Photonic Crystal Heterostructure Research Articles

Multi passbands filter for THz applications based on the one-dimensional photonic crystals heterostructure

In this work, we propose a heterostructure of different photonic crystal designs for multi passband filter applications at THz region. The suggested heterostructure is composed of regular photonic crystal (PC) designs and quasi-periodic photonic crystal (QPPC) of Fibonacci sequence. In our study, the QPPC is inserted between the two regular PC designs. By using the well-known transfer matrix method (TMM), we theoretically investigated the interaction of the incident electromagnetic waves with the proposed PC heterostructure. The numerical results demonstrate resonant peaks appeared in the transmittance spectrum of the proposed design. The tunability feature of the resonant peak is presented by controlling some of the design parameters such as the periodicity number of Fibonacci sequence value and the thickness of the constituent layers. In addition to that, we demonstrated the effect of the hydrostatic pressure on the resulted resonant peaks and the transmittivity of the proposed filter as well. The tunability feature of the resulted resonant peaks make our proposed filter act as multi passband filter via controlling the design parameters at the THz region.

Enhancement and manipulation of group delay based on topological edge state in one-dimensional photonic crystal with graphene.

In this paper, the reflected and transmitted group delay from a one-dimensional photonic crystal heterostructure with graphene at communication band are investigated theoretically. It is shown that the negative reflected group delay of the beam in this structure can be significantly enhanced and can be switched to positive. The large reflected group delay originates from the sharp phase change caused by the excitation of topological edge state at the interface between the two one-dimensional photonic crystals. Besides, the introduction of graphene provides an effective approach for the dynamic control of the group delay. It is clear that the positive and negative group delay can be actively manipulated through the Fermi energy and the relaxation time of the graphene. In addition, we also investigate the transmitted group delay of the structure, which is much less than the reflected one. The enhanced and tunable delay scheme is promising for fabricating optical delay devices like optical buffer, all-optical delays and other applications at optical communication band.

Angular-adjustable single-channel narrow-band filter based on one-dimensional photonic crystal heterostructure

In this work, we designed a narrow-band filter based on a one-dimensional photonic crystal heterostructure featuring an angle-adjustable single-channel. The design presented here is based on a quarter-wave reflector with a mirror defect layer in the middle of the structure. By combining two defective one-dimensional photonic crystals (PCs), we obtained a heterostructure in which the two sub-PCs had the wavelengths of their defect modes, that is, the same at one incident angle and different at all other incident angles. This structure possessed the single-channel resonant peak in the transmission spectrum under either a normal or an oblique incident angle, and the angle-adjustability was related to the two modifying parameters. The filter based on this heterostructure possessed not only a narrow passband but also a sharp angular pass breadth. These properties have potential applications in angular tunable, single-channel narrow-band filters.

Light localization in one-dimensional photonic crystal heterostructures

Effects of both metamaterial inclusion and lack of inversion symmetry on the localized modes in one-dimensional photonic heterostructures under normal incidence are investigated. Each structure consists of two semi-infinite photonic crystals separated by an interface or by several layers. A general condition for light localization between semi-infinite crystals is given by parallelism between two-dimensional vectors in the electromagnetic (H, E) space. The case of a defective photonic crystal is recovered by joining crystals having the same unit cell. The defect modes display leftward and rightward damped oscillations with the same ratio, even when the unit cell lacks inversion symmetry. Their frequencies are found in good agreement with peaks of the transmittance through truncated structures. In heterostructures including metamaterials, an anomalous exponential decay of the magnetic field is found near one edge of the zero-〈n〉 gap.

