Coherent control at gold needle tips approaching the strong-field regime

We demonstrate coherent control in photoemission from a gold needle tip using an omega - 2(.)omega field composed of strong few-cycle laser pulses with a nearfield intensity of similar to 4 TW/cm(2). We obtain the nearfield intensity from electron energy spectra, showing the tell-tale plateau of field-driven electron rescattering at the metal surface induced by the fundamental field. Changing the relative phase between the fundamental field centered at 1560 nm and its second harmonic modulates the total emitted photocurrent with visibilities of up to 80% despite the strong and broadband excitation of the plasmonic material. Our work combines a two-color coherent control scheme and strong-field physics enabled by a nanoplasmonic emitter.

Automated summary

Coherent control of photoemission from a gold needle tip was demonstrated using an omega - 2(omega) field composed of strong few-cycle laser pulses, with nearfield intensity of around 4 TW/cm(2). Changing the relative phase between the fundamental field and its second harmonic modulated the total emitted photocurrent with visibilities of up to 80% despite strong and broadband excitation of the plasmonic material. This work combines a two-color coherent control scheme with strong-field physics enabled by a nanoplasmonic emitter.