Investigation of the characteristics of complex diffractive structures based on a combined approach

The paper is devoted to the study of electrodynamic structures, which include metal and dielectric elements. Simple elements are calculated using the method of integral equations. Their solution is determined by the collocation method and scattered electromagnetic fields. The finitedifference method is required for calculating the equation. For required scattering characteristics of complex electrodynamic structures the choice of diffraction elements is carried out within the framework of a multialternative optimization approach. The individual electrodynamic components are considered first. Then, on their basis, several promising variants of more complex subsystems are formed. It is necessary to apply training information on every stage of modeling. The example of the investigated electrodynamic structure is given. The definition of its characteristics is demonstrated.

SUBSTRATE MATERIAL INFLUENCE ON THE THERMOCHEMICAL LASER WRITING OF DIFFRACTIVE STRUCTURES ON ZIRCONIUM FILMS

The paper is devoted to comparing the features of the formation of oxide microstructures during direct laser writing on thin (100 nm) zirconium films deposited on glass and fused silica substrates to identify the most stable and predicted writing modes. The presence of self-induced oxide quasiperiodic structures was detected during continuous laser writing on zirconium films deposited on glass substrates. The effect of the formation of nanostructures, which are parallel cracks in the oxide layer and have a period equal to the recording step (250-500 nm), formed during the writing process on zirconium films deposited on a quartz substrate is revealed. The advantages of fused silica as a substrate material for direct laser writing on zirconium films are shown due to the higher softening temperature of fused silica compared to glass.

Study of thin, achromatic diffractive structures to focus terahertz radiation on a detector

Thin and lightweight achromatic focusing elements with F-number close to 1 are desirable in many practical applications. We present the idea to use diffractive structures designed to work for the substantially increased THz frequency range. The paper analyses mono- and multi-focal lenses forming point-like foci as well as axicon and light sword optical elements focusing THz radiation into line segments located along the optical axis. We consider diffractive elements in a form of the first and the second order kinoforms having various thicknesses. Designed and fabricated elements were numerically and experimentally examined to verify their achromatic functioning. We present point spread functions (XY scans) and 2D energy maps (XZ scans) for different THz frequencies. Moreover, a diagram of chromatic aberration is created by registering energy distribution along the optical axis for different frequencies. The distance corresponding to the highest energy is chosen for each frequency. Therefore, we can compare broadband working of designed structures. The spherical lens coded as kinoform of the second order provides the best broadband functioning, however it is two times thicker than structures providing extended depth of focus (light sword and axicon) working with slightly smaller efficiency but being much thinner.

OPTIMIZATION OF OPTICAL CHANNEL OF SCANNING LASER NANOLITHOGRAPHER FOR WRITING ON PHOTO- AND THERMO-SENSITIVE MATERIALS

New units and modified constructional components of an optical channel of a scanning X-Y laser nanolithographer are described. The nanolithographer serves for direct laser writing of subwavelength diffractive structures on thin-film photo- and thermo-sensitive materials deposited on planar transparent glass substrates. Significant changes were introduced into a unit of spatial frequency filtration, expansion and collimation of the laser beam of a writing laser. A new unit for on-line in-situ inspection of written diffractive structure is a unit of backward incoherent illumination.