Seminarium Optyczne

An optical vortex (OV) refers to an optical donut-like beam which exhibits phase singularity surrounded by a helicoidal spatial wave-front and, associated with it, orbital angular momentum. Due to such unique properties OVs have been extensively exploited in the context of their fundamental properties as well as practical applications, particularly, optical tweezing, super-resolution imaging, quantum entanglements, and nano-structured surface machining. These promising applications require efficient approaches to generate reliable, high-quality optical vortices. In addition, from practical points of view, it is desirable to minimize the sizes of generated vortex beams as well as optimize vortex generators. The presentation focuses on flat-surface nano-structured gradient index micro-optical vortex phase mask (nVPM) components and their developments based on nanostructurization technique and effective medium theory. The mask was fabricated utilizing a cost-effective modified stack-and-draw technique. In the first part, I will introduce the concept, design and fabrication of the nanostructured vortex phase masks. Verification of its optical performance in air, water, and ethanol will be also analyzed both numerically and experimentally. Moreover, numerical studies also show that the problem of the undesirable light waveguide effect inside the gradient phase components, which accounts to the non-uniformity of the beam intensity profile, can be mitigated. In addition, possibilities to use nanostructured phase masks to generate vortices with high topological charge will be analyzed. In the next part, I will present the design and fabrication of the fiber-based vortex converter microprobe based on the aforementioned nVPM. The probe comprises a single-mode fiber, coreless fiber spacer, and nGRIN VPM integrated manually using active alignment technique. Both experimental and theoretical verifications will be discussed in this section. The results confirm that the probe efficiently converts fiber guided fundamental ode into an optical OV beam with single topological charge. The research results also confirm that the proposed nanostructurization method for the fabrication of a flat parallel surface nanostructured gradient index element is compatible with the optical fiber technique.

Seminarium z użyciem połączenia internetowego https://zoom.us/j/97696726563 (meeting ID: ID 97696726563, password: 314297)