Submicron SOI waveguides - UGentphotonics.intec.ugent.be/download/ocs63.pdf · 2005. 3. 11. ·...

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Submicron SOI waveguides

Dries Van ThourhoutTrento ‘05

http://photonics.intec.UGent.be 2© intec 2004

AcknowledgementsThe European Union IST-PICCO and IST-PICMOS projectThe European Space AgencyThe Belgian IAP-PHOTON networkThe Flemish Institute for the industrial advancement of Scientific and Technological Research (IWT)

The Photonic Research Group at Ghent University – IMECPieter Dumon, Wim Bogaerts, Dries Van Thourhout, Dirk Taillaert, Bert Luyssaert, Peter Bienstman, Joris Van Campenhout, Gunther Roelkens, Ilse ChristiaensThe Silicon Process division at IMECVincent Wiaux, Stephan Beckx, Johan Wouters, DizianaVangoidsenhoven, Rudi De Ruyter, Johan Mees


OutlineSubmicron SOI-wires

Introduction: why do we need themBasic properties: design, loss, wavelength, polarizationFabricationDevices: couplers, crossings, filters …

III-V on SiliconIntroductionCoupling of lightFabricationPICMOS (Photonic Interconnect on CMOS)


Scale differenceElectronics

Active opto-electronics

Passive photonics

1cm1mm100µm10µm1µm100nm

AWG in Silica on SiliconBend radius

linewidth in current PIC

VCSELstripe laserLED

detector

gatewidth

transistor

taperspot-sizeconvertor

2R regenerator

fibre core

flip-flop

Wavelength-scale photonics

interconnects

Wavelength-scale photonics


PICs: today and futureToday (InP, Silica-on-Silicon...):

Size of components on a chip (both functional components and interconnect components):

103 - 106 µm2

Number of components on a chip:1 - 103

Future (10-20 years from now):Size of components on a chip (both functional components and interconnect components):

1 - 103 µm2

Number of components on a chip:103 - 106


Silica-on-silicon

NTT (e.g. Miya e.a., IEEE STQE ’00 pp.38)


Reduce PIC-size / increase density WE NEED:Ultra-compact waveguiding with

Sharp bends (Bend radius < 10µm)

Compact splitters and combiners

Short mode-conversion distances

Compact wavelength selective functionsHighly dispersive element

Small, high-Q resonators

Compact non-linear functionsIncrease power density by using tight confinement


High refractive index contrast (>2:1)High refractive index contrast allows for:

Very tight bendsCompact resonators with low lossWide angle mirrorsVery compact mode size

strong field strength strong non-linear effectssmall volume to be pumped in active devices faster and/or lower power

Photonic band gap effects

air semiconductor

dielectric

High refractive index contrast is key for ultra-compact photonic circuits


Index ContrastConventional PICs Nanophotonics

In-plane (effective) index contrast

Out

-of-p

lane

inde

x co

ntra

st

Low

Low

High

High


Materials for nanophotonic waveguides

In-plane indexcontrast

Out-of-planeindex contrast

Si/SiO2 (SOI) 3.5 to 1 3.5 to 1.5

Si/air(membrane)

3.5 to 1 3.5 to 1

GaAs/AlOx 3.5 to 1 3.5 to 1.5

InP/SiO2 3.3 to 1 3.3 to 1.5

SiON/SiO2 2 to 1.5/1 2 to 1.5

GaAs/AlGaAs 3.5 to 1 3.5 to 3.2

InGaAsP/InP 3.3 to 1 3.3 to 3.17


SOI nanophotonics

Start: SOI-Wafer• Thin Silicon layer• Thick SiO2 buffer

BOX thickness

Waveguide Definition

Width + Height


SOI-wires

EBeamyes1110.0 600260Oct. 03Columbia5.0 500200

DUVyes115.0 300300Apr. '05LETI / LPM+oxidation0.8 20050G-lineyes132.0 500200Dec. '01MITEBeamno1105.0 400320Dec. '02YokohamaEBeamno36.0 300300Dec. '02NTTEBeamno35.0 470270Aug. '03CornellEBeamno23.6 445220Apr. '04IBMDUVno12.4 500220Apr. '04IMEC