Faraday rotator made of conjugated magneto active photonic crystal heterostructures

Two defective conjugated magneto active photonic crystals are proposed in this paper for fabrication of Faraday rotators. Optical features of the suggested structures are studied using 4 × 4 transfer matrix method and taking into consideration of the couplings of polarization states. Band structure of the crystals including generation of stop bands and resonant modes localizations are studied by exploring the dependence of the crystals' transmittance on the period number of the layers. It is shown that desirable responses are obtained by just very low number of periods. Furthermore, optical anisotropy of the crystals is considered to be purely magnetic field-induced. Then in addition to studying the dependencies on structural parameters, connection between wave incident angle and magneto-optical effects (Faraday rotations and changes of the ellipticity angle) are discussed in detail. Results clearly show the ease of tunability of the structures' responses in this way which is of prime importance from experimental point of view. Furthermore, the proposed structures offer remarkable Faraday rotation angles when transmittance amounts remain high enough simultaneously. Thus it seems that these crystals might be useful for fabrication of polarization dependent sensor/transducers based on Faraday rotators which are vital elements in development of integrated circuits as well as imaging systems.

Dual‐Band Absorption Effect in a Topological‐Insulator‐Based Tamm Plasmon Multilayer System

Topological insulator materials have attracted greater attention in recent years due to their conducting surface state and insulating bulk state. The unique surface states in topological insulators offer potential applications in photonics and optoelectronics. Herein, topological insulators’ near‐infrared plasmonic behavior is utilized to demonstrate a tunable double‐mode absorber that shows an electromagnetically induced transparency (EIT)‐like effect. A composite structure is formed by sandwiching a photonic crystal heterostructure between topological insulator layers. The transfer matrix method is used to examine the optical response. The evolution of the modes with changes in layer thicknesses, grating period number, and propagating angle is also investigated. The study is further extended to multichannel optical absorption by making changes in the composite structure period, and the resultant absorption spectrum shows a multichannel EIT‐like effect.

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.

Two-dimensional photonic crystal heterostructure for light steering and TM-polarization maintaining applications

An attractive and realizable scheme of a compact two-dimensional (2D) photonic crystal (PhC) heterostructure is proposed for flexible light steering formed by integrating two PhC structures having diverse optical properties. The first PhC allows both TE- and TM-polarized light to propagate through it with minimum transmission loss (TL), whereas the second PhC structure is designed in such a way that TE-polarized light faces a photonic bandgap while self-collimated TM-polarized light travels without any diffraction. The study is conducted via a 2D finite element method. By the distinctive arrangement of both PhC structures, it is possible to obtain a TM-polarization maintaining device that offers a high polarization extinction ratio of ∼49 dB as well as a compact 180° bend for TE-polarized light with low TL. The proposed study is useful in designing PhC waveguides with sharp bends, which can be employed for multiple applications in photonic integrated circuits.

Silver loaded anodic aluminum oxide dual-bandgap heterostructure photonic crystals and their application for surface enhanced Raman scattering

Photonic crystals (PCs) are regarded as ideal materials for surface-enhanced Raman scattering (SERS) active substrates due to their unique optical behaviors of photonic band gap (PBG). In this work, for the sake of introduction of more PBGs in visible range, the Ag nanoparticle loaded anodic aluminum oxide dual-bandgap heterostructure photonic crystals (Ag@AAO DHPCs) SERS-active substrates are fabricated by using a specially designed periodic voltage–time waveform and vacuum thermal evaporation technology, which have a large-scale highly ordered nanopore structure, tunable high-quality multiple PBGs. As SERS substrates, the Ag@AAO DHPCs show excellent SERS-activity for Rhodamine B (RhB) with ultra-high sensitivity, uniformity, stability and reproducibility, the calculated enhancement factor (EF) can reach as high as 1.3 × 106, and the concentration limit can fall to an ultra-low value of 10−11 mol/L, suggesting that the trace detection of RhB could be realized with them. The outstanding SERS-activity of the Ag@AAO DHPCs would be mainly attributed to the introduction of multiple PBGs in surface plasma resonance (SPR) absorption range of silver nanoparticles and matching with the incident light, therefore, the stronger surface local electromagnetic field is obtained to enhance the SERS-activity through the synergistic effect of the Bragg reflection and the slow photon effect at the PBGs’ edges of AAO DHPCs. The Ag@AAO DHPC SERS-activity substrates are beneficial to the explorations of enhancement mechanism of surface Raman scattering signals and the developments of Raman imaging, biomolecular detection and chemical analysis.

