Design optimization of one-dimensional photonic crystal waveguide

Compact, wide bandwidth, multi-channel power dividers based on one-dimensional photonic crystal waveguides

We propose a compactly integrated transverse-magnetic (TM)-pass polarizer based on rectangular-shape onedimensional photonic-crystal silicon waveguide with an extremely high polarization extinction ratio of >30 dB and low insertion loss (~1 dB) over a broad wavelength range of 210 nm from 1,460 nm to 1,670 nm. The polarizer has been numerically simulated using three-dimensional finite-difference time-domain (3D FDTD) method. The optimum length of the proposed TM-pass polarizer is about 4 μm. At the 1,550 nm wavelength, the simulated polarization extinction ratio of the polarizer is 36 dB, and its corresponding insertion loss is about 1 dB.

A single bandgap overlapping scheme is often used to enlarge the photonic bandgap (PBG) range in cascaded or hetero one-dimensional photonic crystal (1D PC) structures. In this paper, we design an optimized one-dimensional plasma photonic crystal (1D PPC) heterostructure based on the idea of combining complementary multiple PBGs to enlarge the PBG range. The flexibility of the PBG of a 1D PPC, caused by the frequency-dependent dispersive properties of plasma, is helpful for generating and combining multiple bandgaps. The obtained omni-directional photonic bandgap (ODPBG) width for the 1D PPC heterostructure is dramatically enhanced compared with that of a single 1D PPC alone and is much larger than that of 1D PC heterostructures described in the previous works. Further study shows that the PPC heterostructures are more suitable than other heterostructures (such as a 1D PC heterostructure or heterostructures composed of a 1D PPC and 1D PC) for combining complementary PBGs. The ODPBG ranges for 1D PPC heterostructures can be further extended by adjusting the parameters of the plasma to allow more complementary PBGs to combine with each other.

Realization of white LED using plasmonic-based photonic structure through reflection, absorption and transmission analysis

The analysis of band structure of one-dimensional (1-D) photonic crystal containing dispersive and non-linear dispersive materials has been presented. The band spectra for the different combination of photonic crystals have been calculated by the well-known plane wave expansion method. The effect of the dispersive and non-linear materials on the band structures has been determined. The third-order nonlinearity has been considered in the non-linear material, and Lorentz–Drude model has been taken for dispersive material. The band gaps of considered photonic crystal are affected by the nonlinearity in the presence of dispersive material like gold. We have observed that the normalized frequency difference between photonic bands decreases on increasing intensity of input beam. This work may be useful in optical switching devices.

In the present research work, we have theoretically analyzed the photonic band-gap properties of one-dimensional photonic structures composed of polycarbonate and non-glass materials. These photonic structures, PC1, PC2, PC3 and PC4, are composed of alternating layers of polycarbonate/Al2O3, polycarbonate/MgF2, polycarbonate/BaF2 and polycarbonate/TiO2 materials, respectively. The period of each photonic structure is made up of a thin non-glass material layer sandwiched between two identical polycarbonate layers. The transfer matrix method has been used to investigate the transmission properties of PC1 to PC4. The comparison between the transmission spectra of PC1 to PC4 shows that the polycarbonate and TiO2-based photonic structure (PC4) possess three PBGs of zero transmission located at far-ultraviolet, visible and near-infrared regions of the electromagnetic spectrum at normal and oblique incidence (θ0 = 55°), both corresponding to TE wave only. The index of refraction of all five materials used in this study was obtained by applying the Sellmeier-type dispersion relationship to ensure accuracy in the results. The purpose of selecting polycarbonate along with Al2O3, TiO2, MgF2 or BaF2 as constituent materials of these photonic structures is due to the heat resistance properties of polycarbonate and the unique optical properties of oxide and fluoride materials with wide transparency from the ultraviolet to the near-infrared regions of the electromagnetic spectrum. The proposed work can be used to design some influential wavelength-selective reflectors composed of 1D PCs behind the active region of the solar cells for improving the photovoltaic performance of solar panels. This study can further be utilized for the fabrication of advanced solar cell designs consisting of 1D photonic mirror-based luminescence and reflection concentrators. The low temperature problem which arises in satellites may also be overcome with the help of smart windows based on the proposed multilayer structures.

Highly sensitive one-dimensional Dielectric-Superconductor photonic crystal structure for low temperature sensing applications

The photonic band structures of one-dimensional photonic crystals (1D PCs) with threelayers in a period are studied theoretically. Our results show that complete photonicbandgaps (PBGs) for all polarizations can be obtained in these 1D PCs made of aconventional dielectric material, a negative-permittivity and a negative-permeabilitymetamaterial. The origin of the complete PBGs lies in the existence of surface waves for allpolarizations.

Strongly influenced by the advances in the semiconductor industry, the miniaturization and integration of optical circuits into smaller devices has stimulated considerable research efforts in recent decades. Among other structures, integrated interferometers play a prominent role in the development of photonic devices for on-chip applications ranging from optical communication networks to point-of-care analysis instruments. However, it has been a long-standing challenge to design extremely short interferometer schemes, as long interaction lengths are typically required for a complete modulation transition. Several approaches, including novel materials or sophisticated configurations, have been proposed to overcome some of these size limitations but at the expense of increasing fabrication complexity and cost. Here, we demonstrate for the first time slow light bimodal interferometric behaviour in an integrated single-channel one-dimensional photonic crystal. The proposed structure supports two electromagnetic modes of the same polarization that exhibit a large group velocity difference. Specifically, an over 20-fold reduction in the higher-order-mode group velocity is experimentally shown on a straightforward all-dielectric bimodal structure, leading to a remarkable optical path reduction compared to other conventional interferometers. Moreover, we experimentally demonstrate the significant performance improvement provided by the proposed bimodal photonic crystal interferometer in the creation of an ultra-compact optical modulator and a highly sensitive photonic sensor.

