Three-dimensional active tunable spiral zone plates for selective adjusting of optical vortex and depth of focus
Abstract
Diffractive optical elements (DOEs) have a number of advantages over refractive or reflective optical elements, including improved dispersion, wider profile tolerances, and greater design freedom. A critical DOE, the Fresnel zone plate (FZP) is widely used in a variety of optical systems, including nano/micro focusing lenses, X-ray imaging, and beam shaping. Optics research on tunable functional devices has a long history of being an enticing field, having a significant impact on the evolution of optical information technology and photonic integrated circuits. The active-spiral Fresnel zone plate (ASFZP), the nanoscale polymer-dispersed liquid crystals (LC) tunable Fresnel lens, and the tunable spiralized Fresnel zone plate are all examples of tunable zone plates. All previously described tunable zone plates achieve tunability by modifying their properties or shape in two dimensions along the lateral plane. In this study, we demonstrate an active flexible three-dimensional tunable spiral plate (3DSP). Rather than alternating bright and dark zones, these zone plates have a spiral pattern in three dimensions. These zone plates enable tunability in both wavelength and depth of focus by actively modifying the lateral and vertical planes. These zone plates achieve a combination of selective wavelength transmission and predefined depth of focus by activating the 3DSP to predefined settings.