On the design of photonic crystal multiplexers

Self-imaging in periodic dielectric waveguides

Self-imaging phenomena in periodic dielectric waveguides has been predicted and investigated based on multimode interference effect by using the plane wave expansion method and the finite-difference timedomain method. Asymmetric and symmetric interferences were discussed and respective imaging positions were calculated. As examples of application, a demultiplexer and a filter with ultracompact and simple structures were designed and demonstrated theoretically for optical communication wavelengths.

Design of ultra-compact metallo-dielectric photonic crystal filters

Filter characteristics of metallo-dielectric photonic crystal slabs are analyzed using the Multiple Multipole Program combined with the Model-Based Parameter Estimation technique. This approach takes losses and material dispersion into account and provides highly accurate results at short computation time. Starting from this analysis, different ultra-compact band pass filters for telecommunication wavelengths are designed. The filters consist of five silver wires embedded in a waveguide structure. By applying stochastic and deterministic techniques the filter structures are optimized to obtain the desired characteristics.

Optimization of photonic crystal structures

We report on the numerical structural optimization of two-dimensional photonic crystal (PhC) power dividers by using two different classes of optimization algorithms, namely, a modified truncated Newton (TN) gradient search as deterministic local optimization scheme and an evolutionary optimization representing the probabilistic global search strategies. Because of the severe accuracy requirements during optimization, the proper PhC device has been simulated by using the multiple-multipole program that is contained in the MaX-1 software package. With both optimizer classes, we found reliable and promising solutions that provide vanishing power reflection and perfect power balance at any specified frequency within the photonic bandgap. This outcome is astonishing in light of the discrete nature inherent in the underlying PhC structure, especially when the optimizer is allowed to intervene only within a very small volume of the device. Even under such limiting constraints structural optimization is not only feasible but has proven to be highly successful.

Design and optimization of an achromatic photonic crystal bend

We perform a simple sensitivity analysis of a W1 waveguide bend in a photonic crystal (PhC) where we use the information obtained to optimize the PhC bend's frequency response. Within a single optimization step we already achieve very low power reflection coefficients over almost the entire frequency range of the photonic bandgap (PBG), i.e., an achromatic bend. A further analysis shows that there is a single critical rod in the optimized bend structure that exhibits an extraordinary high sensitivity at a given frequency. Hence power reflection becomes tunable from 0 % up to 100 % involving only small changes in the critical rod's properties. This opens the door to novel topologies for compact switches and sensor applications.