Excitation Of Surface Plasmon Polaritons Research Articles

Efficient Experimental Design of a Long-Range Gapped Surface Plasmon Polariton Waveguide for Plasmonic Modulation Applications

We propose straight and tapered insulator–metal–insulator-type surface plasmon polariton (SPP) waveguides with a gap (G-SPPWs). The optical characteristics of the G-SPPWs are experimentally evaluated at a wavelength of 1.55 μm due to optical communication gateway. The parameters of the 20-nm-thick G-SPPWs were chosen based on our previous simulation results. The excited input SPPs propagate, jump over the gaps with low coupling losses, and propagate again, despite a 9-μm-long gap in the G-SPPWs. The coupling losses of the gap were experimentally determined to be less than 0.7 dB with various gap lengths up to 9 μm. The insertion losses of the straight G-SPPW with 8 μ m × 2 μ m (gap length × SPPW width) and the tapered G-SPPW with 8 μ m × 2 μ m (gap length × SPPW width) and a 6 μ m × 3 μ m (taper width × taper length) were determined to be ∼1.03 and ∼0.74 dB, respectively. The tapered structure increases the tunneling efficiency in the gap of the G-SPPW by reducing the insertion loss. In the 2.5-Gbps optical signal transmission experiment, the proposed G-SPPW exhibited excellent eye opening and transferred the carrier wave as well as the data signal. This device has potential as a new plasmonic modulation element offering control of a guided SPP through interaction with an applied force in the gap.

Multipole Radiations from Large Gold Nanospheres Excited by Evanescent Wave

We proposed the use of the evanescent wave generated in a total internal reflection configuration to excite large gold nanospheres and investigated the radiations of the high-order plasmon modes supported in gold nanospheres. It was revealed that the evanescent wave excitation is equivalent to the excitation by using both the incident and reflected light, offering us the opportunity to control the orientation of the electric field used to excite nanoparticles. In addition, it was found that the scattering light intensity is greatly enhanced and the background noise is considerably suppressed, making it possible to detect the radiations from high-order plasmon modes. Moreover, the influence of the mirror images on the scattering induced by a metal substrate is eliminated as compared with the surface plasmon polariton excitation. By exciting a gold nanosphere with s-polarized light and detecting the scattering light with a p-polarized analyzer, we were able to reveal the radiation from the electric quadrupole mode of the gold nanosphere in both the spatial and the frequency domains. Our findings are important for characterizing the radiations from the high-order modes of large nanoparticles and useful for designing nanoscale photonic devices.

Amplitude scaling and lateral shift of leaky radiation from surface plasmon excitation

We investigate spatial field transformation in surface plasmon excitation by a prism coupling configuration. By exciting surface plasmon polaritons (SPPs), the total reflected field is contributed by the direct reflection of the incident wave and the outgoing radiation of the SPP leakage. We show that the SPP leaky radiation field enables both an amplitude scaling and a lateral shift, which play an important role in forming the total reflected field profile. We classify the spatial field transformation by different coupling conditions from weak coupling to critical and strong cases. A method is proposed to evaluate loss rate ratio between the leaky radiation and the material intrinsic absorption, by measuring the reflected beam profile under flat-top beam illumination. This study paves the way for fast computing and optimizing the incident light to control the total reflected field intensity distribution, which is practically significant in the applications of spatial field, such as plasmonic spatial light modulators and computations.

On-Chip Detection of Optical Spin-Orbit Interactions in Plasmonic Nanocircuits.

On-chip manipulating and controlling the temporal and spatial evolution of light are of crucial importance for information processing in future planar integrated nanophotonics. The spin and orbital angular momentum of light, which can be treated independently in classical macroscopic geometrical optics, appear to be coupled on subwavelength scales. We use spin-orbit interactions in a plasmonic achiral nanocoupler to unidirectionally excite surface plasmon polariton modes propagating in seamlessly integrated plasmonic slot waveguides. The spin-dependent flow of light in the proposed nanophotonic circuit allows on-chip electrical detection of the spin state of incident photons by integrating two germanium-based plasmonic-waveguide photodetectors. Consequently, our device serves as a compact (∼6 × 18 μm2) electrical sensor for photonic spin Hall dynamics. The demonstrated configuration opens new avenues for developing highly integrated polarization-controlled optical devices that would exploit the spin-degree of freedom for manipulating and controlling subwavelength optical modes in nanophotonic systems.

