Transverse Electric Transverse Magnetic Research Articles

Full characterization of vector eigenstates in symmetrically confined systems with photonic spin-orbit coupling.

The photonic spin-orbit (SO) coupling is a widely investigated effect in optical microcavities leading to various interesting physical phenomena and potential applications. We report the full sets of eigenenergies and eigenstates in a symmetrically confined potential under the effect of SO coupling induced by the transverse-electric transverse-magnetic (TE-TM) splitting, which are derived analytically via the degenerate perturbation theory. We obtained the eigenenergies and the eigenstates from the 1st to the 6th orders of excited manifold, and demonstrate unambiguously that universal rules governing the mode formation exist in such complicated photonic systems, making the modes exhibiting the features of solid and hollow skyrmions as well as spin vortices. We show that these eigenstates can be described by the SO coupled hyperspheres that can be decomposed into a series of higher-order Poincare spheres. Our results significantly extend the area of microcavity spin-optronics to the general theory of eigenvalues in confined systems, and provide an efficient theoretical frame for the information processing using microcavity-based high-dimensional vector states.

Silicon-based subwavelength grating polarization beam splitter with asymmetric directional coupler

In this paper, a novel polarization beam splitter (PBS) is proposed. The silicon-based subwavelength grating (SWG) is successfully applied to the asymmetric directional coupled PBS, and the research shows that its performance has improved in many aspects. By carefully optimizing structural parameters, the transverse electric (TE) polarization is in a reflected state in the SWG, which effectively weakens the coupling strength, while the transverse magnetic (TM) polarization is almost unaffected. Simulation results show that the bandwidths of TE polarization and TM polarization are 200 nm (1450–1650 nm) and 141 nm (1450–1650 nm) in the extinction ratio of >20 dB, respectively, while the insertion loss is <0.5 dB and <1.3 dB, respectively. The PBS is very robust to the process production. With the manufacturing error exceeding 20 nm, the performance is only reduced by 0.6 dB, effectively solving the problem of complex preparation process.

High-Mode Purity 1 μm Cylindrical Vector Beam All-Fiber Laser Based on a Symmetric Two-Mode Coupler

Cylindrical vector beams (CVBs) are the product of polarization modulation of optical fields, and possess both unique focusing characteristics and excellent properties applicable to machining, imaging, communication and other fields. Mode selection couplers comprise a promising new method to realize the long-term stable output of cylindrical vector beam all-fiber lasers. Mode selection couplers have the advantages of a simple structure, high mode conversion efficiency and high mode purity. However, the production process of conventional asymmetric mode selection couplers is more complicated. Therefore, in this paper, a symmetric two-mode coupler with a 1 μm band is designed and fabricated using the finite element method, beam propagation method and fused pull-cone method, and a set of all-fiber passive mode-locked lasers based on symmetric dual-mode couplers are constructed. Finally, we obtain cylindrical vector beam outputs with central wavelengths of 1038.97 nm/1067.72 nm, a repetition rate of 8.78 MHz, pulse durations of 660 ps/656 ps, maximum average powers of 5.25 mW/5.2 mW, and the high mode purity of TM (transverse magnetic)01 mode and TE (transverse electric)01 mode is 97.18% and 97.07%, respectively.

A modified Jerusalem inspired bandpass FSS for multiband applications based on concentric ring slots

Abstract This paper presents the design of a multi-band planar bandpass Frequency Selective Surface with the novel rings and a modified Jerusalem cross integrated structure. To begin, the proposed FSS array geometry is defined by constructing a unit cell size of order of 0.57 λ 0 × 0.57 λ 0 where λ 0 represents free-space wavelength of the first resonant frequency of the FSS periodic structure using novel concentric rings, leading to low profile design. The array structure is fabricated on the substrate material FR4 with a permittivity of 4.4 and having a thickness of 0.8 mm. Combination of concentric rings and Jerusalem Integrated Structure is examined. Low-profile, simpler design, improved angular and polarization stability are all benefits of the proposed FSS. The proposed FSS structure is designed to obtain a stable frequency response over entire Ku band. The simulated and experimental results are measured in a free space measurement setup, which indicate resonances at 12.39 GHz, 14.63 GHz, 16.11 GHz and 17.82 GHz, exhibits supported band pass frequency ratio 1.43 for Ku band applications. The simulated, equivalent circuit model and experimental results showed that the experimental results agree well with the simulated results for both TE (Transverse Electric) mode and TM (Transverse Magnetic) mode of polarization.

