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HL: Fachverband Halbleiterphysik

HL 1: Optical Properties I

HL 1.9: Vortrag

Montag, 9. März 2026, 11:45–12:00, POT/0006

Phase-matched electron-photon interactions enabled by 3D printed helical waveguides — •Masoud Taleb¹, Mohsen Samadi², and Nahid Talebi¹ — ¹Institute of Experimental and Applied Physics, Kiel University, 24098 Kiel, Germany — ²Department of Electrical and Information Engineering, Kiel University, 24143 Kiel, Germany

We demonstrate a new phase-matching mechanism between free electrons and guided optical modes using 3D-printed helical waveguides. The structure consists of a polymer micro-fiber coated with a thin gold layer, fabricated by two-photon polymerization. When an electron beam propagates parallel to the helix axis, the helical geometry extends the optical path and enables sequential, phase-synchronous coupling to a plasmonic hybrid mode. This interaction unifies elements of Smith-Purcell and Cherenkov emission and yields a strong, highly directional visible-light output. Cathodoluminescence measurements reveal a dominant emission near 2.1-2.2 eV, collimated along the electron trajectory and exhibiting circular polarization dictated by the helix handedness. The observed photon yield (~0.02 photons per electron for an 11-turn helix) exceeds that of planar electron-driven photon sources by more than two orders of magnitude. These results introduce helical micro-waveguides as an efficient platform for directional, polarization-controlled electron-photon interactions.

Keywords: Free-electron light sources; Helical waveguide; Electron–photon interactions; Cathodoluminescence spectroscopy; 3D microprinting / two-photon polymerization