is typically done with gratings or patterning in and near the emission layers. Ideally these gratings can assist in extracting light that is trapped in the emission layers and extracting it into the glass at angles where it will not suffer TIR at the glass/air interface. We can study this effect directly with FDTD Solutions.
Macroscopic optical effects: this mainly involves patterning or roughening the air/glass interface which can be used to reduce TIR. Also, some authors have concluded that patterning near the emission layers can lead to increased efficiency for the same reason: the light makes multiple round trips from the emission layers to the glass/air interface, and scattering from the grating at the emission layer can change the direction of the reflected light and prevent TIR at the air/glass interface. For example, Peter Vandersteegen, in "Modeling of the Optical Behavior of Organic LEDs for illumination" (Doctoral Thesis, 2008, ), concludes in section 5.4.6 that a substantial efficiency improvement is available for certain designs due to multiple round trip scattering events, but that the efficiency improvement is negligible when these multiple round trip events are ignored. This effect can be studied using FDTD Solutions either by calculating the angular emission of the light in the glass and then combining these results with considerations of the multiple round trip effects or by artificially reducing the thickness of the glass layer such that it can be directly modeled by FDTD and yet remain thick enough to obtain accurate results.
In the second half of the thesis, we focus on an important application of the FDTD method, the computational time reversal (TR) technique, which is an algorithm applied in inverse source problems such as source reconstruction.
Based on the finding, we then derived the analytic solution of the FDTD method, presenting an alternative non-iterative time-domain approach for electromagnetic problems.
The major constraint of the FDTD method is, in its iterative solution process, that the time step is restricted by the Courant-Friedrichs-Lewy (CFL) condition.
Optimizing the conductivity profile allows reduction of the PML thickness.A typical application of the FDTD method is the design of a mobile handset antenna.
In modeling electromagnetic structure problems, finite-difference time-domain (FDTD) method is one of the most well-known and widely adopted methods due to its algorithmic simplicity and flexibility.
Following its theoretical development, the modified FDTD method is applied to three classes of problems: the modeling of nonlinear corrugated optical wave guide beam steering and output coupling devices, the rigorous treatment of metallic thin film diffraction gratings, and the modeling of tracking signals produced by realistic optical data storage disk geometries.