介质损耗对左手媒质周期结构频率选择特性的影响

采用多模网络与严格的模匹配相结合的方法研究了介质损耗对左手媒质构成的周期结构频率选择特性的影响;并对其中的新现象给予了解释.讨论了损耗对左手和右手周期结构的频率选择特性影响的差异.本文得到的结果对于精确设计新的毫米波频率选择表面有一定的指导意义.     

一维各向异性掺杂光子晶体的缺陷模特性

利用传输矩阵的方法给出了光波在一维各向异性掺杂光子晶体中传播的透射率,研究了缺陷模的相关特性,经数值模拟计算得出:光通过一维各向异性掺杂光子晶体后,透射波中TE波和TM波存在明显的缺陷模,缺陷模的中心波长位置随光波入射角的改变而不同,两个缺陷模能完全分开;TE波的缺陷模中心波长位置随着光学厚度的增大向短波方向移动,TM...     

Gain saturation properties of a semiconductor gain medium withtensile and compressive strain quantum wells

Gain saturation properties of a multiple-quantum-well structure with both tensile and compressively strained quantum wells are investigated analytically. This type of structure has recently been experimentally demonstrated to serve as a basis for the implementation of a two-polarization/two-frequency laser and polarization insensitive travelling wave(TW) amplifier. The performance of these devices strongly depends on the interaction between the TE and TM gains of the structure. The gain medium model appropriate for this type of structure is developed and the rate equation approach is used to describe the saturation properties of TE/TM gains and the coupling between the TE and TM gains due to gain saturation. The minimum amount of coupling between the two is governed by the basic symmetry of the light-hole wavefunction which interacts with photons of both polarization: photon cross-coupling. The finite rate of carrier escape from the quantum wells provides for carrier induced coupling between the populations of the two well types and therefore also couples TE and TM gains: carrier cross-coupling. The performance of a polarization insensitive amplifier, laser, and polarization control element is evaluated as a function of the amount of carrier cross-coupling, which is a structure dependent parameter. A structure with high degree of cross-coupling is desirable for polarization insensitive TW amplifier, while two-polarization lasers and polarization control elements require minimum cross-coupling     

含负折射率光子晶体缺陷模偏振态的吸收特性

为了研究含负折射率掺杂光子晶体各缺陷模偏振态的吸收特性,引入复折射率并利用光学特征矩阵法进行分析,结果表明：杂质的消光系数对TE波和TM波的缺陷模均有影响,但对TE波的影响更为明显;当消光系数一定时,对TE波而言,中心波长相对较大的两个缺陷模透射峰值均随入射角的增加而迅速减小,而TM波的三个缺陷模透射峰均随入射角的增加而增加。利用这一特性可以设计双（多）通道光子晶体偏振滤波器。     

1维3元磁化等离子体光子晶体传输特性分析

为了研究1维3元磁化等离子体光子晶体的传输特性,采用传输矩阵法得到了TE波通过1维3元磁化等离子体光子晶体后的左旋和右旋极化波的传输特性,用计算得到的透射系数来讨论了周期常数、介电常数、介质层厚度和等离子体参量对其传输特性的影响。结果表明,改变介电常数、介质层厚度和等离子体频率可以实现对禁带数目和宽度的调谐,改变周期数和等离子体碰撞频率不能影响禁带带宽;等离子体回旋频率仅仅能影响右旋极化波的禁带带宽,对左旋极化波的禁带带宽无影响。这为设计1维3元磁化等离子体光子晶体器件提供了理论参考。     

150 nm亚波长铝光栅的近红外偏振特性

采用纳米压印、反应离子辅助刻蚀及物理溅射技术制作了周期为150 nm的铝光栅,用分光光度计测量了样品的透过率随入射光偏振方向变化的关系以及在可见、近红外波段TE,TM波的透射光谱。利用严格耦合波理论对光栅的上述性能进行了数值模拟和理论分析。考察了斜入射情况下样品的性能及损耗随入射角的变化关系。理论和实验结果表明,光栅的透过率对入射光的偏振态十分敏感:在近红外范围内(1000~2000 nm)对TE波完全反射,对TM波具有90%的透过率,并且在斜入射时因入射角的增大而轻微加强。此外,还比较了不同金属材料光栅的TM波近红外透射特性,探讨了改善其性能的途径。     

Generation of Polarization-Entangled Photons by Type-II Quasi-Phase-Matched Waveguide Nonlinear-Optic Device

A cross-polarized twin-photon generation device was implemented with Ti-indiffused LiNbO₃ waveguides and gratings for type-II (TE rarr TE + TM) quasi-phase matching. Generation of polarization-entangled twin-photon beams by a simple system using the fabricated device is demonstrated through quantum interference and photon polarization measurement experiment.     

