Abstract
Nanostructures exposed to ultrashort waveform-controlled laser pulses enable the generation of enhanced and highly localized near fields with adjustable local electric field evolution. Here, we study dielectric SiO2 nanospheres (d = 100–700 nm) under strong carrier-envelope phase-controlled few-cycle laser pulses and perform a systematic theoretical analysis of the resulting near-field driven photoemission. In particular, we analyze the impacts of charge interaction and local field ellipticity on the near-field driven electron acceleration. Our semiclassical transport simulations predict strong quenching of the electron emission and enhanced electron energies due to the ionization induced space charge. Though single surface backscattering remains the main emission process for the considered parameter range, we find a substantial contribution of double rescattering that increases with sphere size and becomes dominant near the cutoff energy for the largest investigated spheres. The growing importance of the double recollision process is traced back to the increasing local field ellipticity via trajectory analysis and the corresponding initial to final state correlation. Finally, we compare the carrier-envelope phase-dependent emission of single and double recollision electrons and find that both exhibit a characteristic directional switching behavior.
Highlights
The excitation of nanostructures with laser light can be utilized to generate near fields that are localized on sub-wavelength scales and exhibit strong-field enhancement [1]
Our study shows that the yields of single and double recollision electrons exhibit nearly linear dependencies with both intensity and size, which can be explained as a result of space charge trapping in the nanosphere’s Coulomb potential
The analysis further shows that double recollision electrons become important for large spheres because of the increasing relative strength of tangential field components
Summary
The excitation of nanostructures with laser light can be utilized to generate near fields that are localized on sub-wavelength scales and exhibit strong-field enhancement [1]. The feasibility of using nonresonant near fields for the control of strong-field electron dynamics with high time resolution has been demonstrated in photoemission experiments on metal nanotips [3,4,5,6,7], isolated dielectric nanospheres [8,9,10], and surface-assembled nanoantennas [11]. The importance of the spatial field profile has been shown by the observed quenching of backscattering if the quiver amplitude exceeds the near-field extension [4]. In this impulsive acceleration regime, spectral focussing and defocussing via an additional THz field has been demonstrated in the strong-field emission from biased nanotips [13]. Near fields have been used to drive quantum-coherent electronic free–free transitions of high-energy electrons [14], in analogy to two-color atomic strong-field ionization of atoms [15]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
