Magnetic Photonic Crystals Research Articles

Designing externally controllable optical filters with two-dimensional magnetized plasma photonic crystals

Designing externally controllable optical filters with two-dimensional magnetized plasma photonic crystals

Bandgap structure and density of states of two-dimensional magnetized plasma photonic crystals

In this paper, we study dispersion properties in a two-dimensional magnetized plasma photonic crystal, based on the modified plane wave expansion method. Transverse electric polarization is considered. The influence of different factors such as external magnetic field, lattice constant, dielectric constants of background and central rod, and electron density of plasma in photonic bandgap structure and photonic bandgap map is studied. The photonic density of states is also demonstrated. Results show that a large magnetic field produces more band gaps in higher frequencies. The lattice constant is an important factor in controlling the bandgap structure and it can compensate low magnetic field effect. Using a larger dielectric constant in the background compared to the central dielectric rod leads to more and sharper band gaps in higher frequencies. Electron density of plasma plays an important role in tuning bandgap structure. There would be three or four band areas in the band structure and the band frequencies are larger than the cutoff frequency of plasma.

Newton-ADE-FDTD Method for Oblique Incident Magnetized Time-varying Plasma

In this paper, the Newtonian equation of motion describing the movement of electrons when electromagnetic waves propagate in a magnetized plasma is combined with the traditional auxiliary differential equation finite difference time domain (ADE-FDTD) method. The FDTD iterative formulas of transverse magnetic (TM) wave and transverse electric (TE) wave of the electromagnetic wave obliquely incident on the magnetized time-varying plasma plate are derived. The biggest difference between this method and the ordinary ADE-FDTD algorithm is the addition of the logarithmic derivative of the time-varying plasma electron density to calculate the current density, which is called the Newton-ADE-FDTD method. Through Example 1, the reflection coefficient of electromagnetic wave incident on the magnetization time-varying plasma plate was calculated, and the correctness of the improved algorithm was verified. At the same time, the Newton-ADE-FDTD algorithm is used to calculate the reflection coefficient of electromagnetic waves incident on the magnetized plasma-dielectric photonic crystal. The results show that different incident angles have a greater impact on the reflection coefficients of left-handed circularly polarized wave (LCP) and right-handed circularly polarizedwave (RCP).

Lipophilic Magnetic Photonic Nanochains for Practical Anticounterfeiting.

Magnetic photonic crystals (PCs) possess attractive magnetic orientation, flexible pattern designability, and abundant angle-dependent colors, providing immense potential in anticounterfeiting field. However, all-solid magnetic PCs-based labels generally suffer from incompatibility with screen printing techniques, and inferior environmental endurance and mechanical properties. Herein, by developing a selective concentration polymerization method under magnetic field (H) in microheterogenous dimethyl sulfoxide-water binary solvents, individual tens-of-micrometer-length lipophilic magnetic photonic nanochains (PNCs) of full-width at half-maxima below 30nm are fabricated, which, after simply dispersed in solvent-free cycloaliphatic epoxy resin, can be formulated as photonic inks to print robust anticounterfeiting labels through an H-assisted screen-printing technology. The as-printed labels possess vivid optically variable effects (OVEs) associated with the spatial distribution of H directionality, which are easy to identify by the naked eye but difficult to imitate and duplicate, while they show excellent environmental resistance and mechanical properties, promising practical applications in banknotes and high-grade commodities. The polymerization mechanism of the lipophilic PNCs is elucidated, and the OVEs are deciphered in numerical simulation. Besides an efficient way to build organic-inorganic hybrid nanostructures, the work provides advanced structural color pigments to achieve the practical application of magnetic PCs in such an anticounterfeiting field.

