Design and simulation of wideband photonic intergrated circuits for multi mode (de) multiplexing and conversion

MINISTRY OF EDUCATION AND TRAINING HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY -0 TRAN TUAN ANH DESIGN AND SIMULATION OF WIDEBAND PHOTONIC INTEGRATED CIRCUITS FOR MULTI-MODE (DE)MULTIPLEXING AND CONVERSION DOCTORAL DISSERTATION IN TELECOMMUNICATIONS ENGINEERING HANOI – 2020 MINISTRY OF EDUCATION AND TRAINING HANOI UNIVERSITY OF SCIENCE AND TECHNOLOGY -0 TRAN TUAN ANH DESIGN AND SIMULATION OF WIDEBAND PHOTONIC INTEGRATED CIRCUITS FOR MULTI-MODE (DE)MULTIPLEXING AND CONVERSION Major: Telecommunications Engineering Code: 9520208 DOCTORAL DISSERTATION IN TELECOMMUNICATIONS ENGINEERING SUPERVISORS: PROF DR TRAN DUC HAN DR TRUONG CAO DUNG HANOI – 2020 DECLARATION OF AUTHORSHIP I, Tran Tuan Anh, declare that this dissertation entitled, "Design and simulation of wideband photonic integrated circuits for multi-mode (de)multiplexing and conversion", and the work presented in it is my own I confirm that: - This work was done wholly or mainly while in candidature for a Ph.D research degree at Hanoi University of Science and Technology - Where any part of this dissertation has previously been submitted for a degree or any other qualification at Hanoi University of Science and Technology or any other institution, this has been clearly stated - Where I have consulted the published work of others, this is always clearly attributed -Where I have quoted from the work of others, the source is always given - With the exception of such quotations, this dissertation is entirely my own work - I have acknowledged all main sources of help Where the dissertation is based on work done by myself jointly with others, I have made exactly what was done by others and what I have contributed myself Hanoi, December, 2020 Postgraduate Student Tran Tuan Anh SUPERVISORS SUPERVISOR SUPERVISOR i Acknowledgment First and foremost, I would like to thank my supervisor Prof Dr Tran Duc Han for his support and advice throughout my research time in Hanoi University of Science and Technology (HUST) His encouragement and full support led me to every success of my study I have been able to learn a lot from him about being a good teacher and researcher I would like to express my gratitude to my supervisor, Dr Truong Cao Dung, for guiding and motivating me since I was an undergraduate student at HUST He has given me the very first guidance until I finished my doctoral dissertation I special thanks to Prof Dr Vu Van Yem for his constant help during my study postgraduate courses and sincere advices for my future career I am also thankful to my research team, Ms Nguyen Thi Hang Duy, Mr Ta Duy Hai, Ms Tran Thi Thanh Thuy and Mr Hoang Do Khoi Nguyen in Posts and Telecommunications Institute of Technology They gave me a lot of help during my last two years Finally, I would like to express my grateful thanks to my parents, Mr Tran Quoc Hung and Mrs Tran Thi Huong, and my uncle, Mr Tran Quoc Dung, for their support and encouragement TRAN TUAN ANH ii Table of Contents INTRODUCTION CHAPTER SOI WAVEGUIDE STRUCTURE, ANALYSIS AND FABRICATION 1.1 Shapes and functions of silicon-on-insulator waveguide _8 1.2 Optical waveguide analysis and simulation methods 12 1.2.1 Wave equations _ 12 1.2.2 Effective index method _ 15 1.2.3 Finite Difference Method _ 17 1.2.4 Beam Propagation Method 18 1.2.5 Finite Difference Beam Propagation Method 19 1.3 Silicon-on-insulator waveguide fabrication 21 1.3.1 Separation by implanted oxygen (SIMOX) 21 1.3.2 Bond and Etch-back SOI (BESOI) 23 1.3.3 Wafer Splitting _ 24 1.3.4 Silicon Epitaxial Growth 25 1.3.5 Fabrication of surface etched features 25 1.4 Silicon-on-insulator waveguide structure used for MDM functionality _27 1.4.1 Directional coupler 27 1.4.2 Multimode interference _ 32 1.4.3 Asymmetric Y-junction waveguide _ 41 1.5 Conclusion _43 CHAPTER MODE DIVISION MULTIPLEXER BASED ON ASYMMETRIC DIRECTIONAL COUPLER _ 45 2.1 Two mode division (De)multiplexer based on an MZI asymmetric silicon waveguide _45 2.1.1 Design and structural optimization 45 2.1.2 Simulation and performance analysis 49 2.2 Conclusion _52 CHAPTER MODE DIVISION MULTIPLEXER BASED ON MULTIMODE INTERFERENCE COUPLER _ 54 3.1 Cascaded N x N general interference MMI analysis _54 3.2 Three-mode division (De)multiplexer based on a trident coupler and two cascaded 3×3 MMI silicon waveguides _56 3.2.1 Design and structural optimization 56 3.2.2 Simulation and performance analysis 64 3.3 Conclusion _68 CHAPTER MODE DIVISION MULTIPLEXER BASED ON TILT BRANCHED BUS STRUCTURE SILICON WAVEGUIDE 70 4.1 Three-mode multiplexed device based on tilt branched bus structure using