Fig 2
(a) EFCs of an isotropic and homogeneous medium (top) and schematic EFCs of 2D photonic crystals (middle and bottom). The k vector in the crystals is determined by the continuity of the tangential component of the incident wave-vector across the boundary. (b)-Light propagation direction in the three media.
Source publication
In this letter, we report a novel approach in demultiplexer design by performing wavelength separation in hetero photonic crystal (HPC) with an oblique boundary. First step, demultiplexing action is considered like ordinary demultiplexers using wavelength dispersion in photonic crystals. Contrary to ordinary demultiplexers, the oblique boundary in...
Contexts in source publication
Context 1
... sequence of events happens if we have a hetero photonic crystal (HPC) structure. As shown in Fig. 2-a, the intersections of a vertical line originating from the wavevector in medium 1 with crystals' EFCs determine the wavevectors of excited waves in the two crystals. This means that multi-stage demultiplexing cannot be obtained by these structures because the vertical line does not change course by just adding different media. In ...
Context 2
... originating from the wavevector in medium 1 with crystals' EFCs determine the wavevectors of excited waves in the two crystals. This means that multi-stage demultiplexing cannot be obtained by these structures because the vertical line does not change course by just adding different media. In other words, a better demultiplexer than that shown in Fig. 2 can be obtained by just devoting the whole space occupied by the two crystals to the more dispersive ...
Citations
... In this paper, by employing this strategy, a boundary between positive and negative refraction for the incident spectrum in the photonic crystal is created to enhance wavelength separation in the demultiplexer. The separated wavelengths then impinge on a second crystal with an oblique boundary to change their Bloch wavenumbers and increase the separation angles even further according to the technique described in [15]. ...
... The design technique described in the previous section can be combined with the technique reported in [15] to even further improve the demultiplexing properties of the design. As is clarified in [15], an oblique boundary between two photonic crystals can change the Bloch wavenumber of the propagating wave and change its traveling direction as shown in Fig. 10. ...
... The design technique described in the previous section can be combined with the technique reported in [15] to even further improve the demultiplexing properties of the design. As is clarified in [15], an oblique boundary between two photonic crystals can change the Bloch wavenumber of the propagating wave and change its traveling direction as shown in Fig. 10. The Bloch wavevector in the first crystal can be determined by drawing a vertical line from the initial wavevector. ...
In this paper, a systematic approach is employed to design a photonic crystal with a boundary between positive and negative refraction to boost the refractive properties of the crystal. Mathematical techniques are employed to turn the process of equi-frequency contours’ engineering into a nearly mechanical process free of trial-and-error steps. The designed demultiplexer’s operational characteristics are then further improved by adding a second photonic crystal with an oblique boundary. The refracted beams in the first crystal impinge on an oblique interface of the second photonic crystal to experience a change in Bloch wavenumbers and even greater refraction angles so that a novel super-dispersive two-step optical demultiplexer is made. A beam divergence of 161 degrees is obtained for an input spectrum of λ = [1474 nm, 1550 nm] which is quite superior than the design’s counterparts.
Graphical abstract
... In this paper, by employing this strategy, a boundary between positive and negative refraction for the incident spectrum in the photonic crystal is created to enhance wavelength separation in the demultiplexer. The separated wavelengths then impinge on a second crystal with an oblique boundary to change their Bloch wavenumbers and increase the separation angles even further according to the technique described in [15]. ...
... The design technique described in the previous section can be combined with the technique reported in [15] to even further improve the demultiplexing properties of the design. As is clarified in [15], an oblique boundary between two photonic crystals can change the Bloch wavenumber of the propagating wave and change its traveling direction as shown in Fig. 10. ...
... The design technique described in the previous section can be combined with the technique reported in [15] to even further improve the demultiplexing properties of the design. As is clarified in [15], an oblique boundary between two photonic crystals can change the Bloch wavenumber of the propagating wave and change its traveling direction as shown in Fig. 10. The Bloch wavevector in the first crystal can be determined by drawing a vertical line from the initial wavevector. ...
In this paper, a systematic approach is employed to design a photonic crystal with a boundary between positive and negative refraction to boost the refractive properties of the crystal. Mathematical techniques are employed to turn the process of EFC engineering into a nearly mechanical process free of trial-and-error steps. The designed demultiplexers operational characteristics are then further improved by adding a second photonic crystal with an oblique boundary. The refracted beams in the first crystal impinge on an oblique interface of the second photonic crystal to experience a change in Bloch wavenumbers and even greater refraction angles so that a novel super-dispersive two-step optical demultiplexer is made. A beam divergence of 161 degrees is obtained for an input spectrum of {\lambda}= [1474nm, 1550nm].