Mimicking surface polaritons for unpolarized light with high-permittivity materials

Tailoring near-field optical phenomena often requires excitation of surface plasmon polaritons (SPPs) or surface phonon polaritons (SPhPs), surface waves at the interface between media with electric permittivities of opposite sign. Despite their unprecedented field confinement, surface polaritons are limited by polarization: only transverse magnetic fields enable their excitation, leaving transverse electric fields unexploited. By contrast, guided modes in positive permittivity materials occur for both linear polarizations, however, they typically cannot compete with SPPs and SPhPs in terms of confinement. Here we show that omnipolarization guided modes in materials with high-permittivity resonances can reach confinement factors similar to SPPs and SPhPs, while surpassing them in terms of propagation distance. We explore the cases of silicon carbide and transition-metal dichalcogenides near their permittivity resonances, and compare with SPhPs in silicon carbide and SPPs in silver, at infrared and visible frequencies, respectively.

Structure of optical Cherenkov radiation in a three-dimensional compound medium with carbon nanotubes

We study the optical Cherenkov radiation in a compound three-dimensional (3D) system with a charge moving over a periodic system of parallel carbon nanotubes. To consider a case of bounded single-walled nanotubes, we apply the numerical finite-difference time-domain technique. We found that, because of the broadband radiation of a charge, the spectrum of the optical field in such a nanosystem is determined by the surface plasmon-polariton excitations. Our study of the field energy spectrum as a function of the plasma frequency detects a nonmonotonic double-well dependency within the area of a surface plasmon-polariton resonance. A well-defined peak that indicates a generation of collective excitations in nanotubes by Cherenkov field is registered.

Плазмон-стимулированное фотолегирование в тонкослойной структуре As-=SUB=-2-=/SUB=-S-=SUB=-3-=/SUB=---Ag

Abstract The effect of the excitation of surface plasmon polaritons at the silver – chalcogenide glass interface on photostimulated diffusion of silver into the chalcogenide was studied for the first time. To excite plasmons, a high-frequency aluminum diffraction grating with a period of 248.5 nm was used, onto which a two-layer Ag–As2S3 structure was deposited. It was found that the process of photostimulated diffusion of silver into the chalcogenide layer is accelerated (that is, the photosensitivity of such a structure increases) when the surface plasmon polariton is excited at the Ag – As2S3 interface during the exposure. The dynamics of photostimulated changes in the optical characteristics of the structure, including the initial stage of the photodiffusion process, was registered by recording the changes in the plasmon excitation characteristics with the exposure time.

Role of optical angular momentum in enhanced transmission process of plasmonic coaxial nanoring aperture

The nano groove can highly improve the transmittance of coaxial nanoring aperture due to the excitation of surface plasmon polariton (SPP). The total angular momentum carried by incident beam is reserved in the whole process and transferred to the SPP, thus the vortex SPP carrying orbital angular momentum is generated. The enhanced transmittance of nano aperture by vortex SPP has a wide range of applications, but its physical mechanism has been ignored for a long time. Here we study the process of the enhanced transmittance of the coaxial nanoring aperture and provide a model to describe the process of photon transmission. When the incident light irradiates on the coaxial nanoring aperture and nano groove, the vortex SPP induced by the groove propagates to coaxial nanoring aperture. Some of the photons in the SPP are coupled into the coaxial nanoring aperture and some are reflected back. The reflected photons travel back and forth multiple times between the coaxial nanoring aperture and nano groove. The vortex SPP interacts with the incident beam at the round of coaxial nanoring aperture, which determines the intensity at the round of the coaxial nano aperture, and thus affecting the transmittance. We systematically study the influence of optical angular momentum and the radius of the nano groove on the transmittance of coaxial nanoring aperture by using theoretical analysis and numerical simulations. The results show that the optical angular momentum and radius of the nano groove both affect the radial propagation phase of vortex SPP from nano groove to coaxial nanoring aperture, hence affecting the intensity of the electric field at the round of coaxial nanoring aperture and consequently determine the transmittance. The transmittance peaks of incident beams with different optical angular momenta will appear at different radii of the nano grooves, which provides a potential way to modulate the transmittance by adjusting the radius of the nano groove. This study is instructive for designing the enhanced optical transmission nano device based on vortex SPP.

