Probing the quantum tunneling limit of plasmonic enhancement by third harmonic generation.

Metal nanostructures provide extreme focusing of optical energy that is limited fundamentally by quantum tunneling. We directly probe the onset of the quantum tunneling regime observed by a sharp reduction in the local field intensity in subnanometer self-assembled monolayer gaps using third harmonic generation. Unlike past works that have inferred local limits from far-field spectra, this nonlinear measurement is sensitive to the near-field intensity as the third power. We calculate the local field intensity using a quantum corrected model and find good quantitative agreement with the measured third harmonic. The onset of the quantum regime occurs for double the gap size of past studies because of the reduced barrier height of the self-assembled monolayer, which will be critical for many applications of plasmonics, including nonlinear optics and surface enhanced Raman spectroscopy.

[1]  Naomi J Halas,et al.  Nanosphere arrays with controlled sub-10-nm gaps as surface-enhanced raman spectroscopy substrates. , 2005, Journal of the American Chemical Society.

[2]  Mark A. Reed,et al.  Mechanism of electron conduction in self-assembled alkanethiol monolayer devices , 2003 .

[3]  David R. Smith,et al.  Film-coupled nanoparticles by atomic layer deposition: Comparison with organic spacing layers , 2014 .

[4]  Michel Orrit,et al.  Third-harmonic generation from single gold nanoparticles. , 2005, Nano letters.

[5]  Emil Prodan,et al.  Quantum description of the plasmon resonances of a nanoparticle dimer. , 2009, Nano letters.

[6]  A. Borisov,et al.  Robust subnanometric plasmon ruler by rescaling of the nonlocal optical response. , 2013, Physical review letters.

[7]  I. Sharp,et al.  Phosphonic Acid Adsorbates Tune the Surface Potential of TiO2 in Gas and Liquid Environments. , 2014, The journal of physical chemistry letters.

[8]  Nikolay I. Zheludev,et al.  Ultrafast active plasmonics: transmission and control of femtosecond plasmon signals , 2008 .

[9]  Romain Quidant,et al.  Plasmon nano-optical tweezers , 2011 .

[10]  Stefan A. Maier,et al.  Quantum Plasmonics , 2016, Proceedings of the IEEE.

[11]  P. Nordlander.  Molecular Tuning of Quantum Plasmon Resonances , 2014, Science.

[12]  Jennifer A. Dionne,et al.  Observation of quantum tunneling between two plasmonic nanoparticles. , 2013, Nano letters.

[13]  R. Gelfand,et al.  Effect of surface roughness on self-assembled monolayer plasmonic ruler in nonlocal regime. , 2014, Optics express.

[14]  Wei Bao,et al.  Mapping Local Charge Recombination Heterogeneity by Multidimensional Nanospectroscopic Imaging , 2012, Science.

[15]  Annemarie Pucci,et al.  Angstrom-scale distance dependence of antenna-enhanced vibrational signals. , 2012, ACS nano.

[16]  Stefan A Maier,et al.  Plasmonics: The benefits of darkness. , 2009, Nature materials.

[17]  Javier Aizpurua,et al.  Bridging quantum and classical plasmonics with a quantum-corrected model , 2012, Nature Communications.

[18]  A. Roberts,et al.  The dark side of plasmonics. , 2013, Nano letters.

[19]  Biao Wu,et al.  Effects of quantum tunneling in metal nanogap on surface-enhanced Raman scattering , 2009, 0901.0607.

[20]  Reuven Gordon,et al.  Single molecule directivity enhanced Raman scattering using nanoantennas. , 2012, Nano letters.

[21]  Lukas Novotny,et al.  Optical frequency mixing at coupled gold nanoparticles. , 2007, Physical review letters.

[22]  R. T. Hill,et al.  Probing the Ultimate Limits of Plasmonic Enhancement , 2012, Science.

[23]  Jérémy Butet,et al.  Ultrasensitive optical shape characterization of gold nanoantennas using second harmonic generation. , 2013, Nano letters.

[24]  Sang‐Hyun Oh,et al.  Ultrasmooth Patterned Metals for Plasmonics and Metamaterials , 2009, Science.

[25]  Steve Blair,et al.  Third-harmonic generation from arrays of sub-wavelength metal apertures. , 2009, Optics express.

[26]  Lin Wu,et al.  Quantum Plasmon Resonances Controlled by Molecular Tunnel Junctions , 2014, Science.

[27]  Romain Quidant,et al.  Thermo‐plasmonics: using metallic nanostructures as nano‐sources of heat , 2013 .

[28]  A. Borisov,et al.  Quantum plasmonics: nonlinear effects in the field enhancement of a plasmonic nanoparticle dimer. , 2012, Nano letters.

[29]  Lin Wu,et al.  Fowler-nordheim tunneling induced charge transfer plasmons between nearly touching nanoparticles , 2013, 2013 Abstracts IEEE International Conference on Plasma Science (ICOPS).

[30]  Jeremy J. Baumberg,et al.  Revealing the quantum regime in tunnelling plasmonics , 2012, Nature.

[31]  Aftab Ahmed,et al.  Plasmon hybridization for enhanced nonlinear optical response. , 2012, Optics express.

[32]  Reuven Gordon,et al.  Directivity enhanced Raman spectroscopy using nanoantennas. , 2011, Nano letters.

[33]  Jérémy Butet,et al.  Augmenting second harmonic generation using Fano resonances in plasmonic systems. , 2013, Nano letters.

[34]  David R. Smith,et al.  Plasmon ruler with angstrom length resolution. , 2012, ACS nano.