Multi-frequency coherent perfect absorption in the one-dimensional magnetized ferrite photonic structure

A controllable multi-frequency absorption structure predicated on a one-dimensional magnetized ferrite photonic crystals (MFPCs) that achieves coherent perfect absorption is designed and further analyzed by utilizing the transfer matrix method. By introducing the filter structures to the MFPC and using the gradient descent optimization algorithms to optimize its layer parameters, the multi-frequency coherent absorption curve is obtained. The suggested MFPC brings out about six absorption peaks whose absorptance can be higher than 0.99 at the same time under the transverse electric mode. Moreover, the absorptance can be regulated from 0.99 to less than 0.1 by merely changing the phase deviation between the two incident waves to the front and rear surfaces. Besides, the studied results demonstrate that the intensity of coherent absorption and the position of absorption peaks can be adapted by altering the magnetic field and the thicknesses of ferrite layers. It follows that the absorption peaks can cover most frequency points from 58.6 to 65.9 THz via changing the thicknesses of the external magnetic field and ferrite layers. Moreover, the structure also has the potential for wide-angle absorption. This research furnishes a significant reference for the design of the multi-frequency absorption optoelectronic device and phase sensor.

Nonreciprocal Goos–Hänchen effect at the reflection of electromagnetic waves from the one-dimensional magnetized ferrite photonic crystals

Leveraging the traditional transfer matrix and stationary phase methods, the nonreciprocal Goos–Hänchen (GH) phenomena for the electromagnetic (EM) waves reflected at the surface of the one-dimensional photonic crystals with ferrite layers and dielectric layers are investigated numerically. The GH effect (the peak of the lateral shift value up to over 200 times the wavelength) produced by the forward and backward incidence of EM waves under the transverse electric wave is identified to arise at significantly different frequency positions in the terahertz (THz) regime, whereas the transverse magnetic wave produces almost no GH effect under the same condition. Based on such a nonreciprocal phenomenon, the effect of the incident angle on the nonreciprocal properties is covered initially, for every 20° increase in the angle of the incident TE wave, the frequency span at which the two GH shift peaks emerge will decrease by 0.1 THz. In addition, the thicknesses of dielectric layers are modified separately, and distinct sensitivities of them to the nonreciprocal phenomenon are displayed. Lastly, through the regulation of the external magnetic fields of ferrite layers, the nonreciprocal effect can be selectively presented in multiple forms, which provides a novel pathway to design nonreciprocal sensors.

Gas sensing applications using magnetized cold plasma multilayers

In this paper, we theoretically propose a novel magnetic field-dependent sensor using omnidirectional magnetized cold plasma photonic crystal in one dimension for TE polarization. The structure consists of asymmetric two periodic arrays from magnetized cold plasma and sample cavity layer. Between the periodic arrays, a sample cavity is sandwiched between two quartz layers. The methodology of the proposed detector depends on the appearance of a sensitive defect mode. The results clear that the defect mode frequency depends significantly on the refractive index of the sample, and it is extremely sensitive to incident angle changes, applied magnetic field, the number density of electrons, and sample layer thickness. The optimized proposed sensor has high sensitivity of 15.14 GHz/RIU, quality-factor of 527.32, and figure of merit of 1066.20 RIU−1, where RIU means refractive index unit. So, the proposed sensor can aid in solving many challenges in chemical and environmental applications.

Cross-waveguide based on sunflower-type eightfold quasiperiodic magnetic photonic crystal

Nonreciprocal waveguides play a key role in optical communication devices due to their robustness in unidirectional transmission along the edge. We proposed a unidirectional air guide waveguide structure based on eightfold sunflower quasiperiodic magnetic photonic crystal (PC) that has a large working bandwidth, high transmission efficiency, and strong stability. A cross-waveguide is constructed in the sunflower-type eightfold quasiperiodic magnetic PC structure. It can be used as a single-pole double-throw switch by changing the external bias magnetic field direction, in which the isolation is over 28 dB in the microwave band from 4.21 to 4.5 GHz and insertion loss is close to 0.001 dB. It can also achieve 1 × 2 or 1 × 3 equal ratio beam splitting, with a total transmission rate of close to 100% and transmission loss of 0.001 dB. The cross-waveguide is simple in structure and easy to integrate and manufacture, and it has a wide range of functions that have tremendous potential applications in optical communication systems.

