Femtosecond Laser Filament-Induced Discharge at Gas–Liquid Interface and Online Measurement of Its Spectrum

Gas–liquid discharge shows great promise for enhancing the efficiency of diverse energy conversion systems; however, its inherent stochasticity and instability hinder precise process control. Here, we use femtosecond laser-induced discharge combined with space–time resolution spectroscopy to achieve stable and tunable plasma generation at the gas–liquid interface. Experimental results show that the interface reduces the breakdown electric-field threshold by about 25%, shortens the breakdown delay by about 80 ns, and markedly suppresses timing jitter compared with air and the formation of high-density, low-temperature plasma, indicating that liquid-derived species participate in and reshape the ionization pathways. This work provides a controllable platform for the study of gas–liquid discharge and new insights for the design of efficient plasma auxiliary systems for multiphase flow energy conversion.