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Novel applications of photonic band gap materials: Low‐loss bends and high Q cavities
Abstract
In this paper we discuss a novel material which has nearly ideal properties at optical frequencies. It combines the low dissipation of a dielectric with the reflectivity of a metal. This material employs a two‐dimensional photonic band gap structure to achieve in‐plane confinement of light and uses index contrast to achieve vertical confinement. We discuss how this material can be used to create microcavities for the production of low threshold lasers and waveguides capable of low‐loss bends.
... [9][10][11] One-dimensional and twodimensional PCs with defects were reported theoretically and experimentally by Smith et al. 8 He reported the investigation of energy density of the defect modes. Line defect waveguide firstly investigated by Meade et al. in 1994 and sharp bending of light is theoretically investigated by Mekis et al. 12 13 The enhancement of reflectance band width was reported by Ojha and Srivastava by introducing defect in conventional photonic band gap structure. 14 In the similar fashion, we can create a localized defect mode in PBG by inserting or removing a layer from the one-dimensional PC which leads to selective transmission in the photonic band gap region and can be used as filters and splitters. ...
... [9][10][11] One-dimensional and twodimensional PCs with defects were reported theoretically and experimentally by Smith et al. 8 He reported the investigation of energy density of the defect modes. Line defect waveguide firstly investigated by Meade et al. in 1994 and sharp bending of light is theoretically investigated by Mekis et al. 12 13 The enhancement of reflectance band width was reported by Ojha and Srivastava by introducing defect in conventional photonic band gap structure. 14 In the similar fashion, we can create a localized defect mode in PBG by inserting or removing a layer from the one-dimensional PC which leads to selective transmission in the photonic band gap region and can be used as filters and splitters. ...
In the present paper, we have presented the transmission mode tunability in non-graded photonic crystal (NGPC) and linearly graded photonic crystal (LGPC) using lead sulphide (PbS) and titanium dioxide (TiO 2) in infrared region. A birefringent defect layer is created in NGPC and LGPC using potassium titany phosphate (KTP). With the help of transfer matrix method, the transmission properties of proposed structure is investigated for transverse electric (TE) and transverse magnetic (TM) polarization. NGPC and LGPC without defect layer is also investigated. We have found that a photonic band gap (PBG) arises in the infrared region. An additional defect layer of KTP is created in NGPC and LGPC structure. We have seen that a transmission mode appears in PBG region, arises due to the addition of defect layer. We have also seen the effect of linear gradation in thickness, angle of incidence, tilt angle, and thickness of defect layer, on PBG and transmission mode. We have observed that the transmission mode and PBG width can be tuned by changing the above parameters. The proposed structure may be used as channeled filter, optical switches, monochromator, and broadband optical reflector.
... PCs display photonic band gap (PBG) similar to their electronic counterparts in which no electromagnetic (EM) waves could be transmitted. EM wave transmission for frequencies lying in the PBG of a PC can be achieved by introducing, for instance, linear defects to form waveguides (WGs) in which EM waves are confined in and decay abruptly in the transverse direction [2][3][4][5]. Linear defect WGs have found widespread utility in applications such as wavelength division de/multiplexing [6,7] and unidirectional light transmission [8,9]. EM waves in two parallel WGs were shown to couple and decouple and thus enable EM power transfer in between if the dielectric region between the WGs is properly designed [10,11]. ...
Guiding and evanescent coupling properties of surface modes bound to the interfaces of two-dimensional photonic crystals in close proximity are numerically demonstrated. Interacting photonic crystals are composed of silicon pillars in air, where their outermost layers facing each other are annular. Surface modes are identified through supercell band structure computations, while their excitation by the electromagnetic waves through a perpendicular insertion waveguide is demonstrated using finite-difference time-domain simulations. Lifting the degeneracy between the surface modes as a consequence of bringing two identical photonic crystal surfaces to a sufficient distance results in evanescent coupling in a beating manner whose beat length linearly varies between 10 and 20 periods up to a frequency at which both surface modes travel with the same group velocity. The surface mode coupling phenomenon could be employed either to enhance sensitivity or to reduce device size in bio/chemical sensor applications since the effective travelling length of surface waves increases by about 3.5 times due to evanescent coupling.
... This type of waveguide is generally called W1 waveguide. The linear defect induced in the PhC can support linearly localized mode (guided mode) when its frequency lies into the photonic bandgap [58]. Such modes can act as waveguides, without relying on the total internal reflection that is regarded as the basic principle of guiding in the conventional optical waveguides. ...
In this thesis, we have studied two different devices: an electric field sensor and an electro-optical modulator made of LiNbO3, based on the electro-optical effect of this material. The proposed structures are based on photonic crystals in which a very confined optical mode with a high quality factor (Q) can be excited in LiNbO3.This leads to a strong enhancement of the electro-optical effect which results in a modification of the refractive index of LiNbO3. This index variation induces a spectral shift in the resonance of the optical mode. We used the FDTD method for the calculation of the optical response of the proposed structures. Through its character of spatial discretization (Yee schema), this numerical method allowed us to reveal the excitation of the symmetry protected modes (SPM) through a symmetry break related to the numerical scheme used. By exciting this type of SPM modes, we reach resonances with a very high Q factor up to 1 million. By combining the high Q-factors with the dielectric mode required for an electro-optical device, we have obtained a high local field factor of about 245. We have demonstrated, with the versatile structure we propose, an electric field detection sensitivity of 4pm.m/V and a temperature detection sensitivity of about 947nm/°C. In addition, we have proposed another geometry of an electro-optical modulator based on an enhaced transmission meta-material deposited on LiNbO3. Numerical simulations show that our electro-optical modulator has a value of the half-wave voltage Vπ of only 0.3V, which is more than 3 times lower than the state of the art. The fabrication of the proposed structure has been started and preliminary results are presented. The optical characterization of the structure allows us to validate the theoretical behavior of its optical response taking into account manufacturing imperfections. The optical bench used for the characterization of the fabricated structures was set up during this thesis.
