P-polarized Waves Research Articles

Wide-angle and Fano-shape contrast between emission and absorption in hybrid polariton-involved planar structure

Nonreciprocal light propagation in planar structure has become a hot topic because of the pattern-free fabrication process and the potentials for exploring heat transfer and energy management. An effective strategy incorporated with natural van der Waals material (α-phase molybdenum trioxide, α-MoO3), ultra-thin polar crystal (silicon carbide, SiC) thin film and a Weyl semimetal interlayer sitting on a metal (silver, Ag) substrate is proposed. The emission and absorption of the suggested device is explored with electromagnetic simulations that utilize the 4×4 transfer matrix method. Angular-resolved emission shows that the Fano-shape of nonreciprocity can be maintained within wide angle range. Tunable Fano resonances with different line shapes are demonstrated by varying the structural parameters. Moreover, the enhanced nonreciprocal radiation effect can be observed for both s- and p-polarized incidence waves. The proposal allows simultaneous control of spectral distribution and polarization of radiation, which will facilitate the active design and application of mid-infrared emitters.

Polarization features in optical spectra of partially oxidized permalloy nanofilms

For light coupling to partially oxidized permalloy nanofilms, unusual polarization features were demonstrated experimentally and theoretically by analyzing angle-resolved spectra of the ellipsometric parameters, reflection and transmission polarization-resolved spectra at oblique incidence. The polarizing angles for light reflected from the nanofilms were revealed as resonant features. These were dips in reflection spectra for the p-polarized waves, whose reflection was totally suppressed, and the phase experienced a «π-jump » at two wavelengths. It was explained by the simultaneous fulfillment of amplitude equivalence and phase resonance conditions for the p-polarized light waves reflected from a subwavelength bilayer, which was a low-loss oxide layer on an absorbing metal layer.

Multi-Bound States in the Continuum and Lineshape Tailoring of the Multi-Layers Dielectric Metasurface

Bound states in the continuum (BICs) with high quality factors (Q-factors) by confining resonances embedded in a continuous spectrum by eliminating radiation loss can boost substantially light-matter interaction for various applications in ultrathin, active, and nonlinear metadevices. Regulating and improving the modulating freedom of the BICs are important in tailoring the spectra lineshape. Here, we suggest a way to manipulate the number of BICs in the spectra by controlling the layers and the shape or arrangement of the rectangular nanoholes in each layer of the metasurface, illuminated by a p-polarized plane wave. It is convenient to achieve symmetry protected multiple at-Γ BICs and multiple off-Γ BICs associated with the decoupling of the radiation waves and improve their regulation depth only by adjusting the layers and one single nanohole arrangement and shape in one lattice in each layer, without introducing extra geometric complexity of the metasurface. Additionally, we demonstrate the multiple BICs are robust and have a good tolerance to fabrication imperfections. Beyond the multiple BICs of both types, we also explore the huge sensitivity around the multi-BICs of the metasurface on the surrounding medium refractive index. Multiple BICs with high Q-factor realized in this multi-layer metasurface promise various practical applications including ultra-high sensitivity sensors and filters.

Surface plasmon resonance based sensor using one-dimensional photonic crystal

A surface plasmon resonance (SPR) based sensor is presented for the optical sensing that employs one-dimensional photonic crystal (1DPC). An interface of a metal and 1DPC is utilized to excite the surface plasmon-polariton (SPP) waves using prism-coupling. The 1DPC is made up of a bilayer structure of two different dielectric materials. The excited SPP waves are utilized to sense a small change in the refractive index of the dielectric material. A very simple and compact design is proposed for the optical sensing of the dielectric material. A p-polarized plane wave is incident from the metal side and the change in the refractive index of the dielectric material is observed by computing the corresponding change in the incidence angle of excitation of the SPP wave. Absorptance peaks are shifting with a small change in the refractive index of the dielectric materials. It is observed that by changing the refractive index of the prism sensitivity changes with an inverse relation. The power density of the proposed sensor is limited to the metal and 1DPC interface which is the manifestation of the excitation of the SPP wave at that interface. Better results of sensitivity are achieved using this simple design of metal and 1DPC.

