® © 2003 intel corporation silicon photonics applications research results & integration...

®

© 2003 Intel Corporation

Silicon Photonics Applications Research Results & Integration Challenges

Berkley Lecture Series: 4/27/04

Silicon Photonics Applications Research Results & Integration Challenges

Berkley Lecture Series: 4/27/04

Mario Paniccia, PhD.Mario Paniccia, PhD.

Director Photonics Technology LabDirector Photonics Technology Lab

Intel CorporationIntel Corporation

®


Acknowledgements:Acknowledgements:

Drew Alduino, Sean Koehl, Richard Jones, Drew Alduino, Sean Koehl, Richard Jones, Ansheng Liu, Ling Liao, Mike Morse, Mike Salib, Ansheng Liu, Ling Liao, Mike Morse, Mike Salib, Dean Samara-RubioDean Samara-Rubio Oded Cohen, Doron Rubin, Assia BorkaiOded Cohen, Doron Rubin, Assia Borkai

• 3 •Communications TechnologyCommunications Technology

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OutlineOutline

Microprocessor Performance TrendsMicroprocessor Performance Trends Applications for opticalApplications for optical Interconnect Requirements Interconnect Requirements Silicon Photonics: Silicon Photonics:

Recent ResultsRecent Results Integration challengesIntegration challenges

SummarySummary


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Moore’s Law Scaling: Moore’s Law Scaling:

4004400480808080

80868086

80088008

Pentium® ProcessorPentium® Processor

486™ DX Processor486™ DX Processor386™ Processor386™ Processor

286286

Pentium® II ProcessorPentium® II Processor

Pentium® III ProcessorPentium® III Processor Pentium® 4Pentium® 4ProcessorProcessor

Itanium® 2 ProcessorItanium® 2 Processor

1,0001,000

10,00010,000

100,000100,000

1,000,0001,000,000

10,000,00010,000,000

100,000,000100,000,000

1,000,000,0001,000,000,000

19701970 19801980 19901990 20002000 20102010

~ 1Billion transistors by end of decade~ 1Billion transistors by end of decade

Microprocessor transistor countMicroprocessor transistor count

Source: IntelSource: Intel


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Microprocessor PerformanceMicroprocessor Performance

Microprocessor clock frequency Microprocessor clock frequency trending to ~ 10GHz end of decadetrending to ~ 10GHz end of decade

Microprocessor clock frequency Microprocessor clock frequency trending to ~ 10GHz end of decadetrending to ~ 10GHz end of decade

Microprocessor Clock FrequencyMicroprocessor Clock Frequency

0.10.1

11

1010

100100

1,0001,000

10,00010,000

19701970 19801980 19901990 20002000 20102010

MHzMHz

Pentium® 4 ProcessorPentium® 4 Processor

Pentium® III ProcessorPentium® III ProcessorPentium® II ProcessorPentium® II Processor

Pentium® ProcessorPentium® Processor486™ Processor486™ Processor

386™ Processor386™ Processor286286

80868086

80858085

8080808040044004

Source: IntelSource: Intel


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PC or “Datacom” Economics:PC or “Datacom” Economics:

MIPSMIPS

PentiumPentium®®

ProcessorProcessor

PentiumPentium® ® ProProProcessorProcessor

PentiumPentium® ® IIIIProcessorProcessor

PentiumPentium® ® IIIIIIProcessorProcessor

PentiumPentium® ® 44ProcessorProcessor

Intel386Intel386TM TM DXDXMicroprocessorMicroprocessor

Intel486Intel486TMTM DX DX CPU CPU

MicroprocessorMicroprocessor

1

10

100

1000

10000

19851985 19891989 19931993 19951995 19971997 19991999 20012001

MIPS

$/MIPS$/MIPS

0.01

0.1

1

10

100

$/MIPS

1991199119871987

Higher Performance, Lower Cost


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OutlineOutline



SummarySummary


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Chip to Chip1 – 50 cm

Board to Board50 – 100 cm

Copper (FR4)

Communication ApplicationsCommunication Applications

Shorter Distances

1 to 100 m

Rack to Rack

Copper/ FiberFiber

0.1 – 80 km

SONET

FiberChannel

Ethernet


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Chip to Chip1 – 50 cm

Board to Board50 – 100 cm

Copper (FR4)