... Since 1990s, such structures are considered easier for fabrication than photonic crystals with full three-dimensional band gaps, while retaining many of the latter's desirable properties. 188,189 Compared to 1D structures, photonic crystal slabs provide a broader variety of designs for unit cells, different types of their arrangement and, consequently, more degrees of freedom for flexible control over their optical properties. 160,190 Due to this fact, the variety of BICs in such structures is more extensive than for one-dimensional gratings or chains, including the possibility of BICs with high-order (≥ 2) ...
Bound states in the continuum provide a remarkable example of how a simple problem solved about a century ago in quantum mechanics can drive the research on a whole spectrum of resonant phenomena in wave physics. Due to their huge radiative lifetime, bound states in the continuum have found multiple applications in various areas of physics devoted to wave processes, including hydrodynamics, atomic physics, and acoustics. In this review paper, we present a comprehensive description of bound states in the continuum and related effects, focusing mainly on photonic dielectric structures. We review the history of this area, basic physical mechanisms in the formation of bound states in the continuum, and specific examples of structures supporting such states. We also discuss their possible applications in optics, photonics, and radiophysics.
... One-dimensional periodic waveguides were first conceived and studied in the middle of the 90s using the band structure analysis by [68][69][70]. Similar structures, considering an uniform strip waveguide and a periodic set of dielectric squares of ϵ = 12, see Fig. 2.16, and herein depicted. In the first case, the homogeneous structure presents a continuous translational symmetry in the z direction so that k is unrestricted in the band study, although here we impose an artificial restriction for the sake of comparison. ...
Silicon photonics is a key emerging technology in next-generation communication
networks and data centers interconnects, among others. Its success relies on the
ability of using CMOS-compatible platforms for the integration of optical circuits
into small devices for a large-scale production at low-cost. Within this field,
integrated interferometers play a crucial role in the development of several on-chip
photonic applications such as biological sensors, electro-optic modulators, all-optical
switches, programmable circuits or LiDAR systems, among others. However, it is well
known that optical interferometry usually requires very long interaction paths, which
hinders its integration in highly compact footprints. To mitigate some of these size
limitations, several approaches emerged including sophisticated materials or more
complex structures, which, in principle, reduced the design area but at the expense of
increasing fabrication process steps and cost.
This thesis aims at providing general solutions to the long-standing size problem
typical of optical integrated interferometers, in order to enable the densely integration
of silicon-based devices. To this end, we combine the benefits from both bimodal
waveguides and periodic structures, in terms of high-performance operation and
compactness to design single-channel interferometers in very reduced areas. More
specifically, we investigate the dispersive effects that arise from subwavelength
grating and photonic crystal structures for their implementation in different bimodal
interferometric configurations. Furthermore, we demonstrate various potential
applications such as sensors, modulators and switches in ultra-compact footprints of
a few square microns. In general, this thesis proposes a new concept of integrated
interferometer that addresses the size requirements of current photonics and open up
new avenues for future bimodal-operation-based devices.
... A lattice of dielectric material affects the motion of light through the material in much the same way that a lattice of atoms affect the motion of electrons through a material. Photonic crystals have a wide range of potential applications [62,79,52]. Two dimensional photonics have well-founded theoretical design principles [61], but principles to design photonic crystals 2 in three dimensions are based on general heuristics. ...
The synthesis of nanoparticles and colloids with anisotropic interactions and intricate shapes has led to the possibility of an assortment of complex self-assembled soft matter phases. In the first part of this work, I construct a theoretical minimal model to investigate the role of translational and rotational entropy in self-assembled solids of hard particles. Using computer simulations, I calculate the frequency of each normal mode of the solid and find the entropy contained in each translational and rotational wave. I show the entropy of a solid of hard hexagons is distributed nontrivially at many length scales among translational and rotational modes and construct maps in reciprocal space showing which fluctuations have more entropy. In the second part, I show that a solid of hard squares, like hard regular triangles, exhibit a strange high-density chiral symmetry-breaking transition. I show this transition is in the Ising universality class and that it is driven by a competition between rotational and translational entropy. In the third part of this work, I explore the origins of photonic band gaps in a wide variety of crystal structures formed of dielectric spheres. This problem has significant interest in the context of self-assembled soft matter as a route to design color-changing colloidal materials. I examine what characteristics of electromagnetic modes are responsible for opening a band gap in photonic materials. This problem is well-understood for photonics in two dimensions, but my coauthors and I show that the design heuristics developed for that problem do not hold in three dimensions.
... Existing optical filter technologies include: Fabry-Perot [1][2][3], Phasar [4][5][6], Bragg grating [7,8], and ring resonator filters [9][10][11]. However, it is important to approach photonic crystals, as they provide an opening for compact integration of optics [12,13]. ...
... In PhC devices, an artificial periodic structure with different refractive index that provides a band of frequency, which is not allowed the flow of light, called photonic bandgap (PBG). By introducing point defects or line defects into this PhC periodic structure, the transmission of light could be possible (Sigalas et al. 1993;Meade et al. 1994). These photonic structures are also used to design the devices to perform a lot of networking functions such as switching (Djavid et al. 2018), buffering (Long et al. 2010), computing (Vali-Nasab et al. 2019Askarian et al. 2019;Surendar et al. 2019), data encoding (Gholamnejad and Zavvari 2017; Olyaee 2019) regenerating, addressing (Salmanpour et al. 2015a, b) and demultiplexing (Venkatachalam et al. 2017). ...
