Focused Xe-Ion Plasma Beam Milling of Coumarin-153 Single Crystals Into Photonic Cavities–Experimental and Theoretical Investigations

Focused ion beam (FIB) milling with Ga-ions enabled early success in fabricating photonic cavities in organic crystals, advancing crystal photonic foundry. However, Ga-ion milling often causes contamination and amorphization. In contrast, Xe-ion plasma milling, with its inertness, faster milling, smoother finishes, and reduced sidewall damage, presents a promising alternative. This study introduces Xe-ion plasma milling for coumarin-153 dye crystals, to fabricate precise disc (DR1 and DR2) and ring resonators (RR1 and RR2). These resonators, crucial for sensors and photonic integrated circuits, support sustained light recirculation and enhanced optical signals, evident as resonant modes in photoluminescence spectra. Finite element analysis confirms the expected resonant optical modes and strong optical field localization near the resonators' outer boundaries, highlighting the FIB milling potential for advancing organic crystal photonics.