Limitations of Extreme Nonlinear Ultrafast Nanophotonics

Abstract

High-harmonic generation (HHG) has been established as an indispensable tool in

optical spectroscopy. This effect arises for instance upon illumination of a

noble gas with sub-picosecond laser pulses at focussed intensities significantly

greater than 1012W/cm2. HHG provides a coherent light source in the extreme

ultraviolet (XUV) spectral region, which is of importance in inner shell photo

ionization of many atoms and molecules. Additionally, it intrinsically features

light fields with unique temporal properties. Even in its simplest realization,

XUV bursts of sub-femtosecond pulse lengths are released. More sophisticated

schemes open the path to attosecond physics by offering single pulses of less

than 100 attoseconds duration.

Resonant optical antennas are important tools for coupling and enhancing

electromagnetic fields on scales below their free-space wavelength. In a special

application, placing field-enhancing plasmonic nano antennas at the interaction

site of an HHG experiment has been claimed to boost local laser field strengths,

from insufficient initial intensities to sufficient values. This was achieved

with the use of arrays of bow-tie-shaped antennas of ∼ 100nm in length. However,

the feasibility of this concept depends on the vulnerability of these

nano-antennas to the still intense driving laser light.We show, by looking at a

set of exemplary metallic structures, that the threshold fluence Fth of

laser-induced damage (LID) is a greatly limiting factor for the proposed and

tested schemes along these lines.We present our findings in the context of work

done by other groups, giving an assessment of the feasibility and effectiveness

of the proposed scheme.