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.     

Multimode interference-based photonic crystal waveguide power splitter

A compact power splitter based on the multimode interference (MMI) effect in photonic crystal waveguides is designed and analyzed. The device size reduction compared with the conventional MMI power splitter can be attributed to the large dispersion of the photonic crystal waveguides. The Massachusetts Institute of Technology Photonic-Bands code is used to calculate the band structures of photonic crystal waveguides. The finite-difference time-domain method is adopted to simulate the relevant structures.     

Optimal design of a multi-mode interference splitter based on SOI

In this paper, the multimode waveguide lengths and the output port locations of a SOI （silicon on insulator） material-based 1×4 MMI （multimode interference） optical splitter are optimized by means of FD-BPM （finite difference - beam propagation method）. An improved 1×4 MMI optical splitter is designed. Compared with an usual optical splitter, a smaller loss 0. 12dB and a better output port power uniformity 0.11dB are achieved for the optical signal transmission.     

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     

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.     

Shortened Polarization Beam Splitters With Two Cascaded Multimode Interference Sections

This letter presents a design for shortening the length of a polarization beam splitter (PBS) by using two cascaded multimode interference (MMI) sections with different widths. By optimizing the MMI parameters, a short PBS of good performance is achieved. The total length of the PBS is reduced to about 1/28 of that of a conventional design.      

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.     

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.     

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。     

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.     

Proposal for an Ultracompact Polarization-Beam Splitter Based on a Photonic-Crystal-Assisted Multimode Interference Coupler

An ultracompact polarization-beam splitter (PBS) combining a multimode interference (MMI) coupler and some photonic crystal (PC) structures is presented. The MMI coupler is designed to collect polarized powers reflected by or transmitted through an internal PC structure. The simulation result shows that the designed PBS is very short (about 50 mum), and has a low insertion loss, a high extinction ratio, and a broad bandwidth     

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.     

光敏杂化溶胶-凝胶法研制多模干涉波导分束器

采用有机/无机杂化溶胶-凝胶方法制备高质量的SiO2薄膜和光敏性薄膜材料;利用三维FD-BPM(finitedifference beam propagation method)研究了掩埋式和暴露式矩形波导结构多模干涉(MMI)型光功率分束器的主要性能,理论模拟发现,掩埋式矩形波导结构分束器的长度、宽度和厚度容差性都优于暴露式矩形波导结构的MMI型分束器,并且具有更宽的带宽特性。通过简单的紫外曝光、显影工艺制备了1×4 MMI型波导分束器,分束器在1 550 nm波长附近的插入损耗为8.1～8.8 dB,功率分束不均匀性小于1 dB。     

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     

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     

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.     

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.     

Parallel feed travelling wave distributed pin photodetectors withintegrated MMI couplers

The fabrication and performance of a parallel feed travelling wave photodetector with pin diodes operating at 1550 nm is presented. A parallel optical feed using an integrated multimode interference (MMI) power splitter helps increase the maximum linear photocurrent through a more uniform distribution of photocurrent. The maximum DC linear current measured is 52.2 mA. Maximum linear RF power at 10 GHz was 9 dBm     

Design and fabrication of the GaAs integrated optical chip for fiber optical gyroscope

An integrated optical chip for fiber optical gyroscope (FOG) is designed and fabricated on GaAs. To achieve a high modulation efficiency and a small chip size, a deeply etched waveguide structure is employed, and accordingly a multimode interference (MMI) coupler is used as the 1 × 2 power splitter. The size of the chip is about 8.5 mm × 0.5 mm, which is much smaller than that of LiNbO₃-based chips. The experimental results show that the extinction ratio (ER) of the TE mode to the TM mode is over 26 dB and the value of V _π·L of the phase modulators is 18 V · cm. The method to further lower V _π is discussed.