Propagation of the radiation field excited on discontinuities of optical waveguides

Numerical and semi-analytical techniques widely used to model the complicated structure of the radiation field excited on sharp and smooth discontinuities of a dielectric slab are reviewed. Comparative analysis of the radiation field modelling by the fast Fourier transformation-beam propagation method (FFT-BPM) and the finite difference (FD)-BPM is presented. Propagation of a higher-order mode through the cut-off cross-section of smooth and sharp discontinuities is simulated numerically by the FD-BPM, the total field is analysed using the leaky mode approach.     

Critical ray-like propagation modes along graded-index planar optical waveguides

Graded-index planar optical waveguides and surface compression layers were formed simultaneously in the surface layer of glass plates by ion exchange. A change in the refractometer patterns was observed. Before ion exchange, only a critical ray fringe was observed, but with ion exchange a guided wave fringe appeared on the high effective refractive index side of the ‘critical ray’ fringe, and the number of guided wave fringes increased. The guided wave fringe or fringes were birefringent, whereas the ‘critical ray’ fringe was kept nonbirefringent. It was concluded that the ‘critical ray’ propagated along the bottom of a waveguide, ie at the foot of the refractive index distribution.     

非线性介质光波导中的传输功率和光学双稳态

本文对结构为非线性包层/线性芯层/非线性衬底的非线性介质光波导的传输特性进行了深入的分析,给出了模场分布函数,色散关系和传输功率的一组形式统一的公式,并对其传输功率的光学双稳态特性进行了讨论.     

Ti：LiNbO3光波导导模的场分布

给出了Ti扩散LiNbO_3条波导任意阶导模场分布的试探解.通过变分法分析,不但可以合理地确定其中的待定参数,而且也得到了相应导模传播常数的近似值.与扩展的有效折射率方法比较:这种解不但在函数形式上简单,待定常数确定方便,而且具有精度高的优点.还可以得到等效一维波导折射率分布的解析表达式.     

金属包层渐变折射率介质光波导的传输特性与损耗

用金属包层介质光波导损耗的微扰理论及藉助多层近似法用递推公式分析渐变折射率波导传播常数的方法,对几种类型的金属包层渐变折射率介质光波导的传输特性与损耗进行分析和讨论,得到了与精确数值计算结果相吻合的结果.     

Spatial effects in the linear propagation of drastically ultrashort optical pulses in single-mode waveguides

We analyze the effect of the varying transverse field profile associated to the linear propagation of ultrashort pulses along an optical waveguide. This effect has been systematically ignored in the literature. Based on numerical calculations, we analyze the magnitude of such effect to justify the use of the standard model, at least for pulses larger than about 5–7 optical carrier cycles. Theoretical considerations are presented about the extreme difficulty of even establishing the initial mathematical condition of the propagation problem under such circumstances.     

微环耦合谐振光波导中的色散控制模型与数值仿真

本文利用传输矩阵法得到了微环耦合谐振光波导的色散关系,讨论了耦合损耗、传输损耗及耦合系数对微环耦合谐振光波导色散的影响,改变耦合损耗、传输损耗及耦合系数可控制其色散曲线的形状、位置、以及带宽,色散曲线的变化及控制对微环耦合谐振光波导在滤波、光信号延迟及缓存等方面的应用有重要意义. 关键词： 光波导 微环光波导 传输矩阵法     

洛伦兹光束经光阑失调傍轴光学系统的传输

基于广义衍射积分公式和光阑函数的复高斯展开,导出了一洛伦兹光束经一个带圆形光阑失调傍轴光学系统的近似解析传输公式.作为一般公式的特例,还给出了洛伦兹光束经一无光阑失调傍轴光学系统的解析传输式.作为数值计算的例子,运用所得到的公式分析了洛伦兹光束经带光阑失调薄透镜的传输特性.结果表明：不同强度的衍射即圆形光阑半径的大小明显影响衍射光束的归一化强度分布及其传输变化规律. 关键词： 洛伦兹光束 失调傍轴光学系统 光束传输     

Fabrication and characterization of polyethylene terephatate optical waveguides

In this paper, the fabrication and characterization of polyethylene terephatate (PET) thin film integrated optical waveguide is presented. Dip-coating technique has been used to fabricate the optical waveguide using PET. Various waveguide properties, such as mode effective refractive index, optical loss, dispersion and waveguide thickness as a function of temperature of waveguides have been reported. The optical loss are found to be <1 dB cm^–1.     

加入增益介质的表面等离子体激元耦合共振波导传输特性理论研究

将增益介质加入金属环构成的表面等离子体激元耦合共振波导,利用传输矩阵及时域有限差分方法研究了不同增益系数下该耦合共振波导的透射谱线、色散关系以及群折射率.结果表明,增益介质共振频率附近的反常色散及正常色散变化能有效影响由共振波导几何结构决定的色散关系曲线,且具有相反的效果,分别使其变得平坦和陡峭,从而放大和缩小由共振波导几何结构决定的群折射率.另外,增益系数随外加抽运光改变的特点使得加入增益介质的耦合共振波导具有传输性能可灵活调节特性.文章的研究对促进耦合共振波导在高密度光学集成中的广泛应用具有积极意义. 关键词： 增益介质 耦合共振波导 表面等离子体激元 群折射率     

Strong optical non-linearities for efficient all-optical switching in GaAlAs waveguides

The light intensity transmission of GaAlAs strip waveguides is sensitively dependent on the strength of the electric field inside the waveguide, when the photon energy is close to the band gap (Franz-Keldysh effect). In a waveguide embedded in a pn-junction the transmitted light itself induces the field changes through the photoelectric effect. This photo-induced Franz-Keldysh effect causes a non-linear intensity transmission of the waveguide. Light power levels far below 1 mW are sufficient to give strong non-linearities. Possible application schemes for modulation and all-optical switching in integrated optics and optoelectronics are discussed.     