Realization of logical gates in the optical domain is a crucial part of current research to take the advantages of light speed in future demands, an example optical computer motherboard. Here, this paper proposed a simple reconfigurable XOR/OR gate using Two-Dimensional (2D) Photonic crystal structure. The performance of the device is analyzed using 2D finite difference time domain method. The dimension of the proposed crystal structure is 12.5 µm × 12 µm. The field distribution has been measured and displayed to indicate the performance of the logic gates. The proposed structure is very compact with a low latency of 120 fs.
... In this paper, the emulation of evanescent (or weak) couplings via locally periodic structures is presented. In a similar fashion as the coupled-resonator optical waveguides are engineered with defects inside photonic crystals [11][12][13][14][15] , here coupled mechanical resonators are engineered in an otherwise periodic structure. The idea is to use the gaps of crystalline mechanical structures that will be taken as couplers. ...
Solid state physics deals with systems composed of atoms with strongly bound electrons. The tunneling probability of each electron is determined by interactions that typically extend to neighboring sites, as their corresponding wave amplitudes decay rapidly away from an isolated atomic core. This kind of description is essential in condensed-matter physics, and it rules the electronic transport properties of metals, insulators and many other solid-state systems. The corresponding phenomenology is well captured by tight-binding models, where the electronic band structure emerges from atomic orbitals of isolated atoms plus their coupling to neighboring sites in a crystal. In this work, a mechanical system that emulates dynamically a quantum tightly bound electron is built. This is done by connecting mechanical resonators via locally periodic aluminum bars acting as couplers. When the frequency of a particular resonator lies within the frequency gap of a coupler, the vibrational wave amplitude imitates a bound electron orbital. The localization of the wave at the resonator site and its exponential decay along the coupler are experimentally verified. The quantum dynamical tight-binding model and frequency measurements in mechanical structures show an excellent agreement. Some applications in atomic and condensed matter physics are suggested.
... In 1987, Yablonovitch and John conceptualized the photonic band gap and light localization [1,2]. In 1994, Meade et al. applied these concepts in planning devices [3]. In 1999, Painter et al. realized the first laser oscillation under a low-temperature pulsed condition [4]. ...
The GaInAsP semiconductor photonic crystal nanolaser operates at room temperature by photopumping and emits near-infrared light at a wavelength longer than 1.3 μm. Immersion of the nanolaser in a solution causes its laser characteristics to change. Observation of this phenomenon makes it possible to perform biosensing without a fluorescent label or a chromogenic substrate. The most common phenomenon between many photonic sensors is that the resonance wavelength reflects the refractive index of attached media; an index change of 2.5 × 10−4 in the surrounding liquid can be measured through an emission wavelength shift without stabilization. This effect is applicable to detecting environmental toxins and cell behaviors. The laser emission intensity also reflects the electric charge of surface ions. The intensity varies when an electrolyte or a negatively charged deoxyribonucleic acid (DNA), which is positively or negatively charged in water, is accumulated on the surface. This effect allows us to detect the antigen-antibody reaction of a biomarker protein from only the emission intensity without any kind of spectroscopy. In detecting a small amount of DNA or protein, a wavelength shift also appears from its concentration that is 2–3 orders of magnitude lower than those of the conventional chemical methods, such as the enzyme-linked immuno-solvent assay. It is unlikely that this wavelength behavior at such low concentrations is due to the refractive index of the biomolecules. It is observed that the electric charge of surface ions is induced by various means, including plasma exposure and an electrochemical circuit shifting the wavelength. This suggests that the superhigh sensitivity is also due to the effect of charged ions. Thus, we call this device an iontronic photonic sensor. This paper focuses on such a novel sensing scheme of nanolaser sensor, as an example of resonator-based photonic sensors, in addition to the conventional refractive index sensing.
... Fabriquer de telles structuresà l'échelle nanométrique permet de retrouver certaines des propriétés des cristaux de la nature [73,74]. Leurs multiples applications en optique, par exemple pour fabriquer des guides d'ondes [75] ou des cavités laser [76], en font un sujet d'étude très en vogueà l'heure actuelle. ...
Cette thèse porte sur la physique des ondes, dans le but de contrôler leur propagation. Nous cherchons à mettre en évidence des phénomènes communs à toutes les ondes grâce à un système expérimental modèle utilisant les ondes à la surface d’un liquide. Plus précisément, nous choisissons de travailler avec des ondes hydroélastiques en couvrant la surface du liquide avec un film élastique. Les déformations élastiques de cette membrane sont couplées aux mouvements du fluide, de sorte qu’en modifiant les propriétés de la membrane nous pouvons agir sur la propagation des ondes. Ainsi, en changeant localement l’épaisseur du film élastique nous montrons qu’il est possible de dévier, réfléchir ou encore focaliser les ondes. Ensuite, en structurant périodiquement la membrane nous mettons en évidence des effets liés à la périodicité et/ ou à la nature des objets formant le réseau régulier. Nous utilisons des perforations circulaires dont nous varions le diamètre, l’espacement et l’arrangement dans l’espace, ce qui nous permet de contrôler très finement le comportement des ondes dans le cristal artificiel ainsi formé. Nous mettons notamment en évidence l’existence de bandes interdites de propagation. Enfin, nous re-visitons l’instabilité de Faraday, connue en hydrodynamique, en vibrant verticalement un bain liquide recouvert d’une membrane élastique, et nous montrons que cette instabilité existe également pour les ondes hydroélastiques.