Fab.top clad

BOX [um]

loss [dB/cm]

w [nm]

h [nm]

DateGroup

(Table partly from Vlasov, McNab, Opt. Expr. ’04, pp1630)


OutlineSubmicron SOI-wires

Introduction: why do we need themBasic properties: theory, design, loss, wavelength, polarizationFabricationDevices: couplers, crossings, filters …



Back to basics: cavities and waveguides

How does light propagate in waveguides and cavities?

n1

n2

n2

n1

n2

n2

n1

n2

n2

n1

n2

n2

Propagation in waveguide

Propagation through cavity

Emission within waveguide/cavity

Propagation through waveguide discontinuity

What is the role of n2 /n1 ?



kx

kz

TotalInternalReflection

Radiation modes

n2k0 n1k0

d n1

n2

n2

k

kx

kz

• dispersion:

• continuity:

For slab waveguide: n2 /n1 0.99 0.9 0.5Fraction of (2D) k-space confined by TIR = 14% 44% 87%

For channel waveguide:Fraction of (3D) k-space confined by TIR = 2% 19% 75%

“Light line”

220 yx kkc

nnkk +=== ω

2,1, xx kk =

2

1

21 ⎟⎠

⎞⎜⎝

⎛−

nn

2

1

21 ⎟⎠

⎞⎜⎝

⎛−

nn



kx

kz

π/d

Resonance if ↓

d large → many resonancesd small → few resonances

Two types of resonances:

• guided modes confined by TIR

• resonantly enhanced radiation modes

d n1

n2

n2

k

kx

kz

Only one guided mode if

dmkz

π=

( )2121

12

nn

nd−

≤λ



Waveguide/cavity types:• conventional waveguide: n2 /n1 ≈ 0.9 - 1

single mode even for d substantially larger than λ/n1lots of radiation modes

only small fraction of k-space well controlled by TIR

hence bends, couplers need to be based onslow adiabatic transitions → longinterference with long coupling length between guided modes → long



Waveguide/cavity types:• high contrast waveguide: n2 /n1


Back to basics: periodic stacks

n1

n1

n1

n2

n2

Λ

kx

kz

n2k0 n1k0

Strong reflection and little transmission if:(for normal incidence)

(Bragg condition)

2π/Λd1

d2

Λ=

Λ+

Λπmdkdk 2211

Λ+

Λ=

=Λ→

22

11:

2dndnnwith

nm

av

av

λ


Back to basics: periodic stacks

Cases:• low contrast stack: n2 /n1 ≈ 1

many periods needed for strong reflection

strong reflection only for narrow angular and spectral range

• high contrast stack: n2 /n1


Spectral accuracy and geometrical accuracy

High index contrast components:- interference based filters,

with d the waveguide width (≈λ)

- cavity resonance wavelengthwith d the cavity length (a few λ)

- photonic crystalwith d the hole diameter (≈λ)

dd∂

≈∂λλ

if tolerable wavelength error : 1 nm ⇓

tolerable length scale error : (of the order of) 1 nm

dd∂

≈∂λλ

dd∂

≈∂λλ


Basic PropertiesEffective Index

1

1.25

1.5

1.75

2

2.25

2.5

2.75

300 400 500 600 700 800

Waveguide Width [nm]

Effe

ctiv

e In

dex

TE0

TE1

TM0TM0

TE1

Single-Mode Width

Cladding (1.44)

h=220nm – λ=1550nm – 2D calc


1

1.25

1.5

1.75

2

2.25

2.5

2.75

300 400 500 600 700 800

Basic PropertiesEffective Index

Waveguide Width [nm]

