Emission Of Surface Plasmon Polaritons Research Articles

Refractive index sensing based on surface plasmon-coupled emission excited by reverse Kretschmann or Tamm structure.

Surface plasmon coupled emission (SPCE) is the directional emission of surface plasmon polaritons (SPPs) through the reverse channels of focused surface plasmon excitation to the far field, which has shown significant possibilities in bioanalysis, medical diagnosis, and so on. We carried out a theoretical study of SPCE to analyze its mechanisms and proposed a new structure to improve the emission intensity of SPCE. We proposed a method for refractive index sensing based on SPCE, consisting of a reverse Kretschmann (RK) or a Tamm structure for the first time, to the best of our knowledge. The corresponding sensing sensitivity reaches 87.61 deg/RIU and 67.44 deg/RIU, respectively. Compared with that in the RK, the far-field radiation intensity of SPCE in the Tamm structure is enhanced by two orders of magnitude. Furthermore, compared with surface plasmon resonance (SPR) sensing, SPCE sensing can improve the signal-to-noise ratio (SNR) and excitation efficiency. Our structures enable refractive index sensing with a high SNR, high spatial resolution, and without the requirement of angular alignment using complex mechanics, which are suitable for practical applications such as quantitative biomolecular detection and medical diagnosis.

Enhanced optical chirality with directional emission of Surface Plasmon Polaritons for chiral sensing applications

Chirality is a crucial aspect in life sciences, where systems capable of enhancing the chiroptical properties of molecules are highly demanded. In this work, we present a numerical proof of concept of a novel approach towards chiral sensing, consisting in the measurement of chiroptical properties via the directional emission of Surface Plasmon Polaritons (SPPs) on a metasurface. Based on the enhanced differential absorption between right and left circularly polarized light upon interaction with a metasurface made of high refractive index dielectric unit cells, a polarization-dependent SPP differential emission is obtained. Furthermore, the plasmonic emission direction is entirely dependent on the polarization handedness. Using FDTD numerical methods we report Circular Dichroism signals of around − 6° for the unit cell, with threefold dissymmetry factor enhancements in places accessible to analytes. We believe that this work sets a brand-new branch in chiral sensing towards faster, real-time measurements.

Surface Plasmon Polaritons Emission with Nanopatch Antennas: Enhancement by Means of Mode Hybridization

We theoretically study the emission of surface plasmon polaritons (SPPs) in cylindrical nanopatch antennas with sub-10 nm dielectric gaps. The eigenmodes of a nanopatch antenna can be classified as...

Dynamics of Strongly Coupled Modes between Surface Plasmon Polaritons and Photoactive Molecules: The Effect of the Stokes Shift

We have investigated the dynamics of strongly coupled modes of surface plasmon polaritons (SPPs) and fluorescent molecules by analyzing their scattered emission polarization. While the scattered emission of SPPs is purely transverse magnetic (TM) polarized, the strong coupling with molecules induces transverse electric (TE) polarized emission via the partial molecular nature of the formed SPP–molecule polariton mode. We observe that the TM/TE ratio of the polariton emission follows the contribution of the molecular excited states in this hybrid mode. By using several types of molecules, we observe that, in addition to the coupling strength, which determines the contribution of the molecular excited states, also the Stokes shift of the molecule fluorescence influences the polarization of the emission: the larger the shift, the lower the TE-polarized emission. We argue that due to random orientation of the molecules, the emission of a fully coherent SPP–molecule polariton should be purely TM-polarized, like...

Scattering of electrically excited surface plasmon polaritons by gold nanoparticles studied by optical interferometry with a scanning tunneling microscope

We study the scattering of electrically excited surface plasmon polaritons (SPP) from individual nanostructures. The tunneling electrons from a scanning tunneling microscope (STM) are used to excite an out-going, circular SPP wave on a thin (50-nm) gold film on which isolated gold nanoparticles (NPs) have been deposited. Interaction of the excited SPPs with the NPs leads to both in-plane (SPP-to-SPP) and out-of-plane (SPP-to-photon) scattering. We use SPP leakage radiation microscopy to monitor the interference between the incident and in-plane scattered SPP waves in the image plane. By changing the location of the STM tip, the distance of the pointlike SPP source to the scatterers can be varied at will, which constitutes a key advantage over other existing techniques. As well, the out-of-plane scattered radiation interferes with the direct light emission from the STM tip in the back focal plane (Fourier plane). This confirms the mutual coherence of the light and SPP emission resulting from the inelastic tunneling of an electron in the STM junction. We use this effect to demonstrate that SPP-to-photon scattering at NPs is highly directional.

