Nonlinear dispersion in a coupled-resonator optical waveguide

The propagation of an optical pulse in a coupled-resonator optical waveguide may be calculated nonperturbatively to all orders of dispersion, in the conventional tight-binding approximation, even though the dispersion relationship is nonlinear. Working in this framework, we discuss limits of the physical parameters and approximations to the exact formulation that highlight the conditions under which pulse distortion can be minimized. The results are fundamental to the design of coupled-resonator optical waveguides and are also relevant to other applications of the tight-binding method.     

Miniband transmission in a photonic crystal coupled-resonator optical waveguide

We demonstrate in the near infrared the coupled-resonator optical waveguide (CROW) concept that was recently proposed by Yariv et al. [Opt. Lett.24, 711 (1999)]. Two-dimensional photonic crystals have been used to define, in a GaAs-based waveguiding heterostructure, an array of micrometer-sized hexagonal cavities coupled through thin walls. With the photoexcitation of InAs quantum dots as an internal source, the transmission spectra of the coupled resonators show marked minibands and minigaps, in agreement with theoretical predictions.     

Dispersion characteristics of coupled-resonator optical waveguides

A tight-binding optical waveguide formed by proximity coupling of nearest-neighbor resonators, e.g., a coupled-resonator optical waveguide (CROW), has distinct wave and pulse propagation characteristics compared with a conventional waveguide, and several applications in photonic devices have been proposed recently. But analysis of the dispersion, and in particular the group-velocity dispersion, in such a waveguide requires particular attention: the waveguide displays two distinct regimes of operation, depending on the position of the wave packet in the dispersion relationship.     

Subwavelength-diameter silica wire for light in-coupling to silicon-based waveguide

Coupling between subwavelength-diameter silica wires and silicon-based waveguides is studied using the parallel three-dimensional (3D) finite-different time-domain method.     

Engineering the light propagating features through the two-dimensional coupled-cavity photonic crystal waveguides

This paper studies the propagating characteristics of the electromagnetic waves through the coupled-resonator optical waveguides based on the two-dimensional square-lattice photonic crystals by the finite-difference time-domain method.When the traditional circular rods adjacent to the centre of the cavities are replaced by the oval rods,the simulated results show that the waveguide mode region can be adjusted only by the alteration of the oval rods’ obliquity.When the obliquity of the oval rods around one cavity is different from the obliquity of that around the adjacent cavities,the group velocities of the waveguide modes can be greatly reduced and the information of different frequencies can be shared and chosen at the same time by the waveguide branches with different structures.If the obliquities of the oval rods around two adjacent cavities are equal and they alternate between two values,the group velocities can be further reduced and a maximum value of 0.0008c(c is the light velocity in vacuum) can be acquired.     

Slow light engineering in a photonic crystal slab waveguide through optofluidic infiltration and geometric modulation

In this paper, a new type of flat-band slow light structure with high group index (n _g) and large normalized delay-bandwidth product (NDBP) in a silicon on insulator (SOI) based photonic crystal (PC) slab waveguide with a triangular lattice of circular holes is demonstrated. The dispersion engineering is performed by infiltrating optical fluids with different refractive indices n _f in the first row and shifting the second row of air holes adjacent to the PC waveguide (PCW) in the longitudinal direction. In the optimized case, a high NDBP of 0.32 with a group index of 54.55 and a bandwidth of 9.13 nm could be obtained. Furthermore, an ultra-low group velocity dispersion (GVD) in the range of 10^–20 s²/m is achieved in all of the structures. These results are obtained by numerical simulations based on three-dimensional (3D) plane wave expansion (PWE) method.     

A propagating beam analysis of optical waveguide couplers

We study the mode coupling among the local normal modes of couplers formed from planar parabolic graded-index tapered optical waveguides with the propagating beam method. Our results indicate that couplers whose radiia (z) depend on axial length as \Lambda /2$$ " align="middle" border="0"> , have many desirable properties not possessed by other couplers.     

