1. Optics and Photonics
Georgia Institute of Technology - Atlanta
School of Electrical and Computer Engineering

2. Optics and Photonics
 Core Faculty
 Ali Adibi
 John A. Buck
 Russ Callen
 Gee-Kung Chang  Affiliated members
 David S. Citrin
 Ian T. Ferguson  Christiana Honsberg Microsystems
 Thomas K. Gaylord  William Hunt BioEngineering
 Elias N. Glytsis  Mary Ann Ingram Telecommunications
 Bernard Kippelen  Glenn Smith Electromagnetics
 Stephen E. Ralph  Ajeet Rohatgi Microsystems
 William T. Rhodes  Steve McLaughlin Telecom
 Gisele Bennett  Douglas Yoder Microsystems GTRIP
 Ben Klein

3. Primary Research Areas
 Optical Communication Networks
 Next generation optical networks
 Optical networking testbeds
 Advanced modulation formats
 Optical and electronic mitigation of signal impairment
 Coherent and interferometric detection
 Equalization and coding with telecommunications faculty
 Nonlinear Optics
 Propagation in optical fibers and nonlinear effects in
semiconductors
 Wavelength conversion methods
 Propagation of ultrashort solitons,
 Nonlinear propagation in fiber amplifiers
 Continuum generation in microstructure fiber.
 Short pulse characterization techniques which reveal both the
amplitude and phase

4. Primary Research Areas
 Photonics and optoelectronics
 Integrated sensors
 Fundamental investigations of new materials and nanostructures
 High speed optical transmitters, receivers
 Lithium niobate modulators with integrated drivers and detection
 Photonic bandgap devices: optical interconnects, signal processing,
and computing.
 Photonic crystals with 1-D, 2-D, and 3-D bandgap structures, for
passive and active optical devices
 Diffractive and holographic optics
 Volume holograms for data storage (memory), 3D pattern recognition,
filtering, WDM, interconnection, and sensing
 Diffractive/holographic optical elements, perform functions that would
be very difficult or impossible to produce using conventional optics.
 Driven by fundamental improvements in modeling, design, and
optimization methods as well as advances in microfabrication
technology

5. Georgia Tech Lorraine
 Quantum optical signal transmission
 Photon counting for long distance transmissions with very weak
optical beams (1 photon/bit)
 Non-linear dynamics for generating random codes for spread-
spectrum communications and multiple access networks
 Soliton modulation, wavelength division multiplexing
 Signal coding for wireless communications
 Efficient conversion of 2- and 3-D full-spectral image information
 Secure communications by means of quantum optics and chaotic
generation of random encryption keys

6. Advanced Methods for Terahertz
Science and Engineering
TERAHERTZ TECHNOLOGY
With Doug Denison, Mike Knotts, John Schultz, Don Creyts, Electromagnetic Spectrum
David Citrin, Stephen Ralph 100 GHz 10 THz
OBJECTIVES RF and Microwave IR, Optical, X-ray
• Expand recognized RF and optical capabilities to
Science TERAHERTZ Engineering
cover Terahertz frequency region
• Support current research programs in metamaterials Carrier
and EM composites characterization dynamics
• Provide advanced THz measurement resource for
Georgia Tech community Imaging
• Increase RI collaborations, publications and
innovations to attract new sponsored research
RESEARCH DESCRIPTION IMPACT OF WORK
Terahertz Science:
• Development of efficient sources and detectors
• Understanding of THz/material interactions • Supports GTRI strategic plan for growth into new
• Integration of semiconductor simulations with full EM technology areas
field numerical routines • Promotes active area of scientific research that
bridges high frequency electronics and optics
Terahertz Engineering:
• Secures new funding in biomedical research,
• Spectroscopy of large organic molecules and nanotechnology, industrial process monitoring, and
composites defense and national security applications
• Imaging for biomedicine and national security

7. Ultrafast Nano-Optics Theory and Simulation
David S. Citrin
School Of Electrical and Computer Engineering
Georgia Institute of Technology
Atlanta, Georgia 30332-0250