... The maximum group velocity at the center of CROW transmission band can be calculated using the formula provided in [14] Mechanisms proposed in the past for optical waveguiding include: total internal reflection, Bragg waveguiding and waveguiding based on coupling of optical resonators or coupled resonator optical waveguide (CROW) [15] [16] . Some of the possible ways realizations of CROW based waveguides are: evanescent-field coupling between the high-Q modes of individual microdisk cavities in MRR CROW and evanescent-field coupling between the individual resonators (point defect cavities) in [17] [18] embedded in a two-dimensional periodic structure such as 2D photonic crystal [19] [20] . The coupling in case of CROWs is due to the evanescent Bloch waves. ...
In this paper, a new design of optical delay line based on coupled ring resonators in photonic crystals is proposed and analyzed by means of numerical simulation in CST Microwave Studio. The performance of the proposed photonic crystal ring resonator (PhCRR) based coupled resonant optical waveguide (CROW) is compared to: point-defect cavity based coupled cavity waveguides (CCW) in photonic crystal. microring resonator (MRR) based CROW. The suggested design addresses compactness issues of the MRR CROW while offering normalized delay values better than CCW and comparable to MRR CROW. The PhCRR CROW also enhances design flexibility as the PhCRRs support multiple modes and thereby supporting multi-channel transfer/delay application on a single device.
... PhC waveguides, formed by introducing a linear defect into a perfect PhC structure, is one of the essential ingredients in PICs. 2D PhC waveguides were proposed [6] and demonstrated experimentally [7,8] . Based on this structure, many components such as Mach-Zehnder devices [9] , filters [10,11] , modulators [12] , detectors [13] , sensors [14] , and directional couplers [15] can be created. ...
In this Letter, the effects of material/structure parameters of photonic crystal (PhC) parallel waveguides on the coupling length are investigated. The results show that, increasing the effective relative permittivity of the PhC leads to a downward shift of the photonic bandgap and a variation of the coupling length. A compact PhC 1.31/1.55 μm wavelength division multiplexer (WDM)/demultiplexer with simple structure is proposed, where the output power ratios are more than 24 dB. This WDM can multiplex/demultiplex other light waves efficiently.
... The existence of PBGs will lead to many interesting phenomena, e.g., modification of spontaneous emission [13][14][15] and photon localization [16][17][18]. Thus numerous applications of photonic crystal have been proposed in improving the performance of optoelectronic and microwave devices such as high-efficiency semiconductor lasers, light emitting diodes, wave guides, optical filters, high-Q resonators, antennas, frequency-selective surface, optical limiters and amplifiers [19][20][21]. These applications would be significantly enhanced if the band structure of the photonic crystal could be tuned. ...
With the optical kerr effect, the conventional photonic crystal can be turned into the function photonic crystal under the action of pump light. In the paper, we have designed the ultra-strong light source and laser with one-dimensional function photonic crystal. When the incident light is the ordinary light, the output is ultra-strong light source, and when the incident light is the low power laser, the output is ultra-strong laser, the maximum magnification can be reached $10^{80}$ and even more. Otherwise, we analyzed the effect of period number, medium refractive index and thickness, incident angle, the pump light irradiation way and pump light intensity on the magnification, these results shall help to optimal design ultra-strong light source and laser.
... It has been widely studied since the concept was proposed by Yablonovitch [1] and John [2]. The most striking feature of PCs is that they can cause localization of photons, which is one of the most significant properties of optical cavities and waveguides [3,4]. Based on this property, many optical devices can be built, such as mainstream optical fibers [5], couplers/filters [6,7] and lasers [8]. ...
Light trapping at the Dirac point in 2D plasma photonic crystal has been obtained. The new localized mode, Dirac mode, is attributable to neither photonic bandgap nor total internal reflection. It exhibits a unique algebraic profile and possesses a high-Q factor resonator of about 10⁵. The Dirac point could be modulated by tuning the filling factor, plasma frequency and plasma cyclotron frequency, respectively. When a magnetic field parallel to the wave vector is applied, Dirac modes for right circularly polarized and left circularly polarized waves could be obtained at different frequencies, and the Q factor could be tuned. This property will add more controllability and flexibility to the design and modulation of novel photonic devices. It is also valuable for the possibilities of Dirac modes in photonic crystal containing other kinds of metamaterials.
... The nanophotonic structures offer exceptional potential for the development of new architectures of photovoltaic solar cells in thin layers and high efficiency. Among the promising applications of PCs, we mentioned selective filter based on 2D CPs [3]. ...
Two dimensional finite differences temporal domain (2D-FDTD) numerical simulations are performed in cartesian coordinate system to determine the dispersion diagrams of transverse electric (TE) of a two-dimension photonic crystal (PC) with triangular lattice. The aim of this work is to design a filter with maximum spectral response close to the frequency 1.55 μm. To achieve this frequency, selective filters PC are formed by combination of three waveguides W<sub>1</sub><sup>K </sup>A wherein the air holes have of different normalized radii respectively r<sub>1</sub>/a =0.44, r<sub>2</sub>/a =0.288 and r<sub>3</sub>/a = 0.3292 ( a: is the periodicity of the lattice with value 0.48 μm). Best response is obtained when we insert three small cylindrical cavities (with normalized radius of 0.17) between the two half-planes of photonic crystal strong lateral confinement.
... Naturally, the size of the mode area (or length) depends on the wavelength under consideration, on the waveguide materials and, above all, on the confinement mechanism, which can be based on total internal reflection (TIR), on interference, or on more exotic phenomena, such as the coupling with free charges in metal, as it happens for surface plasmon polaritons (SPPs)[6,7]. Even considering only the case of planar dielectric structures, one finds a quite surprising variety of confined modes, from D'yakonov waves, which exist at the interface between anisotropic and isotropic media[8,9], to guided modes in Bragg waveguides[10,11]. Light confinement in dielectric multilayers has been extensively investigated in fundamental studies of the light-matter interaction and for the development of photonic technologies[12][13][14]. ...
