Enhancing local ionization in micro-gap atmospheric discharge

Abstract

Enhancement of local ionization in micro-gap atmospheric dielectric barrier discharges is achieved experimentally via spatiotemporal control combining geometric confinement and harmonic excitation, namely adding a second-order harmonic to the applied voltage. Optimizing plasma emission near the dielectric surface is proposed as a possible route for ultraviolet plasma-on-chip sources. This approach aims to overcome the lack of integrated UV sources compatible with photonic integrated circuits (PICs). Reducing the discharge gap down to 100 µm intensifies near-chip ionization and emission by enhancing the sheath electric field and sheath overlapping during polarity reversal. Harmonic excitation, especially with a 270∘ phase difference, amplifies peak gap voltages, redistributing power temporally to further enhance local ionization and emission on the chip surface. Experiments show 48% enhancement in surface emission with the combined techniques, alongside emission profile transitions from multi-layer to single-zone structures as the gap reduces. A 1D plasma model is presented to provide insight into emission characteristics and sheath dynamics, confirming spatiotemporal control of the electric field as a prospective strategy for enhancing surface ionization and efficiently coupling UV plasma emission into PICs.