Enhanced beam shifts mediated by bound states in continuum

The interaction of light beams with resonant structures has led to the development of various optical platforms for sensing, particle manipulation, and strong light–matter interaction. In the current study, we investigate the manifestations of the bound states in continuum (BIC) on the in plane and out of plane shifts (referred to as Goos–Hänchen (GH) and Imbert–Fedorov (IF) shifts, respectively) of a finite beam with specific polarization incident at an arbitrary angle. Based on the angular spectrum decomposition, we develop a generic formalism for understanding the interaction of the finite beam with an arbitrary stratified medium with isotropic and homogeneous components. It is applied to the case of a Gaussian beam with p and circularly polarized light incident on a symmetric structure containing two polar dielectric layers separated by a spacer layer. For p-polarized plane wave incidence one of the coupled Berreman modes of the structure was recently shown to evolve to the bound state with infinite localization and diverging quality factor coexisting with the other mode with large radiation leakage (Remesh et al 2021 Opt. Commun. 498 127223). A small deviation from the ideal BIC resonance still offers resonances with very high quality factors and these are exploited in this study to report giant GH shifts. A notable enhancement in the IF shift for circularly polarized light is also shown. Moreover, the reflected beam is shown to undergo distortion leading to a satellite spot. The origin of such a splitting of the reflected beam is traced to a destructive interference due to the left and right halves of the corresponding spectra.

All-magneto-optical grating bio-sensors based on enhanced transverse magneto-optical Kerr effect

Herein, a novel structure composed of an all-magneto-optical periodic grating, without using noble metals, is presented to enhance the transverse magneto-optical Kerr effect (TMOKE). This is done by calculating the relative changes in the reflection amplitudes for the p-polarized wave using the finite element method (FEM) with COMSOL Multiphysics. Bio-sensing applications of the proposed structure can be possible by detecting alternation in the refractive index of the analyte medium through monitoring of the TMOKE. The simultaneous operation of the magneto-optic layer as a sensing layer is the advantage of our idea, where direct interaction with the analyte happens, leading to the suppression of the wave reflection amplitudes, and finally leading to extreme TMOKE in a magneto-optical (MO) grating (the TMOKE amplitudes are near 0.8 in this work). And since TMOKE shows a Fano-like shape, we calculate sensitivity and figure of merit (FoM) by fitting them together. This results in high sensitivity, and the value of the FoM is remarkable (between 2×103 and 3×103 refractive index unit) at resonance angles for different refractive indices, which makes our proposed structure able to be utilized for bio-sensing applications.

High Transmission in layered composite with graphene and hyperbolic metamaterials

The transmission characteristics are presented for the sandwich composite structure containing hyperbolic metamaterials (HMMs) and graphene. The numerical results show that the high transmittance (larger than 0.9) within a ultra wide incident angle range (0 ∼ 68.1°, 0 ∼ 75.7°) can be obtained by optimizing the chemical potential (μc=0.5,0.6eV) for both s-polarized and p-polarized waves under the certain incident frequency (30THz). Meanwhile, to acquire the transmission enhancement in a wide incident angle range, the thickness of HMMs and the number of graphene layers should also be chosen appropriately. Additionally, the broadband and wide-angle of the transmission enhancement for s-polarized and p-polarized waves can be acquired by adjusting the incident angles and frequencies, which has the potential application for bandpass and high-pass filters.

Variable magnetic field electron spectrometer to measure hot electrons in the range of 50-460 keV.

Resonance absorption (RA) occurs when a p-polarized electromagnetic wave, obliquely incident on an inhomogeneous plasma, tunnels past its turning point and resonantly excites an electron plasma wave (EPW) at the critical density. This phenomenon is important, for instance, in the direct drive approach to inertial fusion energy and is a particular example of a wider phenomenon in plasma physics known as mode conversion, which is crucial for heating magnetic fusion devices, such as tokamaks, via RF heating. Direct measurement of these RA-generated EPW accelerated hot electrons, with energy in the range of a few tens to a few hundreds of keV, is a challenging task due to the relatively low deflecting magnetic fields needed. The solution described here is a magnetic electron spectrometer (MES) with a continually changing magnetic field, lower at the entrance of the MES and gradually increasing toward the end, that enables the measurement of a wide spectral range of electrons with energies between 50 and 460keV. Electron spectra taken in a LaserNetUS RA experiment were acquired from plasmas generated by irradiating polymer targets with the combination of an ∼300ps pulse followed by a series of ten high intensity 50-200fs duration laser pulses from the ALEPH laser at Colorado State University. The high intensity beam is designed as spike trains of uneven duration and delay pulses in order to modify the RA phenomenon.