Interconnect ApplicationsInterconnect Applications

Shorter Distances

1 to 100 m

Rack to Rack

Copper/ FiberFiber

0.1 – 80 km

SONET

FiberChannel

Ethernet


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OPTICALOPTICAL

Electrical to Optical: Bandwidth vs Cost Electrical to Optical: Bandwidth vs Cost

20042004 2010+2010+

ELECTRICALELECTRICAL

EnterpriseEnterpriseDistance: 0.1-Distance: 0.1-10km10km

Rack-RackRack-RackDistance: 1-100mDistance: 1-100m

Board-BoardBoard-BoardDistance: 50-Distance: 50-100cm100cm

Chip-ChipChip-ChipDistance: 1-50cmDistance: 1-50cm

3.125G 10G 3.125G 10G 40G 40G

3.125G 5-6G3.125G 5-6G 10G 10G 20G 20G

3.125G 5-6G3.125G 5-6G 10G 10G 15-20G 15-20G

Copper to optical transition is cost-driven

10G 10G >= 40G >= 40G

Cu TechnologyCu Technology(B/W)(B/W)

Optical CostsOptical Costs

Transition Zone

Transition Zone

Silicon Photonics?


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OutlineOutline

Microprocessor Performance TrendsMicroprocessor Performance Trends Applications for opticalApplications for optical Interconnect RequirementsInterconnect Requirements Silicon Photonics: Silicon Photonics:


SummarySummary


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Interconnect: Most StringentInterconnect: Most Stringent

HardDrives

PCIExpress

ATA

CPU

Front side bus*

USB 2.0

PeripheralDevices

LAN

MCHMemory

Controller Hub

ICHI/O

Controller Hub

MemoryAGP4X

Monitor

Memory bus*Graphics

bus

Computer Interconnect

Estimated High Level costs

Requirements for 2010+ : • Data rates > 15 Gb/s per channel • BER < 10^ -13• Voltage < 5 V• Low power consumption ideally <100mW • Distances <25 inches• Cost/link < $5


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OutlineOutline


Opportunity & Recent ResultsOpportunity & Recent Results Integration challengesIntegration challenges

SummarySummary


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Opportunity for Silicon PhotonicsOpportunity for Silicon Photonics Take advantage of enormous (billions $$) of silicon

infrastructure and process learning Most tools exist: Lithography requirements do not

push leading edge (ie no 90nm litho) Integration opportunity to combine multiple optical

devices together (potential cost savings) Can use Silicon as workbench to assist with

packaging and alignment Opportunity to converge communication and

computing all on one platform..

Could provide PC like economics to Photonics Could provide PC like economics to Photonics However… many issues and challenges…However… many issues and challenges…


LabLab


LaserFilter

(adds tunability)Photo

ReceiverModulator

(improved encoding)

DATA

OpticalFiber

1 0 1

Elements of an Optical Link

ReceiverTransmitter

+ + TransimpedanceTransimpedance

Amplifier (TIA)Amplifier (TIA)

+ Drive+ DriveElectronicsElectronics


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1. Light Source

2. Guide Light

3. Fast Modulation

4. Light Detection

5. Low-cost Assembly

6. Intelligence

Low-cost External Laser

Si on Insulator (SOI) WG

Si MOS Capacitor Device

Si Based Photodetector

Si Passive Alignment

Si CMOS Circuitry

REQUIREMENT OUR SOLUTION

Requirements for “Siliconizing” Photonics

Requirements for “Siliconizing” Photonics


LabLab


TIATIA

TIATIA

DriversDrivers

CMOSCMOSCircuitryCircuitry

Vision: Integrated Photonic ChipConvergence of Communication and Computing

PhotodetectorPhotodetector

PassivePassiveAlignmentAlignment

ModulatorModulatorECLECL

FilterFilter MultipleMultipleChannelsChannels


LabLab


2) Guide Light

Wave-guides Tapers

Splitters

Switches,Couplers,& others

1) Light Source

External Cavity LaserLight Source

4) Detect Light

Photo-Detector

Components for SiliconizationComponents for Siliconization

6) Intelligence

CMOSCMOS

3) Fast Modulation

SiliconModulator

5) Low Cost Assembly

PassiveAlignment


LabLab


Photon Energy and Silicon Transparency

Photon Energy and Silicon Transparency

Ultra Violet (UV)