Leaky-Wave Analysis of TM-, TE-, and Hybrid-Polarized Aperture-Fed Bessel-Beam Launchers for Wireless-Power-Transfer Links

Bessel beams (BBs) can be generated at microwave frequencies by means of compact, planar devices based on Fabry–Perot cavity leaky-wave resonators. Most designs are based on the excitation of a single transverse magnetic/transverse electric (TM/TE) leaky mode by means of a vertical electric/magnetic dipole source. In this work, we analyze the important case of a horizontal magnetic dipole, which excites both TM and TE modes, developing an original theoretical framework suitable for resonant radiators. Analytical expressions are provided for the dominant leaky-wave aperture field. The near-field distribution is then evaluated through an accurate numerical integration of the radiating currents and validated through full-wave simulations for the relevant case of a BB launcher when excited by a waveguide-fed slot. Different designs are presented and analyzed in order to obtain TM, TE, and hybrid polarizations, finding in all cases an excellent agreement between simulations and theoretical results. Finally, we evaluate and compare the wireless-power-transfer efficiency of two coupled TM-, TE-, or hybrid-polarized BB launchers when a wireless link is established in the radiative near-field region. Interestingly, full-wave results demonstrate the superior performance of resonant BB launchers in TM or TE polarization with respect to the nonresonant hybrid case.

Complete photonic bandgap in silicon nitride slab assisted by effective index difference between polarizations.

The slab effective index difference between the transverse-electric (TE) and transverse-magnetic (TM) polarizations was utilized to obtain complete photonic bandgap (CPBG) in a silicon nitride (SixNy) photonic crystal slab. For this, coincident frequency range in the TE photonic bandgap (PBG) and TM PBG, which denotes the CPBGs of the slab, must be found with the same structure. Through adjusting the effective index pair of TE and TM polarizations by changing the thickness of the SixNy core layer, and also optimizing the structure parameters within the photonic crystal plane, a large normalized CPBG of 5.62% was theoretically obtained in a slab of SixNy with a refractive index of 2.5. Moreover, based on the obtained CPBG, a microcavity which could support both TE and TM polarization was theoretically demonstrated. The cavity modes for different polarizations were both well confined, which proved the reliability of the CPBG. In addition, using the same method, the lowest refractive index of SixNy on silica slab for a CPBG could be extended to as low as 2. The results indicate that there is potential for development of various high-performance CPBG devices based on SixNy slab technology.

Analysis of Light‐Emission Polarization Ratio in Deep‐Ultraviolet Light‐Emitting Diodes by Considering Random Alloy Fluctuations with the 3D k·p Method

For nitride‐based AlGaN light‐emitting diodes, the fluctuations in the potential caused by alloy disorder can relax the compressive strain in the lower Al (higher Ga) composition sites. However, strain in the quantum wells impacts the bandgap and the transverse magnetic/transverse electric (TE) polarization ratio. Herein, the 6 × 6 k·p method combined with a 3D Poisson, drift diffusion, and localization landscape solver is used to study the changes in the polarization ratio due to random alloy fluctuations. The influence of different Al compositions in the buffer layer is studied. The results show that the TM polarization ratio with alloy fluctuations is higher than that without fluctuations. On increasing the Al composition in the buffer layer, the polarization ratio changes from 0.93 to −0.67 when the Al composition changes from 60% to 100%.

TWO-DIMENSIONAL INVERSION MODELING OF MAGNETOTELLURIC (MT) SYNTHETIC DATA OF A GRABEN STRUCTURE USING SimPEG

The magnetotelluric (MT) method is a passive exploration method in geophysics that utilizes natural electromagnetic waves as a signal source. MT operates in the frequency range of 10 -5 - 10 6 Hz , designed to study the structure of the conductivity below the earth's surface with a depth range from several tens of meters to the upper mantle. In this paper, 2-dimensional inversion modeling is performed on MT synthetic data using the SimPEG software. First, forward modeling is done by making a 2-dimensional conductivity model in the form of a valley (graben), which aims to produce MT synthetic data in TE (transverse electric) mode, TM (transverse magnetic) mode, and a combination of TE mode and TM mode. Next, an inversion modeling is performed on the MT synthetic data by adding a 5% Gaussian noise and a 10 -5 floor as data uncertainty to obtain a 2-dimensional conductivity inversion model. The final result can be validated by comparing the true model and the inversion model and between observational data (synthetic) and predictive predicted data. The results of this study provide a significant fit of the model and suitability of the data. The inversion quality is validated with an RMS Error for TE mode of 0.349%, TM mode of 0.348%, and a combination of TE and TM mode of 0.249%.

