Executive Summary : | The demand for 3D control of highly focused focal fields is increasing due to applications such as nanolithography, optical data storage, laser-based materials processing, optical tweezers, and high-spatial-resolution imaging. The emerging field of structured light faces challenges in the future, particularly in the application of tailored light shapes and innovations. The ability to tailor light in all three components of the fields, often by exploiting the wide angular spectrum available in non-paraxial light, is crucial. Various attempts, including 4pi configurations, amplitude/phase/polarization modulations, and meta lenses, have been proposed to sculpture the desired sub-wavelength scale focal volume under tight focusing conditions. Digital Micromirror Device (DMD) / spatial Light Modulator (sLM) or pure phase filters are commonly used, but their efficiency is poor. Dedicated Phase masks are more efficient but require high precision nano fabrication technology and fixed parameters. A simple and efficient methodology is proposed to use the axial birefringence of thin uniform uniaxial crystal at the focal plane of a high NA objective as a controlling parameter to tailor and tune the desired 3D focal structure. This project aims to numerically investigate the complex polarization-phase transformations in tightly focused laser modes in anisotropy medium using Vector Diffraction Theory. The proposed theoretical investigation is essential for sculptured focal fields with multi-target hallmarks in a single optical setup, which is robust, scalable, flexible, and low-cost. |