Design of novel power splitters by directional coupling between photonic crystal waveguides

The design of a novel photonic crystal waveguide power splitter is presented. The proposed power splitter has three output ports, the coupling among three parallel photonic crystal waveguides can be considered as a multimode interference (MMI), and the positions of output waveguides are determined by those of twofold images which are formed by the self-imaging effect of multimode interference. The transmission characteristics of the splitter are investigated by using the finite-difference time domain (FDTD) and the plane wave expansion method. The output optical power in each port can be controlled by adjusting the radius of the dielectric rods in the coupling region, and the coupling effect among output ports is decreased by using the T-shaped output port. The results indicate that 1× 1, 1×2 and 1×3 type power splitters can be realized when the normalized radius of dielectric rods in the coupling region is 0.130, 0.180, 0.152 or 0.221, respectively.     

Theoretical Investigation of Polarization-Insensitive Multimode Interference Splitters on Silicon-on-Insulator

An ultracompact polarization-insensitive 1times2 multimode interference (MMI) splitter based on silicon-on-insulator is investigated theoretically. The impact of the insulator index on the size of the MMI and the polarization-dependent performance is analyzed. A polarization-insensitive 1times2 MMI splitter of 4 mum by 16.5 mum is shown as an example. Relaxed tolerances on MMI width (> plusmn100 nm) and length (> plusmn0.7 mum) are obtained for both polarizations while the polarization differential loss is kept in range of 0.1 dB and its excess loss is kept below 0.5 dB. In addition, a wide operation wavelength window of 150 nm is obtained for both polarizations as well.     

General matrix theory of self-imaging in multimode interference(MMI) couplers

We present a simple and very general matrix method for predicting the properties of integrated optical multimode interference (MMI) couplers with single-mode input and output guides. We derive a set of N×N matrices which (in the paraxial limit) can be used to predict the complex mode amplitudes in the output guides from the complex mode amplitudes in the input guides for any type of MMI coupler, splitter or recombiner. We compare this theory with experiment for an 11×11 nonuniform coupler     

An InP-based optical multiplexer for 100-GHz pulse-train generation

A 100-GHz optical pulse train is generated using an InP-based optical multiplexer. This device is based on a waveguide array with five paths of different lengths separated by a 10-ps propagation time. We used a multimode interference (MMI) splitter at the input and a taper-type combiner at the output. This device is well-suited for optical time-division multiplexing (OTDM) applications     

A 12-channel phased-array wavelength multiplexer with multimodeinterference couplers

A compact 12-channel phased-array wavelength-division multiplexer based on multimode interference (MMI) couplers and useful for application with multiwavelength lasers is proposed. A suitably-chosen 1×12 MMI nonuniform power splitter is used to suppress the sidelobes of the multiplexer spectral response. Simulated results for the multiplexer designed in an InP-InGaAsP rib waveguide system and with 1-nm channel spacing at a wavelength of 1550 nm are presented. The multiplexer has a length of 3.2 mm and an insertion loss of 1.7 dB     

1.55μm SiGe 2×3光开关

利用多模干涉效应和自由载流子等离子体色散效应设计和模拟了基于1.55μm波长的2×3 SiGe光开关.该光开关由两个单模输入端口、一个多模干涉区和三个单模输出端口构成.在多模干涉区,设有两个折射率调制区,可以利用来把从两个输入端口输入的光信号分别从三个输出端口输出.束传播法分析结果表明,该光开关的传输损耗小于1.43dB,串扰在-18～-32.8dB之间.     

