optoelectronic integration
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05/05/14. Optoelectronic Integration. - PowerPoint PPT PresentationTRANSCRIPT
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Optoelectronic IntegrationBergur GudbergssonZach WhitneyMarcus HaleAs 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
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OutlineFiber Optics
– Basics of Fiber– Fiber types– Optical Power– Transmission Bands– Wave Division Mux
PIN Photodiode– Absorption– Energy Band Diagrams– Applications
VCSEL– Basic Operation– Structure– VCSEL-PIN TRx function & fabrication
Optical Interconnects– Basic operation
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The Basics of Fiber• A fiber cable consists of:
1. Core2. Cladding3. Buffer4. Jacket
• “Total Internal Reflection”
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Cladding has lower refractive index than the core which causes total internal reflection within the core
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Fiber Types• Two main types of fiber optics cables– Single Mode Fiber (SMF) (9μM)– Multi Mode Fiber (MMF) (62.5μM or 50μM)
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Single Mode Fiber• Small core carries single mode of light• No modal dispersion• Long-haul data transmission• Requires expensive coherent laser light source• Requires specific connector alignment• Operates in 1.3μM -1.5μM Region
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Multi Mode Fiber• Multiple modes of light can propagate• Modal dispersion limits distance (500 meters)• Uses cheaper light sources– LED– VCSEL
• Larger alignment tolerances• Typically operates at 0.85μM
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Optical Power• Light follows “inverse square law”– inversely proportional to distance squared– Attenuation = loss of intensity
• Measured in Decibel-milliWatts (dBm /dBmW)– 0dBm is 1 mW– 3dBm is 2 mW– -50dBm is 10 nW
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Transmission BandsSplit into four windows– 850nM• High attenuation
– 1310nM• Zero modal dispersion for SMF• Up to 10kM reach
– 1550nM (Conventional-band)• Amplified via erbium doped fibers
– 1570-1610nm (Long-band)
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Typical Mux/Demux System
• Multiple signals are generated• Multiplexer combines the lights into a signal carrier signal• Signal is transmitted• λν=c• Signal is re-separated• Signal 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)
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Absorption• Photons Absorbed in the intrinsic region• Creates Carriers• Increases Photocurrent (Light into Current)• Si: infrared(700nm) up to 1μm• InGaAS: up to 1.7μm (Longer wavelengths)
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Electron-Hole Pair Generation
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Energy band Diagram InGaAs
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Energy band Diagram PIN-Si
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Applications• Optical fiber communications
• Security Systems
• Cameras
• Light 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 Lasers• Different from typical Laser Diodes– Laser is perpendicular to the surface.
• P and N doped regions act as parallel DBR mirrors, also forming a diode junction.
• Multiple quantum wells• Able to arrange in dense 1 or 2D, on-chip
arrays.
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History of VCSELs– 1979 first device
using GaInAsP/InP– 1988 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 StructureTypical Laser Diode VCSEL
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VCSEL Array
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VCSEL technology
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VCSEL technology
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VCSEL-PIN TRx• Monolithic transceiver chips coupled with
MMF• Miniaturization only possible with PIN PD– Why?
• Data Rates in the 10-Gb/s range• Arrays allow Optical Interconnects even higher
rates
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VCSEL-PIN TRx Fabrication• Two stacks of MBE
layers• PIN PD grown in the
same run of the VCSEL layers.
• Order is important
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VCSEL-PIN TRx
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VCSEL-PIN TRx
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VCSELsPROS
• Easy testing throughout fabrication
• High reflectivity mirrors• Reduced threshold
current (down to the 10’s of uA)
• Low power consumption
CONS• 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 layers– SiO2 (dated)• High resistivity and insulation• Poor heat conductivity (1W/mK)
– AlN (new fabrication)• High resistivity• High heat conductivity (300W/mK)• Increased temp distribution, reduces thermal
resistance
– Carbon Nanotubes (future?)
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Correcting Thermal Issues in VCSELs
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Correcting Thermal Issues in VCSELs
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Final Thoughts on VCSELs
• VCSLEs experiencing huge growth as electrical interconnects slowly become obsolete
• VCSELs are attractive for short-haul, large data transfers
• Can densely back in 1D & 2D array allowing for increased output as well as easy packaging
• Great, and basically only choice for optical interconnects
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Brief Overview of Optical Interconnects
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Brief Overview of Optical Interconnects
• Advantages– Keep up with Moore’s Law– Higher carrier frequency– Less crosstalk– Lower power consumption– Data ranges in the range of Tb/s
• http://www.youtube.com/watch?v=0U4Af2qmgFA (similar but using silicon based lasers)
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Conclusion• All of these optoelectrical innovations
contribute to the growing field of optical interconnection technology
• Immensely complex, research still underway
• Huge growth potential
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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=6698467
• Introduction 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
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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/1303.3954
• Muramoto, 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
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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.pdf
• Total 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 distances
• Light signal intensity is measured in dBmW• PIN 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.