Multiple Surface-plasmon-polariton Waves Research Articles

On the Propagation of Multiple Surface Plasmon-Polariton Waves by a Triangle Helix Thin Film in Sarid Configuration

Increasing the propagation length of surface plasmon polariton waves has always been a problem in the field of plasmonics. Here, we reported that the surface plasmon polariton waves are multiplied by considering a central metal defect in a dielectric triangle helix thin film using Sarid configuration. The dependence relative phase speed and propagation length of the multiple surface plasmon polariton waves on different structural parameters are investigated. The results showed that the high propagation length up to 236 μm is made available by selecting suitable structural parameters. The localization of surface plasmon polariton waves is proven by the depiction of the time-averaged Poynting vector and local absorption as a function of depth of the structure.

A highly sensitive multiplasmonic sensor using hyperbolic chiral sculptured thin films

Surface plasmon-polariton (SPP) waves guided by an interface of a metal and a hyperbolic chiral sculptured thin film (STF) were theoretically investigated for optical sensing of an analyte. The chiral STF was infiltrated with the analyte to be sensed, and the resulting change in the incidence angle of excitation of the SPP waves in the prism-coupled configuration was computed. The results indicated the potential of this configuration for a plasmonic sensor with sensitivity up to 6000 degrees per refractive index units of the infiltrating fluid in the angular investigation scheme, with multiple SPP waves of the same frequency but different phase speeds, spatial profiles, and sensitivities. The enhancement in the sensitivity is attributed to the high field strength of the SPP waves near the interface. A multiplasmonic sensor is advantageous because of its potential for higher confidence in the measurement of the same analyte.

Multiple surface-plasmon-polariton waves guided by a chiral sculptured thin film grown on a metallic grating

Theoretical and experimental studies were undertaken to investigate the grating-coupled excitation of multiple surface-plasmon-polariton (SPP) waves guided by the periodically corrugated interface of a metal and a chiral sculptured thin film (STF). The rigorous coupled-wave approach was adapted to calculate the absorptance spectrum of a structure comprising a chiral STF atop a rectangular metallic grating when that structure is illuminated by a linearly polarized plane wave whose wavevector lies wholly in the corrugation plane. The incidence direction could be either normal or oblique with respect to the thickness direction of the structure. High-absorptance bands for both s- and p-polarized incident plane waves were found to be correlated with the SPP wavenumbers calculated from the solution of the underlying canonical boundary-value problem, indicating that multiple distinct SPP waves can be excited at a specific frequency. The resistive-heating thermal evaporation technique was used to deposit chiral STFs of zinc selenide on gold gratings made by electron-beam lithography, and transmittance and reflectance spectra of the fabricated structures were measured in a variable-angle spectroscopic system in order to qualitatively validate the theoretical understanding. Several high-absorptance bands were found to be almost unaffected by the number of periods of the chiral STF. The existence of these bands indicated that as many as three distinct SPP waves were excited at a specific frequency in several spectral regimes by s- and/or p-polarized incident light.

Experimental excitation of multiple surface-plasmon-polariton waves and waveguide modes in a one-dimensional photonic crystal atop a two-dimensional metal grating

The excitation of multiple SPP waves as Floquet harmonics was demonstrated in structures fabricated as one-dimensional photonic crystals (PCs) on top of two-dimensional gold gratings. Each period of the PC comprised nine layers of silicon oxynitrides of different compositions, and each PC had either two or three periods. Absorptances for obliquely incident $p$- and $s$-polarized light were measured in the 500--1000-nm wavelength regime and the sharp bands in the absorptance spectra were compared with the solutions of the underlying canonical boundary-value problem. The excitation of multiple surface-plasmon-polariton (SPP) waves as Floquet harmonics was confirmed. The structures demonstrated broadband absorption with overall weak dependences on the incidence angle and the polarization state of the incident light, and has potential application for harvesting solar energy.

