Terahertz Driven Amplification of Coherent Optical Phonons in GaAs Coupled to a Metasurface

Abstract

We demonstrate amplification of longitudinal optical (LO) phonons by polar-optical interaction with an electron plasma in a GaAs structure coupled to a metallic metasurface using two-color two-dimensional spectroscopy. In a novel scheme, the metamaterial resonator enhances broadband terahertz fields, which generate coherent LO phonons and drive free electrons in the conduction band of GaAs. The time evolution of the LO phonon amplitude is monitored with mid-infrared pulses via the LO-phonon-induced Kerr nonlinearity of the sample, showing an amplification of the LO phonon amplitude by up to a factor of 10, in agreement with a theoretical estimate.

Terahertz quantum plasmonics at nanoscales and angstrom scales

“…Metal structures such as nanotip, nanoantennas, and nanoslit and slot antennas have been of great research interest over the past two decades because of their potentials and functionalities for a broad range of applications such as chemistry, biology, and medical applications, as well as from basic research aspects [24,[51][52][53][54][55][56][57][58][59][60][61][62][63][64]. Strong field enhancement and confinement obtained at the subwavelength volume are the main resultant properties from interaction between electromagnetic waves and metal nanostructure, which are essential for nonlinear optics in nanoscale.…”

“…Electron transport through single molecules has been intensively studied because of its potential for device applications such as single-electron transistor. Beyond static properties of the single-electron transistor, its dynamical transport properties have been investigated by terahertz waves because typical energy scales in singlemolecule transport lie mostly in the terahertz frequency regime such as tunneling times, vibron energies, orbital energy spacing, charging energies, and so on [50,51]. To couple the terahertz waves to a single molecule trapped between nanogap electrodes, however, it is inevitable to utilize the plasmonic effects of metal electrodes with a nanometer sized gap.…”

Advances and opportunities in ultrafast X-ray crystallography and ultrafast structural optical crystallography of nuclear and electronic protein dynamics

“…Particularly, table-top based ultrafast powder diffraction has been very successful and has optimized and exploited the available flux for measurements of ultrafast nuclear and charge density dynamics 15–18 . Compelling and recent developments include reports on terahertz driven motion using this technique 19–21 . Whereas early instruments used near-IR sources for the hard X-ray generation, the brightness is substantially increased with the use of intense mid-infrared pulses generated by an Optical Parametric Chirped-Pulse Amplifier, improving capabilities of table-top sources significantly 22,23 .…”

Investigation of Phonon Polaritons in an hBN GaN Heterostructure

“…This decay process is shown below in Figure 1.4 and was initially used in the design for acoustic phonon lasing in 1996 [32]. Most phonon lasers generate acoustic rather than optical phonons, this is due to the significantly larger energy of optical phonons coupled with the inability to meet the inversion requirements under quasistationary conditions makes achieving amplification difficult [33].…”

“…As shown above in Figure 1.5, it is difficult to achieve gain while the electron distribution is centered around the Γ point, and rather performs absorption. Using a THz optical pump pulse the initial LO phonons are generated, and the electron distribution is shifted allowing for ( ) > ( − ) , thus fulfilling the inversion condition for gain [33].…”