一种基于多模干涉耦合器的集成光开关研制

设计并制作了一种采用InP/InGaAsP材料的2×2基于多模干涉(MMI)器的Mach-Zehnder干涉仪(MZI)光开关,用三维有限差分束传播法(3D-BPM)对器件进行了优化设计与模拟分析。开关端口设计为单模波导且对偏振不敏感,采用电流注入调制相移区折射率,当折射率的改变引起π相位差时实现开关状态转换。测试结果表明,当注入电流达到43 mA时光信号从交叉端口交换到直通端口,开和关状态的串扰分别为-19.2 dB和-14.3 dB。     

1×3多模干涉型光功分器的研究

本文采用导模传输分析法,在GaAs/GaAlAs单异质结外延材料上设计了1×3MMI（多模干涉）型光功分器。根据所确定的器件结构参数,结合器件设计和制作过程中可能遇到的因素,详细分析了器件中自映像效应多模波导的宽度和长度、输入单模波导的宽度等结构参数对器件性能的影响。本文基于RSoft软件,对所设计的器件结构参量进行了仿真。模拟结果表明,所设计的器件实现了1×3光功分器功能,具有插入损耗低和均匀性好的特点。     

Tunable multimode interference coupler

An electrically tunable multimode interference (MMI) coupler/splitter is demonstrated. The device operates by modifying the phase of the multiple self-images that are formed around the midpoint of the MMI structure. This provides a simple way to fine-tune the 50:50 output power split ratio or other arbitrary ratio.     

基于多模干涉光子晶体波导1×4超紧凑分束器

本文基于自成像效应的波导多模耦合,提出并且数值计算了一种1×4超紧凑分束器。将七光子晶体单模波导的相互耦合看成一个多模干涉系统,当入射波长λ=1．55μm时,这种分束器耦合区的长度只有3．92μm。通过调节耦合区介质柱半径R,来改变耦合区电磁场的相位分布,从而控制四个输出端口的能量分布。这种分束器在光子晶体集成电路中具...     

Analysis of generalized Mach-Zehnder interferometers forvariable-ratio power splitting and optimized switching

The nonideal integrated optical N×N generalized Mach-Zehnder interferometer (GMZI) employing multimode interference (MMI) couplers is analyzed using transfer matrix techniques. Deviations in the phase relations and the power splitting ratio of the MMI couplers are included in the theory, along with the effects of phase errors in the interferometer arms. The predictions of the theory are compared to the response of a 4×4 GMZI which has been fabricated. The device is operated as both a variable-ratio power splitter and a switch by compensating for the phase errors in the interferometer arms, but the performance is ultimately limited by the nonideal imaging in the MMI couplers. The practicality of these applications is investigated by performing a tolerance analysis for the operation of 1×N power splitters and switches for N up to 10     

2×2 InP/InGaAsP MMI-MZI型光开关设计与实验

主要研究基于多模干涉耦合器(MMI)的2×2 InP/InGaAsP马赫曾德型(MMI-MZI)光开关.开关的特性采用BPM(光束传输法)进行器件建模、参数分析与性能优化.开关的结构按照传输波导保证单模传输、低偏振敏感要求进行了设计.光开关通过载流子电注入产生的载流子吸收和带填充效应改变移相臂传输光相位.实验测得光开关在控制电压为6.4 V时可实现交叉态到直通态的倒换,开关和关态串扰分别为-20.49 dB、-19.19 dB.这种开关具有结构紧凑、制作容差大和偏振无敏感等优点,它可以很方便地和其它半导体有源器件集成,在未来DWDM系统中有着非常广泛的应用前景.     

Design and performance evaluation of 1-by-64 multimode interferencepower splitter for optical communications

A 1-by-64 multimode interference power splitter in SiO₂ has been designed for use in fiber-optics communication systems. The splitter exhibits a minimum loss of 0.5 db and a uniformity of 1.7 dB at a wavelength of 1.55 μm. The polarization sensitivity is below 0.14 dB, the reflection level below -55 dB, and the optical bandwidth 30 nm. The fabrication tolerances are ±0.1 mm on the length and ±3.5 μm on the width of the multimode section of the splitter. In comparison with a branching-type splitter it is found that the designed device is approximately 30% shorter than the branching-type device for comparable losses     

Board-level optical-to-electrical signal distribution at 10 gb/s

An opto/electrical prototype for on-board optical-to-electrical signal broadcasting operating at 10 Gb/s per channel over an interconnect distance of 10 cm is demonstrated. An improved 1/spl times/4 multimode interference (MMI) splitter at 1550 nm with linearly tapered output facet is heterogeneously integrated with four p-i-n photodetectors (PDs) on a silicon (Si) bench. The Si bench itself is hybrid integrated onto an FR-4 printed-circuit board with four receiver channels. A novel fabrication/integration approach demonstrates the simultaneous alignment between the four waveguides and the four PDs during the MMI fabrication process. The entire system is fully functional at 10 Gb/s.     