Resonant photonic states of quasi one-dimensional photonic quantum well in a rectangular waveguide

We have demonstrated a calculation of the resonant photonic states of quasi one dimensional photonic quantum well for the transverse electric (TE) and transverse magnetic (TM) modes in a rectangular waveguide. The photonic crystal heterostuctures are composed of two different photonic crystals as (AB)m(CD)n(AB)m . In order to solve the resonant photonic states, it is necessary to calculate the transmission functions of TE modes and TM modes. In this work, we consider the propagation of microwaves in photonic crystal heterostructures in our simulation model. The positions and number of the resonant photonic states can be adjusted by the widths of photonic quantum wells. The degenerate resonant photonic states are not existed for both the TE and TM modes, respectively. These results are useful applications in photonic quantum devices and nano technologies.

Ultra-narrow-band Infrared Absorbers Based on Surface Plasmon Resonance

Due to the advantage of improving the sensing performance, narrow-band metamaterial perfect absorbers (MPAs) have attracted much attention in the sensor field. Here, we propose an ultra-narrow-band infrared absorber (UNBIRA) based on localized surface plasmon resonance. The peak absorption of the UNBIRA exceeds 99% with the full width at half maximum (FWHM) of 1.94 nm and 6.32 nm for transverse electric (TE) wave and transverse magnetic (TM) wave in 1.5–1.8 μm. The corresponding Q-factors for TE wave and TM wave are 817 and 266, respectively. When used as an infrared refractive index sensor, the sensitivity of UNBIRA is as high as 1632.5 nm/RIU for TE wave and 1647.5 nm/RIU for TM wave. Accordingly, the figure of merits (FOMs) of 816.2/RIU for TE wave and 260.7/RIU for TM wave are achieved. This UNBIRA possesses a simple geometry structure and an excellent sensing performance, implying a great potential for application of ultra-narrow infrared sensing or detecting.

Highly birefringent slotted core photonic crystal fiber for terahertz waveguiding

A novel porous core photonic crystal fiber (PC-PCF) is suggested and analyzed for terahertz waveguiding. The PC-PCF has a TOPAS background material with suspended asymmetric slotted core. Therefore, high birefringence of 0.09 is achieved with small material absorption losses of 0.016 cm−1 and 0.028 cm−1 for the quasi transverse electric (TE) and quasi transverse magnetic (TM) modes, respectively at f = 1.5 THz. Additionally low bending losses of 2.63 × 10–24 cm−1 and 8.16 × 10–36 cm−1 are obtained for the quasi TE and quasi TM modes, respectively at 1.0 cm bending radius and f = 1.5 THz. Further, the PC-PCF has an ultra-flat low dispersion of 0.54 $$\pm$$ 0.08 ps/THz/cm and 0.94 $$\pm 0.1{ }$$ ps/THz/cm for the quasi TE and TM modes, respectively within the frequency range of 0.8–1.2 THz. Therefore, the reported SSCPCF has a strong potential for usage in the Terahertz regime.

Broadband Low-Profile L-Probe Fed Metasurface Antenna With TM Leaky Wave and TE Surface Wave Resonances

A broadband low-profile L-probe fed metasurface antenna is proposed by well exciting both transverse magnetic (TM) leaky wave and transverse electric (TE) surface wave resonances. The metasurface is composed of an array of rectangular metallic patch cells. An L-shaped probe positioned underneath the finite metasurface is utilized to excite a TM leaky wave resonance and a TE surface wave resonance simultaneously for broadband operation. The dispersion properties of the TM leaky wave and TE surface wave are used to analyze the dual resonance modes. The proposed L-probe fed metasurface antenna achieves a broad −10 dB impedance bandwidth of 34.5% with the peak gain of 10.3 dBi and the front-to-back ratio larger than 18 dB with a low profile of $0.06\lambda _{0}$ , where $\lambda _{0}$ is the free-space wavelength at the center operating frequency.

A Memory-Efficient Formulation of Precise-Integration Time-Domain Method With Riccati Matrix Differential Equations

A novel numerical method, referred to as the Riccati precise-integration time-domain (Riccati-PITD) method, is proposed to reduce the memory requirement of the conventional PITD method. In the Riccati-PITD method, the electromagnetic field components of the transverse electric/transverse magnetic (TE/TM) wave are arranged in a matrix for constructing the Riccati matrix differential equations (RDEs) about Maxwell's curl equations. Then the precise integration technique is adopted for the numerical integration of the RDEs. Theoretical analyses about the memory requirements of the conventional and the Riccati-PITD methods are presented. It is found that the memory requirement can be more greatly reduced by solving the electromagnetic-field components in the form of the matrices in the Riccati-PITD method rather than in the form of the vectors in the conventional PITD method. Numerical examples are also given to confirm that the proposed method has significant advantages over the conventional PITD method with respect to the execution time and the memory requirement.