VisibleNear IR Far IR

Infra Red (IR)

E=hc/

Intel Litho

Photon Energy (eV) → 2.76 1.55 1.1eV 0.41Wavelength (µm) → 0.45 0.8 1.12µm 3.0

Silicon Opaque Silicon Transparent

Si Bandgap


LabLab


Guiding Light with Si WaveguidesGuiding Light with Si Waveguides

•Use silicon fabrication techniques to etch optical channels •The light is confined in the top Si layer between oxide layers•High index contrast (>2.5) allows for small bend radii

Rib waveguide

Silicon

oxide

SEM IMAGESSiliconoxide


LabLab


2) Guide Light

Wave-guides Tapers

Splitters


1) Light Source


4) Detect Light

Photo-Detector


6) Intelligence

CMOSCMOS

3) Fast Modulation

SiliconModulator


PassiveAlignment


LabLab


RESULTS: ModulatorRESULTS: Modulator Fast Modulators (>10GHz) exist, but use exotic

materials InP, Lithium Niobate etc

Fastest Si modulator to date was ~20MHz

Intel’s recent Research Breakthrough: Scalable 1GHz B/W silicon modulator

50 times faster than previous research attempts Published in the journal Nature on Feb-12, 2004

Uses novel “transistor-like” phase shifting device Simulations show this can scale to greater than 10GHz

Eliminates a significant barrier to making Photonic Devices in SiliconEliminates a significant barrier to making Photonic Devices in Silicon


LabLab


Modulator ConceptMach Zehnder Interferometer (MZI)Modulator ConceptMach Zehnder Interferometer (MZI)

Y coupler Y coupler/2

Silicon die

MZI Converts Phase shift into amplitude modulation

Optical Phase-Shifter

AmplitudeModulated

out

CW in

/2


LabLab


Novel Intel Capacitor Phase-shifterNovel Intel Capacitor Phase-shifter

Device x-section is transistor-like & operates in accumulation mode Uses Majority carriers, so speed is determined by RC only

•R controlled by doping, •C controlled by WG geometry and gate thickness

Trade off in size reduction, doping, and speed

oxide

Silicon

n-type Si

+

Gate Oxide p-type Polysilicon

OxideSilicon

Oxide

p-type Polysilicon

smkoehl

replace laser icon w/ new


LabLab


Results: Phase vs Voltage (Active L: SOI h=1.4um, Poly .9um , Gox=120A)Results: Phase vs Voltage (Active L: SOI h=1.4um, Poly .9um , Gox=120A)

Moving to 60A Drive voltage can move to 3V

= 2nL/

indexncharge

N=0r/(etoxt)[VD-VFB]

Vfb~ 1.2V

Modeling

0 2 4 6 8 10

0.0

0.2

0.4

0.6

0.8

1.0 L=1.0 mm L=2.5 mm L=5.0 mm L=8.0 mm

Ph

ase

sh

ift

()

Drive voltage VD (V)

Vfb

Based on Plasma Optical Effect


LabLab


Results: MZI-modulatorResults: MZI-modulator L = 16.7L = 16.7m; 42nm FSR m; 42nm FSR (testing convenience)(testing convenience) Optical Loss:Optical Loss:

Passive WG 1.0 dB/cmPhase-shifter 5.1 dB/cm

Small-signal measurementsSmall-signal measurements Large-signal modulatorLarge-signal modulator

Phase shifters

Light

1cm

Light

2.5mm

Phase shifter

6.7 dB on-chip loss6.7 dB on-chip loss


LabLab


0.1 1-5

-4

-3

-2

-1

0

1

3 dB line

Opt

ical

res

pons

e (d

B)

Frequency (GHz)

0.1 110-4

10-3

10-2

On-chip voltage (V

)

Pho

to-r

ecei

ver o

utpu

t (V

)

Frequency (GHz)

10-2

10-1

100

Small Signal Frequency ResponseSmall Signal Frequency Response

Normalize 3 dB Rolloff ~2.5GHz

Small signal response (.5Vp-p)

