Plasmon-enhanced high-harmonic generation from silicon

Abstract

Plasmonic antennas can enhance the intensity of a nanojoule laser pulse by localizing the electric field in their proximity 1 . It has been proposed that the field can become strong enough to convert the fundamental laser frequency into high-order harmonics through an extremely nonlinear interaction with gas atoms that occupy the nanoscopic volume surrounding the antennas [2][3][4] . However, the small number of gas atoms that can occupy this volume limits the generation of high harmonics [5][6][7] . Here we use an array of monopole nano-antennas to demonstrate plasmon-assisted high-harmonic generation directly from the supporting crystalline silicon substrate. The high density of the substrate compared with a gas allows macroscopic buildup of harmonic emission. Despite the sparse coverage of antennas on the surface, harmonic emission is ten times brighter than without antennas. Imaging the high-harmonic radiation will allow nanometre and attosecond measurement of the plasmonic field 8 thereby enabling more sensitive plasmon sensors 9 while opening a new path to extreme-ultraviolet-frequency combs 10

Ultrahigh Off‐Resonant Field Effects in Semiconductors

“…While most present experiments of HHG and HSG in solids have focused on unstructured bulk targets or quantum wells, using nanostructured surfaces can greatly enhance and modify the high‐harmonic emission intensity . The strong field enhancement in such nanostructures can be utilized to considerably lower the fieldstrength needed to produce HHG and help in the development of more compact HHG sources.…”

“…[], the HHG emission emerges from the nanostructures itself, Ref. [] have chosen a different approach: An array of gold nano‐antennas is grown on a crystalline silicon substrate. In this case, the harmonics are emitted predominantly from the silicon substrate due to the local field enhancement created by the antennas.…”

Investigating the origin of third harmonic generation from diabolo optical antennas

“…Our results are in agreement with the recent plasmonic enhanced high harmonic generation from a crystalline material. 28,35 We do not observe a significant enhancement of the THG emission from the bare Au itself, which is ascribed to the strong absorption by Au atoms. It will be promising to use mid-infrared femtosecond sources to further investigate the ability of bare Au for THG enhancement because in the long wavelength region, the band-to-band transition is not as significant as in the case of a near-infrared driver.…”

Ultrafast extreme ultraviolet photoemission without space charge

“…Although the highest HHG repetition rates have been reported using high-power frequency combs resonantly enhanced in optical cavities, 33,34 their reliability and suitability for time-resolved photoemission have faced skepticism from several authors 8,30,35 . Instead, there has been great investment in other approaches including HHG from high-power Ti:Sapphire and parametric amplifiers, 35,36 HHG from high power fiber lasers, 37,38 HHG generated within 39 and at the output 40 of thin-disk lasers, HHG from solids, 41,42 and HHG in the near-fields of nanostructures 43 . Despite these intense efforts, HHG-based photoemission comparable to that done with tunable synchrotron radiation has not been realized using any platform.…”