Theoretical analysis of wide-angle metamaterial absorbers based on equivalent medium theory

In the past decade, most of researchers have been devoted to broadening the bandwidth of absorber. There are few researches on how to achieve wide-angle absorbing materials by detailed theoretical analysis and design guidance. It is still difficult to design wide-angle absorbers. In this paper, based on the equivalent medium theory, the reflectivity of the metamaterial absorber with a single-layered medium backed with metal reflector is analyzed in detail. Starting from the basic electromagnetic theory, the reflection coefficient of the absorber under transverse electric(TE) plane wave and transverse magnetic (TM) plan wave irradiation are derived. And the equivalent electromagnetic parameters of realizing the wide-angle absorbing effect are analyzed, which provide a theoretical basis for designing the wide-angle metamaterial absorber. The theoretical analysis results show that the equivalent electromagnetic parameters required for the medium to achieve low-profile and wide-angle absorbing effect are mainly related to the equivalent permeability and have little relationship with the equivalent permittivity. Moreover, the equivalent electromagnetic parameter value for achieving ultra-wide-angle absorber under TE wave and that under TM wave irradiation are different from each other. In other words, the anisotropic metamaterial with appropriate equivalent permeability has the potential to be used to design the ultra-wide-angle absorbers which are not sensitive to TE waves nor TM waves. In addition, in order to find the theoretically achievable widest absorbing angle value under TE wave and TM wave irradiation, the reflection coefficients at all angles must be less than or equal to –10 dB to obtain the relationship among the equivalent electromagnetic parameters, thickness and angle. The results show that the theoretically achievable widest absorbing angle value is 86.56° under TE wave and TM wave irradiation. The designer can choose the corresponding thickness and permeability from the data obtained from the analysis according to the design requirements. The narrow-band absorbers have limited applications. Therefore, in this paper we also theoretically analyze the values of the equivalent electromagnetic parameters for ahcieving wide-band and wide-angle absorbing materials, and make theoretical verification. The results show that the wide-band and wide-angle absorber can be achieved theoretically, while the equivalent electromagnetic parameters of the medium vary with frequency as some special curves indicate. Although this method is based on the equivalent medium theory and has no direct relationship with the actual structure, it does provide theoretical guidance for designing the wide-angle absorbers.

Broadband Polarization-Independent Directional Coupler Using Asymmetric-Waveguides

A high-performance broadband polarization-independent directional coupler is designed by using asymmetric-waveguides configuration on a silicon-on-insulator platform. Through the design of cascaded directional couplers, the coupling characteristics of the light with the orthogonally polarized transverse electric (TE) and transverse magnetic (TM) can be manipulated, so that the coupling strength could be equivalent between TE and TM polarizations within an ultra-broadband. Couplers with 50% splitting ratio are designed and simulated for operating in the wavelength range from 1450 nm to 1650 nm for both polarizations. Within the 100 nm wavelength range from 1500 nm to 1600 nm, the deviations of splitting ratio for TE polarization and TM polarization are $\pm$ 3.3% and $\pm$ 6.2%, respectively. And within the 200 nm wavelength range from 1450 nm to 1650 nm, the deviations for TE polarization and TM polarization are $\pm$ 9.0% and $\pm$ 7.8%, respectively. The footprint of this polarization-independent directional coupler is only 21 $\mu$ m × 1.6 $\mu$ m.

Omega-Bianisotropic Wire-Loop Huygens’ Metasurface for Reflectionless Wide-Angle Refraction

Huygens’ metasurfaces, typically designed using sub-wavelength unit cells, allow the arbitrary control of electromagnetic waves. Two well-known unit-cell topologies are the wire-loop and stacked-layer designs. The wire-loop unit cell utilizes a conductive wire and loop to control its electric and magnetic responses, while the stacked-layer unit cell utilizes cascaded impedance sheets. Due to their versatility, Huygens’ metasurfaces have been used for numerous applications. One interesting application has been perfect or reflectionless wide-angle refraction. In recent years, it was shown that for perfect refraction, omega-bianisotropy was required in Huygens’ metasurfaces. To realize omega-bianisotropic designs, asymmetric unit cells were proposed and demonstrated utilizing stacked-layer unit cells. However, an omega-bianisotropic wire-loop unit cell for modulated Huygens’ metasurfaces has yet to be demonstrated. This article demonstrates the design, simulation results, and measurements of an omega-bianisotropic wire-loop Huygens’ metasurface for reflectionless wide-angle refraction of 71.8° at 20 GHz. The design and simulation results of both TE and TM transverse-electric (TE) and transverse-magnetic (TM) designs are presented. Additionally, an optimized TM metasurface is experimentally verified through a combination of quasi-optical and far-field measurements. The presented results demonstrate negligible reflections, high scattered refraction efficiency, and a 0.7 GHz bandwidth, which validates the wire-loop unit-cell topology for realizing omega-bianisotropic Huygens’ metasurfaces.

