Surface and bulk contributions to the second-order nonlinear optical response of a gold film

Wang, Fu Xiang; Rodríguez, Francisco; Albers, Willem M.; Ahorinta, Risto; Sipe, J. E.; Kauranen, Martti

doi:10.1103/physrevb.80.233402

Cited by 250 publications

(256 citation statements)

References 30 publications

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“…Indeed, this component is known to be the main surface contribution to SHG from metallic nanoparticles. 41,42 Recent experimental work on the SHG from spherical silver nanoparticles has further demonstrated that the nnn component represents the dominant contribution to the second harmonic signal and other contributions play only a minor role in the SHG from plasmonic nanostructures. 43 Figure 2 shows the second harmonic near-field intensity when the fundamental wavelength is (a) λ = 800 nm and (b) λ = 950 nm.…”

Section: * S Supporting Informationmentioning

confidence: 99%

Augmenting Second Harmonic Generation Using Fano Resonances in Plasmonic Systems

2013

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Significant augmentation of second harmonic generation using Fano resonances in plasmonic heptamers made of silver is theoretically and experimentally demonstrated. The geometry is engineered to simultaneously produce a Fano resonance at the fundamental wavelength, resulting in a strong localization of the fundamental field close to the system, and a higher order scattering peak at the second harmonic wavelength. These results illustrate the versatility of Fano resonant structures to engineer specific optical responses both in the linear and nonlinear regimes thus paving the way for future investigations on the role of dark modes in nonlinear and quantum optics. 1 One such property is the generation of hot spots, whose presence in nanostructures, such as optical antennae, is promising for applications in nonlinear optics, since they require a strong electric near-field.2 Recent studies have reported the observation of different nonlinear optical phenomena in such nanosystems, like, for example, second harmonic generation (SHG), 3 multiphoton luminescence, 4,5 third harmonic generation, 6,7 higher harmonic generation, 8 and four-wave mixing. 9 SHG is significantly dependent on the symmetry of both the material being used and the structure being studied and therefore is a sensitive tool for characterizing plasmonic structures.10−13 SHG from centrosymmetric materials is due to the breaking of inversion symmetry at their surfaces and is therefore used as a surface probe.14 In recent years, strong SHG has been observed in metallic nanostructures such as sharp metallic tips, 15 multiple resonant nanostructures, 16,17 split-ring resonators, 18 metamaterials 19,20 and nanocups, 21 underlining the fast growing interest in the area of nonlinear plasmonics. 22,23 Efficient SHG requires the presence of strong SHG sources, that is, nonlinear polarization currents oscillating at the second harmonic frequency, at the nanostructure surface as well as an efficient scattering of the SHG signal into the far-field. Several strategies have been developed to enhance SHG from metallic nanostructures including using multiple resonances at both the fundamental and the second harmonic wavelengths, 16 breaking the centrosymmetry using noncentrosymmetric nanostructures 20 and even enhancing the electric fields using nanogaps. 24 However, the efficiency of SHG is restricted by two fundamental classes of losses that electromagnetic waves suffer in such metallic structures, namely radiative "losses" like optical scattering and nonradiative losses like the generation of heat. 25 Therefore, to increase the detected SHG in the far-field the structures must decrease the radiative losses at the fundamental wavelength while increasing them at the second harmonic wavelength and at the same time increase the near-field at the fundamental wavelength. Because the SHG yield increases as the square of the fundamental field intensity, 26 a higher near-field at the fundamental is required to increase the near-field at the second harmonic. The wid...

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Section: * S Supporting Informationmentioning

confidence: 99%

Augmenting Second Harmonic Generation Using Fano Resonances in Plasmonic Systems

2013

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“…This results in a high spin rotation efficiency of 70% at the interface, where the transmitted (reflected) current loses its orthogonal spin component and becomes polarized parallel (antiparallel) to the Fe magnetization. [37] Here we neglect the bulk quadrupole contribution which was shown to be small in Au [38].…”

Section: H Y S I C a L R E V I E W L E T T E R Smentioning

confidence: 99%

Femtosecond Spin Current Pulses Generated by the Nonthermal Spin-Dependent Seebeck Effect and Interacting with Ferromagnets in Spin Valves

Alekhin¹,

Razdolski²,

Ilin³

et al. 2017

Phys. Rev. Lett.

