Direct imaging of surface plasmon polariton dispersion in gold and silver thin films

Ives, Megan; Autry, Travis M.; Cundiff, Steven T.; Nardin, Gaël

doi:10.1364/josab.33.000c17

Cited by 6 publications

(7 citation statements)

References 21 publications

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“…In turn, this tunability could be used to improve the performance of devices for a variety of applications, such as perfect absorbers, photovoltaics, hydrogen storage, metallurgy, catalysis, and electrocatalysis . However, in contrast to the well‐investigated dispersion relation of pure noble metals (Ag and Au), the dispersion of SPPs for Ag–Au alloys has rarely been explored . Additionally, the correlations between the effect of alloying on the optical dispersion relation, the threshold of the interband transition, and the new material's band structure are still not well understood.…”

mentioning

confidence: 99%

Band Structure Engineering by Alloying for Photonics

Gong

Kaplan

Benson

et al. 2018

Advanced Optical Materials

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at deep sub-wavelengths, [2] leading to a variety of applications including nanolasers, [3] sensors, [4] bioimaging, [5] surfaceenhanced Raman spectroscopy, [6,7] color displays, [8] and others. [9][10][11][12] To improve the performance of today's photonic systems, researchers have extensively investigated the fundamental relation between the wave vector and energy of an SPP wave-named dispersion relation. This quantity describes the propagation of light within a material (i.e., medium), extremely relevant for the abovementioned optical devices. Therefore, understanding the dispersion relation can allow the design of optical materials with superior response, ranging from 2D van der Waals to oxides and metals. Concerning 2D materials, it can uncover the origin of tunable polaritons in hyperbolic metamaterials based on graphene and hexagonal boron nitride (h-BN), which is due to the hybridization of SPP and surface phonon polaritons. [13] As another example, by utilizing the band-edge mode of the dispersion relation in metallic nanocavities, [3] lasing with a 200 times enhancement of the spontaneous emission rate of the dye has been reached. [14] As a class of emerging photonic materials, noble metal alloys with permittivity and localized surface plasmon resonances not achievable by pure metals [9,15,16] have been proposed as alternative candidates for plasmonics [12,[17][18][19][20] because of their tunable dielectric functions, which make it possible to engineer the alloy composition to attain optical properties that will meet desired resonances. In turn, this tunability could be used to Surface plasmon polaritons (SPPs) enable the deep subwavelength confinement of an electromagnetic field, which can be used in optical devices ranging from sensors to nanoscale lasers. However, the limited number of metals that satisfy the required boundary conditions for SPP propagation in a metal/dielectric interface severely limits its occurrence in the visible range of the electromagnetic spectrum. We introduce the strategy of engineering the band structure of metallic materials by alloying. We experimentally and theoretically establish the control of the dispersion relation in Ag-Au alloys by varying the film chemical composition. Through X-ray photoelectron spectroscopy (XPS) measurements and partial density-of-states calculations we deconvolute the d band contribution of the density-of-states from the valence band spectrum, showing that the shift in energy of the d band follows the surface plasmon resonance change of the alloy. Our density functional theory calculations of the alloys band structure predict the same variation of the threshold of the interband transition, which is in very good agreement with our optical and XPS experiments. By elucidating the correlation between the optical behavior and band structure of alloys, we anticipate the fine control of the optical properties of metallic materials beyond pure metals. Band Structure EngineeringThe ORCID identification number(s) for the author(s) of this article can b...

