Invited Talk - Bilaspur Univ

8/14/2019 Invited Talk - Bilaspur Univ

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D. K. Gautam, Department of Electronics, North Maharashtra University, Jalgaon-425 001 (MS) INDIA

Design and Fabrication of the

Guided Wave Devices atNorth Maharashtra University,

Jalgaon

D. K. Gautam

Department of Electronics,North Maharashtra University,

Jalgaon 425 001(MS) INDIA


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Present trends of Optoelectronics

Designing, modeling and

analysis of lasers and other

devices are being carried outOptimization of Optic fibers

In India In abroad

Optoelectronic materials thin

films

Device fabrication is being carriedout at few places

Standardization in design,analysis

and fabrication

Optoelectronics Integrated circuit

Micro-machineries, short wave

length lasers, optical computing

Applied opt-electronics equipment

Guided wave remote controlled

automatic equipments



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Optical Communication Networks are

being installed in India

Inevitable need for the developing the

INDEGENEOUS technologyfor Fabricating the components required for

the communication networks

Cost Effectiveness


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Various Components required for the networks

Power Splitters /

CombinersModulators / switchesMulti/Demultiplexers

Isolators

Passive

Laser DiodeAmplifierLED

Active


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Next Generation Computers and Integrated Circuits

Further Miniaturization forIncreased SpeedHigher Capacity

Tighter Confinement of Light

Photonic Crystal Devices

Demand for

That Needs

New class of Devices


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Research & Development

strategy at N.M.U.

Department of Electronics

First Tire

Design &

Development

Laboratory

IndigenouslyDeveloped

Software

Tools

Second Tire

Sophisticated

Clean Room

Indigenously

Developed

Fabrication

Machines

Third Tire

Mass Scale

Production

facilities

Characterizationtools


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Department of Electronics,

North Maharashtra University

Active / Passive Devices

Design

Established 10 years ago

One of the Pioneer Institutions to Initiate

the work related to optical guided wave devices

Capable of

Fabrication

Some Fabrication

Facilities have been

developed already, Work

is in progress to developother facilities


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CAD Tools

CAD Tools Based on BPM and FDTDApplicable to the Passive Devices:

Optical Waveguide Waveguide Transitions, Bends, Junctions Optical Multi/demultiplexer

Tools for Quantum Well Structures

CAD Tools for the design of the Laser diode Blue Laser Diode

GaN/AlGaN Heterostructure Laser Diode

ZnO/MgZnO Heterostructure Laser Diode


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Design Group


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Rib Waveguide Design

t

w

dhGT

SiO2 buffer layer

Guide layer

Upper clad layer

Silicon Substrate



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Guiding Film

Upper Clad

Air

Lower clad

Guiding Film

Upper Clad

Air

Lower clad

Guiding Film

Upper Clad

Air

Lower clad

Clad

Nef1

Guide

Nef2

Clad

Nef1

STEP I

STEPII

Non

Guidingregion

Guiding

region

w

dh

GT

Guide I GuideII

Guide III

Guide IV

Non

Guidingregion

Effective Index Method

Applied to the

Rib Waveguide Structure


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+=+ 2

0

0012

exp),,(),,( nn

jkzzyxezzyxE

=+n

nnn zjkyxEazzyxe )exp(),(),,( 0

=n

nn yxEazyxe ),(),,( 0

),(),,( 0 yxEzyxea nn +

=

Main Equations used to Implement the

Beam Propagation Algorithm

Decomposition to the

Fourier Components

Propagation in

Fourier Domain

Correction for

the perturbation

in Refractive

Index

Inverse Fourier Transform



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Our Tools Applied for the Design of theOur Tools Applied for the Design of the

Directional Coupler Based DemultiplexerDirectional Coupler Based Demultiplexer

1,

2

1

2

s

w Guide I

Guide II

Advantage: Easy Fabrication Method

W=waveguide widthS=separation between the waveguides


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Bpm simulation results for the propagation of

two wavelengths through the demux

1 = 1.3 m 2 = 1.304 m

Guide Separation = 2.5 m

Guide Thickness = 4.4 m

Rib Width = 9 m

Rib Height = 2 mClad Thickness = 2 m

Device Length = 7.3175 cm


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Hetero-structure Laser Design


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Electrical Equations

Poissons Equation

Continuity Equations forelectrons and holes

Current density Equation

Physical EquationsPhysical Equations

Optical Equations

Wave Equation

Rate Equation forPhotons

Output CharacteristicsOutput Characteristics



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Blue Laser Structure Used for the AnalysisBlue Laser Structure Used for the Analysis

n- Substrate

Lower clad

Active layer

Upper clad

p-contact

n-contact

x

Y



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Structural Parameters used for AnalysisStructural Parameters used for Analysis

Layer Thickness

in

nanometer

Doping

Concentra-

tion in cm-3 .