Investigation of p-polarized wave propagation through nonmagnetic chiral interfaces and slabs without and with dielectric loss

ABSTRACT Wave propagation through a nonmagnetic achiral/chiral (ACC) interface (en route to chiral/achiral (CAC) interfaces and resonant slabs) is investigated in-depth using amplitude Fresnel coefficients (FCs). A p-polarized plane wave at the interface is tracked for rarer-to-denser configuration, followed by incidence at a CAC interface under stand-alone and ACC source interface conditions. Finally, a model involving a low-loss tangent chiral dielectric is examined by investigating the corresponding reflection and transmission behaviour. Detailed understanding of the (anomalous or normal) occurrence of total internal reflection (TIR), inverse total internal reflection (ITIR), evanescence, – and – based envelope decay and propagation across the modes in the longitudinal and transverse directions. A few sample simulations involving chiral slab resonators with p-polarization incidence are also presented. In ongoing follow-up work, dual lossy interfaces combined to create chiral resonators and arrays (in the thick or thin film regimes) will be investigated building upon the results presented here.

NON-REFLECTIVE INCIDENCE OF P-POLARIZED ELECTROMAGNETIC WAVES ON THE SOLID-STATE STRUCTURE "UNIAXIAL PLASMONIC METASURFACE — DIELECTRIC LAYER — METAL"

Subject and Purpose. The solid-state structures involving metasurfaces can be used to effectively control some of the basic properties of electromagnetic waves, like amplitude, phase and polarization. The present work is aimed at analyzing the new effects that may appear during incidence of p-polarized electromagnetic waves upon a solid-state structure involving a uniaxial plasmonic metasurface, a dielec- tric interlayer, and a layer of metal. Methods and Methodology. The conditions suitable for identifying the effects that result from the reflection of a p-polarized electro- magnetic wave incident upon a solid-state structure of the above described type have been sought for via numerical simulation. That has allowed finding the magnitudes of the essential parameters, such as angles of incidence and frequencies of the electromagnetic waves, as well as thicknesses of the dielectric interlayer, that could stipulate appearance of novel electromagnetic effects. Results. It has been shown that the solid-state structure involving a uniaxial plasmonic metasurface, a dielectric interlayer, and a layer of metal is capable, under certain conditions, to fully absorb an incident electromagnetic wave of p-polarization. Moreover, a new effect has been predicted, specifically that of full conversion of the incident p-polarized electromagnetic wave into a reflected wave of s-polariza- tion. The necessary condition is that the plane of incidence of the electromagnetic wave were at an acute angle to the principal symmetry axis of the plasmonic metasurface. Conclusions. The solid-state structures of the type involving a uniaxial plasmonic metasurface, a dielectric interlayer, and a layer of metal are characterized by unique reflective properties. They are capable of fully absorbing, under certain conditions, the p-polarized electromagnetic waves incident upon them. Such structures can be used for creating optical and nanoelectronic devices of new types.

Impact of non-linearity and non-integer dimension on the reflection and transmission coefficients

Presented manuscript is devoted to the study of reflection and transmission coefficients of a second-order nonlinear dielectric and linear dielectric NID interface excited by a P-polarized electromagnetic wave. Impact of the non-linearity of the NL medium and non-integer dimension of the NID medium are studied separately. The method of separation of variables is used to model the propagation of waves in NID medium and the solution of the non-linear wave equation is obtained by following the procedure of slowly varying amplitude approximation. We extend our analysis for special cases of the original geometry, i.e. epsilon negative non-linear, mu negative non-linear and epsilon negative NID mediums are considered in this regard. We also calculated the specific values of the permittivities, permeability and dimension of the NID medium for which maximum amplitude of the reflection and transmission coefficients can be achieved.

One-Dimensional Photonic Crystals with Different Termination Layer Thicknesses and Very Narrow Bloch Surface Wave and Guided Wave Based Resonances for Sensing Applications

We demonstrate an efficient sensing of both gaseous and aqueous analytes utilizing Bloch surface waves (BSWs) and guided waves (GWs) excited on a truncated one-dimensional photonic crystal (1DPhC) composed of six TiO2/SiO2 bilayers with a termination layer of TiO2. For the gaseous analytes, we show that 1DPhC can support the GW excited by an s-polarized wave and the theoretical shift of the resonance wavelength is linear for small changes in the analyte refractive index (RI), giving a constant RI sensitivity of 87 nm per RI unit (RIU). In addition, for the aqueous analytes, the GW excited by s-polarized and BSW by p-polarized waves can be resolved and exploited for sensing applications. We compare two designed and realized 1DPhCs with termination layer thicknesses of 60 nm and 50 nm, respectively, and show experimentally the differences in their very narrow reflectance and phase responses. An RI sensitivity and figure of merit as high as 544.3 nm/RIU and 303 RIU−1, respectively, are obtained for the smaller thickness when both s- and p-polarized BSWs are excited. This is the first demonstration of both very deep BSW-based resonances in two orthogonal polarizations and a very narrow resonance in one of them.

