One step femtosecond direct laser writing (fs-DLW) of tunable optical vortex (OV) generator

Optical Vortices (OVs) find applications in various fields including high-order quantum entanglement, optical tweezers, astrometry, medicinal applications, and nonlinear optics. However, traditional passive methods for generating OVs, such as custom synthetic holograms, spiral wave plates, double cylindrical lens phase converters, light scattering from uneven surfaces, and interference of regular waves, often produce single-mode OVs or lack adjustability and flexibility. Here, we introduce an innovative, fully characterized, passively tunable device for generating optical vortices. This device is fabricated using 3D femtosecond direct laser writing (3D fs-SLW) techniques and incorporates a three-dimensional pattern of silver microstructures embedded in a biodegradable polymer matrix. The 3D silver patterning is achieved through multiphoton-assisted photoreduction. This novel approach offers significant potential for advanced applications such as optical tweezers and micro/nano photonics.