Enhancement of the Surface Plasmon Polaritons Excitation Efficiency

Surface Plasmon Polaritons (SPPs) are propagating excitations that arise from the coupling of light with collective oscillations of electrons on the metal surface. This paper describes a new approach for increasing the SPP excitation efficiency. Using a computational electromagnetics approach, potential techniques for reducing incident power reflectivity were investigated using the Kretschmann configuration. The effects of different parameters such as incident angle, metal thickness, and dielectric permittivity were tested and optimized to improve the efficiency of SPPs by minimizing reflectivity. An 30% increase in efficiency was obtained. In addition, the optical response of a thin metal film on a glass substrate was numerically examined in terms of SPP excitation. The dependency of the response on the incident angle, materials, and dimensions were demonstrated. This paper describes how an improvement in efficiency can improve the effectiveness of bio-sensing applications through the proper choice of layer dimensions and material permittivity of different layers. The relationship between incident angle and reflectivity for different permittivities can be used for bio-sensing applications such as blood glucose biosensors, etc.

Surface plasmon-polaritons in deformed graphene excited by attenuated total internal reflection

AbstractIn the present work we theoretically investigated the excitation of surface plasmon-polaritons (SPPs) in deformed graphene by attenuated total reflection method. We considered the Otto geometry for SPPs excitation in graphene. Efficiency of SPPs excitation strongly depends on the SPPs propagation direction. The frequency and the incident angle of the most effective excitation of SPPs strongly depend on the polarization of the incident light. Our results may open up the new possibilities for strain-induced molding flow of light at nanoscales.

Configuration Resonance and Generation Rate of Surface Plasmon Polaritons Excited by Semiconductor Quantum Dots near a Metal Surface

We discuss particular features of generation of surface plasmon polaritons in a metal–dielectric planar interface that is coupled to semiconductor quantum dots by near-field interactions. As a model of working medium for performing numerical experiment, we use a gold metal surface onto which a polyethylene terephthalate film containing CdSe semiconductor spherical quantum dot is deposited. The problem of optimizing the radius of a quantum dot and its distance to a metal surface is solved for achieving the maximum transfer efficiency of the quantum dot energy for the generation of surface plasmon polaritons. Dispersion effects of the surface wave generation rate associated with deviations of the radius of quantum dots and their distance to the metal surface from the corresponding average values are taken into account.

Ultrasensitive Tunable Terahertz Sensor With Graphene Plasmonic Grating

We propose an ultrasensitive tunable terahertz (THz) sensor which consists of single-layer graphene-based gratings integrated with a Fabry–Perot cavity through numerical simulation. The excitation of standing-wave graphene surface plasmon polaritons can make the probing field strongly confined in a gap cavity. This provides an excellent platform for ultrasensitive and high figure-of-merit (FOM) refractive index sensing at the THz band. Our full-wave electromagnetic simulations show a frequency sensitivity as high as 4.2 THz per refractive index unit and an FOM beyond 12.5 at normal incidence in the THz regime. At oblique incidence, the operation angle for effective THz sensing can be maintained as wide as 75° without inducing degeneration of the sensitivity and FOM. The sensing performance can be readily tuned by electrically controlling the chemical potential of graphene. The proposed graphene plasmonic grating scheme is a promising candidate for the development of on-chip integrated THz biochemical sensors.

Enhancement of surface plasmon polariton excitation via feedback-based wavefront shaping.