Light intensity imbalance in 2D magnetic photonic crystals with a real number in off-diagonal components of a dielectric tensor

Magneto-optical effects are caused by parameters of the off-diagonal components in the dielectric tensor of materials, which is a complex number. Because the real parts of off-diagonal components rotate the photo-induced polarization in the materials from the direction of the incident light electric field, the parts must become one of the effective parameters for light energy flow control in photonic crystals. In this study, we theoretically proposed a mechanism to realize light intensity imbalance to the left and right by inverting the sign of the real parts for 2D magnetic photonic crystals based on a finite-difference time-domain simulation and photonic band calculations. Our analyzes reveal that the maximal intensity peaks of light magnetic field distributions rotate ∼60∘ around the hole of the crystal at the Γ point in the Brillouin zone, and these rotations are caused by the real parts. The imbalance is caused by the deflections of light energy flow owing to the rotation, which are explained based on the following two mechanisms: the walk-off phenomenon and uneven bifurcation. Furthermore, the proposed mechanism was experimentally confirmed by observing the imbalance in the scattered light intensity from the surface of rough-cutting magnetic photonic crystals fabricated from a cerium-substituted yttrium iron garnet. The results of this study serve as a foundation for the development of light energy flow control by engineering photonic crystals using the real part of the off-diagonal components in dielectric tensors.

The visible region transitions measuring of one-dimensional magnetic photonic crystal with structure [formula omitted] by magnetic circular dichroism method

Magnetic circular dichroism (MCD) spectroscopy is a powerful method to investigate and characterize magnetic materials' spin and excited electronic states. This spectroscopy method, relying on measuring the absorption difference between left circularly polarized (LCP) light and right circularly polarized (RCP) light is more precise than other spectroscopic methods. It was induced in a sample by a strong magnetic field oriented parallel to light propagation. A magnetic circular dichroism measurement system was launched in this study. The measurement setup consists of a collimator xenon lamp crossing at a polarizer angle to the main modulator axis. The obtained circular polarized light passes through the sample and is finally collected by a spectrometer. The study analyzed magnetic photonic crystal positions and transition types TiO2/SiO26/Bi:YIG/TiO2/SiO26 in the range of 500 to 700 nm; three paramagnetic transitions 6A1(6S)→4T2(4G), 6A1(6S)→4T1(4G) and, 6A1g(6S)→6T2g(6G) due to crystal field transitions at 510, 550, 580, 610, and 680 nm were identified.

A microfluidics‐dispensing‐printing strategy for Janus photonic crystal microspheres towards smart patterned displays

AbstractFrom the implementation point of view, the printable magnetic Janus colloidal photonic crystals (CPCs) microspheres are highly desirable. Herein, we developed a dispensing‐printing strategy for magnetic Janus CPCs display via a microfluidics‐automatic printing system. Monodisperse core/shell colloidal particles and magnetic Fe3O4 nanoparticles precursor serve as inks. Based on the equilibrium of three‐phase interfacial tensions, Janus structure is successfully formed, followed by UV irradiation and self‐assembly of colloid particle to generate magnetic Janus CPCs microspheres. Notably, this method shows distinct superiority with highly uniform Janus CPCs structure, where the TMPTA/Fe3O4 hemisphere is in the bottom side while CPCs hemisphere is in the top side. Thus, by using Janus CPCs microspheres with two different structural colors as pixel points, a pattern with red flower and green leaf is achieved. Moreover, 1D linear Janus CPCs pattern encapsulated by hydrogel is also fabricated. Both the color and the shape can be changed under the traction of magnets, showing great potentials in flexible smart displays. We believe this work not only offers a new feasible pathway to construct magnetic Janus CPCs patterns by a dispensing‐printable fashion, but also provides new opportunities for flexible and smart displays.

Externally tunable multichannel filtering applications of organic material based 1D magnetic cold-plasma photonic crystals.

In the present research work, we employed the transfer matrix method (TMM) in addition to MATLAB software to examine the transmission properties of various organic-based one-dimensional (1D) magnetic cold-plasma photonic crystals (MCPPhCs). The proposed structures were found to be made up of periodic layers of organic materials and magnetic cold-plasma (MCP) at normal incidence. An external magnetic field (B) polarized in right-hand (RH) and left-hand (LH) configurations was applied on 1D MCPPhCs. In this study, four organic materials, namely pentane, hexane, heptane, and octane, were chosen to design four 1D photonic crystals (PCs), named as PC1 (pentane-MCP), PC2 (hexane-MCP), PC3 (heptane-MCP), and PC4 (octane-MCP). Our results indicated that the central frequency of the resonant peaks of unit transmission inside the photonic band-gap (PBG) of the respective organic PCs could be tuned towards the higher or lower frequency side by applying B polarized in RH and LH configurations, respectively. We also studied the effect of the period number N to produce closely spaced N-1 transmission channels of unit transmission inside the PBG of all four organic PCs. By increasing the period number N we could increase the number of transmission channels inside the PBG as per our desire. These multiple resonant peaks of unit transmission inside PBG could be easily modulated inside the PBG to accommodate new frequencies by applying B polarized in either RH or LH configurations, respectively. Moreover, our results showed that under the RH configuration, increasing B resulted in a shifting of the resonant peak towards the higher frequency side with a reduction in its full width half maximum (FWHM), whereas the findings were the opposite in the case of increasing B under the LH configuration. These findings may be beneficial for designing externally tuneable organic chemical sensors in the microwave frequency region.

