Control of electromagnetic waves by using fractal structures

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(1) "Right Angle Scattering Spectra of 3D Fractal Menger Sponge by Using Terahertz. Time-Domain Spectroscopy"We fabricated Menger sponges made of brass and measured transmission and right angle scattering spectra. In stage 2, clear minima are seen at around 2.0 cm^<-1> and 5.0 cm^<-1> in the transmission spectra. Corresponding to the minimum, a sharp peak is seen at in the right scattering These wavelengths correspond to the cut-off modes of the square rods of the Menger sponge.(2) "Using 1D Fractal Cantor-bar Microstrip Lines to Control Microwaves"We fabricated Cantor-bar microstrip lines, and measured and simulated their transmission and reflection spectra. In the stage 3 Cantor-bar, the transmission spectra showed gaps and localized modes appeared in the gap regions. Q factor of the intermediate structure revealed the largest value.(3) "Theoretical analysis of localized electromagnetic eigenmodes in the Menger sponge fractal"The eigenfrequency, field distribution, and quality factor of the localized electromagnetic eigenmodes in the metallic and dielectric Menger sponge were analyzed accurately by the method of dipole radiation with the symmetry-adapted boundary conditions based on the FDTD finite-difference time-domain calculation. The spectra of the eigenfrequency agree quite well with the peaks in the 90-degree light scattering spectra. It is shown that the LCAO approximation gives a good guiding principle for the analysis of scaling (self-similar) properties of the localized modes.(4) "Rigorous solution for electromagnetic waves propagating through pre-Cantor sets"We study one-dimensional systems constructed from a segment by employing the Cantor-set rule up to an arbitrary stage of self-similar patterns. The transmission spectra change drastically with the increase of the stage. At rather high stage the periodicity hidden in the self-similarity comes out.