We demonstrate strong-field photoelectron emission from gold nanorods driven by femtosecond mid-infrared optical pulses. The maximum photoelectron yield is reached at the localized surface plasmon resonance, indicating that the photoemission is governed by the resonantly-enhanced optical near-field. The wavelength- and field-dependent photoemission yield allows for a noninvasive determination of local field enhancements, and we obtain intensity enhancement factors close to 1300, in good agreement with finite-difference time domain computations.
Kusa, F., Echternkamp, K. E., Herink, G., Ropers, C., & Ashihara, S. (2015). Optical field emission from resonant gold nanorods driven by femtosecond mid-infrared pulses. AIP Advances, 5(7). https://doi.org/10.1063/1.4927151