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Register a new userA surface plasmon platform for angle-resolved chiral sensing
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Chiral sensitive techniques have been used to probe the fundamental symmetries of the universe, study biomolecular structures, and even develop safe drugs. As chiral signals are inherently weak and often suppressed by large backgrounds, different techniques have been proposed to overcome the limitations of traditionally used chiral polarimetry. Here, we propose an angle-resolved chiral surface plasmon resonance (CHISPR) scheme that can detect the absolute chirality (handedness and magnitude) of a chiral sample and is sensitive to both the real and imaginary part of a chiral samples refractive index. We present analytical results and numerical simulations of CHISPR measurements, predicting signals in the mdeg range for chiral samples of <100nm thickness at visible wavelengths. Moreover, we present a theoretical analysis that clarifies how our far-field measurements elucidate the underlying physics. This CHISPR protocol does not require elaborate fabrication and has the advantage of being directly implementable on existing surface plasmon resonance instrumentation.
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We use mono-crystalline gold platelets with ultra-smooth surfaces and superior plasmonic properties to investigate the formation of interference patterns caused by surface plasmon polaritons (SPPs) with scattering-type scanning near-field microscopy (s-SNOM) at 521~nm and 633~nm. By applying a Fourier analysis approach, we can identify and separate several signal channels related to SPPs launched and scattered by the AFM tip and the edges of the platelet. Especially at the excitation wavelength of 633~nm, we can isolate a region in the center of the platelets where we find only contributions of SPPs which are launched by the tip and reflected at the edges. These signatures are used to determine the SPP wavelength of $lambda_{SPP}=606$ nm in good agreement with theoretical predictions. Furthermore, we were still able to measure SPP signals after 20~$upmu$m propagation, which demonstrates impressively the superior plasmonic quality of these mono-crystalline gold platelets.
We propose a plasmonic device consisting of a concentric ring grating acting as an efficient tool for directional launching and detection of surface plasmon-polaritons (SPPs). Numerical simulations and optical characterizations are used to study the fabricated structured gold surface. We demonstrate that this circularly symmetrical plasmonic device provides an efficient interface between free space radiation and SPPs. This structure offers an excellent platform for the study of hybrid plasmonics in general and of plasmon-emitter couplings in particular, such as those occurring when exciting dye molecules placed inside the ring. As illustrated in this work, an interesting property of the device is that the position of excitation determines the direction of propagation of the SPPs, providing a flexible mean of studying their interactions with molecules or dipole-like emitters placed on the surface.
We present a simplified yet sophisticated variation to localised surface plasmon resonance spectroscopy, which makes use of naked or non-functionalised, nanoparticle templates. These nanoparticle templates, produced with a rapid and scalable process, namely laser annealing, were used as a highly sensitive surface sensor to monitor the adsorption of both metallic lead and a lead salt from aqueous solutions, showing a measurable optical response due to a surface abundance of lead as low as 100 ppm from 0.3 ml of Pb2SO4 solutions, with concentrations less than 20 ppm. This proposed method enables the end user to rapidly assess the surface abundance of lead from a simple optical reflectance measurement and could serve as a platform for in situ analysis within water filtration and cleaning systems.
The electrodynamics of Weyl semimetals (WSMs) is an extension of Maxwells theory where in addition to field strength tensor $F_{mu u}$, an axion field enters the theory which is parameterized by a four-vector $b^mu=(b_0,bf b)$. In the tilted Weyl matter (TWM) an additional set of parameters ${bfzeta}=(zeta_x,zeta_y,zeta_z)$ enter the theory that can be encoded into the metric of the spacetime felt by electrons in TWM. This allows an extension of Maxwells electrodynamics that describes electric and magnetic fields in TWMs and tilted Dirac material (TDM) when $b^mu=0$. The tilt parameter $bfzeta$ appearing as off-diagonal metric entries mixing time and space components mingles $bf E$ and $bf B$ fields whereby modifies the inhomogeneous Maxwells equations. Surface plasmon polariton (SPP) in these systems describes the propagation of electromagnetic waves at the {it interface of two different spacetime geometries}. In the case of TDM, we find a characteristic dependence of SPP spectrum on the tilt parameter $zeta$ which can be used map $zeta$ from SPP measurements. In the case of TWM, depending on whether the interface with vacuum supports a Fermi arc or not, and whether the propagation direction is along the Fermi arc or transverse to it, we find many unusual spectral features for SPP modes. Our detailed study of the dependence of SPP spectra on the arrangements of three vectors $(bf b, q,zeta)$, the first two of which are at our control, can be utilized to map the tilt characteristics and Fermi arc characteristics from SPP measurements.
This paper proposes a low-profile and highly efficient endfire radiating travelling-wave antenna based on spoof surface plasmon polaritons (SSPPs) transmission line. The aperture is approximately $0.32lambda_0times0.01lambda_0$ where $lambda_0$ is the space wavelength at the operational frequency 8 GHz. This antenna provides an endfire radiation beam within 7.5-8.5 GHz. The maximum gain and total efficiency reaches 9.2 dBi and $96%$, respectively. In addition to the endfire operation, it also provides a beam scanning functionality within 9-12 GHz. Measurement results are finally given to validate the proposed SSPPs antenna.
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