... The EOT only appears when a TM polarized wave is incident upon this structure even with very narrow slits [16]. For the sake of simplicity, only the normal incident is studied here with the incident wave expressed with Magnetic field and Electric field as Based on Floquet-Bloch theory, the reflected ( , ) and transmitted waves ( , ) can be written as an infinite series of diffracted modes [17][18][19][20]: Note that the (1) and (2) are written for < 0, while the equation (3) is for > . Also, the wave number components are defined as: ...
In this paper, two distinct light transmission peaks, named EOT and Fabry-Perot resonances, in slit arrays of metallic films are analyzed using mode matching method and simulated by FEM. These two resonances are known to be different in the transmission bandwidth, resonance frequency, and in the transverse magnetic field pattern in the resonance frequencies. However, it is observed herein that the variation in the structure's thickness can convert EOT resonances to Fabry-Perot and vice versa.
... Photonic crystals (PhCs) have been explored extensively for their ability to control the propagation of light [1,2]. Among those novel phenomena due to the intrinsic dispersion relations, superprism [3][4][5][6][7] and super-collimation [8][9][10][11][12][13][14] are the ones which attract much attention. Most traditional superprisms are designed at the sharp corner regions of the equal-frequency contour (EFC) [4,[15][16][17] which results in unwanted beam broadening. ...
We investigate the beam propagation behavior in the photonic crystal (PhC) of the local super-collimation (LSC) regions both theoretically and numerically. A theory based on the cubic dispersion model in the LSC regions is established, which is a powerful tool to predict the beam evolution after a long propagation distance. The numerical experiments are also implemented, whose results agree well with those from our theory. Both the theoretical and simulation results show the new phenomenon of the asymmetric beam broadening for beams in the LSC regions, which is quite different from the traditional symmetric broadening. Physical reasons of such asymmetric broadening are explained by the cubic dispersion model and the solution to suppress the asymmetric broadening is proposed. Since the LSC beams could be widely used in photonic devices, such as hypersensitive spectrometers and demultiplexers, the deep insights of the beam propagation behavior in the LSC regions can help us to optimize our designs, such as choosing the proper beam width and the proper working range in the phase space.
... Metamaterials have attracted great attention due to their abundant properties and potential applications in both science and technology. Many interesting phenomena, such as slow light [1], negative refraction [2], super-collimation [3,4], and superprism effect [5][6][7], have been explored in theoretical and experimental works. Hyperbolic metamaterials (HMMs) are highly anisotropic metamaterials whose effective electric and/or magnetic tensors have opposite-sign principal components. ...
... The transmission behaviors for two topological types of EFCs of the graphene HMM are further studied. Equation (5) shows that as ε || varies from positive to negative values, the EFC diagram changes from an ellipse to a hyperbola, which are clearly shown by the yellow EFC curves in Figs. 3(a1) and 3(b1). ...
... 3(a1) and 3(b1). For the case of μ c = 0.2 eV in Fig. 3(a1), ε || is 1.58, which together with ε ⊥ = 2.2 makes the EFC to be an ellipse according to Eq. (5). Such an elliptic EFC shows slightly anisotropy. ...
We theoretically study the topological transition of dispersion types and propose a tunable planar lens based on graphene hyperbolic metamaterials (HMMs). By tuning the chemical potential (μc) of graphene, the dispersion relation of the HMM is topologically switchable between ellipse (μc<0.6 eV) and hyperbola (μc>0.6 eV) where positive and negative refractions occur respectively. Especially, for μc>0.6 eV, a Gaussian light beam is negatively refracted twice and focuses at a far-field point finally, acting well as a planar lens. Furthermore, its focal length l can be sensitively tuned by controlling μc, and Δl reaches 260 μm (from 528 to 268 μm) while μc varies with only 0.05 eV (from 0.65 to 0.7 eV). The physical reason is attributed to the different anisotropy degrees of EFCs for different μc. Such a compact, high-speed, and sensitively tunable planar lens holds great promise in photonic integration, photonic imaging, and directional coupling applications.