Laser-Induced Patterned Photonic Crystal Heterostructure for Multimetal Ion Recognition

In this work, a new method of direct laser writing patterned photonic crystal heterostructure on a glass surface is proposed. A multi-heterostructure photonic crystal (MHPC) is predeposited on the glass surface and then the laser spot is focused on it and moves according to the set program, leading to the formation of patterned MHPC. Scanning electron microscopy (SEM) and finite element simulation show that the patterning is caused by the local thermal annealing of the polymer colloidal spheres through the thermal conduction effect of the substrate on the laser energy. The patterned area presents a function of the water confinement effect and can be used as a high-performance droplet analysis chip. By integrating the patterned MHPC array and seven fluorescent dyes, nine metal ions can be successfully recognized and discriminated. This approach is quite facile and fast for designing colloidal photonic crystals with controllable patterns. Moreover, it is of considerable significance for the practical application of photonic crystal heterostructure in the detection, sensing, anti-counterfeiting, and display fields.

Design of asymmetric transmission of photonic crystal heterostructure based on two-dimensional hexagonal boron nitride material

Two-dimensional (2D) hexagonal boron nitride (hBN) possesses many unique properties such as high mechanical strength and excellent chemical and thermal stability. The 2D hBN exhibits a wide bandgap in the UV region and optically-stable ultra-bright quantum emitters that make hBN a promising nanophotonic platform for quantum computing and information processing, especially in the visible wavelength range. Therefore, it is greatly important to build up different nanophotonic devices with different functionalities based on this material platform to achieve the integrated photonic chips. Among the devices, the integratable optical asymmetric transmission devices are important elements for functional quantum computing chips. Since hBN is a dielectric material, photonic crystal (PhC) structure is the most suitable in principle and allows on-chip integration with other photonic devices. In this study, we theoretically design an asymmetric transmission device based on 2D hBN PhC heterostructures in the visible wavelength range for the first time. Due to the relatively low refractive index of 2D hBN material (<i>n</i> < 2.4), we design a free-standing hBN PhC heterostructure to maximize the light trapping in the structure and minimize the propagation loss. The asymmetric transmission device is composed of two square-lattice 2D PhC structures, namely PhC 1 and PhC 2. We use the plane wave expansion method (PWM) to calculate the iso-frequency contours (EFCs) of the PhC structures to study the light propagation inside of the PhCs, which will propagate along the gradient of direction of the EFCs. We design the PhC structure in the way that the incident light beams from different angles can be self-collimated along the <i>Г-X</i> direction of the PhC 2 and coupled out. On the other hand, the backward incident light is blocked by the bandgaps of PhC 2. In this way, asymmetric optical transmission is achieved with high forward transmittance and contrast ratio. In addition, we further finely tune the structural parameters, including the lattice constant and column radius of the PhCs to optimize the performance by using the finite difference time domain (FDTD) method. The resulting 2D hBN PhC heterostructure achieves an asymmetric transmission in a wavelength range of 610–684 nm with a peak forward transmittance of 0.65 at a wavelength of 652 nm. Meanwhile, the backward transmittance is controlled to be 0.04. As a result, the contrast ratio can reach up to 0.95. The working bandwidth of the hBN PhC is 74 nm (<i>T</i><sub>F</sub> > 0.5). In addition, the designed asymmetric transmission device has a small size of 11 μm × 11 μm, thus it is suitable for on-chip integration. Our results open up possibilities for designing new nanophotonic devices based on 2D hBN material for quantum computing and information processing. The design principle can be generally used to design other photonic devices based on 2D hBN material.