We present a systematic comparison between guided modes supported by slab waveguides and Bloch Surface Waves (BSWs) propagating at the surface of truncated periodic multilayers. We show that, contrary to common belief, the best surface field enhancement achievable for guided modes in a slab waveguide is comparable to that observed for BSWs. At the same time, we demonstrate that, if one is interested in maximizing the electromagnetic energy density at a generic point of a dielectric planar structure, BSWs are often preferable to modes in which light is confined uniquely by total internal reflection. Since these results are wavelength independent and have been obtained by considering a very wide range of refractive indices of the structure constituent materials, we believe they can prove helpful in the design of future structures for the control and the enhancement of the light-matter interaction.
... 18 The quality factor Q is used to denote the losses present in any resonant cavity, for high Qfactor cavities, only a small amount of energy leaks out of the cavity per optical cycle. 19,20 The Q-factor of the defect region can be controlled by the size of the air holes and the refractive index contrast of the structure and then analyzed by using Fourier transform technique. Increasing or decreasing the sizes of the air hole will change the dielectric material in the structure and will push the modes toward the dielectric bands. ...
In this study, the structure being investigated consists of periodic layers of In0.2Ga0.8As that have a defect region in air holes and GaAs. Using the finite-difference time-domain method (FDTD), we show that the influences of hole radius on the Q-factor, frequency of defect region and the defect band structure. Also, we investigate property of the defect region on the bandgap structures.
The absence of a suitable standard device platform for terahertz waves is currently a major roadblock that is inhibiting the widespread adoption and exploitation of terahertz technology. As a consequence, terahertz-range devices and systems are generally an ad hoc combination of several different heterogeneous technologies and fields of study, which serves perfectly well for a once-off experimental demonstration or proof-of-concept, but is not readily adapted to real-world use case scenarios. In contrast, establishing a common platform would allow us to consolidate our design efforts, define a well-defined scope of specialization for “terahertz engineering,” and to finally move beyond the disconnected efforts that have characterized the past decades. This tutorial will present arguments that nominate substrateless all-silicon microstructures as the most promising candidate due to the low loss of high-resistivity float-zone intrinsic silicon, the compactness of high-contrast dielectric waveguides, the designability of lattice structures, such as effective medium and photonic crystal, physical rigidity, ease and low cost of manufacture using deep-reactive ion etching, and the versatility of the many diverse functional devices and systems that may be integrated. We will present an overview of the historical development of the various constituents of this technology, compare and contrast different approaches in detail, and briefly describe relevant aspects of electromagnetic theory, which we hope will be of assistance.
Photonic crystals and metamaterials are two overarching paradigms for manipulating light. By combining these approaches, hypercrystals can be created, which are hyperbolic dispersion metamaterials that undergo periodic modulation and mix photonic-crystal-like aspects with hyperbolic dispersion physics. Despite several attempts, there has been limited experimental realization of hypercrystals due to technical and design constraints. In this work, hypercrystals with nanoscale lattice constants ranging from 25 to 160 nm were created. The Bloch modes of these crystals were then measured directly using scattering near-field microscopy. The dispersion of the Bloch modes was extracted from the frequency dependence of the Bloch modes, revealing a clear switch from positive to negative group velocity. Furthermore, spectral features specific to hypercrystals were observed in the form of sharp density of states peaks, which are a result of intermodal coupling and should not appear in ordinary polaritonic crystals with an equivalent geometry. These findings are in agreement with theoretical predictions that even simple lattices can exhibit a rich hypercrystal bandstructure. This work is of both fundamental and practical interest, providing insight into nanoscale light-matter interactions and the potential to manipulate the optical density of states.
In this paper, a Graphene based field emission electron gun is designed for W-band PhC based high power source. The electron gun is designed in CST and analyzed using particle tracking studio suite. At 3kV anode voltage, achieved beam current >100 mA. The beam transported (100%) ≥10 mm through the beam tunnel of 1.8 mm without applying any magnetic field.
We describe a unified quantum approach for analyzing the scattering coefficients of superconducting microwave resonators with a variety of geometries, and demonstrate its consistency with the classical approach [Q.-M. Chen et al., Phys. Rev. B 106, 214505 (2022)]. We also generalize the result to a chain of resonators with time delays, and reveal several transport properties similar to a photonic crystal and can be used to design high-quality resonators. These results form a firm theoretical ground for analyzing the scattering coefficients of an arbitrary resonator network. They set a step forward to designing and characterizing superconducting microwave resonators in a complex superconducting quantum circuit.
Photonic crystals and metamaterials are two overarching paradigms for manipulating light. Combining the two approaches leads to hypercrystals: hyperbolic dispersion metamaterials that undergo periodic modulation and mix photonic-crystal-like aspects with hyperbolic dispersion physics. So far, there has been limited experimental realization of hypercrystals due to various technical and design constraints. Here, we create nanoscale hypercrystals with lattice constants ranging from 25 nm to 160 nm and measure their collective Bloch modes and dispersion with scattering nearfield microscopy. We demonstrate for the first time dispersion features such as negative group velocity, indicative of bandfolding, and signatures of sharp density of states peaks, expected for hypercrystals (and not for ordinary polaritonic crystals). These density peaks connect our findings to the theoretical prediction of an extremely rich hypercrystal bandstructure emerging even in geometrically simple lattices. These features make hypercrystals both fundamentally interesting, as well as of potential use to engineering nanoscale light-matter interactions.