Slow light using semiconductor optical amplifiers: Model and noise characteristics

We developed an improved model in order to predict the RF behavior of the SOA valid for any experimental conditions. It takes into account the dynamic saturation of the SOA, which can be fully characterized by a simple measurement, and only relies on material fitting parameters, independent of the optical intensity and bias current. We used this new model to analyze and model the additive noise of the SOA in order to fully characterize the influence of the slow light effect on the microwave photonics link properties. To cite this article: P. Berger et al., C. R. Physique 10 (2009).     

ABCD law for partially coherent Gaussian light,propagating through first-order optical systems

This paper shows under what condition the well-knownABCD law — which can be applied to describe the propagation of one-dimensional Gaussian light through first-order optical systems (orABCD systems) — can be extended to more than one dimension. It is shown that in the two-dimensional (or higher-dimensional) case anABCD law only holds for partially coherent Gaussian light for which the matrix of second-order moments of the Wigner distribution function is proportional to a symplectic matrix. Moreover, it is shown that this is the case if we are dealing with a special kind of Gaussian Schell model light, for which the real parts of the quadratic forms that arise in the exponents of the Gaussians are described by the same real, positive-definite symmetric matrix.     

Evolution of nonclassical light propagating through passive optical coupled waveguides: Entanglement dynamic

In this paper, nonclassical light propagation through passive optical coupler is investigated. On the other hand, passive optical device design for nonclassical light is analyzed in this work. Effect of mode mismatching including mismatching in propagation constant on operation of the considered device is studied. We investigate different separable and entangled input excitations with single photons in this case. We specially study the measure of entanglement and effect of propagation constant mismatch on it. The simultaneous effect of loss and mismatch is also studied. Obtained results for different excitation states illustrate that there is a possibility to design such that the system operation can be immune versus fabrication imperfections.     

Slow light performance enhancement of graphene-based photonic crystal waveguide

We propose a graphene-based photonic crystal (PC) slow light waveguide, which is realized by creating periodical air holes in a silicon layer to achieve spatially varying chemical potentials of graphene. The structure is optimized around 30 THz, and a large group index of 166.6 is obtained, with a very low propagation loss of ?2.1 dB/um. The corresponding normalized delay-bandwidth product reaches as high as 4.00. Furthermore, the slow light performance can be dynamically tuned by changing a bias voltage. The center frequency of the slow light waveguide can be tuned between 19.1 THz and 27.4 THz. Our results suggest that graphene-based PC structures are very promising for slow light devices.     

Electron transport through curved two-dimensional quantum waveguide

This paper details the study of electron transport through a two-dimensional curved quantum waveguide. The curvature of the quantum waveguide is found to greatly affect the transport properties. It is shown that no evanescent mode exists when the inner radius of the curved part of the waveguide is zero. Also, this paper details how localized modes with energy below the Fermi energy can be formed in the curved part due to curvilinear effects. A series of Fano-resonance type dips of the transmission coefficient appear because of the presence of localized modes. Due to the quantum effect, the transmission coefficient and the traversal time increase nonlinearly with the curved angle θ₀${\theta }_0$. This nonlinear property is destroyed as the radius increases.     

二维平板光子晶体直波导的制备和光传输特性的测量

利用聚焦离子束刻蚀的方法在SOI(silicon on insulator)基片上制备了W3型二维光子晶体直波导.观察并测量了近红外激光通过光子晶体波导的散射图形和透过谱.实验结果说明，激光在有引入引出脊形波导的光子晶体直波导中具有很好的传输特性. 关键词： 光子晶体波导 光子带隙 脊型波导     

光脉冲在微环耦合谐振光波导中传输线性特性的数值仿真

利用传输矩阵法得到了微环耦合谐振光波导色散关系的一般表达式,并由色散关系出发讨论了光脉冲在微环耦合谐振光波导中传输时的线性特性,包括带宽、群速度、色散和线性相位变化,这些特性对微环耦合谐振光波导在光通信和光传感领域的应用有重要意义. 关键词： 微环光波导 光脉冲线性特性 传输矩阵法 数值仿真     

Determination of the absorption for incident light propagating parallel through the guest–host polymer film waveguide

Guest–host polymer thin films of polymethyl methacrylate (PMMA) incorporated with (4′-nitrobenzene)-3-azo-9-ethylcarbazole (NAEC) were fabricated by spin coating and then poled by the method of corona-onset poling at elevated temperature. The absorption mechanism of the polymeric film, which is very important for the optical transmission losses and directly relates to the orientation of chromophore NAEC in polymer PMMA, was investigated in detail. From the UV–visible absorption spectra for NAEC/PMMA film before and after being poled, we determined the change of absorption coefficient κ with the wavelength and approximately calculated the maximum absorption A_max as 3.46 for incident light propagating parallel through the film, i.e. the ordinary polarized light, which cannot be directly measured in the spectrophotometer.     