8. Terahertz technology window and opportunities
 Medical imaging
 Biochemical sensing
 Security
 Satellite-to-satellite
communications
 Process monitoring
 Direct modulation

9. Terahertz Nonlinearities in Semiconductor Optical
Amplifiers (SOA)
Time dependent carrier
temperature in GaAs SOA
follows THz frequency

10. Magneto-Optical Sensors:
Semiconductor Nanorings
InAs nanorings: Petroff group: UCSB

11. Localized Correlators for Mode Separation in
Multimode Fibers
Ali Adibi
School of Electrical and Computer Eng.
Georgia Institute of Technology

12. Applications of Two-Center Recording
• Gated holographic recording ⇒ Localized recording
 Data storage
 Optical elements
Conventional optical elements
Diffractive optical elements
 Optical correlator
Pattern recognition
Mode separation (MM fibers)

13. Localized Holographic Correlators
Reference
Sensitizing
Detector Array
Recording Correlation
 Different patterns are recorded in different slices
 Diffracted intensity is proportional to the correlation
between the reading pattern with the recorded one

15. Research Areas
Fundamental physical processes Applications
 charge generation  Organic displays
 charge transport  Photovoltaic cells
 electroluminescence  RFID tags and sensors
 optical amplification  Organic field-effect
transistors
 lasers
 Organic memories
 photorefractivity
 Real-time holography
 nonlinear-optics
 Electro-active lenses
 liquid crystal mesophases
 Imaging

16. Organic Photovoltaics
 Bottom-up approach to photovoltaic cells on light weight flexible
substrates
 Develop new organic semiconductors with high mobility
 Use self-assembly to produce highly ordered thin films

17. Organic Electronics
Low temperature processing
of organic semiconductors,
metals and dielectrics on
flexible substrates: low cost
($0.01)
 Macroelectronics
 RF identification tags
Metal deposition on plastics  Electronic paper
from solution, micro-size
features using soft lithography  Active matrix drivers

18. Organic Displays
 RGB active high luminance at
low voltage, processing at low
temperature on flexible substrates
 Developed photo-patternable hole transport
polymers that can be processed like a photoresist;
provides easy patterning for color displays.
Chem. Mater. 15, 1491 (2003)

19. Holography and Imaging
Thick phase recording media for real-time
holography, large dynamic range and
video rate compatible response times
 Holographic storage
 Optical correlators
 Dynamic holograms
 Image processing
 Medical Imaging
 Optical testing
 Novelty filtering
 Phase-conjugation

20. Nonlinear Optics & Photonics
 Organic electro-optic
materials and devices
 Frequency conversion
 Tunable filters and
routers
 Tunable optical delay
lines
 Amplifiers and lasers
 Short pulse
diagnostics
 Integrated waveguide
and microring resonator
devices

21. Optical Networking Group Goals
• Establish Optical Networking Research Laboratory
• Next Generation optical network architecture and applications
• Design and Build Next Generation Optical Internet Testbed
• Enabling Photonic System Technology Research
• Advanced transmitters, receivers, modulation techniques
• All-optical wavelength, space, and time switches
• Tunable optical delay, optical label, and burst mode payload receivers
• Compensation techniques for fiber transmission impairments
• Control and Management of Optical Routing Network
• Broadband access technology for bandwidth-on-demand, low-latency
symmetric customer services.
• OLS and GMPLS control plane and management interface
• Routing protocol and contention resolution algorithms
• Enhanced Intelligent Networking Services and Operations
• Agile dynamic service creation, provisioning, and protection/restoration
• Flexible burst switching service with flexible bandwidth granularity
• Build a National Research Testbed Consortium
• Lead communications research institutions
• Enhance and build upon National Light (Lambda) Rails

