Luận án tiến sĩ: Thiết kế và mô phỏng mạch tích hợp quang băng rộng đa mode - Tran Tuan Anh (HUST, 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 DOCTORAL DISSERTATION IN TELECOMMUNICATIONS ENGINEERING HANOI – 2020 luan an 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. TRAN DUC HAN DR. TRUONG CAO DUNG HANOI – 2020 luan an 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.

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, October, 2020 Postgraduate Student Tran Tuan Anh SUPERVISORS SUPERVISOR 1 SUPERVISOR 2 i luan an Acknowledgment First and foremost, I would like to thank my supervisor Prof.

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. 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 luan an Table of Contents INTRODUCTION ________________________________________________________ 1 CHAPTER 1. SOI WAVEGUIDE STRUCTURE, ANALYSIS AND FABRICATION __ 8 1.1 Shapes and functions of silicon-on-insulator waveguide ___________________________8 1.2 Optical waveguide analysis and simulation methods ____________________________12 1.2 Effective index method ___________________________________________ 15 1.3 Finite difference method __________________________________________ 17 1.4 Beam propagation method _________________________________________ 18 1.5 Finite difference beam propagation method ___________________________ 19 1.3 Silicon-on-insulator waveguide fabrication ____________________________________21 1.1 Separation by implanted oxygen (SIMOX) ____________________________ 21 1.2 Bond and Etch-back SOI (BESOI) __________________________________ 23 1.4 Silicon Epitaxial Growth __________________________________________ 25 1.5 Fabrication of surface etched features ________________________________ 25 1.4 Silicon-on-insulator waveguide structure used for MDM functionality _____________28 1.3 Asymmetric Y-junction waveguide. MODE DIVISION MULTIPLEXER BASED ON ASYMMETRIC DIRECTIONAL COUPLER _______________________________________________ 44 2.1 Two mode division (De)multiplexer based on an MZI asymmetric silicon waveguide _45 2.1 Design and structural optimization __________________________________ 45 2.2 Simulation and performance analysis ________________________________ 49 2.1 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 3.1 Design and structural optimization __________________________________ 56 3.2 Simulation and performance analysis ________________________________ 64 3.

MODE DIVISION MULTIPLEXER BASED ON TILT BRANCHED BUS STRUCTURE SILICON WAVEGUIDE.1 Three-mode multiplexed device based on tilt branched bus structure using silicon waveguide __________________________________________________________________70 4.1 Design and structural optimization __________________________________ 70 4.2 Simulation and performance analysis ________________________________ 74 iii luan an 4.2 Four-mode multiplexed device based on tilt branched bus structure using silicon waveguide __________________________________________________________________78 4.1 Design and structural optimization __________________________________ 78 4.2 Simulation and performance analysis ________________________________ 83 4.3 Proposal of experimental diagram ___________________________________ 85 4.3 Conclusion _______________________________________________________________89 DISSERTATION CONCLUSION AND FUTURE WORKS _____________________ 92 PUBLICATIONS DURING PHD COURSE __________________________________ 94 UNDER REVIEW PAPER ________________________________________________ 94 PUBLICATIONS BEFORE PHD COURSE __________________________________ 94 REFERENCE __________________________________________________________ 95 iv luan an 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 luan an 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 luan an List of Tables Table 1.1 Summary of different MMI types’ properties .1 Comparison of our proposed designs based on ADC with others designs having similar structure.1 Comparison of our proposed designs based on MMI with others designs having similar structure.1 Comparison of our proposed designs based on branch bus structure with others designs having similar structure. 90 vii luan an List of Figures Fig 1. Set up initial parameters of SOI waveguide and simulation method in RSoft 4 Fig 2. Pathway monitoring power at each output port of a design .1 Schematic of non-planar optical waveguides.

High index is indicated by darker color.2 Schematic of SOI waveguide .3 Schematic of SOI Rib waveguide .1 Scheme of the effective index method for solving the propagation constant of a step-index channel waveguide. Starting from a 2D waveguide, the problem is split into two step-index planar waveguides .2 The cross-section of the waveguide is made discrete with a rectangular grid of points which have identical spacing.3 Comparison between FD-BPM (left) and FFT-BPM (right) simulation. FD-BPM under TBC gives better simulation result as the simulated wave is smoother .4 Comparison between FD-BPM simulation time depending on computed step of grid size 0.05μm (a) verse grid size 0.1 Variation of the oxygen profile during the SIMOX process. (a) Low-dose; (b) high-dose (peak is at the stoichiometric limit for SiO2); and (c) after implantation and annealing at 1300oC for several hours .2 The bond and etch-back process to form BESOI: (a) oxidation; (b) bonding; and (c) thinning.

