Femtosecond laser stimulation of electrical discharges in submicron and nanoscale gaps

Electrical characteristics of current-controlled discharges stimulated by femtosecond laser pulses in nanoscale gaps between sharpened metal tips and gold film substrates were studied. Pulse intensity of 5.6×1011W∕cm2 reliably triggered transient discharges in 500nm gaps. For gaps shorter than a threshold value, discharge stimulation probability was high and independent of applied potentials. At lower laser intensity, the discharge stimulation probability was also lower and depended on applied potential. It is suggested that the laser stimulated microdischarge mechanism observed in these experiments is associated with asperity breakdown by femtosecond laser ablation and field emission, resulting in release of charge carriers.