Graphene-based low-threshold and tunable optical bistability in one-dimensional photonic crystal Fano resonance heterostructure at optical communication band.

In this paper, the one-dimensional photonic crystal Fano resonance heterostructure is used to achieve low-threshold and tunable graphene-based optical bistability of the transmitted and reflected light beam at optical communication band. The low-threshold of optical bistability (OB) originates from the local field enhancement owing to the Fano resonance excited by topological edge states mode and Fabry-Perot cavity mode. The study found that it is feasible to continuously adjust the hysteresis behavior and optical bistable thresholds by altering the Fermi energy of the left and right graphene respectively. Furthermore, the OB can also be controlled by changing the number of graphene layers or the angle of incident beam, which makes this structure a feasible object of experimental research at optical communication band in the future.

Manipulating the light-matter interaction in a topological photonic crystal heterostructure.

We theoretically and numerically investigate the ligh-matter interaction in a classic topological photonic crystal (PhC) heterostructure, which consists of two opposite-facing 4-period PhCs spaced by a dielectric layer. Due to the excitation of topological edge mode (TEM) at the interface of the two PhCs, the strong coupling between incident light and TEM produces a high quality resonance peak, which can be applied to many optical devices. As a refractive index sensor, it achieves a sensitivity of 254.5 nm/RIU and a high figure of merit (> 250), which is superior to many previously reported sensors. We further study the coupling between photons and excitons by replacing the pure dielectric layer with the J-aggregates doped layer. By tuning the thickness of the doped layer and the angle of incident light, the dispersive TEM can efficiently interact with the molecular excitons to form a hybrid mode with TEM-like or exciton-like components, showing interesting energy transfer characteristics and flexible modulation characteristics. This work may be helpful for a better understanding of light-matter interactions in a topological PhC heterostructure, and achieve potential applications in related optical devices.

Enhanced spectral splitting in a novel solar spectrum optical splitter based on one dimensional photonic crystal heterostructure

Controlling the distribution of solar spectrum in different bands would boost the energy harvesting efficiency and optimize the energy dispatchability. 1D photonic crystal with intrinsic optical band gap can be used to split the solar spectrum for hybrid photovoltaic/thermal solar applications. Here, we designed an efficient solar spectrum optical filter based on a cermet layer, Si/SiO2 1D photonic crystal, and top heterostructure layer. Compared with 1D photonic crystal structure, the 1D photonic crystal heterostructure with top YSZ layer can realize the reflectance of greater than 92% in PV band and the low average reflectance in two thermal bands by tuning the effective impedance of multilayer films. The enhanced reflectance in PV band results from the huge mismatching of impedance between free space and the heterostructure structure. The top dielectric layer can also be extended to other oxides.

Behaviors of the multiple interface states in photonic crystal heterostructure with frequency-dependent dielectric functions

In this paper, Dirac point method is used to study the interface state of one-dimensional photonic crystal heterojunction [Formula: see text] containing dispersive materials GaAs. We found that the energy levels of the interface states satisfy a simple sinusoidal function. We investigate the variation of the energy levels of the interface states with the incident angle, it is found that these interface states move toward high-frequency with the increase of the incident angle. At the same time, it is found that there is an extra localized band and it is further proved that the extra band corresponds to the defect band, and the energy levels of the defect band possess the same behavior with those of interface states.

Photonic crystal with 2-fold rotational symmetry for highly efficient asymmetric transmission

Here we demonstrate a photonic crystal heterostructure with 2-fold rotational symmetry elliptical shape lattice for highly efficient optical asymmetric transmission based on the self-collimation effect. The forward transmitted light can be collimated along the propagation direction and efficiently coupled out of the structure. Thus, the high forward transmittance up to 0.661 and 0.581 at the telecommunication wavelength of 1550 nm for TE and TM polarized modes can be achieved by this design. The 2-fold rotational symmetry allows further optimizing the structure by tuning the angle between the major axis of the ellipse and the Γ-X direction, and found that high forward transmittance can be achieved when the major axis of the ellipse is along the Γ-X direction.

