Tapered Multimode Interference Combiners for Coherent Receivers

A new tapered multimode interference （MMl）-based coherent lightwave combiner is reported. A comprehensive theoretical analysis of mode behaviors in the tapered MMI waveguide is presented, and the output characteristics of the tapered MMI combiners with various structures are demonstrated. The combiner is fabricated on a silicon-on-insulator （SO1） substrate. Due to its advantages of having no end-facet reflection,easy extension to a multi-port configuration, high tolerance for fabrication errors, and compact size, the tapered MMI is a good candidate for a coherent lightwave combiner to be used in large-scale photonic integrated circuits.

An Efficient MMI SOI Splitter with Multimode Input/Output Waveguides

A 1×8 multimode interference power splitter with multimode input/output waveguides in SOI material is designed by the beam propagation method and fabricated by the inductive coupled plasma etching technology for use in fiber optics communication systems.The fabricated device exhibits low loss and good coupling uniformity.The excess loss is lower than 0 8dB,and the uniformity is 0 45dB at the wavelength of 1550nm.Moreover,the polarization dependent loss is lower than 0 7dB at 1550nm.The device size is only 2mm×10mm.

Semi-vectorial analysis of a compact wavelength demultiplexer based on the tapered multimode interference coupler

Based on a parabolically tapered multimode interference （MMI） coupler with a deep-etched SiO2/SiON rib waveguide, a compact wavelength demultiplexer operating at 1.30 and 1.55 μm wavelengths is proposed and analysed by using three-dimensional semi-vectorial finite-difference beam propagation method （3D-SV-FD-BPM）. The results show that a MMI section of 330.0 μm in length, which is only 76% length of a straight MMI coupler, is achieved with the contrasts of 42.3 and 39.2dB in quasi-TE mode, and 38.4 and 37.8dB in quasi-TM mode at wavelengths 1.30 and 1.55μm, respectively, and the insertion losses below 0.2dB at both wavelengths and in both polarization states, The alternating direction implicit algorithm with the Crank-Nicholson scheme is applied to the discretization of the 3D-SV-FD-BPM formulation along the longitudinal direction. Moreover, a modified FD scheme is constructed to approximate the resulting equations along the transverse directions, in which the discontinuities of the derivatives of magnetic field components Hy and Hx along the vertical and horizontal interfaces, respectively, are involved.

Two-Mode Converters at 1.3μm Based on Multimode Interference Couplers on InP Substrates

Two-mode converters at 1.3μm, aiming at applications in mode-division multiplexing in Ethernet systems, are proposed and experimentally demonstrated. Based on multimode interference couplers, the two-mode converters with 50% and 66% mode conversion efficiencies are designed and fabricated on InP substrates. AIode conver- sion from the fundamental mode （TEo） to the first order mode （TE1） is successfully demonstrated within the wavelength range of 1280-1320nm. The 1.3-μm mode converters should be important devices in mode-division multiplexing systems in Ethernet systems.

Unitary transformation of general nonoverlapping-image multimode interference couplers with any input and output ports

An explanation of optical unitary transformation is presented for general nonoverlapping-image multimode interference(MMI)couplers with any number of input and output ports.The light transformation in the MMI coupler can be considered as an optical field matrix acting on an input light column vector.We investigate the general phase principle of output light image.The complete proof of nonoverlapping-image MMI coupler’s optical unitarity along with the phase analysis of matrix element is provided.Based on a two-dimensional finite-difference time-domain(2 D-FDTD)simulation,the unitary transformation is obtained for a 4×4 nonoverlapping-image MMI coupler within a deviation of 4×10-2 for orthogonal invariance and 8×10-2 for transvection invariance in the C-band spectral range.A compact 1×4 splitter based on cascaded MMI coupler is proposed,showing a phase deviation less than 5.4°while maintaining a low-loss performance in C-band spectra.