Tunable enhanced Faraday rotation in a defected plasma photonic crystal under external magnetic field with different declinations

Magneto-optical responses and the potential for tunability when changing the variables of a one-dimensional defected magnetized plasma photonic crystal have been studied using a transfer matrix method for operation in the mm-range wavelength region. The effect of the number and dielectric defect layer thickness as well as the intensity and declination angle of magnetic field on transmittance, Faraday rotation, and its ellipticity has been investigated. The results demonstrate the ability to alter the resonant modes frequency at multiple levels of precision. The structures with four, six, and eight defect layers have been investigated. The number of defect dielectric layers changes the number of resonance modes. A single defect mode appears within the photonic bandgap with four defect dielectric layers while two defect modes were observed with six layers, and three modes with eight layers. An increase in magnetic field declination decreased the Faraday rotation intensity and width of Faraday resonance mode.

Theoretical analysis of glide-Z2 magnetic topological photonic crystals.

Gapped systems with glide symmetry can be characterized by a Z2 topological invariant. We study the magnetic photonic crystal with a gap between the second and third lowest bands, which is characterized by the nontrivial glide-Z2 topological invariant that can be determined by symmetry-based indicators. We show that under the space group No. 230 (I a3¯d), the topological invariant is equal to a half of the number of photonic bands below the gap. Therefore, the band gap between the second and third lowest bands is always topologically nontrivial, and to realize the topological phase, we need to open a gap for the Dirac point at the P point by breaking time-reversal symmetry. With staggered magnetization, the photonic bands are gapped and the photonic crystal becomes topological, whereas with uniform magnetization, a gap does not open, which can be attributed to the minimal band connectivity exceeding two in this case. By introducing the notion of Wyckoff positions, we show how the topological characteristics are determined from the structure of the photonic crystals.

Dual-polarization topological phases and phase transition in magnetic photonic crystalline insulator

Two-dimensional topological photonic crystals have rapidly emerged as a recent and fascinating branch of photonic research. However, most of them were limited to a specific type of polarization, TE or TM polarization. Here, we explored the dual-polarization topological phases in two-dimensional magnetic photonic crystal (PC) which are composed of ferrite rod clusters in the plasma background. Under the perturbations of the bias magnetic field and/or the cluster distortion in the unit cell, the PC exhibited dual-polarization topological phases, including the quantum Hall (QH) phase, the higher-order quantum spin Hall (HO-QSH) phase and the conventional insulator (CI) phase. We studied the topological nature of these phases by the Wilson loop, Chern number, and unidirectional edge states. Intriguingly, we showed that the HO-QSH phases could present in PC of C 3v symmetry instead of being restricted to C 6v symmetry. The lower symmetry enlarges the gap in the edge states, which helps for the emergence of corner states. By continuously deforming the unit cell configuration, we demonstrated the phase transition in the system was dual-polarization. Our results extend the topological phases in the PCs and pave the way for the dual-polarization topological devices and their applications.

Investigation on the nonreciprocal properties of one-dimensional cylindrical magnetized plasma photonic crystals.