Stimulated emission of surface plasmon polaritons on smooth and corrugated silver surfaces

We have observed two regimes of stimulated emission of surface plasmon polaritons (SPPs) propagating at interfaces between dye-doped polymeric films and silver substrates. (i) On top of smooth silver substrates, the lasing threshold is very soft, and the relatively broad stimulated emission peak gradually narrows with increase of the pumping. We infer that this stimulated emission regime is dominated by amplification of SPPs in open paths, with a possible contribution from a diffusion feedback provided by unintentional scattering. (ii) At the same time, the laser action on top of roughened silver substrates is characterized by a sharp threshold and multiple narrow spectral lines. This novel stimulated emission effect has strong coherent feedback supported by strong scattering of SPPs at a roughened silver surface. The observed phenomena provide an addition to the family of surface plasmon lasers, enabling active metamaterials and plasmonics.

Handedness-sensitive emission of surface plasmon polaritons by elliptical nanohole ensembles

We report handedness-sensitive surface plasmon polariton (SPP) emission in mirror-symmetric ensembles of elliptical nanoholes made in a thin gold film. It is found by means of rigorous calculations and scanning near-field optical microscopy that SPP excitation direction depends on the direction of circularly polarized illumination E-vector rotation. An analytical model based on anisotropic polarizability of each nanohole is presented. Both the experimental and calculated results are in agreement with Curie's principle, and contribute to better understanding of symmetry in plasmonics.

Amplified Spontaneous Emission of Surface Plasmon Polaritons with Unusual Angle‐Dependent Response

Loss issues are fundamentally crucial for the application of surface plasmon polaritons (SPPs). In this study the amplified spontaneous emission (ASE) of SPPs in a typical Kretschmann configuration is observed and shows an unusually broadened angular response with increased pump intensity. Theoretical models are further developed to verify the results and understand the amplification of SPPs in Fourier space.

Surface Plasmon Polariton Emission Prompted by Organic Nanofibers on Thin Gold Films

The excitation of surface plasmon polaritons (SPP) at a gold–vacuum interface by femtosecond light pulses mediated by organic nanofiber-induced dielectric perturbations is observed using interferometric time-resolved photoemission electron microscopy. The experimental data are quantitatively reproduced by analytic simulations, where the nanofibers are considered as superior source of the SPP emission. The flexibility and tuneability of phenylene-based nanofibers in their morphology and intrinsic optical properties open up future applications to fabricate custom-designed nanoscale sources of SPP.

Direct observation of amplified spontaneous emission of surface plasmon polaritons at metal/dielectric interfaces

We report on direct observation of amplified spontaneous emission (ASE) of surface plasmon polaritons (SPPs) at the interface of a silver film and a gain medium. Based on a typical Kretschmann configuration incorporated with Rhodamine 6G molecules, the growing ASE spectra of SPPs have been clearly identified by carefully conducting a pump-dependent angle-resolved spectral measurement. Spectral narrowing effects induced by the SPP amplification are also demonstrated. The observed phenomena are helpful in understanding the fundamental interactions between SPPs and gain medium, which could enable wide applications on plasmonic sources and sensors.

Stimulated Emission of Surface Plasmon Polaritons in a Microcylinder Cavity

We have observed stimulated emission of surface plasmon polaritons (SPPs) in dye-doped polymeric microcylinder cavities deposited onto gold and silver wires. The stimulated emission spectra featured a characteristic series of laser modes, with modal spacing corresponding to SPPs propagating at the interface between the metal and dielectric. A plasmonic microlaser adds to the toolbox of plasmonic devices and plasmonic metamaterials and enables on-chip plasmonic generation and loss compensation.

All-Plasmonic Modulation via Stimulated Emission of Copropagating Surface Plasmon Polaritons on a Substrate with Gain

We experimentally demonstrate suppressed absorption and stimulated emission of surface plasmon polaritons (SPP) leading to all-plasmonic modulation of an SPP signal propagating at the interface between a metal and a gain medium; these observations are supported by the developed theory. The use of copropagating signal and control waves can provide more than 10 times more efficient SPP stimulated emission compared to out-of-plane pumping and opens up the possibility to realize integratable plasmonic components for active nanophotonic circuitry.