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mentioning

confidence: 99%

Band Structure Engineering by Alloying for Photonics

Gong

Kaplan

Benson

et al. 2018

Advanced Optical Materials

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“…By this, we achieve two goals -first, as also used in Refs. [4][5][6][7][8], the sample is simultaneously probed by the many plane-waves making up the converging beam and having an angular span of 10 degrees (in air). Using Snell's law, this is translated to a range of incident angle of 41°-48° with respect to the sample.…”

Section: Methodsmentioning

confidence: 99%

“…Taking advantage of the spatial-interrogation capabilities, we measured the SPP dispersion curves of metalstrip waveguides and demonstrated that our method allows local measurement of waveguides which are as narrow as 3 µm. Like previous Fourier-space imaging methods used for dispersion measurements [4][5][6][7][8][9], our method can be used for broadband, high-resolution and real-time sensing applications. However, in addition, it permits spatial discrimination of several microns and mapping of spatially-inhomogeneous structures, by lateral scanning over the interrogated area.…”

Section: Dispersion Of Plasmonic Waveguidesmentioning

confidence: 99%

“…In order to measure the SPP resonance and its shift under material changes, two approaches are possible -either a broad-spectrum beam is reflected off the metallic surface at a fixed angle (spectral interrogation mode), or a monochromatic collimated beam is used and the reflected intensity is measured, while the angle of incidence is scanned (angular interrogation mode). It was shown in the past that by using Fourier-space (far-field) imaging in conjunction with the Kretschmann-Raether configuration, the two approaches can be unified to obtain the spectral and angular dependence of the plasmon resonance, in a single-shot measurement [4][5][6][7][8]. Alternatively, it was recently demonstrated [9] that similar Fourier-plane single-shot measurements can also be achieved by the use of a half-ball prism positioned on top of the sample.…”

Section: Introductionmentioning

confidence: 99%

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Spatially resolved measurement of plasmon dispersion using Fourier-plane spectral imaging

Ohad¹,

Akulov²,

Granot³

et al. 2018

Photon. Res.

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We show that Fourier-plane imaging in conjunction with the Kretschmann-Raether configuration can be used for measuring polariton dispersion with spatial discrimination of the sample, over the whole visible spectral range. We demonstrate the functionality of our design on several architectures, including plasmonic waveguides, and show that our new design enables the measurement of plasmonic dispersion curves of spatially-inhomogeneous structures with features as small as 3µm, in a single shot.or spectral interrogation, more information is obtained and can be fitted numerically to extract refractive-index changes in the sample. Finally, the possibility to measure the plasmon dispersion in a simple and robust manner can also be used to extract the wavelength-dependent refractive index of an interrogated material, as used in SPP ellipsometry.Here we demonstrate that the concept of Fourier-plane imaging can be further expanded to allow for spatially-resolved dispersion measurements in planar samples supporting surface plasmons. We show that by shaping the illumination beam and incorporating real-space imaging in the optical setup, pre-and post-selection of the interrogated area can be obtained. Therefore, our new optical design offers hybrid functionality and combines the high sensitivity of the broadband dispersion measurements with the imaging capabilities of SPR-imaging techniques. Our measurements show that the lateral detection resolution is high enough to acquire SPP dispersion curves in structures as small as 3µm.

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“…Moreover, in the presence of magnified-field environments, charge oscilltions at metals surfaces couple strongly with the EM field in its immediate dielectric vicinity, producing surface plasmon polaritons (SPP) which travel along the interface of metals and dielectrics. 136 Recent work has shown gold-film structures under optical illumination result in SPPs with evanescent field-scales of up to ~50 nm reach that can couple strongly with 2D quantum wells as far as 20 nms away, leading to either enhancement or drop in exciton radiation efficiency depending the coupling with the SPPs. 137 In our case, being atomically proximal to the MoS2 layer, SPPs (if generated by the optical illumination) can potentially couple strongly with the various excitonic species or act as a channel for hot carrier injection into the MoS2.…”

Section: 2: Experimental Details and Resultsmentioning

confidence: 99%

Tunable electronic and optical properties of layered 2D materials

Rubin¹

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Direct imaging of surface plasmon polariton dispersion in gold and silver thin films

Cited by 6 publications

References 21 publications

Band Structure Engineering by Alloying for Photonics

Band Structure Engineering by Alloying for Photonics

Spatially resolved measurement of plasmon dispersion using Fourier-plane spectral imaging

Tunable electronic and optical properties of layered 2D materials

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