Tunable planar polymer Bragg gratings having exceptionally low polarization sensitivity

We report fabrication of planar polymer Bragg gratings that can be thermally tuned 20 nm with very low polarization sensitivity, (/spl lambda//sub TE/-/spl lambda//sub TM/)相似文献   

Rigorous Analysis of the Scattering of Surface Waves in an Abruptly Ended Slab Dielectric Waveguide

The reflection and the scattering properties of even TE and TM surface waves incident in an abruptly ended dielectric slab waveguide are analyzed. The discontinuity is regarded as a junction between two open waveguides namely the dielectric slab waveguide and the free space waveguide. The boundary conditions acting together with the orthogonality provide singular coupled integral equations on the discrete and the continuous wave amplitudes at the discontinuity. These singular coupled intergral equations with Cauchy kernels and infinite limits of integration are solved by iteration via the Neuman series. Numerical results are presented for the reflectivity of the even TE/sub 0/ and TM/sub 0/ fundamental modes, together with their mode conversion on even TE/sub 2/ and TM/sub 2/ in a slab where two guided modes can propagate. Reflectivity and mode conversion of higher order excitations are also investigated     

A polarization independent GaAs-AlGaAs electrooptic modulator

Two designs for polarization independent GaAs-AlGaAs interferometric electrooptic modulators are described. One design uses the linear electrooptic effect to couple degenerate TE/TM eigenmodes of a single-mode waveguide. In the other design the eigenmodes need only be near degenerate. The design using the coupling between near degenerate TE/TM modes utilizes a novel biasing scheme. A novel polarization independent GaAs-AlGaAs interferometric optical modulator based on this design has been fabricated and characterized at 1.3 μm. This modulator is fabricated as a traveling wave modulator incorporating 50 Ω, phase velocity matched, low microwave loss electrodes for maximum electrical bandwidth     

Exact derivation of the coupling coefficient in corrugated waveguides with rectangular tooth shape

An exact analysis, based on local field expansion, is used in order to calculate the coupling coefficient in corrugated waveguide structures having rectangular tooth shape and small tooth height. In particular, the coupling coefficients for TE field polarization and TM field polarization are derived. It is shown that the expression for the TE coupling is identical with previous results based on the coupled wave formalism and on other techniques as well. This is a consequence of the formal validity of the equivalent index method for TE polarized waves. In the case of TM coupling, the equivalent index method does not hold and the expression for the coupling coefficient deviates significantly from the results obtained by the coupled mode formalism.     

TE-TM mode conversion of an optical beam wave in thin-film opticalwaveguides

The TE-TM mode conversion efficiency when a Gaussian beam wave propagates in thin-film optical waveguides is discussed. For film thicknesses at which strong coupling between the TE and TM modes is obtained, two hybrid modes have oppositely rotating circular polarizations, or linear polarizations perpendicular to each other with equal magnitude of TE-wave and TM-wave components. In the former (i.e. circular polarization), complete TE-TM mode conversion is impossible. In the latter (i.e. linear polarization) complete TE-TM mode conversion is available. These claims are based on the fact that the direction of power flow of the hybrid modes depends on the polarization     

杂质吸收对光子晶体缺陷模偏振态的影响

引入复折射率并利用特征矩阵法,研究了杂质的吸收对TE波和TM波缺陷模透射峰的影响.得出:杂质的消光系数对TE波和TM波的缺陷模透射峰都有显著的影响,但对TE波缺陷模的影响比对TM波缺陷模的影响更为明显.当消光系数一定时,TE波的缺陷模透射峰随入射角的增大而迅速减小,而TM波的缺陷模透射峰随入射角的增大而增大.利用这一特性可以设计光子晶体偏振滤波器.     

