Excitation Of Plasmonic Waves Research Articles

Excitation of plasmonic waves in metal–dielectric structures by a laser beam using holography principles

A method for development of gratings for effective excitation of surface plasmonic waves using holography principles has been proposed and theoretically analyzed. For the case of a plasmonic wave in a dielectric layer on metal, the proposed volume hologram is 1.7 times more effective than the simple grating of slits in the dielectric layer with the optimized period and slits’ width. The advantage of the hologram over the optimized grating is in the refractive index distribution that accounts phase relationships between an exciting and an excited waves more correctly. The proposed holographic method is universal. As expected, this can be extended for effective excitation of different types of optical surface waves and modes of optical waveguides.

Excitation of Surface Plasmon Polaritons in an Inhomogeneous Graphene-Covered Grating

Highly confined waves of surface plasmon polaritons (SPPs) in monolayer graphene are efficiently excited using an etched diffractive grating on silicon. In this paper, an inhomogeneous graphene-covered grating is proposed and the excitation of which is analyzed as an analogy with the two-level system in quantum mechanics. Based on the equivalent circuit theory, the excitation of plasmonic waves in an etched diffractive grating is equivalent to the resonance of an oscillator. Thus, according to the governing equation, the electric currents for the inhomogeneous graphene-covered grating is correspond to the ket of energy states in the two-level system. In addition, the excitation of SPPs in an inhomogeneous graphene-covered grating is numerically analyzed to validate the theoretical model. Our work offers a new inroad of the excitation of SPPs in an inhomogeneous graphene-covered grating in an analogy with the two-level system.

Electromagnetically-induced-transparency plasmonics: Quantum-interference-assisted tunable surface-plasmon-polariton resonance and excitation

An experimentally feasible configuration of a prism coupler with an electromagnetically-induced-transparency (EIT) medium layer, e.g., a semiconductor-quantum-dot (SQD) medium, deposited upon its prism base is suggested for generating tunable surface-plasmon-polariton resonance. Such surface-plasmon-polariton resonance and optical excitation of a surface plasmon wave can be manipulated by switchable quantum interference among SQD multilevel transitions driven by two external control fields. When an incident probe field is coupled into a surface plasmon wave excitation mode, the surface-plasmon-polariton (SPP) resonance at the interface between the SQD medium layer and the substrate will arise, and the quantum-coherently controllable reflection spectrum of the probe field on the prism base can be achieved. In this process, destructive and constructive quantum interference (determined by the intensity ratio of the two external control fields) in the SQD multilevel system plays a key role for achieving the tunable reflection spectrum. The EIT-based surface-plasmon-polariton resonance presented here will have three characteristics (some of them would be attractive): (i) switchable quantum interference exhibited by surface plasmon wave excitation, (ii) quantum-coherently controllable surface plasmon polaritons by external optical fields, (iii) surface wave sensitive to dispersion of the SQD quantum coherent medium. Such an effect of controllable optical response based on the quantum-interference switchable surface-plasmon-polariton resonance in the EIT-prism coupler may find some potential applications in design of new photonic and quantum optical devices.

Transmitive Spectral SPR Droplet Biosensing: Principle, Sensor Design, and Experimental Demonstration

Surface plasmons resonance (SPR) architectures based on grating coupler/disperser combination is an attractive alternative for spectral-based biochemical sensing. In this paper, we investigate theoretically and experimentally a new concept where the plasmon coupling occurs through a thin film grating and sensing occurs via the first evanescent diffraction order in transmitive mode. The surface plasmon wave excitation induces a peak in the wavelength as well as in the angular spectra of the detected first transmitted diffraction order. Accordingly, a change in SPR spectrum of the detected diffraction order can be used to quantify the amount of the target molecules immobilized on the sensor surface, and therefore, the concentration of these molecules in the analyte solution. The developed sensor architecture is dedicated to droplet biochemical sensing and appears to be especially suitable for biosensor integration and miniaturization. The presented sensor concept is perfectly suited for mass production of low-cost and reproducible SPR sensor chip for biochemical analysis. The implemented setup gives access to multichannel biosensing with the potential for efficient internal referencing essential to achieve sufficiently high reproducibility and accuracy of the measurements.

Excitation of Plasmonic Waves in Graphene by Guided-Mode Resonances

We propose an active plasmonic device based on graphene. Highly confined plasmonic waves in monolayer graphene are efficiently excited using an etched diffractive grating on silicon. The guided-wave resonance of the combined structure creates a sharp notch on the normal-incidence transmission spectra, as the incident optical wave couples to the graphene plasmonic wave. This structure can be used as a highly tunable optical filter or a broad-band modulator because the resonant wavelength can be quickly tuned over a wide wavelength range by a small change in the Fermi energy level of the graphene. In this paper, we analyze the performance of this device with finite-difference time-domain simulations. We compare the proposed structure with recently demonstrated graphene nanoribbons based on bound plasmonic oscillations.

Demagnifing super resolution imaging based on surface plasmon structures

An imaging mechanism for demagnifing features above wavelength into desired images beyond the diffraction limit is proposed in this letter. The super resolution ability (about two times and even more that of diffraction limit) arises from the surface plasmon wave excitation and amplification associated with metallic grating structure. Two specifically designed masks are projected to the grating surface from both sides, at one of which the superimposed field forms the desired images. Conceptually formalism of the imaging process is presented using spatial Fourier analysis and illustrated with numerical simulations.

Experimental investigation of lateral wave contribution to the shift of a reflected beam at surface plasmon resonance

Reflected field intensity distributions are reported for surface plasmon wave excitation in an attenuated total internal reflection configuration for different metal film thickness. The measured lateral shift is compared with theoretical predictions.