Stable bright and vortex solitons in photonic crystal fibers with inhomogeneous defocusing nonlinearity

We predict that a photonic crystal fiber whose strands are filled with a defocusing nonlinear medium can support stable bright solitons and also vortex solitons if the strength of the defocusing nonlinearity grows toward the periphery of the fiber. The domains of soliton existence depend on the transverse growth rate of the filling nonlinearity and nonlinearity of the core. Remarkably, solitons exist even when the core material is linear.     

Optical trapping of metal-dielectric nanoparticle clusters near photonic crystal microcavities

We predict the formation of optically trapped, metal-dielectric nanoparticle clusters above photonic crystal microcavities. We determine the conditions on particle size and position for a gold particle to be trapped above the microcavity. We then show that strong field redistribution and enhancement near the trapped gold nanoparticle results in secondary trapping sites for a pair of dielectric nanoparticles.     

Optical vortex solitons in parametric wave mixing

We analyze two-component spatial optical vortex solitons supported by parametric wave mixing processes in a nonlinear bulk medium. We study two distinct cases of such localized waves, namely, parametric vortex solitons due to phase-matched second-harmonic generation in an optical medium with competing quadratic and cubic nonlinear response, and vortex solitons in the presence of third-harmonic generation in a cubic medium. We find, analytically and numerically, the structure of two-component vortex solitons, and also investigate modulational instability of their plane-wave background. In particular, we predict and analyze in detail novel types of vortex solitons, a "halo-vortex," consisting of a two-component vortex core surrounded by a bright ring of its harmonic field, and a "ring-vortex" soliton which is a vortex in a harmonic field that guides a ring-like localized mode of the fundamental-frequency field.     

Observation of second-band vortex solitons in 2D photonic lattices

We demonstrate second-band bright vortex-array solitons in photonic lattices. This constitutes the first experimental observation of higher-band solitons in any 2D periodic system. These solitons possess complex intensity and phase structures, yet they can be excited by a simple highly localized vortex-ring beam. Finally, we show that the linear diffraction of such beams exhibits preferential transport along the lattice axes.     

强非局域非线性介质中的涡旋光孤子

满足强非局域条件时，光束在非局域非线性介质的传输过程由Snyder-Mitchell模型描述.在旋转柱坐标系下求解了Snyder-Mitchell模型，得到涡旋光孤子的自相似旋转解析解.结果表明，涡旋光孤子解在径向是惠特克函数与幂函数的乘积，光束的光强呈环形分布，光束绕光束中心旋转. 关键词： 非局域非线性介质 强非局域性 涡旋光孤子 惠特克函数     

自散焦非局域非线性材料中的光学涡旋孤子

通过数值模拟的方法对非局域非线性自散焦材料中的光学 涡旋孤子的传输特性以及相互作用特性进行了研究. 研究表明, 拓扑荷|m|=1的非局域涡旋孤子是稳定的, 而拓扑荷|m|>1的非局域涡旋孤子均具有拓扑不稳定性. 在微扰存在的情况下以及在近距离相互作用的过程中, |m|>1的涡旋孤子会分裂成一系列的|m|=1的涡旋孤子. 非局域涡旋孤子与局域涡旋孤子具有相同的长距离相互作用模式, 即点涡旋相互作用模式. 但两者的短距离相互作用存在一些差别, 在相同的距离下, 两涡旋间的相互绕转的周期随着材料的非局域响应长度增大而增大. 关键词： 非局域非线性薛定谔方程 自散焦 涡旋孤子     

Observation of discrete vortex solitons in optically induced photonic lattices

We report on the first experimental observation of discrete vortex solitons in two-dimensional optically induced photonic lattices. We demonstrate strong stabilization of an optical vortex by the lattice in a self-focusing nonlinear medium and study the generation of the discrete vortices from a broad class of singular beams.     

Highly noninstantaneous solitons in liquid-core photonic crystal fibers

The nonlinear propagation of pulses in liquid-filled photonic crystal fibers is considered. Because of the slow reorientational nonlinearity of some molecular liquids, the nonlinear modes propagating inside such structures can be approximated, for pulse durations much shorter than the molecular relaxation time, by temporally highly nonlocal solitons, analytical solutions of a linear Schr?dinger equation. The physical relevance of these novel solitons is discussed.     

