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The concept of fractal, such as Cantor set, has been combined with the Fresnel zone plates (ZPs) to improve its imaging capability and introduce additional freedom for optimizing. In this letter, Fibonacci zone plates (FiZPs), which is generated by means of Fibonacci fractals, was proposed. The FiZPs can be constructed by the generating rules of the Fibonacci sequences similar with the Cantor set zone plate published. Numerical simulation based on Fresnel diffraction is performed to verify the on-axis intensity distribution of the FiZPs. According to the simulated results, the FiZPs can focus the incident beam as conventional zone plates as well but with fractal on-axis intensity profile. The theoretical results are also verified by the experiment by means of phase-only spatial light modulator (pSLM). Furthermore, the spiral Fibonacci zone plate (sFiZPs) was designed by overlapping the spiral phase on the FiZPs. Both numerical simulations and experiments are performed and the results are coincident well with each other.

A new kind of bowtie related structures, Sierpinski complementary bowtie aperture (SCBA), is proposed for enhancing and confining optical magnetic field. The magnetic field enhancement factor can be improved with the presence of the fractal. Numerical simulation shows that higher iteration of the SCBA is responsible for the variation of the resonant wavelengths. The magnetic field distributions illustrated 10nm above the output plane prove the magnetic intensity is confined in the sub-wavelength scale. Further investigation demonstrates current can be enhanced in the center of the apertures while electric fields are found to be easier to concentrate at the tiny fractal structures. Magnetic intensity distributions at several resonant points in the spectrum of the third-iteration SCBA are also plotted and the longer wavelength region in near infrared is found to be unsuited for confining magnetic field in SCBA due to weak interaction with the fractals.