Normalized frequency response


LabLab


Large-signal ModulatorLarge-signal Modulator MZI has 1cm phase MZI has 1cm phase

shifter in each armshifter in each arm

Cap. load requires Cap. load requires parallel drive parallel drive

Bank of 8 differential Bank of 8 differential ECL buffersECL buffers

1.6V1.6Vpp pp

~5.8dB ER expected ~5.8dB ER expected

PRBS Source

CW in via lensed fiber. Polarization is controlled. MZI biased to quadrature by tuning . (FSR ~ 42nm)

3mm

+ -

Light output collected w/ lensed fiber DC-coupled 15GHz receiver


LabLab


Modulation Result: 1Gb/s Modulation Result: 1Gb/s Achieved 5dB RF extinction ratio Achieved 5dB RF extinction ratio Clearly recoverable 1Gb/s PRBS patternClearly recoverable 1Gb/s PRBS pattern

0.00

0.07

0.14

0.21

0.28

0.35

0 10 20 30 40 50Time (ns)

Pho

tore

ceiv

er O

utpu

t (V

)

70mV

225mV

PRBS Source Voltage (arb. units)

Extinction Ratio ~ 5dB


LabLab


2) Guide Light

Wave-guides Tapers

Splitters


1) Light Source


4) Detect Light

Photo-detector


6) Intelligence

CMOSCMOS

3) Fast Modulation

SiliconModulator


PassiveAlignment


LabLab


Silicon-based Photodetectors

Adding germanium to silicon pushes the onset of detection to longer wavelengths useful for data communication

Silicon is a good detector for visible light (used in CCD cameras)silicon is transparent to infrared : need to change band gap

Si

Ge

Silicon

Siliconoxide

Gen-Si

I

p-Si


LabLab


Previous Work on SiGe PhotodetectorsPrevious Work on SiGe PhotodetectorsReference Structure Efficiency Dark Current

Luyri et al. Ge p-i-n ex=40%@1.45 m 50 mA/cm2

Temkin et al. SiGe MQW pin int=40%@1.3 m 7 mA/cm2

Huang et al. SiGe MQW ex= 1%@1.3 m 60 mA/cm2

Huang et al. SiGeC ex= 1%@1.3 m 7 mA/cm2

Shuppert et al. SiGe MQW pin ex= 11%@1.3 m 1 mA/cm2

Samavedam et al. Ge pn diode ex= 13%@1.3 m 0.15 mA/cm2

Colace et al. Ge MSM ex= 23%@1.3 m 100 mA/cm2

Li et al. SiGe MQW pin ex= 1%@1.3 m no data

Oh et al. Ge pin ex= 49%@1.3 m 400 mA/cm2

Bauer et al. SiGe pin ex= 1%@1.3 m 40 mA/cm2

Goal SiGe pin waveguide ex=50% @1.3 m 1 mA/cm2

None of these have the desired performance and manufacturability to be commercially feasible.


LabLab


Preliminary Photodetector Results

100Mb/s pseudo-random optical data detected at 1319nm

Source: Intel Corporation


LabLab


2) Guide Light

Wave-guides Tapers

Splitters


1) Light Source


4) Detect Light

Photo-detector


6) Intelligence

CMOSCMOS

3) Fast Modulation

SiliconModulator


PassiveAlignment


LabLab


Low cost assembly: Passive AlignmentLow cost assembly: Passive Alignment

FIBER

WAVEGUIDE

WAVEGUIDE

GROOVE

GROOVE

• Assembly is 1/3-2/3 the cost of optical components

• Active alignment means light on and optimizing power

• Complex, time consuming, expensive

• Passive Alignment uses lithographically + silicon to align

Fiber Attach Laser Attach 45 deg facet


LabLab


Etched FacetEtched Facet •Develop a high quality waveguide facet etch (using a multi Develop a high quality waveguide facet etch (using a multi step etch recipe)step etch recipe)

• Deposit AR coating on Facet Deposit AR coating on Facet

..

Metallization IssuesMetallization Issues •Develop a metallization process with high bond strength Develop a metallization process with high bond strength

SOI Waveguide

Silicon Substrate

Challenges Challenges

Laser Diode


LabLab


AccomplishmentsAccomplishmentsAchievements: Achievements:

Au electroplating developed for 2.5Au electroplating developed for 2.5m bump with good m bump with good

uniformityuniformity..

