Time-Dependent Ultrafast Quadratic Nonlinearity in an Epsilon-Near-Zero Platform

TY - JOUR

T1 - Time-Dependent Ultrafast Quadratic Nonlinearity in an Epsilon-Near-Zero Platform

AU - Bykov, Anton yu.

AU - Deng, Junhong

AU - Li, Guixin

AU - Zayats, Anatoly v.

N1 - Funding Information: The authors acknowledge helpful discussions with Prof. Yonatan Sivan on the dynamics of hot carriers in ITO and assistance from Dr. Anastasiia Zaleska in characterizing the ITO thin films. This work was supported in part by the ERC iCOMM project (789340) and the UK EPSRC project (EP/Y015673/1). Publisher Copyright: © 2024 The Authors. Published by American Chemical Society.

PY - 2024/3/14

Y1 - 2024/3/14

N2 - Ultrafast nonlinearity, which results in modulation of the linear optical response, is a basis for the development of time-varying media, in particular those operating in the epsilon-near-zero (ENZ) regime. Here, we demonstrate that the intraband excitation of hot electrons in the ENZ film results in a second-harmonic resonance shift of ∼10 THz (40 nm) and second-harmonic generation (SHG) intensity changes of >100% with only minor (<1%) changes in linear transmission. The modulation is 10-fold enhanced by a plasmonic metasurface coupled to a film, allowing for ultrafast modulation of circularly polarized SHG. The effect is described by the plasma frequency renormalization in the ENZ material and the modification of the electron damping, with a possible influence of the hot-electron dynamics on the quadratic susceptibility. The results elucidate the nature of the second-order nonlinearity in ENZ materials and pave the way to the rational engineering of active nonlinear metamaterials and metasurfaces for time-varying applications.

AB - Ultrafast nonlinearity, which results in modulation of the linear optical response, is a basis for the development of time-varying media, in particular those operating in the epsilon-near-zero (ENZ) regime. Here, we demonstrate that the intraband excitation of hot electrons in the ENZ film results in a second-harmonic resonance shift of ∼10 THz (40 nm) and second-harmonic generation (SHG) intensity changes of >100% with only minor (<1%) changes in linear transmission. The modulation is 10-fold enhanced by a plasmonic metasurface coupled to a film, allowing for ultrafast modulation of circularly polarized SHG. The effect is described by the plasma frequency renormalization in the ENZ material and the modification of the electron damping, with a possible influence of the hot-electron dynamics on the quadratic susceptibility. The results elucidate the nature of the second-order nonlinearity in ENZ materials and pave the way to the rational engineering of active nonlinear metamaterials and metasurfaces for time-varying applications.

UR - http://www.scopus.com/inward/record.url?scp=85187989203&partnerID=8YFLogxK

U2 - 10.1021/acs.nanolett.4c00282

DO - 10.1021/acs.nanolett.4c00282

M3 - Article

SN - 1530-6984

VL - 24

SP - 3744

EP - 3749

JO - Nano Letters

JF - Nano Letters

IS - 12

ER -