104

120

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Using the sensitivity of optical second harmonic generation to currents, we demonstrate the generation of 250-fs long spin current pulses in Fe=Au=Fe=MgOð001Þ spin valves. The temporal profile of these pulses indicates ballistic transport of hot electrons across a sub-100 nm Au layer. The pulse duration is primarily determined by the thermalization time of laser-excited hot carriers in Fe. Considering the calculated spin-dependent Fe=Au interface transmittance we conclude that a nonthermal spin-dependent Seebeck effect is responsible for the generation of ultrashort spin current pulses. The demonstrated rotation of spin polarization of hot electrons upon interaction with noncollinear magnetization at Au=Fe interfaces holds high potential for future spintronic devices. DOI: 10.1103/PhysRevLett.119.017202 Optimization and control of spin currents (SC) and their interaction with magnetic constituents in heterostructures on a femtosecond time scale is key for future terahertz spintronics applications. Although electronic transport through a ferromagnet (FM), as described by Mott's two current model [1], generates a spin-polarized current, its density is intrinsically limited by Joule losses. The discovery of the spin-dependent Seebeck effect (SdSE), where thermal gradients over a bulk FM [2] or across an interface to a normal metal [3] generate SCs, opened a path towards overcoming such limitations. Indeed, shortlived thermal gradients can produce short (∼100 ps) SC pulses at densities exceeding the static Joule limit, as recently demonstrated upon laser excitation of spin-valve structures [4].Creating highly energetic electrons [5][6][7][8][9], femtosecond laser excitation is promising for SC pulse generation on subpicosecond time scales, before the electron-electron [9] and electron-lattice [8] equilibration is reached.

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“…Since its discovery in 1961 5 the importance of SHG has grown, because of its sensitivity to space symmetry, making SHG an extremely versatile tools for studying many kinds of surfaces [6][7][8][9][10] , superlattices 11 and interfaces 10,[12][13][14] . Nowadays this technique is also used for characterizing systems like interfaces of nanocrystals 15 or as a probe for molecular chirality in polymers 16,17 and nanotubes 18 .…”

Section: Introductionmentioning

confidence: 99%

Ab initiosecond-order nonlinear optics in solids: Second-harmonic generation spectroscopy from time-dependent density-functional theory

2010

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We present in detail the formulation of the ab initio theory we have developed for the calculation of the macroscopic second-order susceptibility χ (2) . We find a general expression for χ (2) valid for any fields, containing the ab initio relation between the microscopic and macroscopic formulation of the second-order responses. We consider the long wavelength limit and we develop our theory in the Time-Dependent Density-Functional Theory framework. This allows us to include straightforwardly many-body effects such as crystal local-field and excitonic effects. We compute the Second-Harmonic Generation spectra for the cubic semiconductors SiC, AlAs and GaAs and starting from the Independent-Particle Approximation for χ (2) , we include quasiparticle effects via the scissors operator, crystal local-field and excitonic effects. In particular, we consider two different types of kernels: the ALDA and the "long-range" kernel. We find good agreement with other theoretical calculations and experiments presented in literature, showing the importance of very accurate description of the many-body interactions.

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Surface and bulk contributions to the second-order nonlinear optical response of a gold film

Cited by 250 publications

References 30 publications

Augmenting Second Harmonic Generation Using Fano Resonances in Plasmonic Systems

Augmenting Second Harmonic Generation Using Fano Resonances in Plasmonic Systems

Femtosecond Spin Current Pulses Generated by the Nonthermal Spin-Dependent Seebeck Effect and Interacting with Ferromagnets in Spin Valves

Ab initiosecond-order nonlinear optics in solids: Second-harmonic generation spectroscopy from time-dependent density-functional theory

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