Amplification Of Surface Plasmon Polaritons Research Articles

Amplification and excitation of surface plasmon polaritons via four-wave mixing process

We suggest a scheme for the excitation and amplification of surface plasmon polaritons (SPPs) along the interface between metal and semiconductor quantum well (SQW), employing a four-wave mixing (FWM) process. The SQW consists of four-level asymmetric double quantum wells that exhibit quantum interference effects, which leads to the coupler-free excitation of SPPs. In our proposed system, the inherent losses of SPPs are compensated by introducing gain through the FWM process, resulting in a significant enhancement in the propagation length and penetration depth of SPPs. We further analyze the effect of gain on the long-range and short-range SPPs and observe that the propagation distance and lifetime of both types of SPPs are increased.

Giant enhancement of third harmonic generation in an array of graphene ribbons using amplification of surface plasmon polaritons by optical gain

In this paper, we theoretically study the enhancement of third-harmonic generation in a plasmonic structure composed of an array of trilayer graphene ribbons sandwiched between two CaF2\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$CaF_{2}$$\\end{document} layers. In fact, we suggest a new method for more enhancement of nonlinearity in plasmonic structures using incorporation of optical gain into graphene ribbons. As the pump intensity increases, the maximum output intensity of third harmonic generated (THG) wave versus fundamental frequency is blue-shifted while its value enhances. Our analysis indicates that the enhancement factor of THG in our proposed structure is 1.1 × 107 without occurring an electric breakdown compared to case at which an optically pumped trilayer graphene sheet sandwiched between two CaF2 layers. Therefore, only presence of optical gain is not sufficient for significant enhancement of output intensity of THG wave and excitation of SPPs through the structure is also essential. On the other hand, our results demonstrate that the output intensity of THG wave from the proposed structure under optical pumping enhances by 105\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$10^{5}$$\\end{document} times compared to the plasmonic structure without optical gain which confirms the role of optical gain for THG enhancement in the plasmonic structure. This is because the gain in graphene ribbons amplifies the SPPs waves leading to the more field enhancement along the graphene ribbons which results in significant enhancement of THG wave in the plasmonic structure in comparison with one without gain. Therefore, we reveal that both SPPs and optical gain contribute to the strong output intensity of THG in our proposed structure compared to the trilayer graphene sheet inserted between two CaF2 layers.

Resonant amplification of slow surface plasmon polaritons in a DC current pumped semiconductor/graphene waveguide with a groove defect

We propose the principle of a planar surface plasmon polariton amplifier composed of a complex waveguide structure based on a semiconductor thin film separated from a dielectric substrate by a graphene monolayer. The amplification of surface plasmon polaritons in that waveguide in the terahertz regime is driven by a direct current in the graphene layer under a synchronism condition that allows an efficient energy exchange from the collective flux of charge carriers in graphene and the surface electromagnetic wave in the semiconductor film. Positive feedback required for resonant amplification is achieved through surface plasmon polariton reflections at the edges of the active waveguide, one of which is formed by a local thickness defect (a groove) at the upper surface of the semiconductor film that also provides an exit channel for the energy of the amplified surface wave to be transferred to an adjacent passive thin film semiconductor waveguide. We determine the conditions required for the resonant amplification of surface plasmon polaritons in that complex structure, which are essentially governed by the geometry of the groove as well as by the characteristic parameters of the active and passive waveguides.

Coherent surface plasmon polariton amplification via free-electron pumping

Surface plasmonics with its unique confinement of light1,2 is expected to be a cornerstone for future compact radiation sources and integrated photonics devices. The energy transfer between light and matter is a defining aspect that underlies recent studies on optical surface-wave-mediated spontaneous emissions3-5. However, coherent stimulated emission of free electrons, which is essential for free-electron light sources, and its dynamical amplification process remain to be disclosed in a clear, unambiguous and calibrated manner. Here we present the coherent amplification of terahertz surface plasmon polaritons via free-electron-stimulated emission: a femtosecond optical pulse creates an in-phase free-electron pulse with an initial terahertz surface wave, and their ensuing interactions intensify the terahertz surface wave coherently. The underlying dynamics of the amplification, including a twofold redshift in the radiation frequency over a one-millimetre interaction length, are resolved as electromagnetic-field-profile evolutions using an optical pump-probe method. By extending the approach to a properly phase-matched electron bunch, our theoretical analysis predicts a super-radiant surface-wave growth, which lays the ground for a stimulated surface-wave light source and may facilitate capable means for matter manipulation, especially in the terahertz band.