Successfully electroplated 5x10Successfully electroplated 5x10m and 4x8m and 4x8m bumpsm bumps


LabLab


First Bonding ResultsFirst Bonding Results

Mechanical die have been bonded to a patterned siliconwafer with 2.5m

thick electroplated Au bumps and

sheared off

0.5 mm

1 mm

0.25 mm


LabLab


First Passively Aligned Laser DiodeFirst Passively Aligned Laser Diode

Top View

Output WaveguideFacet

Laser diode

ElectricalProbe

waveguide


LabLab


Output Waveguide Facet

Laser OFF

Output Waveguide Facet with passively aligned LD

Laser ON

First Passively Aligned Laser Diode


LabLab


Planar waveguide filtersPlanar waveguide filtersFiltersFilters Bragg filters ~ 2mm long x 2.5um wideBragg filters ~ 2mm long x 2.5um wide

Made from alternating polycrystalline Made from alternating polycrystalline silicon with crystalline silicon in waveguide silicon with crystalline silicon in waveguide ((n~0.01) narrow reflection bandn~0.01) narrow reflection band

70% reflectivity70% reflectivity 20dB extinction ratio20dB extinction ratio Stop band 0.5 - 5nmStop band 0.5 - 5nm Thermally tunable 12-nm/100-CThermally tunable 12-nm/100-C

ECLECL Used Bragg filters to wavelength stabilize Used Bragg filters to wavelength stabilize

external cavity laser external cavity laser Showed POC single mode ECLShowed POC single mode ECL Tunability same as gratingTunability same as grating Current researching SiON Bragg filters for Current researching SiON Bragg filters for

temperature stable devicetemperature stable device

Silicon / Poly silicon Bragg grating~ 0.5nm reflection band

Tuning of silicon based ECL with temperature

-25

-20

-15

-10

-5

0

1540 1545 1550 1555 1560

Wavelength (nm)

Op

tica

l po

wer

(d

B)

Silicon

Poly Silicon

-70

-60

-50

-40

-30

-20

-10

0

1538 1540 1542 1544 1546 1548

wavelength / nm

ou

tpu

t /

dB

m

25.6 C

29.5 C

34.8 C

39.9 C

47.1 C

52.6 C

59.6 C

66.6 C

71.1 C


LabLab


Coupling to Planar waveguide devicesCoupling to Planar waveguide devices

Coupling lossCoupling loss

Solution to large coupling Solution to large coupling loss is to taper from large loss is to taper from large input waveguide to smaller input waveguide to smaller bus waveguidebus waveguide

Showed Showed decreasedecrease in coupling in coupling loss to loss to 1.5dB/interface1.5dB/interface

Taper from 8umx8um to 2.5umx2.5um

THIS IS BIG CHALLENGE FOR SILICON PHOTONICS


LabLab


TIATIA

TIATIA

DriversDrivers

CMOSCMOSCircuitryCircuitry

Vision: Integrated Photonic ChipsConvergence of Communication and Computing

PhotodetectorPhotodetector

PassivePassiveAlignmentAlignment

ModulatorModulatorECLECL

FilterFilter MultipleMultipleChannelsChannels


LabLab


Integration Challenges w/CMOS FabricationIntegration Challenges w/CMOS Fabrication

Photonic IntegrationPhotonic Integration

Electronic (logic) & Photonic: Electronic (logic) & Photonic:


LabLab


Integrated solution must perform better or lower cost than sum of discrete components

Integration just for the sake of integration is not always good thing

Integration: Photonic Only Integration: Photonic Only

Monolithic integration of multiple optical devices has advantages:

1) Potential reduction in time and cost for testing vs hybrid 2) Litho alignment can reduce interface losses vs hybrid3) Packaging of one die vs multiple devices 4) New form factor/functionality that discrete devices may not provide

In the end though its all about balancing complexity vs yield


LabLab


Integration: Photonic & ElectronicIntegration: Photonic & Electronic

1) Process compatibility: • @ 10Gb/s CMOS IC’s need 90nm technology. • Silicon Photonic devices may only need ~.25um.