Refractive

Index

% of

Magnesium

% of

Sulphur

Substrate

GaAs1180 3 * 1018 3.6

Lower

clad

ZnMgSSe

7677 * 10

17 2.5878 13 % 17 %

Active

layer

ZnSSe

50 1.7 * 1016 2.78 0 % 3 %

Upper

clad

ZnMgSSe

138 7 * 1016 2.5878 13 % 17 %

Device width: 60 micron

Channel width: 5 micron

Channel depth: 0.5 micron


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Plot of Intensity(relative) verses WavelengthPlot of Intensity(relative) verses Wavelength

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

503 505 507 509 511 513

Wavelength (nanometer)

Intensity

(re

lative

)



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Field Intensity Distribution in X-direction

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

5 15 25 35 45 55

Distance X (micrometer)

Intens

it



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Field intensity distribution in Y-direction

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

700 1000 1300 1600 1900 2200 2500

Distance Y (nanometer)

Intensit

Substrate Lower clad Upper

clad

Active layer



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Waveguidestructure

used for the lightconfinement in

thevertical direction.

Waveguidestructure

used for the light

confinement in thehorizontal direction

Analysis of optical field confinement

Lower Clad ncn

Active Layernf

Upper Clad ncu

X

Y

X

Y

Nl Nm Nr



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0

5

10

15

20

25

30

35

0 5 10 15 20 25 30 35

Channel width (micron)

Fullwidthath

alfmaximu

Full width of half maximum of field spreading as a

function of channel width at 507 nanometer



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Photonic Crystal Device Design


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Photonic CrystalPhotonic Crystal - Photonic crystals are micro-

structured materials in which the dielectric constant isperiodically modulated on a length scale comparable to the

desired wavelength of operation and in which

electromagnetic waves of desired frequencies are forbidden.

WHAT IS PHOTONIC CRYSTAL?


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Why Photonic Crystal ?

Most Important Points for today's VLSI/ULSI and Communication

Technology :

Speed Photonic crystals uses photons hence speed is greater thanelectro-optical devices.

Size Photonic crystals has the dimensions of nano-sizes hence verycompact size devices are possible.

Information carrying capacity Photonic crystals usesphotons hence information carrying capacity is greater.

All-optical ICs All-optical ICs can be developed because usingphotonic crystals various devises can be fabricated such as

lasers, filters fibers, multiplexer/demultiplexer,


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Semiconductor

crystal

Semiconductor

crystal

PeriodicPotential

Dueto

Photonic

crystal

Photonic

crystal

Periodic

AtomicLattice

Bragg-likediffractio

n fromatomForbidden Gapfor electrons

PeriodicPotential

Dueto

Lattice of

macroscopicdielectricmedia

Bragg-scattering atthe dielectric

interfacesForbidden band gap(Photonic band gap)

for photons


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One dimensional

photonic crystals

Periodic inone direction

x

yz


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Two dimensionalphotonic crystals

Periodic in

two direction

x

yz

A)

B)

A) Dialectic rod PC with triangular lattice - lattice constant 700 nm, roddiameter 500 nm, rod height 3.9 m.

B) Air column PC with triangular lattice - lattice constant 580 nm, columnradius 430 nm, column height 4.2 m.

(Obtained by Reactive ion etching of Si)


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Point Defect Planer DefectLine Defect

Resonant Cavity

(Traps Light)

Waveguide

(Transports Light)

PerfectDielectric mirror

(Reflects Light)

Defects in Photonic Crystals


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FabricationGroup



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FHD Sol-gel PECVD

1. High growth rate

2. Porous Films

3. Poor uniformity

4. High temperatureprocess

5. Annealing needed

6. Cannot be used inmicroelectronics

1. High growth rate

2. Porous film

3. Poor uniformity

4. Low temperatureprocess

5. Annealing needed

1. High growth rate

2. Dense film

3. Good uniformity

4. Low temperatureprocess

5. Annealing notrequired

6. Useful for

microelectronics

High growth rate techniques


Ch i l V D iti


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Chemical Vapor DepositionTechniquesSr.No.