Effe

ctiv

e In

dex TE0

TE1

TM0TM0

TE1

Single-Mode Width

Cladding (1.44)

h=220nm – λ=1550nm – 2D calc


Basic PropertiesGroup Index

h=220nm – λ=1550nm – 2D calc

1

1.5

2

2.5

3

3.5

4

4.5

5

1500 1525 1550 1575 1600Wavelength [nm]

n eff

-ngr

oup

w=400-600

w=400-600

1.52

2.53

3.54

4.55

400 450 500 550 600Waveguide Width [nm]

νν+=

λλ−=

ddnn

ddnnng Determines filter properties

ngroup

neff


Substate Leakage

BOX Buffer Thickness [um]

Subs

trat

e Le

akag

e Lo

ss [d

B/c

m]

w=300nmw=500nm

1dB/cm

h=220nm – λ=1550nm


Losses


DUVyes115.0 300300Apr. '05LETI/ LPM

+oxidation0.8 20050

G-lineyes132.0 500200Dec. '01MIT11EBeamno1105.0 400320Dec. '02Yokohama

EBeamno36.0 300300Dec. '02NTTEBeamno35.0 470270Aug. '03Cornell

2.5EBeamno23.6 445220Apr. '04IBM< 5DUVno12.4 500220Apr. '04IMEC

σroughness [nm]

Fab.top clad

BOX [um]

loss [dB/cm]

w [nm]

h [nm]

DateGroup


0

5

10

15

20

25

30

35

40

300 350 400 450 500 550

Wire width (nm)

Loss

es (d

B/c

m)

w400nm440nm450nm500nm

33.89.47.42.4

Propagation losses± 1.7 dB/cm± 1.8 dB/cm± 0.9 dB/cm± 1.6 dB/cm

Loss (IMEC)

22

2s

2s n

dxEE

∆σ

∝α∫ Refractive index contrast

Field at interfaceSurface Roughness

Width [nm]

Loss

[dB

/cm

]

IBM


Loss (IBM)2

2

2s

2s n

dxEE

∆σ

∝α∫

Wavelength [nm]

Loss

[dB

/cm

]

3.5dB/cm

(Vlasov, McNab, Optics Express, ’04)

w=450nmh=220nm

TETM


Loss - otherOxidationDifference TE/TM

TM higher substrate leakage

TM higher scattering at vertical roughness

TE higher field intensityRoughness Correlation lengthGrillot e.a., PTL ’04, pp. 1661

(MIT)(Grillot)


Polarisation


DUVyes115.0 300300Apr. '05LETI/LPM

+oxidation0.8 20050

G-lineyes132.0 500200Dec. '01MIT11EBeamno1105.0 400320Dec. '02Yokohama

EBeamno36.0 300300Dec. '02NTTEBeamno35.0 470270Aug. '03Cornell

2.5EBeamno23.6 445220Apr. '04IBM< 5DUVno12.4 500220Apr. '04IMEC

σroughness [nm]

Fab.top clad

BOX [um]

loss [dB/cm]

w [nm]

h [nm]

DateGroup


PolarisationIssues:

Rectangular cross-section: very different neffSquare cross-section:

neff,TE = neff,TMBut: polarisation conversion + higher losses

Polarisation conversion in bends studied by SakaiFDTD: Conversion < 25dB (R>1um)Experiment: -13dB to -10dBReason: side wall angle (85o)

Polarisation insensitivity: hopeless ??Use polarisation diversity

(Sakai, Fukazawa, Baba, JLT ’04, pp. 520)


Temperature dependence

K/pm140dTdK1079.1

dTdn c14Si =λ⇒×= −−

Classical Filters: dTdn

dd c =

λλ

(λc : central wavelength)


Temperature DependenceUse Temperature Dependence for TO-switch

Espinola e.a. (PTL ’03, pp. 1366)

Lh=650um

Switching time = 3.5us

Switching power = 50mW


Waveguide Density

Photonic Crystal Guides have smaller mode diameter but require several rows of holes !!!

Further scaling: increase height, increase index (?)

Surface Plasmon waveguides ?