Optical amplification of surface plasmon polaritons in a graphene single layer integrated with a random grating

In this paper, we design and simulate a terahertz (THz) controllable active plasmonic waveguide structure based on a single graphene layer that is placed on a random SiC grating substrate whose grooves are filled with CaF2. Optical gain in the proposed THz active plasmonic waveguide structure is provided by the stimulated emission process in the photoexcited graphene monolayer that leads to the amplification of surface plasmon polariton (SPP) waves. We use a random grating substrate to introduce Anderson localization of the SPP waves propagating through the graphene monolayer to enhance their optical amplification at resonance frequencies in which more amplification occurs due to multi-scattering and interference effects. It is shown that the input SPP wave can be amplified by 130 times at resonance frequencies of the random system. Significant amplification occurs only for frequencies that are equal to the resonance frequencies corresponding to the passive structure and are located within the gain bandwidth of graphene. The effects of depth and width of filled grooves on the amplification characteristics are also investigated. Furthermore, we show that increasing the ambient temperature by 30 K can reduce the output intensity by a factor of 12. This property of the proposed graphene-based THz plasmonic waveguide structure makes it useful in temperature sensing applications and on/off switchable laser devices.

Hyperbolic plasmonics with anisotropic gain–loss metasurfaces

In this Letter, a fundamentally new concept of realization of hyperbolic plasmonic metasurfaces by anisotropic gain-loss competition is proposed, and the possibility of highly directional propagation and amplification of surface plasmon polaritons is predicted. A simple realistic configuration of such a metasurface represents the periodic array of lossy metallic slabs embedded in the gain matrix. Our results may pave the way for numerous applications ranging from integrated and highly directional quantum light emitters to nonlinear-optical frequency converters.

Resonant amplification of surface plasmon polaritons with an electric current in a single-walled carbon nanotube lying on a spatially modulated substrate

We discuss the possibility of using a direct electric current pump in order to amplify a mid-infrared surface plasmon polariton (SPP) in a single-walled carbon nanotube (CNT) deposited on a substrate. Amplification is achieved providing that the phase velocity of the SPP and the drift velocity of the charge carriers in the nanotube are matched. Calculating the amplification characteristics involves numerical simulations that allow to account for the influence of the substrate on the dispersion and inhomogeneity of the plasmon mode field distribution across the CNT. The spectral behaviour of an amplified SPP is shown to exhibit a high sensitivity to variations of the refractive index of the substrate supporting the CNT. We propose a design for the resonant amplification of SPPs with a DC current pump, in which a distributed resonator is obtained with a periodical modulation of the refractive index of the substrate.

Surface plasmon hole burning via doppler broadening

The hole burning phenomenon is investigated in a five-level atomic configuration at the interface of cesium and gold in the presence of Doppler broadening. The group index and refractive index of surface plasmon polaritons (SPPs) becomes equal in the hole burning region, which display that the phase and group velocities of SPPs are matched. The propagation length during absorption of SPPs decreases with the decrease of absorption, while there are increases with amplification of SPPs. This study could have significant applications in optical storage devices, telecommunication, imaging, and enhancement of plasmonster memory.

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.

Noise reduction in plasmonic amplifiers

Surface plasmon polaritons amplification give the possibility to overcome strong absorption in metals and design truly nanoscale devices for on-chip photonic circuits. However, the process of stimulated emission in the gain medium is inevitably accompanied by spontaneous emission, which greatly increases the noise power. Herein we present an efficient strategy for noise reduction in plasmonic amplifiers,which is based on gain redistribution along the amplifier. We show that even a very small gain redistribution (∼3%) makes it possible to increase the signal-to-noise ratio by ∼100% and improve the bit error ratio by orders of magnitude.

Surface plasmon polariton amplification in a single-walled carbon nanotube.

The interaction of a surface plasmon polariton wave of the far-infrared regime propagating in a single-walled carbon nanotube with a drift current is theoretically investigated. It is shown that under the synchronism condition a surface plasmon polariton amplification mechanism is implemented due to the transfer of electromagnetic energy from a drift current wave into a terahertz surface wave propagating along the surface of a single-walled carbon nanotube. Numerical calculations show that for a typical carbon nanotube surface plasmon polariton amplification coefficient reaches huge values of the order of 106 сm-1, which makes it possible to create a carbon-nanotube-based spaser.

Surface plasmon polariton amplification in semiconductor–graphene–dielectric structure

A mechanism of amplification of surface plasmon polaritons due to the transfer of electromagnetic energy from a drift current wave into a far‐infrared surface wave propagating along a semiconductor‐dielectric boundary in waveguide geometry is proposed. A necessary condition of the interaction of these waves is phase matching condition, i. e., when the phase velocity of the surface wave approaches the drift velocity of charge carriers. It is shown that in the spectral region of the surface plasmon polariton slowing‐down its amplification coefficient can reach values substantially exceeding the ohmic loss coefficient of the surface wave in the structure. image

Amplification of surface plasmon polariton wave in single-walled carbon nanotube using electric current pump

We propose a surface plasmon polariton amplification technique based on direct energy transfer from a dc electric current flowing in a carbon nanotube. It is shown that when the synchronization conditions are satisfied, when the surface plasmon polariton wave velocity is close to the drift velocity of the charge carriers in the nanotube, the surface wave is significantly enhanced.