纳米集成光路中的光源、光波导和光增强

使用近场光学显微术(scanning near-field optical microscopy, SNOM)研究了ZnO亚微米线端面出射性质,不同空间形貌Ⅱ-Ⅵ族半导体荧光器件光波导特性,二维光子晶体、准晶光子晶体对LED的出射增强作用以及表面等离激元(surface plasmon polariton, SPP)与半导体纳米荧光器件的相互作用,对纳米集成光路中的光源、光波导、光增强三个重要问题做了实验和理论上的分析.研究发现半导体微纳米线端面出射光束的质量与样品的直径有密切关系.通过合理地设计其直径和 关键词： 纳米集成光路 扫描近场光学显微术 光波导 光增强     

纳米集成光路中的光源、光波导和光增强

使用近场光学显微术(scanning near-field optical microscopy, SNOM)研究了ZnO亚微米线端面出射性质，不同空间形貌Ⅱ-Ⅵ族半导体荧光器件光波导特性，二维光子晶体、准晶光子晶体对LED的出射增强作用以及表面等离激元(surface plasmon polariton, SPP)与半导体纳米荧光器件的相互作用，对纳米集成光路中的光源、光波导、光增强三个重要问题做了实验和理论上的分析.研究发现半导体微纳米线端面出射光束的质量与样品的直径有密切关系.通过合理地设计其直径和     

Transmission characteristics of optical waveguide corners

Two-dimensional dielectric waveguide corners with air reflector or metal reflector have been investigated by means of the method of plane-wave expansion, which has the advantage of being compact for optical integrated circuit applications. The operating principle of these waveguide corners is based on the total internal reflection or large partial reflection. The corner losses and field profiles are presented for various waveguide parameters. It is found that the corner loss can be small if the waveguide corner is properly fabricated.     

Slow light in a dielectric slab waveguide with a negative refractive index photonic crystal substrate

Slow light effect in a dielectric slab waveguide with a negative refractive index photonic crystal substrate is numerically investigated. The guided modes are confined in the core layer by total internal reflection. Dispersion and wave propagating properties are explored in details. The result demonstrates that light speed can approach zero at two adjacent frequencies, which is also verified by finite-difference time-domain (FDTD) simulation. Calculated Q-factors both exceed several thousand. The structure has the potential to be used as high-Q open cavity for dual-wavelength lasers or traveling wave amplifiers.     

Slow light in photonic crystals waveguide constructed with symmetrically perturbed structure

Symmetrically perturbed photonic crystal waveguide can be constructed by inserting perturbative dielectric rods into photonic crystal waveguide structure with whose rods’ radius distributed according to a certain proportion. Slow light properties in this new structure are studied by using the plane wave expansion method (PWM). In this paper, schemes of adjusting radius of perturbative dielectric rods and adjusting the dielectric constant of perturbative dielectric rods are proposed to optimize slow light properties. The result shows that the scheme for adjusting radius of perturbative rods can realize larger average slow light bandwidth and efficiently control the NDBP value of the waveguide, but it contributes little to obtain smaller group velocity. The scheme for adjusting dielectric constant of perturbative rods can realize smaller group velocity, but can only obtain smaller slow light bandwidth and cannot efficiently enlarge NDBP value of waveguide. Both optimization schemes proposed in this paper realize group velocity that is two magnitudes smaller than the vacuum speed of light meanwhile maintaining large NDBP and low GVD region. Our results provide important theoretical basis for the potential application offered by symmetrically perturbed photonic crystal in future optical networks.