Tunable ultrafast thermionic emission from femtosecond-laser hot spot on a metal surface: role of laser polarization and angle of incidence

Abstract

Ultrafast laser induced thermionic emission from metal surfaces has several applications. Here, we investigate the role of laser polarization and angle of incidence on the ultrafast thermionic emission process from laser driven gold coated glass surface. The spatio-temporal evolution of electron and lattice temperatures are obtained using an improved three-dimensional (3D) two-temperature model (TTM) which takes into account the 3D laser pulse profile focused obliquely onto the surface. The associated thermionic emission features are described through modified Richardson-Dushman equation, including dynamic space charge effects and are included self-consistently in our numerical approach. We show that temperature dependent reflectivity influences laser energy absorption. The resulting peak electron temperature on the metal surface monotonically increases with angle of incidence for P polarization, while for S polarization it shows opposite trend. We observe that thermionic emission duration shows strong dependence on angle of incidence and contrasting polarization dependent behaviour. The duration of thermionic current shows strong correlation to the intrinsic electron-lattice thermalization time, in a fluence regime well below the damage threshold of gold. The observations and insights have important consequences in designing ultrafast thermionic emitters based on a metal based architecture.

17 pages, 7 figures, 1 table

References in corpus (10)

• Thermophotovoltaic Efficiency of 40%
• Ultrafast dynamics of electrons and phonons: from the two-temperature model to the time-dependent Boltzmann equation
• Influence of the electron-phonon interfacial conductance on the thermal transport at metal/dielectric interfaces
• Long-lived modulation of plasmonic absorption by ballistic thermal injection
• Sub-ps thermionic electron injection effects on exciton-formation dynamics at a van der Waals semiconductor/metal interface
• High brightness ultrafast Transmission Electron Microscope based on a laser-driven cold-field emission source: principle and applications
• Ultrafast electron dynamics in platinum and gold thin films driven by optical and terahertz fields
• Plasma-induced surface cooling
• Excitation and Relaxation of Nonthermal Electron Energy Distributions in Metals with Application to Gold
• Controlled transition to different proton acceleration regimes: near-critical density plasmas driven by circularly polarized few cycle pulse