(b) A second wafer is bonded to the first as in the BESOI process. (c) Thermal processing splits the implanted wafer at a point consistent with the range of the hydrogen ions .4 (a) Schematic of a silicon rib waveguide. (b) Electron micrograph of a silicon rib waveguide. Reproduced by permission of Intel Corporation .5 Schematic of a confined AC-generated plasma suitable for silicon processing.

The processed wafer in placed on the lower, grounded electrode .1 Directional coupler consisting of slab optical waveguide .2 Periodic exchange of power between waveguide 1 and 2 .3 Simulation of periodic exchange of power between waveguide 1 and 2 using BPM .4 Power transfer ratio verse phase mismatch parameter ∆𝛽𝐿𝑜 .5 The schematic configuration of MMI waveguide .6 Two-dimensional representation of a MMI waveguide .7 Power distribution of GI-MMI with 𝐿 = 3𝐿𝜋 (left), 𝐿 = 3𝐿𝜋/2 (middle), 𝐿 = 3𝐿𝜋/3 (right) using FD-BPM simulation. 38 viii luan an Fig 1.8 Power distribution of 2x2 PI-MMI, input access waveguide is at ±𝑊/6 with 𝐿 = 𝐿𝜋/2 (left), 𝐿 = 𝐿𝜋 (right) using FD-BPM simulation.9 Power distribution of SI-MMI showing 1-to-3-way splitting (left) and 1- to-1 imaging (right) having same length and different width using FD-BPM simulation.10 Oscillating field pass through boundary between two isotropic media .11 Schematic structure of tilt branch bus waveguide .1 Schematic of the mode synthesizer based silicon waveguide.2 BPM simulation for the height of waveguides of the asymmetric directional .3 BPM simulation for power ratio as a function of the waveguide height.4 Transmission characteristic of on dependence of the coupling length of the asymmetric directional coupler by BPM simulation. Electric field patterns for the mode (de)MUXer.6 Wavelength response of the mode DMUXer in the C-band.7 1-nm-wavelength spectrum in the side of mode multiplexer.8 Crosstalk of the modes in the structure for MUXer and deMUXer devices as a function of the etched depth tolerance: H=h1=500 nm.9 Sidewall roughness loss calculation for two modes and two polarization states of the waveguide in two cases: a) σ = 2 nm, Lcor = 50 µm and b) σ = 0.1 Schematic of cascade NxN GI MMI used for switching optical signal….1 Proposed schematic of a three mode (de)multiplexer based on a trident coupler and two multimode interference couplers on the platform of silicon on insulator waveguides.2 Schematic diagram and transmittance properties of the trident coupler: a) schematic diagram and b) BPM simulation for transmittance properties of the trident coupler as a function of the length of the sinusoidal .3 BPM simulation for the phase angle Φ is a function of the central width of the phase shifter.4 Electric field patterns of the proposed three - mode (de)MUXer for: fundamental mode (a), first-order mode (b), second-order mode (c), and total of three modes (d).5 Performances dependence on the wavelength of the proposed three mode- (de)MUXer: (a) insertion loss and (b) crosstalk.6 Influence of branching angles of the trident coupler on optical performances of the proposed (de)MUXer: a) insertion loss, and b) crosstalk.7 Fabrication tolerances of the proposed (de)MUXer: a) length tolerance of the second MMI coupler LMMI2, and b) width tolerance of the input width W0.8 Insertion loss and crosstalk in the proposed structure for three mode - (de)MUXer device as functions of the etched depth tolerance. 1 The proposed design of the three-mode channel separation device.

71 ix luan an Fig 4.2 Dependence of effective index of the main bus waveguide on variation of the main waveguide width Wm at the height h of 220 nm .3 The results of transmission characteristic of proposed device at the first tilted waveguide as a function of the width Wa (nm), which passively affects the mode selective coupling coefficients.4 The results of transmission characteristic of proposed device at the second tilted waveguide as a function of the width Wa (nm), which passively affects the mode selective coupling coefficients.5 Simulated electric field patterns for the proposed three mode (de)multiplexer for: fundamental mode (a), first-order mode (b), second-order mode (c).6 The characteristic optical performance of the device depends on the wavelength, showing the I.T of each three mode outputs.7 Variation of optical transmission performance of the proposed waveguide depended on width tolerance ΔW (nm).8 Variation of optical transmission performance of the proposed waveguide depended on height tolerance Δh (nm).