Compact high-performance polarization beam splitter based on a silicon photonic crystal heterojunction

A novel polarization beam splitter based on a silicon photonic crystal (PC) heterostructure operating in the optical-telecommunications band is envisaged and is configured for planar integration with other PC or waveguide structures. The small 9μm×9.4μm footprint polarization beam splitter is investigated by the plane-wave expansion and finite-difference time-domain methods. Due to the combined effects of self-collimation and the photonic band gap, self-collimation transmission and 90° beam splitting for the two orthogonal polarizations are achieved. The transmissivity exceeds 60% (78%) for TE (TM) polarization covering a 115-nm bandwidth, and it is also observed that the polarization extinction ratios of the device are higher than 13 and 31 dB, respectively. Moreover, at the wavelength of 1550 nm, TE (TM) polarization has high transmissivity 94.9% (88%) with high polarization extinction ratio of 17 dB (41 dB). A compact and efficient polarization beam splitter is successfully designed for applications in optical communications.

Purcell enhancement of a deterministically coupled quantum dot in an SU-8 laser patterned photonic crystal heterostructure

Enhancement of single photon source emission through cavity quantum electrodynamics is key to the realization of applicable emitters in many quantum optics technologies. In this work, we present a flexible and convenient cavity fabrication process that writes a SU-8 microstrip onto a photonic crystal waveguide deterministically, in which InGaAs/GaAs quantum dots are present as emitters. The strip cavity is laser patterned at the location of a quantum dot with a chosen emission wavelength. Micro-photoluminescence studies are undertaken, which demonstrate an enhanced emission intensity by a factor of 2.1 with weak coupling to a single quantum dot, and time-resolved photoluminescence further shows a Purcell enhancement factor of 2.16. The fabrication process is, thus, verified as a reliable recipe to introduce deterministic cavity coupling to a chosen quantum dot.

Optical states in a 1D superlattice with multiple photonic crystal interfaces

Interface states in a 1D photonic crystal heterostructure with multiple interfaces are examined. The heterostructure is a periodic network consisting of two different photonic crystals. In addition, the two crystals themselves are periodic, with one being made of alternating binary layers and the other being a quaternary crystal with a tunable layer. The second crystal can thus be smoothly transformed from one binary crystal to another. All individual photonic crystals in the superstructure have symmetric unit cells, as well as identical periods and optical path lengths. Therefore, as the tunable layer in the quaternary crystal expands, other layers will shrink. It is found that the behavior of the localized modes in the band gaps is dependent on whether there is an even or odd number of interfaces in the heterostructure. With certain sequences of all dielectric photonic crystals, topological states are shown to split in two, whereas for other heterostructures they are shown to vanish. Additional resonant Tamm states appear depending on how many crystals are in the heterostructure. If the tunable layer is frequency dependent, the band gap can still support topological/resonant modes with some band gaps even supporting two separate groups.

Asymmetric transmission of light waves in a photonic crystal waveguide heterostructure with complete bandgaps.

Here, we theoretically present an on-chip nanophotonic asymmetric transmission device (ATD) based on the photonic crystal (PhC) waveguide structure with complete photonic bandgaps (CPBGs). The ATD comprises two-dimensional silica and germanium PhCs with CPBGs, within which line defects are introduced to create highly efficient waveguides to achieve high forward transmittance. In the meantime, the total internal reflection principle is applied to block the backward incidence, achieving asymmetric transmission. We optimize the design of the PhCs and the waveguide structure by scanning different structure parameters. The optimized ATD shows a high forward transmittance of 0.581 and contrast ratio of 0.989 at the wavelength of 1582 nm for TE mode. The results deepen the understanding and open up the new possibility in designing novel ATDs. The on-chip ATD will find broad applications in optical communications and quantum computing.