silicon waveguide 70 4.1.1 Design and structural optimization 70 iii 4.1.2 Simulation and performance analysis 74 4.2 Four-mode multiplexed device based on tilt branched bus structure using silicon waveguide 78 4.2.1 Design and structural optimization 78 4.2.2 Simulation and performance analysis 83 4.2.3 Proposal of experimental diagram _ 85 4.3 Conclusion _89 DISSERTATION CONCLUSION AND FUTURE WORKS _ 92 PUBLICATIONS 94 UNDER REVIEW PAPER 94 REFERENCE 95 iv Abbreviation ADC Asymmetric Directional Coupler AON All Optical Network BESOI Bond and Etch-back SOI BER Bit Error Rate BPM Beam Propagation Method CMOS Complementary Metal Oxide Semiconductor Cr.T Cross talk CMP Chemical Mechanical Polishing CVD Chemical Vapor Deposition CWDM Coarse Wavelength Division Multiplexing DC Directional Coupler DWDM Dense Wavelength Division Multiplexing DUT Device Under Test DUV Deep Ultra Violet EBL Electron Beam Lithography EDFA Erbium Doped Fiber Amplifier EIM Effective Index Method EME Eigenmode Expansion EMS Eigenvalue Mode Solver FD-BPM Finite Difference Beam Propagation Method FDM Finite Difference Method FDTD Finite Difference Time Domain FFT-BPM Fast Fourier Transform Beam Propagation Method FTTH Fiber to the Home GI General Interference I.L Insertion Loss v LER Line Edge Roughness MDM Mode Division Multiplexing MMI Multimode Interference MPA Mode Propagation Analysis MZI Mach-Zehnder Interferometer OEICs Opto-electronic Integrated Circuits ONU Optical Network Unit OOK On-off Keying Signals PDM Polarization Division Multiplexing PECVD Plasma-enhanced chemical vapor deposition PICs Planar Integrated Circuits PMMA Polymethyl Methacrylate PLCs Planar Lightwave Circuits PON Passive Optical Network RI Restricted Interference SI Symmetric Interference SDM Spatial Mode Division Multiplexing SIMOX Separation by Implanted Oxygen SOI Silicon on Insulator TBC Transparent Boundary Condition TE Transverse Electric TEM Transverse Electromagnetic TM Transverse Magnetic WDM Wavelength Division Multiplexing XPM Cross Phase Modulation vi List of Mathematical Symbols nc Refractive effective index of cladding layer ns Refractive effective index of substrate layer nr Refractive effective index of core layer neff Effective refractive effective index cm Excitation coefficient of m-th order mode m m-th order mode LΠ Half beat coupling length LMMI Length of MMI Coupler NxM Matrix dimension with N and M W Width of waveguide h Height of waveguide Pin Input power Pout Output power N 1  Sum from to (N-1) of variable q m Propagation constant of m-th order mode  Operation wavelength in waveguide F x Differential equation of function F by variable x φ Phase Shifting (rad)  mn Uncoupled coefficients of m-th order mode at n-th order output port mn Coupled coefficients of m-th order mode at n-th order output port q 0 vii List of Tables Table 1.1 Pros and Cons of different materials used in fabricating PLCs devices Table 1.2 Summary of different MMI types’ properties 41 Table 2.1 Comparison of our proposed designs based on ADC with others designs having similar structure 53 Table 3.1 Comparison of our proposed designs based on MMI with others designs having similar structure 69 Table 4.1 Comparison of our proposed designs based on branch bus structure with others designs having similar structure 90 viii mixture of TE and TM polarization in the input signal will significantly degrade the optical performance of the device, which in turns limits the applications of SOI-based photonic circuits in optical communications To overcome this drawback, many structures for realizing polarization diversity schemes have been used, including polarization splitters [110], [111], polarization rotators [112], polarization-insensitive waveguides [113], TE/TM-passing polarizers [114]–[118], in order to achieve a transparent photonic integrated circuit Therefore, to enhance optical performances of proposed device, TE-pass polarizers need to be used before and after connecting with the device to refine TM polarization Compared to recent works such as Chunlei Sun et al [119] and Yunhong Ding et al [120], the proposed devices have the same performance and fabrication tolerance but their structure is less complex On the other hand, it is also the first time that designs, which can couple and convert some specific high-order modes from bus waveguide into non-fundamental mode in the branched waveguide following particular phase matching conditions, are introduced Criteria Number FP* M** Structure BW*** I.L Cr.T of mode Our (de)Mux proposed modes design Ref [34] (de)Mux modes Ref [36] (de)Mux modes Ref [89] (de)Mux modes 950μm x μm SOI 1200μm SOI x μm 1500nm1600nm >-1.3 dB -1.5 dB -0.03 dB -5.7 dB