Fractal diffraction elements with variable transmittance and phase shift

The new type of diffraction fractal elements is presented and optical fields properties, obtained from these elements are discussed. Fractal diffraction elements based on well-known fractals, possess exact or statistical selfsimilarity, but have managed amplitude transmittance and phase shift, which are correlated with fractal spatial characteristics. The fractal dimension is not enough for these objects description, and the correlation coefficient between phase/amplitude and spatial characteristic is needed. For this reason the fractal objects were called multifractal structures (MFS). It is shown that the MFS diffraction spectrum possess prevailing power of high frequencies in comparison with spectra of regular two-dimensional or fractal structures with binary transmittance and phase shift. This property could be applied for spatial filtering and transparent objects phase heterogeneities detection. Modeling results for different MFS types are presented and it is shown that MFS application allows detecting the value of initial object distortion with high accuracy. The description of fractal zone plates (FraZP) with variable transmittance and/or phase shift is also presented. The results of Fresnel diffraction modeling from FraZPs with MFS show that the correlation coefficient value has influence on the focal point position.