Polarization independent 1 × 3 equal optical power splitter based on self-collimation effect in two-dimensional photonic crystal

A polarization independent 1 × 3 equal optical power splitter (OPS) based on the self-collimation effect in two-dimensional (2-D) photonic crystal (PC) is proposed. Two splitter structures are introduced in the self-collimation 2-D PC, both of which have an air layer and a row of defect air holes. The proposed OPS is simulated using Rsoft software combined with plane wave expansion method and two finite-difference time-domain method. The results show that the beam for transverse electric (TE) mode and transverse magnetic (TM) mode can be self-collimated and divided equally into three outputs at the operating wavelength of 1310 nm. The transmission efficiencies are 95% for TE mode and 93% for TM mode, and the corresponding additional losses are 0.223 and 0.315 dB for TE mode and TM mode, respectively. The steady times are lower than 1.4 ps. The proposed polarization independent 1 × 3 equal OPS will have potential applications in optical fiber communication system.

Fano resonance and polarization transformation induced by interpolarization coupling of Bloch surface waves.

In this work, the resonant coupling behaviors between the transverse-electric (TE) and transverse-magnetic (TM) Bloch surface waves (BSWs) on a dielectric multilayer have been theoretically studied. Due to the different penetration depths in the dielectric multilayer, the TM BSWs and TE BSWs can act as the radiative and dark electromagnetic modes, respectively. By using a rectangular grating on the dielectric multilayer, both Rabi splitting and Fano resonance phenomena based on the coupling of the two BSW modes were demonstrated, through tuning the period of the grating and the azimuthal angle of the incoming wave. Furthermore, by using the temporal coupled-mode theory, we show that the anti-Hermitian coupling between the two BSW modes contributes to the enhanced diffraction and the huge polarization transformation efficiency of incoming waves in the weak coupling regime.

Electro-optic controllable transverse electric/transverse magnetic polarization converter based on the GaN/Al03Ga07N superlattice waveguide

An electro-optic controllable transverse electric/transverse magnetic (TE/TM) polarization converter based on the GaN/Al0.3Ga0.7N superlattice waveguide is proposed for actively controlling the output polarization state. We use the highly accurate and efficient full-vector mode-matching method to evaluate its performance. The result indicates that the output polarization state can be actively controlled in a full 0°–90° range by applying the adjustable voltage on this converter, and that a full TE↔TM conversion is also realizable by applying no voltage. Moreover, this converter has a high conversion efficiency of 99.9%, a low insertion loss of 0.03 dB, and a wide bandwidth (FWHM) of 200 nm. We further investigate the deviation effect of the etching width or the operating wavelength on TE↔TM conversion. In order to counteract deterioration on conversion efficiency brought on by the deviation, a simple compensation method is presented by actively adjusting the voltage to a certain value.

Photonic crystal structures: Beam deflector and beam router

We investigate the optical characteristic, transverse magnetic (TM) and transverse electric (TE) band of two-dimensional (2D) square lattice photonic crystal structure, which is composed of cylindrical air regions positioned at the corners of the square shaped dielectric rods. We obtain the wide photonic bandwidths between TM1–TM2 and TM3–TM4 bands. According to the results, we demonstrate the band gaps close to each other in the TM and TE frequencies for proposed structures. The resulting photonic gaps are formed to be about 8% at the higher frequencies of TE modes (TE4–TE5) and TM modes (TM7–TM8 and TM9–TM10). In addition, we examine isotropically generated structures for light guiding properties and observe that the light is directed in a particular route without using any deflection. We also investigate the self-collimation effect with the designed structure. The obtained results reveal the influences of the radius of cylindrical air holes and the angle between these air holes on absolute and partial photonic band gaps. Moreover, we observe the TM and TE band gaps that overlap. It is thought that the obtained band overlap will provide an easy way to produce the photonic crystals in practical applications like photonic insensitive waveguide. It is also believed that these results can provide the photonic crystal structures to work as a beam deflecting and beam router in integrated optical circuit applications.