Multiplasmonic Optical Sensor Using Sculptured Nematic Thin Films

Fluid-infiltrated sculptured nematic thin films (SNTFs) were modeled using a combination of piecewise uniform approximation technique and Bruggeman formalism. The modeling was then used to exploit surface plasmon-polariton (SPP) waves for optical sensing of the fluid infiltrating the SNTF. The interface of the chosen metal and the SNTF supports multiple SPP waves of the same frequency, thereby, providing multiple angles of incidence in the prism-coupled configuration for optical sensing, offering potential for a higher confidence in measurements and multi-analyte sensing at the same time.

On the propensity of guiding surface-plasmon-polariton waves by the back-contact of an amorphous silicon p-i-n solar cell

The effect of varying the n-layer on the propensity of guiding surface-plasmon-polariton (SPP) waves by the back-contact of a p-i-n solar cell was studied theoretically. The i-layer was assumed to consist of an a-SiGex:H homogeneous layer of bandgap energy 1.3 eV. To determine the SPP waves that can propagate at the metal/multilayer material interface, a canonical boundary-value problem comprising periodically repeated p-i-n semiconductor layers partnering a homogeneous metal was solved for four different n-layers. The canonical problem was formulated to predict both of the TM- and TE-polarized SPP waves that can be guided by the interface. It was found that the configurations that have an amorphous silicon layer partnering the metal have equivalent propensity for guiding TM- and TE-polarized SPP waves by the planar metal/multilayer material interface, although their phase speeds, e-folding distances, and localization are slightly altered. On the other hand, the configuration that has an aluminum zinc oxide partnering the metal has significantly reduced propensity for guiding TE-polarized SPP waves. To examine the excitability of the SPP waves predicted from the canonical problem, one of the considered configurations is incorporated in a practical grating-coupled configuration. Oblique incidence was assumed, and multiple SPP waves were successfully excited. The total absorptance of the p-i-n solar cell shows enhancement at the SPP wave excitation wavelengths.

Errata: Enhancement of light absorption efficiency of amorphous-silicon thin-film tandem solar cell due to multiple surface-plasmon-polariton waves in the near-infrared spectral regime

The reflectances of a thin-film solar cell were computed, using the rigorous coupled-wave approach, as functions of the angle of incidence and the free-space wavelength for illumination by linearly polarized plane waves. A tandem solar cell made of amorphous-silicon alloys was considered. The metallic back-reflector was taken to be periodically corrugated. Both the simple and the compound periodic corrugations of the metallic back-reflector (surface-relief gratings) were investigated. Low-reflectance bands in the reflectance spectrums were correlated with the solutions of the underlying canonical boundary-value problem to delineate the excitation of multiple surface-plasmon-polariton (SPP) waves. For the standard AM1.5 solar irradiance spectrum, we found that the light absorption efficiency in the near-infrared spectral regime can be increased up to 100% when multiple SPP waves of both linear polarization states are excited.

Plasmonic Absorption Enhancement in a Dye-Sensitized Solar Cell Using a Fourier Harmonics Grating

A solid-state dye-sensitized solar cell with back-contact Fourier harmonics (FH) grating was studied theoretically, using the rigorous coupled-wave analysis. The FH grating was found to provide enhanced absorptance and enable efficient multiple surface–plasmon–polariton (SPP) wave excitations. The incident plane wave was considered to be TM-polarized with oblique incidence. The FH gratings were designed to excite multiple SPP waves at desirable wavelengths by solving a canonical boundary value problem. The excitation of SPP waves is indicated by the presence of peaks in the absorptance plots. The FH grating enables light trapping corresponding to the wave vectors of the constituting simple gratings, which may be useful for chemical sensing and communication applications as well.