Surface plasmon polariton (SPP) is an electromagnetic excitation with efficient spatial confinement and high local field intensity at a metal/dielectric interface, which has been widely applied in many fields such as nanophotonics, imaging, biosensing, nonlinear optics, and so on. However, the destructive interference, which arises from wavevector mismatching between the spatial components of incident light and SPP, limits the effective excitation of SPP.Here, we experimentally demonstrate the enhancement of SPP excitation via a feedback-based wavefront shaping method in the Kreschmann configuration. After optimizing the phase profile of the incident laser beam, the intensity is enhanced by a factor of 1.58 times even at the resonance angle of the fundamental mode Gaussian beam. Besides, the influences of different conditions for the enhancement of SPP excitation are also analyzed. This work provides a flexible and convenient method to further enhance the SPP excitation, and it may have the application of further enhancement of the interaction between SPP and other physical processes.

Maskless formation of uniform subwavelength periodic surface structures by double temporally-delayed femtosecond laser beams

Surface structures with nanoscale size and periodicity are important in controlling the flow of light as well as light-matter interaction. Fabrication of these periodic nanostructure requires sophisticated and expensive nanofabrication methods that limits large scale production of such structures. Laser induced periodic surface structures (LIPSS) is a scalable and cheap method to create periodic structures. However, they suffer from lacking a long-range order. Here, we present a maskless fabrication technique of creating highly uniform subwavelength structures on nickel surface, using two collinear femtosecond laser beams at various temporal delays. Our femtosecond laser induced periodic surface structures (FLIPSSs) show a high spatial uniformity with a grating period ranging between 320–350 nm. The high spatial uniformity is a consequence of using two pulsed beams with short inter-beam delay time due to reduction in the propagation length of excited surface plasmon polaritons (SPPs). The subwavelength period is due to grating splitting mechanism where the two beams sequentially interact with existing structures to create a superimposed grating. The demonstrated fabrication method enables large scale fabrication of regular sub-wavelength structures.

Surface-Plasmon Assisted Transmission Through an Ultrasmall Nanohole of ~ 10 nm with a Bull’s Eye Groove

We simulate the light transmission through an extremely small nanoscale aperture having a 10 nm diameter punctured in a metal film positioned at the center of a plasmonic bull’s eye grating. A considerable directive emission of transmitted light with a divergence angle of 5.7 degrees was observed at 10 μm from the nanohole opening at the frequency of surface plasmon polariton excitation, an confirmed by measuring the distance dependent transmission amplitude. Observations of the electric field in cross-sectional, near-field, and far-field views near-field enhancement associated with the surface plasmon excitation, and the interference of the electric field light through the nanohole in the near-field region is responsible for such a considerable directive emission.

Tunable plasmonic focus array generated by Dammann grating in tightly focusing system

Surface plasmon polaritons (SPPs) play crucial roles in a wide-range of applications, such as plasmonic imaging, sensors, plasmonic tweezers, etc. However, the excitation of SPPs gives rise to a big challenge to manipulate SPP fields in a dynamical way. Here, we propose a full optics-controlled method to manipulate SPP fields with Dammann grating (DG) in a tightly focusing system, rather than customizing a special structure on the metal film. Owing to the coupling between free-space incident vector beam and SPPs, the phase of SPPs can be controlled directly by that of the incident vector beam, which is modulated by the DG in free space. Thus, by adjusting the parameters of the DG, a plasmonic focus array with tunable number, position and topological charge can be created flexibly on the metal film, while the light intensity distribution of each plasmonic focus is only dependent on the polarized state of the incident vector beam. This work presents an important step for the manipulation of SPP fields with wavefront techniques and may open new avenues to extend holography for dynamical SPP field control.