椭圆偏振光在各向异性1维光子晶体中的传输

为了解决利用传统传输矩阵法计算在各向异性材料结构中任意极化态电磁波传播遇到的困难,设计含磁光材料缺陷层的1维光子晶体。通过把入射电磁波按左旋圆偏振和右旋圆偏振进行正交分解的方法,推导出适合各向异性材料和任意极化态入射电磁波的传输矩阵算法。结果表明,该算法可以确定1维层状结构透射波和反射波偏振态的变化。     

用亚波长正弦介质光栅设计1/4波片

采用扩展边界条件法,得出亚波长正弦介质光栅正入射反射型1/4波片的结构参数。发现在一定精度范围内TE波与TM波的相位差能够在一段较大的槽深区域满足设计要求,从而降低了实际控制刻蚀深度的难度。讨论了线偏振光转化为圆偏振光的方位角问题。     

An analysis of intersecting diffused channel waveguides

The coupling characteristics of intersecting diffused channel waveguides are computed for realistic three-dimensional diffusion profiles by means of the propagating beam method (PBM). Both TE and TM polarizations are treated for waveguides formed onz-cut LiNbO3. Good agreement between computed and previously reported measured results is found for the TE polarization. Agreement between computed and measured results is not as good for the TM polarization. This is explained by the fact that the applicable2Deltan-waveguide supports four modes, which should make coupling characteristics very sensitive to input conditions.     

Simulation of polarization converter formed by poling-inducedpolymer waveguides

A polarization converter using electrooptic (EO) polymer waveguides is proposed and it is simulated by a full vectorial beam propagation method (VBPM) for anisotropic medium. First, an efficient structure of poling electrodes is proposed for the fabrication of TE-mode poling-induced waveguides in EO polymer. For given electrode structures of both TE-mode and TM-mode waveguides, poling-induced dielectric tensors are calculated by the finite-element method to provide refractive index distribution, data for VBPM simulation. It is shown numerically that the poled TE and TM mode waveguides work efficiently as the corresponding polarization filters. Then, new poling electrodes are suggested to fabricate a waveguide device formed by connecting the TE and TM mode waveguides adiabatically with a slowly varying structure. This waveguide device has the optic axis slowly rotating as one moves along the propagation direction, so that it will act as polarization converter. VBPM simulation shows that the polarization of the guided mode rotates following the optic axis distribution. Polarization conversion is demonstrated successfully with high conversion efficiency and low excess loss     

Integrated-Optic Polarization Controlling Devices Using Electro-Optic Polymers

Integrated-optic polarization controlling devices such as polarizers, polarization splitters, and polarization converters, are proposed and demonstrated in nonlinear optic polymers. Poling-induced birefringence in electro-optic polymers is exploited to fabricate the devices. The polymeric waveguide polarizers show low excess losses, and extinction ratios of 20.7 dB and 17.1 dB for TM-pass and TE-pass polarizers, respectively. The polymeric waveguide polarization splitters exhibit TE-TM mode splittings with crosstalk of 14.2 dB and 10.1 dB for TM and TE mode splittings, respectively. The polymeric waveguide polarization converters show successful TE/TM polarization mode conversion with conversion efficiencies of higher than 30 dB. The device employs poling-induced waveguides which have slowly rotating azimuth angle of optic axis along the light propagation direction. The novel polarization converter is insensitive to wavelength and easier to fabricate than the other polarization converters containing periodic structures.     

电磁波在等离子体中的传播衰减

针对通信黑障的问题,文中从电磁波在等离子体中的传播特性出发,利用Matlab数值仿真,研究不同电磁波频段,不同等离子体参数,包括等离子频率、碰撞频率、等离子温度、压强等对电磁波传播衰减的影响,以及外加磁场作用下,不同极化的电磁波在等离子体层的传播衰减特性。研究结果表明:外加磁场可明显降低圆极化电磁波衰减,并且当外加磁场满足一定条件,大于最小磁场强度时,电磁波衰减小于10 dB;且同等条件下右旋极化比左旋极化电磁波的衰减更小,为了获得较小的电磁波衰减,右旋极化电磁波所需的磁场强度也小于左旋极化。     

Electrooptic guided-to-unguided mode converter

Experimental demonstration of electrooptic polarization conversion from a guided TE wave to an unguided TM wave in a thin-film light guide is reported. In the specific device we fabricated utilizing Ta2O5film and LiTaO3substrate, we have observed a 40-percent modulation when 500 V were applied across two electrodes spaced 50 μm apart. We present here a ray-optics analysis of the conversion process. With the inclusion of the Goos-Haenchen shifts, the analysis agrees well with the experiment.