Min

. Cen

ter-

to-c

ente

r [µ

m]

Waveguide Width [µm]

Single mode

Crosstalk < 20dB/cm


Bends

4040

0.150.05

2.05.0

500220LETI/LPM

2 bends1.3resonant 400340Columbia

poly-Si0.3resonant 12 bends0.51.0 500200MIT

31.0 400320Yokohama0.173.0

24 bends0.462.0 300300NTT05.0 ?2.0 ?1.0 500220IMEC05.0

0.0132.0 20 bends0.0861.0 445220IBMNote

Loss [dB/90]

Radius [um]

w [nm]

h [nm]Group

(Table partly from Vlasov, McNab, Opt. Expr. ’04, pp1630)


Bends

Wide λ-range

No need for resonant bends ?

(Vlasov, Mc Nab)


Submicron SOI-wiresIntroduction: why do we need themBasic properties: design, loss, wavelength, polarizationFabricationDevices: couplers, crossings, filters …


Outline


Fabrication: Review

RIE (CF4:Ar)AluminiumEBeamyes1110.0 Columbiamixed5.0

HBr etchingSiO2DUVyes115.0 LETIoxidation0.8

RIE (SF6)SiO2G-lineyes32.0 MITICP (CF4 + Xe)metalEBeamno1105.0 Yokohama

SF6/CF4 etch, ECR-etchEBeamno36.0 NTTICPEBeamno35.0 Cornell

CF4/CHF3/Ar (Oxide) + HBr (Silicon)SiO2EBeamno23.6 IBM

Cl2/He/Hbr/O2ResistDUVno12.4 IMEC

Etch MethodMaskFab.top clad

BOX [um]

loss [dB/c

m]

Group


FabricationEBeam

Best suited for research, Features < 50nmSlow, not compatible with mass-fabrication (?)

Standard Litho (G-line, I-Line)OK for 500nm linesProblem for smaller features (gaps in direction coupler, PhC, taper tips

DUV (248nm, 193nm)Resolution OK (but characterisation needed !)Compatible with Mass-FabricationExpensive mask


Original fabrication process

Si-substrate

SiO2Si

Photoresist Photoresist

AR-coating

wafer Photoresist(UV3)

Bare Soft bake AR coating Illumination(248nm deep UV)

bakePost Development Silicon etch Oxide etch Resist strip


Line width with exposure dose

200

300

400

500

600

700

800

900

10 15 20 25 30 35 40

200

300

400

500

600

700

DesignedLine Width

Line width (nm)

Exposure dose (mJ)


Hole size with exposure dose

150

200

250

300

350

400

450

500

550

10 15 20 25 30 35 40

400/240400/320450/270450/360500/300500/400550/220550/330550/440600/240600/360600/480

DesignedPitch/diameter

Hole size (nm)

Exposure dose (mJ)

Sufficient ProcesswindowMarginally

sufficient


-5%-10%-15% +5% +10% +15%

-0.4

-0.2

Bestfocus

+0.2

+0.4

Exposure Energy [∆E/E0 ]

Bestenergy

Focu

s [µ

m]

λ = 248nmNA = 0.63resist = UV3


λ = 248nmNA = 0.7resist = TIS

Process WindowDesign Pitch/Size: 500nm /300nmTarget size: 300nm

5% deviation ellipse



-5%-10%-15% +5% +10% +15%

-0.2

-0.1

Bestfocus

+0.1

+0.2

Exposure Energy [∆E/E0 ]

Bestenergy

Focu

s [µ

m]




Process WindowDesign Pitch/Size: 400nm /240nmTarget size: 200nm

5% deviation ellipse



Optical proximity effectsexample:

triangular lattice

pitch = 530nm

Diameter = 420nm

r/a = 0.4

1um

resist

Bulk hole = 420nm

Border hole = 380nm

Corner hole = 350nm


Optical proximity effectsW1 waveguide

pitch = 500nmhole Ø in bulk lattice = 300nm

0.400.42 0.44 0.46 0.48 0.50k

0.26

0.27

0.28

0.29

0.30

0.31

0.32a/λ

Light cone

Oddlattice

modes

Even lattice modes

0.42 0.44 0.46 0.48 0.50k

0.40

MSB MSB

Øborder=310nm Øborder=320nm λ(nm)