Coherent surface plasmon amplification through the dissipative instability of 2D direct current

Abstract We propose an original concept for on-chip excitation and amplification of surface plasmon polaritons. Our approach, named nanoresotron, utilizes the collective effect of dissipative instability of a 2D direct current flowing in vicinity of a metal surface. The instability arises through the excitation of self-consistent plasma oscillations and results in the creation of a pair of collective surface electromagnetic modes in addition to conventional plasmon resonances. We derive the dispersion equations for these modes using self-consistent solutions of Maxwell’s and 2D hydrodynamics equations. We find that the phase velocities of these new collective modes are close to the drift velocity of 2D electrons. We demonstrate that the slow mode is amplified while the fast mode exhibits absorption. Estimates indicate that very high gain are attainable, which makes the nanoresotron a promising scheme to electrically excite and regenerate surface plasmon polaritons.

Cost-effective near-perfect absorber at visible frequency based on homogenous meta-surface nickel with two-dimension cylinder array.

To date, near-perfect light absorbers at visible frequency are still severely impeded by the complicated architecture design and time-consuming costly fabrication procedures. In this work, we design and fabricate a new cost-effective near-perfect absorber at visible frequency based on homogenous meta-surface nickel (Ni) with a two-dimension cylinder array. The simulated and measured average absorption at normal incidence are beyond 94% and 92% over the entire visible wavelength band from 400 nm to 700 nm, respectively. Additionally, the absorbance property was well retained, and the absorptivity still remained beyond 70% when the incident angles vary from 0° to 60°. Our theoretically and experimentally results indicate that the broadband wide-angular absorption can be ascribed to the Rayleigh-Wood anomaly combined with slot modes induced by excited surface plasmon polaritons. Moreover, the low-cost double-beam interference lithography followed by soft nano-imprinting and electroforming technology, which are directly compatible with the cost-effective and high volume manufacturing requirements, are employed to fabricate the proposed absorber. The proposed approach is simple and inexpensive and the obtained ultrathin homogenous meta-surface nickel absorber can be rolled or folded on the surface of various optoelectronics, such as solar system and radiation thermal devices.

Plasmon‐Polariton Induced, “from Surface” RAFT Polymerization, as a Way toward Creation of Grafted Polymer Films with Thickness Precisely Controlled by Self‐Limiting Mechanism

AbstractPlasmon‐induced “from surface” reversible addition‐fragmentation chain‐transfer (RAFT) polymerization is reported for the first time. The gold grating surface, supporting the surface plasmon polariton excitation and propagation, is grafted with RAFT agent, immersed in the solution, containing the NIPAm monomer and AIBN and subsequently illuminated at a wavelength corresponding to plasmon absorption. The grafting of the polymer layer, its thickness, and morphology are characterized by several techniques (including the surface‐enhanced Raman spectroscopy (SERS), scanning electron microscopy and energy‐dispersive X‐ray spectroscopy (SEM‐EDX), X‐ray photoelectron spectroscopy (XPS), nanomechanical atomic force microscopy (AFM) mapping, and goniometry). It is shown that the polymerization efficiently starts only under the surface plasmon‐polariton excitation. The time‐dependent SERS and XPS measurements indicate rather self‐limiting nature of plasmon‐induced “from the surface” PNIPAm growth, namely the reaction takes place up to a certain polymer thickness and is stopped despite a significant excess of polymerization initiator and monomer in the reaction solution. The present results provide the basis for designing further experiments on plasmonic catalysis in general and offer a new way of producing ultrathin polymer films with a defined structural dimension.

Extremely sharp transmission peak in optically thin aluminum film with hexagonal nanohole arrays

Extraordinary transmission is the most attractive phenomenon, that has been studied in recent decades, for optically thick metal film with nanohole arrays. On the contrary, in optically thin metal film with nanohole arrays, it has been found that the interaction between excited surface plasmon polariton and non-resonant direct propagation light introduces a strong light absorption and causes a suppressed transmission dip. Here, we explore the optical properties of a free standing optically thin aluminum film with a hexagonal large filling ratio nanohole array and find an extremely sharp extra extraordinary transmission peak within the suppressed transmission dip which is originated from the interaction of the excited surface plasmon polariton and the non-resonant directly scattered light. Simulation results show that the nanohole-array-based biosensor that were proposed have an excellent sensitivity, with a figure of merit of 87, beyond that of nanohole-array-based biosensors reported previously for normal incidence.