INFLUENCE OF UNIAXIAL PLASMON METASURFACE ON ANTIREFLECTION PROPERTIES OF DIELECTRIC LAYER

Subject and Purpose. Th e study of the eff ect of refl ectionless electromagnetic waves propagation through solid-state structures containing metasurfaces at its boundaries has a great scientifi c and practical interest for improving the performance and creating new types of nanoelectronics and optics devices. Th e aim of this work is to study the eff ect of an anisotropic uniaxial plasmon metasurface located at the boundary of the dielectric layer on the eff ect of refl ectionless propagation of electromagnetic waves. The study of the effect of refl ectionless propagation of electromagnetic waves through solid-state structures containing metasurfaces at its boundaries is of great scientific and practical interest for improving the performance and creating new types of nanoelectronics and optics devices. Methods and Methodology. Numerical simulations were used to study the effect of the refl ectionless electromagnetic waves propagation through an anisotropic uniaxial plasma metasurface lying on the dielectric layer. It is used to determine the thicknesses and permeability values of the dielectric layer, for which the effect was observed. Results. It is shown that the presence of an anisotropic uniaxial plasmon metasurface on the dielectric layer leads to a signifi cant conditions change of the eff ect of refl ectionless propagation of p-polarized electromagnetic waves along and across the main axis of anisotropy of the metasurface. It was shown that the metasurface removes the rigid restriction of the dielectric layer permeability value. To achieve the effect of refl ectionless propagation of electromagnetic waves, the permeability of the dielectric layer can be chosen within a wide range. Conclusion. Dielectric layers with anisotropic uniaxial plasmonic metasurfaces have signifi cantly better characteristics for the effect of refl ectionless propagation of electromagnetic waves. They can be used to create fundamentally new nanoelectronic and optical devices.

CHANGES IN ELECTROMAGNETIC WAVE POLARIZATION RESULTING FROM ITS REFLECTION AT A UNIAXIAL PLASMONIC METASURFACE ON TOP OF A DIELECTRIC LAYER

Subject and Purpose. The analysis of the electromagnetic waves’ polarizational transformations that may accompany their reflection from a metasurface is of considerable scientific and practical interest from the point of possibilities for improving characteristics of nanoelectronic and optical devices, and creating novel types of these. This work has been aimed at finding the conditions for efficient conversion of a p-polarized electromagnetic wave incident upon a uniaxial plasmonic metasurface at the boundary of a dielectric layer, into a wave of s-polarization. Methods and Methodology. The effects of conversion of p-polarized electromagnetic waves incident upon a uniaxial plasmonic metasurface, into s-polarized waves were explored through numerical modeling. The approach has allowed determining the wave frequencies and thicknesses of the dielectric layer best suitable for ensuring full conversion. Results. The presence of a uniaxial plasmonic metasurface on top of a dielectric layer can provide for full conversion of an incident p-polarized electromagnetic wave into a wave of s-polarization. As has been established, the effect takes place if the plane of incidence of the p-polarized wave makes an acute angle with the principal axis of the plasmonic metasurface. Another finding is that the full conversion is possible for a variety of permittivity values of the dielectric layer. Conclusions. The uniaxial plasmonic metasurface placed on a dielectric layer is characterized by unique reflective properties. It can have a noticeable impact on polarization of the p-polarized wave’s incident upon the layer. Dielectric layers provided with uniaxial metasurfaces can be used for creating optical and nanoelectronic devices of new types.

Enhanced terahertz emission from mushroom-shaped InAs nanowire network induced by linear and nonlinear optical effects

The development of powerful terahertz (THz) emitters is the cornerstone for future THz applications, such as communication, medical biology, non-destructive inspection, and scientific research. Here, we report the THz emission properties and mechanisms of mushroom-shaped InAs nanowire (NW) network using linearly polarized laser excitation. By investigating the dependence of THz signal to the incidence pump light properties (e.g. incident angle, direction, fluence, and polarization angle), we conclude that the THz wave emission from the InAs NW network is induced by the combination of linear and nonlinear optical effects. The former is a transient photocurrent accelerated by the photo-Dember field, while the latter is related to the resonant optical rectification effect. Moreover, the p-polarized THz wave emission component is governed by the linear optical effect with a proportion of ∼85% and the nonlinear optical effect of ∼15%. In comparison, the s-polarized THz wave emission component is mainly decided by the nonlinear optical effect. The THz emission is speculated to be enhanced by the localized surface plasmon resonance absorption of the In droplets on top of the NWs. This work verifies the nonlinear optical mechanism in the THz generation of semiconductor NWs and provides an enlightening reference for the structural design of powerful and flexible THz surface and interface emitters in transmission geometry.