Using cold atoms to simulate strongly interacting quantum systems represents an exciting frontier of physics. However, as atoms are nominally neutral point particles, this limits the types of interactions that can be produced. We propose to use the powerful new platform of cold atoms trapped near nanophotonic systems to extend these limits, enabling a novel quantum material in which atomic spin degrees of freedom, motion, and photons strongly couple over long distances. In this system, an atom trapped near a photonic crystal seeds a localized, tunable cavity mode around the atomic position. We find that this effective cavity facilitates interactions with other atoms within the cavity length, in a way that can be made robust against realistic imperfections. Finally, we show that such phenomena should be accessible using one-dimensional photonic crystal waveguides in which coupling to atoms has already been experimentally demonstrated.

The development of patterned multiquantum well heterostructures in GaAs/AlGaAs waveguides has recently made it possible to achieve exciton-polariton condensation in a topologically protected bound state in the continuum (BIC). Polariton condensation was shown to occur above a saddle point of the two-dimensional polariton dispersion in a one-dimensional photonic crystal waveguide. A rigorous analysis of the condensation phenomenon in these systems, as well as the role of the BIC, is still missing. In the present Letter, we theoretically and experimentally fill this gap by showing that polariton confinement resulting from the negative effective mass and the photonic energy gap in the dispersion play a key role in enhancing the relaxation toward the condensed state. In fact, our results show that low-threshold polariton condensation is achieved within the effective trap created by the exciting laser spot, regardless of whether the resulting confined mode is long-lived (polariton BIC) or short-lived (lossy mode). In both cases, the spatial quantization of the polariton condensate and the threshold differences associated to the corresponding state lifetime are measured and characterized. For a given negative mass, a slightly lower condensation threshold from the polariton BIC mode is found and associated to its reduced radiative losses, as compared to the lossy one.

Tungsten oxide WO3-x is a transition metal oxide and a wide bandgap semiconductor, with a wide range of possible optical and photonic applications. In dependence on the fabrication techniques different stoichiometric ratios (x) and crystalline phases are obtained, which end up with an overall polymorph and extremely versatile material, characterized by tailorable dielectric properties. In particular, WO3-x thin film deposition by Radio-Frequency (RF) sputtering techniques provides a precise control of thickness, composition and nanostructure. In this work we introduce and discuss a specific process of deposition, that is magnetron RF-sputtering as a suitable way to grow WO3-x thin films with selected properties. Possibility of integrating WO3-x thin film on to one-dimensional (1D) photonic crystal structures is also explored. Films are transparent in the near and short-wavelength infrared optical spectral range. Their quality is assessed by morphological, structural and compositional characterizations. Dielectric properties are characterized by optical spectroscopy and ellipsometry, the latter also evaluates the degree of optical anisotropy of thin films in their crystalline phase. An 1D photonics bandgap structure is designed, formed by a SiO2–TiO2 multilayer and capped with a 450 nm-thick transparent WO3-x film, so that surface confinement and local enhancement of the optical field at 1416 nm in the topmost WO3-x layer is obtained.

A two-dimensional perovskite photonic crystal structure of Methylamine lead iodide (CH3NH3PbI3, MAPbI3) is rationally designed as the absorption layer for solar cells. The photonic crystal (PC) structure possesses the distinct “slow light” and band gap effect, leading to the increased absorption efficiency of the absorption layer, and thus the increased photoelectric conversion efficiency of the battery. Simulation results indicate that the best absorption efficiency can be achieved when the scattering element of indium arsenide (InAs) cylinder is arranged in the absorption layer in the form of tetragonal lattice with the height of 0.6 μm, the diameter of 0.24 μm, and the lattice constant of 0.4 μm. In the wide wavelength range of 400–1200 nm, the absorption efficiency can be reached up to 82.5%, which is 70.1% higher than that of the absorption layer without the photonic crystal structure. In addition, the absorption layer with photonic crystal structure has good adaptability to the incident light angle, presenting the stable absorption efficiency of 80% in the wide incident range of 0–80°. The results demonstrate that the absorption layer with photonic crystal structure can realize the wide spectrum, wide angle, and high absorption of incident light, resulting in the increased utilization efficiency of solar energy.

We have measured the intensity of Raman scattering light, which is due to optical phonons, as a function of excitation laser wavelength for the guide-mode band of ${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{As}$-based photonic-crystal-slab line-defect waveguide. As a result, we find that the Raman scattering efficiency is pronouncedly enhanced as the signal wavelength approaches the band edge. Comparison of the result with theoretical prediction reveals that the enhancement should reflect increase of the photon density of states in a divergent manner, which is characteristic of a one-dimensional system.

Phase matching is an important factor that affects the efficiency of nonlinear conversion. A phase matching scheme based on photonic crystal structure is proposed in this paper and the phase matching of photonic crystal was analyzed theoretically. To verify this scheme, we designed a GaAs photonic crystal line defect nonlinear waveguide. By optimizing the line defect width, the phase matching condition was successfully achieved at 288.76 THz. Furthermore, the finite element method was employed to simulate the propagation of electromagnetic wave in the device. The calculated results indicate that the nonlinear conversion efficiency of the nonlinear waveguide device reaches 43,107% (W-1cm-2), with a coherence length exceeding 103 μm. The proposed photonic crystal structure enhances the nonlinear conversion efficiency significantly, which offers a novel approach for realizing phase matching and designing nonlinear optical devices. In addition, this scheme can also be applied to other nonlinear materials.