Research Progress on Multimode Interference Switches

Optical switches are key components for constructing optical communication networks, so it is necessary to design optical switches and optical switch arrays with high performance and low cost. As one type of optical switches, the multimode interference（MMl） switches have received considerable attention due to their unique merits. The structures and operation principles of various types of MMI switches are introduced, and the recent progresses of MMI switches are also discussed.

All-fiber erbium-doped dissipative soliton laser with multimode interference based on saturable-reserve saturable hybrid optical switch

Reverse saturable absorption is essential for the realization of dissipative solitons.In this paper,we introduce reverse saturable absorption by using nonlinear multimode interference(NL-MMI),for the first time,to the best of our knowledge,and obtain a stable dissipative soliton operation.By adjusting the coupling efficiency from multimode fiber to single mode fiber,the absorption properties of NL-MMI can be switched between saturation and reverse saturation.The dissipative soliton can be obtained with pulse width of 975 fs in the experiment,the 3-dB bandwidth at 1555 nm is 16 nm,and the maximum output power is 11.48 m W.The nonlinear absorption optical modulation and high damage threshold characteristics of the NL-MMI based ultrafast optical switch provide a new idea for realizing dissipative solitons.

Temperature Dependence of Characteristics for Multimode Interference Based 3-dB Coupler in SOI

The temperature dependence of characteristics for multimode interference(MMI) based 3-dB coupler in silicon-on-insulator is analyzed, which originates from the relatively high thermo-optic coefficient of silicon. For restricted interference 3-dB MMI coupler, the output power uniformity is ideally 0 at room temperature and becomes 0.32 dB when temperature rises up to 550 K.For symmetric interference 3-dB MMI coupler, the power uniformity keeps ideally 0 due to its intrinsic symmetric interference mechanism. With the temperature rising, the excess loss of the both devices increases. The performance deterioration due to temperature variety is more obvious to restricted interference MMI 3-dB coupler, comparing with that of symmetric interference MMI 3-dB coupler.

Silicon-Based Mode Converter and Demultiplexer for Wavelength Division Multiplexing Transmission by Using Multimode Interference Couplers

We present a mode converter and demultiplexer structure for wavelength division multiplexing (WDM) transmission by employing multimode interference (MMI) on Silicon-on-Insulator (SOI) platform. The mode converter and demultiplexer have a compact size of less than 2.7 μm × 43.7 μm. Moreover, the crosstalk between neighboring wavelength channel within C band (1530 nm to 1570 nm) can be reduced by utilizing the tapered phase shifter cascaded with MMI. The simulated results indicate that this structure has a low insertion loss of less than 1 dB, a low crosstalk of better than ?15 dB and a relatively high fabrication tolerance of ~10 nm. Such structure may find many potential applications in silicon photonic integrated devices.

弱限制MMI型光功分器

本文采用导模数值计算法对MMI(多模干涉 )型光功分器SIE干涉区内的导模进行计算并对输出波导位置进行优化 ,证明在一定条件的弱限制下器件的插入损耗和输出均匀度均超过强限制的情况 ,说明MMI型光功分器的制作可以采用方便的湿法刻蚀 。

MMI阵列波导光栅复用/解复用器的研制

详细分析了基于自镜像效应的 MMI DMUX器件的基本工作原理 ,在此基础上 ,在 SOI材料上完成了对 8信道 MMI DMU X的具体设计 .该器件的输入、输出单模波导采用 Soref的大截面脊形光波导理论进行优化设计 ,最后获得了当输入、输出单模波导宽度为 5 μm,SIE多模波导宽度和长度分别为 72 μm和 6 313.4μm时 ,该器件对8信道波长的隔离度均在 35 d B以上 ,且理论传输损耗 <0 .18d B.

8-信道MMI阵列波导光栅复用/解复用器的研制(英文)

本文首先详细分析了基于自镜象效应的 MMI DMUX器件的基本工作原理 ,在此基础上 ,在 Ga As/Ga Al As系材料上完成了对 8信道 MMI DMUX的具体设计 .该器件的输入、输出单模波导和 SIE多模波导采用离散谱折射率法进行优化设计 ,最后获得了当输入、输出单模波导宽度为 3μm、SIE多模波导宽度和长度分别为 40 μm和 1 731 .45μm时 ,该器件对 8信道波长的隔离度为～ 2 6d B,理论传输损耗为～ 0 .2 4 d B.

