3D structured Bessel beam polarization and its application to imprint chiral optical properties in silica

Polarization plays a crucial role in light-matter interactions; hence its overall manipulation is an essential key to unlock the versatility of light manufacturing, especially in femtosecond laser direct writing. Existing polarization-shaping techniques, however, only focus on their manipulation in the transverse plane of light beams, i.e., two-dimensional control. In this paper, we propose a novel passive strategy that exploits a class of femtosecond laser written space varying birefringent elements to shape the polarization state along the optical path. As a demonstration, we generate a three-dimensional structured Bessel beam whose linear polarization state slowly evolves along the focus (typ. 90 degrees within 60 lambda). Such a helically polarized Bessel beam allows imprinting twisted nanogratings in SiO2 glass which result in an extrinsic optical chirality at a micrometric scale and own a high optical rotation. Our work provides new perspectives for three-dimensional polarization manipulation and insights into applications in structured light, light-matter interaction, and chiral device fabrication. (c) 2023 Author(s).

Automated summary

Polarization manipulation is crucial for unlocking the versatility of light manufacturing, and existing techniques only focus on two-dimensional control. In this paper, we present a novel passive strategy using femtosecond laser written birefringent elements to shape polarization along the optical path. We demonstrate the generation of a three-dimensional structured Bessel beam with a slowly evolving polarization state, enabling the imprinting of twisted nanogratings and high optical rotation. Our work provides new perspectives on three-dimensional polarization manipulation and insights into applications in structured light and chiral device fabrication.