Layer Of Resonance Research Articles

Peculiarities of the spectrum of reflected and transmitted light of circular polarization for a thin layer of an anisotropic wurtzite-type crystal near phonon resonance

Background. Polaritons attract the attention of researchers and engineers with their unique properties and promising applications in the field of micro- and nanoelectronics. Such applications could include devices such as transistors or even polaritons lasers, as have been reported in the scientific literature.
 Aim. The work analyzes the frequency reflection spectra upon excitation of polaritons, and also considers the change in the polarization ellipse upon reflection of circularly polarized light from an anisotropic crystal.
 Methods. Based on the wave equation in an anisotropic medium, a dispersion equation for polaritons is derived. To calculate energy reflection coefficients using the characteristic matrix method.
 Results. An aluminum nitride AlN crystal was chosen as the object of analysis. It is shown that the use of circularly polarized incident radiation makes it possible, using an anisotropic crystal, to change the nature of polarization from circular to almost linear polarization.
 Conclusion. The found dependence of the polarization of reflected light can be used in electronic devices based on polaritons.

Investigation of Acetone Vapour Sensing Properties of a Ternary Composite of Doped Polyaniline, Reduced Graphene Oxide and Chitosan Using Surface Plasmon Resonance Biosensor.

This work reports the use of a ternary composite that integrates p-Toluene sulfonic acid doped polyaniline (PANI), chitosan, and reduced graphene oxide (RGO) as the active sensing layer of a surface plasmon resonance (SPR) sensor. The SPR sensor is intended for application in the non-invasive monitoring and screening of diabetes through the detection of low concentrations of acetone vapour of less than or equal to 5 ppm, which falls within the range of breath acetone concentration in diabetic patients. The ternary composite film was spin-coated on a 50-nm-thick gold layer at 6000 rpm for 30 s. The structure, morphology and chemical composition of the ternary composite samples were characterized by FTIR, UV-VIS, FESEM, EDX, AFM, XPS, and TGA and the response to acetone vapour at different concentrations in the range of 0.5 ppm to 5 ppm was measured at room temperature using SPR technique. The ternary composite-based SPR sensor showed good sensitivity and linearity towards acetone vapour in the range considered. It was determined that the sensor could detect acetone vapour down to 0.88 ppb with a sensitivity of 0.69 degree/ppm with a linearity correlation coefficient of 0.997 in the average SPR angular shift as a function of the acetone vapour concentration in air. The selectivity, repeatability, reversibility, and stability of the sensor were also studied. The acetone response was 87%, 94%, and 99% higher compared to common interfering volatile organic compounds such as propanol, methanol, and ethanol, respectively. The attained lowest detection limit (LOD) of 0.88 ppb confirms the potential for the utilisation of the sensor in the non-invasive monitoring and screening of diabetes.

Control of Au nanoantenna emission enhancement of magnetic dipolar emitters by means of VO2 phase change layers.

Active, ultra-fast external control of the emission properties at the nanoscale is of great interest for chip-scale, tunable and efficient nanophotonics. Here we investigated the emission control of dipolar emitters coupled to a nanostructure made of an Au nanoantenna, and a thin vanadium dioxide (VO2) layer that changes from semiconductor to metallic state. If the emitters are sandwiched between the nanoantenna and the VO2 layer, the enhancement and/or suppression of the nanostructure's magnetic dipole resonance enabled by the phase change behavior of the VO2 layer can provide a high contrast ratio of the emission efficiency. We show that a single nanoantenna can provide high magnetic field in the emission layer when VO2 is metallic, leading to high emission of the magnetic dipoles; this emission is then lowered when VO2 switches back to semiconductor. We finally optimized the contrast ratio by considering different orientation, distribution and nature of the dipoles, as well as the influence of a periodic Au nanoantenna pattern. As an example of a possible application, the design is optimized for the active control of an Er3+ doped SiO2 emission layer. The combination of the emission efficiency increase due to the plasmonic nanoantenna resonances and the ultra-fast contrast control due to the phase-changing medium can have important applications in tunable efficient light sources and their nanoscale integration.