22. Broadband Optical Networking
ONU
ONU
Testbed Research in Georgia Tech
ONU
Access Network
Splitter/
Combiner
Core Network
Node
RWA OLSR RWA
OLT
WDM WDM
IP/MPLS
IP/MPLS
ADM ports
RWA ADM ports
Edge Network WDM Edge Network
Node
RWA Node
IP/MPLS WDM RWA
IP/MPLS
WDM ONU
ADM ports
ADM ports
Optical Router
ONU
Architecture
Backplane
OLT
-X
S
bE
PO
C
O
G
Splitter/
M&CN
Optical label Combiner
Nλ ’s Extraction Client Interface Processor Wavelength
per Fiber Interchange
OLSR: Optical Label Access Network ONU
Incoming Outgoing
Optical
Traffic OLS
Switching Fabric
Optical
Traffic Switching Router
ONU
Forwading Engine RWA: Routing and
Routing Engine Switching Assignment
Georgia Tech Confidential

23. Building Optical Networking Testbed in GCATT

24. Promoting Optical Networking
for Next Generation Internet
BellSouth Network Service President and CTO

25. Fully Integrated Chem/Bio Sensing
Multimode Interferometer/CMOS detection and signal analysis
 Development of interferometric chemical and biological “wet” and gas sensors
integrated directly with on-chip electronics for intelligent sensors
 The key to this research is the design and fabrication of biological and chemical
interferometric sensors integrated in three dimensions (3D) directly on top of Si
CMOS VLSI detector and signal processing circuitry
 The challenge for this integrated system is to demonstrate high sensitivity detection
in a miniaturized, short Si CMOS on-chip size, and species discrimination in a
rugged, low power, portable format
Silicon PiN diode array for modal image analysis
Sigma-Delta “analog to digital” converters
Heterogeneous integrated laser sources

26. Interferometer Structure
Reference
Sensing
Sensing Layer:
 Detects organics, i.e. benzene,
trichloroethylene
 Compatible with electronics
fabrication and processing
 Chemically resistant
 Reusable (reversible sorption or
organics)
Novolac ~1 µm, n ~1.60 Si3N4 ~0.2 µm,
 Effective up to 250 °C n ~ 1.9218, k ~ 0
 Index of refraction = 1.59 – 1.61
(l = 850 nm) SiO2 cladding ~2 µm, n ~ 1.4734, k ~ 0
 Available dissolved in solvent for
spin coating Silicon Substrate, n ~ 3.6538, k ~ 0.004177

27. A Platform Technology for the Integration of
Semiconductor Electronic Devices with Nonlinear
Optical Materials
Stephen E. Ralph W. Alan Doolittle
stephen.ralph@ece.gatech.edu alan.doolittle@ece.gatech.edu
404 894 5168 404 894 9884
Georgia Institute of Technology
School of Electrical and Computer Engineering
777 Atlantic Drive
Atlanta GA 30332

28. Dense Epitaxial Integrated Optics
Signal processing circuits
Electrodes Epitaxial III-Nitride
Epitaxial AlN buffer
Ti diffused/strip loaded
waveguides LiNbO3
 Georgia Tech has developed a materials growth technology which allows the epitaxial integration of AlGaN
semiconductors with the most widely used nonlinear-electro optical material, Lithium Niobate
 This technology enables:
 Integrated control of phase and amplitude of optical signals
 Advanced modulation formats exploiting phase, commonly seen in wireless
 Interferometric transmitters and receivers
 Integrated detection at 1500nm via use of InN detectors
 Monitoring of Extinction ratio
 Dynamically adaptable bias point control
 Dynamic Chirp control
 Pulse shaping

29. Source
Progress in Device Processing
Gate Drain
Process Protection
Process Protection SiNX Waveguide Electrodes
Modulation doped cap
Modulation doped AlGaN cap
Undoped GaN
Undoped GaN
“Special”AlN
“Special” AlN
Z-cut LiNbO3 Ti-diffused wafers
Z-cut LiNbO3 Ti-diffused wafers
Waveguides •Students have been trained and have
successfully completed 7 out of 16
process steps.
Source •Aggressive small geometry lithography
and metallization (1-4 um) successfully
demonstrated.
Gate Drain
Source
Drain
•New students began training and clean room
qualification (~3 month process) in fall 2003.
Mesa
•Effort leveraged by engineer supported
outside of GTBI program.