Optical trirefringence in photonic crystal waveguides

We demonstrate that 2D photonic crystals can possess optical trirefringence in which there are six field orientations for which linear incident light is not perturbed on reflection or transmission. Such a property is rigorously forbidden in homogeneous nonmagnetic dielectrics which can possess only optical birefringence. We experimentally demonstrate this phenomena in silicon-based mesostructures formed from photonic crystal waveguides embedded in a Fabry-Perot cavity. Multirefringence is controlled by the presence of submicron dielectric patterning and is well explained by an exact scattering matrix theory.     

Lateral stress-induced propagation characteristics in photonic crystal fibres

Using the finite element method, this paper investigates lateral stress-induced propagation characteristics in a photonic crystal fibre of hexagonal symmetry. The results of simulation show the strong stress dependence of effective index of the fundamental guided mode, phase modal birefringence and confinement loss. It also finds that the contribution of the geometrical effect that is related only to deformation of the photonic crystal fibre and the stress-related contribution to phase modal birefringence and confinement loss are entirely different. Furthermore, polarization-dependent stress sensitivity of confinement loss is proposed in this paper.     

Waveguide arrays in selectively infiltrated photonic crystal fibres

The periodic array of air holes in the cladding of a photonic crystal fibre (PCF) provides a convenient scaffold for the introduction of an infiltrating liquid. In this paper we demonstrate a novel platform of one-dimensional tuneable nonlinear photonic lattices produced by selectively infiltrating a row of holes in a PCF. Such structures have been realised by blocking individual holes on one end of a PCF, leaving the desired infiltration pattern unblocked. Unblocked holes are then infiltrated by immersing the unblocked end of the fibre in a reservoir of the infiltrating liquid, allowing for the realisation of a wide variety of periodic structures. Such structures are studied for traditional linear and nonlinear effects in periodic systems.     

Raman perturbation and surface core soliton in hollow photonic crystal fiber

Effect of Raman scattering and higher order dispersion are investigated in case of surface core or gap solitons, known to exist in hollow core photonic crystal fibers. The necessary conditions for the existence of the soliton are analyzed in the parameter plane. It is observed that these conditions are compatible with the famous Vakhitov-Kolokolov (VK) criterion. In the later part the system of partial differential equations are solved by ETDRK method from which the shapes of the pulses are investigated as it travels along the z direction. Both the terms, intrapulse Raman scattering and higher order dispersion have important effect on the propagation characteristics     

共振光子晶体中Laue孤子传播的动力学行为

从理论上研究了Laue孤子传播的动力学行为，并通过数值模拟验证了这些行为.结果表明，由于非线性衍射，入射脉冲会分裂产生四种模式，其中产生的Laue孤子的传播行为与一般共振介质中孤子的传播行为相似.     

Temperature dependence of birefringence in olarization-maintaining photonic crystal fibres

In this paper,the temperature dependence of birefringence in polarization maintaining photonic crystal fibres(PMPCFs) is investigated theoretically and experimentally.Utilizing the structural parameters of the PM-PCF samples in the experiment,two effects leading to the birefringence variation under different temperatures are analysed,which are the thermal expansion of silica material and the refractive index variation due to the temperature variation.The actual birefringence variation of the PM-PCF is the combination of the two effects,which is in the order of 10-9 K-1 for both fibre samples.Calculation results also show that the influence of refractive index variation is the dominant contribution,which determines the tendency of the fibre birefringence variation with varying temperature.Then,the birefringence beat lengths of the two fibre samples are measured under the temperature,which varies from -40℃ to 80℃.A traditional PANDA-type polarization maintaining fibre(PMF) is also measured in the same way for comparison.The experimental results indicate that the birefringence variation of the PM-PCF due to temperature variation is far smaller than that of the traditional PMF,which agrees with the theoretical analysis.The ultra-low temperature dependence of the birefringence in the PM-PCF has great potential applications in temperature-insensitive fibre interferometers,fibre sensors,and fibre gyroscopes.     