1925

1850

1785

1725

1665

1610

1560

0.42 0.44 0.46 0.48k

0.40

MSB

Øborder=300nm

0.50

Light cone

Oddlattice

modes

Even lattice modes

Light cone

Oddlattice

modes

Even lattice modes


Optical Proximity CorrectionProblem: Optical Proximity EffectsHoles at lattice boundary are different than holes in bulk due to interference effects

Correction on mask required (also on PICCO_03)

Original Mask layout Resist on wafer Mask layout with OPC


Optical proximity correctionsDetermine empirically from PICCO_01

Example: 500nm pitch, 300→320nm holes

Border hole

bias (nm)

Corner hole bias (nm)

Hol

e si

ze d

evia

tion

(nm

)

Bulk

Border hole

Corner hole


Deep Etch RoughnessExample: Ring resonator

Straight wire=400nmRing wire = 500nm


OxidationThermal oxidation of top Silicon layer.

Roughness reduction

Lithography Si+SiO2 Etch 20-60nm thermal oxide

Oxide removalwith HF dip

optiona

l

10nmoxide

30nmoxide 50nm

oxide

Roughness onair-oxide interface


Shallow etchingShallow etching → less roughnessBut: Scattering at bottom of hole

Roughness reduction

Lithography Si Etch 10nm oxide Oxide deposition

Re-fill hole with oxide to reduce asymmetry

200nm hole

optiona

l


Silicon-only etch

Deep etching Si-only etching

Less roughness


Etch bias with Silicon-only etchThick resist layer: 800nm UV3

needed for deep etching200-300nm hole Ø: high aspect ratiocauses litho-etch bias

800n

m

300nmhole Ø

Litho Etch Result

shadowof thickresist

230-250nmhole Ø


Etch bias with Silicon-only etchOptimal Solution:

new litho + etch development: no time.Short-term Solution:

Resist-hardening/Resist Trimming plasma treatment

800n

m

300nmhole Ø

Litho Etch ResultRH

300nmhole Ø

smallershadow

Still slightly sloped sidewalls


Updated Fabrication Process

Si-substrate

SiO2Si

Photoresist Photoresist

AR-coating

wafer Photoresist(UV3)

Bare Soft bake AR coating Illumination(248nm deep UV)

bakePost Development Resist Hardening

Silicon etch Resist strip


2-step processingTwo types of structures

Waveguides: requires deep etch (al least through Silicon)

Fibre couplers: require 50nm etch

Two-step processingFibre couplers first: 50nm etch gives little topography

Wafer-scale alignment: Alignment markers on the wafer and reticle periphery, not between the structures


2-step processing

deep trench

shallow fibre coupler


CMOS-compatible ?Well, it is SiliconIt is processed in a CMOS line

ButCMOS = layered

We: lines, holes, gaps, tips all in same layerCMOS = vias but rather low density

Phot Crystals = superdense latticesLine-edge roughness: no issue in CMOS (till now)

Roughness kills everything


Submicron SOI-wiresIntroduction: why do we need themBasic properties: design, loss, wavelength, polarizationFabricationDevices


Outline

• Couplers• Crossings• Ring Resonators• AWG• Cascaded MachZehnder• Fibre-chip couplers


Couplers - SplittersDirectional Couplers

Used in ring resonators, cascaded MZI …“Easy” to choose splitting ratioSensitive to fabrication issues (optical proximity, deviations in widths)

Multi-mode interference couplers (MMI)Fabrication tolerant

Standard Y-juncionSymmetric, narrow gap

Advanced CouplersSakai, Fukazawa, Baba, IEICE Trans ’02, 1033


CouplersYokohama Nat. Univ

Simulation:


CrossingsCrosstalk free crossings in optics ?

Standard crossingLarge diffractionLarge crosstalk (-9dB)Large loss (1.4dB)

Enhanced versionsBetter performanceLarger

NOT acceptable for large density circuitsUse multiple waveguide layers ??