Propagation of a Lorentz-Gauss beam through a misaligned optical system

Based on the generalized integral formula and the convolution theorem of the Fourier transform, an analytical propagation formula of a Lorentz-Gauss beam passing through a misaligned paraxial optical system is derived. As numerical examples, the propagation properties of a Lorentz-Gauss beam through a misaligned thin lens with the lateral displacement and the angle displacement are graphically illustrated, respectively. The influences of the lateral displacement and the angle displacement of the misaligned thin lens on the normalized light intensity and the phase distributions are also examined, respectively.     

Coupled magnetic resonator optical waveguides

Optical resonators are important devices that control the properties of light and manipulate light–matter interaction. Various optical resonators are designed and fabricated using different techniques. For example, in coupled resonator optical waveguides, light energy is transported to other resonators through near‐field coupling. In recent years, magnetic optical resonators based on LC resonance have been realized in several metallic microstructures. Such devices possess stronger local resonance and lower radiation loss compared with electric optical resonators. This study provides an overall introduction on the latest progress in coupled magnetic resonator optical waveguide (CMROW). Various waveguides composed of different magnetic resonators are presented and Lagrangian formalism is used to describe the CMROW. Moreover, several interesting properties of CMROWs, such as abnormal dispersions and slow‐light effects, are discussed and CMROW applications in nonlinear and quantum optics are shown. Future novel nanophotonic devices can be developed using CMROWs.     

Analytical investigations of planar optical waveguides with arbitrary index profile

We present here an improvement of the existing equivalent attenuated vector (EAV) method. It is shown that our study gives not only analytical dispersion equation with clear physical insight, but also the extremely accurate propagation constants for planar waveguides with arbitrary index profiles.     

All-optical broadband variable optical attenuators and switches in plasmonic teeth waveguides

All-optical broadband variable optical attenuators (VOAs) and switches based on plasmonic teeth shaped waveguides have been proposed and numerically investigated. The Finite Difference Time Domain (FDTD) simulation results reveal that VOAs based on three teeth structure filled with CdSe-doped PMMA can continuously attenuate the power of a light beam from 3.7 dB to 39 dB within a broad forbidden band by an external control light. For wavelengths within the forbidden band, the structure can also operate as a switch with presence or absence of pumping light corresponding to on or off state. For a modulation depth of 27 dB, a relatively small variation in the absorption coefficient of CdSe QD-PMMA in side cavity (from κ = 0 to κ = 0.15) is enough.     

Broad band Bragg deflector for optical waveguides on silicon substrates

Technical solutions are described which allow the 500 MHz acousto-optical Bragg deflector integrated onto a silicon substrate to have a good performance and quite high deflection efficiency. This is achieved by diminishing the influence of acoustic propagation losses. As a consequence, is it possible to implement a large bandwidth acousto-optical rf spectrum analyser using fully planar technology.     

Cerium dioxide thin film optical waveguides

Cerium dioxide thin film optical waveguides were fabricated by an RF magnetron sputtering process. The films were deposited on glass substrates and on silicon dioxide layers grown on silicon substrates. Optical loss measurements for the fabricated waveguides are reported. It is seen that the volume losses in the films were fairly high compared with the surface losses.     

Femtosecond laser micromachined optical waveguides in LiTaO3 crystal

By using femtosecond laser micromachining, optical wave guides in both depressed cladding and dual‐line configurations have been produced in LiTaO₃ crystal. The guiding properties and the thermal stability have been investigated for both geometries, which exhibit different performance. Depressed cladding waveguides support guidance along both extraordinary and ordinary index polarizations, while dual‐line waveguides support only extraordinary index polarization. Thermal annealing has been proved to be an effective method to reduce the propagation losses. For the cladding waveguide, the lowest propagation loss was as low as 0.38 dB/cm after the annealing treatment at 400 °C. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

厄米-余弦-高斯光束通过具有光阑光学系统时的传输特性

当厄米_余弦_高斯光束通过带有矩形光阑的一阶ABCD近轴光学系统时,可由Collins公式给出其场分布的积分形式。将其中硬边光阑的窗口函数写成矩形函数,并将矩形函数用高斯函数展开,通过积分可得到由光阑限制的厄米_余弦_高斯光束传输的解析式。分析和讨论了厄米_余弦_高斯光束通过具有圆孔光阑限制的薄透镜系统时的情况,其结果与直接用广义衍射积分公式进行复杂数值计算时的结果完全一致。这样不仅便于进行物理分析,而且也节省了计算机的计算时间。     

Calculation of cutoff frequency of arbitrary weak guidance optical waveguides by extended boundary condition method

The extended boundary condition method is applied to both circular and elliptical regions for calculating cutoff frequencies V_c of weakly guiding optical waveguides, which consist of a uniform cladding and a core with arbitrary shape and index profile. The frequency shift formula method is explained by means of the extended boundary condition method on circular regions. Comparing the method with analytic and other rigorous methods, we show that it is indeed a powerful tool. Numerical results confirm that the mode designation and arrangement order in elliptical and rectangular waveguides are, in general, dependent on the aspect ratio.