ATTENUATION MEASUREMENT ON CYCLOTENE

(BCB PHOTO RESIN) POLYMER BASED SLAB WAVEGUIDE

KESAVAN S/O ULAGANATHEN

A project report submitted in partial fulfillment of the requirements for the award of the

Degree of Master of Engineering (Electrical-Electronic&Telecommunication)

Faculty of Electrical Engineering

Universiti Teknologi Malaysia

MAC 2005

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Dedicated to my beloved supervisor, wife and my two sons

KABILAN & MUGILAN

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ACKNOWLEDGEMENTS

I would like to express deepest thanks to my supervisor, Associate Prof. Dr.

Norazan Kassim for his invaluable guidance, support and encouragement in the

completion of this project. Special thanks to Mr. Shi Yugang to be my working partner

throughout this project. Without them, this work would not have been possible.

I would like to wish appreciation to members of the research group, especially to

Mr. Hanif , Mr. Leow , Mr. Ahmad and Mr. Azrul for their support throughout this

project.

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ABSTRACT

Photonic switch /device are widely developed due to great requirement of all

optical based network. The photonic device can be further divided into active and

passive devices, in which for the former one, further light controlled using electric field

or temperature variation is the actual characteristic. In this project, investigation of the

thermo optic properties of the existing polymer in the photonic Lab was carried out. The

investigation included with the literature study on the possible ways for characterizing

both properties and further an experimental set-up was included in this project. Study on

the attenuation and losses of light wave when it travels through polymer slab was

introduced. An experimental set-up to identity the best technique to launch the light

source into the wave guide by comparing the other method been done. New improved

technique of the launching the light source into the fiber slab was introduced with taking

into the account of attenuation and the losses at the minimum level.

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ABSTRAK

Penyuisan Photonic merupakan keperluan utama dalam bidang rangkaian

perhubungan optik. Keperluan optikal boleh dibahagikan kepada komponen aktif dan

pasif. Di dalam projek ini, penyiasat terhadap ciri-ciri suhu, pengurangan isyarat atau

kehilangan isyarat di kenal pasti melalui eksperimen di makmal “Photonic” . Dalam

penyiasatan ini, kajian ilmiah dan cara – cara mengklasifikasikan komponen

“Termo-Optic” di kenal pasti. Dalam masa yang sama eksperimen bagi mengenal

pasti teknik bagi menghantar isyarat cahaya berbanding dengan cara-cara lain di

kenal pasti. Di akhir projek ini, satu teknik bagi menghantar isyarat cahaya dalam

pandu gelombang jenis “Slab” dengan mengambil kira kehilangan di kenal pasti.

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CONTENTS

TITLE i

DECLARATION ii

DEDICATION iii

ACKNOWLEDGMENTS iv

ABSTRACT v

ABSTRAK vi

TABLE OF CONTENTS vii

LIST OF TABLES x

LIST OF FIGURES xi

LIST OF SYMBOLS xiii

LIST OF APPENDICES xv

LIST OF ABBREVIATIONS xvi

CHAPTER 1 INTRODUCTION

1.1 Introduction 1

1.2 Objectives 3

1.3 Scopes of Research 3

1.4 Research Methodology 4

1.5 Thesis Organization 5

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CHAPTER 2 LITERATURE REVIEW

2.1 Introduction 6

2.2 Polymer Optical Wave guide 7

2.3 Properties of Polymer Material 10

2.4 Polymer switches 12

2.5 Review Intergrated Optics 14

2.6 Review Sources of Propagation Losses 16

2.7 Review Fabrication Process 24

2.8 Techniques of Measurement Losses in Optical guide 25

2.8.1 Prism Coupling 26

2.8.2 Scattered Light 29

2.8.3 Fabry-Perot Cavity 35

2.8.4 Direct Cut- Back 36

2.8.5 End Fire Coupling 40

CHAPTER 3 METHODOLOGY

3.1 Introduction 42

3.2 Cyclotene 4024-40 and Ancillary Chemicals 42

3.3 Fabrication Process 47

3.3.1 Surface Cleaning 49

3.3.2 Adhesion Promoter 50

3.3.3 Spin Coat 50

3.3.4 Oven Soft Bake 52

3.3.5 Exposure 53

3.3.6 End Point Monitor 53

3.3.7 Puddle Develop 54

3.3.8 Post Develp Bake 55

3.3.9 Cure 55

3.4 End Product 56

3.5 Experimental Set-up Using Prism Coupler 56

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3.5.1 List of Equipment Used 60