Properties APCVD LPCVD PECVD

01. Temperature (

o

C) 300-500 500-900100-350

02. Materials SiO2

Poly-Si, SiO2,

Si3N

4, SiO

xN

y

Si3N

4, SiO

2,

SiOxN

y

03. Particles Many Few Many

04. Film Properties Good Excellent Excellent

05. Advantages Simple reactor,

Fast Deposition,

Excellent purity

and uniformity

Low temp, Fast

deposition

06. Disadvantages Poor stepcoverage &

particlecontamination

Low deposition

rate

Chemical and

Particulate

contamination

07. Applications Passivation,

Insulation

Gate metal,

Passivation,

Insulation

Final Passivation,

Insulation



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TEOS

Solution is

Conventional CVD Technique

Use of Silane Dichloro - Silane

Toxic

Explosive

Pyrophoric

Corrosive

Dangerous in handling

Extra Safety Measures

required

More Deposition Cost



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TEOS-CVD

Reaction[Si(OC2H5)4] + O2 = SiO2 + by

products

Advantages

TEOS is nontoxic Non

Pyrophoric Stable, inertliquid

used inbubbler Handling iseasy

Deposited films Show

Excellentuniformity

Conformal stepcoverage Good filmproperties


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Why SiO2 Films for Optical Devices?

Matured Process Technology

Refractive Index matches with the

Optical Fiber

Minimizes the coupling losses

Polarization independent operation

Easy Fabrication

High integration capacityLow manufacturing cost



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Why Si3N4 and SiOxNy Films?

Superior material properties like:

High density,

High electrical resistivity,

Resistance to sodium ion, Moisture permeation,

High thermal stability

Adjustable refractive index Adjustable film stress


Optimization of process


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Optimization of processparameters

Growth

rate

Flow rate

Chamber pressureSubstrate

temperatureTEOS temperature

Reactor

geometry

Residence time

Material ofelectrodeInter electrodespacingElectrode type

RF Power


Processing Parameters


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Processing Parameters

Sr.

No.Process parameter Physical value

1 Chamber Pressure 1 Torr

2 TEOS flow rate 3 SCCS

3 O2 flow rate 15 SCCS4 TEOS Bubbler temp. 450 C

5 RF power 40 W

6 RF frequency 13.56 MHz

7 Substrate temperature 300 0 C


Thickness Profile of SiO Films by


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Thickness Profile of SiO2 Films by

PECVD


Refractive Index Profile of SiO Films


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Refractive Index Profile of SiO2 Films

by PECVD


FTIR Transmittance spectrum of SiO Films by PECVD


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FTIR Transmittance spectrum of SiO2 Films by PECVD



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S.N. Si-O-Si stret-

ching (cm-1)

Si-O-Si

bending (cm-1)

Si-O-Si

rocking (cm-1)

FWHM Authors

01 1070 810 450 88 L. Zajickova et al

02 1074 820 --- 92.8 Ying-Chia CHEN

et al

03 1080 800 --- --- Kunio Okimura et

al

04 1069 --- --- --- K. Ramkumar et al

05

1072 820 447 --- Nur Selamoglu et

al

06 1080 --- --- 140 William J. Patricet al

07 1070 --- --- 67.7 K. Ishii et al

08 1076.2 814.3 447.5 85.68 Present study

Transmittance Spectra of SiO2 films by PECVD


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EDX of the deposited SiO2 films by PECVD



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Surface MorphologySurface Morphology

Microphotograph of granular SiO2 film



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Microphotograph of uniform SiO2 film

Surface MorphologySurface Morphology



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FTIR Absorption Spectra of Deposited Si N Films


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FTIR Absorption Spectra of Deposited Si3N4 Films

Wavenumber (cm-1)

N-H Stretch

3378.8 cm-1

Si-H Stretch

Si-N-Si Stretch

N-H bending1179.9 cm-1

Si-NVibration

493.3 cm-1

N-H

1579.8 cm-1

Ab

sorp

tion


C i S


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0

1

2

3

4

5

6

7

740 780 820 860

Deposition temperature (oC)

HConcentration(X1023c

m-3)

Si-H

N-H

H total

Total Hydrogen Concentration Vs. Substrate Temperature


SEM f D it d Sili Nit id Fil


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SEM of Deposited Silicon Nitride Films



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Invited Talk - Bilaspur Univ