Fibre coupling

InP ridge wg

SM-fibre core

SOI PhC wg

µmMode mismatch between waveguide and fibre


Coupling to fiberImportant:

Large bandwidth

Low loss

FabricationLimited extra processingTolerant to fabrication deviations

Coupling tolerance If coupling to SMF: same for all types of taperCoupling to high-NA fiber: lower


Fiber-chip couplingRegular taper

Difficult to fabricate

Multi-mode

Facet coating required


Coupling to fiberInverse taper

Broad wavelength range

Single mode

Easy to fabricate (if you can do the tips)

Low facet reflections

0.4µm

80nm

0.2µm

500 µm

polished facet


Coupling to fiber

3x32x002x2

Cladding Size

0.8Polymer60.0200.0 300300NTT< 4dBSiO2100.040.0 470270Cornell< 1dBPolymer75.0150.0 445220IBM

tbdPolymer500220IMEC

LossCladding Material

tip width [nm]

L [um]

w [nm]

h [nm]

Group

0.4µm

80nm

0.2µm

500 µm

polished facet


Coupling to fibreTip fabrication

EBeam

Modified DUV (resist trimming)

220nm


spot size convertor

Single modefiber core

Coupling to fiberThe vertical fiber coupler

use a grating to couple light from/to a fiber perpendicular to the PIC

use a spot-sizeconvertor in plane

wafer scale, no need to cleave/polish the devices

good alignment tolerances

relatively broadband

works for TE only

(artist’s impression)


Out-of-plane coupler

What is new ?Other grating couplers

long (>100µm)

very narrow bandwidth

couple in and out

high efficiency (>50%)

Our grating couplershort (10µm)

bandwidth > 50nm possible

couple in and out

high efficiency ?

Grating couplers :‘Second’ order grating (Λ=λ /neff)

First order diffraction couples light out of the waveguide producing a surface normal propagating field


Fabricated DevicesAlternative: Grating couplers

Waferscale testing

Waferscale packaging

High alignment tolerance

deep trench

shallow fibre coupler

Towards optical circuit


From Fibre

-40

-35

-30

-25

-20

-15

-10

-51500 1520 1540 1560 1580 1600

Tran

smis

sion

[dB

]

Wavelength [nm]

∆λ1dB = 35nm


-60

-55

-50

-45

-40

-35

-30

-25

-20

-151500 1510 1520 1530 1540 1550 1560 1570 1580 1590 1600

wavelength [nm]

T [d

B] passdrop

bcb cladding, ring resonator with bend coupling, R=8µm


Fiber CouplersCoupling light from waveguide to optical fiber on top


Experimental results

33% efficiency (4.8dB coupling loss)35-40nm 1dB bandwidth

0.00

0.10

0.20

0.30

0.40

1520 1560 1600 1640

wavelength (nm)

fiber

cou

plin

g ef

ficie

ncy

620nm period630nm period620nm theory630nm theory


2D grating fiber couplerFiber to waveguide interface for polarisationindependent photonic integrated circuit

2D grating

couples each fiber polarisationin its own waveguide

in the waveguides the polarisation is the same (TE)

Allows for polarisationdiversity approach

patent



Experimental resultsFabrication

SOI: 220nm Si / 1000nm SiO2Etch depth: 90nm

Square lattice of holes: 580nm period


Optical Ring ResonatorsOptical Ring Resonators

For a given loss: trade-offHigh Q Low coupling

ButLow coupling Low drop efficiency !!!

Relevant Characteristics:• Free Spectral Range (Period)• Quality Factor

Determined by:• Coupling ratio• Round-trip loss• Length (=radius)


Optical Ring Resonator

1um

5um


Optical Ring Resonators

-60.00

-50.00

-40.00

-30.00

-20.00

-10.00

1520 1540 1560 1580

Ring resonator demux4 rings in series

Linearly increasing radius

λc does not increase linearly as expected !!

