Bergur Gudbergsson Zach Whitney Marcus Hale As the data transfer limits of conventional electric interconnects are approached emerging onchip optoelectric solutions look promising as means of keeping up with increased processing power efficiency and bandwidth requirements This prese ID: 355273
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Optoelectronic Integration
Bergur GudbergssonZach WhitneyMarcus Hale
As the data transfer limits of conventional electric interconnects are approached, emerging on-chip optoelectric solutions look promising as means of keeping up with increased processing power, efficiency, and bandwidth requirements. This presentation will explore fiber optics, vertical-cavity surface emitting lasers (VCSEL), optical interconnects, and photodiodes.
05/05/14
1Slide2
Outline
Fiber OpticsBasics of FiberFiber typesOptical PowerTransmission BandsWave Division Mux
PIN PhotodiodeAbsorptionEnergy Band DiagramsApplicationsVCSELBasic OperationStructure
VCSEL-PIN TRx function & fabricationOptical InterconnectsBasic operation
2Slide3
The Basics of Fiber
3A fiber cable consists of:CoreCladding
BufferJacket“Total Internal Reflection”Slide4
4
4
Cladding
has lower refractive index than the
core which
causes
total internal reflection
within the coreSlide5
Fiber Types
5Two main types of fiber optics cablesSingle Mode Fiber (SMF) (9μM)
Multi Mode Fiber (MMF) (62.5μM or 50μM)Slide6
Single Mode Fiber
6Small core carries single mode of lightNo modal dispersion
Long-haul data transmissionRequires expensive coherent laser light sourceRequires specific connector alignmentOperates in 1.3μM -1.5μM RegionSlide7
Multi Mode Fiber
7Multiple modes of light can propagateModal dispersion limits distance (500 meters)Uses cheaper light sources
LEDVCSELLarger alignment tolerancesTypically operates at 0.85μMSlide8
Optical Power
8Light follows “inverse square law”inversely proportional to distance squaredAttenuation = loss of intensity
Measured in Decibel-milliWatts (dBm /dBmW)0dBm is 1 mW3dBm is 2
mW-50dBm is 10 nWSlide9
Transmission Bands
9Split into four windows850nMHigh attenuation
1310nMZero modal dispersion for SMFUp to 10kM reach1550nM (Conventional-band)Amplified via erbium doped fibers1570-1610nm (Long-band)Slide10
10Slide11
Typical Mux/
Demux System
Multiple signals are generatedMultiplexer combines the lights into a signal carrier signalSignal is transmittedλν=
cSignal is re-separatedSignal is received
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PIN Photodiodes
Photodiodes with an Intrinsic (undoped) region between highly doped P and N junctions.
Anti-reflection (1/4 wavelength)
12Slide13
Absorption
Photons Absorbed in the intrinsic regionCreates CarriersIncreases Photocurrent (Light into Current)Si: infrared(700nm) up to 1μmInGaAS: up to 1.7μm (Longer wavelengths)
13Slide14
Electron-Hole Pair Generation
14Slide15
Energy band Diagram
InGaAs
15Slide16
Energy band
Diagram PIN-Si
16Slide17
Applications
Optical fiber communicationsSecurity SystemsCamerasLight Controls
http://www.hamamatsu.com/cs/Satellite?blobcol=urldata&blobheadername1=content-disposition&blobheadervalue1=inline%3Bfilename%3D149%2F656%2Fk_s1226-44bq_bk_-5bq_bk_pp_xx.jpg&blobkey=
id&blobtable=MungoBlobs&blobwhere=1328686465431&ssbinary=true
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Fiber Optic Link
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Camera Brightness Metering
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Smoke Detector
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Introduction to VCSELs
Vertical Cavity Surface Emitting LasersDifferent from typical Laser DiodesLaser is perpendicular to the surface.P and N doped regions act as parallel DBR mirrors, also forming a diode junction.Multiple quantum wellsAble to arrange in dense 1 or 2D, on-chip arrays.
21Slide22
History of VCSELs
1979 first device using GaInAsP/InP1988 first continuous wave using GaAs
Today, GaAs-AlGaAs material is favored, 850nm wavelength used for short-haul data communication (monolithic TRx)
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VCSELs Basic Structure
Typical Laser Diode
VCSEL
23Slide24
VCSEL Array
24Slide25
VCSEL technology
25Slide26
VCSEL technology
26Slide27
VCSEL-PIN TRx
Monolithic transceiver chips coupled with MMFMiniaturization only possible with PIN PDWhy?Data Rates in the 10-Gb/s rangeArrays allow Optical Interconnects even higher rates
27Slide28
VCSEL-PIN TRx
Fabrication
Two stacks of MBE layersPIN PD grown in the same run of the VCSEL layers.Order is important28Slide29
VCSEL-PIN TRx
29Slide30
VCSEL-PIN TRx
30Slide31
VCSELs
PROSEasy testing throughout fabricationHigh reflectivity mirrors
Reduced threshold current (down to the 10’s of uA)Low power consumptionCONS
Poor thermal characteristics at high-power (980nm+)Increased heat increases threshold current
Reduced output at high-power
Reduced output at longer wavelengths
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Correcting Thermal Issues in VCSELs
Experiments with various passivation layersSiO2 (dated)High resistivity and insulationPoor heat conductivity (1W/mK)
AlN (new fabrication)High resistivityHigh heat conductivity (300W/mK)Increased temp distribution, reduces thermal resistanceCarbon Nanotubes (future?)
