| Abstract [eng] |
Over recent years, the field of modern optics exploiting free-form optics and flat optics such as metasurfaces at the microscale has attracted increasing research interest. This grow is driven by the aim to miniaturize optical elements and enhance overall compactness of optical systems while maintaining effective control of light through integrated designs. Within this context, one of the key technologies enabling fabrication of miniaturized optics is multi-photon lithography (MPL) – a maskless 3D lithography technique which, in combination with highly transparent photoresist, allows the realization of free-form micro-optical elements. At present, the practical extent to which micro-optical systems can be scaled down while still satisfying the assumptions of wave optics and the constraints imposed by MPL remains an open question. For instance, existing integrated optics designs report system lengths of several hundred micrometers to achieve sufficient beam diameter for effective light modulation. To explore the feasibility of further reducing the size of micro-optical system designs, this work investigates MPL fabricated micro beam expanders realized using an organic-inorganic hybrid photoresist – SZ2080TM, which enables the fabrication of accurate three-dimensional structures with high fidelity. Initial designs of Galilean type beam expanders showed a 2.5-fold more compact arrangement compared with existing optical fiber-integrated light-shaping devices. The multi-lens configuration further decreased the height of the micro-optical device and thus supported larger beam expansion ratios while remaining compatible with high-NA MPL fabrication. Optical performance assessment showed that the MPL-fabricated beam expander reduces beam divergence by a factor of 1.8 after 6 cm of propagation compared with free-space propagation, whereas MPL-fabricated spiral phase plates produced characteristic vortex-like intensity distributions, demonstrating their suitability for beam-shaping applications. The combined micro-optical device, consisting of a beam expander and a spiral phase plate within a total height of 138 µm, also showed a vortex-like intensity distribution, suggesting that MPL can integrate complex optical functionalities within a single micro-architecture. |