In this paper, the equations for the transfer matrix method of one-dimensional cylindrical magnetized plasma photonic crystals are proposed, and its nonreciprocal properties based on the Thue-Morse sequence are also studied. By adding the influence of the magnetic field into Maxwell's equations in the cylindrical coordinate system, the transmission matrix equation of cylindrical wave propagation in the cylindrical medium is obtained and a quasi-periodic structure with the Thue-Morse sequence is designed to study its nonreciprocal features. By considering Maxwell's equations and the equations of motion of charged particles, the relative dielectric function of plasma under the $z$-axis magnetic field is achieved. Considering the influences of this dielectric function in the cylindrical coordinate system, the transmission matrix equations of cylindrical wave propagation in the cylindrical medium are derived, and those equations are used to design a cylindrical structure with two layers of ordinary medium and one layer of plasma satisfying the Thue-Morse sequence. It is concluded that the nonreciprocal phenomenon becomes more and more obvious with the increase of the plasma frequency, the relative dielectric constant of the medium, and the incident angle. But with the increase of ${\omega _c}$, the nonreciprocal propagation is attenuated, and there is no significant change when the collision frequency is enlarging.

Tunable Fano resonance in one-dimensional magnetized plasmon photonic crystals

In this paper, the reflection characteristics of one-dimensional (1D) magnetized plasma photonic crystals (MPPCs) are studied by using the transfer matrix method. The given structure is made up of binary photonic crystals whose unit only contains two plasma layers with different plasma frequencies and a dielectric material layer at the end. The phenomenon of Fano resonance can be realized by such a simple periodic asymmetric structure. By applying the external applied magnetic field, the properties and transmission metrics of the presented MPPCs can be achieved. The numerical results reveal that two narrow and asymmetric linear reflection peaks will appear, and a phenomenon of Fano resonance can be observed. The influences of refractive index, period constant, incident angle, and magnetized plasma parameters on the obtained Fano resonance also are investigated. The analyzed results demonstrate that the tailored Fano resonance can appear in the proposed 1D MPPCs, and the above parameters can affect its features. The stated 1D MPPCs can be used in the sensors, slow light optical devices, and so on.

Nonreciprocal absorption characteristics of one-dimensional cylindrical magnetized plasma photonic crystals

By combining the propagation matrix of planar magnetized plasma photonic crystals with that of the cylindrical non-magnetized medium, the transfer matrix equation of the cylindrical magnetized plasma photonic crystals is obtained. Applying this equation to the cylindrical structure, a quasi-periodic structure conforming to the Pell sequence is designed, which has good nonreciprocal property. Therefore, the absorptance of light propagating forward and backward in this structure are studied respectively. The concept of contrast ratio (D C ), calculated from the absorption of the forward and backward propagation of electromagnetic waves in the structure, is used to compare the degree of difference between the two. It is found that the nonreciprocal propagation becomes larger with the increase of the azimuth modulus and the relative dielectric constant of the medium, increases first, and then decreases with the increase of the incident angle, but does not change obviously when the plasma collision frequency and the cyclotron frequency of the plasma are getting larger. The absorptance decreases with the increase of azimuth modulus, relative dielectric constant, and plasma cyclotron frequency, and becomes better with the increase of the plasma collision frequency. However, when the incident angle gets larger, the absorptance becomes better at first and then gets worse.

Photonic crystals with a touch of topology

Topological Materials Manmade photonic crystals offer a flexible platform for controlling the propagation and flow of light. Such control can be extended across the electromagnetic spectrum by correctly engineering the bandgap. Limitations in the fabrication process, however, can result in structural imperfections that allow the light or energy to leak out. Wang et al. add magnetism to the mix to form heterostructures of magnetic photonic crystals. They demonstrate that, for microwaves, this magnetic addition provides a topological aspect to the band structure, resulting in the propagation of the microwaves in one direction that is robust to defects. The ability to controllably route and collimate electromagnetic waves also could be applied to electronic and phononic waveguide systems. Phys. Rev. Lett. 126 , 067401 (2021).

Topological One-Way Large-Area Waveguide States in Magnetic Photonic Crystals.

We have theoretically and experimentally achieved large-area one-way transport by using heterostructures consisting of a domain of an ordinary photonic crystal sandwiched between two domains of magnetic photonic crystals. The nonmagnetized domain carries two orthogonal one-way waveguide states which have amplitude uniformly distributed over a large area. We show that such one-way waveguide states can be used to abruptly narrow the beam width of an extended state to concentrate energy, and the transport is robust against different kinds of defects and imperfections. They are also immune to the Anderson-type localization when large randomness is introduced.