Multiple excitations of surface-plasmon-polariton waves in an amorphous silicon p-i-n solar cell using Fourier harmonics and compound gratings

In an amorphous silicon p-i-n solar cell, back contact Fourier harmonics (FH) and compound gratings were studied theoretically, using the rigorous coupled-wave analysis. The FH grating was found to enable more efficient multiple surface-plasmon-polariton (SPP) wave excitations compared with a compound grating, while both of them are made of the same constituting simple gratings. The incident plane wave was considered to be TM-polarized. The FH and compound gratings were designed to excite multiple SPP waves at desirable wavelengths by solving a canonical boundary-value problem. The excitation of SPP waves is indicated by the presence of peaks in the absorptance plots. The multiple SPP waves excited by the FH grating were found to increase the external quantum efficiency.

Multiple surface plasmon–polariton waves guided by the interfaceof a metal and a periodically nonhomogeneous magnetic material

The excitation of multiple surface plasmon–polariton (SPP) waves guided by the interface of a homogeneous metal and a periodically nonhomogeneous magnetic material was studied theoretically. The solution of the canonical boundary-value problem indicated that multiple SPP waves of different polarization states, phase speeds, spatial profiles, and attenuation rates can be guided by the interface of the metal and the periodically nonhomogeneous magnetic material. The multiplicity of SPP waves can only be attributed to the periodic nonhomogeneity of the magnetic material.

Multiple trains of same-color surface-plasmon-polaritons guided by the planar interface of a metal and a sculptured nematic thin film. Part VI: Spin and orbital angular momentums

The spin and the orbital parts of the angular momentum of multiple surface-plasmon-polariton (SPP) waves guided by the planar interface of a metal and a periodically nonhomogeneous sculptured nematic thin film (SNTF) were theoretically investigated. Both the Minkowski and Abraham formulations of angular momentum were considered. Multiple SPP waves guided by the metal/SNTF interface propagating along a direction that does not lie wholly in the morphologically significant plane of the SNTF were found to have different magnitudes and directions of the spin and the orbital parts of the angular momentum. The spin angular momentum is oriented in a variety of directions, but the orbital angular momentum is perpendicular to the direction of propagation and lies in the interface plane. Not only does the periodic nonhomogeneity of the partnering dielectric material engender a multiplicity of SPP waves, but also it can enhance the magnitudes of the spin and orbital parts of their angular momentums.

Enhancement of light absorption efficiency of amorphous-silicon thin-film tandem solar cell due to multiple surface-plasmon-polariton waves in the near-infrared spectral regime*

The reflectances of a thin-film solar cell were computed, using the rigorous coupled-wave approach, as functions of the angle of incidence and the free-space wavelength for illumination by linearly polarized plane waves. A tandem solar cell made of amorphous-silicon alloys was considered. The metallic back-reflector was taken to be periodically corrugated. Both the simple and the compound periodic corrugations of the metallic back-reflector (surface-relief gratings) were investigated. Low-reflectance bands in the reflectance spectrums were correlated with the solutions of the underlying canonical boundary-value problem to delineate the excitation of multiple surface-plasmon-polariton (SPP) waves. For the standard AM1.5 solar irradiance spectrum, we found that the light absorption efficiency in the near-infrared spectral regime can be increased up to 100% when multiple SPP waves of both linear polarization states are excited.

Broadband Light Absorption with Multiple Surface Plasmon Polariton Waves Excited at the Interface of a Metallic Grating and Photonic Crystal

Light incident upon a periodically corrugated metal/dielectric interface can generate surface plasmon polariton (SPP) waves. This effect is used in many sensing applications. Similar metallodielectric nanostructures are used for light trapping in solar cells, but the gains are modest because SPP waves can be excited only at specific angles and with one linear polarization state of incident light. Here we report the optical absorptance of a metallic grating coupled to silicon oxide/oxynitride layers with a periodically varying refractive index, i.e., a 1D photonic crystal. These structures show a dramatic enhancement relative to those employing a homogeneous dielectric material. Multiple SPP waves can be activated, and both s- and p-polarized incident light can be efficiently trapped. Many SPP modes are weakly bound and display field enhancements that extend throughout the dielectric layers. These modes have significantly longer propagation lengths than the single SPP modes excited at the interface of a metallic grating and a uniform dielectric. These results suggest that metallic gratings coupled to photonic crystals could have utility for light trapping in photovoltaics, sensing, and other applications.