30. Soliton Generation via Intrapulse
Stimulated Raman Scattering in Photonic
Crystal Fibers:
Experimental and Numerical
Investigations
B.R. Washburn, S.E. Ralph
School of Electrical and Computer Engineering
Georgia Institute of Technology
P. A. Lacourt, J. M. Dudley, W. T. Rhodes
GTL-CNRS Telecom, Georgia Tech Lorraine
S. Coen
Service d’Optique et Acoustique, Université Libre de Bruxelles
R.S. Windeler
Bell Laboratories, Lucent Technologies

31. Geometry of the Photonic Crystal Fiber
• PCF comprised of a hexagonal lattice
of air-holes and glass
• The “core” is a defect in the lattice:
glass where a hole should be
• PCF exhibits a reduced fiber core size
compared to standard fiber
• The effective nonlinearity (γ=0.07(W
m)−1 ) is eight times larger than in
2020ncrωγ≡π
standard fiber at 800 nm
• Specific geometry exhibits zero group
velocity dispersion at 767 nm

32. Supercontinuum Generation in PCF
100
10-1
10-2
10-3
Supercontinuum
Generation
Spectral Intensity (a.u.)
10-4
Input Ti:sapphire
10-5
spectrum
600 700 800 900 1000 1100 1200 1300 1400
Wavelength (nm)
 Dramatic spectral broadening due to multiple nonlinear effects
(SPM, FWM, SRS) occurring simultaneously
 Dominant mechanism depends on peak power, pulse width and
dispersion and fiber length
 Spectral width of 1000 nm, which covers all visible wavelengths

33. Cooperative Signal Processing for Equalization
Stephen E. Ralph and Steve Mclaughlin
School of Electrical and Computer Engineering

34. Fabricated Device
V cc
 Two-segment metal-semiconductor-
metal (MSM) device fabricated
 InGaAs and GaAs demonstrated -Vcc Vo
 Ease of manufacture
 50-µm inner detector radius
Vcc
 Scalar weighting is implemented by Vcc
applying dual-biasing Separate
Optical Detection Regions
 “Polarity” of detected signal is related Fiber
to polarity of bias voltage Vo
 Maintains the simplicity of a
conventional photodetector
-Vcc

35. Channel Impulse Response
Simulation Measurement
λ = 1550 nm λ = 1550 nm
λ = 810 nm λ = 810 nm
 Measured with ~1-ps @ 1550-nm or ~20-ps @ 810-nm
 Assume incoherent interaction among modes are output
 Fiber: 1.1-km silica MMF with 50-µm graded-index core
 Simulation parameter of fiber based on manufacture specs

36. Simulated Eye-Diagram over 1.1-km MMF
600-Mbps @ 810-nm 1250-Mbps @ 1550-nm
Emulate MMF link
by using
measured MMF
impulse response
with conventional
PD
600-Mbps @ 810-nm 1250-Mbps @ 1550-nm
Emulate MMF link
by using measured
MMF impulse
response with SRE
enhancement
200 MHz-km @ 810-nm 500 MHz-km @ 1550-nm

37. Measured 1.25-Gbps Link
 Link with 1.1 km, 50-µm, GI-MMF
 PRBS at 1.25-Gb/s
 Externally modulated 1550-nm FP
laser source with mode-scrambler
 Overfilled-launch into fiber
 Dramatic reduction in ISI with SRE
 Improvement in amplitude and phase margin
 Complete closure of eye otherwise
 Works synergistically with restricted
illumination condition

38. Measured Bit-Error-Rate
* includes penalty
associated with non-
optimized performance
inherent to receiver (PD
responsivity, TIA noise,
PD-TIA response)
 For 1.1-km link, >10-9 BER at 1.25 Gbps is achievable with SRE
 With standard detection, ISI renders link unusable
 Despite SRE loss, sensitivity required for 1000-LX Ethernet is achievable
 Back-to-back; accounting for penalty due to non-optimal device fabrication

39. 1.1km MMF Link Performance @ 1.25 Gbps
 Combined techniques
“SRE+DFE” and “SRE +
Viterbi” shows unique
capabilities of an
integrated
Photonic/Electrical
Approach pioneered at
Georgia Tech
 Near total compensation
of DMD is possible
DFE = 5 forward taps, 5 backward taps Viterbi = 16 states, 20 bits decoder depth