Photoemission at metallic nanostructures: multiphoton and strong-field dynamics

Photoemission from nanostructures offers sub-wavelength field localization and enhancement. Excited by ultrashort pulses, electron emission can be confined and controlled in both time and space. Studies with metallic nanotips have examined the transition to strong-field conditions in photoemission. Reaching deeply into this regime with ultrashort mid-infrared pulses, we generate photoelectrons up to hundreds of electron volts and observe dynamics in which electrons are ejected from the field-enhanced region in less than an optical half cycle. Moreover, single cycle terahertz pulses are shown to yield a novel means of control over the photoemission process.