Optical spatial solitons in photorefractive media have been very attractive for research because of their relative ease of formation at low laser powers. Photonic lattices embedded in photorefractive crystals can mimic structures and properties of photonic crystals.In this chapter, we have discussed the stability and existence of gap solitons in different types of photorefractive optical lattices, i.e. optical lattices in non-centrosymmetricphotorefractives, centrosymmetricphotorefractives and pyroelectricphotorefractives. A theoretical foundation using the Helmholtz equation has been laid which serves as a general framework for photorefractive crystals having different nonlinearities and configurations. The gap soliton profiles in the first and second finite band gap for each of the three configurations of the photorefractive crystal have been studied. The first finite band gap supports entirely positive single-humped solitons and the second finite band gap supports asymmetric and double-humped or multi-humped solitons. The stability of gap solitons is analysed in all three configurations by linear stability analysis.
Le contrôle des ondes est d’un intérêt fondamental pour de nombreuses applications. On peut forcer une onde à se propager suivant un chemin désiré en concevant le milieu de propagation permettant le concept de réfraction négative. Les ondes de Lamb sont adéquates pour l’application de ce concept. Elles présentent l’existence de points à vitesse de groupe nul (ZGV) au-dessus desquels cohabitent des modes à vitesse de phase positive et négative. Le changement abrupt de l’épaisseur d’une plaque permet la conversion d’un mode à vitesse de phase positive en un mode à vitesse de phase négative, donnant lieu aux phénomènes de réfraction et réflexion négatives.Ce manuscrit présente un modèle semi-analytique développé pour prédire les coefficients de réflexion et de transmission des modes de Lamb sur une marche d’épaisseur. Il est utilisé pour évaluer la réfraction négative en fonction des caractéristiques de la plaque et de l’onde incidente. Ensuite sont présentées les études numériques et expérimentales de dispositifs utilisant la réfraction négative afin d’annuler la diffusion de l’onde par un objet ou encore de piéger une onde par réfractions négatives successives. Une étude numérique visant à réaliser une lentille permettant de vaincre la limite de diffraction pour les ondes de Lamb est ensuite présentée. Enfin un nouveau dispositif expérimental est mis en place pour étudier les ondes de Lamb avec une génération monochromatique et sélective spatialement permettant alors d’étudier le comportement des modes de Lamb au voisinage du mode ZGV, là où coïncident modes prograde et rétrograde.
This paper presents a planar silicon integrated subharmonic mixer on top of a photonic-crystal platform. The local oscillator (LO) power is injected through a 2D photonic-crystal (PC) slab to a resonant cavity that effectively couples the signal to a planar bow-tie antenna. The same antenna, which is printed on the top of the PC cavity, contains an antiparallel Schottky diode pair which performs the down-conversion. The proposed design is a single layer, low cost, low profile device. Moreover, the described fabrication process is compatible with active components integration. The performance of the design has been experimentally demonstrated showing good agreement with the simulation and is comparable with the state-of-the-art of planar mixers. The work presented here is based on concepts and technologies from electronics and photonics domains and may be a good starting point for the creation of new devices, allowing the integration and upgrading of existing techniques from both worlds.
Using binary phase shift keying is one of the popular methods used for designing optical logic gates. In this paper, we used optical waveguides with different lengths for designing an all-optical XOR gate. The proposed structure works based on constructive and destructive interference of optical beams. The time delay of the proposed structure is 0.5 ps.
Optical waveguides are structures which guide waves (flow of optical energy) in the optical spectrum. These can be broadly categorized into planar and non-planar waveguides; non-planar waveguides can be further classified according to geometry, mode structure, refractive index distribution, and material.
Optical reversible gates are required in realizing all optical digital data processing. In reversible gates, there is a one by one mapping between the input and output ports which helps us to recover the inputs from the outputs. In this paper we aim to design and propose all optical reversible XOR and XNOR gates based on electromagnetic scattering phenomenon in nonlinear photonic crystal structures. For realizing the proposed structures a special resonator was proposed which consists of two cross connected waveguides along with some linear and nonlinear defect rods. The proposed structure will be simulated using finite difference time domain method. The simulation results show that the maximum time delay for the proposed structures is about 10 ps. The truth tables for the both structures prove that there is one by one mapping between the inputs and outputs of the proposed structures.
A photonic crystal slab is a periodic arranged dielectric nanostructure which can be used in many applications, such as a label-free optical biosensor. This work demonstrates a novel nanofabrication process using helium ion lithography (HIL) for the rapid prototyping of master molds, which can be repeatedly used for fabricating photonic crystal slabs by nanoimprint lithography. To prove the concept, photonic crystal slabs with nano-grating and nano-hole patterns have been fabricated and the results show that the photonic crystal slabs fabricated by the HIL in conjunction with the nanoimprint lithography demonstrate photonic bandgaps. The functional tests demonstrate that the fabricated nano structures can be utilized as refractometric sensors to detect changes of the refractive index caused by adsorption of biochemicals. This fabrication approach offers a new route for mass-production of high-quality photonic crystal biosensors with a variety of nano-patterns.
