Ultrafast Spectroscopy of Graphene-Protected Thin Copper Films

© 2016 American Chemical Society. We studied by broad-band pump-probe spectroscopy the ultrafast optical response of thin copper films covered by a monolayer of graphene. It is demonstrated that graphene protection does not alter the thermo-modulational nonlinearity of copper in the whole visible range. Also, we provide a quantitative validation of a theoretical model for this optical nonlinearity, derived from a semiclassical description of electron thermalization dynamics and subsequent modulation of copper dielectric function from 450 to 700 nm wavelength. Our results extend to the nonlinear domain the capability of graphene-protected copper nanolayers to serve as a low cost optical grade material, with major potential impact on nonlinear plasmonics and metamaterials

Graphene plasmonics

Two rich and vibrant fields of investigation, graphene physics and plasmonics, strongly overlap. Not only does graphene possess intrinsic plasmons that are tunable and adjustable, but a combination of graphene with noble-metal nanostructures promises a variety of exciting applications for conventional plasmonics. The versatility of graphene means that graphene-based plasmonics may enable the manufacture of novel optical devices working in different frequency ranges, from terahertz to the visible, with extremely high speed, low driving voltage, low power consumption and compact sizes. Here we review the field emerging at the intersection of graphene physics and plasmonics.Comment: Review article; 12 pages, 6 figures, 99 references (final version available only at publisher's web site

Graphene-protected copper and silver plasmonics.

Plasmonics has established itself as a branch of physics which promises to revolutionize data processing, improve photovoltaics, and increase sensitivity of bio-detection. A widespread use of plasmonic devices is notably hindered by high losses and the absence of stable and inexpensive metal films suitable for plasmonic applications. To this end, there has been a continuous search for alternative plasmonic materials that are also compatible with complementary metal oxide semiconductor technology. Here we show that copper and silver protected by graphene are viable candidates. Copper films covered with one to a few graphene layers show excellent plasmonic characteristics. They can be used to fabricate plasmonic devices and survive for at least a year, even in wet and corroding conditions. As a proof of concept, we use the graphene-protected copper to demonstrate dielectric loaded plasmonic waveguides and test sensitivity of surface plasmon resonances. Our results are likely to initiate wide use of graphene-protected plasmonics.SAIT GRO Program and EPSRC grant EP/K011022/1. Y.-J. Kim was supported by the Global Research Laboratory Program (2011-0021972) of the Ministry of Education, Science and Technology, Korea. The support of the Graphene Flagship project is acknowledged

Layered material platform for surface plasmon resonance biosensing

Plasmonic biosensing has emerged as the most sensitive label-free technique to detect various molecular species in solutions and has already proved crucial in drug discovery, food safety and studies of bio-reactions. This technique relies on surface plasmon resonances in ~50 nm metallic films and the possibility to functionalize the surface of the metal in order to achieve selectivity. At the same time, most metals corrode in bio-solutions, which reduces the quality factor and darkness of plasmonic resonances and thus the sensitivity. Furthermore, functionalization itself might have a detrimental effect on the quality of the surface, also reducing sensitivity. Here we demonstrate that the use of graphene and other layered materials for passivation and functionalization broadens the range of metals which can be used for plasmonic biosensing and increases the sensitivity by 3-4 orders of magnitude, as it guarantees stability of a metal in liquid and preserves the plasmonic resonances under biofunctionalization. We use this approach to detect low molecular weight HT-2 toxins (crucial for food safety), achieving phase sensitivity~0.5 fg/mL, three orders of magnitude higher than previously reported. This proves that layered materials provide a new platform for surface plasmon resonance biosensing, paving the way for compact biosensors for point of care testing