Optical wave propagation in photonic crystal metamaterials

Metamaterials that provide negative refraction can be implemented in photonic crystals (PhCs) through careful design of the devices. Theoretically, we demonstrate that the dispersion can be altered to achieve negative refraction. This can be done through engineering the geometry of the device as well as selecting appropriate materials. The PhC also demonstrates slow light that facilitate sensing chemicals or biological agents. Using metallic materials such as gold nano-particle enables PhCs to guide optical waves in desired pathways. Also using magnetic materials such as highly doped n-GaAs, we can tune the band gap by changing magnetic field. The simulated results are consistent with some of the previously reported experimental results and give us guidance for future experiments.     

一维反铁磁光子晶体光学双稳态效应研究

基于传递矩阵方法和光局域化原理, 本文研究了一维反铁磁光子晶体共振频率附近光学双稳态效应随电磁波入射角、 外磁场强度及电介质层数的变化.研究发现, 当外磁场为1.0 kG(1 G=10^-4 T)、电磁波小角度入射时, 反铁磁材料高低共振频率附近均可探测到光学双稳态效应; 当电磁波大角度入射时, 仅在高共振频率附近探测到光学双稳态效应. 然而, 当外磁场强度增加到2.0 kG时, 由于反铁磁材料的高低共振频率向两侧移动, 低共振频率附近缺失的光学双稳态频率窗口又被有效激发. 此外, 电磁波小角度入射时, 电介质层数在低共振频率附近对双稳态效应影响较明显.     

Dispersion management in soft glass all-solid photonic crystal fibres

The development of all-solid photonic crystal fibres for nonlinear optics is an alternative approach to air-glass solid core photonic crystal fibres. The use of soft glasses ensures a high refractive index contrast (> 0.1) and a high nonlinear coefficient of the fibres. We report on the dispersion management capabilities in all-solid photonic crystal fibres taking into account four thermally matched glasses which can be jointly processed using the stack-and-draw fibre technique. We present structures with over 450 nm broadband flat normal dispersion and ultra-flat near zero anomalous dispersion below 5 ps/nm/km over 300 nm dedicated to supercontinuum generation with 1540 nm laser sources. The development of an all-solid photonic crystal fibre made of F2 and NC21 glasses is presented. The fibre is used to demonstrate supercontinuum generation in the range of 730?C870 nm (150 nm) with flatness below 5 dB.     

Tunability of discrete diffraction in photonic liquid crystal fibres

In this paper theoretical and experimental results regarding discrete light propagation in photonic liquid crystal fibres (PLCFs) are presented. Particular interest is focused on tunability of the beam guidance obtained due to the variation in either external temperature or optical power (with assumption of thermal nonlinearity taking place in liquid crystals). Highly tunable (discrete) diffraction and thermal self-(de)focusing are studied and tested in experimental conditions. Specifically, spatial light localization and/or delocalization due to the change in tuning parameters are demonstrated, with possibility of discrete spatial (gap) soliton propagation in particular conditions. Results of numerical simulations (performed for the Gaussian beams of different widths and wavelengths) have been compared to those from experimental tests performed in the PLCFs of interest. Owning to the limit of experimental means, direct qualitative comparison was not quite accessible. Nevertheless, a qualitative agreement between theoretical and experimental data (obtained in analogous conditions) has been achieved, suggesting a compact and widely-accessible platform for the study of tunable linear (and nonlinear) discrete light propagation in two-dimensional systems. Proposed photonic structures are of a great potential for all-optical beam shaping and switching.     

Optical sensing with photonic crystal fibers

A review of optical fiber sensing demonstrations based on photonic crystal fibers is presented. The text is organized in five main sections: the first three deal with sensing approaches relying on fiber Bragg gratings, long‐period gratings and interferometric structures; the fourth one reports applications of these fibers for gas and liquid sensing; finally, the last section focuses on the exploitation of nonlinear effects in photonic crystal fibers for sensing.