asymmetrical optical - UiTM Institutional Repository

UNIVERSITI TEKNOLOGI MARA

1><N

SYMMETRICAL AND ASYMMETRICAL OPTICAL PLANAR WAVEGUIDES COUPLERS

NOR SYAFIQAH MOHAMED KASSIM

Thesis submitted in

fulfillment of

the requirements

for

the degree

of

Master of

Science

Faculty of Applied

Sciences

October 2012

AUTHOR’S DECLARATION

I declare mm the work in this thesis was carried cm in accordance with the regulations

of

Universifi Teknologi MARA. It is original and is the result

of

my own work, ^unless otherwise indicated or acknowledged as referenced work. This thesis has not been submitted to any other academic institution or non-academic institution for any degree or qualification.

I, hereby, acknowledge that I have been supplied with the Academic Rules and Regulations for Post Graduate, Universiii Teknologi MARA, regulating the conduct

of

my study and research.

Name

of

Student : Nor Syafiqah Mohamed Kassim

Student

ID.

No. : 2008533447

Programme : Master

of

Science (Research)

Faculty : Applied Sciences

Thesis Title : 1><N Symme‘rical and Asymmetrical Optical Planar Waveguides Couplers

Signature

of

Student

EWU‘N

I

Date : October 2012

ABSTRACT

1><N symmetrical and asymmetrical couplers based-on highly multimode planar

waveguide have been designed, simulated, fabricated and characterized. Highly multimode waveguide has wide panential application in home-network applications, automotive wiring such as entertainment devices in car and sensors application. In this research work, 1X2 and 1X4 symmetrical waveguide coupler were utilized symmetry Y-junction design to obtain symmetric splitting ratio. Meanwhile, 1X2 asymmetrical waveguide coupler were developed using different technique to obtain asymmetrical ratios. The transmission chmc’cefistics were simulated using non- sequential ray-tracing technique. The devices have cross-section area

of

1 mm X1 mm were fabricated on transparent acrylic substrates. Two different waveguides have been used as a core that is highly transparent adhesive polymer and hollow metal-based waveguide. The hollow waveguide structure was coated with GO—nm-thick reflective layer to enhance reflectivity in the waveguide channel. The design

of

1X2 tap-off Y- junction waveguide coupler utilized changing the width

of

the branching waveguides to obtain asymmetric branching ratios. The simulation result gives excess loss from 0.223 dB 11: 0.528 dB with van'ous tap-width

of

0.05 mm m 0.95 mm with 0.05 mm interval. The output coupling ratios have been designed in ^{the range}

of

1% to 99%.

A

novel design

of

asymmetric hollow shifi-port Y-junction waveguide coupler was proposed. This Y-junction simply utilizes the technique

of

shifiing the axis

of

the

m

of

the output port so that the required power-splitting ratio can be obtained. The waveguide splits the output power asymmetrically in the range

of

93% to 7% with

8%

splitting-ratio muracy. The measured insertion loss at the shifi-port hasa minimum value

of

4.00 to a maximum

of

15.62 dB for 0.00 to 0.90 mm shifiing

of

the axis respectively. While the measured optical excess loss at the shifi-port varies from 2.06 to 4.32 dB. Another new asymmetrical waveguide coupler design which is hollow shifi-axis has been presented. The strumn’e with a series

of

patterns having shified axis (Ax) from 0.1 mm to 0.9 mm have been designed. The center axis

of

the taper waveguide and the branching output mm were adjusted in a straight line to obtain an asymmetrical branching ratio. By shifiing Ax from 0.1 to 0.9 mm, the brancMng ratio can be obtained in the range from 1% to 99% by experiment. The measured insertion loss at the shift—axis has a minimum value

of

5.21 dB toa maximum

of

27.36 dB for 0.1 to 0.9 mm shifting

of

the axis respectively. While the measured optical excess loss at the shifi-axis varies from 5.18 to 10.58 dB.

iii

TABLE OF CONTENTS

AUTHOR’S DECLARATION ABSTRACT

ACKNOWLEDGEMENT

TABLE

OF CONTENTS

LIST

OF TABLES

LIST

OF FIGURES

LIST

OF SYMBOLS

CHAPTER ONE: INTRODUCTION

1.1

1.2 1.3 1.4 1.5 1.6

Research Background Problem Statement Research Objectives Significance

of

Study Scope

of

Research Work Content

of

Thesis

CHAPTER TWO: THEORY OF OPTICAL WAVEGUIDE 2.1

22

23

Introduction Optical Waveguide 2.2.]

2.22 2.2.3 2.2.4 2.2.5 2.2.6

Introduction

Electromagnetic Analysis

of

the Plana: Waveguide Geometry

of

Waveguides

Polymer Waveguide Hollow Waveguide Rectangular Waveguides Optical Fiber

2.3.1 2.3.2

Multimode Fiber Polymer Optical Fiber (POF) 2.3.2.1 Advantages

2.332

Coupling Light Into Multimode Planar Waveguides

A-bwwu.‘

2.4 Multimode Optical Couplers 2.4.1 1X2 Symmetry Coupler 2.4.2 1><2 Asymmetry Coupler

CHAPTER THREE: METHODOLOGY 3.1

3.2

3.3 3.4 35

Introduction Couplers Fabrication

3.2.1 Polymer Y-Junction Coupler 3.2.2 Hollow Metal-Based Y-Junction Coupler Experimental Set Up

of

Y-junction Waveguide Coupler Non-Sequential Ray Tracing

Flow Chart

3.5.1 Presentation Flow

of

Experimental Results and Discussion

CHAPTER FOUR:

lXN

SYMMETRICAL WAVEGUIDE COUPLERS 4.1

4.2

4.3

Introduction

1X2 Symmetrical Waveguide Coupler 4.2.1 1X2 Polymer Y-Junction Coupler

4.2.”

Simulation and Experiment

of

1X2 Polymer Y-Junction Coupler

4.2.1.2 Results and Discussion

of

1X2 Polymer Y-Junction Coupler

4.2.2 V-shaped Tip Y—j unction Waveguide Coupler 4.2.2.1 Simulation

of

V-shaped Tip Waveguide Coupler 4.2.2.2 Results and Discussion

of

V-shaped Tip

Y-junction Waveguide Coupler 4.2.3 1X2 Hollow Metal-Based Y-Junction Coupler

4.2.3.1 Simulation and Experiment

of

¹ X2 Symmetrical Hollow Metal-Bassd Y-Junction Coupler 4.2.32 Results and Discussion

of

1X2 Symmetrical Hollow

Metal-Based Y-Junction Coupler 4.2.4 Summary

of

1X2 Symmetrical Waveguide Coupler 1X4 Symmetrical Waveguide Coupler

4.3.1 1X4

Pomer

Y-Junction Coupler

22 23 26

30 31 3s 3s 40 41 43 45

46 46 48 49

51

58 59 6]

63 64

64

70 70 73

vi