Spatially Controlled Phase Modulation – Selective Higher-OrderMode Excitation in 3D Nanoprinted on-Chip Hollow-CoreWaveguides

Higher-order modes and hollow-core waveguides are highly relevant research directions in photonics, while most studies are solely focused on fundamental modes. This work introduces a novel approach to efficiently excite higher-order modes in nano-printed hollow-core waveguides using spatially controlled phase modulation. The key lies in the integration of precisely designed nanoprinted phase elements at the beginning of an antiresonant waveguide, which creates a spatially controlled phase shift that matches the phase distribution of the desired mode. Both experiments and simulations confirm efficient excitation of specific higher-order modes and verify antiresonant light guidance within the core. The study details all aspects of this approach, including a mathematical model explaining the importance of phase matching, simulations demonstrating the effect of the phase elements, and experimental verification using 3D nanoprinting and optical characterization. This approach enables the precise excitation of selected higher-order modes in a nanoprinted hollow-core waveguide, combining several key features in an integrated on-chip photonic platform with a small geometric footprint. Potential applications span across multiple disciplines, including nanoscience, analytical chemistry, and materials science. The flexibility of the concept and implementation method allows for transferring it to other types of on-chip waveguides and optical fibers, opening up new avenues for waveguide photonics.