Strong interaction between graphene layer and Fano resonance in terahertz metamaterials

Graphene has emerged as a promising building block in modern optics and optoelectronics due to its novel optical and electrical properties. In the mid-infrared and terahertz (THz) regime, graphene behaves like metals and supports surface plasmon resonances (SPRs). Moreover, the continuously tunable conductivity of graphene enables active SPRs and gives rise to a range of active applications. However, the interaction between graphene and metal-based resonant metamaterials has not been fully understood. In this work, a simulation investigation on the interaction between the graphene layer and THz resonances supported by the two-gap split ring metamaterials is systematically conducted. The simulation results show that the graphene layer can substantially reduce the Fano resonance and even switch it off, while leaving the dipole resonance nearly unaffected, which is well explained with the high conductivity of graphene. With the manipulation of graphene conductivity via altering its Fermi energy or layer number, the amplitude of the Fano resonance can be modulated. The tunable Fano resonance here together with the underlying physical mechanism can be strategically important in designing active metal-graphene hybrid metamaterials. In addition, the ‘sensitivity’ to the graphene layer of the Fano resonance is also highly appreciated in the field of ultrasensitive sensing, where the novel physical mechanism can be employed in sensing other graphene-like two-dimensional materials or biomolecules with the high conductivity.

Role of stochasticity in turbulence and convective intermittent transport at the scrape off layer of Ohmic plasma in QUEST

Statistical features of fluctuations are investigated using the fast camera imaging technique in the scrape of layer (SOL) of electron cyclotron resonance heated Ohmic plasma. Fluctuations in the SOL towards low field side are dominated by coherent convective structures (blobs). Two dimensional structures of the higher order moments (skewness s and kurtosis k) representing the shape of probability density function (PDF) are studied. s and k are seen to be functions of the magnetic field lines. s and k are consistently higher towards the bottom half of the vessel in the SOL showing the blob trajectory along the field lines from the top towards bottom of the vessel. Parabolic relation (k=As2+C) is observed between s and k near the plasma boundary, featuring steep density gradient region and at the far SOL. The coefficient A, obtained experimentally, indicates a shift of prominence from pure drift-wave instabilities towards fully developed turbulence. Numerical coefficients characterizing the Pearson system are derived which demonstrates the progressive deviation of the PDF from Gaussian towards gamma from the density gradient region, towards the far SOL. Based on a simple stochastic differential equation, a direct correspondence between the multiplicative noise amplitude, increased intermittency, and hence change in PDF is discussed.

금속 표면의 전위가 표면 플라즈몬 공명 특성에 미치는 영향에 대한 연구

표면 플라즈몬 공명 (SPR) 센서에서 금속 전극에 전압을 걸었을 경우, 표면에 여기 되는 전기장에 의해 전하가 쌓이게 된다. 이는 금속 표면의 광학적 성질과 표면 플라즈몬 공명 각도의 변화를 야기시킨다. 본 논문에서는 그에 대한 검증을 위해 다양한 산도 조건의 수용액 하에서 금속에 전압을 걸었을 때의SPR 각도 변화를 측정하였고, 누적 전하량과 공명 각도에 대한 의존성을 그렸을 때 수용액의 산도에 관계없이 일치함을 확인 하였다. 이 관계를 설명하는 기존의 공간전하층(SCL) 모델과 비교해보고 실험결과와 어긋나는 부분과도 잘 맞는 수정된 SCL 모델을 제시하였다. 이 결과는 표면 플라즈몬 공명 센서의 응용과 금속박막의 광학적 성질에 대한 연구에 기여할 거라 기대된다. When voltage is applied on the metal layer of a surface plasmon resonance (SPR) sensor, electric field excitation causes charge accumulation on the metal surface. This alters not only the optical properties of the metal but also the SPR angle. In this study we investigate this effectby performing experiments using solutions of various pH values, and we obtain the relation between total surface charge and SPR angle. The curves for the various pH conditions become coincident. We compare our results to those from an earlier space charge layer (SCL) model, and suggest a modified SCL model which explains our result well. This result will be useful in applications of SPR sensors, and in studying the optical properties of thin metal layers.