Transverse Anderson localization of evanescent waves propagating in randomly layered media

We study theoretically the transverse Anderson localization of light in the simplest geometry, where the p-polarized wave propagates along the layers in the randomly stratified dielectric and evanesces exponentially in the direction across the layers. In this case, there exist two reasons for the localization of the wave in the direction transverse to its propagation: the usual evanescent wave confinement and the Anderson mechanism related to the randomness of the spatial distribution of permittivity. We solve the problem using the retarded-Green-function formalism in the Born approximation and show that, for fixed values of the wave frequency ω and wavenumber q, the random inhomogeneity results in the weakening of the wave localization. In the case of the surface plasmon-polaritons (SPPs) propagation, the Anderson mechanism changes the dispersion law for SPPs, moving the dispersion curves away from the light line. Therefore, the localization depth varies in different ways when increasing the disorder, depending on which of the values, wave vector q or frequency ω, is fixed. Namely, the localization depth increases for given q, but it decreases for given ω.

Optimization for continuous-wave terahertz reflection imaging for biological tissues.

Continuous-wave terahertz reflection imaging is a potential tool for biological tissues. Based on our home-made continuous-wave terahertz reflection imaging system, the effect of both polarization mode and reflection window on the imaging performance is studied theoretically and experimentally, showing good agreement. By taking obtaining sample information and image contrast into consideration, p-polarized terahertz waves are recommended. Moreover, considering the sample boundary identification and the image contrast, selection criteria for reflection window are proposed. This work will help to improve the performance of continuous-wave terahertz reflection imaging and accelerate the THz imaging in biological application.

High performance liquid analyte sensing based on Bloch surface wave resonances in the spectral domain

In this paper, we report a design of a truncated one-dimensional photonic crystal (1DPhC) comprising six bi-layers of TiO2/SiO2 with a termination layer of TiO2 to realize a highly sensitive liquid analyte sensor utilizing Bloch surface wave (BSW) resonances in the spectral domain. We demonstrate that the BSW excitation shows up as a dip for both p- and s-polarized waves. Reflectance response for a p-polarized BSW is due to the spectral interference with maximum depth, and resonance thus obtained is comparable in magnitude with surface plasmon resonance (SPR). In the theoretical analysis, the spectral reflectance, phase difference and its derivative are determined for aqueous solutions of NaCl when the refractive index (RI) is changed in a range of 1.3330–1.3482. We revealed that the BSW resonances for the p-polarized wave give a sensitivity of 1602 nm per RI unit (RIU) and figure of merit (FOM) of 106 RIU−1, respectively. For an s-polarized BSW, they are increased to 1933 nm/RIU and 434 RIU−1, respectively. Moreover, the theoretical results are experimentally verified, and very good agreement is confirmed. The spectral responses for aqueous solutions of NaCl with the RI up to 1.3547 give for the p-polarized BSW a sensitivity of 2022 nm/RIU and FOM of 109 RIU−1, respectively, and using the spectral derivative of the BSW phase difference, the FOM is increased to 301 RIU−1. BSW based sensors with responses in both polarizations thus represent an effective alternative to SPR sensors with advantages including a higher FOM and mechanical robustness.

Properties of band gap for p-polarized wave propagating in a binary superconductor-dielectric photonic crystal

A photonic crystal (PC) having the structure (AB)NA is investigated. A and B are superconductor and dielectric layers, respectively. P-polarized (TM) wave is assumed to be incident on the PC. The transmission of TM waves through the PC is studied with a focus on photonic band gap (PBG). The change in the PBG is studied with the variation of different parameters of the superconducting layer such as temperature, critical temperature, thickness and London penetration length. The angle of incidence dependence of the PBG is also investigated. The PBG band width at half maximum (BWHM) decreases with increasing the incidence angle until Brewster angle is reached where the band gap vanishes. The BWHM has shown the lowest dependence on temperature and critical temperature among the parameters of the superconducting layer. London penetration length has the greatest effect on the BWHM among the parameters of the superconductor layer.

Scattering matrix approach for propagation of electromagnetic waves through gyrotropic superlens

We present a theoretical formalism for the calculation of the field distributions inside different types of gyrotropic multilayered structures, as well as their reflection and transmission properties. We show the applicability of this approach by calculating the relative changes in the reflection amplitudes for both s- and p-polarized waves, impinging upon slabs with different kinds of optical anisotropy. Furthermore, we show how to obtain, the dispersion relations of the surface electromagnetic modes linked to extreme values of transverse magneto-optical Kerr effect.