Ultra-long photonic jets and large depth of field imaging driven by Bessel-like energy redistribution in micro-pyramid array

This study proposes and experimentally demonstrates an ultra-long photonic jet generator based on a micro-pyramid array. The device forms and maintains a quasi-Bessel-type extended main lobe in free space, thereby achieving an ultra-long imaging range and a large depth of field (DOF). Numerical simulations indicate that the micro-pyramids form a high-intensity main lobe over an ultra-long axial distance of 878λ. A high-consistency array was fabricated on a PMMA substrate using single-point diamond turning (SPDT). Focal spot experiments conducted on a micro-pyramid array with a base width of 90 μm yielded an axial decay length of 1170λ, which closely matches the simulations and supports the proposed ultra-long focusing mechanism driven by Bessel-like wavefront redistribution. Further z -sequential imaging tests demonstrate that stable contrast and discernible textures (with a minimum resolvable spacing of 5.58 μm) are maintained within an axial range of 100–825 μm, indicates a significantly extended imaging range and large DOF. Samples with a small base width (40 μm) achieved higher lateral resolution (minimum resolvable spacing of 2.94 μm) at shorter working distances, revealing a tunable trade-off between “resolution” and “depth of field” governed by structural parameters. This work provides an experimental pathway for structured light field elements suitable for scalable fabrication and array integration.