Fabrication problem: mask discretisation

Solution: vary parameter which is less sensitive to fabrication

Other:Peak splitting due to reflections


Increasing Index ContrastLow Contrast - Fiber Matched

(silica or polymer based)Bend Radius ~ 5 mmSize ~ several cm^2

Medium Contrast (InP-InGaAsP)

Bend Radius ~ 500µm

5 mm

Ulra-high Contrast (SOI based)

Bend Radius < 50µm

200

µm

5 cm


AWG DesignVarious devices were designed :

∆ν = 400GHzFSR = 8 x 400GHzw = 0.5µm# arms = 18 or 24R = 75µm ~ 150µmwi = 0.6µm ~ 1.0µmwg = 0.6µm ~ 1.0µmg = 0.2µm

200µm To gratingcouplers

R

wg

wiw

All designs fabricated with different exposure doses (during litho)

different actual waveguide widths

wg

wi

g


200µmAWG ResultsAWG, 400GHz spacing, 8 channels

∆ν = 340GHz 360GHz (different exposure times)8dB on-chip loss

-25

-20

-15

-10

-51500 1520 1540 1560 1580 1600

Tran

smis

sion

[dB

]

Wavelength [nm]


O2

-25

-20

-15

-10

-51500 1520 1540 1560 1580 1600

200µmAWG Results5 x 8 AWG, 400GHz spacing, 8 Channels

300µm x 300µm area8dB on-chip loss6-10 dB crosstalk

Tran

smis

sion

[dB

]

Wavelength [nm]

7dB


AWGYokohama Nat. University

(Fukazawa, Ohno, Baba, Jap. J of Appl. Physics, ’04)


AWG Crosstalk OriginPossible reasons for crosstalk

“Overspill” in star-coupler

Reflections in star-coupler

Phase errors in grating arms


AWG Crosstalk OriginPhase errors in Waveguide arms ?

Assume standard deviation for phase-error given by :

ic

Lfi

πσφ1

=

Cro

ssta

lk L

evel

[dB

]

fc

Calculated Crosstalk vs. fc

Correlation length [µm]0.01 0.1 1 10 100 103 104

Rou

ghne

ss[n

m]

5

10

fc=100

fc

fc=100


-25.00

-20.00

-15.00

-10.00

-5.00

0.00

1520.00 1530.00 1540.00 1550.00 1560.00 1570.0

Cascaded MZ FilterExample: 5 stage CMZ

3.2nm bandwidth

17nm FSR

coupling efficiency ~80%

-10 dB crosstalk

wavelength [nm]no

rmal

ized

out

put [

dB]

pass

drop

20µm 14µm 20µm 20µm 14µm 20µm

∆L = 32.8µm

gap width = 220nm

waveguide width= 535nm



PICCO04: Cascaded MZ FilterExample: 5 stage CMZ

2.6nm bandwidth

17nm FSR

coupling efficiency ~100%

-10 dB crosstalk-25.00

-20.00

-15.00

-10.00

-5.00

0.00

1520.00 1530.00 1540.00 1550.00 1560.00 1570.0

wavelength [nm]no

rmal

ized

out

put [

dB]

pass

drop

26µm 14µm 20µm 20µm 14µm 26µm

∆L = 32.8µm

gap width = 220nm




Optical ProximityEffectsOptical Lithography

Images of neighbouringstructures interfere

Effect can be additiveof subtractive

= optical proximity effects

Example:isolated line width: 565

gap width: 220nm

line width in coupling section: 535nm

wg

wi

wc

W. Bogaerts et al. to be published in JLT (Oct 2004)


ConclusionsSub-micron SOI-waveguides:

Powerful platform for high-density Photonic circuitsWe have all basic building blocs (and no need for these complicated Photonic Crystals)

Fabrication issues to be solvedOptical proximity (narrow lines, fine gaps)Phase-Errors, control central wavelength of devicesFurther reduction losses needed ?

Next step: active functionality ?

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Submicron SOI waveguides - UGentphotonics.intec.ugent.be/download/ocs63.pdf · 2005. 3. 11. ·...

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