Interplay of pulse duration, peak intensity, and particle size in laser-driven electron emission from silica nanospheres

Abstract

We present the results of a systematic study of photoelectron emission from gasphase dielectric nanoparticles (SiO 2 ) irradiated by intense 25 fs, 780 nm linearly polarized laser pulses as a function of particle size (20 nm to 750 nm in diameter) and laser intensity. We also introduce an experimental technique to reduce the effects of focal volume averaging. The highest photoelectron energies show a strong size dependence, increasing by a factor of six over the range of particles sizes studied at a fixed intensity. For smaller particle sizes (up to 200 nm), our findings agree well with earlier results obtained with few-cycle, ~4 fs pulses. For large nanoparticles, which exhibit stronger near-field localization due to field-propagation effects, we observe the emission of much more energetic electrons, reaching energies up to ~200 times the ponderomotive energy. This strong deviation in maximum photoelectron energy is attributed to the increase in ionization and charge interaction for many-cycle pulses at similar intensities.

Three-dimensional Imaging of Nanoplasma by Ion Nanoscopy

“…1c). As the predicted ion yields are proportional to the laser intensity, the number of emitted ions per laser shot serves as a guide for near-single intensity sampling of the nanosphere interaction 28 . This data discrimination provided us with each ion image used for reconstruction under the same experimental conditions.…”

“…The ion count per 2D VMI image can be used as a coarse guide for the near-single intensity sampling of the laser interacting on the nanospheres, called the intensity binning technique 28 . By a LabVIEW script, we rstly recorded the 2D VMI image and counted the ion numbers of every image.…”

Strong-field physics with nanospheres

“…We will start the discussion in Section 4 by reviewing early surprises where rescattering from small dielectric nanospheres was first observed [36] and continue with inspecting the decisive impacts of charge interaction on the electron emission [43,44]. Section 5 focuses on the effects induced by field propagation within larger dielectric nanospheres and resulting implications and applications [41,[45][46][47][48]. In Section 6 we will review the ultrafast laser-induced metallization of initially dielectric spheres.…”

Tunable Near‐ to Far‐Infrared Optical Breakdown in Nonlinear Interactions of Ultrashort Laser Pulses with Water Microdroplets in Ambient Air

“…Water droplets are omnipresent in biophysical environments and ecosystems, playing an important role in communication through the atmosphere (i.e., aerosols and contaminants, fog, mist, haze, drizzle, clouds) and being involved in a variety of physicochemical reactions and biological processes (respiratory droplets due to breathing, talking, coughing, etc., biological cells, bioaerosols, water clusters, surface adhesion, and wettability). Broad opportunities in analysis, detection, and control over droplet distributions are enabled by the application of powerful lasers used for laser breakdown, [ 1–3 ] electron photoemission [ 4–7 ] and cavity‐enhanced droplet spectroscopy, [ 8,9 ] long‐distance optical communications, [ 10–12 ] and high harmonic generation from water microdroplets. [ 13–15 ] The processes of ultrashort laser excitation and ionization of water droplets and aerosols remain poorly explored for a wide range of photon energies and wavelengths from visible to long‐wave infrared (IR) range.…”

“…Electron plasma formation inside aerosols and microdroplets is closely related not only to the particle damage but also to drastic transient changes in scattering and absorption behavior in the atmosphere, as well as electron spill-out through the water interface, resulting in photoemission patterns of different directionality, [4,6] nanofocusing and nanoshadowing effects in photo-electron spectroscopy. [5,7] This serves as a potential tool for detection and analysis of atmospheric contaminants.…”