2) Yields: • Typical industry IC yields are very high, but the process windows are

extremely tight.• Combining photonics and CMOS could exceed thermal budget, DOF, and other processing guidelines, thereby reducing IC yield.

3) Potential for performance improvement at very high speeds

Size, form factor, power, performance & cost all factor into choosing Monolithic or Hybrid approach


LabLab


SummarySummary• Silicon Photonics could provide opportunity bring PC

economics to photonic industry

• Recent Results with silicon modulator have shown silicon to possibly be considered and optical material

• To be practical one must consider the integration challenges that will be encountered to produce these devices.

• In line wafer testing is big gap for HVM optical devices

• Electronic and photonic integration will be very challenging…


LabLab


Optical Modulator ReferencesOptical Modulator References

Ansheng Liu, Richard Jones, Ling Liao, Dean Samara-Rubio, Doron Rubin, Oded Ansheng Liu, Richard Jones, Ling Liao, Dean Samara-Rubio, Doron Rubin, Oded Cohen, Remus Nicolaescu, and Mario Paniccia, Cohen, Remus Nicolaescu, and Mario Paniccia, A high-speed silicon optical A high-speed silicon optical modulator based on a metal–oxide–semiconductor capacitormodulator based on a metal–oxide–semiconductor capacitor, , NatureNature 02/04 02/04

Tang, C. K. & Reed, G. T.Tang, C. K. & Reed, G. T., Highly efficient optical phase modulator in SOI , Highly efficient optical phase modulator in SOI waveguides. waveguides. Electron. Lett.Electron. Lett. 31, 451–452 (1995).31, 451–452 (1995).

Dainesi, P. Dainesi, P. et al.et al. CMOS compatible fully integrated Mach-Zehnder interferometer in CMOS compatible fully integrated Mach-Zehnder interferometer in SOI technology.SOI technology. IEEE Photon. Technol. Lett. IEEE Photon. Technol. Lett. 12, 660–662 (2000).12, 660–662 (2000).

Irace, A., Breglio, G. & Cutolo, A.Irace, A., Breglio, G. & Cutolo, A. All-silicon optoelectronic modulator with 1 GHz All-silicon optoelectronic modulator with 1 GHz switching capability. switching capability. Electron. Lett.Electron. Lett. 39, 232–233 (2003). 39, 232–233 (2003).

Hewitt, P.D.,Hewitt, P.D., Reed, G.T., Reed, G.T., Improving the response of optical phase modulators in Improving the response of optical phase modulators in SOI by computer simulation,SOI by computer simulation, J. Lightwave Technol. J. Lightwave Technol. 18, 443-450, (2000).18, 443-450, (2000).

Miller, D.A.B., Weiner, J.S., and Chemla, D.S.,Miller, D.A.B., Weiner, J.S., and Chemla, D.S., Electric field dependence of linear Electric field dependence of linear optical properties in quantum well structures: waveguide electroabsorption and optical properties in quantum well structures: waveguide electroabsorption and sum rules. sum rules. IEEE J. of Quantum Electron.IEEE J. of Quantum Electron. QE-22, 1816-1830 (1986) QE-22, 1816-1830 (1986)

Wooten, E. L. et al.Wooten, E. L. et al. A review of lithium niobate modulators for fiber-optic A review of lithium niobate modulators for fiber-optic communications systems. communications systems. IEEE J. Select. Topics Quant. Electron.IEEE J. Select. Topics Quant. Electron. 6, 69–82 (2000).6, 69–82 (2000).


LabLab


Silicon Photonics ReferencesSilicon Photonics References

Book: Silicon Photonics an Introduction by Graham T Reed , Book: Silicon Photonics an Introduction by Graham T Reed , Andrew Knights (Wiley) . March 2004Andrew Knights (Wiley) . March 2004

Silicon Photonics. Springer series topics in Applied Physics L. Silicon Photonics. Springer series topics in Applied Physics L. Pavesi, D. Lockwood (due out April 2004) Pavesi, D. Lockwood (due out April 2004)

For more info on Intel Research in Silicon Photonics , please visit: For more info on Intel Research in Silicon Photonics , please visit: www.intel.comwww.intel.com/technology/sp/technology/sp

® © 2003 intel corporation silicon photonics applications research results & integration...

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