Extraordinary absorption of sound in porous lamella-crystals

We present the design of a structured material supporting complete absorption of sound with a broadband response and functional for any direction of incident radiation. The structure which is fabricated out of porous lamellas is arranged into a low-density crystal and backed by a reflecting support. Experimental measurements show that strong all-angle sound absorption with almost zero reflectance takes place for a frequency range exceeding two octaves. We demonstrate that lowering the crystal filling fraction increases the wave interaction time and is responsible for the enhancement of intrinsic material dissipation, making the system more absorptive with less material.The work was supported by the Spanish Ministry of Science and Innovation and European Union FEDER through project FIS2011-29734-C02-01. J.C. gratefully acknowledges financial support from the Danish Council for Independent Research and a Sapere Aude grant (12-134776). V. R. G. gratefully acknowledges financial support from the ''Contratos Post-Doctorales Campus Excelencia Internacional'' UPV CEI-01-11.Christensen, J.; Romero García, V.; Picó Vila, R.; Cebrecos Ruiz, A.; Garcia De Abajo, FJ.; Mortensen, NA.; Willatzen, M.... (2014). Extraordinary absorption of sound in porous lamella-crystals. Scientific Reports. 4(4674). https://doi.org/10.1038/srep04674S44674Mei, J. et al. Dark acoustic metamaterials as super absorbers for low-frequency sound. Nat. Commun. 3, 756 (2012).Leroy, V., Strybulevych, A., Scanlon, M. G. & Page, J. Transmission of ultrasound through a single layer of bubbles. Eur. Phys. J. E 29, 123 (2009).Leroy, V., Bretagne, A., Fink, M. H. W., Tabeling, P. & Tourin, A. Design and characterization of bubble phononic crystals. Appl. Phys. Lett. 95, 171904 (2009).Thomas, E. L. Applied physics: Bubbly but quiet. Nature 462, 990 (2009).Romero-García, V., Sánchez-Pérez, J. V. & Garcia-Raffi, L. M. Tunable wideband bandstop acoustic filter based on two-dimensional multiphysical phenomena periodic systems. J. Appl. Phys. 110, 014904 (2011).Garcia-Chocano, V. M., Cabrera, S. & Sanchez-Dehesa, J. Broadband sound absorption by lattices of microperforated cylindrical shells. Appl. Phys. Lett. 101, 184101 (2012).Kushwaha, M. S., Halevi, P., Dobrzynski, L. & Djafari-Rouhani, B. Acoustic band structure of periodic elastic composites. Phys. Rev. Lett. 71, 2022 (1993).Vasseur, J. O. et al. Experimental and Theoretical Evidence for the Existence of Absolute Acoustic Band Gaps in Two-Dimensional Solid Phononic Crystals. Phys. Rev. Lett. 86, 3012 (2001).Liu, Z. et al. Locally Resonant Sonic Materials. Science 289, 1734 (2000).Christensen, J., Martin-Moreno, L. & Garcia-Vidal, F. J. All-angle blockage of sound by an acoustic double-fishnet metamaterial. Appl. Phys. Lett. 97, 134106 (2010).Botten, L. C., Craig, M. S., McPhedran, R. C., Adams, J. L. & Andrewartha, J. R. The finitely conducting lamellar diffraction grating. Optica Acta 28, 1087 (1981).McPhedran, R. C., Botten, L. C., Craif, M. S., Neviere, M. & Maystre, D. Lossy lamellar gratings in the quasistatic limit. Optica Acta 29, 289 (1982).Kravets, V. G., Schedin, F. & Grigorenko, A. N. Plasmonic blackbody: Almost complete absorption of light in nanostructured metallic coatings. Phys. Rev. B 78, 205405 (2008).Sondergaard, T. et al. Plasmonic black gold by adiabatic nanofocusing and absorption of light in ultra-sharp convex grooves. Nat. Commun. 3, 969 (2012).Clapham, P. B. & Hurtley, M. C. Reduction of Lens Reflexion by the Moth Eye Principle. Nature Vol. 244, 281 (1973).Garcia-Vidal, F. J., Pitarke, J. M. & Pendry, J. B. Effective Medium Theory of the Optical Properties of Aligned Carbon Nanotubes. Phys. Rev. Lett. 78, 4289 (1997).Yang, Z., Ci, L., Bur, J. A., Lin, S. & Ajayan, P. M. Experimental Observation of an Extremely Dark Material Made By a Low-Density Nanotube Array. Nano Lett. 8, 446 (2008).Garcia-Vidal, F. J. Metamaterials: Towards the dark side. Nat. Photonics 2, 215 (2008).Mizunoa, K. et al. A black body absorber from vertically aligned single-walled carbon nanotubes. Proc. Natl. Acad. Sci. USA 106, 6044 (2009).Lidorkis, E. & Ferrari, A. C. Photonics with Multiwall Carbon Nanotube Arrays. ACS Nano 3, 1238 (2009).Beenakker, C. W. J. & Brouwer, P. W. Distribution of the reflection eigenvalues of a weakly absorbing chaotic cavity. Physica E 9, 463 (2001).Lafarge, D., Lemarinier, P., Allard, J. F. & Tarnow, V. Dynamic compressibility of air in porous structures at audible frequencies. J. Acoust. Soc. Am. 102, 1995 (1997), With the macroscopic parameters: ϕ = 0.94, α∞ = 1, σ = 20000 Nm−4s and Λ = Λ′ = 0.41 μm.García de Abajo, F. J. Colloquium: Light scattering by particle and hole arrays. Rev. Mod. Phys. 79, 1267–1290 (2007)