PurposeNowadays, noise pollution is considered a major environmental problem which has affected the health and comfort of millions of people around the world. Solving the mentioned problems need to design a new generation of acoustic barriers. Acoustics experts believe that stopping and absorbing the low-frequency sound is difficult. The aims of this study were to remove the harmful frequency in industries and cities. This study concentrates on the reduction of the noise level and increasing the mass law and resonance at low frequencies.Methods
Sound measurement and frequency analysis did to fix the harmful frequency in the Shiraz city and in the Shiraz Gas Power Plant. COMSOL 5.3a software used for simulation. Suitable material chose for the manufacture of the sound barrier through the Cambridge engineering selection software 2013. The meta-material sound barrier made and tested in the acoustic room and in the free space. Results analyzed and optimized by Design of Experiment (DOE) and Response Surface Methodology (RSM) software. Mini Tab. 18.1 software used for Statistical Calculations. New sound barriers manufactured with adding new strategies to previous studies to improve the performance of meta-materials like beautification inspired from the flowers of nature and increasing of resonance in internal pipes.ResultsThree mechanisms used in this scatterer model which included, resonance phenomenon, Band Gap (BG) without absorption mechanism and inner-fractal-like structure. Our technique showed an advantage to reduce at frequencies below 100 Hz without adsorbent usage. The results showed that reduced noise exposures about 17.8 dB at frequency 50 Hz, about 9.1 dB within the range of 250 Hz according to EN 1793–2 standard (Lab Test for Airborne Sound Insulation). The sound barrier reported in this work provides the best and updated solution in the field of noise control.ConclusionsA novel generation of sound barriers introduced. We called this structure Interior Quasi-Fractal Sonic Crystal Acoustic Barrier (IQFSCAB). In this study, several different gaps used to remove various frequencies. It could be concluded that the outcomes of the meta-material models based on the Sonic Crystal (SC) could be used for the purpose of noise control system and could be helpful for decision-makers on the noise control legislations.
Interaction of waves with noise barriers and wave propagation inside periodic media is a hot topic in many branches of science and technology. The acoustic metamaterial can create green environments by reducing the low frequencies of industrial noise or traffic jam. New barrier have added a number of new strategies to previous studies in order to improve the performance of meta-materials. Our technique shows a clear advantage over to absorb at frequencies below 100 Hz without adsorbent usage. Innovative use of several different gaps and diameters for to remove various frequencies was done in this study. We called this structure IQFSACB due to fractal like interior pipes as those seen in some of the flowers in nature.
An original design of compact and efficient 16-channels demultiplexer integrated in a photonic crystals PhCs slab for dense wavelength demultiplexing near infrared application operating around two wavelengths 1.31 μm and 1.55 μm with an occupied area of 752.25 μm² is proposed in this paper. The demultiplexer is based on a square lattice two-dimensional PhCs quasi square ring resonator (QSRR) for wavelength division multiplexing applications; it consists of two blocks where each one of theme is dedicated to function around one band of wavelengths 1.31 μm or 1.55 μm separated by a wideband demultiplexer. The demultiplexer is of good-quality factor Q that equals 517.6 for a spectral width of 3 nm and 622 for a spectral width 2.5 nm, low crosstalk values between -9 dB and-41 dB were observed in the same block. Furthermore, an extreme low crosstalk values between -27 dB and-288 dB were noted between two different blocks (1.31 μm and 1.55 μm), with high transmission efficiency of about 90%.
In this paper, we have proposed the spinor wave equation of free and non-free photon, and given the quantum transfer matrix, dispersion relation, quantum transmissivity and quantum reflectivity of one-dimensional photonic crystals with the quantum theory of photon. On that basis, we have studied the effect of different incident angle, refractive index and thickness of medium on quantum and classical dispersion relation, transmissivity and reflectivity. We have found the results of quantum and classical are identical, which indicate the quantum theory approach for photonic crystals is reasonable and true, it will be studied the quantum edge state, quantum Zak phase and Chern number of the quantum topological property for photonic crystals.
A silicon photonic crystal (PhC)-based structure is proposed to efficiently couple power from two different wavelengths, targeted to the application of an integrable Raman amplifier. The coupler uses two asymmetrical PhC waveguides as input ports which are joined together and the coupled power is directed to a slotted photonic crystal waveguide-based output port. Coupling efficiency and the other performance metrics are evaluated using a three-dimensional full-vector finite-difference time domain simulation method, which is tested for accuracy using some existing experimental structures and corresponding results. The heuristic approach has been adopted to optimize the design for maximizing the coupling efficiency. Dependence of the coupling performance on different design parameters has also been investigated. Simulations exhibit ∼3-dB coupling losses for both arms in a small footprint as small as ∼54 μm². © 2018 Society of Photo-Optical Instrumentation Engineers (SPIE).
Photonic crystal nanocavities that simultaneously possess small modal volumes and high quality (Q) factors have opened up novel research areas in photonics during this decade. Here, we present an important key for the increase of Q factors to ranges beyond ten million. A systematic investigation on photon lifetimes of air-bridge-type heterostructure nanocavities fabricated from silicon on insulator (SOI) substrates indicated the importance of cleaning the bottom side (buried oxide side) of the nanaocavites. Repeated thermal oxidation and an oxide removal process applied after the removal of the buried oxide layer underneath the nanocavities realized an experimental Q factor greater than eleven million, which is the highest experimental Q ever recorded. The results provide important information not only for Si PC nanocavities but also for general Si nanophotonic devices and photonic electronic convergence systems.
It has been demonstrated that photonic band gap can be realized in quasi-periodic photonic crystal. We design a two dimensional octagonal photonic quasicrystal composed of alumina cylinders. The photonic band gaps are theoretically examined by the Transfer Matrix Method (TMM) and Finite-Difference Time-Domain (FDTD) for transverse magnetic (TM) wave. A Y-shaped light splitter is designed and simulated by FDTD method. The transmission spectra indicate the quasi-periodic photonic crystal has a band gap at the frequency range from ω = 0.27– 0.31, and the designed Y-shaped beam splitter has a clear guiding effect in the first gap (ω = 0.29) the designed Y-sharped beam splitter may have potentional application in integrated plasmonic circuits.
