Spectroscopic Signatures of Plasmonic Near-Fields on High-Harmonic Emission

Intense laser fields can reveal the attosecond and femtosecond response of matter in the emitted photoelectrons and high-harmonic photons. The complementary perspective offered by these two messengers is well explored in gas molecules and, more recently, in bulk solids, where both electron emission and high-order harmonics have been utilized to probe the laser-matter interaction. In nanoscale solids, electron emission provides a wealth of information about the localized and inhomogeneous near fields around the nanoparticles. Here, it is shown experimentally that inhomogeneous fields also affect high-order harmonics. Specifically, the experiment reveals strong indications that the field gradient of a nanoscale plasmonic hotspot found inside a Si crystal induces the emission of even-order high harmonics from the crystal itself. This demonstration extends the complementary electron-photon perspective on attosecond science to nanoscale systems.

Automated summary

The study demonstrates that the field gradient of a nanoscale plasmonic hotspot inside a Si crystal induces the emission of even-order high harmonics from the crystal itself, expanding the complementary electron-photon perspective on attosecond science to nanoscale systems.