Design and Fabrication of Ultracompact 3-dB MMI Coupler in Silicon-on-Insulator

An ultracompact 3 dB coupler is designed and fabricated in silicon on insulator,based on 1×2 line tapered multimode interference (MMI) coupler.Comparing with the conventional straight MMI coupler,the device is ～40% shorter in length.The device exhibits uniformity of 1 3dB and excess loss of 2 5dB.

用MMI实现的平顶型AWG的特性分析

引入归一化偏移和归一化间距,利用高斯近似得到阵列波导光栅(AWG)的频谱响应,从而分 析了展宽系数、品质因数、插损与归一化间距的关系。给出一个实例,取归一化间距为0.707,对应的展宽系数约为2,插入损耗IL约为2dB,并用光束传输方法(BPM)进行了验证。

渐变截面多模干涉器件中MMI区长度的计算

从渐变截面波导与强导近似的阶跃截面波导之间的区别入手 ,推导出了渐变截面MMI区长度的精确表达式 ,并对成像的振幅和相位关系进行了研究。结果表明 ,在相同MMI区宽度条件下 ,渐变截面器件中MMI区最短长度为阶跃截面的两倍 ,但它的设计灵活性却是阶跃截面器件所无法比拟的。

超紧凑型SOI基3×3 MMI波导光开关的优化设计

提出一种基于SOI材料的超紧凑型3×3 MMI波导光开关,开关仅有一个多模波导,且多模波导采用更为紧凑的双曲结构。用FD-BPM方法对其各个状态进行了模拟和分析,并对器件的结构参数进行了优化设计。结果表明,这种光开关可以成功实现任意两输入和输出通道间的开关功能,优化后的开关呈现优良的综合性能,且整个器件的尺寸小于4 mm。

MMI型GaAs 1×N和N×N集成光学开关的研制

设计了一种能直接与单模光纤阵列相耦合的多模干涉 (MMI)型光开关。给出了MMI型光开关各组成部分的工作原理 ,并用导模传输分析法 ,模拟了 1× 4MMI型光开关的四种不同的开关状态 ,在此基础上完成了 1× 4和 4× 4MMI型光开关的设计。最后根据所确定的器件结构参数 ,用有限差分光束传输法分析了器件结构参数对器件性能的影响。

MMI型1.31/1.55μmGaAs波分复用/解复用器的研制

利用多模波导的自镜像原理 ,分析设计了一种能直接与单模光纤相耦合的具有最小循环比的 1.31/ 1.55μm波长的GaAs/GaAlAs波分复用 /解复用器。该器件的输入、输出单模波导和SIE多模波导采用离散谱折射率法进行优化设计 ,最后获得了当输入、输出单模波导宽为 3μm、SIE多模波导宽度和最佳耦合长度分别为 18μm和 560 2 .8μm时 ,该器件对 1.31μm和 1.55μm两个波长的隔离度均在 70dB以上 ,且传输损耗小于 0 .1dB。

二维限制MMI耦合器自镜像特性(英文)

采用扩展的导模传输分析法 ,对二维限制多模干涉 (MMI)耦合器的自镜像效应进行分析 ,详细讨论了二维限制多模干涉耦合器的自镜像特性和在两个方向上各自都成完整像的要求 ,并用三维全矢量非旁轴近似光束传输法进一步验证了分析结果 结果表明 ,一维限制多模干涉耦合器的自镜像效应在一定条件下 ,可以拓展到二维限制多模干涉耦合器上 并且在强限制的波导结构中 ,二维自镜像效应可以看成二个相互垂直。

一般1×N的MMI成像位置和相位关系

根据多模干涉器 (MMI)的自映像原理 ,讨论了一般 1×N多模干涉器件的成像位置和相位关系 ,并用导模传输法验证了分析结果 。