In this work we successfully fabricated and measured PhCs patterned on a LiNbO3 APE waveguide. SIMS data indicate that after 5 hours exchange time a PE layer of 3µm can be obtained. The depth of holes was 2µm by applying a large milling current. We presented experimental characterization of the PhC waveguide and a well-defined PBG was observed from the transmission spectra. An extinction ratio was estimated to be approximately 15dB. Optical transmission results indicate that deep air holes can lead to a sharp band edge. This PhC waveguide is a good candidate for further development of an ultra-compact, low-voltage LiNbO3 modulator.
In this work we successfully fabricated and measured PhCs patterned on a LiNbO3 APE waveguide. SIMS data indicate that after 5 hours exchange time a PE layer of 3μm can be obtained. The depth of holes was 2μm by applying a large milling current. We presented experimental characterization of the PhC waveguide and a well-defined PBG was observed from the transmission spectra. An extinction ratio was estimated to be approximately 15dB. Optical transmission results indicate that deep air holes can lead to a sharp band edge. This PhC waveguide is a good candidate for further development of an ultra-compact, low-voltage LiNbO3 modulator.
Guided modes in slab-like structures consisting of dielectric material surrounded by 2D photonic-band-gap material are studied by the plane-wave expansion method on a supercell. We outline (i) the role of boundary arrangement for contradirectional coupling; (ii) the existence of a guide with very narrow mid-gap mode compared to the ID case.
Guided modes in slab-like structures consisting of dielectric material surrounded by 2D photonic band gap material drilled in the same dielectric are studied by the supercell method. Focusing on E-polarized modes (\( \vec{H} \) transverse to the rods), we outline (i) the existence of a guide with mid-gap mode much narrower than the classical quarter-wave layer of the 1D case, (ii) the role of the relative “phases” of the boundary corrugations for contradirectional coupling, and (iii) the symmetries of modes at k = 0 and how it appears in the succession of modes.
An effective refractive index sensor built with square lattice photonic crystal is proposed, which can be applicable to photonic integrated circuits. Two photonic crystal waveguides rather than conventional ridge waveguides are used as entrance/exit waveguides to the micro-cavity. Three layers of photonic lattice are set between the photonic crystal waveguides and the micro-cavity to achieve both a high transmission and a high sensitivity. The plane wave method is utilized to calculate the disperse curves and the finite difference time domain scheme is employed to simulate the light propagation. At the resonant wavelength of about 1500 nm, the resonant wavelength shifts up by 0.7 nm for each increment of Delta n=0.001. A transmission of more than 0.75 is observed. Although the position disorder of the photonic crystal doesn't affect the sensitivity of the sensor, the transmission reduces rapidly as the disorder increases.
We describe the fabrication process of a two-dimensional silicon-based photonic crystal (PC) slab with partial air-bridge, which has a photonic band gap in the near-IR range. The process involves the formation of the air-bridge silicon slab by wet etching and the fabrication of periodic air holes by a focused ion beam. We successfully obtained such a sample and measured its transmission in a wide spectrum. It is found that the observed spectrum is consistent with the theoretical values calculated by the plane wave expansion method. The TM0-like modes reduce the size of the band gap, and the partial air bridge is beneficial to the fabrication of large PC slabs. Meanwhile, it is possible to draw light out from the supporting material of the air bridge.
It has been over 20 years since the concept of photonic crystal was proposed. Photonic crystal is now an important part of nano/micro-optics and quantum optics, and is also applied in many fields, such as information optics etc. The paper is focused on the progress in the fabrication of photonic crystals, especially the fabrication of two-dimensional and three-dimensional photonics. Meanwhile, the application of the photonic crystal is also reviewed. Then some perspectives are proposed.
Compared with the photonic crystal(PC) structures composed of Si circular, the PC structures composed of triangular lattice of air holes in a dielectric slab are more easily fabricated and integrated. The tunability of directional band gap in a two-dimensional photonic crystal of air holes in a semiconductor matrix is demonstrated numerically, using the plane wave expansion calculation. Numerical simulations show that the photonic crystal band gaps are modulated by nematic liquid crystals infiltrated in the air holes. Then the band gap can be controlled easily under the influence of the external electric field. So the results can serve as a field-sensitive polarizer. These results are in agreement with that of Liu. However, the tunable field-sensitive polarizer based on the phenylacetylene liquid crystals instead of 5CB liquid crystals has the wider frequency range. Moreover, the transmission spectrum of the photonic crystal infiltrated by liquid crystal is analyzed, using finite difference time domain(FDTD) method. Numerical simulations show that the shift of the spectrum modulated by liquid crystal can be used to design a novel switch.
It is important to understand properties of different materials and the impact they have on devices used in communication networks. This paper is an overview of optical non-linearities in Silicon and Gallium Nitride and how these nonlinearities can be used in the realization of optical ultra-fast devices targeting the next generation integrated optics. Research results related to optical lasing, optical switching, data modulation, optical signal amplification and photo-detection using Gallium Nitride devices based on waveguides are examined. Attention is also paid to hybrid and monolithic integration approaches towards the development of advanced photonic chips.
A systematic theoretical investigation is undertaken in order to identify a two‐dimensional periodic dielectric structure that has a complete in‐plane photonic band gap for both polarizations. Of the various structures studied, only a triangular lattice of air columns is found to have the desired band‐gap properties. Microwave transmission experiments are performed to test the theoretical predictions.
A review is presented of recent progress in low-loss III-V
semiconductor integrated optics for the 1-1.6 μm wavelength range,
including propagation, bending, coupling, and modulator losses.
Tradeoffs between loss and other performance issues are discussed in
detail. The authors show that significant advances have resulted in a
research shift from work on the general issues of improved material
transparency and straight guide propagation loss to more
application-specific areas. In particular, size-loss tradeoffs in bend
and modulator structures remain key issues for widespread use of III-V
integrated optics