3.5.2 Experimental Set-up Procedures 61

3.5.3 Experimental Set-up (Actual Set-up in Lab) 62

3.6 Experimental Constrain 64

CHAPTER 4 RESULTS AND ANALYSIS

4.1 Introduction 65

4.2 List of Experimental Results and Relationship 67

4.2.1 Summary of Experimental Results 74

4.3 Cut-off Thckness Calculation 76

4.3.1 Matlab Program For Propagation Mode 78

CHAPTER 5 CONCLUSION AND FUTURE WORKS

5.1 Conclusion 80

5.2 Future works 83

REFERENCES 84

APPENDICES A-C 87

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LIST OF TABLES

TABLE TITLE PAGE

3.1 Composition of cyclotene 4024 and ancillary chemicals 44

3.2 Recommended storage temperatures of cyclotene 4024 47

3.3 Thickness of film for different spin speed 50

3.4 Cure profiles for convection oven curing 55

4.1 Summary of Results 66

4.2 Refractive index measurement results 75

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LIST OF FIGURES

FIGURE TITLE PAGE

1.1 OEO and OOO switch 2

1.2 Flow chart of research methodology 4

2.1 A Planar slab waveguide 7

2.2 Planar wave guide 14

2.3 Channel wave guide 15

2.4 Schematic of planar wave guide 18

2.5 Propagation constant of 19

2.6 Drawing of the lowest propagating TE modes with their 23

Power distribution curve

2.7 Flow chart of fabrication process 24

2.8 Brief descripition of each step in fabrication process 25

2.9 Launching the light using prism 27

2.10 Half prism for prism coupling method 28

2.11 CCD camera experimental data 33

2.12 Using optical fiber as alternatif to measure light source 33

2.13 Three prism experimental set-up 34

3.1 Refractive index against temperature 45

3.2 Optical losses against percentage of cure at

wave length 1300nm. 45

3.3 Refractive index against percentage of cure

of wave length 850nm. 46

3.4 Transmission against wavelength 46

3.5 Flowchart of fabrication process 48

3.6 Ultrasonic cleaner used in cleaning process 49

3.7 Spin coater model P6700 52

3.8 Oven used in softbake, post-develop and cure processes 53

3.9 Configuration of asymmetric slab waveguide 56

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3.10 (A) Prism Coupler Technique using two prism 59

3.10 (B) Prism coupler technique using probe 59

3.10 (C) Prism coupling using chopper & lock in amplifier 60

3.11 Typical equipment configuration 62

4.1 List of results 67

4.2 Refractive index profile after soft cure 75

4.3 Thickness against spin speed 76

4.4 Results at cut-off thickness calculation 77

4.5 Number of Propagation modes in the slab 79

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LIST OF SYMBOLS

c (m/s) - velocity of light in free space

B (W/m2) - magnetic flux density

D (C/m2) - electric flux density

E (V/m) - electric field intensity

H (A/m) - magnetic field intensity

k (m-1) - wave normal

m - mode number

N - effective index of a medium

n1 - refractive index of cladding region,

n2, nf - refractive index of guided wave region or film

n3, ns - refractive index of substrate layer

na - refractive index of air

np - refractive index of prism

W - beam width

t (µm) - optical guided layer thickness

tco (µm) - cutoff thickness of waveguiding layer

vp - phase velocity of an electromagnetic in a medium

, m - z- directional component of wave vector for guided wave

mode of order m

- permittivity of a medium

0 (F/m) - permittivity of free space

c (°) - critical angle of total internal reflection

i, m (°) - incidence angle with respect to normal

- coupling coefficient

- wavelength

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µ - permeability of a medium

- 3.142

12 - Goos-Hänchen phase shifts for mth mode, n1-n2 interface

32 - Goos-Hänchen phase shifts for mth mode, n3-n2 interface

(rad/s) - angular frequency

- del operator

- curl operator

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LIST OF APPENDICES

APPENDIX TITLE PAGE

A Cyclotene 4024-40 Properties 70

B Cyclotene 4024-40 Processing Notes 74

C Matlab Program to Calculate Cutoff Thickness 77

D Matlab Program to Calculate Effective Index, 80

Thickness and Refractive Index.

E Loss Measurement Technique by SPA-4000 Series 82

(Matching Index Oil Technique)

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LIST OF ABBREVIATIONS

2-D - Two Dimensional

3-D - Three Dimensional

BCB - B-Staged Bisbenzocyclobute

OEO - Optical-Electrical-Optical Switch

OOO - All Optical Switch

TE - Transverse Electric

TIR - Total Internal Reflection

TM - Transverse Magnetic

UV - Ultra Violet

CHAPTER 1

INTRODUCTION

1.1 Introduction

Demands of high bandwidth for present and future communication system,

especially in multimedia communication have forced new technology to support

these kinds of applications. Optical communication systems offer enormous potential

bandwidth compared with other communication systems. Thus, optical integrated

devices may play important role in networks switching to achieve ‘All optical

Network’ (or sometimes referred to as OOO) as shown in Figure 1.1 which is

subjected to replace OEO (Optical-Electrical-Optical) switching network in near

future. Most curent optical switches use an electric core in switching. Advantages of

OEO switch are flexible and well established but it suffers from electronic

bottleneck, costly and high power consumption. Thus, the OOO technologies are

becoming much more attractive than the OEO because of the avoidance of the

electronic bottleneck, less expensive, low power switching and independent of data

protocol [1,2]. Currently, there are few tehnologies of OOO including the thermo-

optics and electro-optics which use optical waveguide as the basic components.