... 7,8 In a recent study, 9 another parameter named angular-group dispersion-bandwidth-product is defined as a criterion of the superprism effect for spectroscopic applications. In Ref. 10, authors attempted to increase the wavelength sensitivity by using hetero PhCs with oblique boundaries for efficient wavelength demultiplexing applications. 10 A low symmetry feature that constructs the main part of the work is considered, we can refer to Ref. 11, which has similar features to the concept. ...
... In Ref. 10, authors attempted to increase the wavelength sensitivity by using hetero PhCs with oblique boundaries for efficient wavelength demultiplexing applications. 10 A low symmetry feature that constructs the main part of the work is considered, we can refer to Ref. 11, which has similar features to the concept. Even though the study 11 numerically examines anomalous diffractive characteristic (tilted self-collimation effect) due to introduced structural asymmetry to the PhC structure, in this work differently from that report we present the super-dispersive phenomenon that shows superprism and self-collimation effects simultaneously which is the main goal of the work. ...
We propose compact S-vector superprism providing broadband wavelength sensitivity within a/lambda=0.610–0.635, where “a” is the lattice constant, k is the incident wavelength, and S denotes the Poynting vector. The reported configuration overcomes strong beam divergence and complex beam generation due to the self-collimation ability of the low symmetric primitive photonic crystal (PhC) cells. Analytical calculations of equi-frequency contours, photonic band structures, and group velocity dispersions are performed by solving Maxwell’s equations and using the plane wave expansion method. Besides, finite-difference time-domain analyses are also conducted. The
designed superprism induces large refracted angle variation for different frequencies when the incident angle is fixed: 4% change of incident frequencies results in approximately 40 deflected angle difference with a maximum 68.9 deflection angle inside the PhC. Meanwhile, for a fixed incident wavelength, a large output variation occurs if the incident angle is altered. Microwave experimental results are found to be in good agreement with the numerical analyses.
The concept of multifunctional reflection-mode gratings that are based on rod-type photonic crystals (PhCs) with [Formula: see text] symmetry is introduced. The specific modal properties lead to the vanishing dependence of the first-negative-order maximum on the angle of incidence and the nearly sinusoidal redistribution of the incident-wave energy between zero order (specular reflection) and first negative diffraction order (deflection) at frequency variation. These features are key enablers of diverse functionalities and the merging of different functionalities into one structure. The elementary functionalities, of which multifunctional scenarios can be designed, include but are not restricted to multiband spatial filtering, multiband splitting, retroreflection, and demultiplexing. The proposed structures are capable of multifunctional operation in the case of a single polychromatic incident wave or multiple mono-/polychromatic waves incident at different angles. The generalized demultiplexing is possible in the case of several polychromatic waves. The aforementioned deflection properties yield merging demultiplexing with splitting in one functionality. In turn, it may contribute to more complex multifunctional scenarios. Finally, the proposed PhC gratings are studied in transmissive configuration, in which they show some unusual properties.
The concept of multifunctional reflection-mode gratings based on rod-type photonic crystals with C2 symmetry is introduced and examined. The specific modal properties lead to the vanishing dependence of the first-negative-order maximum on the angle of incidence within a wide range, and the nearly sinusoidal redistribution of the incident-wave energy between zero order (specular reflection) and first negative diffraction order (deflection) at frequency variation that are the key features enabling various functionalities in one structure and functionality merging. The elementary functionalities offered by the studied structures, of which multifunctional scenarios can be designed, include but are not restricted to multiband spatial filtering, multiband splitting, and demultiplexing. The proposed structures are shown to be capable in multifunctional operation in case of an obliquely incident polychromatic wave. The generalized demultiplexing is demonstrated for the case when several polychromatic wavesare incident at different angles. The same deflection properties yield multiband splitting, and merging demultiplexing and splitting functionalties in one functionality, which may contribute to various multifunctional scenarios. The proposed gratings arealso studied in transmissive configuration.
In the present paper, a four-channel optical demultiplexer (DMUX) based on two-dimensional photonic crystal has been presented. In this optical demultiplexer, filtering and wavelength separation were performed using point defects between the output and input waveguides. To design the optical demultiplexer, a 31 × 21 resonance filter with a lattice constant (Λ) of 0.54 μm and the radius of the dielectric rods of 0.2Λ was first designed, and then it was expanded to obtain a four-channel 31 × 41 demultiplexer. The output wave spectrum was measured for four channels in the range of 1541.5 nm to 1557.6 nm. The average quality factor of 2567, the average crosstalk of − 25 dB, and the transmission coefficient of higher than 97% were obtained.