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Correcting Thermal Issues in VCSELs
33Slide34
Correcting Thermal Issues in VCSELs
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Final Thoughts on VCSELs
VCSLEs experiencing huge growth as electrical interconnects slowly become obsoleteVCSELs are attractive for short-haul, large data transfersCan densely back in 1D & 2D array allowing for increased output as well as easy packagingGreat, and basically only choice for optical interconnects
35Slide36
Brief Overview of Optical Interconnects
36Slide37
Brief Overview of Optical Interconnects
AdvantagesKeep up with Moore’s LawHigher carrier frequencyLess crosstalkLower power consumptionData ranges in the range of Tb/s
http://www.youtube.com/watch?v=0U4Af2qmgFA (similar but using silicon based lasers)37Slide38
Conclusion
All of these optoelectrical innovations contribute to the growing field of optical interconnection technologyImmensely complex, research still underwayHuge growth potential
38Slide39
References
Arshad, T. S., Othman, M. A., & Yasin, N. Y. Comparison on IV Characteristics Analysis between Silicon and InGaAs PIN Photodiode.
IEEE (ICICI-BME), 71-75. Retrieved May 1, 2014, from http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6698467Introduction to DWDM For Metropolitan Networks. (2000). San Jose, CA: Cisco Systems, Inc.
Kenichi, I. VCSEL -Its Conception, Development, and Future-. IEEE (MOC' 13), 1-2. Retrieved May 1, 2014, from http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6715057
Kern, A., Al-
Samaneh
, A., Wahl, D., &
Michalzik
, R. Monolithic VCSEL–PIN Photodiode Integration for Bidirectional Optical Data Transmission.
IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS
,
19
, 1-13
.
Lifeng, H., Yongfeng
, M., & Yuan, F. Fabrication and Testing of 980nm High-Power VCSEL with AlN Film Passivation Layer. IEEE (ICOM)
, 45-48. Retrieved May 1, 2014, from
http://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=6316212
39Slide40
References
Mishra, S., Chaudhary, N., & Singh, K. Overview of Optical Interconnect Technology. International Journal of Scientific & Engineering Research, 3, 1-7. Retrieved May 1, 2014, from
http://arxiv.org/abs/1303.3954Muramoto, Y., & Ishibashi, T. InP=InGaAs pin photodiode structure
maximising bandwidth and efficiency. ELECTRONICS LETTERS, 29.
Paschotta
, D. R. (
n.d.
). p–
i
–n Photodiodes.
Encyclopedia of Laser Physics and Technology
. Retrieved May 1, 2014, from http://www.rp-photonics.com/p_i_n_photodiodes.html
Paschotta
, R. (
n.d.). Passive Fiber Optics. Tutorial “”: multimode fibers, number of modes, core diameter, numerical aperture, graded-index fiber. Retrieved May 1, 2014, from http://www.rp-photonics.com/passive_fiber_optics4.html
Single mode optical fiber. (2014, April 22). Wikipedia
. Retrieved May 2, 2014, from https://en.wikipedia.org/wiki/Single_mode_optical_fiber
40Slide41
References
Steenbergen, R. (Director) (2013, February 4). Everything You Always Wanted to Know About Optical Networking - But Were Afraid to Ask. NANOG57. Lecture conducted from GTT, Orlando, Florida
.Technologies. (n.d.). . . Retrieved May 1, 2014, from http://www.pacer.co.uk/Assets/Pacer/User/Photodiode%20Typical%20Applications.pdfTotal internal reflection. (2014, April 28). Wikipedia. Retrieved May 2, 2014, from https://en.wikipedia.org/wiki/Total_internal_reflection
Zeghbroeck., B. V. (2011, January 1). Chapter 4: p-n Junctions. Optoelectronic devices. Retrieved May 1, 2014, from http://ecee.colorado.edu/~bart/book/book/chapter4/ch4_6.htm
http://en.wikipedia.org/wiki/Vertical-cavity_surface-emitting_laser
http://en.wikipedia.org/wiki/Laser_diode
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Key Points
Single Mode fibers are used in long data transmission. Multimode Fibers are cheaper and are used for short distancesLight signal intensity is measured in dBmWPIN PDs create one electron-hole pair per entering photon.VCSELs allow for minimal power use and densely packed on chip integration
Monolithic VCSEL-PIN based transceivers allow for short-haul data transfer in the 10Gb/s range.42