Axial-Symmetric Diffraction Radiation Antenna with a Very Narrow Funnel-Shaped Directional Diagram

The paper is focused on reliable modeling and analysis of axially symmetric radiators with a very narrow (throat) funnel-shaped radiation pattern. When such a diagram is formed, a wave analogue of Smith–Purcell coherent radiation is realized—the surface wave of a radial dielectric waveguide ‘sweeps out’ with its exponentially decaying part a concentric periodic grating, the fundamental spatial harmonic of which, propagating without attenuation in a direction close to the symmetry axis of the structure, generates a radiation field with the required characteristics.

Направленные поверхностные акустические волны в нецентросимметричных решетках

Spatial distribution of surface Rayleigh acoustic wave propagating along the surface of GaAs semiconductor covered by a periodic grating of gold stripes is calculated. We demonstrated that when the lattice has no center of spatial inversion the distribution of deformation for the surface wave with the Bloch wave vector kx = 0 is asymmetric and characterized by nonzero mean momentum in the interface plane and nonzero degree of transverse polarization in the plane perpendicular to the surface. The work has been supported by the Russian Science Foundation Grant No. 20-12-00194.

Coloration of Surfaces with Periodic Microstructures Replicated by Non-isothermal Precision Molding

Micro/nano periodic structures are generally adopted in diffraction gratings. As an important optical component, the diffraction grating has the capability to split and diffract incident white light beams into iridescent beams dispersing to different directions. The appearance of coloration is a form of structural coloration by optical diffraction. In this paper, the non-isothermal precision molding is introduced for rapid & precise replication of periodic micro/nano grating structures, which are employed to render iridescent colors onto surfaces. Firstly, the effect of colorization and periodic grating profiles are theoretically analyzed. Secondly, different periodic micro gratings on silicon wafer, which are generally generated by photolithography, are employed in non-isothermal precision molding process as mold inserts. The molding result indicates that the periodic grating space and depth of grating structures can be precisely replicated from the mold inserts to polymer substrates. Subsequently, the split and iridescent color effects are demonstrated with monochromatic & white incident light beam and compared between samples with different periodic grating spaces. The optical effects of the replicated micro-structures confirm the feasibility of this method. The proposed non-isothermal precision molding process provides an alternative manufacturing option for realizing structural colors with large volume and low cost.

Measuring Optical Properties of Advanced Nano/Micro-Periodic Structures Fabricated by Multi-Exposure Interference Lithography

Functional optical elements based on nano/micro-periodic structures have attracted much attention. Since the fabrication of these dual-periodic structures requires precise control of periodicity, the semiconductor process such as an electron beam lithography has been mainly employed. However, these techniques have problems with expensive and low throughput for industrial applications. Therefore, there remains a need for low cost and high throughput fabrication methods of dual-periodic structures. Then we developed a multi-exposure interference lithography (MEIL) system using rotational Lloyd’s mirror interferometer to overcome these problems. The advantages of interference lithography are a large processing area and low cost. Our developed rotational Lloyd’s mirror setup enables us to a highly precise superposition of multiple interference fringes by multi-exposure. Furthermore, we developed a measurement setup for reflective diffractive elements using a two axial rotating stage and measured the diffraction properties of the fabricated dual-periodic diffraction gratings. In this paper, as a demonstration, we succeeded in the fabrication of high-dispersion diffraction grating with an enhanced diffraction efficiency of the −3rd order light. The fabricated shapes have a periodicity of 1997 nm and 665 nm. Furthermore, it was confirmed that the intensity of the −3rd order light was enhanced by about 10 times compared to the single periodic grating.

Structrual Coloration of Surfaces With Microstructures Replicated by Non-Isothermal Precision Glass Molding

Micro/nano periodic structures are generally adopted in diffraction gratings. As an important optical component, the diffraction grating has the capability to split and diffract incident white light beams into iridescent beams travelling in different directions. The emerging coloration is a form of structural coloration. In this paper, the non-isothermal precision glass molding is introduced for fast replication of periodic grating structures, which are employed to render iridescent colors on surfaces. Firstly, the effect of colorization and periodic grating profiles is theoretically analyzed. Secondly, different periodic micro gratings on silicon wafer, which are generally generated by photolithography, are employed in non-isothermal precision glass molding process as mold inserts. The molding result indicates that the periodic grating space and depth of grating structures can be precisely replicated from the mold inserts to polymer substrates. Subsequently, the split and iridescent color effects are demonstrated with monochromatic & white incident light beam and compared between samples with different periodic grating spaces. The optical effects of the replicated micro-structures confirm the feasibility of this method. The proposed non-isothermal precision glass molding process provides an alternative manufacturing option for realizing structural colors with large-volume and low-cost.