Stimulated emission of surface plasmon polaritons by lead-sulphide quantum dots at near infra-red wavelengths

Amplification of surface plasmon polaritons in planar metal-dielectric structure through stimulated emission is investigated using leakage-radiation microscopy configuration. The gain medium is a thin polymethylmethacrylate layer doped with lead-sulphide nanocrystals emitting at near-infrared wavelengths. We demonstrate an optical gain of ~200 cm(-1) for the mode under consideration, which corresponds to ~32% compensation of SPP loss.

Optical gain, spontaneous and stimulated emission of surface plasmon polaritons in confined plasmonic waveguide

We develop a theoretical model to compute the local density of states in a confined plasmonic waveguide. Based on this model, we derive a simple formula with a clear physical interpretation for the lifetime modification of emitters embedded in the waveguide. The gain distribution within the active medium is then computed following the formalism developed in a recent work [Phys. Rev. B 78, 161401 (2008)], by taking rigorously into account the pump irradiance and emitters lifetime modifications in the system. We finally apply this formalism to describe gain-assisted propagation in a dielectric-loaded surface plasmon polariton waveguide.

Amplified spontaneous emission of surface plasmon polaritons and limitations on the increase of their propagation length

Amplified spontaneous emission of surface plasmon polaritons (SPPs) at the interface of a resonant gain medium has been observed. The amplification is accompanied by significant spectral narrowing and limits the gain available for compensation of SPP propagation losses. The effect is similar to the deteriorating influence of amplified spontaneous emission in laser resonators.

Compensation of surface plasmon loss by gain in dielectric medium

It has been experimentally shown that absorption loss in metal, which causes damping of localized surface plasmons (SPs) and propagating surface plasmon polaritons (SPPs), can be compensated by optical gain in dye-doped dielectric media adjacent to a metallic surface. In particular, (i) six-fold increase of Rayleigh scattering caused by an enhancement of SP resonance in aggregated metallic nanoparticles, (ii) significant elongation of the propagation length of SPPs by gain, and (iii) stimulated emission of SPPs has been demonstrated. The obtained results pave the road to many applications of nanoplasmonics and metamaterials.

Stimulated Emission of Surface Plasmon Polaritons

We have observed laserlike emission of surface plasmon polaritons (SPPs) decoupled to the glass prism in an attenuated total reflection setup. SPPs were excited by optically pumped molecules in a polymeric film deposited on the top of a silver film. Stimulated emission was characterized by a distinct threshold in the input-output dependence and narrowing of the emission spectrum. The observed stimulated emission and corresponding compensation of the metallic absorption loss by gain enables many applications of metamaterials and nanoplasmonic devices.

Glassy gain

Stimulated emission of surface plasmon polaritons is achieved by using structures with gold strips embedded inside erbium-doped phosphate glass

Observation of Stimulated Emission of Surface Plasmon Polaritons

We report a direct experimental evidence of stimulated emission of surface plasmon polaritons (SPPs) at telecom wavelengths (1532 nm) with erbium doped glass as a gain medium. We observe an increase in the propagation length of signal surface plasmons when erbium ions are excited optically using pump SPP. The design, fabrication, and characterization of SPP waveguides, thin gold metal strips, embedded in erbium (Er) doped phosphate glass is presented. Such systems can be suitable as integrated devices coupling electronic and photonic data transmissions as well as SPP amplifiers and SPP lasers.

Subwavelength Focusing and Guiding of Surface Plasmons

The constructive interference of surface plasmon polaritons (SPP) launched by nanometric holes allows us to focus SPP into a spot of high near-field intensity having subwavelength width. Near-field scanning optical microscopy is used to map the local SPP intensity. The resulting SPP patterns and their polarization dependence are accurately described in model calculations based on a dipolar model for the SPP emission at each hole. Furthermore, we show that the high SPP intensity in the focal spot can be launched and propagated on a Ag strip guide with a 250 x 50 nm2 cross section, thus overcoming the diffraction limit of conventional optics. The combination of focusing arrays and nano-waveguides may serve as a basic element in planar nano-photonic circuits.