Layered material platform for surface plasmon resonance biosensing

Abstract: Plasmonic biosensing has emerged as the most sensitive label-free technique to detect various molecular species in solutions and has already proved crucial in drug discovery, food safety and studies of bio-reactions. This technique relies on surface plasmon resonances in ~50 nm metallic films and the possibility to functionalize the surface of the metal in order to achieve selectivity. At the same time, most metals corrode in bio-solutions, which reduces the quality factor and darkness of plasmonic resonances and thus the sensitivity. Furthermore, functionalization itself might have a detrimental effect on the quality of the surface, also reducing sensitivity. Here we demonstrate that the use of graphene and other layered materials for passivation and functionalization broadens the range of metals which can be used for plasmonic biosensing and increases the sensitivity by 3-4 orders of magnitude, as it guarantees stability of a metal in liquid and preserves the plasmonic resonances under biofunctionalization. We use this approach to detect low molecular weight HT-2 toxins (crucial for food safety), achieving phase sensitivity~0.5 fg/mL, three orders of magnitude higher than previously reported. This proves that layered materials provide a new platform for surface plasmon resonance biosensing, paving the way for compact biosensors for point of care testing

Octave-wide photonic band gap in three-dimensional plasmonic Bragg structures and limitations of radiative coupling

Radiative coupling between oscillators is one of the most fundamental subjects of research in optics, where particularly a Bragg-type arrangement is of interest and has already been applied to atoms and excitons in quantum wells. Here we explore this arrangement in a plasmonic structure. We observe the emergence of an octave-wide photonic band gap in the optical regime. Compared with atomic or excitonic systems, the coupling efficiency of the particle plasmons utilized here is several orders of magnitude larger and widely tunable by changing the size and geometry of the plasmonic nanowires. We are thus able to explore the regime where the coupling distance is even limited by the large radiative decay rate of the oscillators. This Bragg-stacked coupling scheme will open a new route for future plasmonic applications such as far-field coupling to quantum emitters without quenching, plasmonic cavity structures and plasmonic distributed gain schemes for spasers

Raman spectroscopy as a versatile tool for studying the properties of graphene.

Raman spectroscopy is an integral part of graphene research. It is used to determine the number and orientation of layers, the quality and types of edge, and the effects of perturbations, such as electric and magnetic fields, strain, doping, disorder and functional groups. This, in turn, provides insight into all sp(2)-bonded carbon allotropes, because graphene is their fundamental building block. Here we review the state of the art, future directions and open questions in Raman spectroscopy of graphene. We describe essential physical processes whose importance has only recently been recognized, such as the various types of resonance at play, and the role of quantum interference. We update all basic concepts and notations, and propose a terminology that is able to describe any result in literature. We finally highlight the potential of Raman spectroscopy for layered materials other than graphene

Non-Polaritonic Effects in Cavity-Modified Photochemistry (dataset)

This is the dataset (all in .csv format) for the manuscript "Non-Polaritonic Effects in Cavity-Modified Photochemistry" published in Advanced Materials in 2023.This is the dataset used for the Thomas et al. (2023) article "Non-Polaritonic Effects in Cavity-Modified Photochemistry" published in Advanced Materials.European Research Council (ERC)Engineering and Physical Sciences Research Council (EPSRC)Graphene Flagship programme, Core