硅基槽波导级联多模干涉耦合器型偏振分束器

提出了一种基于硅基槽波导的级联多模干涉(MMI)耦合器型偏振分束器,由锥形及矩形结构MMI耦合器构成.级联结构使器件长度无需为两偏振模自镜像长度的公倍数,不仅能有效减小器件尺寸,而且提高设计灵活性.同时,利用槽波导的高双折射特性及MMI耦合器的锥形结构,可进一步缩短器件尺寸.分析结果表明,所提器件能够有效实现偏振束分离,两级MMI工作区总长度仅为42μm,准TE与准TM模的偏振消光比分别为29.8和31.4d B,1.55μm波长下的插入损耗分别为0.395和0.699 d B,偏振消光比大于20 d B时光带宽为43 nm,覆盖整个C波段.最后,详细分析了器件关键参数的制造误差对器件性能的影响.     

Wideband Criterion for Multimode Interference Splitters

A wideband criterion for multimode interference (MMI) splitter is proposed. The basic principle is based on reducing the interference length difference and making it shorter than the spot size for constructive mode interference. Simulation results show the spectra of proposed MMI splitter is wide enough (1.26-1.70 mum) to cover the fiber communication band and the size of the splitter is more compact than that of the conventional MMI or Y-branch splitter     

质子交换铌酸锂波导MMI光功分器

利用三维非旁轴近似光束传输法对退火质子交换铌酸锂渐变折射率分布波导中的自镜像效应进行分析与模拟.在此基础上,利用退火质子交换技术在X切Y传铌酸锂衬底上进一步制作了1×8 MMI光功分器.测试表明器件实现了1路分成8路的光功分功能.     

可调谐高分子MMI光波导功率分配器的研究

设计了一种基于多模干涉(MMI)波导结构的可调谐功率分配器,利用高分子含氟聚酰亚氨材料的热光效应,调节多模波导中局部区域的折射率,可实现两单模输出导模的输出功率比在较大范围内连续可调谐.BPM防真证实了这一结果.     

Design and fabrication of a significantly shortened multimode interference coupler for polarization splitter application

We report that we have successfully designed and fabricated a significantly shortened multimode interference coupler for application in polarization splitter, using a phenomenon that we termed "quasi-state" (QS) imaging effect. First, we identified and analyzed the QS imaging effect, and, based on the QS analysis, designed and fabricated a novel multimode interference (MMI) device with its split length shortened to 1/5 of a normally designed MMI split length. The fabrication is simple and cost effective and the fabricated device shows outstanding characteristics in extinction ratio, signal homogeneity, excess loss, and tolerance in the length of the splitter.     

基于MMI滤波器的可调谐连续光全光纤OPO

在连续光全光纤光学参量振荡器（FOPO）中,目前主要利用可调滤波器（TBPF）等高插入损耗的滤波器件进行边带光输出波长的调谐,这种方式所引起的高环形腔损耗限制了FOPO输出性能的进一步提升。为解决此问题,提出了基于多模干涉（MMI）滤波器的低腔损耗可调谐连续光FOPO。通过选取不同长度和纤芯尺寸的多模光纤制作级联单模-多模-单模光纤（SMS）作为滤波器件,使其在选定波长处的插入损耗小于1 dB,FOPO环形腔的总损耗不大于5 dB,并通过对SMS器件施加轴向拉力的方式调节滤波器件的透射谱,实现了1 494~1 501 nm和1 638~1 629 nm范围内的双边带可调谐连续光输出。