Therefore, research in optical waveguide is still important and ongoing nowadays, in

fact it is the first major step towards development of OOO technologies.

This project is mainly involved in-house fabrication and characterization of

cyclotene polymer based optical slab waveguide. Slab waveguides were fabricated

by deposition of polymer onto substrate to form a film layer and spinning the

substrate on a spinner to spread the layer evenly. Different thicknesses of slab

2

waveguide were realized by using different spin speed. The waveguide layers consist

of the new type of polymer cyclotene 4024-40 as the waveguiding layer, microscope

glass as the substrate and air as the cladding. These samples were then characterized

in terms of refractive index and thickness using prism coupler measurement

equipment. This technique was first successfull demonstrated in 1969 by Ulrich, Tien

and Martin [3] which well explained of its basic principle.

Prism coupler is well established, versatile, accurate and reliable method and

until now, many new configurations and modeling of this technique have been

discussed in published journals [4,5,6] in optical measurement. It is much more

interesting since this equipment is the first such system available in Malaysia.

Therefore, this system need to be tested for further use in optical measurement. The

next section in this chapter presents the objective, scopes and research methodology

of this thesis. Description of thesis organization is presented at the end of this

section.

Figure 1.1: OEO and OOO switch [1]

SD

1648SMCommunication Subsystem Shelf

Electronic SwitchOptical to electrical

conversion

Electrical to optical

conversion

OEO Core Optical Switch

SD1648 SM

Communication Subsystem Shelf

All Optical Switch

Optical Switch Photonic Path

3

1.2 Objectives

1) To establish the attenuation and the losses using polymer slab

wave guide at various length & thickness

2) To establish the effect of rotation per minute (RPM) on the

attenuation & losses for polymer slab wave guide.

1.3 Scopes of Research

i. To understand fundamentals of related areas including optical waveguide

and optical measurement techniques and

ii. To study properties of cyclotene 4024-40 photo polymer from the

given specifications.

iii. To understand and practice in house fabrication process of slab

waveguide.

iv. To measure atenuation of the fabricated slab waveguides using prism

coupler measurement equipment.

v. To make comparison between results obtained from prism coupler

measurement and other measurement equipment.

vi. To analyse measured results.

4

1.4 Research Methodology

To achieve the objectives, the following steps as shown in Figure 1.2 has

been taken:

Determination of the fabricated of slab waveguide

Determination of the light

propagation

Experimental Set-up

Measurement using prism coupler and other equipment

Report writing

YesNo

Figure 1.2: Flow chart of research methodology

Literature Review

5

This project started with literature review to understand fundamentals,

requirements, problems and technology related to this topic by reviewed on

published journals and books. These include fundamentals of optical waveguide,

optical measurement technique, and technique of fabrication. The second stage was

to determine the requirements of this project in terms of facilities, materials and

equipment. Facility such as clean room for in house fabrication should be well

equipped prior to the fabrication stage. A new polymer, the cyclotene 4024-40 was

used in this experiment, Other equipments such the spincoater, oven, ultrasonic

cleaner and hotplate were then prepared to their best condition. The third stage was

examine the fabricated polymer on the light propagation with particular coated

polymer. The fourth stage was to characterize the optical properties of the fabricated

slab waveguide such as width of the propagated light and the attenuation using

suitable set-up. All the results were collected during both stages. The final stage was

to write report which is composed of all the findings, results and conclusion.

1.5 Thesis Organization

This thesis is organized into 5 chapters. Begins with Chapter 1 with

explaination of motivation and importance of the project, objective, scopes and

research methodology. Chapter 2 is the literature review part, presents related

theories of dielectric slab waveguide which important in this research. These include

the derivation of mode in slab waveguide using the ray optic and electromagnetic

theory, the fabrication part, thermal effect and attenuation. In Chapter 3, presents

various method used to measure attenuation, more focused on the prism coupler

principle and prism coupler technique in optical measurement. This includes

measurement of coupling angle in order to determine refractive index and thickness

of waveguide. Measured results and analysis of data are presented in Chapter 4.

Finally, Chapter 5 presents the conclucion based from all the works and results

achieved throughout this research. Several recommendations for further works are

also given.

84

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guides,” J. Opt. Soc. Amer., vol. 60, pp. 1325-1337, 1970.

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85

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