Study of energy transfer by electron cyclotron resonance in tokamak plasma

A theoretical study of energy transfer by electron cyclotron resonance to tokamak plasma is presented. Then the predictions of linear theory including relativistic effects on the wave absorption are examined. Electron-cyclotron (EC) absorption in tokamak plasma is based on interaction between wave and electron cyclotron movement when the electron passes through a layer of resonance at a fixed frequency which depends on the magnetic field. This technique is the principle of additional heating (ECRH) and the generation of non-inductive current drive (ECCD) in modern fusion devices. The power absorbed depends on the optical depth which in turn depends on coefficient of absorption and the order of the excited harmonic for O-mode or X-mode

The chaotic layer of a nonlinear resonance under low-frequency perturbation

Conditions whereby the chaotic layer of a nonlinear resonance is described in terms of low-frequency separatrix mapping are discussed. In this case, the accurate estimation of the size of the layer requires the arrangement of resonances at its edge to be known. The resonance picture is constructed using the separatrix mapping invariants of the first three orders. The variation of the layer size with the mapping amplitude is traced with the criterion for resonance overlapping. Results obtained by direct calculation and by invariants analysis are compared. Issues that remain to be solved are noted.

Chaotic layer of a nonlinear resonance driven by quasiperiodic perturbation

We present the numerical and analytical evidences are given of the fact that the formation of a chaotic layer of a nonlinear resonance under the action of multifrequency perturbation is qualitatively different from the case of a single-frequency perturbation which is well studied by now. The new effect of appearance in the separatrix mapping of the system of low-frequency secondary harmonics is discussed and the conditions under which just these harmonics play the dominant role in the formation of chaos are found. Theoretical estimates of the secondary harmonic amplitudes are compared with the results of numerical calculations. Invariants of the first two orders of separatrix mapping enabling one to produce an approximate picture of resonance overlapping on the edge of the chaotic layer and to get its size value are introduced.

Fine structure of splitting of the separatrix of a nonlinear resonance

This report is a continuation of an analysis, initiated elsewhere V.V. Vecheslavov and B. V. Chirikov, Zh. Eksp. Teor. Fiz. 114, 1516 (1998) [JETP 86, 823 (1998)], of the effect of splitting of the separatrix of a nonlinear resonance for the model of standard mapping, based on results of direct measurements of the splitting angle α(K), where K is the system parameter. Measurements were made in the previously used wide range 0.1≳α≳10−208 (1⩾K⩾0.0004), but with significantly higher relative (better than 1050) and average (∼10−55) accuracy. This procedure made it possible to substantially refine the effects observed in Ref. 1 and construct qualitatively new empirical dependences providing reliable extrapolation of the data obtained for the angle and the invariant in the intermediate asymptotic limit K≲10−2 beyond the limits of the investigated region. The results obtained by us can be useful for further development of the theory of separatrix splitting and formation of the stochastic layer of a nonlinear resonance.

Formation of a chaotic layer of nonlinear resonance by a two-frequency perturbation

A new effect [V. V. Vecheslavov, Zh. Eksp. Teor. Fiz. 109, 2208 (1996) (JETP 82, 1190 (1996)]—the appearance of low-frequency secondary harmonics in the separatrix mapping of a system—is discussed in detail for the example of a pendulum with a two-frequency perturbation. It is shown that there exist regions of values of the perturbation parameters where these harmonics make the main contribution to the formation of the chaotic layer of the fundamental resonance. The results of analytical and numerical determinations of the amplitudes of the secondary harmonics are compared.

