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The paper presents results of the experimental investigation of “spectral” diffractive lenses the same focus position for several given wavelengths. Two spectral diffractive lenses designed to focus radiation of three and five specified wavelengths in the visible spectrum were investigated. Using a method of direct laser writing in photoresist with iterative correction of writing parameters, we fabricated a diffractive microrelief of the spectral lenses with the height deviation from the designed relief of less than 30 nm. Using a pinhole located at the focus of the fabricated lenses, we estimated the operation wavelengths. The point spread functions of the spectral lenses at the designed wavelengths were measured with the use of a tunable laser. The imaging properties of the spectral lenses were illustrated by the images of a reference color table.

A method for calculating a “spectral” diffractive lens, which ensures the preservation of the focal position at several prescribed wavelengths is proposed. The method is based on minimizing the function characterizing the difference between the complex transmission functions of the spectral lens for given wavelengths and the complex transmission functions of diffraction lenses calculated separately for each of the given wavelengths. As examples, spectral diffractive lenses are calculated for three and seven wavelengths. The simulation results of the calculated lenses confirm good performance of the proposed method.

We consider the possibility of using generalized lenses in imaging optical systems. We propose using two generalized lenses in a system similar to a Fourier-correlator to obtain a point-to-point mapping, where the second lens is set so that a plane wave is also formed at the output of the system when the incident wave is plane. We show that for generalized lenses with a small deviation of their degree from 2, such a system forms a fairly high-quality image. We use a standard radial photographic chart to test the system, which allows us to determine its key optical characteristics.

We described an experiment on passing Bessel beams through the atmosphere with heat-trolled flows. We showed that at small distances, while passing through the region with a hot air flow, the Bessel beam can be distorted to a complete loss of the structure, but with further propagation over large distances it completely restores its structure. We also described an experiment with the passage of superpositions of vortex beams through the atmosphere with heat flows and aerosols.