Non-degenerate optical parametric amplification analysis of surface plasmon polariton wave in a silver coated PPLN planar waveguide

Propagation length enhancement of surface plasmon polariton (SPP) wave in telecom c-band through nonlinear χ(2)-based nondegenerate difference frequency generation (ndDFG) process is investigated theoretically. The SPP wave is excited in a silver coated planar periodically poled lithium niobate (PPLN) waveguide. Quasi phase matching is used to compensate the phase mismatch between the interacting excited SPP and guided modes. Domain inversion with proper domain wavelength of Λ = 101.9 μm leads to nonlinear efficient mode interaction of guided↔SPP. With 31 MW/cm coupled pump intensity a SPP amplification of about 16 dB is achievable which results in enhancement of the propagation length about 11 mm. The acceptance SPP amplification bandwidth is pump power dependent. In a low pump depletion regime, a 3-dB bandwidth is about 75 nm whereas in more depletion the bandwidth becomes narrower but not less than 25 nm.

Investigations of influences of spontaneous emission properties on surface plasmon polariton amplifications with the rate-equation theory

The influences of the position-related spontaneous emission properties of gain media on gain and amplified spontaneous emission (ASE) noise characteristics of surface plasmon polariton (SPP) amplification are investigated with rate-equation theory in this paper. It is found that both the spontaneous emission rate and the probability of spontaneous emission into the SPP mode of the gain media in an SPP waveguide are position related. Based on this, a rate-equation model considering those spontaneous emission properties is presented. With this model, the influences of the position-related spontaneous emission properties on the gain and ASE noise characteristics of a single-mode dielectric-loaded SPP amplifier are discussed. The results show that the spontaneous emission rate of gain media is enhanced near the metal interface and the probability of spontaneous emission into the SPP mode decreases near both the metal and air interfaces of the amplifier. This gives rise to reduced gain and low ASE output power. Moreover, the noise property of the amplifier may be improved because of the great decrease in the output ASE power.

Quality Factor Improvement for Nano Cavity

In this paper, the increasing of quality factor in the stimulated amplification of surface plasmon polaritons at visible frequencies was reported. Laser science has been successful in producing high powered, faster, and smaller coherent light sources. Such lasers are restricted, both in optical mode size and physical device dimension, to being larger than half the wavelength of the optical field, and it remains a key fundamental challenge to realize ultra-compact lasers that can directly generate coherent optical fields at the nanometer scale, far beyond the diffraction limit. A way of addressing this issue is to make use of surface plasmons, which are capable of tightly localizing light, but so far ohmic losses at optical frequencies have inhibited the realization of truly nanometer-scale lasers based on such approaches. We design a plasmonic laser with quality factor equal 900 at wavelength 500 nm.

Full loss compensation in hybrid plasmonic waveguides under electrical pumping.

Surface plasmon polaritons (SPPs) give an opportunity to break the diffraction limit and design nanoscale optical components, however their practical implementation is hindered by high ohmic losses in a metal. Here, we propose a novel approach for efficient SPP amplification under electrical pumping in a deep-subwavelength metal-insulator-semiconductor waveguiding geometry and numerically demonstrate full compensation for the SPP propagation losses in the infrared at an exceptionally low pump current density of 0.8 kA/cm2. This value is an order of magnitude lower than in the previous studies owing to the thin insulator layer between a metal and a semiconductor, which allows injection of minority carriers and blocks majority carriers reducing the leakage current to nearly zero. The presented results provide insight into lossless SPP guiding and development of future high dense nanophotonic and optoelectronic circuits.

Amplification of surface plasmon polaritons in nonlinear medium with full saturation susceptibility model

In this paper, a numerical analysis to model the amplification of nonlinear surface plasmon polaritons (SPPs) propagating along a metal active dielectric interface is presented. Nonlinearity of the medium with gain is considered through the full saturation susceptibility parameter of a two-level model. Above the linear threshold of the gain and loss balance, the nonlinear performance of the amplified SPPs is verified, which agrees well with the experimental results reported in the literature. An important feature of the proposed method is to predict an abrupt increase in output intensity due to amplified spontaneous emission.

Toward parametric amplification in plasmonic systems: Second harmonic generation enhanced by surface plasmon polaritons

Having in mind parametric amplification of surface plasmon polaritons (SPPs) as the final goal, we took the first step and studied in the Kretschmann geometry a simpler nonlinear optical process - second harmonic generation (SHG) enhanced by SPPs propagating at the interface between gold film and 2-methyl-4-nitroaniline (MNA). The experimentally demonstrated SHG efficiency was nearly 10(6) times larger than the one reported previously in the SPP system with different nonlinear optical material. The experimentally measured nonlinear conversion efficiency is estimated to be sufficient for parametric amplification of surface plasmon polaritons at ultra-short laser pumping.

Rashba plasmon polaritons in semiconductor heterostructures

We propose a concept of surface plasmon-polariton amplification in the structure comprising interface between dielectric, metal, and asymmetric quantum well. Due to the Rashba spin-orbit interaction, minima of dispersion relation for electrons in conduction band are shifted with respect to the maximum of dispersion dependence for holes in Γ-point. When energy and momentum intervals between extrema in dispersion relations of electrons and holes match dispersion relation of plasmons, indirect radiative transition can amplify the plasmons; excitation of leaky modes is forbidden due to the selection rules. Efficiency of the indirect radiative transition is calculated and design of the structure is analysed.