Effect of relativistic nonlinearity on a driven electron plasma wave in a weakly inhomogeneous plasma

The effect of a relativistic nonlinearity on the excitation of an electron plasma wave (epw) in a cold weakly inhomogeneous plasma is analyzed. It is shown that the relativistic electron mass increase in a large epw field results in a frequency detuning of the epw in the vicinity of the critical layer of linear resonance, and the tunneling of the driven epw to the overdense plasma side. Due to this, the saturated amplitude of the driven wave is limited by 2.2β d 1 3 , which is independent of the density scale-length. The field amplitude distributions of the driven wave are calculated for both the cases of linear and parabolic density profiles. The resonance absorption decrease due to the relativistic nonlinearity is also discussed.

Localization of the surface acoustic longitudinal pseudomode of silicon in a buried SiO2 layer.

We have measured the Brillouin spectrum in p-p polarization of a bilayer of Si/${\mathrm{SiO}}_{2}$ produced by low-dose oxygen implantation on the Si (001) surface. The spectra show two strong resonances close to the longitudinal threshold of silicon, which are explained by a full calculation of the Brillouin cross section. In particular the resonance below the threshold is a guided mode of the buried layer (${\mathrm{SiO}}_{2}$), which originates from the localization in the layer of the surface longitudinal resonance of the matrix (Si). The theory takes into account in a supported double layer both the ripple and the elasto-optic scattering mechanisms.

Statistics of poincaré recurrences and the structure of the stochastic layer of a nonlinear resonance

Statistics of poincaré recurrences and the structure of the stochastic layer of a nonlinear resonance

Statistics of Poincaré recurrences and the structure of the stochastic layer of a nonlinear resonance

<dm:abstracts xmlns:dm="http://www.elsevier.com/xml/dm/dtd"><ce:abstract xmlns:ce="http://www.elsevier.com/xml/common/dtd" view="all" class="author" id="aep-abstract-id5"><ce:section-title>Publisher Summary</ce:section-title><ce:abstract-sec view="all" id="aep-abstract-sec-id6"><ce:simple-para id="fsabs019" view="all">It is shown that a resonance is a mimic of the pendulum motion for which there are two dynamical realms separated by its separatrix and two associated stable and unstable fixed points semi-classically, a quantum level (state) can be viewed as a subspace in the dynamical phase space. Therefore, levels can be classified as those lying below and above the separatrix (corresponding to a resonance in the energy scale). For a pendulum, its oscillating frequency is expected to be smaller as the motion is close to the separatrix because of the nonlinear effect. Quantum mechanically, this will be reflected in that the nearest level energy spacing for those levels around the separatrix will reach a minimum. This is the so-called Dixon dip. This concept is integrated by the quantal and classical analogs. We note that the Dixon dip appears not only at the levels sharing a well-defined polyad number as stated in the literature, but also when the resonance is very seriously perturbed by other complicated interactions, like in the systems of Henon–Heiles and quartic potentials for which resonance is hardly well-defined. However, for the molecular systems like H<ce:inf loc="post">2</ce:inf>O and DCN with multiple resonances, the Dixon dip will be destroyed by the overlapping of resonances which, as conjectured by Chirikov, will lead to chaos. This will be further analyzed by an independent Lyapunov exponent analysis as shown in this chapter below. The destruction of the Dixon dip under multiple resonances in the H<ce:inf loc="post">2</ce:inf>O system where the emerging of multiple resonances definitely will complicate the level structure and may cause the dip phenomenon to be less obvious. For the system of DCN, the dips are only apparent for the low and high levels while not for those levels in between. In terms of Chirikov's conjecture, this is because of the overlapping of resonances which will lead to chaos. Independently, this issue is analyzed in terms of the degree of chaoticity by the averaged Lyapunov exponent. These two results show consistent interpretations. This algorithm can be of potential value in the elucidation of the dynamical properties of the highly excited vibrational system, including the transitional state, of which multiple resonances, and therefore chaos, is prevailing.</ce:simple-para></ce:abstract-sec></ce:abstract></dm:abstracts>