Excitation of multiple surface-plasmon-polariton waves guided by the periodically corrugated interface of a metal and a periodic multilayered isotropic dielectric material

The excitation of multiple surface-plasmon-polariton (SPP) waves guided by the periodically corrugated interface of a homogeneous metal and a periodic multilayered isotropic dielectric (PMLID) material was studied theoretically. The solution of the underlying canonical boundary-value problem (with a planar interface) indicates that multiple SPP waves of different polarization states, phase speeds, and attenuation rates can be guided by the periodically corrugated interface. Accordingly, the boundary-value problem was formulated using rigorous coupled-wave analysis and solved using a numerically stable algorithm. A linearly polarized plane wave was considered obliquely incident on a PMLID material of finite thickness and backed by a metallic surface-relief grating. The total reflectance, total transmittance, and the absorptance were calculated as functions of the incidence angle for different numbers of unit cells in the PMLID material of fixed period. The excitation of SPP waves was indicated by those peaks in the absorptance curves that were independent of the number of unit cells, and these peaks were also correlated with the solutions of a dispersion equation obtained from the canonical boundary-value problem.

Grating-coupled excitation of multiple surface plasmon-polariton waves

The excitation of multiple surface-plasmon-polariton (SPP) waves of different linear polarization states and phase speeds by a surface-relief grating formed by a metal and a rugate filter, both of finite thickness, was studied theoretically, using rigorous coupled-wave-analysis. The incident plane wave can be either p or s polarized. The excitation of SPP waves is indicated by the presence of those peaks in the plots of absorbance vs. the incidence angle that are independent of the thickness of the rugate filter. The absorbance peaks representing the excitation of s-polarized SPP waves are narrower than those representing p-polarized SPP waves. Two incident plane waves propagating in different directions may excite the same SPP wave. A line source could excite several SPP waves simultaneously.

On multiple surface-plasmon-polariton waves guided by the interface of a metal film and a rugate filter in the Kretschmann configuration

The excitation of multiple surface-plasmon-polariton (SPP) waves—of different linear polarization states, phase speeds and spatial profiles—guided by the interface of a metal film and a rugate filter in the Kretschmann configuration was investigated. A plane wave of either of the two linear polarization states was made incident on the metal-capped rugate filter of finite thickness and the absorptances were calculated using a stable algorithm. The excitation of SPP waves was inferred by the presence of those peaks in the absorptance curves that were independent of the thickness of the rugate filter. The absorptance peaks representing the excitation of s-polarized SPP waves are narrower than those representing p-polarized SPP waves. For efficient excitation of multiple SPP waves, the metal film's thickness should be close to the penetration depth of the metal. The solution of a canonical boundary-value problem of SPP-wave propagation guided by a metal film, with a semi-infinite homogeneous dielectric material on one side and a semi-infinite rugate filter on the other side, reinforced the results obtained for the Kretschmann configuration. The thin metal film in the Kretschmann configuration may lead to coupling of its two interfaces.

Multiple trains of same-color surface plasmon-polaritons guided by the planar interface of a metal and a sculptured nematic thin film. Part IV: Canonical problem

The canonical problem of the propagation of surface-plasmon-polariton (SPP) waves localized to the planar interface of a metal and a sculptured nematic thin film (SNTF) that is periodically nonhomogeneous along the direction normal to the interface was formulated. Solution of the dispersion equation obtained thereby confirmed the possibility of exciting multiple SPP waves of the same frequency or color. However, these SPP waves differ in phase speed, field structure, and the e-folding distance along the direction of propagation.